Posts by Jai Ganesh

Jai Ganesh · This is Cool

2521) Odometer

Gist

An odometer is an instrument on a vehicle's dashboard that measures and displays the total distance traveled, typically in miles or kilometers. It works via mechanical gears or electronic sensors (on modern cars) tracking wheel rotations to determine distance, crucial for maintenance tracking and resale value.

Odometer includes the root from the Greek word hodos, meaning "road" or "trip". An odometer shares space on your dashboard with a speedometer, a tachometer, and maybe a "tripmeter". The odometer is what crooked car salesmen tamper with when they want to reduce the mileage a car registers as having traveled.

Summary

An odometer is a device that registers the distance traveled by a vehicle. Modern digital odometers use a computer chip to track mileage. They make use of a magnetic or optical sensor that tracks pulses of a wheel that connects to a vehicle’s tires. This data is stored in the engine control module (ECM). Odometers use these stored values to determine the total distance traveled by a vehicle.

Analog or mechanical odometers consist of a train of gears (with a gear ratio of 1,000:1) that causes a drum, classified in tenths of a mile or kilometre, to make one turn per mile or kilometre. A series of usually six such drums is arranged in such a way that one of the numerals on each drum is visible in a rectangular window. The drums are coupled so that 10 revolutions of the first cause one revolution of the second, and so forth, with the numbers appearing in the window representing the vehicle’s accumulated mileage.

The Roman architect and engineer Vitruvius is credited with inventing the initial version of an odometer in 15 bce. The concept consisted of a chariot wheel that turned 400 times to show one Roman mile. This wheel was mounted in a frame with a 400-tooth cogwheel. For every 400 rotations of the chariot wheel, the cogwheel would drop one pebble. In 1642 the French mathematician Blaise Pascal used the same principle to create an apparatus that used gears and wheels. For every 10 rotations of a gear, a second gear advanced one place. The modern odometer was invented about 1847 by pioneers William Clayton and Orson Pratt, members of the Church of Jesus Christ of Latter-day Saints. They attached their apparatus to a wagon wheel while they traversed the plains from Nebraska to the Great Salt Lake valley.

Details

An automobile’s most prominent yet unexplored part is the odometer. It is placed behind the steering wheel on the dashboard. It displays the distance the car has run. Odometer readings are beneficial to car owners when selling the vehicle. It helps evaluate the mileage or plans for car service.

Odometers can be mechanical, electrical, or a combination of the two. They are also known as mileometer or milometers in countries with imperial units or US customary units. Odometer is the most widely used name, especially in the UK and the Commonwealth countries.

Meaning

An odometer is a device used to measure the displacement of an object. It measures the distance travelled between the start point and the endpoint. Odometer is derived from two Greek words that mean path and measure.

Who invented the odometer?

Vitruvius, a Roman architect and engineer, is credited for the invention of the odometer in the 15th century. He used a standard chariot wheel, mounted on a frame with a 400-teeth cogwheel, and turned it 400 times in a Roman mile. The cogwheel employed a gear that slipped a stone into the box for every mile. Thus, it helped learn the miles covered by counting the pebbles.

In the 16th century, Blaise Pascal invented a calculating machine called Pascaline. It was a prototype of an odometer—the Pascaline comprised gears and wheels, where each gear had ten teeth. Every time a tooth completed a revolution, the second gear was engaged. This principle is used in the mechanical odometer.

English military engineer Thomas Savery invented an odometer for ships. In 1775, Ben Franklin, a statesman and a writer, created a simple odometer that measured the mileage of the routes. He attached it to his carriage.

In 1847, the Mormon Pioneers invented an odometer while crossing the plains from Missouri to Utah. Also known as a roadometer, they attached it to the wagon’s wheel, and when the wagon started the journey, it counted the wheel revolutions. Orson Pratt and William Clayton designed the odometer, and Appleton Milo Harmon, the carpenter, built it.

In 1854, Nova Scotia’s Samuel McKeen designed another early version of the odometer. The device measured driven mileage. He attached the device to the carriage side and measured the miles with wheels turning.

Types of odometer:

There are two types of odometers.

1) Mechanical odometers

2) Electronic odometers

Mechanical odometers

Mechanical odometers start with the transmission. The transmission system contains a small gear that measures the odometer advancing. This small gear is connected to the speedometer drive cable. The other end of this cable is connected to the instrument cluster.

The internal transmission gear turns when the engine is turned on, and the car starts moving. This internal transmission gear motion is conveyed to another set of gears linked to changeable digits by the connected drive cable. Thus, the counting begins from the right side of the group of numbers.

The process continues till the distance travelled by automobile compels the left side digits to roll over. This counting process repeats until all the adjacent numbers touch their apex values. Then, all the digits are set back to zero, and it starts again.

Mechanical odometers are not always precise and a hundred per cent accurate.

Electronic odometers

After the mechanical odometers came the electronic ones. They are also known as digital odometers. They depend on the automobile’s electronics for establishing accurate mileage.

Electronic odometers, like mechanical ones, employ a special gear for changing the count seen on the dashboard. In addition, a magnetic sensor replaces the drive cable to track the gear turns in the transmission. The wires conduct the obtained signal to the car’s onboard computer that interprets and converts the data into mileage count.

The advantage of electronic odometers over mechanical ones is that they provide better accuracy. In addition, no one can manipulate electronic odometers easily, hence giving an accurate count of the vehicle’s mileage.

Odometers come with an additional trip meter called a trip odometer. It helps the car owners determine the mileage for any particular distance without interfering with the primary odometer reading.

Conclusion

The primary purpose of an odometer is to measure the distance travelled by the vehicle. In addition, odometer readings help determine various maintenance milestones such as tyre rotations, oil changes etc. Dealers use odometer readings to estimate the vehicle’s valuation in the used car market. Resetting odometer values require changing the entire transmission system of a car. Hence, odometer readings are very difficult to reset. Also, tampering with the reading is considered a fraud and punishable by law.

Additional Information

Mechanical odometers have been counting the miles for centuries. Although they are a dying breed, they are incredibly cool because they are so simple! A mechanical odometer is nothing more than a gear train with an incredible gear ratio.

The odometer we took apart for this article has a 1690:1 gear reduction! That means the input shaft of this odometer has to spin 1,690 times before the odometer will register 1 mile.

Odometers like this are being replaced by digital odometers that provide more features and cost less, but they aren't nearly as cool. In this article, we'll take a look inside a mechanical odometer, and then we'll talk about how digital odometers work.

Mechanical Odometers

Mechanical odometers are turned by a flexible cable made from a tightly wound spring. The cable usually spins inside a protective metal tube with a rubber housing. On a bicycle, a little wheel rolling against the bike wheel turns the cable, and the gear ratio on the odometer has to be calibrated to the size of this small wheel. On a car, a gear engages the output shaft of the transmission, turning the cable.

The cable snakes its way up to the instrument panel, where it is connected to the input shaft of the odometer.

The Gearing

This odometer uses a series of three worm gears to achieve its 1690:1 gear reduction. The input shaft drives the first worm, which drives a gear. Each full revolution of the worm only turns the gear one tooth. That gear turns another worm, which turns another gear, which turns the last worm and finally the last gear, which is hooked up to the tenth-of-a-mile indicator.

Each indicator has a row of pegs sticking out of one side, and a single set of two pegs on the other side. When the set of two pegs comes around to the white plastic gears, one of the teeth falls in between the pegs and turns with the indicator until the pegs pass. This gear also engages one of the pegs on the next bigger indicator, turning it a tenth of a revolution.

On the white wheel between the "3" and the "4," there are two pegs. One time per revolution, one of the gear teeth on the white gear falls in between these two pegs, causing the black gear next to it to move one-tenth of a revolution.
You can now see why, when your odometer "rolls over" a large number of digits (say from 19,999 to 20,000 miles), the "2" at the far left side of the display may not line up perfectly with the rest of the digits. A tiny amount of gear lash in the white helper gears prevents perfect alignment of all the digits. Usually, the display will have to get to 21,000 miles before the digits line up well again.

You can also see that mechanical odometers like this one are rewindable. In many older vehicles, driving in reverse could cause the mechanical odometer to run backward due to the straightforward gear mechanism. However, some mechanical odometers were equipped with mechanisms to prevent reverse counting, ensuring the mileage only increased regardless of the driving direction.

In the movie "Ferris Bueller's Day Off," in the scene where they have the car up on blocks with the wheels spinning in reverse -- that should've worked! In real life, the odometer would've turned back. Another trick is to hook the odometer's cable up to a drill and run it backwards to rewind the miles.

Computerized Odometers

If you make a trip to the bike shop, you most likely won't find any cable-driven odometers or speedometers. Instead, you will find bicycle computers. Bicycles with computers like these have a magnet attached to one of the wheels and a pickup attached to the frame. Once per revolution of the wheel, the magnet passes by the pickup, generating a voltage in the pickup. The computer counts these voltage spikes, or pulses, and uses them to calculate the distance traveled.

If you have ever installed one of these bike computers, you know that you have to program them with the circumference of the wheel. The circumference is the distance traveled when the wheel makes one full revolution. Each time the computer senses a pulse, it adds another wheel circumference to the total distance and updates the digital display.

Many modern cars use a system like this, too. Instead of a magnetic pickup on a wheel, they use a toothed wheel mounted to the output of the transmission and a magnetic sensor that counts the pulses as each tooth of the wheel goes by. Some cars use a slotted wheel and an optical pickup, like a computer mouse does. Just like on the bicycle, the computer in the car knows how much distance the car travels with each pulse, and uses this to update the odometer reading.

One of the most interesting things about car odometers is how the information is transmitted to the dashboard. Instead of a spinning cable transmitting the distance signal, the distance (along with a lot of other data) is transmitted over a single wire communications bus from the engine control unit (ECU) to the dashboard. The car is like a local area network with many different devices connected to it. Here are some of the devices that may be connected to the computer network in a car:

* Engine control unit (ECU)
* Climate control system
* Dashboard
* Power window controls
* Radio
* Anti-lock braking system
* Air bag control module
* Body control module (operates the interior lights, etc.)
* Transmission control module

Many vehicles use a standardized communication protocol, called SAE J1850, to enable all of the different electronics modules to communicate with each other.

The engine control unit counts all of the pulses and keeps track of the overall distance traveled by the car. This means that if someone tries to "roll back" the odometer, the value stored in the ECU will disagree. This value can be read using a diagnostic computer, which all car-dealership service departments have.

Several times per second, the ECU sends out a packet of information consisting of a header and the data. The header is just a number that identifies the packet as a distance reading, and the data is a number corresponding to the distance traveled. The instrument panel contains another computer that knows to look for this particular packet, and whenever it sees one it updates the odometer with the new value. In cars with digital odometers, the dashboard simply displays the new value. Cars with analog odometers have a small stepper motor that turns the dials on the odometer.

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Jai Ganesh · Dark Discussions at Cafe Infinity

2458) Felix Bloch

Gist:

Life

Felix Bloch was born in Zurich, Switzerland, the son of a merchant, and studied at ETH and elsewhere. When the Nazis took power in 1933, he left Europe to work at Stanford University. After becoming an American citizen, he worked on atomic energy in Los Alamos during World War II and later on radar at Harvard University. Immediately after the war, he did his Nobel Prize-awarded work at Stanford. He became the first head of CERN outside Geneva in 1954-1955. Bloch was married and had four children.

Work

Protons and neutrons in nuclei act like small, rotating magnets. Atoms and molecules therefore align in a magnetic field. Radio waves can disturb their direction of rotation, but only in certain stages, in accordance with quantum mechanics. When the atoms return to their original positions, they emit electromagnetic radio waves with frequencies characteristic of different elements and isotopes. In 1946, Felix Bloch and Edward Purcell developed methods for precise measurement, making it possible to study different materials’ compositions.

Summary

Felix Bloch (born Oct. 23, 1905, Zürich, Switz.—died Sept. 10, 1983, Zürich) was a Swiss-born American physicist who shared (with E.M. Purcell) the Nobel Prize for Physics in 1952 for developing the nuclear magnetic resonance method of measuring the magnetic field of atomic nuclei.

Bloch’s doctoral dissertation (University of Leipzig, 1928) promulgated a quantum theory of solids that provided the basis for understanding electrical conduction. Bloch taught at the University of Leipzig until 1933; when Adolf Hitler came to power he emigrated to the United States and was naturalized in 1939. After joining the faculty of Stanford University, Palo Alto, Calif., in 1934, he proposed a method for splitting a beam of neutrons into two components that corresponded to the two possible orientations of a neutron in a magnetic field. In 1939, using this method, he and Luis Alvarez (winner of the Nobel Prize for Physics in 1968) measured the magnetic moment of the neutron (a property of its magnetic field). Bloch worked on atomic energy at Los Alamos, N.M., and radar countermeasures at Harvard University during World War II.

