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#1 This is Cool » Server » Today 00:22:37

Jai Ganesh
Replies: 0

Server

Gist

A server is a computer or system that provides resources, data, services, or programs to other computers, known as clients, over a network.

Summary

A server is a hardware device or software that processes requests sent over a network and replies to them. A client is the device that submits a request and waits for a response from the server. The computer system that accepts requests for online files and transmits those files to the client is referred to as a “server” in the context of the Internet.

What is a Server?

A Server is a program or a device that provides functionality for called clients which are other programs or devices. This architecture is called the client-server model.

A single overall computation is distributed across multiple processes or devices. Servers can provide various functionalities called services. These services include sharing data or resources among multiple clients or performing computations for a client. Multiple clients can be served by a single server, and a single client can use multiple servers.

Uses of Servers

A client process may run on the same device. It can also connect over a network to a server to run on a different device. Examples of servers may include database servers, mail servers, print servers, file servers, web servers, application servers, and game servers. Most frequently client-server systems are implemented by the request-response communication., i.e., a client sends a request to the server. In this model, the server performs some action and sends a response back to the client, typically with a result or acknowledgement.

Designating a computer as server-class hardware means that it is specialized for running servers on it. This implies that it is more powerful and reliable than standard personal computers. However large computing clusters may comprise many relatively simple, replaceable server components.

Details

A server is a software or hardware device that accepts and responds to requests made over a network. The device that makes the request, and receives a response from the server, is called a client. On the Internet, the term "server" commonly refers to the computer system that receives requests for a web files and sends those files to the client.

What are they used for?

Servers manage network resources. For example, a user may set up a server to control access to a network, send/receive e-mail, manage print jobs, or host a website. They are also proficient at performing intense calculations. Some servers are committed to a specific task or one website, often called dedicated servers. However, many servers today are shared servers that take on the responsibility of e-mail, DNS (domain name system), FTP, and multiple websites in the case of a web server.

Why are servers always on?

Because they are commonly used to deliver services that are constantly required, most servers are never turned off. Consequently, when servers fail, they can cause the network users and company many problems. To alleviate these issues, servers are commonly set up to be fault tolerant.

Examples of servers

The following list contains links to various server types.

* Application server
* Blade server
* Cloud server
* Database server
* Dedicated server
* Domain name service
* File server
* Mail server
* Print server
* Proxy server
* Standalone server
* Web server

How do other computers connect to a server?

With a local network, the server connects to a router or switch that all other computers on the network use. Once connected to the network, other computers can access that server and its features. For example, with a web server, a user could connect to the server to view a website, search, and communicate with other users on the network.

An Internet server works the same way as a local network server, but on a much larger scale. The server is assigned an IP address by InterNIC, or by web host.

Usually, users connect to a server using its domain name, which is registered with a domain name registrar. When users connect to the domain name (such as "computerhope.com"), the name is automatically translated to the server's IP address by a DNS resolver.

The domain name makes it easier for users to connect to the server, because the name is easier to remember than an IP address. Also, domain names enable the server operator to change the IP address of the server without disrupting the way that users access the server. The domain name can always remain the same, even if the IP address changes.

Where are servers stored?

In a business or corporate environment, a server and other network equipment are often stored in a closet or glass house. These areas help isolate sensitive computers and equipment from people who should not access them.

Servers that are remote or not hosted on-site are located in a data center. With these types of servers, the hardware is managed by another company and configured remotely by you or your company.

What is a Linux server?

A Linux server is a computer running a version of Linux that's connected to a network or the Internet. For example, many of the web servers that host web pages on the Internet are Linux servers.

Can my computer be a server?

Yes. Any computer, even a home desktop or laptop computer, can act as a server with the right software. For example, you could install an FTP server program on your computer to share files between other users on your network.

Although it is possible to have your home computer act as a server, keep the following ideas in mind.

* Your computer and the related server software must always be running to be accessible.
* When your computer is used as a server, its resources (e.g., processing and bandwidth) is taken away from what you have available to do other things.
* Connecting a computer to a network and the Internet can open up your computer to new types of attacks.
* If the service you're providing becomes popular, a typical computer may not have the necessary resources to handle all of the requests.

Additional Information

In computing, a server is a piece of computer hardware or software (computer program) that provides functionality for other programs or devices, called "clients". This architecture is called the client–server model. Servers can provide various functionalities, often called "services", such as sharing data or resources among multiple clients or performing computations for a client. A single server can serve multiple clients, and a single client can use multiple servers. A client process may run on the same device or may connect over a network to a server on a different device. Typical servers are database servers, file servers, mail servers, print servers, web servers, game servers, and application servers.

Client–server systems are usually most frequently implemented by (and often identified with) the request–response model: a client sends a request to the server, which performs some action and sends a response back to the client, typically with a result or acknowledgment. Designating a computer as "server-class hardware" implies that it is specialized for running servers on it. This often implies that it is more powerful and reliable than standard personal computers, but alternatively, large computing clusters may be composed of many relatively simple, replaceable server components.

Operation

Strictly speaking, the term server refers to a computer program or process (running program). Through metonymy, it refers to a device used for (or a device dedicated to) running one or several server programs. On a network, such a device is called a host. In addition to server, the words serve and service (as verb and as noun respectively) are frequently used, though servicer and servant are not. The word service (noun) may refer to the abstract form of functionality, e.g. Web service. Alternatively, it may refer to a computer program that turns a computer into a server, e.g. Windows service. Originally used as "servers serve users" (and "users use servers"), in the sense of "obey", today one often says that "servers serve data", in the same sense as "give". For instance, web servers "serve [up] web pages to users" or "service their requests".

The server is part of the client–server model; in this model, a server serves data for clients. The nature of communication between a client and server is request and response. This is in contrast with peer-to-peer model in which the relationship is on-demand reciprocation. In principle, any computerized process that can be used or called by another process (particularly remotely, particularly to share a resource) is a server, and the calling process or processes is a client. Thus any general-purpose computer connected to a network can host servers. For example, if files on a device are shared by some process, that process is a file server. Similarly, web server software can run on any capable computer, and so a laptop or a personal computer can host a web server.

While request–response is the most common client-server design, there are others, such as the publish–subscribe pattern. In the publish-subscribe pattern, clients register with a pub-sub server, subscribing to specified types of messages; this initial registration may be done by request-response. Thereafter, the pub-sub server forwards matching messages to the clients without any further requests: the server pushes messages to the client, rather than the client pulling messages from the server as in request-response.

Hardware

Hardware requirement for servers vary widely, depending on the server's purpose and its software. Servers often are more powerful and expensive than the clients that connect to them.

The name server is used both for the hardware and software pieces. For the hardware servers, it is usually limited to mean the high-end machines although software servers can run on a variety of hardwares.

Since servers are usually accessed over a network, many run unattended without a computer monitor or input device, audio hardware and USB interfaces. Many servers do not have a graphical user interface (GUI). They are configured and managed remotely. Remote management can be conducted via various methods including Microsoft Management Console (MMC), PowerShell, SSH and browser-based out-of-band management systems such as Dell's iDRAC or HP's iLo.

Large servers

Large traditional single servers would need to be run for long periods without interruption. Availability would have to be very high, making hardware reliability and durability extremely important. Mission-critical enterprise servers would be very fault tolerant and use specialized hardware with low failure rates in order to maximize uptime. Uninterruptible power supplies might be incorporated to guard against power failure. Servers typically include hardware redundancy such as dual power supplies, RAID disk systems, and ECC memory, along with extensive pre-boot memory testing and verification. Critical components might be hot swappable, allowing technicians to replace them on the running server without shutting it down, and to guard against overheating, servers might have more powerful fans or use water cooling. They will often be able to be configured, powered up and down, or rebooted remotely, using out-of-band management, typically based on IPMI. Server casings are usually flat and wide, and designed to be rack-mounted, either on 19-inch racks or on Open Racks.

These types of servers are often housed in dedicated data centers. These will normally have very stable power and Internet and increased security. Noise is also less of a concern, but power consumption and heat output can be a serious issue. Server rooms are equipped with air conditioning devices.

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#2 Re: This is Cool » Miscellany » Yesterday 22:54:29

2106) Muscular System

Gist

The muscular system is composed of specialized cells called muscle fibers. Their predominant function is contractibility. Muscles, attached to bones or internal organs and blood vessels, are responsible for movement. Nearly all movement in the body is the result of muscle contraction.

Summary

The muscular system is composed of specialized cells called muscle fibers. Their predominant function is contractibility. Muscles, attached to bones or internal organs and blood vessels, are responsible for movement. Nearly all movement in the body is the result of muscle contraction. Exceptions to this are the action of cilia, the flagellum on sperm cells, and amoeboid movement of some white blood cells.

The integrated action of joints, bones, and skeletal muscles produces obvious movements such as walking and running. Skeletal muscles also produce more subtle movements that result in various facial expressions, eye movements, and respiration.

In addition to movement, muscle contraction also fulfills some other important functions in the body, such as posture, joint stability, and heat production. Posture, such as sitting and standing, is maintained as a result of muscle contraction. The skeletal muscles are continually making fine adjustments that hold the body in stationary positions. The tendons of many muscles extend over joints and in this way contribute to joint stability. This is particularly evident in the knee and shoulder joints, where muscle tendons are a major factor in stabilizing the joint. Heat production, to maintain body temperature, is an important by-product of muscle metabolism. Nearly 85 percent of the heat produced in the body is the result of muscle contraction.

Details

Muscles play a part in every function of the body. The muscular system is made up of over 600 muscles. These include three muscle types: smooth, skeletal, and cardiac.

Only skeletal muscles are voluntary, meaning you can control them consciously. Smooth and cardiac muscles act involuntarily.

Each muscle type in the muscular system has a specific purpose. You’re able to walk because of your skeletal muscles. You can digest because of your smooth muscles. And your heart beats because of your cardiac muscle.

The different muscle types also work together to make these functions possible. For instance, when you run (skeletal muscles), your heart pumps harder (cardiac muscle), and causes you to breathe heavier (smooth muscles).

Keep reading to learn more about your muscular system’s functions.

1. Mobility

Your skeletal muscles are responsible for the movements you make. Skeletal muscles are attached to your bones and partly controlled by the central nervous system (CNS).

You use your skeletal muscles whenever you move. Fast-twitch skeletal muscles cause short bursts of speed and strength. Slow-twitch muscles function better for longer movements.

2. Circulation

The involuntary cardiac and smooth muscles help your heart beat and blood flow through your body by producing electrical impulses. The cardiac muscle (myocardium) is found in the walls of the heart. It’s controlled by the autonomic nervous system responsible for most bodily functions.

The myocardium also has one central nucleus like a smooth muscle.

Your blood vessels are made up of smooth muscles, and also controlled by the autonomic nervous system.

3. Respiration

Your diaphragm is the main muscle at work during quiet breathing. Heavier breathing, like what you experience during exercise, may require accessory muscles to help the diaphragm. These can include the abdominal, neck, and back muscles.

4. Digestion

Digestion is controlled by smooth muscles found in your gastrointestinal tract. This comprises the:

* mouth
* esophagus
* stomach
* small and large intestines
* rectum
* the last part of the digestive tract

The digestive system also includes the liver, pancreas, and gallbladder.

Your smooth muscles contract and relax as food passes through your body during digestion. These muscles also help push food out of your body through defecation, or vomiting when you’re sick.

5. Urination

Smooth and skeletal muscles make up the urinary system. The urinary system includes the:

* kidneys
* bladder
* ureters
* urethra
* male or female reproductive organs
* prostate

All the muscles in your urinary system work together so you can urinate. The dome of your bladder is made of smooth muscles. You can release urine when those muscles tighten. When they relax, you can hold in your urine.

6. Childbirth

Smooth muscles are found in the uterus. During pregnancy, these muscles grow and stretch as the baby grows. When a woman goes into labor, the smooth muscles of the uterus contract and relax to help push the baby through the math.

7. Vision

Your eye sockets are made up of six skeletal muscles that help you move your eyes. And the internal muscles of your eyes are made up of smooth muscles. All these muscles work together to help you see. If you damage these muscles, you may impair your vision.

8. Stability

The skeletal muscles in your core help protect your spine and help with stability. Your core muscle group includes the abdominal, back, and pelvic muscles. This group is also known as the trunk. The stronger your core, the better you can stabilize your body. The muscles in your legs also help steady you.

