Math Is Fun Forum

Superconductivity

Gist

Superconductivity is a quantum mechanical phenomenon occurring in certain materials cooled below a specific critical temperature, characterized by exactly zero electrical resistance and the expulsion of magnetic fields (Meissner effect). It allows for lossless energy transmission and magnetic levitation. Key applications include MRI machines, particle accelerators, and maglev trains. 

Superconductivity is when a material, cooled to very low temperatures, lets electricity flow through it with zero resistance, meaning no energy is lost as heat, and it also perfectly pushes away magnetic fields. Think of it like a perfect, frictionless highway for electrons, allowing current to flow forever without a power source once started, and even levitating magnets above it.

Summary

Superconductivity is a set of physical properties observed in superconductors: materials where electrical resistance vanishes and magnetic fields are expelled from the material. Unlike an ordinary metallic conductor, whose resistance decreases gradually as its temperature is lowered, even down to near absolute zero, a superconductor has a characteristic critical temperature below which the resistance drops abruptly to zero. An electric current through a loop of superconducting wire can persist indefinitely with no power source.

The superconductivity phenomenon was discovered in 1911 by Dutch physicist Heike Kamerlingh Onnes. Like ferromagnetism and atomic spectral lines, superconductivity is a phenomenon which can only be explained by quantum mechanics. It is characterized by the Meissner effect, the complete cancellation of the magnetic field in the interior of the superconductor during its transitions into the superconducting state. The occurrence of the Meissner effect indicates that superconductivity cannot be understood simply as the idealization of perfect conductivity in classical physics.

In 1986, it was discovered that some cuprate-perovskite ceramic materials have a critical temperature above 35 K (−238 °C). It was shortly found (by Ching-Wu Chu) that replacing the lanthanum with yttrium, i.e. making YBCO, raised the critical temperature to 92 K (−181 °C), which was important because liquid nitrogen could then be used as a refrigerant. Such a high transition temperature is theoretically impossible for a conventional superconductor, leading the materials to be termed high-temperature superconductors. The cheaply available coolant liquid nitrogen boils at 77 K (−196 °C) and thus the existence of superconductivity at higher temperatures than this facilitates many experiments and applications that are less practical at lower temperatures.

Details

superconductivity, complete disappearance of electrical resistance in various solids when they are cooled below a characteristic temperature. This temperature, called the transition temperature, varies for different materials but generally is below 20 K (−253 °C).

The use of superconductors in magnets is limited by the fact that strong magnetic fields above a certain critical value, depending upon the material, cause a superconductor to revert to its normal, or nonsuperconducting, state, even though the material is kept well below the transition temperature.

Suggested uses for superconducting materials include medical magnetic-imaging devices, magnetic energy-storage systems, motors, generators, transformers, computer parts, and very sensitive devices for measuring magnetic fields, voltages, or currents. The main advantages of devices made from superconductors are low power dissipation, high-speed operation, and high sensitivity.

Discovery

Superconductivity was discovered in 1911 by the Dutch physicist Heike Kamerlingh Onnes; he was awarded the Nobel Prize for Physics in 1913 for his low-temperature research. Kamerlingh Onnes found that the electrical resistivity of a mercury wire disappears suddenly when it is cooled below a temperature of about 4 K (−269 °C); absolute zero is 0 K, the temperature at which all matter loses its disorder. He soon discovered that a superconducting material can be returned to the normal (i.e., nonsuperconducting) state either by passing a sufficiently large current through it or by applying a sufficiently strong magnetic field to it.

For many years it was believed that, except for the fact that they had no electrical resistance (i.e., that they had infinite electrical conductivity), superconductors had the same properties as normal materials. This belief was shattered in 1933 by the discovery that a superconductor is highly diamagnetic; that is, it is strongly repelled by and tends to expel a magnetic field. This phenomenon, which is very strong in superconductors, is called the Meissner effect for one of the two men who discovered it. Its discovery made it possible to formulate, in 1934, a theory of the electromagnetic properties of superconductors that predicted the existence of an electromagnetic penetration depth, which was first confirmed experimentally in 1939. In 1950 it was clearly shown for the first time that a theory of superconductivity must take into account the fact that free electrons in a crystal are influenced by the vibrations of atoms that define the crystal structure, called the lattice vibrations. In 1953, in an analysis of the thermal conductivity of superconductors, it was recognized that the distribution of energies of the free electrons in a superconductor is not uniform but has a separation called the energy gap.

The theories referred to thus far served to show some of the interrelationships between observed phenomena but did not explain them as consequences of the fundamental laws of physics. For almost 50 years after Kamerlingh Onnes’s discovery, theorists were unable to develop a fundamental theory of superconductivity. Finally, in 1957 such a theory was presented by the physicists John Bardeen, Leon N. Cooper, and John Robert Schrieffer of the United States; it won for them the Nobel Prize for Physics in 1972. It is now called the BCS theory in their honour, and most later theoretical work is based on it. The BCS theory also provided a foundation for an earlier model that had been introduced by the Russian physicists Lev Davidovich Landau and Vitaly Lazarevich Ginzburg (1950). This model has been useful in understanding electromagnetic properties, including the fact that any internal magnetic flux in superconductors exists only in discrete amounts (instead of in a continuous spectrum of values), an effect called the quantization of magnetic flux. This flux quantization, which had been predicted from quantum mechanical principles, was first observed experimentally in 1961.

