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GRE閱讀高頻機(jī)經(jīng)原文30：Supernovae&Obscurat by dust

　　Supernovae & Obscuration by dust

　　Recently, significant progress has been made by using Type Ia supernovae as ``standardizable candles''. Supernovae are rare - perhaps a few per century in a Milky-Way-sized galaxy - but modern telescopes allow observers to probe very deeply into small regions of the sky, covering a very large number of galaxies in a single observing run. Supernovae are also bright, and Type Ia's in particular all seem to be of nearly uniform intrinsic luminosity (absolute magnitude , typically comparable to the brightness of the entire host galaxy in which they appear)They can therefore be detected at high redshifts , allowing in principle a good handle on cosmological effects .

　　Obscuration by dust is the leading concern about the reliability of the supernova results. Ordinary astrophysical dust does not obscure equally at all wavelengths, but scatters blue light preferentially, leading to the well-known phenomenon of ``reddening''. Spectral measurements by the two supernova teams reveal a negligible amount of reddening, implying that any hypothetical dust must be a novel ``grey'' variety. This possibility has been investigated by a number of authors . These studies have found that even grey dust is highly constrained by observations: first, it is likely to be intergalactic rather than within galaxies, or it would lead to additional dispersion in the magnitudes of the supernovae; and second, intergalactic dust would absorb ultraviolet/optical radiation and re-emit it at far infrared wavelengths, leading to stringent constraints from observations of the cosmological far-infrared background. Thus, while the possibility of obscuration has not been entirely eliminated, it requires a novel kind of dust which is already highly constrained (and may be convincingly ruled out by further observations).

　　GRE詞匯精選之鄉(xiāng)村,田園

　　bucolic　adj.鄉(xiāng)村的，牧羊的

　　rural　adj.鄉(xiāng)村的

　　rustic　adj.鄉(xiāng)村的，鄉(xiāng)土氣的

　　rusticate　　n.過鄉(xiāng)間生活

　　predial　adj　土地的，鄉(xiāng)村的

　　campestral　adj　田野的，農(nóng)村的

　　paysage　n　鄉(xiāng)村景色，風(fēng)景

　　pastoral　adj.田園生活的，寧?kù)o的

　　eclogue　n.田園詩(shī)，牧歌

　　idyll　n.田園生活，田園詩(shī)

　　madrigal　n.合唱曲，情詩(shī)，牧歌

　　boor　n.舉止粗野的人，鄉(xiāng)下人

　　corny　adj.平談無奇的，鄉(xiāng)巴佬的

　　yeoman　n.自耕農(nóng)，鄉(xiāng)下人

　　yokel　n.鄉(xiāng)巴佬

　　bumpkin　n　粗人，鄉(xiāng)巴佬

　　hillbilly　n　鄉(xiāng)下人，鄉(xiāng)巴佬

　　GRE閱讀詞匯精選之演說

　　discourse　n.演講，論述

　　disquisition　n.長(zhǎng)篇演講，專題論文

　　oration　n.正式演說，演講

　　text　n.(演講等)原文

　　oratory　n　演講術(shù)，祈禱室，雄辯的演講

　　forum　n.辯論的場(chǎng)所，講壇

　　podium　n.講壇,指揮臺(tái)

　　rostrum　n　講壇

　　rostrum　n　講壇,演講壇

　　elocution　n.演說術(shù)

　　eloquent　adj.雄辯的,演說動(dòng)人的

　　extemporize　v.即席演說

　　heroics　n.裝腔作勢(shì)的演說或行為

　　monologue　n.獨(dú)白，個(gè)人長(zhǎng)篇演說

　　screed　n.冗長(zhǎng)的演說，長(zhǎng)篇大論的文章

　　diatribe　n.(口頭或書面猛烈的)抨擊，抨擊性演說

　　harangue　n.長(zhǎng)篇演說

　　tirade　n.長(zhǎng)篇的攻擊性演說

　　valediction　n.告別演說，告別詞

　　talkthon　n　冗長(zhǎng)的討論或演說

　　GRE閱讀詞匯精選之各種劑

　　analgesic　n.鎮(zhèn)痛劑，adj.止痛的

　　anesthetic　n.麻醉劑

　　antiseptic　n.殺菌劑，adj　防腐的

　　astringent　adj.止血的，收縮的　　n.收縮劑，止血?jiǎng)?/p>

　　catalyst　n.催化劑，促使事情發(fā)展的因素

　　coagulant　n.凝結(jié)劑

　　desiccant　n.干燥劑

　　detergent　a.凈化的，n.清潔劑

　　disinfectant　n.消毒劑

　　dose　n.(藥)劑量，一劑

　　emollient　n.潤(rùn)膚劑

　　haemostat　n.止血器，止血?jiǎng)?/p>

　　leaven　n.發(fā)酵劑，影響力v.發(fā)酵，影響或改變

　　lubricant　n.潤(rùn)滑劑

　　nebula　n.星云，噴霧劑

　　opiate　n.安眠藥，鴉片制劑

　　overdose　n.(藥物)過度劑量

　　pesticide　n.殺蟲劑

　　placebo　n.安慰劑

　　polish　v.把…擦光亮n.上光劑,(態(tài)度等)優(yōu)雅

　　preservative　adj.n.防腐的,防腐劑

　　reagent　n.試劑(導(dǎo)致化學(xué)反應(yīng))

　　sedative　adj.n.(藥物)鎮(zhèn)靜的，鎮(zhèn)靜劑

　　solvent　adj.有償債能力的，n.溶劑

　　stimulant　n.興奮劑，刺激物

　　tranquillizer　n.鎮(zhèn)定劑

　　styptic　adj　止血的,n　止血?jiǎng)?/p>

　　deodorant　n　除臭劑，防臭藥

　　precipitant　n　　戀　劑，adj　突如其來的

　　obtundent　adj　止痛的n　緩和劑

　　abrasive　n　研磨劑a　研磨的

　　antihistamine　n　抗組胺劑

　　inhibitor　n　止氧劑

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