9. Posture

Your skeletal muscles also control posture. Flexibility and strength are keys to maintaining proper posture. Stiff neck muscles, weak back muscles, or tight hip muscles can throw off your alignment. Poor posture can affect parts of your body and lead to joint pain and weaker muscles. These parts include the:

* shoulders
* spine
* hips
* knees

The bottom line

The muscular system is a complex network of muscles vital to the human body. Muscles play a part in everything you do. They control your heartbeat and breathing, help digestion, and allow movement.

Muscles, like the rest of your body, thrive when you exercise and eat healthily. But too much exercise can cause sore muscles. Muscle pain can also be a sign that something more serious is affecting your body.

The following conditions can affect your muscular system:

* myopathy (muscle disease)
* muscular dystrophy
* multiple sclerosis (MS)
* Parkinson’s disease
* fibromyalgia

Talk to your doctor if you have one of these conditions. They can help you find ways to manage your health. It’s important to take care of your muscles so they stay healthy and strong.

Additional Information

The muscular system is an organ system consisting of skeletal, smooth, and cardiac muscle. It permits movement of the body, maintains posture, and circulates blood throughout the body. The muscular systems in vertebrates are controlled through the nervous system although some muscles (such as the cardiac muscle) can be completely autonomous. Together with the skeletal system in the human, it forms the musculoskeletal system, which is responsible for the movement of the body.

Types

There are three distinct types of muscle: skeletal muscle, cardiac or heart muscle, and smooth (non-striated) muscle. Muscles provide strength, balance, posture, movement, and heat for the body to keep warm.

There are approximately 640 muscles in an adult male human body. A kind of elastic tissue makes up each muscle, which consists of thousands, or tens of thousands, of small muscle fibers. Each fiber comprises many tiny strands called fibrils, impulses from nerve cells control the contraction of each muscle fiber.

Skeletal

Skeletal muscle, is a type of striated muscle, composed of muscle cells, called muscle fibers, which are in turn composed of myofibrils. Myofibrils are composed of sarcomeres, the basic building blocks of striated muscle tissue. Upon stimulation by an action potential, skeletal muscles perform a coordinated contraction by shortening each sarcomere. The best proposed model for understanding contraction is the sliding filament model of muscle contraction. Within the sarcomere, actin and myosin fibers overlap in a contractile motion towards each other. Myosin filaments have club-shaped myosin heads that project toward the actin filaments, and provide attachment points on binding sites for the actin filaments. The myosin heads move in a coordinated style; they swivel toward the center of the sarcomere, detach and then reattach to the nearest active site of the actin filament. This is called a ratchet type drive system.

This process consumes large amounts of adenosine triphosphate (ATP), the energy source of the cell. ATP binds to the cross-bridges between myosin heads and actin filaments. The release of energy powers the swiveling of the myosin head. When ATP is used, it becomes adenosine diphosphate (ADP), and since muscles store little ATP, they must continuously replace the discharged ADP with ATP. Muscle tissue also contains a stored supply of a fast-acting recharge chemical, creatine phosphate, which when necessary can assist with the rapid regeneration of ADP into ATP.

Calcium ions are required for each cycle of the sarcomere. Calcium is released from the sarcoplasmic reticulum into the sarcomere when a muscle is stimulated to contract. This calcium uncovers the actin-binding sites. When the muscle no longer needs to contract, the calcium ions are pumped from the sarcomere and back into storage in the sarcoplasmic reticulum.

There are approximately 639 skeletal muscles in the human body.

Cardiac

Heart muscle is striated muscle but is distinct from skeletal muscle because the muscle fibers are laterally connected. Furthermore, just as with smooth muscles, their movement is involuntary. Heart muscle is controlled by the sinus node influenced by the autonomic nervous system.

Smooth

Smooth muscle contraction is regulated by the autonomic nervous system, hormones, and local chemical signals, allowing for gradual and sustained contractions. This type of muscle tissue is also capable of adapting to different levels of stretch and tension, which is important for maintaining proper blood flow and the movement of materials through the digestive system.

Physiology:

Contraction

Neuromuscular junctions are the focal point where a motor neuron attaches to a muscle. Acetylcholine, (a neurotransmitter used in skeletal muscle contraction) is released from the axon terminal of the nerve cell when an action potential reaches the microscopic junction called a synapse. A group of chemical messengers across the synapse and stimulate the formation of electrical changes, which are produced in the muscle cell when the acetylcholine binds to receptors on its surface. Calcium is released from its storage area in the cell's sarcoplasmic reticulum. An impulse from a nerve cell causes calcium release and brings about a single, short muscle contraction called a muscle twitch. If there is a problem at the neuromuscular junction, a very prolonged contraction may occur, such as the muscle contractions that result from tetanus. Also, a loss of function at the junction can produce paralysis.

Skeletal muscles are organized into hundreds of motor units, each of which involves a motor neuron, attached by a series of thin finger-like structures called axon terminals. These attach to and control discrete bundles of muscle fibers. A coordinated and fine-tuned response to a specific circumstance will involve controlling the precise number of motor units used. While individual muscle units contract as a unit, the entire muscle can contract on a predetermined basis due to the structure of the motor unit. Motor unit coordination, balance, and control frequently come under the direction of the cerebellum of the brain. This allows for complex muscular coordination with little conscious effort, such as when one drives a car without thinking about the process.

Tendon

A tendon is a piece of connective tissue that connects a muscle to a bone.[8] When a muscle intercept, it pulls against the skeleton to create movement. A tendon connects this muscle to a bone, making this function possible.

Aerobic and anaerobic muscle activity

At rest, the body produces the majority of its ATP aerobically in the mitochondria without producing lactic acid or other fatiguing byproducts. During exercise, the method of ATP production varies depending on the fitness of the individual as well as the duration and intensity of exercise. At lower activity levels, when exercise continues for a long duration (several minutes or longer), energy is produced aerobically by combining oxygen with carbohydrates and fats stored in the body.

During activity that is higher in intensity, with possible duration decreasing as intensity increases, ATP production can switch to anaerobic pathways, such as the use of the creatine phosphate and the phosphagen system or anaerobic glycolysis. Aerobic ATP production is biochemically much slower and can only be used for long-duration, low-intensity exercise, but produces no fatiguing waste products that can not be removed immediately from the sarcomere and the body, and it results in a much greater number of ATP molecules per fat or carbohydrate molecule. Aerobic training allows the oxygen delivery system to be more efficient, allowing aerobic metabolism to begin quicker. Anaerobic ATP production produces ATP much faster and allows near-maximal intensity exercise, but also produces significant amounts of lactic acid which render high-intensity exercise unsustainable for more than several minutes. The phosphagen system is also anaerobic. It allows for the highest levels of exercise intensity, but intramuscular stores of phosphocreatine are very limited and can only provide energy for exercises lasting up to ten seconds. Recovery is very quick, with full creatine stores regenerated within five minutes.

Clinical significance

Multiple diseases can affect the muscular system.

Muscular Dystrophy

Muscular dystrophy is a group of disorders associated with progressive muscle weakness and loss of muscle mass. These disorders are caused by mutations in a person’s genes. The disease affects between 19.8 and 25.1 per 100,000 person-years globally.

There are more than 30 types of muscular dystrophy. Depending on the type, muscular dystrophy can affect the patient's heart and lungs, and/or their ability to move, walk, and perform daily activities. The most common types include:

* Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD)
* Myotonic dystrophy
* Limb-Girdle (LGMD)
* Facioscapulohumeral dystrophy (FSHD)
* Congenital dystrophy (CMD)
* Distal (DD)
* Oculopharyngeal dystrophy (OPMD)
* Emery-Dreifuss (EDMD).

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#3 Re: Dark Discussions at Cafe Infinity » crème de la crème » Yesterday 19:00:45

1430) Arthur Leonard Schawlow

Summary

Arthur L. Schawlow (born May 5, 1921, Mount Vernon, New York, U.S.—died April 28, 1999, Palo Alto, California) American physicist and corecipient, with Nicolaas Bloembergen of the United States and Kai Manne Börje Siegbahn of Sweden, of the 1981 Nobel Prize for Physics for his work in developing the laser and in laser spectroscopy.

As a child, Schawlow moved with his family to Canada. He attended the University of Toronto, receiving his Ph.D. in 1949. In that year he went to Columbia University, where he began collaborating with Charles Townes on the development of the maser (a device that produces and amplifies electromagnetic radiation mainly in the microwave region of the spectrum), the laser (a device similar to the maser that produces an intense beam of light of a single colour), and laser spectroscopy. Schawlow worked on the project that led to the construction of the first working maser in 1953 (for which Townes received a share of the 1964 Nobel Prize for Physics). Schawlow was a research physicist at Bell Telephone Laboratories from 1951 to 1961. In 1958 he and Townes published a paper in which they outlined the working principles of the laser, though the first such working device was built by another American physicist, Theodore Maiman, in 1960. In 1961 Schawlow became a professor at Stanford University. He became a world authority on laser spectroscopy, and he and Bloembergen earned their share of the 1981 Nobel Prize by using lasers to study the interactions of electromagnetic radiation with matter. His works include Infrared and Optical Masers (1958) and Lasers and Their Uses (1983). A few years after winning the Nobel Prize, Schawlow wrote an article on the laser for Encyclopædia Britannica’s 1987 Yearbook of Science and the Future.

Details

Arthur Leonard Schawlow (May 5, 1921 – April 28, 1999) was an American physicist and co-inventor of the laser with Charles Townes. His central insight, which Townes overlooked, was the use of two mirrors as the resonant cavity to take maser action from microwaves to visible wavelengths. He shared the 1981 Nobel Prize in Physics with Nicolaas Bloembergen and Kai Siegbahn for his work using lasers to determine atomic energy levels with great precision.

Biography

Schawlow was born in Mount Vernon, New York. His mother, Helen (Mason), was from Canada, and his father, Arthur Schawlow, was a Jewish immigrant from Riga (then in the Russian Empire, now in Latvia). Schawlow was raised in his mother's Protestant religion. When Arthur was three years old, they moved to Toronto, Ontario, Canada.

At the age of 16, he completed high school at Vaughan Road Academy (then Vaughan Collegiate Institute), and received a scholarship in science at the University of Toronto (Victoria College). After earning his undergraduate degree, Schawlow continued in graduate school at the University of Toronto which was interrupted due to World War II. At the end of the war, he began work on his Ph.D at the university with Professor Malcolm Crawford. He then took a postdoctoral position with Charles H. Townes at the physics department of Columbia University in the fall of 1949.

He went on to accept a position at Bell Labs in late 1951. He left in 1961 to join the faculty at Stanford University as a professor. He remained at Stanford until he retired to emeritus status in 1996.

Although his research focused on optics, in particular, lasers and their use in spectroscopy, he also pursued investigations in the areas of superconductivity and nuclear resonance. Schawlow shared the 1981 Nobel Prize in Physics with Nicolaas Bloembergen and Kai Siegbahn for their contributions to the development of laser spectroscopy.

Schawlow coauthored the widely used text Microwave Spectroscopy (1955) with Charles Townes. Schawlow and Townes were the first to publish the theory of laser design and operation in their seminal 1958 paper on "optical masers", although Gordon Gould is often credited with the "invention" of the laser, due to his unpublished work that predated Schawlow and Townes by a few months. The first working laser was made in 1960 by Theodore Maiman.

In 1991, the NEC Corporation and the American Physical Society established a prize: the Arthur L. Schawlow Prize in Laser Science. The prize is awarded annually to "candidates who have made outstanding contributions to basic research using lasers."

Science and religion

He participated in science and religion discussions. Regarding God, he stated, "I find a need for God in the universe and in my own life."

Personal life

In 1951, he married Aurelia Townes, younger sister of his postdoctoral advisor, Charles Townes. They had three children: Arthur Jr., Helen, and Edith. Arthur Jr. is autistic, with very little speech ability.

Schawlow and Professor Robert Hofstadter at Stanford, who also had an autistic child, teamed up to help each other find solutions to the condition. Arthur Jr. was put in a special center for autistic individuals, and later, Schawlow put together an institution to care for people with autism in Paradise, California. It was later named the Arthur Schawlow Center in 1999, shortly before his death. Schawlow was a promoter of the controversial method of facilitated communication with patients of autism.

He considered himself to be an orthodox Protestant Christian, and attended a Methodist church. Arthur Schawlow was an intense fan and collector of traditional American jazz recordings, as well as a supporter of instrumental groups performing this type of music.

Schawlow died of leukemia in Palo Alto, California, on April 28, 1999, at the age 77.

