ray (redirected from x-r's)

ray (ra)

1. a line emanating from a center.

2. a more or less distinct portion of radiant energy (light or heat), proceeding in a specific direction.

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α-rays , alpha rays high-speed helium nuclei ejected from radioactive substances; they have less penetrating power than beta rays.

β-rays , beta rays electrons ejected from radioactive substances with velocities as high as 0.98 of the velocity of light; they have more penetrating power than alpha rays, but less than gamma rays.

digital ray 

1. a digit of the hand or foot and the corresponding portion of the metacarpus or metatarsus, considered as a continuous structural unit.

2. in the embryo, a mesenchymal condensation of the hand or foot plate that outlines the pattern of a future digit.

γ-rays , gamma rays electromagnetic radiation of short wavelengths emitted by an atomic nucleus during a nuclear reaction, consisting of high-energy photons, having no mass and no electric charge, and traveling with the speed of light and with great penetrating power.

grenz rays  very soft x-rays having wavelengths about 20 nm, lying between x-rays and ultraviolet rays.

medullary rays  the intracortical prolongations of the renal pyramids.

roentgen rays  x-r's.

x-rays  electromagnetic vibrations of short wavelengths (approximately 0.01 to 10 nm) or corresponding quanta that are produced when electrons moving at high velocity impinge on various substances; they are commonly generated by passing high-voltage current (approximately 10,000 volts) through a Coolidge tube. They are able to penetrate most substances to some extent, to affect a photographic plate, to cause certain substances to fluoresce, and to strongly ionize tissue.

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Ray, John 1627-1705.

English naturalist who was the first to use anatomy to distinguish between specific plants and animals. He established the species as the basic classification of living things.

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ray (r)

n.

1. A narrow beam of light or other electromagnetic radiation.

2. A narrow beam of particles, as a cathode.

3. A structure or part having the form of a straight line extending from a point.

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ray

Etymology: L, radius

a beam of radiation, such as heat or light, moving away from a source.

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Ray, Marilyn Anne,

a nursing theorist who introduced the Theory of Bureaucratic Caring, which emphasizes the interconnectedness of nursing care and health care organizations. The theory emphasizes the holistic nature of an organization rather than simple cause-effect relationships of individual actions. Spiritual-ethical caring by nurses, the ultimate goal of which is the promotion of well-being through caring, has a positive effect on health care organizations and can become an economic resource.

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ray(s),

n a line of light, heat, or other form of radiant energy. A ray is a more or less distinct or isolated portion of radiant energy, whereas the word
rays is a very general term for any form of radiant energy, whether vibratory or particulate.

ray, alpha,

n See particle, alpha.

ray, beta,

n See particle, beta.

ray, cathode,

n See electron stream.

ray, central,

n the center of a radiographic beam.

ray, cosmic,

n radiation that originates outside the earth's atmosphere. Cosmic rays have extremely short wavelengths. They are able to produce ionization as they pass through the air and other matter and are capable of penetrating many feet of material such as lead and rock. The primary cosmic rays probably consist of atomic nuclei (mainly protons), some of which may have energies of the order of 1010 to 1015 eV. Secondary cosmic rays are produced when the primary cosmic rays interact with nuclei and electrons (e.g., in the earth's atmosphere). Secondary cosmic rays consist mainly of mesons, protons, neutrons, electrons, and photons that have less energy than the primary rays. Practically all the primary cosmic rays are absorbed in the upper atmosphere. Almost all cosmic radiation observed at the earth's surface is of the secondary type.

ray, gamma,

n photons with a shorter wavelength than those ordinarily used in diagnostic medical and dental radiography and that originate in the nuclei of atoms. A quantum of electromagnetic radiation emitted by a nucleus as a result of a quantum transition between two energy levels of the nucleus; e.g., as a radioisotope decays, it gives off energy, some of which may be in the form of gamma radiation.

ray, grenz

n roentgen rays that are greater in length than 1 Å; used in radiography of soft tissues, insects, flowers, and microscopic sections of teeth and surrounding tissues. These rays are the result of using approximately 10 to 20 kV in a specially constructed radiation-generating device. They have a wavelength of about 2 Å.

ray, neutron,

n particulate ionizing radiation consisting of neutrons. On impact with nuclei or atoms, neutrons possess enough kinetic energy to set the nuclei or atoms in motion with sufficient velocity to ionize matter or enter into nuclear reactions that result in the emission of ionizing radiation. The former variety is usually called the fast neutron, and the latter the thermoneutron, with gradations of epithermal and slow neutrons between them.

ray, roentgen (r)

n an international unit based on the ability of radiation to ionize air. The exposure to x- or gamma radiation such that the associated corpuscular emission per 0.001293 g of air produces, in air, ions carrying 1 esu of quantity of electricity of either sign (2.083 billion ion pairs).

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ray

a line emanating from a center, as a more or less distinct portion of radiant energy (light or heat), proceeding in a specific direction.