In 1962 the British physicist Brian D. Josephson predicted that two superconducting objects placed in electric contact would display certain remarkable electromagnetic properties. These properties have since been observed in a wide variety of experiments, demonstrating quantum mechanical effects on a macroscopic scale.

The theory of superconductivity has been tested in a wide range of experiments, involving, for example, ultrasonic absorption studies, nuclear-spin phenomena, low-frequency infrared absorption, and electron-tunneling experiments. The results of these measurements have brought understanding to many of the detailed properties of various superconductors.

Additional Information

At what most people think of as “normal” temperatures, all materials have some amount of electrical resistance. This means they resist the flow of electricity in the same way a narrow pipe resists the flow of water. Because of resistance, some energy is lost as heat when electrons move through the electronics in our devices, like computers or cell phones. For most materials, this resistance remains even if the material is cooled to very low temperatures. The exceptions are superconducting materials. Superconductivity is the property of certain materials to conduct direct current (DC) electricity without energy loss when they are cooled below a critical temperature (referred to as Tc). These materials also expel magnetic fields as they transition to the superconducting state.

Superconductivity is one of nature’s most intriguing quantum phenomena. It was discovered more than 100 years ago in mercury cooled to the temperature of liquid helium (about -452°F, only a few degrees above absolute zero). Early on, scientists could explain what occurred in superconductivity, but the why and how of superconductivity were a mystery for nearly 50 years.

In 1957, three physicists at the University of Illinois used quantum mechanics to explain the microscopic mechanism of superconductivity. They proposed a radically new theory of how negatively charged electrons, which normally repel each other, form into pairs below Tc. These paired electrons are held together by atomic-level vibrations known as phonons, and collectively the pairs can move through the material without resistance. For their discovery, these scientists received the Nobel Prize in Physics in 1972.

Following the discovery of superconductivity in mercury, the phenomenon was also observed in other materials at very low temperatures. The materials included several metals and an alloy of niobium and titanium that could easily be made into wire. Wires led to a new challenge for superconductor research. The lack of electrical resistance in superconducting wires means that they can support very high electrical currents, but above a “critical current” the electron pairs break up and superconductivity is destroyed. Technologically, wires opened whole new uses for superconductors, including wound coils to create powerful magnets. In the 1970s, scientists used superconducting magnets to generate the high magnetic fields needed for the development of magnetic resonance imaging (MRI) machines. More recently, scientists introduced superconducting magnets to guide electron beams in synchrotrons and accelerators at scientific user facilities.

In 1986, scientists discovered a new class of copper-oxide materials that exhibited superconductivity, but at much higher temperatures than the metals and metal alloys from earlier in the century. These materials are known as high-temperature superconductors. While they still must be cooled, they are superconducting at much warmer temperatures—some of them at temperatures above liquid nitrogen (-321°F). This discovery held the promise of revolutionary new technologies. It also suggested that scientists may be able to find materials that are superconducting at relatively high temperatures.

Since then, many new high-temperature superconducting materials have been discovered using educated guesses combined with trial-and-error experiments, including a class of iron-based materials. However, it also became clear that the microscopic theory that describes superconductivity in metals and metal alloys does not apply to most of these new materials, so once again the mystery of superconductivity is challenging the scientific community.

DOE Office of Science & Superconductivity

The DOE Office of Science, Office of Basic Energy Sciences has supported research on high-temperature superconducting materials since they were discovered. The research includes theoretical and experimental studies to unravel the mystery of superconductivity and discover new materials. Even though a complete understanding of the quantum mechanism is yet to be discovered, scientists have found ways to enhance superconductivity (increase the critical temperature and critical current) and have discovered many new families of high-temperature superconducting materials. Each new superconducting material offers scientists an opportunity to get closer to understanding how high-temperature superconductivity works and how to design new superconducting materials for advanced technological applications.

Superconductivity Facts

* Superconductivity was discovered in 1911 by Heike Kamerlingh-Onnes. For this discovery, the liquefaction of helium, and other achievements, he won the 1913 Nobel Prize in Physics.
* Five Nobel Prizes in Physics have been awarded for research in superconductivity (1913, 1972, 1973, 1987, and 2003).
* Approximately half of the elements in the periodic table display low temperature superconductivity, but applications of superconductivity often employ easier to use or less expensive alloys. For example, MRI machines use an alloy of niobium and titanium.