Additional Information

Electrons in atoms and molecules have fixed energy levels, according to the principles of quantum physics. When there are transitions among different energy levels, light with certain frequencies is emitted or absorbed. This allows atoms and molecules to be analyzed with the help of the absorbed light’s spectrum. With the laser’s coherent and intense light, the measurement phenomenon can occur. In the 1960s, Arthur Schawlow made use of this to eliminate the Doppler effect, allowing him to determine energy levels with great precision.

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#4 Jokes » Carrot Jokes - IV » Yesterday 18:15:38

Jai Ganesh
Replies: 0

Q: Why did the Ukrainian turn his carrot around?
A: He wanted to start the orange revolution!
* * *
Q: What did the rabbit say to the carrot?
A: It's been nice gnawing you.
* * *
Q: What's a vegetable's favourite casino game?
A: Baccarrot!
* * *
Q: What does the Carrot priest say at church?
A: "Lettuce Pray".
* * *
Q: What's orange and never shuts up?
A: A carrot reading the bible!
* * *

#5 Dark Discussions at Cafe Infinity » Chair Quotes - I » Yesterday 18:03:52

Jai Ganesh
Replies: 0

Chair Quotes - I

1. Worrying is like a rocking chair, it gives you something to do, but it gets you nowhere. - Glenn Turner

2. If it's the right chair, it doesn't take too long to get comfortable in it. - Robert De Niro

3. The discontented man finds no easy chair. - Benjamin Franklin

4. A table, a chair, a bowl of fruit and a violin; what else does a man need to be happy? - Albert Einstein

5. When I was in junior high school, the teachers voted me the student most likely to end up in the electric chair. - Sylvester Stallone

6. It is totally different making films in the East than in the West. In the East, I make my own Jackie Chan films, and it's like my family. Sometimes I pick up the camera because I choreograph all the fighting scenes, even when I'm not fighting. I don't have my own chair. I just sit on the set with everybody. - Jackie Chan

7. I have always thought it a great privilege to have as my colleague in the Palit Chair of Chemistry such a distinguished pioneer in scientific research and education in Bengal as Sir Prafulla Ray. It has been invariably my experience that I could count on his cooperation and sympathy in every matter concerning my scientific work. - C. V. Raman

8. In 1979, just after I became governor, I asked Hillary to chair a rural health committee to help expand health care to isolated farm and mountain areas. They recommended to do that partly by deploying trained nurse practitioners in places with no doctors to provide primary care they were trained to provide. - William J. Clinton

9. When I received my first paycheck from my now known day job, I spent it on a period Craftsman chair and a Frank Lloyd Wright-wannabe lamp. With my second paycheck, I bought a stereo. - Brad Pitt

10. If you really want to torture me, sit me in a room strapped to a chair and put Mariah Carey's records on. - Cameron Diaz

11. This is a very superficial job. I sit in a chair for two hours and get hair and makeup done and talk about myself in interviews. That's a very vain thing to do. And I do get caught up in it sometimes. - Selena Gomez

12. When I hear something that comes from me that makes me fall down off my chair, it's not often. - Celine Dion.

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#8 Re: Jai Ganesh's Puzzles » Doc, Doc! » Yesterday 16:23:25

Hi,

#2537. What does the medical term Skin grafting mean?

#9 Re: Jai Ganesh's Puzzles » General Quiz » Yesterday 16:06:00

Hi,

#9729. What does the term in Chemistry Surfactants mean?

#9730. What does the term in Chemistry Substitution reaction mean?

#10 Re: Jai Ganesh's Puzzles » English language puzzles » Yesterday 15:34:31

Hi,

#5713. What does the verb (used with object) condone mean?

#5714. What does the noun confectionary mean?

#12 This is Cool » Blue Green Algae » Yesterday 00:38:20

Jai Ganesh
Replies: 0

Blue Green Algae

Gist

Cyanobacteria, formerly known as blue-green algae, are photosynthetic microscopic organisms that are technically bacteria. They were originally called blue-green algae because dense growths often turn the water green, blue-green or brownish-green. These algae are found in all lakes and are a natural part of the lake ecosystem. Unfortunately, high nutrient concentrations can promote a population explosion of these organisms and result in algal blooms, especially during warm weather.

Summary

Blue-green algae are any of a large, heterogeneous group of prokaryotic, principally photosynthetic organisms. Cyanobacteria resemble the eukaryotic algae in many ways, including morphological characteristics and ecological niches, and were at one time treated as algae, hence the common name of blue-green algae. Algae have since been reclassified as protists, and the prokaryotic nature of the blue-green algae has caused them to be classified with bacteria in the prokaryotic kingdom Monera.

Like all other prokaryotes, cyanobacteria lack a membrane-bound nucleus, mitochondria, Golgi apparatus, chloroplasts, and endoplasmic reticulum. All of the functions carried out in eukaryotes by these membrane-bound organelles are carried out in prokaryotes by the bacterial cell membrane. Some cyanobacteria, especially planktonic forms, have gas vesicles that contribute to their buoyancy. Chemical, genetic, and physiological characteristics are used to further classify the group within the kingdom. Cyanobacteria may be unicellular or filamentous. Many have sheaths to bind other cells or filaments into colonies.

Cyanobacteria contain only one form of chlorophyll, chlorophyll a, a green pigment. In addition, they contain various yellowish carotenoids, the blue pigment phycobilin, and, in some species, the red pigment phycoerythrin. The combination of phycobilin and chlorophyll produces the characteristic blue-green colour from which these organisms derive their popular name. Because of the other pigments, however, many species are actually green, brown, yellow, black, or red.

Most cyanobacteria do not grow in the absence of light (i.e., they are obligate phototrophs); however, some can grow in the dark if there is a sufficient supply of glucose to act as a carbon and energy source.

In addition to being photosynthetic, many species of cyanobacteria can also “fix” atmospheric nitrogen—that is, they can transform the gaseous nitrogen of the air into compounds that can be used by living cells. Particularly efficient nitrogen fixers are found among the filamentous species that have specialized cells called heterocysts. The heterocysts are thick-walled cell inclusions that are impermeable to oxygen; they provide the anaerobic (oxygen-free) environment necessary for the operation of the nitrogen-fixing enzymes. In Southeast Asia, nitrogen-fixing cyanobacteria often are grown in rice paddies, thereby eliminating the need to apply nitrogen fertilizers.

Cyanobacteria range in size from 0.5 to 60 micrometres, which represents the largest prokaryotic organism. They are widely distributed and are extremely common in fresh water, where they occur as members of both the plankton and the benthos. They are also abundantly represented in such habitats as tide pools, coral reefs, and tidal spray zones; a few species also occur in the ocean plankton. On land, cyanobacteria are common in soil down to a depth of 1 m (39 inches) or more; they also grow on moist surfaces of rocks and trees, where they appear in the form of cushions or layers.

Cyanobacteria flourish in some of the most inhospitable environments known. They can be found in hot springs, in cold lakes underneath 5 m of ice pack, and on the lower surfaces of many rocks in deserts. Cyanobacteria are frequently among the first colonizers of bare rock and soil. Various types of associations take place between cyanobacteria and other organisms. Certain species, for example, grow in a mutualistic relationship with fungi, forming composite organisms known as lichens.

Cyanobacteria reproduce asexually, either by means of binary or multiple fission in unicellular and colonial forms or by fragmentation and spore formation in filamentous species. Under favourable conditions, cyanobacteria can reproduce at explosive rates, forming dense concentrations called blooms. Cyanobacteria blooms can colour a body of water. For example, many ponds take on an opaque shade of green as a result of overgrowths of cyanobacteria, and blooms of phycoerythrin-rich species cause the occasional red colour of the Red Sea. Cyanobacteria blooms are especially common in waters that have been polluted by nitrogen wastes; in such cases, the overgrowths of cyanobacteria can consume so much of the water’s dissolved oxygen that fish and other aquatic organisms perish.

Details

Cyanobacteria, also called Cyanobacteriota or Cyanophyta, are a phylum of autotrophic gram-negative bacteria that can obtain biological energy via photosynthesis. The name 'cyanobacteria' refers to their color (from Ancient Greek 'blue'), which similarly forms the basis of cyanobacteria's common name, blue-green algae, although they are not scientifically classified as algae. They appear to have originated in a freshwater or terrestrial environment.

Cyanobacteria are probably the most numerous taxon to have ever existed on Earth and the first organisms known to have produced oxygen. By producing and releasing oxygen as a byproduct of photosynthesis, cyanobacteria are thought to have converted the early oxygen-poor, reducing atmosphere into an oxidizing one, causing the Great Oxidation Event and the "rusting of the Earth", which dramatically changed the composition of life forms on Earth.

Cyanobacteria use photosynthetic pigments, such as various forms of chlorophyll, carotenoids, phycobilins to convert the energy in sunlight to chemical energy. Unlike heterotrophic prokaryotes, cyanobacteria have internal membranes. These are flattened sacs called thylakoids where photosynthesis is performed. Phototrophic eukaryotes such as green plants perform photosynthesis in plastids that are thought to have their ancestry in cyanobacteria, acquired long ago via a process called endosymbiosis. These endosymbiotic cyanobacteria in eukaryotes then evolved and differentiated into specialized organelles such as chloroplasts, chromoplasts, etioplasts, and leucoplasts, collectively known as plastids.

Sericytochromatia, the proposed name of the paraphyletic and most basal group, is the ancestor of both the non-photosynthetic group Melainabacteria and the photosynthetic cyanobacteria, also called Oxyphotobacteria.

The cyanobacteria Synechocystis and Cyanothece are important model organisms with potential applications in biotechnology for bioethanol production, food colorings, as a source of human and animal food, dietary supplements and raw materials. Cyanobacteria produce a range of toxins known as cyanotoxins that can cause harmful health effects in humans and animals.

Overview

* Cyanobacteria are found almost everywhere. Sea spray containing marine microorganisms, including cyanobacteria, can be swept high into the atmosphere where they become aeroplankton, and can travel the globe before falling back to earth.
* Cyanobacteria are a very large and diverse phylum of photosynthetic prokaryotes. They are defined by their unique combination of pigments and their ability to perform oxygenic photosynthesis. They often live in colonial aggregates that can take on a multitude of forms. Of particular interest are the filamentous species, which often dominate the upper layers of microbial mats found in extreme environments such as hot springs, hypersaline water, deserts and the polar regions, but are also widely distributed in more mundane environments as well. They are evolutionarily optimized for environmental conditions of low oxygen. Some species are nitrogen-fixing and live in a wide variety of moist soils and water, either freely or in a symbiotic relationship with plants or lichen-forming fungi (as in the lichen genus Peltigera).

Cyanobacteria are globally widespread photosynthetic prokaryotes and are major contributors to global biogeochemical cycles. They are the only oxygenic photosynthetic prokaryotes, and prosper in diverse and extreme habitats. They are among the oldest organisms on Earth with fossil records dating back at least 2.1 billion years. Since then, cyanobacteria have been essential players in the Earth's ecosystems. Planktonic cyanobacteria are a fundamental component of marine food webs and are major contributors to global carbon and nitrogen fluxes. Some cyanobacteria form harmful algal blooms causing the disruption of aquatic ecosystem services and intoxication of wildlife and humans by the production of powerful toxins (cyanotoxins) such as microcystins, saxitoxin, and cylindrospermopsin. Nowadays, cyanobacterial blooms pose a serious threat to aquatic environments and public health, and are increasing in frequency and magnitude globally.

Cyanobacteria are ubiquitous in marine environments and play important roles as primary producers. They are part of the marine phytoplankton, which currently contributes almost half of the Earth's total primary production. About 25% of the global marine primary production is contributed by cyanobacteria.

Within the cyanobacteria, only a few lineages colonized the open ocean: Crocosphaera and relatives, cyanobacterium UCYN-A, Trichodesmium, as well as Prochlorococcus and Synechococcus. From these lineages, nitrogen-fixing cyanobacteria are particularly important because they exert a control on primary productivity and the export of organic carbon to the deep ocean, by converting nitrogen gas into ammonium, which is later used to make amino acids and proteins. Marine picocyanobacteria (Prochlorococcus and Synechococcus) numerically dominate most phytoplankton assemblages in modern oceans, contributing importantly to primary productivity. While some planktonic cyanobacteria are unicellular and free living cells (e.g., Crocosphaera, Prochlorococcus, Synechococcus); others have established symbiotic relationships with haptophyte algae, such as coccolithophores. Amongst the filamentous forms, Trichodesmium are free-living and form aggregates. However, filamentous heterocyst-forming cyanobacteria (e.g., Richelia, Calothrix) are found in association with diatoms such as Hemiaulus, Rhizosolenia and Chaetoceros.