Bloch returned to Stanford in 1945 to develop, with physicists W.W. Hansen and M.E. Packard, the principle of nuclear magnetic resonance, which helped establish the relationship between nuclear magnetic fields and the crystalline and magnetic properties of various materials. It later became useful in determining the composition and structure of molecules. Nuclear magnetic resonance techniques have become increasingly important in diagnostic medicine.

Bloch was the first director general of the European Organization for Nuclear Research (1954–55; CERN).

Details

Felix Bloch (23 October 1905 – 10 September 1983) was a Swiss-American theoretical physicist who shared the 1952 Nobel Prize in Physics with Edward Mills Purcell "for their development of new methods for nuclear magnetic precision measurements and discoveries in connection therewith".

He was the first Stanford University Nobel laureate.

Bloch made fundamental theoretical contributions to the understanding of ferromagnetism and electron behavior in crystal lattices. He is also considered one of the developers of nuclear magnetic resonance.

Education

Bloch was born on 23 October 1905 in Zurich, Switzerland, to Jewish parents, Gustav Bloch and Agnes Mayer. Gustav was financially unable to attend university and worked as a wholesale grain dealer in Zurich. Gustav moved to Zurich from Moravia in 1890 to become a Swiss citizen. Their first child was a girl born in 1902, while Felix was born three years later.

Bloch entered public elementary school at the age of six and is said to have been teased, in part because he "spoke Swiss German with a somewhat different accent than most members of the class". He received support from his older sister during much of this time, but she died at the age of 12, devastating Felix, who is said to have lived a "depressed and isolated life" in the following years. Bloch learned to play the piano by the age of 8 and was drawn to arithmetic for its "clarity and beauty". Bloch graduated from elementary school at twelve and enrolled in the Cantonal Gymnasium in Zurich for secondary school in 1918. He was placed on a six-year curriculum here to prepare him for university. He continued his curriculum through 1924, even through his study of engineering and physics in other schools, though it was limited to mathematics and languages after the first three years.

After these first three years at the Gymnasium, at the age of 15, Bloch began to study at the ETH Zurich. Although he initially studied engineering, he soon changed to physics. During this time, he attended lectures and seminars given by Peter Debye and Hermann Weyl at the ETH Zurich and Erwin Schrödinger at the neighboring University of Zurich. A fellow student in these seminars was John von Neumann.

Bloch graduated in 1927, and was encouraged by Debye to go to the University of Leipzig to study under Werner Heisenberg. Bloch became Heisenberg's first graduate student, and gained his doctorate in 1928. His doctoral thesis established the quantum theory of solids, using waves to describe electrons in periodic lattices.

Career and research

Bloch remained in European academia, working on superconductivity with Wolfgang Pauli in Zurich; with Hans Kramers and Adriaan Fokker in the Netherlands; with Heisenberg on ferromagnetism, where he developed a description of boundaries between magnetic domains, now known as Bloch walls, and theoretically proposed a concept of spin waves, excitations of magnetic structure; with Niels Bohr in Copenhagen, where he worked on a theoretical description of the stopping of charged particles traveling through matter; and with Enrico Fermi in Rome.

In 1932, Bloch returned to Leipzig to assume a position as Privatdozent (lecturer). In 1933, immediately after Adolf Hitler came to power, Bloch left Germany out of fear of anti-Jewish persecution, returning to Zurich before traveling to Paris to lecture at the Institut Henri Poincaré.

In 1934, the chairman of Stanford Physics invited Bloch to join the faculty. Bloch accepted the offer and emigrated to the United States. In the fall of 1938, Bloch began working with the 37 inch cyclotron at the University of California, Berkeley, to determine the magnetic moment of the neutron. Bloch went on to become the first professor of theoretical physics at Stanford. In 1939, he became a naturalized citizen of the United States.

During World War II, Bloch briefly worked on the atomic bomb project at Los Alamos. Disliking the military atmosphere of the laboratory and uninterested in the theoretical work there, Bloch left to join the radar project at Harvard University.

After the war, he concentrated on investigations into nuclear induction and nuclear magnetic resonance, which are the underlying principles of MRI. In 1946, he proposed the Bloch equations, which determine the time evolution of nuclear magnetization. He was elected to the National Academy of Sciences in 1948. Along with Edward Purcell, Bloch was awarded the Nobel Prize in Physics in 1952 for his work on nuclear magnetic induction.

When CERN was being set up in the early 1950s, its founders were searching for someone of stature and international prestige to head the fledgling international laboratory, and in 1954 Professor Bloch became CERN's first director-general, at the time when construction was getting under way on the present Meyrin site and plans for the first machines were being drawn up. After leaving CERN, he returned to Stanford University, where he in 1961 was made Max Stein Professor of Physics.

In 1964, he was elected a foreign member of the Royal Netherlands Academy of Arts and Sciences. He was also a member of the American Academy of Arts and Sciences and the American Philosophical Society.

Family

On 14 March 1940, Bloch married Lore Clara Misch (1911–1996), a fellow physicist working on X-ray crystallography, whom he had met at an American Physical Society meeting. They had four children, twins George Jacob Bloch and Daniel Arthur Bloch (born 15 January 1941), son Frank Samuel Bloch (born 16 January 1945), and daughter Ruth Hedy Bloch (born 15 September 1949).

Bloch died on 10 September 1983 in Zurich at the age of 77. In 2025 Bloch's family donated his Nobel Prize medal to CERN.

Jai Ganesh · Jokes

Q: What did the bird say to the racing squirrel?
A: You walnut beat that!
* * *
Q: How many squirrels does it take to change a light bulb?
A: Actually, none because squirrels only change bulbs that are NUT broken.
* * *
Q: Why does it take more than one squirrel to screw in a lightbulb?
A: Because they're so darn stupid!
* * *
Q: Why was the squirrel late for work?
A: Traffic was NUTS.
* * *
Q: How do you catch a carpenter squirrel (definition: a squirrel that likes power tools)?
A: Go to Home Depot and pretend to be nut-wood.
* * *

Jai Ganesh · Dark Discussions at Cafe Infinity

Comedy Quotes - II

1. We participate in a tragedy; at a comedy we only look. - Aldous Huxley

2. Friends applaud, the comedy is over. - Ludwig van Beethoven

3. I am completely open to doing a romantic comedy, but I will never do something just for the sake of doing a specific genre or because it's the time or place to do a different type of movie. I think that would be a huge mistake. - Leonardo DiCaprio

4. I will do comedy until the day I die: inappropriate comedy, funny comedy, gender-bending, twisting comedy, whatever comedy is out there. - Sandra Bullock

5. Even actresses that you really admire, like Reese Witherspoon, you think, 'Another romantic comedy?' You see her in something like 'Walk the Line' and think, 'God, you're so great!' And then you think, 'Why is she doing these stupid romantic comedies?' But of course, it's for money and status. - Gwyneth Paltrow

6. When I tried to branch out into comedy, I didn't do very well at it, so I went back to doing what I do naturally well, or what the audience expects from me - action pictures. - Sylvester Stallone

7. As for doing more dramatic work over comedy, I do whatever turns me on at the moment. - Sandra Bullock

8. I think that you can fall into bad habits with comedy... It's a tightrope to stay true to the character, true to the irony, and allow the irony to happen. - Ben Kingsley

Jai Ganesh · This is Cool

Field Vision Test

Gist

A visual field test (perimetry) maps your peripheral and central vision to detect blind spots (scotomas). It is essential for diagnosing and managing glaucoma, neurological conditions (e.g., MS, tumors, strokes), and monitoring medication side effects. Typically lasting 5–10 minutes per eye, patients click a button when they see light flashes while staring at a central point.

A visual field test can determine if you have blind spots, known as scotomas, in your vision and where they are. A blind spot's size and shape can show how eye disease or a brain disorder is affecting your vision.

Summary

A visual field test is an eye examination that can detect dysfunction in central and peripheral vision which may be caused by various medical conditions such as glaucoma, stroke, pituitary disease, brain tumours or other neurological deficits. Visual field testing can be performed clinically by keeping the subject's gaze fixed while presenting objects at various places within their visual field. Simple manual equipment can be used such as in the tangent screen test or the Amsler grid. When dedicated machinery is used it is called a perimeter.

The exam may be performed by a technician in one of several ways. The test may be performed by a technician directly, with the assistance of a machine, or completely by an automated machine. Machine-based tests aid diagnostics by allowing a detailed printout of the patient's visual field.

Details

A visual field test measures your peripheral vision, or how well you can see above, below and to the sides of something you’re looking at. It’s also called a perimetry test. Visual field testing is important for many conditions, including glaucoma.

Overview:

What is a visual field test?

A visual field test is a simple and painless test an eye care provider gives you to diagnose or monitor various eye conditions.

A visual field test measures two things:

* How far up, down, left and right your eye sees without moving (when you’re looking straight ahead).
* How sensitive your vision is in different parts of the visual field, which is the name for the entire area that you can see.

Your eyes normally see a wide area of the space in front of you. Without moving your eyes, you can see not only what’s straight ahead, but also some of what’s above, below and off to either side. Providers call all of the area you can see that isn’t right in front of you “peripheral vision.” This surrounds the area that’s right in front of you that you can see (central vision).

Vision is usually best right in the middle of the visual field, so you probably turn your eyes toward the things you want to see more clearly. The farther away from the center of your vision an object is, the less clearly you can see it. When an object moves far enough to the side, it disappears from your vision completely.

When is a visual field test performed?

When you visit an optometrist or ophthalmologist, a visual field test is part of a routine eye exam. Visual field testing can help your eye care provider find early signs of diseases like glaucoma that gradually damage vision. Some people with glaucoma don’t notice any problems with their vision, but the visual field test shows a loss of peripheral vision.

A visual field test can also help your provider find out more about the part of your nervous system that allows you to see. The visual part of your nervous system includes:

* Your retina, the part of your eye that’s like a translator that changes light energy into an electrical signal.
* Your optic nerve, the nerve that carries the signals to your brain so they can become images.
* Your brain, the place where the signals become the images you see.

Issues with any part of this system can change your visual field. There are well-known patterns in the test results that help providers recognize certain types of injury or disease.

By repeating visual field tests at regular intervals, providers also can tell whether your condition is getting better or worse.

Medical conditions that might cause a provider to order a visual field test

Your healthcare provider may want you to have a visual field test if you have (or they think you may have) certain conditions. Providers use the results to both diagnose and monitor conditions such as:

* Glaucoma.
* Stroke.
* Macular degeneration.
* Multiple sclerosis (MS).
* Graves’ disease.
* Pituitary gland disease.
* Blind spot (scotoma).

Why do some people need to have visual field tests many times?

Sometimes your eye care provider will want to repeat the visual field test right away to make sure the results are accurate. If you’re tired, for example, the test results can be unreliable.

Your provider might also recommend that you take a visual field test again in a few weeks, a few months or a year. This might be necessary to make sure that they find any new problems early. When you have certain eye conditions, your provider will do visual field tests regularly to find out how well the treatment is working.

Visual field tests are especially important in the treatment of glaucoma. These tests will tell the provider if you’re losing vision even before you notice. That’s just one of the reasons why people who have glaucoma should keep all of their appointments with their provider.

Test Details:

What happens during a visual field test?

You don’t have to prepare for a visual field test. It’s not invasive, so you aren’t likely to have any side effects.

There are several types of visual field tests, but they all have one thing in common: you look straight ahead at one point and signal when you see an object or a light somewhere off to the side.

Your provider will explain to you exactly where to look so that the test is accurate.

The two most basic types of visual field tests are very simple:

* Amsler grid: The Amsler grid is a pattern of straight lines that make perfect squares. You look at a large dot in the middle of the grid and describe any areas where the lines look blurry, wavy or broken. The Amsler grid is a quick test that only measures the middle of the visual field (your central vision) and provides your doctor with a small amount of information.
* Confrontation visual field: The term “confrontation” in this test just means that the person giving the test sits facing the person having the test, about 3 or 4 feet (around 1 meter) away. The provider holds their arms straight out to the sides. You look straight ahead, and the tester moves one hand and then the other inward toward you. You give a signal as soon as you see their hand.

The confrontation visual field test measures only the outer edge of the visual field. It’s not very exact.

Other types of visual field tests

You may hear about different types of or terms for visual field tests, including static and kinetic perimetry tests. (Perimetry test is another way of saying peripheral vision test.)

* Kinetic perimetry tests: A kinetic perimetry test is one in which the person giving the test moves an object around, and you tell them when you can see it. Providers often use the Goldmann perimetry test.
* Static perimetry tests: Automated peripheral vision tests are static perimetry tests. You look into a bowl-shaped machine and respond by pressing buttons when you see the object. Common types of static tests are the Humphrey and the Octopus.

How long does a visual field test take?

A test usually isn’t longer than about five to 10 minutes per eye.

What kind of visual field tests give more detailed information?