Q: Why did the Oreo go to the dentist?
A: Because it lost its filling.
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Q:  What do you call an ant dipped in chocolate?
A: Decad-ant.
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Q: What happens when you try to eat 5 candy bars at once?
A: Your gonna choke alot.
* * *
Q: What does it do before it rains candy?
A: It sprinkles!
* * *
Q: What do you call dancing chocolate bar?
A: Nestle Crunk bar.
* * *

Beaver

Gist

Beavers are famous for being "ecosystem engineers," known for building dams with sticks, mud, and rocks to create ponds, which reshapes landscapes, controls water flow, prevents erosion, and creates vital wetland habitats for many species. They are also known for their continuously growing, iron-rich orange teeth, paddle-like tails used for signaling and balance, thick waterproof fur, industrious nature (hence "busy as a beaver"), and for being the national symbol of Canada.

How strong is a beaver's bite?

When a beaver decides to bite it can unleash 180 pounds of pressure per square inch. To give you an idea of what that means… It takes about 160 pounds of pressure to break a human femur (the largest bone in your body). This is how they take down trees we would need chain saws for.

Summary

Beavers (genus Castor) are large semiaquatic rodents of the Northern Hemisphere. There are two existing species: the North American beaver (Castor canadensis) and the Eurasian beaver (C. fiber). Beavers are the second-largest living rodents, after capybaras, weighing up to 50 kg (110 lb). They have stout bodies with large heads, long chisel-like incisors, brown or gray fur, hand-like front feet, webbed back feet, and tails that are flat and scaly. The two species differ in skull and tail shape and fur color. Beavers can be found in a number of freshwater habitats, such as rivers, streams, lakes and ponds. They are herbivorous, consuming tree bark, aquatic plants, grasses and sedges.

Beavers build dams and lodges using tree branches, vegetation, rocks and mud; they chew down trees for building material. Dams restrict water flow, forming ponds, and lodges (usually built in ponds) serve as shelters. Their infrastructure creates wetlands used by many other species, and because of their effect on other organisms in the ecosystem, beavers are considered a keystone species. Adult males and females live in monogamous pairs with their offspring. After their first year, the young help their parents repair dams and lodges; older siblings may also help raise newly born offspring. Beavers hold territories and mark them using scent mounds made of mud, debris, and castoreum—a liquid substance excreted through the beaver's urethra-based castor sacs. Beavers can also recognize their kin by their anal gland secretions and are more likely to tolerate them as neighbors.

Historically, beavers have been hunted for their fur, meat, and castoreum. Castoreum has been used in medicine, perfume, and food flavoring; beaver pelts have been a major driver of the fur trade. Before protections began in the 19th and early 20th centuries, overhunting had nearly exterminated both species. Their populations have since rebounded, and they are listed as species of least concern by the IUCN Red List of mammals. In human culture, the beaver symbolizes industriousness, especially in connection with construction; it is the national animal of Canada.

Details

A beaver, (genus Castor), is either of two species of amphibious rodents native to North America, Europe, and Asia. Beavers are the largest rodents in North America and Eurasia and the second largest rodents worldwide. Their bodies extend up to 80 cm (31 inches) long and generally weigh 16–30 kg (35–66 pounds); however, beavers continue to grow throughout their life, and the heaviest beavers can weigh more than 50 kg (110 pounds). The distinctive tail is scaly, flat, and paddle-shaped and measures up to 45 cm (about 18 inches) long and 13 cm (5 inches) wide. Living in streams, rivers, marshes, and ponds and on the shorelines of large lakes, beavers construct dams of branches, stones, and mud, forming ponds that often cover many hectares. Ecologists often refer to beavers as “ecosystem engineers” because of their ability to alter the landscapes in which they live.

Beavers have short legs and a stout body with a small, broad, and blunt head. Massive chisel-shaped incisor teeth have orange outer enamel because iron has replaced calcium, and this makes them stronger than most rodent incisors. Upon submergence, folds of skin (valves) close the nostrils and the stubby rounded ears, and the eyes are protected by a membrane that keeps water out (nictitating membrane). The fur-lined lips close behind the incisors, blocking water from the mouth and lungs and allowing the animal to cut, peel, and carry branches underwater. Small front feet with five clawed digits dexterously manipulate food. The hind feet are quite large, and the five digits are connected by webbing, which makes them useful as paddles for propulsion underwater. Claws of the second hind digits are split and have serrated edges used for grooming the fur.

Fur consists of a grayish to brown layer of short, fine, and dense underfur that keeps water from reaching the skin. Over this layer are long, coarse, glossy guard hairs ranging in colour from yellowish brown through reddish brown to black; underparts of the animal are paler. Both sexes possess castor glands that exude a musky secretion (castoreum), which is deposited on mud or rocks to mark territorial boundaries. Anal glands secrete oil through skin pores to hair roots. From there it is distributed with the front feet and grooming claws over the whole body to keep the fur sleek, oily, and water-repellent.

Beavers are colonial and primarily nocturnal. Their characteristically dome-shaped island lodges are built of branches plastered with mud. In marshes, lakes, and small rivers, beavers may instead construct bank lodges, and in large rivers and lakes they excavate bank dens with an underwater entrance beneath tree roots or overhanging ledges. Each lodge is occupied by an extended family group of up to eight individuals: an adult pair, young of the year (kits), and yearlings from the previous litter. Lodges are usually 3 metres (10 feet) high and 6 metres (20 feet) across the base but can be as large as 5 metres (16 feet) high and 12 metres (39 feet) wide. One or more tunnel entrances open below the water’s surface and lead into a spacious central chamber above water level; the floor is covered with vegetation. An entry tunnel leads to the nest chamber above the waterline. In winter the moist walls freeze, adding insulation and making the lodge impenetrable to predators.