Marine cyanobacteria include the smallest known photosynthetic organisms. The smallest of all, Prochlorococcus, is just 0.5 to 0.8 micrometres across. In terms of numbers of individuals, Prochlorococcus is possibly the most plentiful genus on Earth: a single millilitre of surface seawater can contain 100,000 cells of this genus or more. Worldwide there are estimated to be several octillion ({10}^{27}, a billion billion billion) individuals. Prochlorococcus is ubiquitous between latitudes 40°N and 40°S, and dominates in the oligotrophic (nutrient-poor) regions of the oceans. The bacterium accounts for about 20% of the oxygen in the Earth's atmosphere.

Morphology

Cyanobacteria are variable in morphology, ranging from unicellular and filamentous to colonial forms. Filamentous forms exhibit functional cell differentiation such as heterocysts (for nitrogen fixation), akinetes (resting stage cells), and hormogonia (reproductive, motile filaments). These, together with the intercellular connections they possess, are considered the first signs of multicellularity.

Many cyanobacteria form motile filaments of cells, called hormogonia, that travel away from the main biomass to bud and form new colonies elsewhere. The cells in a hormogonium are often thinner than in the vegetative state, and the cells on either end of the motile chain may be tapered. To break away from the parent colony, a hormogonium often must tear apart a weaker cell in a filament, called a necridium.

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#13 Re: This is Cool » Miscellany » Yesterday 00:02:51

2105) Anatomy

Gist

The study of the structure of a plant or animal. Human anatomy includes the cells, tissues, and organs that make up the body and how they are organized in the body.

Summary

Anatomy is the study of the structure of living things – animal, human, plant – from microscopic cells and molecules to whole organisms as large as whales.

Anatomy Is Everywhere

* Anthropologists study cultures around the world.
* Paleontologists use cutting-edge technology to discover the ancient world.
* Archeologists uncover our history one artifact at a time.
* Veterinarians help humans care for pets and farm animals.
* Zoologists ensure captive animals – from backyard critters to endangered species – receive optimal care.
* Medical students learn anatomy before becoming nurses, doctors, and dentists.
* Inventors create exoskeletons to give people mobility.
* Biomedical engineers create better pacemakers and prosthetics.
* Physical therapists find remedies for their patients’ challenges.

Who Are Anatomists?

An anatomist broadly describes someone who studies, researches, or teaches in the anatomical sciences, including the study of extinct species, such as dinosaurs and Neanderthals. They help us understand how things are formed and constructed, which has enormous impact. However, not everyone who studies, applies, or researches anatomy calls themselves ‘anatomists.’

WHAT ANATOMISTS DO

Anatomists work with students and researchers to better understand humans and animals, in order to teach the next generation of doctors, nurses, physical therapists, dentists, and veterinarians. Their research into cell and molecular anatomy means that conditions such as cleft palate, congenital heart defects, neurological disorders, and cancer biology are better understood – and can be treated.

WHERE ANATOMISTS WORK

Anatomists work in universities, research institutions, and private industry. They teach anatomy in medical, dental, and veterinary schools, as well as at large undergraduate universities. They run their own research labs at organizations and universities, and they work together in teams of scientists, postdoctoral researchers, and students to uncover discoveries that lead to better understanding of our biology.

Details

Anatomy (from Ancient Greek anatomḗ) 'dissection') is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having its beginnings in prehistoric times. Anatomy is inherently tied to developmental biology, embryology, comparative anatomy, evolutionary biology, and phylogeny, as these are the processes by which anatomy is generated, both over immediate and long-term timescales. Anatomy and physiology, which study the structure and function of organisms and their parts respectively, make a natural pair of related disciplines, and are often studied together. Human anatomy is one of the essential basic sciences that are applied in medicine, and is often studied alongside physiology.

Anatomy is a complex and dynamic field that is constantly evolving as new discoveries are made. In recent years, there has been a significant increase in the use of advanced imaging techniques, such as MRI and CT scans, which allow for more detailed and accurate visualizations of the body's structures.

The discipline of anatomy is divided into macroscopic and microscopic parts. Macroscopic anatomy, or gross anatomy, is the examination of an animal's body parts using unaided eyesight. Gross anatomy also includes the branch of superficial anatomy. Microscopic anatomy involves the use of optical instruments in the study of the tissues of various structures, known as histology, and also in the study of cells.

The history of anatomy is characterized by a progressive understanding of the functions of the organs and structures of the human body. Methods have also improved dramatically, advancing from the examination of animals by dissection of carcasses and cadavers (corpses) to 20th-century medical imaging techniques, including X-ray, ultrasound, and magnetic resonance imaging.

Etymology and definition

Derived from the Greek "dissection" (from "I cut up, cut open" from "up", and "I cut"), anatomy is the scientific study of the structure of organisms including their systems, organs and tissues. It includes the appearance and position of the various parts, the materials from which they are composed, and their relationships with other parts. Anatomy is quite distinct from physiology and biochemistry, which deal respectively with the functions of those parts and the chemical processes involved. For example, an anatomist is concerned with the shape, size, position, structure, blood supply and innervation of an organ such as the liver; while a physiologist is interested in the production of bile, the role of the liver in nutrition and the regulation of bodily functions.

The discipline of anatomy can be subdivided into a number of branches, including gross or macroscopic anatomy and microscopic anatomy. Gross anatomy is the study of structures large enough to be seen with the naked eye, and also includes superficial anatomy or surface anatomy, the study by sight of the external body features. Microscopic anatomy is the study of structures on a microscopic scale, along with histology (the study of tissues), and embryology (the study of an organism in its immature condition). Regional anatomy is the study of the interrelationships of all of the structures in a specific body region, such as the abdomen. In contrast, systemic anatomy is the study of the structures that make up a discrete body system—that is, a group of structures that work together to perform a unique body function, such as the digestive system.

Anatomy can be studied using both invasive and non-invasive methods with the goal of obtaining information about the structure and organization of organs and systems. Methods used include dissection, in which a body is opened and its organs studied, and endoscopy, in which a video camera-equipped instrument is inserted through a small incision in the body wall and used to explore the internal organs and other structures. Angiography using X-rays or magnetic resonance angiography are methods to visualize blood vessels.

The term "anatomy" is commonly taken to refer to human anatomy. However, substantially similar structures and tissues are found throughout the rest of the animal kingdom, and the term also includes the anatomy of other animals. The term zootomy is also sometimes used to specifically refer to non-human animals. The structure and tissues of plants are of a dissimilar nature and they are studied in plant anatomy.

Animal tissues

The kingdom Animalia contains multicellular organisms that are heterotrophic and motile (although some have secondarily adopted a sessile lifestyle). Most animals have bodies differentiated into separate tissues and these animals are also known as eumetazoans. They have an internal digestive chamber, with one or two openings; the gametes are produced in multicellular gender organs, and the zygotes include a blastula stage in their embryonic development. Metazoans do not include the sponges, which have undifferentiated cells.

Unlike plant cells, animal cells have neither a cell wall nor chloroplasts. Vacuoles, when present, are more in number and much smaller than those in the plant cell. The body tissues are composed of numerous types of cells, including those found in muscles, nerves and skin. Each typically has a cell membrane formed of phospholipids, cytoplasm and a nucleus. All of the different cells of an animal are derived from the embryonic germ layers. Those simpler invertebrates which are formed from two germ layers of ectoderm and endoderm are called diploblastic and the more developed animals whose structures and organs are formed from three germ layers are called triploblastic. All of a triploblastic animal's tissues and organs are derived from the three germ layers of the embryo, the ectoderm, mesoderm and endoderm.

Animal tissues can be grouped into four basic types: connective, epithelial, muscle and nervous tissue.

Connective tissue

Connective tissues are fibrous and made up of cells scattered among inorganic material called the extracellular matrix. Connective tissue gives shape to organs and holds them in place. The main types are loose connective tissue, adipose tissue, fibrous connective tissue, cartilage and bone. The extracellular matrix contains proteins, the chief and most abundant of which is collagen. Collagen plays a major part in organizing and maintaining tissues. The matrix can be modified to form a skeleton to support or protect the body. An exoskeleton is a thickened, rigid cuticle which is stiffened by mineralization, as in crustaceans or by the cross-linking of its proteins as in insects. An endoskeleton is internal and present in all developed animals, as well as in many of those less developed.[16]

Epithelium

Epithelial tissue is composed of closely packed cells, bound to each other by cell adhesion molecules, with little intercellular space. Epithelial cells can be squamous (flat), cuboidal or columnar and rest on a basal lamina, the upper layer of the basement membrane, the lower layer is the reticular lamina lying next to the connective tissue in the extracellular matrix secreted by the epithelial cells. There are many different types of epithelium, modified to suit a particular function. In the respiratory tract there is a type of ciliated epithelial lining; in the small intestine there are microvilli on the epithelial lining and in the large intestine there are intestinal villi. Skin consists of an outer layer of keratinized stratified squamous epithelium that covers the exterior of the vertebrate body. Keratinocytes make up to 95% of the cells in the skin. The epithelial cells on the external surface of the body typically secrete an extracellular matrix in the form of a cuticle. In simple animals this may just be a coat of glycoproteins. In more advanced animals, many glands are formed of epithelial cells.

Muscle tissue

Muscle cells (myocytes) form the active contractile tissue of the body. Muscle tissue functions to produce force and cause motion, either locomotion or movement within internal organs. Muscle is formed of contractile filaments and is separated into three main types; smooth muscle, skeletal muscle and cardiac muscle. Smooth muscle has no striations when examined microscopically. It contracts slowly but maintains contractibility over a wide range of stretch lengths. It is found in such organs as sea anemone tentacles and the body wall of sea cucumbers. Skeletal muscle contracts rapidly but has a limited range of extension. It is found in the movement of appendages and jaws. Obliquely striated muscle is intermediate between the other two. The filaments are staggered and this is the type of muscle found in earthworms that can extend slowly or make rapid contractions. In higher animals striated muscles occur in bundles attached to bone to provide movement and are often arranged in antagonistic sets. Smooth muscle is found in the walls of the uterus, bladder, intestines, stomach, oesophagus, respiratory airways, and blood vessels. Cardiac muscle is found only in the heart, allowing it to contract and pump blood round the body.

Nervous tissue

Nervous tissue is composed of many nerve cells known as neurons which transmit information. In some slow-moving radially symmetrical marine animals such as ctenophores and cnidarians (including sea anemones and jellyfish), the nerves form a nerve net, but in most animals they are organized longitudinally into bundles. In simple animals, receptor neurons in the body wall cause a local reaction to a stimulus. In more complex animals, specialized receptor cells such as chemoreceptors and photoreceptors are found in groups and send messages along neural networks to other parts of the organism. Neurons can be connected together in ganglia. In higher animals, specialized receptors are the basis of sense organs and there is a central nervous system (brain and spinal cord) and a peripheral nervous system. The latter consists of sensory nerves that transmit information from sense organs and motor nerves that influence target organs. The peripheral nervous system is divided into the somatic nervous system which conveys sensation and controls voluntary muscle, and the autonomic nervous system which involuntarily controls smooth muscle, certain glands and internal organs, including the stomach.

Vertebrate anatomy

All vertebrates have a similar basic body plan and at some point in their lives, mostly in the embryonic stage, share the major chordate characteristics: a stiffening rod, the notochord; a dorsal hollow tube of nervous material, the neural tube; pharyngeal arches; and a tail posterior to the math. The spinal cord is protected by the vertebral column and is above the notochord, and the gastrointestinal tract is below it. Nervous tissue is derived from the ectoderm, connective tissues are derived from mesoderm, and gut is derived from the endoderm. At the posterior end is a tail which continues the spinal cord and vertebrae but not the gut. The mouth is found at the anterior end of the animal, and the math at the base of the tail. The defining characteristic of a vertebrate is the vertebral column, formed in the development of the segmented series of vertebrae. In most vertebrates the notochord becomes the nucleus pulposus of the intervertebral discs. However, a few vertebrates, such as the sturgeon and the coelacanth, retain the notochord into adulthood. Jawed vertebrates are typified by paired appendages, fins or legs, which may be secondarily lost. The limbs of vertebrates are considered to be homologous because the same underlying skeletal structure was inherited from their last common ancestor. This is one of the arguments put forward by Charles Darwin to support his theory of evolution.