Computerized instruments are available to perform visual field tests and calculate results. These instruments give more reproducible and accurate results because:

* Your head is always in the same place during the test.
* The instrument has a large central “target” for you to look at, so the center of the visual field stays steady.
* The instrument uses tiny spots of light to test vision. The provider can change the brightness and color of the light to measure the sensitivity of vision at each location.
* There are clear standards for “normal” results. The instrument can compare each new test to these standards.

Results and Follow-Up:

What do the results of the visual field test mean?

A “normal” visual field test means that you can see about as well as people without vision issues.

The visual field test shows the amount of vision loss and the affected areas. The instrument prints the results as patterns of dots or numbers. The patterns tell your provider how well your eyes and visual field system work. This helps your provider diagnose an underlying health condition and what treatment you need.

A test that shows visual field loss means that vision in some areas isn’t as keen as it should be. A test could show that you have a small area of lost vision, or all vision lost in large areas.

When should I know the results of the test?

Generally, your provider should be able to give you results right away.

What are the next steps if the results are abnormal?

Abnormal results may mean different things. These results can indicate different types of issues, including glaucoma, macular degeneration or stroke. The follow-up will vary.

Your eye care provider will discuss treatment options with you.

When should I call my provider?

You should always contact your eye care provider if you have any new vision loss or eye discomfort. If you have sudden vision loss or eye pain, go to an emergency room for immediate medical help.

Additional Information

A visual field test is a diagnostic procedure that measures a person's entire field of vision, including peripheral (side) and central vision. It evaluates how well you can see in different areas of your vision and is commonly used to detect, diagnose, and monitor various eye and neurological conditions. The test plays a crucial role in identifying issues that may not be apparent during a routine eye exam, especially problems affecting peripheral vision.

Visual field testing can help uncover conditions such as glaucoma, retinal disorders, optic nerve damage, and neurological diseases like strokes or brain tumors. By mapping out the areas where vision is diminished or absent, it provides valuable insights into the health of your eyes and the visual pathways in your brain.

Importance of Test Results Interpretation

Accurate interpretation of visual field test results is critical for effective diagnosis and treatment planning. The results are presented as a detailed map showing areas where vision is normal, reduced, or absent. Key aspects of result interpretation include:

* Detection of Blind Spots: Identifying areas where vision is missing, which may indicate damage to the retina or optic nerve.
* Symmetry Analysis: Comparing the visual fields of both eyes to detect asymmetrical vision loss, which can be a sign of neurological conditions.
* Severity and Progression: Monitoring changes over time to assess the progression of diseases like glaucoma.

Patients typically receive a detailed explanation of their test results from an eye care professional, including recommendations for treatment or follow-up testing if necessary.

Uses of a Visual Field Test

Visual field tests serve a variety of purposes in both ophthalmology and neurology. Common uses include:

* Glaucoma Diagnosis and Monitoring: Identifies early signs of vision loss associated with glaucoma and tracks progression.
* Assessment of Retinal Disorders: Detects damage caused by conditions like diabetic retinopathy or retinal detachment.
* Optic Nerve Evaluation: Evaluates the health of the optic nerve, often impacted by optic neuritis or optic neuropathy.
* Neurological Conditions: Identifies vision changes due to strokes, brain tumors, or other neurological disorders.
* Pre-Surgical Planning: Assists in determining the extent of vision impairment before eye surgeries.
* Evaluation of Medication Effects: Monitors vision changes in patients taking medications that may affect eye health.

How to Prepare for a Visual Field Test

Proper preparation ensures accurate results from a visual field test. Follow these steps to get ready:

* Inform Your Eye Doctor: Share your medical history, including any eye conditions, neurological issues, or medications you are taking.
* Rest Well: Ensure you are well-rested before the test to reduce fatigue, which can affect performance.
* Wear Glasses or Contacts if Needed: Bring any corrective eyewear to the appointment, as the test may require you to wear them.
* Avoid Driving Before the Test: The procedure may involve pupil dilation, temporarily affecting your ability to drive.
* Follow Specific Instructions: Your doctor may provide additional preparation guidelines based on your individual needs.

By following these steps, you can help ensure the test provides the most accurate representation of your visual field.

What to Expect During the Procedure

A visual field test is a painless and non-invasive procedure typically performed in an eye doctor's office. Here is what what you can expect:

* Positioning: You will sit in front of a specialized machine and place your chin on a rest to stabilize your head.
* Focus on a Target: You will be asked to focus on a central point while small lights or objects appear in different parts of your visual field.
* Responding to Stimuli: You'll press a button or verbally indicate when you see the lights.
* Eye-by-Eye Testing: Each eye is tested separately by covering the other eye.
* Duration: The test typically takes 15-30 minutes to complete.

Patients can resume normal activities immediately after the test unless they have had their pupils dilated, in which case temporary visual sensitivity may occur.

Normal Range for Visual Field Test Results

Normal results indicate that your visual field is intact and free of significant blind spots beyond the natural blind spot (caused by the optic nerve head). Specific findings in a normal test include:

* Symmetrical vision between both eyes.
* Full peripheral vision within the expected range for your age.
* No unexplained areas of vision loss or distortion.
* Abnormal results may require further investigation to determine the underlying cause and develop an appropriate treatment plan.

Benefits of a Visual Field Test

Visual field testing offers numerous benefits for maintaining eye and neurological health. These include:

* Early Detection: Identifies vision problems before noticeable symptoms develop.
* Comprehensive Assessment: Provides a detailed map of your visual capabilities.
* Monitoring Disease Progression: Tracks changes in vision over time for conditions like glaucoma.
* Guiding Treatment Decisions: Helps tailor treatments based on the specific pattern of vision loss.
* Preventing Vision Loss: Enables timely interventions to preserve remaining vision.

Limitations and Risks of a Visual Field Test

While visual field testing is highly beneficial, it has certain limitations and risks:

* False Positives or Negatives: Patient fatigue or inattention can lead to inaccurate results.
* Limited Scope: Does not provide detailed images of the eyes' internal structures.
* Temporary Discomfort: Prolonged focus during the test may cause mild eye strain.
* Not a Standalone Diagnostic Tool: Often combined with other tests for a complete evaluation.

Understanding these limitations can help set realistic expectations for the procedure.

Frequently Asked Questions (FAQs) About Visual Field Tests:

1. Why is a visual field test important?

A visual field test is essential for detecting early signs of eye and neurological conditions, including glaucoma and optic nerve damage. It provides a detailed map of your field of vision, allowing doctors to diagnose problems that may not be noticeable during routine eye exams. Early detection through this test helps prevent further vision loss by enabling timely treatment and monitoring.

2. How often should I get a visual field test?

The frequency of visual field testing depends on your age, medical history, and risk factors. People with glaucoma or other eye conditions may need regular testing every 6-12 months. For routine eye health, adults should have a visual field test every 1-2 years as part of a comprehensive eye exam. Consult your doctor for personalized recommendations.

3. Is the visual field test painful?

No, the visual field test is completely painless and non-invasive. It involves sitting comfortably and responding to visual stimuli. Some patients may find it slightly tiring to maintain focus during the test, but there is no physical discomfort involved.

4. What do abnormal visual field test results mean?

Abnormal results indicate areas of reduced or missing vision, which could be caused by glaucoma, retinal conditions, optic nerve damage, or neurological issues like strokes. Your doctor will interpret the results and may recommend additional tests to determine the cause and guide treatment.

5. Can children undergo a visual field test?

Yes, children can undergo visual field testing if recommended by their doctor. The procedure is modified to suit their age and ability to follow instructions. It is often used to diagnose conditions like optic nerve disorders or monitor vision changes caused by neurological issues in children.

6. What is the difference between central and peripheral vision testing?

Central vision testing evaluates the ability to see details in the center of your vision, while peripheral vision testing assesses your ability to detect objects and movement in the outer areas of your field of vision. Visual field tests often include both types to provide a complete assessment.

7. Can a visual field test detect brain tumors?

Yes, a visual field test can help detect vision changes caused by brain tumors. Tumors affecting the optic pathways or visual centers in the brain can cause specific patterns of vision loss, which are identifiable through this test. Further imaging tests may be required for confirmation.

8. How accurate is a visual field test?

Visual field tests are highly accurate when performed correctly and under optimal conditions. Factors like patient attentiveness and proper calibration of the equipment influence the reliability of the results. Repeat testing may be necessary to confirm findings.

9. Are there alternatives to a visual field test?

Alternatives include fundus photography, optical coherence tomography (OCT), and perimetry tests. Each method has unique applications, and your doctor will choose the most appropriate one based on your condition and diagnostic needs.

10. What should I do if I fail a visual field test?

Failing a visual field test doesnâ€™t always mean permanent vision loss. It indicates areas requiring further investigation. Follow your doctorâ€™s recommendations for additional testing or treatment. Early intervention can often prevent further deterioration and improve outcomes.

Conclusion

The visual field test is an invaluable diagnostic tool for assessing and preserving eye and neurological health. By identifying early signs of vision loss and guiding treatment decisions, it plays a vital role in managing conditions like glaucoma and neurological disorders. While the procedure has certain limitations, its benefits in early detection and monitoring far outweigh them. Regular visual field testing, combined with comprehensive eye care, can help maintain optimal vision and quality of life. Consult your eye doctor to learn more about this important test and how it fits into your overall health plan.

Jai Ganesh · Science HQ

Arthritis

Gist

Arthritis is inflammation of one or more joints, causing pain, stiffness, and swelling. Common types include osteoarthritis (wear-and-tear) and rheumatoid arthritis (autoimmune). Key risk factors include age, genetics, and obesity. Treatments include medications, physical therapy, and lifestyle changes, aiming to manage symptoms and improve function.

Good approaches for arthritis include low-impact exercise, weight management, heat/cold therapy, and an anti-inflammatory diet rich in fruits, vegetables, fish, and whole grains, while avoiding processed foods and sugar, alongside potential medications, physical therapy, and sometimes surgery for severe cases, with lifestyle changes being key. Balancing activity and rest, maintaining good posture, and using assistive devices can also significantly ease symptoms.

Summary

Arthritis is a general medical term used to describe a disorder in which the smooth cartilagenous layer that lines a joint is lost, resulting in bone grinding on bone during joint movement. Symptoms generally include joint pain and stiffness. Other symptoms may include redness, warmth, swelling, and decreased range of motion of the affected joints. In certain types of arthritis, other organs, such as the skin, are also affected. Onset can be gradual or sudden.

There are several types of arthritis. The most common forms are osteoarthritis (most commonly seen in weightbearing joints) and rheumatoid arthritis. Osteoarthritis usually occurs as a person ages and often affects the hips, knees, shoulders, and fingers. Rheumatoid arthritis is an autoimmune disorder that often affects the hands and feet. Other types of arthritis include gout, lupus, and septic arthritis. These are inflammatory based types of rheumatic disease.

Early treatment for arthritis commonly includes resting the affected joint and conservative measures such as heating or icing. Weight loss and exercise may also be useful to reduce the force across a weightbearing joint. Medication intervention for symptoms depends on the form of arthritis. These may include anti-inflammatory medications such as ibuprofen and paracetamol (acetaminophen). With severe cases of arthritis, joint replacement surgery may be necessary.

Osteoarthritis is the most common form of arthritis affecting more than 3.8% of people, while rheumatoid arthritis is the second most common affecting about 0.24% of people. In Australia about 15% of people are affected by arthritis, while in the United States more than 20% have a type of arthritis. Overall arthritis becomes more common with age. Arthritis is a common reason people are unable to carry out their work and can result in decreased ability to complete activities of daily living. The term arthritis is derived from arthr- (meaning 'joint') and -itis (meaning 'inflammation').

Details:

Overview

Arthritis and other rheumatic diseases are common conditions that cause pain, swelling, and limited movement. They affect joints and connective tissues around the body. Millions of people in the U.S. have some form of arthritis.

Arthritis means redness and swelling (inflammation) of a joint. A joint is where 2 or more bones meet. There are more than 100 different arthritis diseases. Rheumatic diseases include any condition that causes pain, stiffness, and swelling in joints, muscles, tendons, ligaments, or bones. Arthritis is usually ongoing (chronic).

Arthritis and other rheumatic diseases are more common in women than men. These conditions are often found in older people. But people of all ages may be affected.

The 2 most common forms of arthritis are:

* Osteoarthritis. This is the most common type of arthritis. It is a chronic disease of the joints, especially the weight-bearing joints of the knee, hip, and spine. It destroys the padding on the ends of bones (cartilage) and narrows the joint space. It can also cause bone overgrowth, bone spurs, and reduced function. It occurs in most people as they age. It may also occur in young people from an injury or overuse.

* Rheumatoid arthritis. This is an autoimmune disease that causes inflammation in the joint linings. The inflammation may affect all the joints. It can also affect organs, such as the heart or lungs.

