Math Is Fun Forum

Q: What part of a computer does a spider use?
A: The webcam.
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Q: What happens when a Buddhist becomes totally absorbed with the computer he is working with?
A: He enters Nerdvana.
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Q: Why did Jack and Jill "really" go up the hill?
A: To get better Wi-fi.
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Q: What was the spider doing on the computer?
A: Searching the web!
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Q: Why can't an elephant use a computer?
A: He's too afraid of the mouse.
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Thermocouple

Gist

A thermocouple, a temperature-measuring device consisting of two wires of different metals joined at each end. One junction is placed where the temperature is to be measured, and the other is kept at a constant lower temperature.

Summary

A thermocouple, a temperature-measuring device consisting of two wires of different metals joined at each end. One junction is placed where the temperature is to be measured, and the other is kept at a constant lower temperature. A measuring instrument is connected in the circuit. The temperature difference causes the development of an electromotive force (known as the Seebeck effect) that is approximately proportional to the difference between the temperatures of the two junctions. Temperature can be read from standard tables, or the measuring instrument can be calibrated to read temperature directly.

Any two different metals or metal alloys exhibit the thermoelectric effect, but only a few are used as thermocouples—e.g., antimony and bismuth, copper and iron, or copper and constantan (a copper-nickel alloy). Usually platinum, either with rhodium or a platinum-rhodium alloy, is used in high-temperature thermocouples. Thermocouple types are named (e.g., type E [nickel, chromium, and constantan], J [iron and constantan], N [two nickel-silicon alloys, one of which contains chromium and magnesium], or B [a platinum-rhodium alloy]) according to the metals used to make the wires. The most common type is K (nickel-aluminum and nickel-chromium wires) because of its wide temperature range (from about −200 to 1,260 °C [−300 to 2,300 °F]) and low cost.

A thermopile is a number of thermocouples connected in series. Its results are comparable to the average of several temperature readings. A series circuit also gives greater sensitivity, as well as greater power output, which can be used to operate a device such as a safety valve in a gas stove without the use of external power. a temperature-measuring device consisting of two wires of different metals joined at each end. One junction is placed where the temperature is to be measured, and the other is kept at a constant lower temperature.

Details

A thermocouple, also known as a "thermoelectrical thermometer", is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage as a result of the Seebeck effect, and this voltage can be interpreted to measure temperature. Thermocouples are widely used as temperature sensors.

Commercial thermocouples are inexpensive, interchangeable, are supplied with standard connectors, and can measure a wide range of temperatures. In contrast to most other methods of temperature measurement, thermocouples are self-powered and require no external form of excitation. The main limitation with thermocouples is accuracy; system errors of less than one degree Celsius (°C) can be difficult to achieve.

Thermocouples are widely used in science and industry. Applications include temperature measurement for kilns, gas turbine exhaust, diesel engines, and other industrial processes. Thermocouples are also used in homes, offices and businesses as the temperature sensors in thermostats, and also as flame sensors in safety devices for gas-powered appliances.

Principle of operation

In 1821, the German physicist Thomas Johann Seebeck discovered that a magnetic needle held near a circuit made up of two dissimilar metals got deflected when one of the dissimilar metal junctions was heated. At the time, Seebeck referred to this consequence as thermo-magnetism. The magnetic field he observed was later shown to be due to thermo-electric current. In practical use, the voltage generated at a single junction of two different types of wire is what is of interest as this can be used to measure temperature at very high and low temperatures. The magnitude of the voltage depends on the types of wire being used. Generally, the voltage is in the microvolt range and care must be taken to obtain a usable measurement. Although very little current flows, power can be generated by a single thermocouple junction. Power generation using multiple thermocouples, as in a thermopile, is common.

Additional Information

A thermocouple is a sensor for measuring temperature. This sensor consists of two dissimilar metal wires, joined at one end, and connected to a thermocouple thermometer or other thermocouple-capable device at the other end. When properly configured, thermocouples can provide temperature measurements over wide range of temperatures.

Thermocouples are known for their versatility as temperature sensors therefore commonly used on a wide range of applications - from an industrial usage thermocouple to a regular thermocouple found on utilities and regular appliances. Due to their wide range of models and technical specifications, it is extremely important to understand its basic structure, how it works, its ranges as to better determine what is the right type and material of thermocouple for your application.