Mammal anatomy

Mammals are a diverse class of animals, mostly terrestrial but some are aquatic and others have evolved flapping or gliding flight. They mostly have four limbs, but some aquatic mammals have no limbs or limbs modified into fins, and the forelimbs of bats are modified into wings. The legs of most mammals are situated below the trunk, which is held well clear of the ground. The bones of mammals are well ossified and their teeth, which are usually differentiated, are coated in a layer of prismatic enamel. The teeth are shed once (milk teeth) during the animal's lifetime or not at all, as is the case in cetaceans. Mammals have three bones in the middle ear and a cochlea in the inner ear. They are clothed in hair and their skin contains glands which secrete sweat. Some of these glands are specialized as mammary glands, producing milk to feed the young. Mammals breathe with lungs and have a muscular diaphragm separating the thorax from the abdomen which helps them draw air into the lungs. The mammalian heart has four chambers, and oxygenated and deoxygenated blood are kept entirely separate. Nitrogenous waste is excreted primarily as urea.

Mammals are amniotes, and most are viviparous, giving birth to live young. Exceptions to this are the egg-laying monotremes, the platypus and the echidnas of Australia. Most other mammals have a placenta through which the developing foetus obtains nourishment, but in marsupials, the foetal stage is very short and the immature young is born and finds its way to its mother's pouch where it latches on to a nipple and completes its development.

Human anatomy

In humans, dexterous hand movements and increased brain size are likely to have evolved simultaneously.
Humans have the overall body plan of a mammal. Humans have a head, neck, trunk (which includes the thorax and abdomen), two arms and hands, and two legs and feet.

Generally, students of certain biological sciences, paramedics, prosthetists and orthotists, physiotherapists, occupational therapists, nurses, podiatrists, and medical students learn gross anatomy and microscopic anatomy from anatomical models, skeletons, textbooks, diagrams, photographs, lectures and tutorials and in addition, medical students generally also learn gross anatomy through practical experience of dissection and inspection of cadavers. The study of microscopic anatomy (or histology) can be aided by practical experience examining histological preparations (or slides) under a microscope.

Human anatomy, physiology and biochemistry are complementary basic medical sciences, which are generally taught to medical students in their first year at medical school. Human anatomy can be taught regionally or systemically; that is, respectively, studying anatomy by bodily regions such as the head and chest, or studying by specific systems, such as the nervous or respiratory systems. The major anatomy textbook, Gray's Anatomy, has been reorganized from a systems format to a regional format, in line with modern teaching methods. A thorough working knowledge of anatomy is required by physicians, especially surgeons and doctors working in some diagnostic specialties, such as histopathology and radiology.

Academic anatomists are usually employed by universities, medical schools or teaching hospitals. They are often involved in teaching anatomy, and research into certain systems, organs, tissues or cells.

Additional Information

Anatomy is a field in the biological sciences concerned with the identification and description of the body structures of living things. Gross anatomy involves the study of major body structures by dissection and observation and in its narrowest sense is concerned only with the human body. “Gross anatomy” customarily refers to the study of those body structures large enough to be examined without the help of magnifying devices, while microscopic anatomy is concerned with the study of structural units small enough to be seen only with a light microscope. Dissection is basic to all anatomical research. The earliest record of its use was made by the Greeks, and Theophrastus called dissection “anatomy,” from ana temnein, meaning “to cut up.”

Comparative anatomy, the other major subdivision of the field, compares similar body structures in different species of animals in order to understand the adaptive changes they have undergone in the course of evolution.

Gross anatomy

This ancient discipline reached its culmination between 1500 and 1850, by which time its subject matter was firmly established. None of the world’s oldest civilizations dissected a human body, which most people regarded with superstitious awe and associated with the spirit of the departed soul. Beliefs in life after death and a disquieting uncertainty concerning the possibility of bodily resurrection further inhibited systematic study. Nevertheless, knowledge of the body was acquired by treating wounds, aiding in childbirth, and setting broken limbs. The field remained speculative rather than descriptive, though, until the achievements of the Alexandrian medical school and its foremost figure, Herophilus (flourished 300 BCE), who dissected human cadavers and thus gave anatomy a considerable factual basis for the first time. Herophilus made many important discoveries and was followed by his younger contemporary Erasistratus, who is sometimes regarded as the founder of physiology. In the 2nd century CE, Greek physician Galen assembled and arranged all the discoveries of the Greek anatomists, including with them his own concepts of physiology and his discoveries in experimental medicine. The many books Galen wrote became the unquestioned authority for anatomy and medicine in Europe because they were the only ancient Greek anatomical texts that survived the Dark Ages in the form of Arabic (and then Latin) translations.

Owing to church prohibitions against dissection, European medicine in the Middle Ages relied upon Galen’s mixture of fact and fancy rather than on direct observation for its anatomical knowledge, though some dissections were authorized for teaching purposes. In the early 16th century, the artist Leonardo da Vinci undertook his own dissections, and his beautiful and accurate anatomical drawings cleared the way for Flemish physician Andreas Vesalius to “restore” the science of anatomy with his monumental De humani corporis fabrica libri septem (1543; “The Seven Books on the Structure of the Human Body”), which was the first comprehensive and illustrated textbook of anatomy. As a professor at the University of Padua, Vesalius encouraged younger scientists to accept traditional anatomy only after verifying it themselves, and this more critical and questioning attitude broke Galen’s authority and placed anatomy on a firm foundation of observed fact and demonstration.

From Vesalius’s exact descriptions of the skeleton, muscles, blood vessels, nervous system, and digestive tract, his successors in Padua progressed to studies of the digestive glands and the urinary and reproductive systems. Hieronymus Fabricius, Gabriello Fallopius, and Bartolomeo Eustachio were among the most important Italian anatomists, and their detailed studies led to fundamental progress in the related field of physiology. William Harvey’s discovery of the circulation of the blood, for instance, was based partly on Fabricius’s detailed descriptions of the venous valves.

Microscopic anatomy

The new application of magnifying glasses and compound microscopes to biological studies in the second half of the 17th century was the most important factor in the subsequent development of anatomical research. Primitive early microscopes enabled Marcello Malpighi to discover the system of tiny capillaries connecting the arterial and venous networks, Robert Hooke to first observe the small compartments in plants that he called “cells,” and Antonie van Leeuwenhoek to observe muscle fibres and spermatozoa. Thenceforth attention gradually shifted from the identification and understanding of bodily structures visible to the naked eye to those of microscopic size.

The use of the microscope in discovering minute, previously unknown features was pursued on a more systematic basis in the 18th century, but progress tended to be slow until technical improvements in the compound microscope itself, beginning in the 1830s with the gradual development of achromatic lenses, greatly increased that instrument’s resolving power. These technical advances enabled Matthias Jakob Schleiden and Theodor Schwann to recognize in 1838–39 that the cell is the fundamental unit of organization in all living things. The need for thinner, more transparent tissue specimens for study under the light microscope stimulated the development of improved methods of dissection, notably machines called microtomes that can slice specimens into extremely thin sections. In order to better distinguish the detail in these sections, synthetic dyes were used to stain tissues with different colours. Thin sections and staining had become standard tools for microscopic anatomists by the late 19th century. The field of cytology, which is the study of cells, and that of histology, which is the study of tissue organization from the cellular level up, both arose in the 19th century with the data and techniques of microscopic anatomy as their basis.

In the 20th century anatomists tended to scrutinize tinier and tinier units of structure as new technologies enabled them to discern details far beyond the limits of resolution of light microscopes. These advances were made possible by the electron microscope, which stimulated an enormous amount of research on subcellular structures beginning in the 1950s and became the prime tool of anatomical research. About the same time, the use of X-ray diffraction for studying the structures of many types of molecules present in living things gave rise to the new subspecialty of molecular anatomy.

Anatomical nomenclature

Scientific names for the parts and structures of the human body are usually in Latin; for example, the name musculus biceps brachii denotes the biceps muscle of the upper arm. Some such names were bequeathed to Europe by ancient Greek and Roman writers, and many more were coined by European anatomists from the 16th century on. Expanding medical knowledge meant the discovery of many bodily structures and tissues, but there was no uniformity of nomenclature, and thousands of new names were added as medical writers followed their own fancies, usually expressing them in a Latin form.

By the end of the 19th century the confusion caused by the enormous number of names had become intolerable. Medical dictionaries sometimes listed as many as 20 synonyms for one name, and more than 50,000 names were in use throughout Europe. In 1887 the German Anatomical Society undertook the task of standardizing the nomenclature, and, with the help of other national anatomical societies, a complete list of anatomical terms and names was approved in 1895 that reduced the 50,000 names to 5,528. This list, the Basle Nomina Anatomica, had to be subsequently expanded, and in 1955 the Sixth International Anatomical Congress at Paris approved a major revision of it known as the Paris Nomina Anatomica (or simply Nomina Anatomica). In 1998 this work was supplanted by the Terminologia Anatomica, which recognizes about 7,500 terms describing macroscopic structures of human anatomy and is considered to be the international standard on human anatomical nomenclature. The Terminologia Anatomica, produced by the International Federation of Associations of Anatomists and the Federative Committee on Anatomical Terminology (later known as the Federative International Programme on Anatomical Terminologies), was made available online in 2011.

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#15 Jokes » Carrot Jokes - III » 2024-03-26 18:38:20

Jai Ganesh
Replies: 0

Q: What did one snowman say to the other?
A: Does it smell like carrots?
* * *
Q: How do you make gold soup?
A: Put 24 carrots in it.
* * *
Q: What did the carrot say to the rabbit?
A: Do you want to grab a bite?
* * *
Q: What kind of vegetable watches over the elderly?
A: The Carrot-aker.
* * *
Q: What do you call a vegetable with a sense of humor?
A: Carrot Top.
* * *

#16 Dark Discussions at Cafe Infinity » Chain Jokes - II » 2024-03-26 18:29:07

Jai Ganesh
Replies: 0

Chain Jokes - II

1. I'm very intelligent. I'm capable of doing everything put to me. I've launched a perfume and want my own hotel chain. I'm living proof blondes are not stupid. - Paris Hilton

2. The ideal reasoner, he remarked, would, when he had once been shown a single fact in all its bearings, deduce from it not only all the chain of events which led up to it but also all the results which would follow from it. - Arthur Conan Doyle

3. I always had boyfriends, but I never imagined a proposal or a wedding. To me, that was like having a ball and chain round your neck. - Sandra Bullock

4. The most interesting biofuel efforts avoid using land that's expensive and has high opportunity costs. They do this by getting onto other types of land, or taking advantage of byproducts that aren't used in the food chain today, or by intercropping. - Bill Gates

5. If I send out positive messages, it will set a chain of healthy thought processes. - Persis Khambatta

6. The economic situation, the high cost of undertaking manufacturing, the supply chain - which is, by the way, dying out also as manufacturing undergoes hardship - make the U.K. not the first place you would look at to make a manufacturing investment. - Ratan Tata

7. We have only one Windows. We don't have multiple Windows. They run across multiple form factors, but it's one developer platform, one store, one tool chain for developers. And you adapt it for different screen sizes and different input and output. - Satya Nadella

8. I became more part of the industry after quitting acting. I contribute greatly to the industry, as I bring in talent, provide money in the chain, and make it happen. - Pooja Bhatt

9. Olympic Style lifting compliments sprint training perfectly. It does this by making sure everything in the body is 'fully connected.' This is based on the principle that all movements have a kinetic chain. - Linford Christie

10. Many times people tried to convince me about Ahimsa silk, but when I followed the chain of production it always ended with genetically modified silk moths that could not fly. There was nothing Ahimsa about it. - Amala Akkineni

11. That's the food chain that cricket is sometimes. You have to be at the top of it otherwise you get swept away and eaten up. - Joe Root.

image_54680d66-3b4a-4ad8-82f0-f1c80123389d_1024x1024.jpg?v=1681799973

#19 Re: Jai Ganesh's Puzzles » Doc, Doc! » 2024-03-26 16:54:29

Hi,

#2536. What does the medical term Polysome mean?

#20 Re: Jai Ganesh's Puzzles » General Quiz » 2024-03-26 16:44:00

Hi,

#9727. What does the term in Geography Wave-cut platform mean?

#9728. What does the term in Geography Waterway mean?

#21 Re: Jai Ganesh's Puzzles » English language puzzles » 2024-03-26 15:45:19

Hi,

#5711. What does the noun edict mean?

#5712. What does the noun edifice mean?