Beavers often construct a dam a short distance downstream from the lodge to deter predators. The dam impedes the flow of the stream and increases the depth of the water that surrounds the lodge. Dams also create additional wetland habitat for fish and waterfowl and contain or impede the downstream movement of oil spilled into rivers. Despite the environmental services these dams provide, land owners and farmers often regard beavers as nuisance animals because beavers sometimes destroy ornamental trees, devour crops, or flood roads and fields with water impounded behind their dams.

During winter beavers store some fat at the base of their tail, but they maintain body temperature primarily by huddling in the insulated lodge and being less active. They leave the lodge only to feed on branches cached beneath the ice. Slow swimmers, beavers can remain submerged for up to 15 minutes and propel themselves primarily with the webbed hind feet while the front feet are held tight against the body. On land they walk or run with a waddling gait. Their diet consists of the soft cambium layer beneath bark, as well as the buds, leaves, and twigs of certain trees (willows and aspens are preferred). Pond vegetation and bankside plants are also eaten. Herbaceous vegetation is consumed mostly during summer and woody matter during winter. Shrubs, saplings, and trees are felled by beavers, cut into portable lengths, and dragged along mud slides or floated through beaver-made canals to the lodge. Edible branches are cached underwater and anchored in mud near the lodge entrance, where they are to be eaten all winter when the beavers cannot break through the ice to cut fresh branches.

Beavers are monogamous, mating between January and March in the north and November or December in the south. One litter per year of one to nine (usually four) kits is born in the spring after a gestation of 105 days. Beavers communicate by postures, vocalization, scent marking, and tail slapping. When alarmed on land, they retreat to water and warn others by slapping the surface of the water with their tails, producing a loud, startling noise. Eagles, large hawks, and most large mammalian carnivores prey on beavers.

American beavers (Castor canadensis) occur throughout forested parts of North America to northern Mexico, including the southwestern United States and northern Florida. Beavers were at the heart of the fur trade during colonial times and contributed significantly to the westward settlement and development of North America and Canada. As the animal was trapped out in the east, trappers moved progressively westward, and settlers followed. Nearly extirpated by 1900 through excessive trapping for their luxuriant coat, they have reclaimed, either by natural movement or human reintroduction, much of their former natural range, and regulated trapping continues, particularly in Canada. American beavers have been introduced into Finland, where they are flourishing; by the 21st century the geographic range of this population had expanded into the Russian republic of Karelia.

Eurasian beavers (Castor fiber) were once found throughout temperate and boreal forests of the region (including Britain) except for the Mediterranean area and Japan. By the early 20th century this range had contracted, and at the beginning of the 21st century indigenous populations survived only in the Elbe and Rhône river drainages, southern Norway, France, Mongolia, China, and parts of Russia, especially northwestern Siberia and the Altai region. Efforts to reestablish the Eurasian species began in Sweden in the early 1920s. Since that time, Eurasian beavers have been reintroduced throughout Europe, western Siberia, western China, Mongolia, the Kamchatka Peninsula, and near the Amur River in the Russian Far East.

Beavers make up the family Castoridae (suborder Sciuromorpha, order Rodentia). With no close living relatives (the mountain beaver belongs to a separate family), modern beavers are remnants of a rich evolutionary history of 24 extinct genera extending back to the Late Eocene Age of Asia and the Early Oligocene of Europe and North America. Most were terrestrial burrowers, such as Palaeocastor, which is known by fossils from Late Oligocene–Early Miocene sediments of western Nebraska and eastern Wyoming. They probably lived in upland grasslands in large colonies, excavated extensive burrow systems, and grazed on the surface, their entire lifestyle being much like that of modern prairie dogs. The largest rodent that ever lived in North America was the amphibious giant beaver (Castoroides) of the Pleistocene Epoch. Fossils indicate that it had a body length of two metres (six feet) and was about the size of a black bear.

Additional Information

Beavers are famously busy, and they turn their talents to reengineering the landscape as few other animals can. When sites are available, beavers burrow in the banks of rivers and lakes. But they also transform less suitable habitats by building dams. Felling and gnawing trees with their strong teeth and powerful jaws, they create massive log, branch, and mud structures to block streams and turn fields and forests into the large ponds that beavers love.

Beaver Lodges

Domelike beaver homes, called lodges, are also constructed of branches and mud. They are often strategically located in the middle of ponds and can only be reached by underwater entrances. These dwellings are home to extended families of monogamous parents, young kits, and the yearlings born the previous spring.

Beavers are among the largest of rodents. They are herbivores and prefer to eat leaves, bark, twigs, roots, and aquatic plants.

