alpha particles


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alpha

 [al´fah]
the first letter of the Greek alphabet, α; used to denote the first position in a classification system; as, in names of chemical compounds, to distinguish the first in a series of isomers, or to indicate the position of substituent atoms or groups; also used to distinguish types of radioactive decay, brain waves or rhythms, adrenergic receptors, and secretory cells that stain with acid dyes, such as the alpha cells of the pancreas.
alpha-adrenergic blocking agent (alpha-blocker) (alpha-blocking agent) any of a group of drugs that selectively inhibit the activity of alpha receptors in the sympathetic nervous system. As with beta-adrenergic blocking agents, alpha-blocking agents compete with the catecholamines at peripheral autonomic receptor sites. This group includes ergot and its derivatives, and phentolamine.
alpha chain disease the most common heavy chain disease, occurring predominantly in young adults in the Mediterranean area, and characterized by plasma cell infiltration of the lamina propria of the small intestine resulting in malabsorption with diarrhea, abdominal pain, and weight loss, or, exceedingly rarely, by pulmonary involvement. The gastrointestinal form is immunoproliferative small intestine disease.
alpha-fetoprotein (AFP) a plasma protein produced by the fetal liver, yolk sac, and gastrointestinal tract and also by hepatocellular carcinoma, germ cell neoplasms, and other cancers in adults; elevated levels may also be seen in benign liver disease such as cirrhosis and viral hepatitis. The serum AFP level is used to monitor the effectiveness of cancer treatment.

During pregnancy some AFP crosses from the amniotic fluid to the mother's blood. If the fetus has a neural tube defect, large amounts of AFP will be found in the amniotic fluid and maternal blood. Blood screening tests for serum AFP can thus be done as a first step in the screening process; if test results are positive, further testing is indicated to diagnose the defect.
alpha particles a type of emission produced by the disintegration of a radioactive substance. The atoms of radioactive elements such as uranium and radium are very unstable, continuously breaking apart with explosive violence and emitting particulate and nonparticulate types of radiation. The alpha particles, consisting of two protons and two neutrons, have an electrical charge and form streams of tremendous energy when they are released from the disintegrating atoms. These streams of energy (alpha rays) can be used in treatment of various malignancies. See also radiation and radiation therapy.

alpha particles

, alpha rays
Radioactive, positively charged particles, equivalent to a helium nucleus (two protons and two neutrons), ejected at high speeds in certain atomic reactions.

alpha

the first letter of the Greek alphabet, A or α; used to denote the first position in a classification system; as, in names of chemical compounds, to distinguish the first in a series of isomers, or to indicate the position of substituent atoms or groups; also used to distinguish types of radioactive decay, brain waves or rhythms, adrenergic receptors, and secretory cells that stain with acid dyes, such as the alpha cells of the pancreas.

alpha-adrenergic antagonist
see alpha-blocking agents (below).
alpha-blocking agents
a group of drugs that selectively inhibit the activities of alpha receptors in the sympathetic nervous system. As with beta-blocking agents, alpha-adrenergic blocking agents compete with the catecholamines at peripheral autonomic receptor sites. This group includes ergot and its derivatives, and phenotolamine.
alpha brain waves
human brain-wave currents during electroencephalography having a frequency of approximately 8 to 13 hertz (pulsations per second), best seen when patient's eyes are closed and the patient is physically relaxed. See also electroencephalography.
alpha cells
glucagon-producing cells of the pancreas.
alpha-hemolysin
see alpha hemolysis.
alpha hemolysis
see alpha hemolysis.
alpha particles
a type of emission produced by the disintegration of a radioactive substance. The atoms of radioactive elements such as uranium and radium are very unstable; they are continuously breaking apart with explosive violence and emitting particulate and nonparticulate types of radiation. The alpha particles, consisting of two protons and two neutrons, have an electrical charge and form streams of tremendous energy when they are released from the disintegrating atoms. These streams of energy (alpha rays) are used to advantage in the treatment of various malignancies. See also radiation and radiotherapy.
alpha-responsive sympathomimetic drugs
drugs which cause vasoconstriction and maintain correct vascular permeability.
alpha-sheet
α-sheet a common structural feature of many proteins in which a single polypeptide chain turns regularly about itself to make a rigid cylinder in which each peptide bond is regularly hydrogen-bonded to other peptide bonds elsewhere in the chain.
alpha toxin
the toxins of many bacteria are classified as alpha, beta, etc.
References in periodicals archive ?
Given the above, referring to the adopted charges layout, the alpha particles geometry, and specified dimensions, one can write the final formula for the binding energy as the average energy per bond at subtracting the repulsive potentials of protons as whole units and the fractional charge repulsion potentials of neutrons:
Device Rad7 is a system composed of an alpha detector that is located in a Hemisphere chamber, a nuclear electronic system embedded that allow Rad7 to detect the alpha particle.
Bystander signals initiated by very low doses of alpha particles in irradiated normal human diploid fibroblasts induced DSB damage in unirradiated cells, and the percentage of DSBs in bystander cells was not dependent on the dose delivered (Hu et al.
They split a lithium nucleus into alpha particles, with an energy release providing the first direct experimental confirmation of Einstein's E=[mc.
It takes a direct hit from just one alpha particle to destroy a lone cancer cell.
So, DU's alpha particles won't penetrate the outermost (dead) layer of your skin, but if you get DU inside you--say, in your lungs--it can have deadly consequences.
The direction of the alpha particles automatically gives us the direction of the neutrons which, in tum, tells us where the neutrons have bit an object," san Maglich.
Actinium Pharmaceuticals is engaged in the development and commercialization of alpha particle immunotherapeutics based on a unique patent position for the utilization of actinium-225 and bismuth-213.
These act through molecular binding to cancer cells, where they can then emit alpha particles in precisely the right location to treat the tumor.
It is a radioactive compound which selectively binds with bone at the area of cancer involvement and emits a form of radiation called alpha particles.
Carbon-12, an essential element we're all made of, can only form when three alpha particles, or helium-4 nuclei, combine in a very specific way.