| age-structured model | <epidemiology> A mathematical model which take into consideration the division of the host population into different age classes. Such models can used to consider the consequences of such factors as age-dependent infection, morbidity or mortality rates or of age-specific vaccination schedules. (05 Dec 1998) |
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| structured | <biology> Having a definite organic structure; showing differentiation of parts. "The passage from a structureless state to a structured state is itself a vital process." (H. Spencer) Source: Websters Dictionary (01 Mar 1998) |
| structured noise | In radiology, the signals from anatomic structures which interfere with the detection of significant pathology. (05 Mar 2000) |
| achromatic objective | <microscopy> An objective that is corrected chromatic for two colours, and spherically for one, usually in the yellow-green part of the spectrum. (05 Aug 1998) |
| apochromatic objective | <microscopy> A lens system whose secondary chromatic aberrations have been substantially reduced. It is designed to provide the same focal length for three wavelengths and freedom from spherical aberration for two wavelengths of light. The magnification can still vary with wavelength in which case a compensating eyepieces used to cancel the coloured fringes. (05 Aug 1998) |
| plan apochromatic objective lens | <physics> A modern, high-numerical aperture microscope objective lens designed with high degrees of corrections for various aberrations. It is corrected for spherical aberration in four wavelengths (dark blue, blue, green, and red), for chromatic aberration in more than these four wavelengths, and for flatness of field. A single Plan Apo objective may contain as many as 11 lens elements. (05 Aug 1998) |
| homogeneous immersion objective | <microscopy> An objective to be immersed in a liquid of a certain refractive index and dispersion value as specified by the manufacturer of the objective. An oil-immersion objective, the most important type, is intended to be immersed in cedarwood oil (nD = 1.515) or in its manmade optical equivalent. A water-immersion objective is for dipping into an aqueous specimen mount. Alpha-monobromonaphthalene has such a high refractive index (nD = 1.66) that a very highly resolving objective (1.60 numerical aperture) was designed to be immersed in that liquid, for use by reflected light on metals and other opaque objects. (05 Aug 1998) |
| semi-apochromatic objective | <microscopy> A compromise, in the correction for chromatic and spherical aberration, between achromatic and apochromatic objectives, such as a fluorite objective. (05 Aug 1998) |
| dark field objective | <microscopy> Certain objectives for high-power, dark fieldwork equipped with iris diaphragms or funnel stops so that their apertures may be reduced to correspond to the dark field con-denser with which they are used. (05 Aug 1998) |
| dry objective | <microscopy> Any microscope objective designed for use without immersion liquids. (05 Aug 1998) |
| immersion objective | <microscopy> An objective in which the medium of high refractive index and is used in the object space to increase the numerical aperture and hence the resolving power of the lens. See: homogeneous immersion of objective. (05 Aug 1998) |
| objective | 1. <psychology> Perceptible to the external senses. 2. <ophthalmology> The lens or system of lenses in a microscope (or telescope) that is nearest to the object under examination. Origin: L. Objectivus (18 Nov 1997) |
| objective assessment data | Those facts presented by the client that show his/her perception, understanding and interpretation of what is happening. (05 Mar 2000) |
| objective circle | <microscopy> When the focused objective is examined by with- drawing the ocular and viewing its back focal plane through the microscope bodytube, the limiting boundary of the objective, the circumference of the white spot of light, is the objective circle. (05 Aug 1998) |
| objective, fluorite | <microscopy> An objective using the mineral fluorite in its construction. It is usually intermediate between achromatic and apochromatic in correction, but may be more highly corrected. See: illumination, eyepiece. (05 Aug 1998) |