Other forms of arthritis or related disorders include:

* Gout. This condition causes uric acid crystals to build up in small joints, such as the big toe. It causes pain and inflammation.

* Lupus. This is a chronic autoimmune disorder. It causes periods of inflammation and damage in joints, tendons, and organs.

* Scleroderma. This autoimmune disease causes thickening and hardening of the skin and other connective tissue in the body.

* Ankylosing spondylitis. This form of arthritis causes inflammation of the spinal joints. It may lead to severe chronic pain and discomfort. In more advanced cases, sections of the bones fuse together in an immobile position. It can also cause inflammation in other parts of the body. Though it primarily affects the spine, it can also affect the shoulders, hips, ribs, and the small joints of the hands and feet.

* Juvenile idiopathic arthritis or juvenile rheumatoid arthritis. This is a form of arthritis in children under the age of 16 that causes inflammation and joint stiffness. Children may have symptoms that last a limited time, such as a few months or years or in some cases a lifetime. Getting diagnosed and treated early may help prevent joint damage.

What causes arthritis?

The cause depends on the type of arthritis. Osteoarthritis is caused by wear and tear of the joint over time or because of overuse. Rheumatoid arthritis, lupus, and scleroderma are caused by the body’s immune system attacking the body’s own tissues. Gout is caused by the buildup of crystals in the joints. Some forms of arthritis can be linked to genes. People with genetic marker HLA-B27 have a higher risk for ankylosing spondylitis. For some other forms of arthritis, the cause is not known.

Who is at risk for arthritis?

Some risk factors for arthritis that can’t be changed include:

* Age. The older you are, the more likely you are to have arthritis.

* Gender. Women are more likely to have arthritis than men.

* Heredity. Some types of arthritis are linked to certain genes.

Risk factors that may be changed include:

* Weight. Being overweight or obese can damage your knee joints. This can make them more likely to develop osteoarthritis.

* Injury. A joint that has been damaged by an injury is more likely to develop arthritis at some point.

* Infection. Reactive arthritis can affect joints after an infection.

* Your job. Work that involves repeated bending or squatting can lead to knee arthritis.

What are the symptoms of arthritis?

Each person’s symptoms may vary. The most common symptoms include:

* Pain in 1 or more joints that doesn’t go away, or comes back.

* Warmth and redness in 1 or more joints.

* Swelling in 1 or more joints.

* Stiffness in 1 or more joints.

* Trouble moving 1 or more joints in a normal way.

These symptoms can look like other health conditions. Always see your health care provider for a diagnosis.

How is arthritis diagnosed?

Your provider will take your medical history and give you a physical exam. Tests may also be done. These include blood tests, such as:

* Antinuclear antibody test. This checks antibody levels in the blood.

* Complete blood count. This checks if your white blood cell, red blood cell, and platelet levels are normal.

* Creatinine. This test checks for kidney disease.

* Sedimentation rate. This test can find inflammation.

* Hematocrit. This test measures the number of red blood cells.

* RF (rheumatoid factor) and CCP (cyclic citrullinated peptide) antibody tests. These can help diagnose rheumatoid arthritis.

* White blood cell count. This checks the level of white blood cells in your blood.

* Uric acid. This helps diagnose gout.

Other tests may be done, such as:

* Joint aspiration (arthrocentesis). A small sample of synovial fluid is taken from a joint. It's tested to see if crystals or bacteria are present.

* X-rays or other imaging tests. These can tell how damaged a joint is.

* Urine test. This checks for protein and different kinds of blood cells.

* HLA tissue typing. This looks for genetic markers of ankylosing spondylitis.

* Skin biopsy. Tiny tissue samples are removed and checked under a microscope. This test helps to diagnose a type of arthritis that involves the skin, such as lupus or psoriatic arthritis.

* Muscle biopsy. Tiny tissue samples are removed and checked under a microscope. This test helps to diagnose conditions that affect muscles.

How is arthritis treated?

Treatment will depend on your symptoms, your age, and your general health. It will also depend on what type of arthritis you have and how bad the condition is. A treatment plan is tailored to each person with their provider.

There is no known cure for arthritis. The goal of treatment is often to limit pain and inflammation and to help the joint work. Treatment plans often use both short-term and long-term methods.

Short-term treatments include:

* Medicines. Short-term relief for pain and inflammation may include pain relievers, such as acetaminophen, aspirin, ibuprofen, or other nonsteroidal anti-inflammatory medicines.

* Heat and cold. Pain may be eased by using moist heat (warm bath or shower) or dry heat (heating pad) on the joint. Pain and swelling may be eased with cold (ice pack wrapped in a thin towel) on the joint.

* Joint immobilization. Using a splint or brace can help a joint rest and protect it from more injury.

* Massage. Lightly massaging painful muscles may increase blood flow and bring warmth to the muscle.

* Transcutaneous electrical nerve stimulation (TENS). Pain may be eased with a TENS device. The device sends mild, electrical pulses to nerve endings in the painful area. This blocks pain signals to the brain and changes how you feel pain.

* Acupuncture. Thin needles are inserted at certain points in the body. It may help the release of natural pain-relieving chemicals made by the nervous system. The procedure is done by a licensed provider.

Long-term treatments include:

* Disease-modifying antirheumatic drugs. These prescription medicines may slow down the disease and treat any immune system problems linked to the disease. Examples of these medicines include methotrexate, hydroxychloroquine, sulfasalazine, and chlorambucil.

* Corticosteroids. Corticosteroids reduce inflammation and swelling. These medicines, such as prednisone, can be taken by mouth (orally) or as a shot.

* Hyaluronic acid therapy. This is a joint fluid that appears to break down in people with osteoarthritis. It can be injected into a joint, such as the knee to help ease symptoms.

* Surgery. There are many types of surgery, depending on which joints are affected. Surgery may include arthroscopy, fusion, or joint replacement. Full recovery after surgery may take up to 6 months. A rehabilitation program after surgery is an important part of the treatment.

Arthritis treatment can include a team of health care providers, such as:

* Orthopedist or orthopedic surgeon.

* Rheumatologist.

* Physiatrist.

* Primary care (family medicine or internal medicine).

* Rehabilitation nurse.

* Dietitian.

* Physical therapist.

* Occupational therapist.

* Social worker.

* Psychologist or psychiatrist.

* Recreational therapist.

* Vocational therapist.

What are possible complications of arthritis?

Because arthritis causes joints to get worse over time, it can cause disability. It can cause pain and movement problems. You may be less able to carry out normal daily activities and tasks.

Living with arthritis

There is no known cure for arthritis. But it’s important to help keep joints working by reducing pain and inflammation. Work on a treatment plan with your provider that includes medicine and therapy. Work on lifestyle changes that can improve your quality of life. Lifestyle changes include:

* Weight loss. Extra weight puts more stress on weight-bearing joints, such as the hips and knees.

* Exercise. Some exercises may help reduce joint pain and stiffness. These include swimming, walking, low-impact aerobic exercise, and range-of-motion exercises. Stretching exercises may also help keep the joints flexible.

* Activity and rest. To reduce stress on your joints, switch between activity and rest. This can help protect your joints and reduce your symptoms.

* Using assistive devices. Canes, crutches, and walkers can help keep stress off certain joints and improve balance. Make sure walkers, canes, and other mobility devices are adjusted to meet your height and posture.

* Using adaptive equipment. Resachers and grabbers let you extend your reach and reduce straining. Dressing aids help you get dressed more easily.

* Managing use of medicines. Long-term use of some anti-inflammatory medicines can lead to stomach bleeding and other possible side effects. Work with your to create a plan to reduce this risk and manage your pain.

When to contact your doctor

Contact your if you have questions about your medicines, your symptoms get worse, or you have new symptoms.

Additional Information

Arthritis is extremely common, especially in people older than 50. It causes joint pain, stiffness and inflammation. Your provider will help you understand which type of arthritis you have, what’s causing it and which treatments you’ll need. You may need a joint replacement if you have severe arthritis that you can’t manage with other treatments.

Overview:

What is arthritis?

Arthritis is a disease that causes damage in your joints. Joints are places in your body where two bones meet.

Some joints naturally wear down as you age. Lots of people develop arthritis after that normal, lifelong wear and tear. Some types of arthritis happen after injuries that damage a joint. Certain health conditions also cause arthritis.

Arthritis can affect any joint, but is most common in people’s:

* Hands and wrists.
* Knees.
* Hips.
* Feet and ankles.
* Shoulders.
* Lower back (lumbar spine).

A healthcare provider will help you find ways to manage symptoms like pain and stiffness. Some people with severe arthritis eventually need surgery to replace their affected joints.

Visit a healthcare provider if you’re experiencing joint pain that’s severe enough to affect your daily routine or if it feels like you can’t move or use your joints as well as usual.

Types of arthritis

There are more than 100 different types of arthritis. Some of the most common types include:

* Osteoarthritis: Wear and tear arthritis.
* Rheumatoid arthritis: Arthritis that happens when your immune system mistakenly damages your joints.
* Gout: Arthritis that causes sharp uric acid crystals to form in your joints.
* Ankylosing spondylitis: Arthritis that affects joints near your lower back.
* Psoriatic arthritis: Arthritis that affects people who have psoriasis.
* Juvenile arthritis: Arthritis in kids and teens younger than 16.

Depending on which type of arthritis you have, it can break down the natural tissue in your joint (degeneration) or cause inflammation (swelling). Some types cause inflammation that leads to degeneration.

How common is arthritis?

Arthritis is extremely common. Experts estimate that more than one-third of Americans have some degree of arthritis in their joints.

Osteoarthritis is the most common type. Studies have found that around half of all adults will develop osteoarthritis at some point.

Symptoms and Causes

There are more than 100 types of arthritis, but they share several common signs and symptoms.

The most common signs and symptoms of arthritis usually affect your joints and your ability to use them.

What are arthritis symptoms and signs?

The most common arthritis symptoms and signs include:

* Joint pain.
* Stiffness or reduced range of motion (how far you can move a joint).
* Swelling (inflammation).
* Skin discoloration.
* Tenderness or sensitivity to touch around a joint.
* A feeling of heat or warmth near your joints.

Where you experience symptoms depends on which type of arthritis you have, and which of your joints it affects.

Some types of arthritis cause symptoms in waves that come and go called flares or flare-ups. Others make your joints feel painful or stiff all the time, or after being physically active.

What is the main cause of arthritis?

What causes arthritis varies depending on which type you have:

* Osteoarthritis happens naturally as you age — a lifetime of using your joints can eventually wear down their cartilage cushioning.
* You may develop gout if you have too much uric acid in your blood (hyperuricemia).
* Your immune system can cause arthritis (including rheumatoid arthritis) when it damages your joints by mistake.
* Certain viral infections (including COVID-19) can trigger viral arthritis.
* Sometimes, arthritis happens with no cause or trigger. Providers call this idiopathic arthritis.

What are the risk factors?

Anyone can develop arthritis, but some factors may make you more likely to, including:

* Tobacco use: Smoking and using other tobacco products increases your risk.
* Family history: People whose biological family members have arthritis are more likely to develop it.
* Activity level: You might be more likely to have arthritis if you aren’t physically active regularly.
* Other health conditions: Having autoimmune diseases, obesity or any condition that affects your joints increases the chances you’ll develop arthritis.

Some people have a higher arthritis risk, including:

* People older than 50.
* Females.
* Athletes, especially those who play contact sports.
* People who have physically demanding jobs or do work that puts a lot of stress on their joints (standing, crouching, being on your hands and knees for a long time, etc.).

At what age does arthritis usually start?

Arthritis can develop at any age. When it starts depends on which type you have and what’s causing it.

In general, osteoarthritis affects adults older than 50. Rheumatoid arthritis usually develops in adults age 30 to 60.

Other types that have a more direct cause usually start closer to that specific trigger. For example, people with post-traumatic arthritis don’t develop it until after their joints are injured, and gout doesn’t develop until after you’ve had high uric acid levels for at least several months.

Talk to a healthcare provider about your unique arthritis risk, and when you should start watching for signs or changes in your joints.

Diagnosis and Tests:

How do healthcare providers diagnose arthritis?

A healthcare provider will diagnose arthritis with a physical exam. They’ll examine your affected joints and ask about your symptoms. Tell your provider when you first noticed symptoms like pain and stiffness, and if any activities or times of day make them worse.

Your provider will probably check your range of motion (how far you can move a joint). They may compare one joint’s range of motion to other, similar joints (your other knee, ankle or fingers, for example).

Arthritis tests

Your provider might use imaging tests to take pictures of your joints, including:

* X-ray.
* Ultrasound.
* Magnetic resonance imaging (MRI).
* A computed tomography (CT) scan.

These tests can help your provider see damage inside your joints. They can also help your provider rule out other injuries or issues that might cause similar symptoms, like bone fractures (broken bones).

Your provider may use blood tests to check your uric acid levels if they think you have gout. Blood tests can also show signs of infections or autoimmune diseases.