Aquatic Adaptations

These large rodents move with an ungainly waddle on land but are graceful in the water, where they use their large, webbed rear feet like swimming fins, and their paddle-shaped tails like rudders. These attributes allow beavers to swim at speeds of up to five miles an hour. They can remain underwater for 15 minutes without surfacing, and have a set of transparent eyelids that function much like goggles. Their fur is naturally oily and waterproof.

There are two species of beavers, which are found in the forests of North America, Europe, and Asia. These animals are active all winter, swimming and foraging in their ponds even when a layer of ice covers the surface.

Thyroid / Thyroid Disease

Gist

Is thyroid a serious problem?

Yes, thyroid problems can be serious if left untreated, potentially causing heart issues, infertility, bone problems, and even life-threatening conditions like myxedema coma, but they are often manageable with timely diagnosis and consistent treatment, allowing for a normal life. The severity depends on the type (underactive hypothyroidism or overactive hyperthyroidism) and whether it's addressed, as complications can affect heart rate, weight, mood, and energy levels. 

To "reduce thyroid" (meaning manage thyroid health), focus on a balanced diet with selenium (nuts, seafood) and zinc, manage stress through yoga/meditation, exercise regularly, get enough sleep, avoid smoking and processed foods, and take prescribed medication if needed, always consulting a doctor for diagnosis and treatment of conditions like hypothyroidism or hyperthyroidism. Medical treatments vary from medications (levothyroxine for underactive, anti-thyroid drugs for overactive) to radioiodine therapy or surgery, depending on the specific disorder.

Summary

The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans, it is a butterfly-shaped gland located in the neck below the Adam's apple. It consists of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the isthmus (pl.: isthmi). Microscopically, the functional unit of the thyroid gland is the spherical thyroid follicle, lined with follicular cells (thyrocytes), and occasional parafollicular cells that surround a lumen containing colloid.

The thyroid gland secretes three hormones: the two thyroid hormones – triiodothyronine (T3) and thyroxine (T4) – and a peptide hormone, calcitonin. The thyroid hormones influence the metabolic rate and protein synthesis and growth and development in children. Calcitonin plays a role in calcium homeostasis.

Secretion of the two thyroid hormones is regulated by thyroid-stimulating hormone (TSH), which is secreted from the anterior pituitary gland. TSH is regulated by thyrotropin-releasing hormone (TRH), which is produced by the hypothalamus.

Thyroid disorders include hyperthyroidism, hypothyroidism, thyroid inflammation (thyroiditis), thyroid enlargement (goitre), thyroid nodules, and thyroid cancer. Hyperthyroidism is characterized by excessive secretion of thyroid hormones: the most common cause is the autoimmune disorder Graves' disease. Hypothyroidism is characterized by a deficient secretion of thyroid hormones: the most common cause is iodine deficiency. In iodine-deficient regions, hypothyroidism (due to iodine deficiency) is the leading cause of preventable intellectual disability in children. In iodine-sufficient regions, the most common cause of hypothyroidism is the autoimmune disorder Hashimoto's thyroiditis.

Details

The thyroid gland is a vital endocrine (hormone-producing) gland. It plays a major role in the metabolism, growth and development of the human body. It helps to regulate many body functions by constantly releasing a steady amount of thyroid hormones into the bloodstream. If the body needs more energy in certain situations – for instance, if it is growing or cold, or during pregnancy – the thyroid gland produces more hormones.

Location and structure of the thyroid gland

The thyroid gland is found at the front of the neck, under the voice box. It is butterfly-shaped: The two lobes on either side lie against and around the windpipe (trachea), and are connected at the front by a narrow strip of tissue known as the isthmus.

The thyroid typically weighs between 20 and 60 grams. It is surrounded by two fibrous capsules. The outer capsule is connected to the voice box muscles and many important blood vessels and nerves. There is loose connective tissue between the inner and the outer capsule, so the thyroid can move and change its position when we swallow.

The thyroid tissue consists of many individual lobules that are each enclosed in a thin layer of connective tissue. These lobules contain a great number of small sacs – called follicles – which store thyroid hormones in the form of little droplets.

What hormones does the thyroid make?

The thyroid gland produces three hormones:

* Triiodothyronine (T3)
* Tetraiodothyronine (T4), also called thyroxine
* Calcitonin

Only T3 and T4 are considered proper thyroid hormones. Calcitonin is made by C-cells. It is involved in calcium and bone metabolism.

Iodine is an important substance that is needed to make the thyroid hormones T3 and T4. Our bodies can’t produce this trace element, so we need to get enough of it in our diet. Iodine is absorbed into our bloodstream from food in our bowel. It is then carried to the thyroid gland, where it is used to make thyroid hormones.

How do the thyroid hormones work?

The more active T3 and T4 become in the body, the more the basal metabolic rate goes up (the amount of energy your body needs while at rest). They make all of the cells in the body work harder. This has the following effects, for example:

* Body temperature rises
* The heart beat becomes stronger and the pulse faster
* Food is used up more quickly because energy stored in the liver and muscles is broken down
* The brain matures (in children)
* Growth is promoted (in children)
* Activation of the nervous system leads to higher levels of attention and quicker reflexes

How is the production of hormones regulated?

