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 ?
Indeed, it is known that to remove of only a nucleon from alpha particles the energy about 20 MeV is required [9].
3 days, which itself emits an alpha particle and converts to PO-218, a radioactive material with 3-minute half-life.
Designed and built by Canadian scientist Rail Gellert, the APXS uses radioactive curium-244 to produce both alpha particles and X-rays that probe the elemental composition of Martian rocks.
210]Po presents a radiation hazard only if taken into the body because its alpha particles have a range of only 40-50 [micro]m in biological tissue and are easily stopped by surface layers of the skin (Jefferson et al.
The first layer, which is made of a thin plastic, detects alpha particles, which are composed of two protons and two neutrons much like the nucleus of a helium atom.
i] as a result of the XASW interaction with the alpha particles, which oscillate at the second cyclotron harmonic of helium, in this case [theta] [approximately equal to] 0.
Rutherford advised probing the atom with the alpha particles expelled by certain radioactive atoms.
The counters from Cooking Hacks will show beta and gamma radiation, and can be fitted with tubes that have a thin mica window at one end to show alpha particles.
Human skin is thick enough to not be affected, but if you breathe in alpha particles, they can be absorbed by and damage bronchial and lung tissue.
Six samples of radioactive curium-242 in the instrument bombarded the lunar soil with alpha particles (helium nuclei).
TINY missiles containing the same kind of radiation used to kill a former spy are being developed to destroy cancer Scientists have found a way to package deadly alpha particles inside DNA-sized tubes of carbon, it was revealed yesterday.
He explores the interactions with matter and energetic particles, including photons, electrons, protons, alpha particles and neutrons with a variety of applications including photon and neutron cross sections, charged particle stopping powers, electron mean ranges and angular distributions, covering photons as they appear in long wavelengths and other configurations and as an element of photoelectric absorption, electrons, including in elastic scattering from and atom and in the case of collision energy loss, protons and heavier ions, including proton and alpha particle stopping powers in selected materials, and a range of topics on neutron interactions.