Management and Treatment:

What is arthritis treatment?

There’s no cure for arthritis, but your healthcare provider will help you find treatments that manage your symptoms. Which treatments you’ll need depend on what’s causing the arthritis, which type you have and which joints it affects.

The most common arthritis treatments include:

* Over-the-counter (OTC) anti-inflammatory medicine like NSAIDs or acetaminophen.
* Corticosteroids (prescription anti-inflammatory medicine, including cortisone shots).
* Disease-modifying antirheumatic drugs (DMARDs) if you have rheumatoid or psoriatic arthritis.
* Physical therapy or occupational therapy can help you improve your strength, range of motion and confidence while you’re moving.
* Surgery (usually only if nonsurgical treatments don’t relieve your symptoms).

Arthritis surgery

You may need surgery if you have severe arthritis and other treatments don’t work. The two most common types of arthritis surgery are joint fusion and joint replacement.

Joint fusion is exactly what it sounds like: surgically joining bones together. It’s most common for bones in your spine (spinal fusion) or your ankle (ankle fusion).

If your joints are damaged or you’ve experienced bone loss, you might need an arthroplasty (joint replacement). Your surgeon will remove your damaged natural joint and replace it with a prosthesis (artificial joint). You might need a partial or total joint replacement.

Your provider or surgeon will tell you which type of surgery you’ll need and what to expect.

Outlook / Prognosis:

What can I expect if I have arthritis?

You should expect to manage arthritis symptoms for a long time (probably the rest of your life). Your provider will help you find treatments that reduce how much (and how often) arthritis impacts your daily routine.

Some people with arthritis experience more severe symptoms as they age. Ask your provider how often you should have follow-up visits to check for changes in your joints.

Jai Ganesh · Jai Ganesh's Puzzles

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2734.

Jai Ganesh · This is Cool

2520) Fathometer

Gist

A fathometer is a specialized sonar-based instrument used to measure the depth of water (bathymetry) by calculating the time it takes for a sound wave to travel from the surface to the bottom and return as an echo. It is primarily used for navigation, mapping the seafloor, identifying fish, and checking ice thickness.

What is a fathometer used for measuring?

A fathometer is a device that measures the depth of water by measuring the time it takes for a sound wave to travel from the surface to the bottom and for its echo to be returned.

Summary

“A fathometer is a device that measures the depth of water by measuring the time it takes for a sound wave to travel from the surface to the bottom and for its echo to be returned.”

“Echo sounding or depth sounding is the use of sonar for ranging, normally to determine the depth of water (bathymetry). It involves transmitting acoustic waves into water and recording the time interval between emission and return of a pulse; the resulting time of flight, along with knowledge of the speed of sound in water, allows determining the distance between sonar and target. This information is then typically used for navigation purposes or in order to obtain depths for charting purposes.”

Had the fathometer, or echo sounder, been available, it might have changed maritime warfare during the First World War. The Fathometer, first offered for sale in 1923, uses sound waves to quickly and accurately determine water depth and detect underwater objects, like submarines. Before echo sounders, sailors dropped and retrieved weighted hand-held lines (lead lines) to estimate water depth. After the sinking of Titanic in 1912, Canadian engineer Reginald A. Fessenden wanted to improve underwater object detection and communications. An expert in wireless radio technology, Fessenden built an electromagnetic device, called the oscillator, which produced underwater sound waves. These waves bounced off objects and, by measuring the echoes produced by the returning waves, users could estimate the position of the object. Tests in 1914 proved the oscillator could not only detect icebergs, but also determine water depth. Fessenden urged war planners to use the oscillator as a submarine detector, but with his prickly personality, he was rebuffed. After the war, the Submarine Signal Company of Boston incorporated Fessenden’s oscillator technology in the fathometer, opening a new era of navigation, subsurface detection, and marine mapping.

Herbert Grove Dorsey (April 24, 1876 – 1961) was an American engineer, inventor and physicist. He was principal engineer of the United States Coast and Geodetic Survey Radio sonic Laboratory in the 1930s. He invented the first practical fathometer, a water depth measuring instrument for ships.

The depth of the ocean is calculated by knowing how fast sound travels in the water (approximately 1,500 meters per second). This method of seafloor mapping is called echo sounding. … Water depth is typically measured by echo sounders that transmit sound at 12 kilohertz (kHz).

Depth finder, also called echo sounder, device used on ships to determine the depth of water by measuring the time it takes a sound (sonic pulse) produced just below the water surface to return, or echo, from the bottom of the body of water. … sonar devices are used to measure the depth of sea.

Details

A fathometer is a device that measures the depth of water by measuring the time it takes for a sound wave to travel from the surface to the bottom and for its echo to be returned.

A Fathometer is used in ocean sounding when the depth of water is considerably deep and keeps a continuous and precise record of the depth of water under the boat or ship on which it is placed. It is an echo-sounding device in which water depths are determined by measuring the time it takes for vibrations produced by sound waves to travel from a location near the top of the water to the bottom and back. Depending on the kind of water being utilised, it is calibrated to read depth in line with the velocity of sound in that water. A fathometer may either visually represent the depth of the water or graphically indicate the depth of the water on a roll that is continually rotating and can produce a virtual profile of that water body. The fathometer meaning is derived from the word fathom. Fathom is a unit of water depth. Herbert Grove Dorsey invented and patented the first practical fathometer in 1928.

Working of fathometer

Fathometer working is quite simple and accurate compared to older methods of distance measuring of water bodies like the lead lines. A fathometer contains the following parts:

1. Transmitting and receiving oscillators ( for sending and receiving the sound waves )

2. Recorder unit ( for the recording of data)

3. Transmitter / Power unit. (power supply)

The distance between the signal’s leaving pulse and its return is calculated by multiplying half of the time between the signal’s outgoing pulse and its return by the sound speed in the water, roughly 1.5 kilometres per second. When using echo-sounding for precise applications such as hydrography, it is necessary to measure the sound speed, which is commonly accomplished by submerging a sound velocity probe into the water. Echo sounding is a special-purpose use of sonar that is used to find the bottom of any water bodies.

The Fessenden Fathometer was one of the earliest commercial echo- machines, and it made use of the Fessenden oscillator to create sound waves. Submarine Signal Company fitted this for the first time aboard the M&M liner S.S. Berkshire in 1924.

The fathometer is more accurate because it obtains a sounding that is exactly vertical. The vessel’s speed causes it to diverge significantly from the vertical. The precision of 7.5 cm is possible in ports and harbours when the water is at normal levels and conditions. When there is a strong current, and the weather is not conducive to taking soundings with the lead line, a fathometer may be employed (an Old device to measure the depth of water). The fathometer has a higher sensitivity than the lead line.

Uses of fathometer

1. Fathometer echo sounding is a technique that is often employed in fishing. Variations in elevation are often associated with areas where fish gather. In addition, schools of fish will be recorded. Fishfinder is an echo-sounding instrument, similar to a fathometer, that is used by both recreational and commercial fishermen to locate fish and other marine life.

2. This fathometer is installed on almost all ships and submarines in order to get an idea of the depth of water bodies and the morphology of rocks and seabeds in the area surrounding the ships and submarines.

3. It may also be used to measure the rise and fall of the tides in areas where the water is shallow.

4. The lead line is also one of the techniques for measuring the depth of water bodies, but it takes time and cannot be used in bad weather, so it has limited applications. The fathometer, on the other hand, can be used in bad weather and provides a more accurate result in a shorter period of time, making it more useful.

5. The same technique as the fathometer is used to send out sonic pulses in order to identify underwater things.

6. When it comes to submarines, a fathometer is quite important. Along with shoal water protection, other peacetime applications include identifying fish, assessing the thickness of ice in Arctic areas, and mapping the ocean’s surface.

7. A fathometer, also known as a Sonic depth finder, may be used to create a profile of the ocean bottom by recording thousands of soundings each hour over a long period of time. The use of echo sounders in oceanography and survey work to locate underwater pinnacles and shoals is common practice among hydrographers.

Conclusion

A fathometer is a device that uses echo sounding to measure the depth of the ocean or any other water bodies. Fathom is the unit for measuring the depth of any water body. A fathometer is more useful compared to conventional instruments to measure the depth because it can be used in bad weather and is more accurate with only an error of ± 7 cm. A fathometer is also used to locate the iceberg below the sea surface and schools of fish.

Additional Information

A Fathometer is used in ocean sounding where the depth of water is too much, and to make a continuous and accurate record of the depth of water below the boat or ship at which it is installed. It is an echo-sounding instrument in which water depths are obtained be determining the time required for the sound waves to travel from a point near the surface of the water to the bottom and back. It is adjusted to read depth on accordance with the velocity of sound in the type of water in which it is being used. A fathometer may indicate the depth visually or indicate graphically on a roll which continuously goes on revolving and provide a
virtual profile of the lake or sea.

What are the components of echo sounding instrument?

The main parts of an echo-sounding apparatus are:
1. Transmitting and receiving oscillators.
2. Recorder unit.
3. Transmitter / Power unit.

It consists in recording the interval of time between the emission of a sound impulse direct to the bottom of the sea and the reception of the wave or echo, reflected from the bottom. If the speed of sound in that water is v and the time interval between the transmitter and receiver is t, the depth h is given by
h = ½ vt
…
Due to the small distance between the receiver and the transmitter, a slight correction is necessary in shallow waters. The error between the true depth and the recorded depth can be calculated very easily by simple geometry. If the error is plotted against the recorded depth, the true depth can be easily known. The recording of the sounding is produced by the action of a small current passing through chemically impregnated paper from a rotating stylus to an anode plate. The stylus is fixed at one end of a radial arm which revolves at constant speed. The stylus makes a record on the paper at the instants when the sound impulse is transmitted and when the echo returns to the receiver.

Advantage of echo-sounding

Echo-sounding has the following advantages over the older method of lead line and rod:

1. It is more accurate as a truly vertical sounding is obtained. The speed of the vessel does deviate it appreciably from the vertical. Under normal water conditions, in ports and harbors an accuracy of 7.5 cm may be obtained.
2. It can be used when a strong current is running and when the weather is unsuitable for the soundings to be taken with the lead line.
3. It is more sensitive than the lead line.
4. A record of the depth is plotted immediately and provides a continuous record of the bottom as the vessel moves forward.
5. The speed of sounding and plotting is increased.
6. The error due to estimation of water level in a choppy sea is reduced owing to the instability of the boat.
7. Rock underlying softer material is recorded and this valuable information is obtained more cheaply than would be the case where sub-marine borings are taken.

Making the soundings

If the depth is less than 25 m, the soundings can be taken when the boat is in motion. In the case of soundings with rod the leadsman stands in the bow and plunges the rod at a forward angle, depending on the speed o the boat, such that the rod is vertical when the boat reaches the point at which soundings is being recorded. The rod should be read very quickly. The nature of the bottom should also be recorded at intervals in the note-book.

If the sounding is taken with a lead, the leadsman stands in the bow of the boat and casts the lead forward at such a distances that the line will become vertical and will reach the bottom at a point where sounding is required. The lead is withdrawn from the water after the reading is taken. If the depth is great, the lead is not withdrawn from the water, but is lifted between the soundings.

Jai Ganesh · Dark Discussions at Cafe Infinity

2457) Fritz Albert Lipmann

Gist:

Work

In 1937 Hans Krebs presented a complete picture of an important part of metabolism—the citric acid cycle. In this process, which has several steps, nutrients are converted to other molecules with a large amount of chemical energy. An important piece of the process was still missing—a substance that along with a protein forms an enzyme that facilitates an important step. In 1946 the substance was discovered by Fritz Lipmann, who described its role plays and gave it the name coenzyme A.

Summary

Fritz Albert Lipmann (born June 12, 1899, Königsberg, Ger. [now Kaliningrad, Russia]—died July 24, 1986, Poughkeepsie, N.Y., U.S.) was a German-born American biochemist, who received (with Sir Hans Krebs) the 1953 Nobel Prize for Physiology or Medicine for the discovery of coenzyme A, an important catalytic substance involved in the cellular conversion of food into energy.

Lipmann earned an M.D. degree (1924) and a Ph.D. degree (1927) from the University of Berlin. He conducted research in the laboratory of the biochemist Otto Meyerhof at the University of Heidelberg (1927–30) and then did research at the Biological Institute of the Carlsberg Foundation (Carlsbergfondets Biologiske Institut), Copenhagen (1932–39), and at the Cornell Medical School, New York City (1939–41).

At Massachusetts General Hospital, Boston (1941–57), where he directed the biochemistry research department, and as professor of biological chemistry at the Harvard Medical School (1949–57), Lipmann found a catalytically active, heat-stable factor in pigeon liver extracts. He subsequently isolated (1947), named, and determined the molecular structure (1953) of this factor, coenzyme A (or CoA), which is now known to be bound to acetic acid as the end product of sugar and fat breakdown in the absence of oxygen. Coenzyme A is one of the most important substances involved in cellular metabolism; it helps in the conversion of amino acids, steroids, fatty acids, and hemoglobins into energy.