Sometimes our bodies need more thyroid hormones, and sometimes they need less. To make the exact right amount of hormones, the thyroid gland needs the help of another gland: the pituitary gland. It is part of the brain and it regulates many of the processes inside our body. One of the things it does is to use the hormone TSH to control the amount of hormones the thyroid gland releases into the bloodstream.

Most of the thyroid hormones in the bloodstream are bound to proteins, which makes them inactive. If the body needs more hormones, T3 and T4 can be released from these proteins in the blood and do their job.

Thyroid problems and diseases

An overactive thyroid makes too many hormones (hyperthyroidism). An underactive thyroid doesn’t make enough hormones (hypothyroidism). Both of these imbalances can lead to many different symptoms.

The thyroid gland may get bigger too. Sometimes the whole thyroid gland becomes enlarged (diffuse goiter), and sometimes individual lumps called nodules grow in the gland (nodular goiter).

Various tests can be used to diagnose medical conditions affecting the thyroid.

Additional Information

Thyroid disease is an umbrella term for conditions that affect how your thyroid functions. Hypothyroidism and hyperthyroidism are the two main types of thyroid disease. But they each have multiple possible causes. Thyroid diseases are treatable — usually with medication.

Overview:

What is thyroid disease?

Thyroid disease is a general term for a medical condition that keeps your thyroid from making the right amount of hormones. It can affect people of all ages.

Your thyroid is a small, butterfly-shaped gland located at the front of your neck under your skin. It’s a part of your endocrine system and controls many of your body’s important functions by producing and releasing thyroid hormones, like thyroxine (T4) and triiodothyronine (T3).

Your thyroid’s main job is to control the speed of your metabolism (metabolic rate). This is the process of how your body transforms the food you consume into energy. All the cells in your body need energy to function. When your thyroid isn’t working properly, it can impact your entire body.

Types of thyroid disease

The two main types of thyroid disease are hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid). But they each have several conditions that can cause them.

Conditions that can cause hypothyroidism include:

* Hashimoto’s disease: This is a lifelong (chronic) autoimmune condition that can cause an underactive thyroid. It’s the most common cause of hypothyroidism in countries with widely available iodized salt and other iodine-enriched foods.
* Iodine deficiency: Your thyroid needs iodine to make thyroid hormone, so a lack of the mineral in your diet can lead to hypothyroidism. It’s the most common cause of hypothyroidism in countries that don’t have iodized salt widely available. It often causes goiter (enlarged thyroid).
* Congenital hypothyroidism: Sometimes, babies are born with a missing or underactive thyroid. “Congenital” means “present from birth.” About 1 in every 2,000 to 4,000 babies have congenital hypothyroidism.

Conditions that can cause hyperthyroidism include:

* Graves’ disease: This is a chronic autoimmune condition that causes an overactive thyroid. It’s the most common cause of hyperthyroidism.
* Thyroid nodules: These are abnormal lumps on your thyroid gland. If the nodules are hyperfunctioning, they can lead to hyperthyroidism.
* Excessive iodine: When you have too much iodine in your body, your thyroid makes more thyroid hormones than you need. You may develop excessive iodine by taking certain medications, like amiodarone (a heart medication).

Conditions that can cause both hypothyroidism and hyperthyroidism at different times include:

* Thyroiditis: This is inflammation (swelling) of your thyroid gland. It typically causes temporary hyperthyroidism at first and then temporary or chronic hypothyroidism.
* Postpartum thyroiditis: This is a relatively rare condition that affects some birthing parents after pregnancy. An estimated 5% of people may experience this in the year after giving birth. It typically causes hyperthyroidism first, followed by hypothyroidism. It’s usually temporary.

How common is thyroid disease?

Thyroid disease is very common. About 20 million people in the United States have some type of thyroid condition.

Symptoms and Causes:

What are the symptoms of thyroid disease?

There are a variety of symptoms you could experience if you have thyroid disease. Unfortunately, symptoms of a thyroid condition are often very similar to the signs of other medical conditions and stages of life. This can make it difficult to know if your symptoms are related to a thyroid issue or something else entirely.

For the most part, the symptoms of thyroid disease can be divided into two groups — those related to having too much thyroid hormone (hyperthyroidism) and those related to having too little thyroid hormone (hypothyroidism). The symptoms are often “opposites” between the two conditions. This is because hyperthyroidism speeds up your metabolism, and hypothyroidism slows down your metabolism.

Symptoms of hypothyroidism include:

* Slower-than-usual heart rate.
* Feeling tired (fatigue).
* Unexplained weight gain.
* Feeling sensitive to cold.
* Dry skin and dry and coarse hair.
* Depressed mood.
* Heavy menstrual periods (menorrhagia).

Symptoms of hyperthyroidism include:

* Faster-than-usual heart rate (tachycardia).
* Difficulty sleeping.
* Unexplained weight loss.
* Feeling sensitive to heat.
* Clammy or sweaty skin.
* Feeling anxious, irritable or nervous.
* Irregular menstrual cycles or a lack of periods (amenorrhea).