Q: What does a baby computer calls its father?
A: Obsolete
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Q: What do you get if you cross a computer with a ballet dancer?
A: The Netcracker suite.
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Q: What does a king computer do?
A: Execute his programs!
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Q: Why won' tpeople take their iPhones to the bathroom?
A: Because they don't want to give away their IP address!
* * *
Q: How do you get a computer drunk?
A: A Screenshot of Tequila.
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Biopsy

Gist

A biopsy is a medical procedure where a small sample of tissue is removed from the body for examination under a microscope. This sample is then analyzed by a pathologist to help diagnose or monitor various medical conditions.

A biopsy is the removal of tissue from any part of the body to examine it for disease. Some may remove a small tissue sample with a needle while others may surgically remove a suspicious nodule or lump. Most needle biopsies are performed on an outpatient basis with minimal preparation.

Summary

A biopsy is a medical test commonly performed by a surgeon, an interventional radiologist, or an interventional cardiologist. The process involves the extraction of sample cells or tissues for examination to determine the presence or extent of a disease. The tissue is then fixed, dehydrated, embedded, sectioned, stained and mounted before it is generally examined under a microscope by a pathologist; it may also be analyzed chemically. When an entire lump or suspicious area is removed, the procedure is called an excisional biopsy. An incisional biopsy or core biopsy samples a portion of the abnormal tissue without attempting to remove the entire lesion or tumor. When a sample of tissue or fluid is removed with a needle in such a way that cells are removed without preserving the histological architecture of the tissue cells, the procedure is called a needle aspiration biopsy. Biopsies are most commonly performed for insight into possible cancerous or inflammatory conditions.

Details

Overview

A biopsy is a procedure to remove cells, tissue or fluid for examination by a medical pathologist. Healthcare providers do biopsies when they identify areas of concern or if you have symptoms or signs of certain conditions. There are different types of biopsy procedures.

A biopsy removes samples of your tissue, cells or fluids so a medical pathologist can examine them for signs of disease.

Biopsies are one of the ways healthcare providers determine what’s going on in your body. Biopsy types include bone marrow biopsy, excisional biopsy, needle biopsy and sentinel node biopsy.

What is a biopsy?

A biopsy is one of the ways healthcare providers determine what’s going on in your body. In a biopsy, a provider removes samples of your tissue, cells or fluids so a medical pathologist can examine them for signs of disease. Providers may recommend biopsies to diagnose or monitor medical conditions or to plan treatment.

You may hear the term “biopsy” and think “cancer,” but providers do biopsies to diagnose many medical conditions, like:

* Inflammatory disorders, such as in your kidney (nephritis) or liver (hepatitis).
* Infections, like tuberculosis.
* Immune disorders, such as chronic pancreatitis.
* Peptic ulcer disease.
* Endometriosis.

Types of biopsies

All biopsies are procedures to obtain samples of tissue and fluid, but they’re done in different ways. Healthcare providers may do biopsies in medical offices or operating rooms. Biopsy types include:

* Bone marrow biopsy: Providers use a special biopsy needle and syringe to obtain a small sample of bone marrow. They do bone marrow biopsies to diagnose blood cancers, blood disorders and other diseases.
* Cone biopsy: Also known as conization or cold knife biopsy, providers do cone biopsies to remove abnormal tissue from your cervix. Cone biopsies may detect cervical cancer or cervical dysplasia that could lead to cancer.
* Excisional biopsy or incisional biopsies: In these procedures, providers make incisions or cuts in your body to remove tissue from inside your body. Excisional biopsies involve removing entire lumps or suspicious areas. Incisional biopsies involve taking tissue samples of lumps or suspicious areas.
* Liquid biopsy: This blood test detects signs of cancerous cells or cancer cell DNA.
* Needle biopsy: Providers use needle biopsies to extract cells, fluid or tissues. Your provider may order a needle biopsy if they feel an unusual lump or bump on your body or imaging tests detect potential issues.
* Punch biopsy: Providers use a special device to remove tissue that may be cancerous. Providers use a special device that punches a hole in your skin’s surface.
* Sentinel node biopsy: Providers do this procedure to see if cancer cells have spread from an original tumor.
* Shave biopsy: Providers use a razor to scrape up a small sample of skin cells to detect skin cancer.