Lipmann taught or conducted research at the Rockefeller Institute, now Rockefeller University, New York City, from 1957 until his death.

Details

Fritz Albert Lipmann (June 12, 1899 – July 24, 1986) was a German-American biochemist and a co-discoverer in 1945 of coenzyme A. For this, together with other research on coenzyme A, he was awarded the Nobel Prize in Physiology or Medicine in 1953 (shared with Hans Adolf Krebs).

Early life and education

Lipmann was born in Königsberg, Germany, to a Jewish family. His parents were Gertrud (Lachmanski) and Leopold Lipmann, an attorney.

Lipmann studied medicine at the University of Königsberg, Berlin, and Munich, graduating in Berlin in 1924. He returned to Königsberg to study chemistry under Professor Hans Meerwein. In 1926 he joined Otto Meyerhof at the Kaiser Wilhelm Institute for Biology, Dahlem, Berlin, for his doctoral thesis. After that he followed Meyerhof to Heidelberg to the Kaiser Wilhelm Institute for Medical Research.

Career

From 1939 on, Lipmann lived and worked in the United States. He was a Research Associate in the Department of Biochemistry, Cornell University Medical College, New York from 1939 to 1941. He joined the research staff of the Massachusetts General Hospital in Boston in 1941, first as a Research Associate in the Department of Surgery, then heading his own group in the Biochemical Research Laboratory of the hospital. From 1949 to 1957 he was professor of biological chemistry at Harvard Medical School. From 1957 onwards, he taught and conducted research at Rockefeller University, New York City.

In 1953, Lipmann received one half of the Nobel Prize in Physiology and Medicine "for his discovery of co-enzyme A and its importance for intermediary metabolism." The other half of the award was won by Hans Adolf Krebs. Lipmann was awarded the National Medal of Science in 1966. He would try to dive further into his discovery by finding a variant of co-enzyme A, now known as Pantethine. He was an elected member of the American Academy of Arts and Sciences, the United States National Academy of Sciences, and the American Philosophical Society.

Lipmann introduced the specific squiggle designation (~) to indicate high energy-rich phosphate in energy-rich biomolecules like ATP in his essay "Metabolic Generation and Utilization of Phosphate Bond Energy." Of his work, he said "that in the field of biosynthesis we have a rare example of progress leading to simplification."

Personal life

In 1931, Lipmann married Elfreda M. Hall. They had one son.[2] Lipmann died in New York in 1986.The photo shows Mary Soames, not Elfreda Hall Lipmann[10] His widow died in 2008 at the age of 101.

Jai Ganesh · Jokes

Q: What is a squirrels favorite ballet?
A; The nutcracker.
* * *
Q: Why did the squirrel take apart the classic car?
A: To get down to the nuts and bolts.
* * *
Q: Why couldn't the squirrel eat the macadamia nut?
A: It was one tough nut to crack.
* * *
Q: What do you get when you cross a spider and a squirrel?
A: A bug that will run up your leg and eat your nuts.
* * *
Q: What did the Psychologist say to the Squirrel with multiple personalities?
A: You're one tough nut to crack!
* * *

Jai Ganesh · Dark Discussions at Cafe Infinity

Comedy Quotes - I

1. Life is a tragedy when seen in close-up, but a comedy in long-shot. - Charlie Chaplin

2. Socialism is a fraud, a comedy, a phantom, a blackmail. - Benito Mussolini

3. Even actresses that you really admire, like Reese Witherspoon, you think, 'Another romantic comedy?' You see her in something like 'Walk the Line' and think, 'God, you're so great!' And then you think, 'Why is she doing these stupid romantic comedies?' But of course, it's for money and status. - Gwyneth Paltrow

4. I know nothing about love and romance, so I prefer to stick to just comedy. - Sandra Bullock

5. Comedy just pokes at problems, rarely confronts them squarely. Drama is like a plate of meat and potatoes, comedy is rather the dessert, a bit like meringue. - Woody Allen

6. Brad will tell you. He puts a movie on, I'm asleep in 10 minutes. I have no patience. But the kids love action movies with comedy, Jackie Chan and all that. - Angelina Jolie

7. People know me. I'm not going to produce any cartwheels out there. I'm not going to belong on Comedy Central. I'll always be a tennis player, not a celebrity. - Pete Sampras

8. When you make a drama, you spend all day beating a guy to death with a hammer, or what have you. Or, you have to take a bite out of somebody's face. On the other hand, with a comedy, you yell at Billy Crystal for an hour, and you go home. - Robert De Niro.

Jai Ganesh · This is Cool

Tuvalu

Gist

Tuvalu is a small Polynesian island nation in the South Pacific, situated midway between Australia and Hawaii. Comprising nine low-lying coral atolls with a population of roughly 11,000, it faces severe threats from rising sea levels. Funafuti is the capital, and the country is known for its strong community culture and vulnerability to climate change.

Nobody visits Tuvalu much because it's incredibly remote, hard to get to with limited, expensive flights (from Fiji), lacks major tourist infrastructure, and faces an existential threat from climate change and rising sea levels, though it's open for visitors seeking a unique, off-the-beaten-path experience. Its tiny size, basic amenities, and high travel costs deter mass tourism, despite its natural beauty and Polynesian culture.

Summary

Tuvalu is a group of nine tiny islands in the South Pacific which won independence from the United Kingdom in 1978.

Five of the islands are coral atolls, the other four consist of land rising from the sea bed.

Formerly known as the Ellice Islands, all are low-lying, with no point on Tuvalu being higher than 4.5m above sea level. Local politicians have campaigned against climate change, arguing that it could see the islands swamped by rising sea levels.

Life on the islands is simple and often harsh. There are no streams or rivers, so the collection of rain is essential.

Coconut palms cover most of the islands, and copra - dried coconut kernel - is practically the only export commodity. Increasing salination of the soil threatens traditional subsistence farming.

Tuvalu has shown ingenuity by exploiting another source of income. It has sold its .tv internet suffix to a Californian company for several million dollars a year in continuing revenue. The company sells the suffix on to television broadcasters.

Fats

Capital: Funafuti

Population: 11,500

Area: 26 sq km

Languages: Tuvaluan, English

Life expectancy: 62 years (men) 67 years (women).

Details

Tuvalu is an island country in the Polynesian sub-region of Oceania in the Pacific Ocean, about midway between Hawaii and Australia. It lies east-northeast of the Santa Cruz Islands (which belong to the Solomon Islands), northeast of Vanuatu, southeast of Nauru, south of Kiribati, west of Tokelau, northwest of Samoa and Wallis and Futuna, and north of Fiji.

Tuvalu is composed of three reef islands and six atolls spread out between the latitude of 5° and 10° south and between the longitude of 176° and 180°. They lie west of the International Date Line. The 2022 census determined that Tuvalu had a population of 10,643, making it the 194th most populous country, exceeding only Niue and the Vatican City in population. Tuvalu's total land area is 25.14 square kilometres (9.71 sq mi).

The first inhabitants of Tuvalu were Polynesians arriving as part of the migration of Polynesians into the Pacific that began about three thousand years ago. Long before European contact with the Pacific islands, Polynesians frequently voyaged using canoes between the islands. Polynesian navigation skills enabled them to make elaborately planned journeys in either double-hulled sailing canoes or outrigger canoes. Scholars believe that the Polynesians spread out from Samoa and Tonga into the Tuvaluan atolls, which then served as a stepping stone for further migration into the Polynesian outliers in Melanesia and Micronesia.

In 1568, Spanish explorer and cartographer Álvaro de Mendaña became the first European known to sail through the archipelago, sighting the island of Nui during an expedition he was making in search of Terra Australis. The island of Funafuti, currently serving as the capital, was named Ellice's Island in 1819. Later, the whole group was named Ellice Islands by English hydrographer Alexander George Findlay. In the late 19th century, Great Britain claimed control over the Ellice Islands, designating them as within their sphere of influence. Between 9 and 16 October 1892, Captain Herbert Gibson of HMS Curacoa declared each of the Ellice Islands a British protectorate. Britain assigned a resident commissioner to administer the Ellice Islands as part of the British Western Pacific Territories (BWPT). From 1916 to 1975, they were managed as part of the Gilbert and Ellice Islands colony.

A referendum was held in 1974 to determine whether the Gilbert Islands and Ellice Islands should each have their own administration. As a result, the Gilbert and Ellice Islands colony legally ceased to exist on 1 October 1975; on 1 January 1976, the old administration was officially separated, and two separate British colonies, Kiribati and Tuvalu, were formed. On 1 October 1978, Tuvalu became fully independent as a sovereign state within the Commonwealth, and is a constitutional monarchy with Charles III as King of Tuvalu. On 5 September 2000, Tuvalu became the 189th member of the United Nations.

The islands do not have a significant amount of soil, so the country relies heavily on imports and fishing for food. Licensing fishing permits to international companies, grants and aid projects, and remittances to their families from Tuvaluan seafarers who work on cargo ships are important parts of the economy. Because it is a low-lying island nation, Tuvalu is extremely vulnerable to sea level rise due to climate change. It is active in international climate negotiations as part of the Alliance of Small Island States.

Additional Information

Tuvalu is a country in the west-central Pacific Ocean. It is composed of nine small coral islands scattered in a chain lying approximately northwest to southeast over a distance of some 420 miles (676 km).

The de facto capital is the village of Vaiaku, where most government offices are located. It is on Fongafale islet, a constituent part of Funafuti Atoll. Together with what is now Kiribati (formerly the Gilbert Islands), Tuvalu formed the British Gilbert and Ellice Islands Colony before separately gaining its independence in 1978.

The group includes both atolls and reef islands. The atolls—Nanumea, Nui, Nukufetau, Funafuti, and Nukulaelae—have islets encircling a shallow lagoon; the reef islands—Nanumanga, Niutao, Vaitupu, and Niulakita—are compact with a fringing reef. The islands are low-lying, most being 13 to 16 feet (4 to 5 meters) above sea level. There are no rivers; rain catchment and wells provide the only fresh water. Rainfall averages 100 inches (2,500 mm) in the north and 125 inches (3,175 mm) in the south. The prevailing winds are southeast trades; westerly storms occur from November to February. Daytime temperatures range from 80 to 85 °F (27 to 29 °C).

Because the soils are porous, agriculture is limited. Coconut palms thrive, and breadfruit trees, pandanus, taro, and bananas are grown. Pigs and chickens are raised, and seabirds, fish, and shellfish are caught for food. The islands increasingly depend on imported food.

People

The Tuvaluans are Polynesian, and their language, Tuvaluan, is closely related to Samoan. Nui, however, was heavily settled in prehistoric times by Micronesians from the Gilbert Islands (now Kiribati). English is taught in the schools and widely used. The vast majority of the population belongs to the Church of Tuvalu (the former Ellice Islands Protestant Church).

Although most people live on the outer islands in extended family households clustered into villages, about one-third of the population lives on Funafuti, the center of government and commerce. Population growth has been slowed by family planning; life expectancy at birth is about 60 years. About 10 percent of the population lives overseas, either pursuing education, working in the Nauru phosphate industry, or working on merchant ships.

Economy

Most Tuvaluans are subsistence farmers and are aided by remittances from relatives working overseas. A small quantity of copra is produced for export, the sale of stamps accounts for modest earnings, and fees are collected from foreign fishing fleets, but the country depends heavily on foreign aid. It imports most of its food, fuel, and manufactured goods. Fiji, Australia, New Zealand, and Japan are among the country’s major trade partners. Retailing is handled by community-based cooperative societies. Tuvalu uses Australian currency but also issues its own coinage. There is a single bank, a joint government-commercial venture.

Tuvalu has air links with Kiribati and Fiji; for international shipping, it depends on irregular regional services. Seaplanes have been used for interisland travel, but generally the outer islands depend on a single government vessel. Motorcycles are common on Funafuti, but there are few automobiles.

Government and society

Tuvalu is a constitutional monarchy within the Commonwealth, with the British monarch (through a governor-general) as head of state. The government is a parliamentary democracy with a unicameral legislature elected by universal adult suffrage. There are no political parties: the prime minister is chosen by and from the legislature. Tuvalu is a member of the South Pacific Forum.

Cultural life

The Tuvaluan lifestyle has been Westernized to an extent, but Western-style amenities are few. Only Funafuti has a regular electricity supply; the government publishes a brief news sheet, but there is no newspaper; a few motion pictures are shown; satellite television service is available only by subscription; and there is only a single radio station. Most Tuvaluans live in villages of a few hundred people, tend their gardens, and fish from handcrafted canoes. Traditional music and dancing still enjoy a strong following, along with Western forms. Volleyball, football (soccer), and cricket are popular. Tuvaluan life, despite modernization, still rests on a firm traditional base that emphasizes the importance of community consensus and identity.