#23 This is Cool » Tremor » 2024-03-26 14:53:09

Jai Ganesh
Replies: 0

Tremor

Gist

Tremor is a neurological condition that includes shaking or trembling movements in one or more parts of the body, most commonly affecting a person's hands. It can also occur in the arms, legs, head, vocal cords, and torso.

Summary

A tremor is an involuntary, somewhat rhythmic, muscle contraction and relaxation involving oscillations or twitching movements of one or more body parts. It is the most common of all involuntary movements and can affect the hands, arms, eyes, face, head, vocal folds, trunk, and legs. Most tremors occur in the hands. In some people, a tremor is a symptom of another neurological disorder.

Types

Tremor is most commonly classified by clinical features and cause or origin. Some of the better-known forms of tremor, with their symptoms, include the following:

* Cerebellar tremor (also known as intention tremor) is a slow, broad tremor of the extremities that occurs at the end of a purposeful movement, such as trying to press a button or touching a finger to the tip of one's nose. In classic cerebellar tremor, a lesion on one side of the brain produces a tremor in that same side of the body that worsens with directed movement. Cerebellar damage can also produce a "wing-beating" type of tremor called rubral or Holmes' tremor — a combination of rest, action, and postural tremors. The tremor is often most prominent when the affected person is active or is maintaining a particular posture. Cerebellar tremor may be accompanied by other manifestations of ataxia, including dysarthria (speech problems), nystagmus (rapid, involuntary rolling of the eyes), gait problems and postural tremor of the trunk and neck. Titubation is tremor of the head, hands, and torso and is of cerebellar origin.
* Dystonic tremor occurs in individuals of all ages who are affected by dystonia, a movement disorder in which sustained involuntary muscle contractions cause twisting and repetitive motions or painful and abnormal postures or positions. Dystonic tremor may affect any muscle in the body and is seen most often when the patient is in a certain position or moves a certain way. The pattern of dystonic tremor may differ from essential tremor. Dystonic tremors occur irregularly and can often be relieved by complete rest. Touching the affected body part or muscle may reduce tremor severity (a geste antagoniste). The tremor may be the initial sign of dystonia localized to a particular part of the body. The dystonic tremor has usually a frequency of about 7 Hz.
* Essential tremor (sometimes inaccurately called benign essential tremor) is the most common of the more than 20 types of tremor. Although the tremor may be mild and nonprogressive in some people, in others, the tremor is slowly progressive, starting on one side of the body but affecting both sides within 3 years. The hands are most often affected but the head, voice, tongue, legs, and trunk may also be involved. Head tremor may be seen as a vertical or horizontal motion. Essential tremor may be accompanied by mild gait disturbance. Tremor frequency may decrease as the person ages, but the severity may increase, affecting the person's ability to perform certain tasks or activities of daily living. Heightened emotion, stress, fever, physical exhaustion, or low blood sugar may trigger tremors or increase their severity. Onset is most common after age 40, although symptoms can appear at any age. It may occur in more than one family member. Children of a parent who has essential tremor have a 50 percent chance of inheriting the condition. Essential tremor is not associated with any known pathology. Its frequency is between 4 and 8 Hz.
* Orthostatic tremor is characterized by fast (>12 Hz) rhythmic muscle contractions that occur in the legs and trunk immediately after standing up. Cramps are felt in the thighs and legs and the patient may shake uncontrollably when asked to stand in one spot. No other clinical signs or symptoms are present and the shaking ceases when the patient sits or is lifted off the ground. The high frequency of the tremor often makes the tremor look like rippling of leg muscles while standing. Orthostatic tremor may also occur in patients who have essential tremor, and there might be an overlap between these categories of tremor.
* Parkinsonian tremor is caused by damage to structures within the brain that control movement. This resting tremor, which can occur as an isolated symptom or be seen in other disorders, is often a precursor to Parkinson's disease (more than 25 percent of patients with Parkinson's disease have an associated action tremor). The tremor, which is classically seen as a "pill-rolling" action of the hands that may also affect the chin, lips, legs, and trunk, can be markedly increased by stress or emotion. Onset is generally after age 60. Movement starts in one limb or on one side of the body and usually progresses to include the other side. The tremor's frequency is between 4 and 6 Hz.
* Physiological tremor occurs in every normal individual and has no clinical significance. It is rarely visible and may be heightened by strong emotion (such as anxiety or fear), physical exhaustion, hypoglycemia, hyperthyroidism, heavy metal poisoning, stimulants, alcohol withdrawal or fever. It can be seen in all voluntary muscle groups and can be detected by extending the arms and placing a piece of paper on top of the hands. Enhanced physiological tremor is a strengthening of physiological tremor to more visible levels. It is generally not caused by a neurological disease but by reaction to certain drugs, alcohol withdrawal, or medical conditions including an overactive thyroid and hypoglycemia. It is usually reversible once the cause is corrected. This tremor classically has a frequency of about 10 Hz.
* Psychogenic tremor (also called hysterical tremor and functional tremor) can occur at rest or during postural or kinetic movement. The characteristics of this kind of tremor may vary but generally include sudden onset and remission, increased incidence with stress, change in tremor direction or body part affected, and greatly decreased or disappearing tremor activity when the patient is distracted. Many patients with psychogenic tremor have a conversion disorder (see Post traumatic stress disorder) or another psychiatric disease.
* Rubral tremor is characterized by coarse slow tremor which is present at rest, at posture and with intention. This tremor is associated with conditions which affect the red nucleus in the midbrain, classically unusual strokes.
Neuropathic tremor may occur in patients with peripheral neuropathies, when the nerves that supply the body's muscles are traumatized by injury, disease, abnormality in the central nervous system, or as the result of systemic illnesses. It is most commonly observed in patients with an immunoglobulin M paraproteinaemic neuropathy (IgMNP), but also in patients with chronic inflammatory demyelinating polyneuropathy (CIDP). The tremor is predominantely exhibited as an action or postural tremor with a frequency of 3 to 10 Hz. Peripheral neuropathy can affect the whole body or certain areas, such as the hands, and may be progressive. Resulting sensory loss may be seen as a tremor or ataxia (inability to coordinate voluntary muscle movement) of the affected limbs and problems with gait and balance. Clinical characteristics may be similar to those seen in patients with essential tremor.
* Neurogenic tremor is a self-induced tremor that is activated in humans. The mechanism is activated passive supine position, bringing the knees up and splitting them apart. The tremor is akin to the natural shaking mechanism in mammals to discharge stress and trauma.

Tremor can result from other conditions as well

* Alcoholism, excessive alcohol consumption, or alcohol withdrawal can kill certain nerve cells, resulting in a tremor known as asterixis. Conversely, small amounts of alcohol may help to decrease familial and essential tremor, but the mechanism behind it is unknown. Alcohol potentiates GABAergic transmission and might act at the level of the inferior olive.
* Tobacco withdrawal symptoms include tremor.
* Most of the symptoms can also occur randomly when panicked.

Details

Tremor is a neurological condition that includes shaking or trembling movements in one or more parts of the body, most commonly affecting a person’s hands. It can also occur in the arms, legs, head, vocal cords, and torso.  The tremor may be constant, or only happen sometimes. Tremor can occur on its own or as a result of another disorder.

Tremor is not life threatening, but it may cause challenges and even lead to disabilities. Tremor can make daily life tasks such as writing, typing, eating, shaving, and dressing more difficult.

Common symptoms may include:

* Rhythmic shaking of the hands, arms, head, legs, or torso
* Shaky voice
* Difficulty with writing or drawing
* Problems holding and controlling utensils, tools, or other items

Some tremor can be triggered by stress or strong emotion, being physically tired, or being in certain postures or making specific movements.

What are the types of tremor?

Tremor is categorized based on when and how the tremor is activated. These categories are rest and action tremor. Rest tremor occurs when people are at rest. People with Parkinson’s disease often experience rest tremor. Action tremor occurs when a muscle is moved voluntarily. There are several sub-classifications of action tremor, many of which overlap.

* Postural tremor occurs when holding a position against gravity, such as holding the arms outstretched.
* Kinetic tremor is associated with any voluntary movement, such as moving the wrists up and down or closing and opening your eyes.
* Intention tremor starts when the person makes an intended movement toward a target, such as lifting a finger to touch their nose.
* Task-specific tremor only appears when performing goal-oriented tasks such as handwriting or speaking.
* Isometric tremor occurs during a voluntary muscle contraction that is not accompanied by any movement, such as when holding a heavy book in the same position.

Tremor syndromes are defined based on the pattern of the tremor. Some of the most common forms include:

Essential tremor

Essential tremor (previously also called benign essential tremor or familial tremor) is one of the most common movement disorders. Its key feature is a tremor in both hands and arms during action without other neurological signs. It also may affect a person’s head, voice, or lower limbs. Although the tremor can start at any age, it most often first appears during adolescence or in middle age (between ages 40 and 50). It can be mild and stay mild, or slowly get worse over time.

The exact cause of essential tremor is unknown. Studies show essential tremor is accompanied by a mild degeneration of the cerebellum, which is the part of your brain that controls movement coordination. Essential tremor is an inherited condition in 50-70% of cases (referred to as familial tremor). Familial forms often appear early in life. 

Dystonic tremor

Dystonic tremor occurs in people who are affected by dystonia—a movement disorder in which incorrect messages from the brain cause muscles to be overactive, resulting in abnormal postures or sustained, unwanted movements. The disorder usually appears in young or middle-aged adults and can affect any muscle in the body, but most commonly affects the neck (cervical dystonia), vocal cords (laryngeal dystonia), or arms/legs (limb dystonia). A person with dystonic tremor can sometimes relieve their tremor by relaxing completely or touching the affected body part or muscle.

Cerebellar tremor

Cerebellar tremor is typically a slow, big (high amplitude) tremor of the arms, legs, hands, or feet that worsens at the end of a purposeful movement such as pressing a button. It is caused by damage to the cerebellum and its pathways to other brain areas, often from a stroke or tumor, injury from a disease or an inherited disorder, or from chronic damage due to alcohol use disorder. 

Functional tremor

Functional tremor (also called psychogenic tremor) can appear as any form of tremor. Its symptoms may vary but often start suddenly and fluctuate widely. The tremor may increase with attention and decrease or disappear when the person is distracted. 

Enhanced physiologic tremor

Enhanced physiologic tremor typically involves a fine amplitude (small) action tremor in both the hands and the fingers. It is generally not caused by a neurological disease but by reaction to certain drugs, alcohol withdrawal, or medical conditions including an overactive thyroid and hypoglycemia. It is potentially reversible once the cause is corrected.

Parkinsonian tremor

Parkinsonian tremor is common and one of the first signs of Parkinson's disease, although not all people with Parkinson's disease have tremor. Its shaking is most noticeable when the hands are at rest and may look as if someone's trying to roll a pill between the thumb and a finger. Parkinson's tremor may also affect the chin, lips, face, and legs. The tremor may initially appear in only one limb or on just one side of the body but may spread to both sides as the disease progresses. The tremor is often made worse by stress or strong emotions. 

Orthostatic tremor

Orthostatic tremor is a rare disorder characterized by rapid muscle contractions in the legs that occur when a person stands up. The tremor usually stops when the person sits down or walks. Standing may make the person feel unsteady or unbalanced, causing them to try to sit or walk. Because this type of tremor involves very fast shaking, it may not be visible to the naked eye. Orthostatic tremor can be felt by touching the person’s thighs or calves or when a doctor listens to the muscle activities with a stethoscope. In some cases, the tremor can become more severe over time. The cause of orthostatic tremor is unknown.

Who is more likely to get tremor?

Tremor is most common among middle-aged and older adults, although it can occur at any age. Generally, tremor occurs in men and women equally.

Tremor is usually caused by a problem in the parts of the brain that control movements. Most types have no known genetic cause, although there are some forms that appear to be inherited and run in families.

Tremor can occur on its own or be a symptom of other neurological disorders such as Parkinson’s disease, multiple sclerosis, or stroke. Tremor sometimes can be caused by other medical conditions, including but not limited to:

* Medicines. Several drugs can cause tremors, including certain asthma medications, corticosteroids, chemotherapy, and drugs used for certain psychiatric and neurological disorders.
* Heavy metals and other neurotoxins. Exposure to heavy metals (such as mercury, manganese, lead, math, etc.), organic solvents, or pesticides may cause tremors.
* Caffeine. Excessive caffeine may cause temporary tremor or make an existing tremor worse.
* Thyroid disorder. An overactive thyroid can cause tremors.
* Liver or kidney failure. Liver and kidney failure may cause damage in certain brain areas that leads to tremors or jerky movements.
* Diabetes. High or low blood sugar (hyperglycemia or hypoglycemia, respectively) may cause tremors or other involuntary movements.

