|
| | |
Diffraction
Diffraction The scattering of rays of light by collision with particles of matter as they pass through a medium such as air or water, or pass by a edge or narrow aperture. Plays a role when the pupil is small.
RELATED TERMS--------------------------------------
Pupil
A circular opening in the center of the iris. The size of the pupil changes according to the amount of light present. It is small in sunlight and large in a dark room.
SIMILAR TERMS--------------------------------------
Differential diagnosis
The determination of which two or more diseases with similar symptoms is the one from which a patient is suffering, based on an analysis of the clinical data.
Differential white cell count
The proportions of the different types of white cells in the blood, usually split into the different types of granulocytes, lymphocytes, monocytes, eosinophils, and basophils. The differential white cell count was originally done by visual inspection of the blood and is now often machine-generated. Normal values are: 24-62% neutrophils, 19-53% lymphocytes, 2-12% monocytes, 0-7% eosinophils, and 0-2% basophils.
Differentiate
The process cells undergo as they mature into normal cells. Differentiated cells have distinctive characteristics, perform specific functions, and are less likely to divide. See dedifferentiate, undifferentiated.
Differentiated
Having developed into a specialized cell or tissue type
.
Differentiated cancer
A cancer in which the cells are mature and look like cells in the tissue from it arose. Differentiated cancers tend to be decidedly less aggressive than undifferentiated cancers composed of immature cells.
Differentiation
The process whereby an unspecialized early embryonic cell or stem cell acquires the features of a specialized cell, such as a heart, liver, or muscle cell.
Differentiation antigen
A cell surface antigenic determinant found only on cells of a certain lineage and at a particular developmental stage; used as an immunologic marker.
Differentiation therapy
An approach to the treatment of advanced or aggressive malignancies in which the malignant cells are treated so that they can resume the process of maturation and differentiation into mature cells.
Differin
Differin is a prescription or over-the-counter drug which is (or once was) approved in the United States and possibly in other countries. Active ingredient(s): adapalene.
Diffuse
Not definitely localized or limited; spread widely through a tissue or substance.
Diffuse degeneration of gray matter with cirrhosis
A progressive disease of the nervous system characterized by spasticity (tightness), myoclonus and dementia and by liver problems with jaundice and cirrhosis.
Diffuse idiopathic skeletal hyperostosis
Abbreviated as DISH. A form of degenerative arthritis characteristically associated with flowing calcification along the sides of the vertebrae of the spine and commonly associated with inflammation (tendinitis) and calcification of the tendons at their attachments points to bone. Because areas of the spine and tendons can become inflamed, antiinflammatory medications (NSAIDs) such ibuprofen can be helpful in both relieving pain and inflammation.
Diffuse mastocytosis
A form of mastocytosis in which the entire skin is thickened and leathery with generalized reddening and intense pruritus (itching) due to widespread infiltration of the skin with mast cells.
Diffuse toxic goiter
Graves disease, the most common cause of hyperthyroidism (overactivity of the thyroid gland), with generalized diffuse overactivity ("toxicity") of the entire thyroid gland which becomes enlarged into a goiter.
PREVIOUS AND NEXT TERMS--------------------------------------
Delayed match-to-sample
Subject is shown a stimulus and then after a delay is required to choose the same stimulus from a number of stimuli to obtain reward.
Depth capture
Objects in an image with no apparent depth information can be captured by surrounding surfaces which do contain depth information.
Diaplopia
Double vision.
Dichoptic stimulation
When different images are presented to each eye.
Dichromatic color vision
Color vision based on two cone photoreceptor pigments in the retina.
Diffraction
Direction selectivity
A difference in the response of a cell to a pattern of light moving through it receptive field according to the direction of movement. Cells respond well when a stimulus moves in one direction and not in the opposite direction.
Discounting the illuminant
Illumination of the visual world tens to be non-uniform, and fluctuates. in order for the visual system to create a consistent perception of color and lightness it must somehow discount fluctuation and gradient in the lighting source.
Disparity gradient
The ratio of the difference between two feature's disparities and their cyclopean separation. Steeply slanted surfaces have large disparity gradients. Human binocular fusion will only tolerate a disparity gradient of about 1.
Dorsal pathway
One of two theorized systems of visual information processing. Information thought to progress toward the parietal cortex V1-> V2 -> MT -> MST -> STP. Functions in comprehension of spatial arrangement.
Derma
Skin.
We thank you for using the Health Dictionary to search for Diffraction. If you have a better definition for Diffraction than the one presented here, please let us know by making use of the suggest a term option. This definition of Diffraction may be disputed by other professionals. Our attempt is to provide easy definitions on Diffraction and any other medical topic for the public at large.This dictionary contains 25007 terms. |
|
|