Both conditions can cause an enlarged thyroid (goiter), but it’s more common in hyperthyroidism.

What are the risk factors for thyroid disease?

You may be at a higher risk of developing a thyroid condition if you:

* Are female. Females are five to eight times more likely to have a thyroid condition.
* Have a family history of thyroid disease.
* Have Turner syndrome.
* Take a medication that’s high in iodine.
* Live in a country or area that doesn’t have iodized table salt, which can lead to iodine deficiency.
* Are older than 60, especially if you’re female.
* Have received radiation therapy to your head and/or neck.

Having an autoimmune disease also increases your risk, especially if you have:

* Pernicious anemia.
* Type 1 diabetes.
* Celiac disease.
* Addison’s disease (primary adrenal insufficiency).
* Lupus.
* Rheumatoid arthritis.
* Sjögren’s syndrome.

Colored Quotes

1. I often think that the night is more alive and more richly colored than the day. - Vincent Van Gogh

2. Memory is deceptive because it is colored by today's events. - Albert Einstein

3. A soldier will fight long and hard for a bit of colored ribbon. - Napoleon Bonaparte

4. Lying in bed would be an altogether perfect and supreme experience if only one had a colored pencil long enough to draw on the ceiling. - Gilbert K. Chesterton

5. No one has been barred on account of his race from fighting or dying for America, there are no white or colored signs on the foxholes or graveyards of battle. - John F. Kennedy

6. Race prejudice is not only a shadow over the colored it is a shadow over all of us, and the shadow is darkest over those who feel it least and allow its evil effects to go on. - Pearl S. Buck

7. The sea was our main entertainment. When company came, we set them before it on rugs, with thermoses and sandwiches and colored umbrellas, as if the water - blue, green, gray, navy or silver as it might be - were enough to watch. - Sylvia Plath

8. I have always been fascinated with precious stones, especially colored ones, and knew that I would eventually join the family business and be a jewelry designer some day. - Neelam Kothari.

Glacier

Gist

A glacier is a large, persistent body of dense ice that forms on land over centuries as snow accumulates, compresses, and recrystallizes, moving slowly downhill under its own weight. Covering about 10% of Earth's land, these "rivers of ice" store ~69% of the world's freshwater and are critical indicators of climate change.

A glacier is a large, persistent body of dense ice that forms on land from compacted snow and moves slowly downhill under its own weight and gravity, essentially acting as a "river of ice" that carves landscapes as it flows. They form in areas where snow accumulation exceeds melting over many years, compressing into solid glacial ice, and are crucial indicators of climate change, holding vast amounts of freshwater.

Summary

A glacier is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as crevasses and seracs, as it slowly flows and deforms under stresses induced by its weight. As it moves, it abrades rock and debris from its substrate to create landforms such as cirques, moraines, or fjords. Although a glacier may flow into a body of water, it forms only on land and is distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water.

On Earth, 99% of glacial ice is contained within vast ice sheets (also known as "continental glaciers") in the polar regions, but glaciers may be found in mountain ranges on every continent other than the Australian mainland, including Oceania's high-latitude oceanic island countries such as New Zealand. Between latitudes 35°N and 35°S, glaciers occur only in the Himalayas, Andes, and a few high mountains in East Africa, Mexico, New Guinea and on Zard-Kuh in Iran. With more than 7,000 known glaciers, Pakistan has more glacial ice than any other country outside the polar regions. Glaciers cover about 10% of Earth's land surface. Continental glaciers cover nearly 13 million {km}^{2} (5 million sq mi) or about 98% of Antarctica's 13.2 million sq km (5.1 million sq mi), with an average thickness of ice 2,100 m (7,000 ft). Greenland and Patagonia also have huge expanses of continental glaciers. The volume of glaciers, not including the ice sheets of Antarctica and Greenland, has been estimated at 170,000 {km}^{3}.

Glacial ice is the largest reservoir of fresh water on Earth, holding with ice sheets about 69% of the world's freshwater. Many glaciers from temperate, alpine and seasonal polar climates store water as ice during the colder seasons and release it later in the form of meltwater as warmer summer temperatures cause the glacier to melt, creating a water source that is especially important for plants, animals and human uses when other sources may be scant. However, within high-altitude and Antarctic environments, the seasonal temperature difference is often not sufficient to release meltwater.

Since glacial mass is affected by long-term climatic changes, e.g., precipitation, mean temperature, and cloud cover, glacial mass changes are considered among the most sensitive indicators of climate change and are a major source of variations in sea level.

A large piece of compressed ice, or a glacier, appears blue, as large quantities of water appear blue, because water molecules absorb other colors more efficiently than blue. The other reason for the blue color of glaciers is the lack of air bubbles. Air bubbles, which give a white color to ice, are squeezed out by pressure increasing the created ice's density.

Details

A glacier is any large mass of perennial ice that originates on land by the recrystallization of snow or other forms of solid precipitation and that shows evidence of past or present flow.

Exact limits for the terms large, perennial, and flow cannot be set. Except in size, a small snow patch that persists for more than one season is hydrologically indistinguishable from a true glacier. One international group has recommended that all persisting snow and ice masses larger than 0.1 square kilometre (about 0.04 square mile) be counted as glaciers.