History of Tuvalu

The first settlers were from Samoa and probably arrived in the 14th century ad. Smaller numbers subsequently arrived from Tonga, the northern Cook Islands, Rotuma, and the Gilbert Islands. Niulakita, the smallest and southernmost island, was uninhabited before European contact; the other islands were settled by the 18th century, giving rise to the name Tuvalu, or “Cluster of Eight.”

Europeans first discovered the islands in the 16th century through the voyages of Álvaro de Mendaña de Neira, but it was only from the 1820s, with visits by whalers and traders, that they were reliably placed on European charts. In 1863 labor recruiters from Peru kidnapped some 400 people, mostly from Nukulaelae and Funafuti, reducing the population of the group to less than 2,500. A few were later recruited for plantations in Queensland, Australia, as well as in Fiji, Samoa, and Hawaii. Concern over labor recruiting and a desire for protection helps to explain the enthusiastic response to Samoan pastors of the London Missionary Society who arrived in the 1860s. By 1900, Protestant Christianity was firmly established.

With imperial expansion the group, then known as the Ellice Islands, became a British protectorate in 1892 and part of the Gilbert and Ellice Islands Colony in 1916. There was a gradual expansion of government services, but most administration was through island governments supervised by a single district officer based in Funafuti. Ellice Islanders sought education and employment at the colonial capital in the Gilbert group or in the phosphate industry at Banaba or Nauru. During World War II, U.S. forces were based on Nanumea, Nukufetau, and Funafuti, but hostilities did not reach the group.

From the 1960s, racial tension and rivalries over employment emerged between Gilbertese and Ellice Islanders. Ellice Islanders’ demands for secession resulted in a referendum in 1974, transition to separate colonial status between October 1975 and January 1976, and independence as Tuvalu in 1978. After independence the main priorities were to establish the infrastructure for a separate, if small, nation, and to seek foreign assistance to match political independence with economic viability.

_131550289_bbcm_tuvalu_country_profile_191023.png.webp

Jai Ganesh · Science HQ

Tooth Decay

Gist

Tooth decay (dental caries) is the destruction of tooth enamel caused by acids from plaque-forming bacteria feeding on sugars. Key symptoms include toothaches, sensitivity, and white/brown stains. Treatments include fluoride, fillings, crowns, or root canals. It progresses through demineralization, enamel decay, dentin decay, and pulp damage.

Tooth decay is caused by bacteria in your mouth feeding on sugars and starches, producing acids that wear down tooth enamel, forming cavities. Poor dental hygiene allows plaque (a sticky film of bacteria and food debris) to build up, and frequent snacking on sugary/starchy foods creates more acid attacks, leading to enamel erosion and holes in the teeth.

Summary

Tooth decay, also known as caries, is the breakdown of teeth due to acids produced by bacteria. The resulting dental cavities may be many different colors, from yellow to black. Symptoms may include pain and difficulty eating. Complications may include inflammation of the tissue around the tooth, tooth loss and infection or abscess formation. Tooth regeneration is an ongoing stem cell–based field of study that aims to find methods to reverse the effects of decay; current methods are based on easing symptoms.

The cause of cavities is acid from bacteria dissolving the hard tissues of the teeth (enamel, dentin, and cementum). The acid is produced by the bacteria when they break down food debris or sugar on the tooth surface. Simple sugars in food are these bacteria's primary energy source, and thus a diet high in simple sugar is a risk factor. If mineral breakdown is greater than buildup from sources such as saliva, caries results. Risk factors include conditions that result in less saliva, such as diabetes mellitus, Sjögren syndrome, and some medications. Medications that decrease saliva production include psychostimulants, antihistamines, and antidepressants. Dental caries are also associated with poverty, poor cleaning of the mouth, and receding gums resulting in exposure of the roots of the teeth.

Prevention of dental caries includes regular cleaning of the teeth, a diet low in sugar, and small amounts of fluoride. Brushing one's teeth twice per day, and flossing between the teeth once a day is recommended. Fluoride may be acquired from water, salt or toothpaste among other sources. Treating a mother's dental cavities may decrease the risk in her children by decreasing the number of certain bacteria she may spread to them. Screening can result in earlier detection. Depending on the extent of destruction, various treatments can be used to restore the tooth to proper function, or the tooth may be removed. There is no known method to grow back large amounts of tooth. The availability of treatment is often poor in the developing world. Paracetamol (acetaminophen) or ibuprofen may be taken for pain.

Worldwide, approximately 3.6 billion people (48% of the population) have dental caries in their permanent teeth as of 2016. The World Health Organization estimates that nearly all adults have dental caries at some point in time. In baby teeth it affects about 620 million people or 9% of the population. They have become more common in both children and adults in recent years. The disease is most common in the developed world due to greater simple sugar consumption, but less common in the developing world. Caries is Latin for "rottenness".

Details

Tooth decay is the breakdown or destruction of tooth enamel, the hard outer surface of a tooth. Tooth decay can lead to cavities, also called dental caries. These are holes in the teeth. Cavities can get bigger with time if left untreated. A cavity can reach deep within a tooth, where the nerve endings are, leading to pain and sensitivity.

What causes tooth decay in a child?

Tooth decay is caused by bacteria and other things. It can happen when foods containing carbohydrates (sugars and starches) are left on the teeth. Such foods include milk, soda, raisins, candy, cake, fruit juices, cereals, and bread. Bacteria that normally live in the mouth change these foods, making acids. The combination of bacteria, food, acid, and saliva form a substance called plaque that sticks to the teeth. Over time, the acids made by the bacteria eat away at the tooth enamel, causing cavities.

Which children are at risk for tooth decay?

* All children have bacteria in their mouth. So all children are at risk for tooth decay. But the following may raise your child’s risk for it:

* High levels of the bacteria that cause cavities

* A diet high in sugars and starches

* Water supply that has limited or no fluoride in it

* Poor oral hygiene

* Less saliva flow than normal

What are the symptoms of tooth decay in a child?

Tooth decay may be a bit different for each child. Here is a common way that teeth develop decay and cavities:

* White spots begin to form on the teeth in areas affected. These spots mean that the enamel is starting to break down. They may lead to early sensitivity in the teeth.

* An early cavity is seen on the tooth. It has a light brown color.

* The cavity becomes deeper. It turns a darker shade of brown to black.

The symptoms of tooth decay and cavities vary from child to child. Cavities don’t always cause symptoms. Sometimes children don’t know they have a cavity until their dentist finds it. But your child may feel:

* Pain in the area around the tooth

* Sensitivity to certain foods, such as sweets and hot or cold drinks

How is tooth decay diagnosed in a child?

Your child’s dentist can often diagnose tooth decay based on:

* A complete history of your child

* An exam of your child’s mouth (oral cavity)

* Dental X-rays

How is tooth decay treated in a child?

Treatment will depend on your child’s symptoms, age, oral hygiene, and general health. It will also depend on how severe the condition is.

For children, some early tooth decay may be managed with conservative methods such as removal of plaque, cleansing the dental decay, remineralizing the teeth, use of supplemental fluoride, and dental sealants.

In most cases, treatment will require removing the decayed part of the tooth and replacing it with a filling. Fillings are materials placed in teeth to repair damage caused by tooth decay. They are also called restorations. There are different types of fillings:

* Direct restorations. These need a single visit to place a filling directly into a prepared hole. These fillings may be made out of silver, fine glass powders, acrylic acids, or resin. They are often tooth-colored.

* Indirect restorations. These may require 2 or more visits. They include inlays, onlays, veneers, crowns, and bridges. These are constructed with gold, base metal alloys, ceramics, or composites. Many of these materials can look like natural tooth enamel.

How can I help prevent tooth decay in my child?

You can help prevent tooth decay in your child with these simple steps:

* Start brushing your child’s teeth as soon as the first tooth appears. Brush the teeth, tongue, and gums for 2 minutes twice a day with a fluoride toothpaste. Or watch as your child brushes their teeth.

* For children younger than 3 years old, use only a small amount of toothpaste, about the size of a grain of rice. Starting at age 3, your child can use a pea-sized amount of toothpaste.

* Floss your child’s teeth daily after age 2.

* Make sure your child eats a well-balanced diet. Limit snacks that are sticky and high in sugars. These include chips, candy, cookies, cake, and soda drinks.

* Prevent the transfer of bacteria from your mouth to your child's. Don't share eating utensils. And don’t clean your baby’s pacifier with your saliva.

* If your child uses a bottle at bedtime, only put water in it. Juice and formula contain sugars that can lead to tooth decay.

* Talk with your child’s healthcare provider or dentist about using a fluoride supplement if you live in an area without fluoridated water. Also, ask about dental sealants and fluoride varnish. Both are put on the teeth.

* Schedule routine dental cleanings and exams for your child every 6 months.

Key points about tooth decay in children

* Tooth decay is the breakdown of tooth enamel. It can lead to holes in the teeth called cavities or dental caries.

* Tooth decay is caused by bacteria in the mouth. These bacteria make a sticky substance called plaque that can eat away at a tooth’s enamel.

* Poor oral hygiene can raise your child’s risk for tooth decay.

* A dentist can diagnose tooth decay with an exam and X-rays.

* Treatment may require removing the decayed part of the tooth and replacing it with a filling.

Additional Information

Cavities are holes, or areas of tooth decay, that form in your teeth surfaces. Causes include plaque buildup, eating lots of sugary snacks and poor oral hygiene. Treatments include dental fillings, root canal therapy and tooth extraction. The sooner you treat a cavity, the better your chance for a predictable outcome and optimal oral health.

Overview:

What is a cavity?

A cavity is a hole in a tooth that develops from tooth decay. Cavities form when acids in your mouth wear down (erode) your tooth’s hard outer layer (enamel). Anyone can get a cavity. Proper oral hygiene and regular dental cleanings can prevent cavities.

Another name for tooth cavities is dental caries.

Types of cavities

Cavities can start on any tooth surface. Here are common types of cavities and where they occur:

* Smooth surface: This slow-growing cavity dissolves tooth enamel. You can prevent it — and sometimes reverse it — with proper oral hygiene. People in their 20s often develop this form of tooth decay between their teeth.
* Pit and fissure decay: Cavities form on the top part of your tooth’s chewing surface. Decay also can affect the front side of your back teeth. Pit and fissure decay tends to start during the teenage years and progresses quickly.
* Root decay: Adults who have receding gums are more prone to root decay. Gum recession exposes your teeth roots to dental plaque and acid. Root decay is difficult to prevent and treat. (If you’re prone to gum recession, ask your dentist if you should schedule an appointment with a periodontist.)

How common are cavities?

More than 80% of Americans have at least one cavity by the time they enter their mid-30s. Cavities are one of the most common chronic diseases affecting people of all ages.

Who might get a cavity?

Tooth decay can happen at any age, although cavities are more common in children. This is because many children don’t brush properly or regularly enough and they tend to consume more sugary foods and drinks.

Many adults also get cavities. Sometimes, new decay develops around the edges of cavities treated in childhood. Adults are also more likely to have receding gums. This condition exposes your teeth roots to plaque, which can cause cavities.

Symptoms and Causes:

What are the signs of cavities?

Tooth decay on the outer enamel surface doesn’t usually cause pain or symptoms. You’re more likely to experience symptoms as decay reaches beyond the enamel into the dentin and pulp.

Cavity symptoms include:

* Bad breath or a bad taste in your mouth.
* Bleeding gums or other signs of gum disease.
* Facial swelling.
* Toothache or mouth pain.
* Tooth sensitivity to hot or cold foods or drinks.

Tooth decay stages

Cavities can affect all layers of your tooth.

There are five main tooth decay stages:

1. Demineralization: During this first stage, you may notice small, white, chalky spots on your tooth. This is due to the breakdown of minerals in your tooth enamel.
2. Enamel decay: Left untreated, tooth decay progresses and continues to break down your enamel. At this point, cavities (holes) may become noticeable. White spots may turn to a light brownish color.
3. Dentin decay: Dentin is the layer just beneath your tooth enamel. It’s much softer than your enamel. So, once plaque and bacteria reach this layer, cavities form faster. At this stage, you may notice teeth sensitivity. The spots on your teeth may also turn to a darker brown.
4. Pulp damage: Your tooth pulp is the innermost layer of your tooth. It contains nerves and blood vessels that transport nutrients and keep your tooth alive. When cavities reach your pulp, you may feel pain. You may also start to notice redness and swelling in the gums around your tooth. The spots on your tooth may turn darker brown or black.
5. Abscessed tooth: Left untreated, a deep cavity can cause infection. This results in a pocket of pus that forms at the tip of your tooth root (periapical abscess). Symptoms may include pain that radiates into your jaw or face. You may also develop facial swelling and swollen lymph nodes in your neck. At this point, a tooth abscess can spread to surrounding tissues and other areas of your body. In rare cases, infection can even spread to your brain or to your bloodstream (sepsis).