Additional Information

A biopsy is a procedure done to remove tissue or cells from the body for examination under a microscope. Some biopsies can be done in a healthcare provider's office, while others need to be done in a hospital setting. In addition, some biopsies can be done with a local anesthetic to numb just the local area involved. Others may need sedation or even full anesthesia that puts you completely asleep during the procedure.

Biopsies are usually done to find out if a tumor is cancerous or to find the cause of an unexplained lesion, mole, infection, or inflammation.

How is a biopsy done?

A biopsy can be done in various ways. It depends on the type of specimen needed. Tissue samples are usually small and taken from tissue that appears changed in structure, such as a tumor.

Types of biopsies

* Endoscopic biopsy. This type of biopsy is done through a fiberoptic endoscope. This is a long, thin tube that has a close-focusing telescope on the end for viewing. The scope is passed through a natural body orifice (for example, rectum or mouth) or a small incision. It is used to look at the organ in question for abnormal or suspicious areas so that a small amount of tissue can be removed for study. Endoscopic procedures are named for the organ or body area to be viewed or treated. The healthcare provider can insert the endoscope into the gastrointestinal tract (alimentary tract endoscopy), bladder (cystoscopy), abdominal cavity (laparoscopy), joint cavity (arthroscopy), mid-portion of the chest (mediastinoscopy), or trachea and bronchial system (laryngoscopy and bronchoscopy).

* Bone marrow biopsy. Bone marrow aspiration or biopsy involves taking a small amount of bone marrow fluid (aspiration) and/or solid bone marrow tissue (called a core biopsy). The tissue is usually taken from the back of the hip bones to be examined for the number, size, and maturity of blood cells and/or abnormal cells.

* Excisional or incisional biopsy. This type of biopsy is often used when a wider or deeper portion of the tissue is needed. Using a scalpel (surgical knife), a full thickness of skin or all or part of a large tumor may be removed for further examination. The wound is sewn closed (with surgical thread).

When the entire tumor is removed, it is called an excisional biopsy. If only a portion of the tumor is removed, it is called an incisional biopsy. For instance, excisional biopsy is the method usually preferred when melanoma is suspected. Both types of biopsies can be done by using local or regional anesthesia. If the tumor is inside the chest or belly, general anesthesia is used. Under some circumstances, surgeons will take an excisional or incisional biopsy that goes immediately to the pathologist while the patient remains under anesthesia. This is to make sure of complete removal of a tumor. One example of this is during Mohs surgery on the face.

* Fine needle aspiration (FNA) biopsy. This type of biopsy involves using a thin needle and syringe to remove very small pieces from a tumor. Local anesthetic is sometimes used to numb the area. The test rarely causes much discomfort and leaves no scar.

FNA is not used for diagnosis of a suspicious mole. It may be used to biopsy large lymph nodes near a melanoma to see if the melanoma has spread. Breast and thyroid tumors are examples of tumors that may be studied through FNA. A computed tomography scan (CT or CAT scan) may be used to guide a needle into a tumor in an internal organ, such as the lung or liver. An ultrasound, fluoroscopy (a type of continuous X-ray) or other study may also be used for guidance of the needle. A core biopsy is similar to the FNA, but with a larger needle for a larger tissue sample.

* Punch biopsy. Punch biopsies involve taking a deeper sample of skin with a biopsy instrument that removes a short cylinder, or "apple core," of tissue. After a local anesthetic, the instrument is rotated on the surface of the skin until it cuts through all the layers. This includes the dermis, epidermis, and the most superficial parts of the subcutis (fat).

* Shave biopsy. This type of biopsy involves removing the top layers of skin by shaving it off. Shave biopsies are used to diagnose some basal cell or squamous cell skin cancers as well as other skin lesions, but they are not recommended for suspected melanomas of the skin. Shave biopsies are also done with a local anesthetic.

* Reflectance confocal microscopy (RCM). RCM is a technique that allows the healthcare provider to look at an abnormal area of skin to a certain depth without cutting into the skin or removing a skin sample. RCM is used widely in Europe, and it's now available in some centers in the U.S.

Common biopsy sites

* Bone marrow

* Brain

* Breast

* Gastrointestinal tract (stomach and intestines)

* Liver

* Lung

* Lymph nodes

* Skin

* Thyroid

After a biopsy, the tissue specimen is sent to the pathology lab to be examined and analyzed. The time needed to get results back varies depending on the type of tissue and the tests being done.