WordNet

of or pertaining to the region of partial shadow around an umbra
of questionable or minimal quality; "borderline grades"; "marginal writing ability" (同)marginal
a line determining the limits of an area (同)edge, bound
the line or plane indicating the limit or extent of something (同)bound, bounds
a fringe region of partial shadow around an umbra

PrepTutorEJDIC

(…の)国境線,境界線《+『of』(『between』)+『名』[+『and』+『名』]》 / 国境線上の,境界線上の / どっちつかずの,不明確な
『境界線』,境(border) / 限界
(日食・月食の)半影 / (太陽の黒点周囲り)半影部 / (絵画で)明暗(濃淡)の境目

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/03/14 12:21:21」(JST)

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Shadows

Umbra, penumbra, and antumbra, for a lunar eclipse

Umbra (A) and penumbra (B)

The umbra, penumbra and antumbra are three distinct parts of a shadow, created by any light source after impinging on an opaque object. For a point source only the umbra is cast.

These names are most often used for the shadows cast by celestial bodies, though they are sometimes used to describe levels of darkness, such as in sunspots.

Umbra

Umbra, penumbra and antumbra formed through windows and shutters

The umbra (Latin for "shadow") is the innermost and darkest part of a shadow, where the light source is completely blocked by the occluding body. Such an opaque object does not let light through it. An observer in the umbra experiences a total eclipse. The umbra of a round body occluding a round light source forms a right circular cone; to a viewer at the cone's apex, the two bodies are equal in apparent size. The distance from the Moon to the apex of its umbra is roughly equal to that between the Moon and Earth. Because the Earth is 3.7 times wider than the Moon, its umbra extends correspondingly farther, roughly 1.4 million kilometers.^[1]

Penumbra

The penumbra (from the Latin paene "almost, nearly" and umbra "shadow") is the region in which only a portion of the light source is obscured by the occluding body. An observer in the penumbra experiences a partial eclipse. An alternative definition is that the penumbra is the region where some or all of the light source is obscured (i.e., the umbra is a subset of the penumbra). For example, NASA's Navigation and Ancillary Information Facility defines that a body in the umbra is also within the penumbra.^[2]

Earth's shadow, to scale, showing the extent of the umbral cone beyond the Moon's orbit (yellow dot, also to scale)

Antumbra

The antumbra (from Latin ante, "before") is the region from which the occluding body appears entirely contained within the disc of the light source. An observer in this region experiences an annular eclipse, in which a bright ring is visible around the eclipsing body. If the observer moves closer to the light source, the apparent size of the occluding body increases until it causes a full umbra.

References

^ "Lecture 9: Eclipses of the Sun & Moon". ohio-state.edu. Retrieved July 16, 2015.
^ Event Finding Subsystem Preview Navigation and Ancillary Information Facility.

UpToDate Contents

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English Journal

Alteplase versus tenecteplase for thrombolysis after ischaemic stroke (ATTEST): a phase 2, randomised, open-label, blinded endpoint study.

Huang X1, Cheripelli BK1, Lloyd SM2, Kalladka D1, Moreton FC1, Siddiqui A3, Ford I2, Muir KW4.
The Lancet. Neurology.Lancet Neurol.2015 Apr;14(4):368-76. doi: 10.1016/S1474-4422(15)70017-7. Epub 2015 Feb 26.
BACKGROUND: In most countries, alteplase given within 4·5 h of onset is the only approved medical treatment for acute ischaemic stroke. The newer thrombolytic drug tenecteplase has been investigated in one randomised trial up to 3 h after stroke and in another trial up to 6 h after stroke in patien
PMID 25726502

Defining the ischemic penumbra using magnetic resonance oxygen metabolic index.

An H1, Ford AL1, Chen Y1, Zhu H1, Ponisio R1, Kumar G1, Shanechi AM1, Khoury N1, Vo KD1, Williams J1, Derdeyn CP1, Diringer MN1, Panagos P1, Powers WJ1, Lee JM2, Lin W2.
Stroke; a journal of cerebral circulation.Stroke.2015 Apr;46(4):982-8. doi: 10.1161/STROKEAHA.114.008154. Epub 2015 Feb 26.
BACKGROUND AND PURPOSE: Penumbral biomarkers promise to individualize treatment windows in acute ischemic stroke. We used a novel magnetic resonance imaging approach that measures oxygen metabolic index (OMI), a parameter closely related to positron emission tomography-derived cerebral metabolic rat
PMID 25721017

Preconditioning cortical lesions reduce the incidence of peri-infarct depolarizations during focal ischemia in the Spontaneously Hypertensive Rat: interaction with prior anesthesia and the impact of hyperglycemia.

Zhao L1, Nowak TS Jr1.
Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.J Cereb Blood Flow Metab.2015 Mar 11. doi: 10.1038/jcbfm.2015.37. [Epub ahead of print]
The relationship between peri-infarct depolarizations (PIDs) and infarction was investigated in a model of preconditioning by cortical freeze lesions (cryogenic lesions, CL) in the Spontaneously Hypertensive Rat. Small (< 5 mm3) lesions produced 24 hours before permanent focal ischemia were p
PMID 25757750