Stress, anxiety, or fatigue may be associated with tremors.

How is tremor diagnosed and treated?

To diagnose tremor, a doctor will perform a physical exam and review the person’s medical history. They will perform a neurological exam and test muscle tone and strength, reflexes, balance, and speech, and evaluate:

* Whether the tremor occurs when the muscles are at rest or in action
* The location of the tremor in the body (and if it occurs on one or both sides of the body)
* The appearance of the tremor (tremor frequency and amplitude/size)

A doctor may take blood or urine samples to rule out certain contributing factors to the tremor. Diagnostic imaging may help determine if the tremor is the result of damage in the brain. An electromyogram, which measures involuntary muscle activity and muscle response to nerve stimulation, may identify muscle or nerve problems.

Additional tests can help determine any functional limitations such as difficulty with handwriting or the ability to hold a fork or cup.

Treating tremor

Although there is no cure for most forms of tremor, treatments are available to help manage symptoms. In some cases, symptoms may be mild enough that they do not need treatment. Treating any underlying health condition can sometimes cure or reduce a person’s tremor.

Medications

Some medications can slow tremor. Some medications commonly used to treat tremor include:

* Beta-blocking drugs can treat essential tremor and other types of action tremor in some people. 
* Certain anti-seizure medications can be effective to suppress essential tremor in people who do not respond to beta-blockers.
* Tranquilizers (also known as benzodiazepines) may be prescribed to temporarily help some people with tremor.
* However, these medications can negatively affect sleep, concentration, and coordination, and may cause physical dependence and withdrawal symptoms when stopped abruptly.
* Dopaminergic medications are often used to treat Parkinsonian tremors and other movement issues related to Parkinson’s disease.
* Anticholinergic medications can be used to treat dystonic tremors in some people.
* Botulinum toxin (commonly known as Botox) injections can be useful for dystonic head tremor and hand tremor. It can be also used for essential tremor patients who do not respond to oral medications.

Surgery

Surgical procedures may be performed when tremor does not respond to medications or severely impacts daily life.

Deep brain stimulation (DBS) is the most common form of surgical treatment of tremor. It uses surgically implanted electrodes to send high-frequency electrical signals to the thalamus, the deep structure of the brain that coordinates and controls some involuntary movements. A small pulse-generating device placed under the skin in the person’s upper chest (similar to a pacemaker) sends electrical stimuli to the brain to temporarily stop tremor. DBS is currently used to treat parkinsonian tremor, essential tremor, and dystonia.

Radiofrequency ablation uses a radio wave to generate an electric current that disrupts nerves’ signaling ability for six or more months. It is usually performed on only one side of the brain to improve tremor on the opposite side of the body.

Focused ultrasound uses MRI (magnetic resonance imaging) to deliver high frequency focused ultrasound that creates a lesion in tiny areas of the brain's thalamus thought to be causing the tremors. The treatment is approved only for people whose essential tremor does not respond well to anti-seizure or beta-blocking drugs.

Lifestyle changes for treating tremor

Certain lifestyle changes and techniques may provide some relief for mild to moderate tremor.

Physical, speech, and occupational therapy may help control tremor and adapt to daily challenges caused by the tremor.

Eliminating or reducing caffeine.

Assistive tools, such as special plates, spoons, or heavier utensils can lessen tremor and make it easier to eat.

Take medications on time. Talk with a doctor about stopping any medications that may be contributing to the tremor.

Reduce stress or stressful situations that can aggravate the tremor.

Wear clothes that make it easier to dress, such as those that use Velcro instead of buttons. Consider slip-on or no-tie shoes.

Get enough sleep. Some tremors worsen when a person is tired. Physical activity and exercise can help prevent fatigue and improve sleep.

What are the latest updates on tremor?

NINDS, a component of NIH, the leading supporter of biomedical research in the world, is the primary federal funding agency on tremor and other neurological disorders.

Researchers are working to better understand the underlying brain functions that cause tremor, identify the genetic factors that make individuals more likely to have tremor, and develop new and better treatment options.

Identifying brain functioning and disease markers

NINDS researchers are using non-invasive neuroimaging techniques to identify structural and functional changes in the brain. By developing sensitive and specific markers for movement disorders such as Parkinson's disease and essential tremor, researchers can track changes as diseases progress. Other researchers are using functional MRI technology to better understand normal and diseased brain circuit functions and associated motor behaviors. Scientists also hope to develop digital tools capable monitoring tremor in real-time, outside of the clinic, which may help optimize the treatment. Some researchers are studying brain tissue donated by individuals with and without tremor to identify the brain changes associated with tremor and gain deeper insight into its cause and potential treatment targets.

Genetic discoveries

Essential tremor may have a strong genetic component affecting multiple generations of families. NINDS researchers are building on previous genetics work to identify genes that make people more susceptible to familial early-onset (before age 40) essential tremor.  Researchers are focusing on multigenerational, early tremor onset families to better detect connections. Additionally, NINDS scientists are researching the impact of genetic changes on the development of essential tremor. 

Medications and other treatment methods

Medications are effective in about 50% of individuals with tremor. In order to develop assistive and rehabilitative devices for people with essential tremor, researchers are exploring where and how to minimize or suppress tremor while still allowing for voluntary movements.

Many people with essential tremor respond to ethanol (alcohol); however, it is not clear why or how. NINDS researchers are studying the impact of ethanol on tremor to determine the correct dosage amount and its physiological impact on the brain, and whether other medications without the side effects of ethanol can be effective.

Other NIH researchers hope to identify the source of essential tremor, study the effects of currently available tremor-suppressant drugs on the brain, and develop more targeted and effective therapies.

GettyImages-924953552.jpg

#24 Re: This is Cool » Miscellany » 2024-03-26 00:02:32

2104) Tagged Image File Format

Gist

TIF (or TIFF) is an image format used for containing high quality graphics. It stands for “Tagged Image File Format” or “Tagged Image Format”. The format was created by Aldus Corporation but Adobe acquired the format later and made subsequent update in this format.

Summary

A TIFF, which stands for Tag Image File Format, is a computer file used to store raster graphics and image information. A favorite among photographers, TIFFs are a handy way to store high-quality images before editing if you want to avoid lossy file formats.

Aldus eventually merged with Adobe Systems, who held the patent on the format from then on. Today, TIFF files are still widely used in the printing and publishing industry.

A TIFF file is a great choice when high quality is your goal, especially when it comes to printing photos or even billboards. TIFF is also an adaptable format that can support both lossy and lossless compression.

Details

Tag Image File Format or Tagged Image File Format, commonly known by the abbreviations TIFF or TIF, is an image file format for storing raster graphics images, popular among graphic artists, the publishing industry, and photographers. TIFF is widely supported by scanning, faxing, word processing, optical character recognition, image manipulation, desktop publishing, and page-layout applications. The format was created by the Aldus Corporation for use in desktop publishing. It published the latest version 6.0 in 1992, subsequently updated with an Adobe Systems copyright after the latter acquired Aldus in 1994. Several Aldus or Adobe technical notes have been published with minor extensions to the format, and several specifications have been based on TIFF 6.0, including TIFF/EP (ISO 12234-2), TIFF/IT (ISO 12639), TIFF-F (RFC 2306) and TIFF-FX (RFC 3949).

History

TIFF was created as an attempt to get desktop scanner vendors of the mid-1980s to agree on a common scanned image file format, in place of a multitude of proprietary formats. In the beginning, TIFF was only a binary image format (only two possible values for each pixel), because that was all that desktop scanners could handle. As scanners became more powerful, and as desktop computer disk space became more plentiful, TIFF grew to accommodate grayscale images, then color images. Today, TIFF, along with JPEG and PNG, is a popular format for deep-color images.

The first version of the TIFF specification was published by the Aldus Corporation in the autumn of 1986 after two major earlier draft releases. It can be labeled as Revision 3.0. It was published after a series of meetings with various scanner manufacturers and software developers. In April 1987 Revision 4.0 was released and it contained mostly minor enhancements. In October 1988 Revision 5.0 was released and it added support for palette color images and LZW compression.

TIFF is a complex format, defining many tags of which typically only a few are used in each file. This led to implementations supporting many varying subsets of the format, a situation that gave rise to the joke that TIFF stands for Thousands of Incompatible File Formats. This problem was addressed in revision 6.0 of the TIFF specification (June 1992) by introducing a distinction between Baseline TIFF (which all implementations were required to support) and TIFF Extensions (which are optional). Additional extensions are defined in two supplements to the specification, published September 1995 and March 2002 respectively.

Overview

A TIFF file contains one or several images, termed subfiles in the specification. The basic use-case for having multiple subfiles is to encode a multipage telefax in a single file, but it is also allowed to have different subfiles be different variants of the same image, for example scanned at different resolutions. Rather than being a continuous range of bytes in the file, each subfile is a data structure whose top-level entity is called an image file directory (IFD). Baseline TIFF readers are only required to make use of the first subfile, but each IFD has a field for linking to a next IFD.

The IFDs are where the tags for which TIFF is named are located. Each IFD contains one or several entries, each of which is identified by its tag. The tags are arbitrary 16-bit numbers; their symbolic names such as ImageWidth often used in discussions of TIFF data do not appear explicitly in the file itself. Each IFD entry has an associated value, which may be decoded based on general rules of the format, but it depends on the tag what that value then means. There may within a single IFD be no more than one entry with any particular tag. Some tags are for linking to the actual image data, other tags specify how the image data should be interpreted, and still other tags are used for image metadata.

TIFF images are made up of rectangular grids of pixels. The two axes of this geometry are termed horizontal (or X, or width) and vertical (or Y, or length). Horizontal and vertical resolution need not be equal (since in a telefax they typically would not be equal). A baseline TIFF image divides the vertical range of the image into one or several strips, which are encoded (in particular: compressed) separately. Historically this served to facilitate TIFF readers (such as fax machines) with limited capacity to store uncompressed data — one strip would be decoded and then immediately printed — but the present specification motivates it by "increased editing flexibility and efficient I/O buffering".  A TIFF extension provides the alternative of tiled images, in which case both the horizontal and the vertical ranges of the image are decomposed into smaller units.

An example of these things, which also serves to give a flavor of how tags are used in the TIFF encoding of images, is that a striped TIFF image would use tags 273 (StripOffsets), 278 (RowsPerStrip), and 279 (StripByteCounts). The StripOffsets point to the blocks of image data, the StripByteCounts say how long each of these blocks are (as stored in the file), and RowsPerStrip says how many rows of pixels there are in a strip; the latter is required even in the case of having just one strip, in which case it merely duplicates the value of tag 257 (ImageLength). A tiled TIFF image instead uses tags 322 (TileWidth), 323 (TileLength), 324 (TileOffsets), and 325 (TileByteCounts). The pixels within each strip or tile appear in row-major order, left to right and top to bottom.

The data for one pixel is made up of one or several samples; for example an RGB image would have one Red sample, one Green sample, and one Blue sample per pixel, whereas a greyscale or palette color image only has one sample per pixel. TIFF allows for both additive (e.g. RGB, RGBA) and subtractive (e.g. CMYK) color models. TIFF does not constrain the number of samples per pixel (except that there must be enough samples for the chosen color model), nor does it constrain how many bits are encoded for each sample, but baseline TIFF only requires that readers support a few combinations of color model and bit-depth of images. Support for custom sets of samples is very useful for scientific applications; 3 samples per pixel is at the low end of multispectral imaging, and hyperspectral imaging may require hundreds of samples per pixel. TIFF supports having all samples for a pixel next to each other within a single strip/tile (PlanarConfiguration = 1) but also different samples in different strips/tiles (PlanarConfiguration = 2). The default format for a sample value is as an unsigned integer, but a TIFF extension allows declaring them as alternatively being signed integers or IEEE-754 floats, as well as specify a custom range for valid sample values.

TIFF images may be uncompressed, compressed using a lossless compression scheme, or compressed using a lossy compression scheme. The lossless LZW compression scheme has at times been regarded as the standard compression for TIFF, but this is technically a TIFF extension, and the TIFF6 specification notes the patent situation regarding LZW. Compression schemes vary significantly in at what level they process the data: LZW acts on the stream of bytes encoding a strip or tile (without regard to sample structure, bit depth, or row width), whereas the JPEG compression scheme both transforms the sample structure of pixels (switching to a different color model) and encodes pixels in 8×8 blocks rather than row by row.