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alpha r's,

α-r's high-speed helium nuclei ejected from radioactive substances; they have less penetrating power than beta rays. See also alpha particles.

beta r's,

β-r's, beta particles electrons ejected from radioactive substances with velocities as high as 0.98 of the velocity of light; they have more penetrating power than alpha rays, but less than gamma rays.

digital ray

a digit of the hand or foot and corresponding metacarpal or metatarsal bone, regarded as a continuous unit.

ray fungus

branched filamentous appearance of Actinomyces bovis in granules in pus.

gamma r's,

γ-r's electromagnetic radiation of short wavelengths emitted by an atomic nucleus during a nuclear reaction, consisting of high-energy photons, having no mass and no electric charge, and traveling with the speed of light and with great penetrating power.

They have very great range in penetrating tissues and cytotoxic effects, especially on nuclei and on tissues which are replicating rapidly. The fetus, bone marrow, blood, liver and gonads are particularly susceptible. See also radiation injury, radiation therapy.

medullary ray

a cortical extension of a bundle of tubules from a renal pyramid.

roentgen r's

x-rays.

x-r's

see x-ray.

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ray 

In geometrical optics, a straight line representing the direction of propagation of light.
axial ray A ray that is coincident with the axis of an optical system.
chief ray A ray joining an object point to the centre of the entrance pupil of an optical system (Fig. R2). See pencil of light.
emergent ray A ray of light in image space either after reflection (reflected ray) or after refraction (refracted ray).
extraordinary ray See birefringence.
incident ray A ray of light in object space that strikes a reflecting or refracting surface.
marginal ray A ray joining the axial point of an object to the edge or margin of an aperture or pupil (Fig. R2).
ordinary ray See birefringence.
paraxial ray A light ray that forms an angle of incidence so small that its value in radians is almost equal to its sine or its tangent. (i.e. sin θ = θ or tan θ = θ. These are approximate expressions referred to as the paraxial approximation (or the gaussian approximation). See paraxial optics; paraxial region; gaussian theory.
principal ray A ray joining the extreme off-axis object point to the centre of the entrance pupil or aperture (Fig. R2).
ray tracing Technique used in optical computation consisting of tracing the paths of light rays through an optical system by graphical methods or by using formulae. Nowadays, computer methods are used. See sign convention.

Fig. R2 Rays of light incident to the eye (E, centre of the entrance pupil of the eye)

Table R1 Differences between the sine and the tangent values of various angles (in degrees and radians). The error is calculated between the sine value and the value in radians and between the value in radians and the tangent value
angle (deg)		angle (rad)		sine value		tangent value		error (%) sine error		error (%) tangent error
0.5		0.008 727		0.008 727		0.008 727		0.00		0.00
1		0.017 453		0.017 452		0.017 455		0.01		0.01
2		0.034 907		0.034 899		0.034 921		0.02		0.04
3		0.052 360		0.052 336		0.052 408		0.05		0.09
4		0.069 813		0.069 756		0.069 927		0.08		0.16
5		0.087 266		0.087 156		0.087 489		0.13		0.25
6		0.104 720		0.104 528		0.105 104		0.18		0.37
7		0.122 173		0.121 869		0.122 785		0.25		0.50
8		0.139 626		0.139 173		0.140 541		0.33		0.65
10		0.174 533		0.173 648		0.176 327		0.51		1.03
15		0.261 799		0.258 819		0.267 949		1.15		2.35
520		0.349 066		0.342 020		0.363 970		2.06		4.27
30		0.523 599		0.500 000		0.577 350		4.72		10.27

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Patient discussion about x-r's.

Q. I have a low back pain that radiates to my leg when i pick up stuff. Is it a disc herniation? I am a 43 years old bank teller. During the past 5 months I've suffered from a low back pain. The pain is not very strong, but it gets much worse while doing physical activity. When i walk or lift heavy things the pain is even stronger, and it radiates to my left leg. Can it be signs for disc herniation?

A. You can't tell for sure that your symptoms are due to a specific disc pathology.
When i had similar symptoms i went to the GP and he told me to lay down on your back. Then he slowly raised my left leg while the knee is kept in extension.
He said that If raising the leg over 60 degree exacerbates the pain its very likely to be disc herniation. But you should go to your GP and have him examine you.

Q. what does a sun block cream do? and what are a UV rays?

A. It blocks out harmful Ultra violet rays from the skin as the previous entries have related; however it can also block your ability to produce vitamin D. If you live in a northerly area or one that receives limited sunlight, its recommended to get at least 15 minutes of sun a day (this is probably best done with minimal sunblock) and according to personnal sun sensitivity. Another thing to keep in mind is that sunblock works best if applied 20 minutes before sun exposure.

Q. What does radiation do for cancer patients? We found out today that my grandmother has cancer and my mother said that the oncologist is planning on using radiation to ease her pain. My question is, what does radiation do? I know, eases pain, but how?

A. hello;radiation therapy/an anticancer drugs are used to suppress or arrest the rate of cell division in any tumor cells, the rad also kills good cells also.