What causes cavities?

Many factors play a role in the development of cavities.

Here’s how it works:

* Bacteria in your mouth feed on sugary, starchy foods and drinks (fruit, candy, bread, cereal, sodas, juice and milk). The bacteria convert these carbohydrates into acids.
* Bacteria, acid, food and saliva mix to form dental plaque. This sticky substance coats your teeth.
* Without proper brushing and flossing, acids in plaque dissolve tooth enamel, creating cavities, or holes, in the enamel surface.

What are the risk factors for cavities?

Certain factors increase your risk of cavities, including:

* Dry mouth (xerostomia). Certain conditions (like Sjögren’s syndrome), or medications (like antidepressants) can make you more likely to develop dry mouth.
* Consuming sugary, starchy foods or drinks and snacking between meals.
* Family history of tooth decay.
* Gum recession.
* Previous radiation therapy to treat head and neck cancer.

Are cavities contagious?

While you can’t “catch” a cavity, the bacteria that cause cavities can pass from one person to another. In turn, any bacteria you pick up from another person (from kissing, for instance) can lead to tooth decay and other oral health issues over time.

Diagnosis and Tests:

How are cavities diagnosed?

Twice-a-year dental checkups are the best way to catch cavities early, before they worsen or grow larger. A dentist will use a number of instruments to examine your teeth. A tooth with a cavity will feel softer when your dentist probes it.

Your dentist may also take dental X-rays. These images show cavities before the decay is visible.

Management and Treatment:

How do you get rid of cavities?

Tooth decay treatment depends on the severity of your condition.

Cavity treatments include:

* Fluoride.
* Fillings.
* Root canal therapy.
* Tooth extraction.
* Fluoride

In the very early stages of tooth decay, fluoride treatments can repair damaged enamel — a process called remineralization. This can reverse the early signs of cavities. You may need prescription toothpaste and mouthwash, as well as fluoride treatments at the dental office.

Dental fillings

Once a hole forms in your tooth, a dentist drills out the decayed tissue and fills the hole. Dental fillings consist of composite resin (a tooth-colored material), silver amalgam or gold.

Root canal therapy

Root canal therapy relieves pain from advanced tooth decay. Endodontists (specialists who treat issues that affect a tooth’s root) usually perform the procedure. During root canal treatment, an endodontist removes the tooth pulp, then fills the canals and pulp chamber with gutta-percha (a special filling material). In some cases, you might also need a dental crown to strengthen the affected tooth.

Tooth extraction

If root canal therapy isn’t possible, your healthcare provider may recommend tooth extraction (pulling the tooth). You may need a dental bridge or dental implant to replace a pulled permanent tooth. Your dentist can tell you about your specific options.

Outlook / Prognosis:

What can I expect if I have cavities?

When tooth decay goes untreated for too long, you can lose a large portion of your tooth and need an extraction. Advanced tooth decay can lead to a severe infection inside your tooth and under your gums (tooth abscess). This infection can spread throughout your body. Rarely, infection from a tooth abscess can be fatal.

What’s the outlook for people with cavities?

Most people with cavities don’t experience any long-term problems. Because cavities develop slowly, it’s important to get regular dental checkups. Fluoride treatments can stop tooth decay in its early stages. Once tooth decay advances to the root, you risk losing the tooth or developing a painful abscess (infection).

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2519) Potassium Dichromate

Gist

Potassium dichromate is a bright red-orange, odorless crystalline inorganic compound and a strong, non-deliquescent oxidizing agent commonly used in laboratories and industries. As a hexavalent chromium compound, it is highly toxic, corrosive, and a significant allergen. It is widely used for chrome tanning, dyeing, photography, and as a primary analytical standard in redox titrations.

Potassium dichromate is a strong oxidizing agent used in leather tanning (chrome tanning), wood staining (darkening), photography, and as a reagent in analytical chemistry for titrations and purity tests (Schwertzer's solution). It's also used in manufacturing matches, fireworks, and pigments, as a catalyst, and to make chromic acid for etching, though its toxicity has restricted many of these applications.

Summary

Potassium dichromate (K2Cr2O7) is a bright red-orange crystalline compound widely used in laboratories and industries as an oxidizing agent. Its non-deliquescent nature makes it preferable to other dichromates. However, as a hexavalent chromium compound, it is highly toxic and harmful to health.

Potassium dichromate, an inorganic compound with a bright orange colour, is widely used as an oxidizing agent in laboratories and industries. It is produced by reacting chromates with sodium or potassium carbonate. Although it is less potent than potassium permanganate, it is valued for its stability in acid and resistance to light and organic matter. Potassium dichromate is used in cleaning glassware, etching, and photographic screen printing. However, it is highly toxic and must be handled carefully due to its health hazards. As a dichromic acid dipotassium salt, it is one of the most significant and widely used chromium compounds in inorganic chemistry.

Physical Properties of Potassium Dichromate

Appearance: Solid at room temperature with bright orange crystals.
Odor and Taste: Odorless with a bitter taste.
Toxicity: It is toxic and can irritate the eyes.
Combustibility: Non-combustible but prone to rusting.
Melting and Boiling Points: Melts at 398°C and decomposes upon boiling at 500°C.
Solubility: Solubility increases in water at higher temperatures but is insoluble in alcohol and acetone.
Refractive Index: 1.738.
Structure: The chromium ion in potassium dichromate has a tetrahedral coordinate geometry. The crystalline structure is triclinic.

Details

Potassium dichromate is the inorganic compound with the formula K2Cr2O7. An orange solid, it is used in diverse laboratory and industrial applications. As with all hexavalent chromium compounds, it is chronically harmful to health. It is a crystalline ionic solid with a very bright, red-orange color. The salt is popular in laboratories because it is not deliquescent, in contrast to the more industrially relevant salt sodium dichromate.

Niche or archaic uses

Potassium dichromate has few major applications, as the sodium salt is dominant industrially. The main use is as a precursor to potassium chrome alum, used in leather tanning.

Photography and printing

In 1839, Mungo Ponton discovered that paper treated with a solution of potassium dichromate was visibly tanned by exposure to sunlight, the discoloration remaining after the potassium dichromate had been rinsed out. In 1852, Henry Fox Talbot discovered that exposure to ultraviolet light in the presence of potassium dichromate hardened organic colloids such as gelatin and gum arabic, making them less soluble.

These discoveries soon led to the carbon print, gum bichromate, and other photographic printing processes based on differential hardening. Typically, after exposure, the unhardened portion was rinsed away with warm water, leaving a thin relief that either contained a pigment included during manufacture or was subsequently stained with a dye. Some processes depended on the hardening only, in combination with the differential absorption of certain dyes by the hardened or unhardened areas. Because some of these processes allowed the use of highly stable dyes and pigments, such as carbon black, prints with an extremely high degree of archival permanence and resistance to fading from prolonged exposure to light could be produced.

Dichromated colloids were also used as photoresists in various industrial applications, most widely in the creation of metal printing plates for use in photomechanical printing processes.

Chromium intensification or Photochromos uses potassium dichromate together with equal parts of concentrated hydrochloric acid diluted down to approximately 10% v/v to treat weak and thin negatives of black and white photograph roll. This solution reconverts the elemental silver particles in the film to silver chloride. After thorough washing and exposure to actinic light, the film can be redeveloped to its end-point yielding a stronger negative which is able to produce a more satisfactory print.

A potassium dichromate solution in sulfuric acid can be used to produce a reversal negative (that is, a positive transparency from a negative film). This is effected by developing a black and white film but allowing the development to proceed more or less to the end point. The development is then stopped by copious washing and the film then treated in the acid dichromate solution. This converts the silver metal to silver sulfate, a compound that is insensitive to light. After thorough washing and exposure to actinic light, the film is developed again allowing the previously unexposed silver halide to be reduced to silver metal. The results obtained can be unpredictable, but sometimes excellent results are obtained producing images that would otherwise be unobtainable. This process can be coupled with solarisation so that the end product resembles a negative and is suitable for printing in the normal way.

Cr(VI) compounds have the property of tanning animal proteins when exposed to strong light. This quality is used in photographic screen-printing.

In screen-printing a fine screen of bolting silk or similar material is stretched taut onto a frame similar to the way canvas is prepared before painting. A colloid sensitized with a dichromate is applied evenly to the taut screen. Once the dichromate mixture is dry, a full-size photographic positive is attached securely onto the surface of the screen, and the whole assembly exposed to strong light – times vary from 3 minutes to a half an hour in bright sunlight – hardening the exposed colloid. When the positive is removed, the unexposed mixture on the screen can be washed off with warm water, leaving the hardened mixture intact, acting as a precise mask of the desired pattern, which can then be printed with the usual screen-printing process.

Analytical reagent

Because it is non-hygroscopic, potassium dichromate was a common reagent in classical "wet tests" in analytical chemistry.

Aldehyde test

In an aqueous solution the color change exhibited can be used as a test to distinguish aldehydes from ketones. Aldehydes reduce dichromate from the +6 to the +3 oxidation state, changing the solution color from orange to green. A ketone will show no such change because it cannot be oxidized further, and so the solution will remain orange.

Wood treatment

Potassium dichromate is used to stain certain types of wood by darkening the tannins in the wood. It produces deep, rich browns that cannot be achieved with modern color dyes. It is a particularly effective treatment on mahogany.

Natural occurrence

Potassium dichromate occurs naturally as the rare mineral lópezite. It has only been reported as vug fillings in the nitrate deposits of the Atacama Desert of Chile and in the Bushveld igneous complex of South Africa.

Safety

Potassium dichromate is a prevalent allergen in patch tests (4.8%). Its presence in cement can cause contact dermatitis in construction workers after extended exposure. In general, it is one of the most common causes of chromium dermatitis. Aquatic organisms are vulnerable to poisoning by dichromate salts, but far less so than organic pollutants.

As with other Cr(VI) compounds, potassium dichromate is carcinogenic. The compound is also corrosive and exposure may damage eyes. Human exposure further causes impaired fertility.

Additional Information

Potassium Dichromate is an orange to red colored, crystalline, inorganic compound that emits toxic chromium fumes upon heating. Potassium dichromate is highly corrosive and is a strong oxidizing agent. This substance is used in wood preservatives, in the manufacture of pigments and in photomechanical processes, but is mainly replaced by sodium dichromate. Potassium dichromate primarily affects the respiratory tract causing ulcerations, shortness of breath, bronchitis, pneumonia and asthma but can also affect the gastrointestinal tract, liver, kidneys and immune system. This substance is a known human carcinogen and is associated with an increased risk of developing lung cancer and cancer of the sinonasal cavity.

Potassium dichromate or anhydrochromate is prepared by adding to the neutral yellow chromate of potassium in solution, a moderate quantity of one of the stronger acids.

Potassium permanganate is commercially prepared by mixing a solution of potassium hydroxide and powdered manganese oxide with oxidizing agents like potassium chlorate.

Preparation of Potassium Dichromate – K2Cr2O7

* Potassium dichromate is an important chemical used in industries as an oxidizing agent and for the preparation of many other compounds.
* Dichromates are usually prepared from chromates and this is obtained by the combination of chromite ore with sodium/potassium carbonate in the presence of air.

Applications of Potassium Dichromate

The primary application of K2Cr2O7 is in the preparation of potassium chrome alum, a compound which is used extensively in the tanning of leather. Chromic acid can also be prepared from this compound. Potassium dichromate is known to be used in the production of cement since it improves the texture and the density of the cement mixture.

Another important application of potassium dichromate is in the photography industry, where it is used in combination with a powerful mineral acid as an oxidizing agent for photographic screen printing. Since it is non-hygroscopic in nature, this compound is also employed for several wet tests in the field of analytical chemistry.

Frequently Asked Questions – FAQs

Q1: What is the use of potassium dichromate?
A1. It is used in many applications as an oxidizing agent and is also used in the preparation of different products such as waxes, paints, glues, etc. Potassium dichromate is carcinogenic and highly toxic as a compound of hexavalent chromium.

Q2: What does the potassium dichromate test for?
A2. For organic chemistry, potassium dichromate is an oxidizing agent that is milder than potassium permanganate. It is used for the oxidation of alcohol. This converts primary alcohols into aldehydes and carboxylic acids under more pressing conditions.

Q3: Is potassium dichromate light-sensitive?
A3. Clear, light-sensitive orange crystals. Potassium dichromate is used in cotton dyeing as chromium mordant. In black and white image processing, potassium dichromate is used as an intensifier.

Q4: What is the charge of potassium dichromate?
A4. K2Cr2O7 is the molecular formula. A reddish-brown colour as a solid and a molecular weight of 294.18 grams per mole is the physical properties of potassium dichromate. Potassium dichromate is also referred to as a compound of hexavalent chromium, and chromium oxidation is 6+.

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