Most data in TIFF files are numerical, but the format supports declaring data as rather being textual, if appropriate for a particular tag. Tags that take textual values include Artist, Copyright, DateTime, DocumentName, InkNames, and Model.

Internet Media Type

The MIME type image/tiff (defined in RFC 3302) without an application parameter is used for Baseline TIFF 6.0 files or to indicate that it is not necessary to identify a specific subset of TIFF or TIFF extensions. The optional "application" parameter (Example: Content-type: image/tiff; application=foo) is defined for image/tiff to identify a particular subset of TIFF and TIFF extensions for the encoded image data, if it is known. According to RFC 3302, specific TIFF subsets or TIFF extensions used in the application parameter must be published as an RFC.

MIME type image/tiff-fx (defined in RFC 3949 and RFC 3950) is based on TIFF 6.0 with TIFF Technical Notes TTN1 (Trees) and TTN2 (Replacement TIFF/JPEG specification). It is used for Internet fax compatible with the ITU-T Recommendations for Group 3 black-and-white, grayscale and color fax.

Digital preservation

Adobe holds the copyright on the TIFF specification (aka TIFF 6.0) along with the two supplements that have been published. These documents can be found on the Adobe TIFF Resources page. The Fax standard in RFC 3949 is based on these TIFF specifications.

TIFF files that strictly use the basic "tag sets" as defined in TIFF 6.0 along with restricting the compression technology to the methods identified in TIFF 6.0 and are adequately tested and verified by multiple sources for all documents being created can be used for storing documents. Commonly seen issues encountered in the content and document management industry associated with the use of TIFF files arise when the structures contain proprietary headers, are not properly documented, and/or contain "wrappers" or other containers around the TIFF datasets, and/or include improper compression technologies, or those compression technologies are not properly implemented.

Variants of TIFF can be used within document imaging and content/document management systems using CCITT Group IV 2D compression which supports black-and-white (bitonal, monochrome) images, among other compression technologies that support color. When storage capacity and network bandwidth was a greater issue than commonly seen in today's server environments, high-volume storage scanning, documents were scanned in black and white (not in color or in grayscale) to conserve storage capacity.

The inclusion of the SampleFormat tag in TIFF 6.0 allows TIFF files to handle advanced pixel data types, including integer images with more than 8 bits per channel and floating point images. This tag made TIFF 6.0 a viable format for scientific image processing where extended precision is required. An example would be the use of TIFF to store images acquired using scientific CCD cameras that provide up to 16 bits per photosite of intensity resolution. Storing a sequence of images in a single TIFF file is also possible, and is allowed under TIFF 6.0, provided the rules for multi-page images are followed.

Details

TIFF is a flexible, adaptable file format for handling images and data within a single file, by including the header tags (size, definition, image-data arrangement, applied image compression) defining the image's geometry. A TIFF file, for example, can be a container holding JPEG (lossy) and PackBits (lossless) compressed images. A TIFF file also can include a vector-based clipping path (outlines, croppings, image frames). The ability to store image data in a lossless format makes a TIFF file a useful image archive, because, unlike standard JPEG files, a TIFF file using lossless compression (or none) may be edited and re-saved without losing image quality. This is not the case when using the TIFF as a container holding compressed JPEG. Other TIFF options are layers and pages.

TIFF offers the option of using LZW compression, a lossless data-compression technique for reducing a file's size. Use of this option was limited by patents on the LZW technique until their expiration in 2004.

The TIFF 6.0 specification consists of the following parts:

* Introduction (contains information about TIFF Administration, usage of Private fields and values, etc.)
* Part 1: Baseline TIFF
* Part 2: TIFF Extensions
* Part 3: Appendices

Additional Information

TIFFs are a file format popular with graphic designers and photographers for their flexibility, high quality, and near-universal compatibility. Learn more about these raster graphic files and how you can put them to use in your next project.

What is a TIFF file?

A TIFF, which stands for Tag Image File Format, is a computer file used to store raster graphics and image information. A favorite among photographers, TIFFs are a handy way to store high-quality images before editing if you want to avoid lossy file formats.

TIFF files:

* Have either a .tiff or .tif extension.
* Are a lossless form of file compression, which means they’re larger than most but don’t lose image quality.
* Work with Windows, Linux, and macOS.

TIFFs aren’t the smallest files around, but they enable a user to tag up extra image information and data, such as additional layers. They’re also compatible with editing software like Adobe Photoshop.

History of the TIFF file.

Aldus Corporation created the TIFF file in the mid-1980s for use in desktop publishing. TIFFs retained high-quality data and could publish content directly from a computer. The file was designed as a universally applicable format for desktop scanners — hardware that previously handled, depending on the make and model, only a limited set of file formats.

Initially, TIFFs were restricted to print publications before they expanded into digital content. Aldus Corporation was later acquired by Adobe, which has since been responsible for the copyright of the file format.

What are TIFFs used for?

TIFFs are popular across a range of industries — such as design, photography, and desktop publishing. TIFF files can be used for:

* High-quality photographs.

TIFFs are perfect for retaining lots of impressively detailed image data because they use a predominately lossless form of file compression. This makes them a great choice for professional photographers and editors.

* High-resolution scans.

The detailed image quality stored within a TIFF means they’re ideal for scanned images and high-resolution documents. You might find them a useful choice for storing high-resolution images of your artwork or personal documents.

* Container files.

TIFFs also work as container files that store smaller JPEGs. You could store several lower-resolution JPEGs within one TIFF if you wanted to email a selection of photos to a contact.

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#25 Re: Dark Discussions at Cafe Infinity » crème de la crème » 2024-03-25 20:06:30

1429) Nicolaas Bloembergen

Summary

Electrons in atoms and molecules have fixed energy levels, according to the principles of quantum physics. When there are transitions among different energy levels, light with certain frequencies is emitted or absorbed. This allows atoms and molecules to be analyzed with the help of the absorbed light’s spectrum. In the 1960s Nicolaas Bloembergen used laser light, which has waves in phase and of the same wavelength, to determine energy levels with great precision. By coordinating three laser waves, a fourth laser wave was created, and a larger part of the spectrum could be covered.

Details

Nicolaas Bloembergen (March 11, 1920 – September 5, 2017) was a Dutch-American physicist and Nobel laureate, recognized for his work in developing driving principles behind nonlinear optics for laser spectroscopy. During his career, he was a professor at Harvard University and later at the University of Arizona and at Leiden University in 1973 (as Lorentz Professor).

Bloembergen shared the 1981 Nobel Prize in Physics along with Arthur Schawlow and Kai Siegbahn because their work "has had a profound effect on our present knowledge of the constitution of matter" through the use of laser spectroscopy. In particular, Bloembergen was singled out because he "founded a new field of science we now call non-linear optics" by mixing "two or more beams of laser light... in order to produce laser light of a different wave length" and thus significantly broaden the laser spectroscopy frequency band.

Early life

Bloembergen was born in Dordrecht on March 11, 1920, where his father was a chemical engineer and executive. He had five siblings, with his brother Auke later becoming a legal scholar. In 1938, Bloembergen entered the University of Utrecht to study physics. However, during World War II, the German authorities closed the university and Bloembergen spent two years in hiding.

Career:

Graduate studies

Bloembergen left the war-ravaged Netherlands in 1945 to pursue graduate studies at Harvard University under Professor Edward Mills Purcell. Through Purcell, Bloembergen was part of the prolific academic lineage tree of J. J. Thomson, which includes many other Nobel Laureates, beginning with Thomson himself (Physics Nobel, 1906) and Lord Rayleigh (Physics Nobel, 1904), Ernest Rutherford (Chemistry Nobel 1908), Owen Richardson (Physics Nobel, 1928), and finally Purcell (Physics, Nobel 1952). Bloembergen's other influences include John Van Vleck (Physics Nobel, 1977) and Percy Bridgman (Physics Nobel, 1946).

Six weeks before his arrival, Purcell and his graduate students Torrey and Pound discovered nuclear magnetic resonance (NMR). Bloembergen was hired to develop the first NMR machine. At Harvard he attended lectures by Schwinger, Van Vleck, and Kemble. Bloembergen's NMR systems are the predecessors of modern-day MRI machines, which are used to examine internal organs and tissues. Bloembergen's research on NMR led to an interest in masers, which were introduced in 1953 and are the predecessors of lasers.

Bloembergen returned to the Netherlands in 1947, and submitted his thesis Nuclear Magnetic Relaxation at the University of Leiden. This was because he had completed all the preliminary examinations in the Netherlands, and Cor Gorter of Leiden offered him a postdoctoral appointment there. He received his Ph.D. degree from Leiden in 1948, and then was a postdoc at Leiden for about a year.

Professorship

In 1949, he returned to Harvard as a junior fellow of the Society of Fellows. In 1951, he became an associate professor; he then became Gordon McKay Professor of Applied Physics in 1957; Rumford Professor of Physics in 1974; and Gerhard Gade University Professor in 1980. In 1990 he retired from Harvard.

In addition, Bloembergen served as a visiting professor. From 1964 to 1965, Bloembergen was a visiting professor at the University of California, Berkeley. In 1996–1997, he was a visiting scientist at the college of optical sciences of the University of Arizona; he became a professor at Arizona in 2001.

Bloembergen was a member of the board of sponsors of the Bulletin of the Atomic Scientists and honorary editor of the Journal of Nonlinear Optical Physics & Materials.

Laser spectroscopy

By 1960 while at Harvard, he experimented with microwave spectroscopy. Bloembergen had modified the maser of Charles Townes, and in 1956, Bloembergen developed a crystal maser, which was more powerful than the standard gaseous version.

With the advent of the laser, he participated in the development of the field of laser spectroscopy, which allows precise observations of atomic structure using lasers. Following the development of second-harmonic generation by Peter Franken and others in 1961, Bloembergen studied how a new structure of matter is revealed, when one bombards matter with a focused and high-intensity beam of photons. This he termed the study of nonlinear optics. In reflection to his work in a Dutch newspaper in 1990, Bloembergen said: "We took a standard textbook on optics and for each section we asked ourselves what would happen if the intensity was to become very high. We were almost certain that we were bound to encounter an entirely new type of physics within that domain".

From this theoretical work, Bloembergen found ways to combine two or more laser sources consisting of photons in the visible light frequency range to generate a single laser source with photons of different frequencies in the infrared and ultraviolet ranges, which extends the amount of atomic detail that can be gathered from laser spectroscopy.

Personal life and death

Bloembergen met Huberta Deliana Brink (Deli) in 1948 while on vacation with his university's Physics Club. She was able to travel with him to the United States in 1949 on a student hospitality exchange program; he proposed to her when they arrived in the States, and were married by 1950 on return to Amsterdam. They were both naturalized as citizens of the United States in 1958. They had three children.

Bloembergen died on September 5, 2017, at an assisted living facility in his hometown Tucson, Arizona, of cardiorespiratory failure, at the age of 97.

Biography

In 2016 a Dutch biography was published, and in 2019 an English one.

Additional Information

Nicolaas Bloembergen (born March 11, 1920, Dordrecht, Netherlands—died September 5, 2017, Tucson, Arizona, U.S.) was a Dutch-born American physicist, corecipient with Arthur Leonard Schawlow of the United States and Kai Manne Börje Siegbahn of Sweden of the 1981 Nobel Prize for Physics for their revolutionary spectroscopic studies of the interaction of electromagnetic radiation with matter. Bloembergen made a pioneering use of lasers in these investigations.

Bloembergen received undergraduate (1941) and graduate (1943) degrees from the University of Utrecht. In 1946 he entered Harvard University, where with Edward Purcell and Robert Pound he did fundamental research on nuclear magnetic resonance. After receiving his Ph.D. from the University of Leiden in 1948, he returned to Harvard, where he became a professor of applied physics in 1951, Gerhard Gade university professor in 1980, and professor emeritus in 1990. In 2001 he began teaching at the University of Arizona. Bloembergen became a U.S. citizen in 1958.

Bloembergen’s early research on nuclear magnetic resonance led him to an interest in masers. He designed a three-stage crystal maser that was dramatically more powerful than earlier gaseous masers and that has become the most widely used microwave amplifier. Bloembergen then developed laser spectroscopy, which allows high-precision observations of atomic structure. His laser spectroscopic investigations led him in turn to formulate nonlinear optics, a new theoretical approach to the analysis of how electromagnetic radiation interacts with matter. Bloembergen’s research in nonlinear optics helped procure him a share of the Nobel Prize.

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