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]
References in periodicals archive ?
Thus, the following sentence is an instance of a penumbral connection:
Slotboom et al., "Factors that determine penumbral tissue loss in acute ischaemic stroke," Brain, vol.
The penumbral shading becomes stronger as the minutes advance and the Moon moves deeper in.
Moreover, there was no significant difference between embolectomy and standard medical care in patients with penumbral pattern versus nonpenumbral pattern.
The group continued to develop and was type Eac on Aug 14 with the leading and middle penumbral sunspots being the largest.
Three lunar eclipses occur in 2013: a partial eclipse (on April 25) and two penumbral eclipses (May 25 and October 18).
Here is the ephemeris for the January 10,1 BC eclipse: First penumbral contact: 10:31 p.m.
(When the developer is applied, these expired papers turn black.) Rossiter made one group, a series of tornado-like forms that fade into penumbral regions rippling with sepia and gray, by pouring the developer--an action that recalls Morris Louis, as Matthew Witkovsky noted in Artforum this past March.
Natural light creates striking images, though reduced clarity in largely penumbral interiors can be wearying.
Its penumbral phase will start at 10.45 pm on December 31 and end at 3 am on January 1, 2010.
New Delhi, Feb 9 (ANI): A penumbral eclipse on a full moon day will be visible throughout country today.
Chapters address specific questions such as the role of glutamate/NMDA, the mechanisms of penumbral cells, the importance of intermittent hypoxia, and gene regulation under stressful conditions.