penumbra


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penumbra

 [pĕ-num´brah]
1. the part of a shadow in which there is a small amount of illumination from a light source.
2. blurring at the edges of a structure on a radiograph.

pe·num·bra

(pe-nŭm'bră),
The region of partial illumination or radiation caused by light or x-rays not originating from a point source; also called geometric unsharpness.
[Mod. L., fr. L. paene, almost, + umbra, shadow]

pe·num·bra

(pĕ-nŭm'bră)
1. radiology The blurred margin of an image.
2. radiation physics The region at the edges of a radiation beam over which a rapid change in dosage rate occurs.
Synonym(s): geometric unsharpness.
[Mod. L., fr. L. paene, almost, + umbra, shadow]

penumbra 

1. Region of very low illumination on a dark background.
2. Zone in which the brightness varies from some illumination to zero (umbra) in the shadow cast by an opaque object intercepting light from an extensive light source. See shadow.

pe·num·bra

(pĕ-nŭm'bră)
1. radiology the blurred margin of an image.
2. radiation physics the region at the edges of a radiation beam over which a rapid change in dosage rate occurs.
Synonym(s): geometric unsharpness.
[Mod. L., fr. L. paene, almost, + umbra, shadow]

penumbra

a blurred edge to an image, a halo effect, in an x-ray film caused usually by an overlarge focal spot exacerbated by a long object-to-film distance.
References in periodicals archive ?
Export yields at the Penumbra Coal Mine averaged 57.
Because if the pore expands until it has the appearance of a spot, it can be observed that its edges are ragged, and the penumbra is formed entirely of very fine rays converging towards the middle of the shape.
9[degrees] penumbra (2) Maximum Aug 06 02:39:12 58.
14) Thus, visual estimation of CTP penumbra volume by comparing TTP and CBV maps provides important information regarding thrombolytic treatment risk/benefit ratio (Figure 3).
The patient had a good recovery mainly because the deteriorating situation was reversed by salvage of the penumbra and limiting the area of core brain damage.
Theorists suspect that the penumbra is key to keeping a sunspot intact.
Penumbra has a wide range of items, including work by many local craftsmen and women as well as cushions and painted glassware by Sandie.
337) Toward the end of the book, the following wordy conclusions are more confusing than illuminating: "As well as being more commodiously lodged within the erstwhile medical core, and containing a high admixture of graduate physicians, the medical penumbra was thus far more diverse than before.
and move into the outer part of Earth's shadow, also known as the penumbra, at 6:03 p.
Excellent as the translation is, the Penumbra production with its standard rectangular pages and somewhat scholarly appearance is somewhat disappointing after the delightful Finnish production with its square format and fine gray matte paper and broken title extending from back cover to front.
However, she boasts "exhaustive" primary and secondary sources dating as far back as the summer 1982 Penumbra Theater presentation of Black Bart and the Sacred Hills.
Altogether happier is Ray Reader, who has his first success of the season on Penumbra (John Sutcliffe, jr) in the handicap sprint at Sandown.