General observations:

Main types of glaciers

Glaciers are classifiable in three main groups: (1) glaciers that extend in continuous sheets, moving outward in all directions, are called ice sheets if they are the size of Antarctica or Greenland and ice caps if they are smaller; (2) glaciers confined within a path that directs the ice movement are called mountain glaciers; and (3) glaciers that spread out on level ground or on the ocean at the foot of glaciated regions are called piedmont glaciers or ice shelves, respectively. Glaciers in the third group are not independent and are treated here in terms of their sources: ice shelves with ice sheets, piedmont glaciers with mountain glaciers. A complex of mountain glaciers burying much of a mountain range is called an ice field.

Distribution of glaciers

A most interesting aspect of recent geological time (some 30 million years ago to the present) has been the recurrent expansion and contraction of the world’s ice cover. These glacial fluctuations influenced geological, climatological, and biological environments and affected the evolution and development of early humans. Almost all of Canada, the northern third of the United States, much of Europe, all of Scandinavia, and large parts of northern Siberia were engulfed by ice during the major glacial stages. At times during the Pleistocene Epoch (from 2.6 million to 11,700 years ago), glacial ice covered 30 percent of the world’s land area; at other times the ice cover may have shrunk to less than its present extent. It may not be improper, then, to state that the world is still in an ice age. Because the term glacial generally implies ice-age events or Pleistocene time, in this discussion “glacier” is used as an adjective whenever reference is to ice of the present day.

Glacier ice today stores about three-fourths of all the fresh water in the world. Glacier ice covers about 11 percent of the world’s land area and would cause a world sea-level rise of about 90 metres (300 feet) if all existing ice melted. Glaciers occur in all parts of the world and at almost all latitudes. In Ecuador, Kenya, Uganda, and Irian Jaya (New Guinea), glaciers even occur at or near the Equator, albeit at high altitudes.

Glaciers and climate

The cause of the fluctuation of the world’s glacier cover is still not completely understood. Periodic changes in the heat received from the Sun, caused by fluctuations in the Earth’s orbit, are known to correlate with major fluctuations of ice sheet advance and retreat on long time scales. Large ice sheets themselves, however, contain several “instability mechanisms” that may have contributed to the larger changes in world climate. One of these mechanisms is due to the very high albedo, or reflectivity of dry snow to solar radiation. No other material of widespread distribution on the Earth even approaches the albedo of snow. Thus, as an ice sheet expands it causes an ever larger share of the Sun’s radiation to be reflected back into space, less is absorbed on the Earth, and the world’s climate becomes cooler. Another instability mechanism is implied by the fact that the thicker and more extensive an ice sheet is, the more snowfall it will receive in the form of orographic precipitation (precipitation resulting from the higher altitude of its surface and attendant lower temperature). A third instability mechanism has been suggested by studies of the West Antarctic Ice Sheet. Portions of an ice sheet called ice streams may periodically move rapidly outward, perhaps because of the buildup of a thick layer of wet, deformable material under the ice. Although the ultimate causes of ice ages are not known with certainty, scientists agree that the world’s ice cover and climate are in a state of delicate balance.

Only the largest ice masses directly influence global climate, but all ice sheets and glaciers respond to changes in local climate—particularly changes in air temperature or precipitation. The fluctuations of these glaciers in the past can be inferred by features they have left on the landscape. By studying these features, researchers can infer earlier climatic fluctuations.

Additional Information

Glaciers are large, thick masses of ice that form on land when fallen snow gets compressed into ice over many centuries.

Glaciers are massive bodies of slowly moving ice. Glaciers form on land, and they are made up of fallen snow that gets compressed into ice over many centuries. They move slowly downward from the pull of gravity.

Most of the world’s glaciers exist in the polar regions, in areas like Greenland, the Canadian Arctic, and Antarctica. Glaciers also can be found closer to the Equator in some mountain regions. The Andes Mountain range in South America contains some of the world’s largest tropical glaciers. About 2 percent of all the water on Earth is frozen in glaciers.

Glaciers can range in age from a couple hundred to thousands of years old. Most glaciers today are remnants of the massive ice sheets that covered Earth during the Ice Age. The Ice Age ended more than 10,000 years ago. During Earth’s history, there have been colder periods—when glaciers formed—and warmer periods—when glaciers melted.

Scientists who study glaciers are called glaciologists. Glaciologists began studying glaciers during the 19th century in order to look for clues about past ice ages. Today, glaciologists study glaciers for clues about global warming. Old photographs and paintings show that glaciers have melted away from mountain regions over time. Indeed, glaciers worldwide have been shrinking—and even disappearing—at an accelerated rate for the past several decades.

Among the scientists studying the changes in glaciers is Erin Christine Pettit, a glaciologist at the University of Alaska Fairbanks. Pettit observes and measures the flow, fracture, and retreat of glaciers. She uses this information to study how much water enters the oceans from melting glaciers. Melting glaciers are one factor contributing to the global sea-level rise.