GRE阅读高频机经原文30：Supernovae&Obscuratbydust

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GRE阅读高频机经原文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词汇精选之乡村,田园

　　bucolic　adj.乡村的，牧羊的

　　rural　adj.乡村的

　　rustic　adj.乡村的，乡土气的

　　rusticate　　n.过乡间生活

　　predial　adj　土地的，乡村的

　　campestral　adj　田野的，农村的

　　paysage　n　乡村景色，风景

　　pastoral　adj.田园生活的，宁静的

　　eclogue　n.田园诗，牧歌

　　idyll　n.田园生活，田园诗

　　madrigal　n.合唱曲，情诗，牧歌

　　boor　n.举止粗野的人，乡下人

　　corny　adj.平谈无奇的，乡巴佬的

　　yeoman　n.自耕农，乡下人

　　yokel　n.乡巴佬

　　bumpkin　n　粗人，乡巴佬

　　hillbilly　n　乡下人，乡巴佬

　　GRE阅读词汇精选之演说

　　discourse　n.演讲，论述

　　disquisition　n.长篇演讲，专题论文

　　oration　n.正式演说，演讲

　　text　n.(演讲等)原文

　　oratory　n　演讲术，祈祷室，雄辩的演讲

　　forum　n.辩论的场所，讲坛

　　podium　n.讲坛,指挥台

　　rostrum　n　讲坛

　　rostrum　n　讲坛,演讲坛

　　elocution　n.演说术

　　eloquent　adj.雄辩的,演说动人的

　　extemporize　v.即席演说

　　heroics　n.装腔作势的演说或行为

　　monologue　n.独白，个人长篇演说

　　screed　n.冗长的演说，长篇大论的文章

　　diatribe　n.(口头或书面猛烈的)抨击，抨击性演说

　　harangue　n.长篇演说

　　tirade　n.长篇的攻击性演说

　　valediction　n.告别演说，告别词

　　talkthon　n　冗长的讨论或演说

　　GRE阅读词汇精选之各种剂

　　analgesic　n.镇痛剂，adj.止痛的

　　anesthetic　n.麻醉剂

　　antiseptic　n.杀菌剂，adj　防腐的

　　astringent　adj.止血的，收缩的　　n.收缩剂，止血剂

　　catalyst　n.催化剂，促使事情发展的因素

　　coagulant　n.凝结剂

　　desiccant　n.干燥剂

　　detergent　a.净化的，n.清洁剂

　　disinfectant　n.消毒剂

　　dose　n.(药)剂量，一剂

　　emollient　n.润肤剂

　　haemostat　n.止血器，止血剂

　　leaven　n.发酵剂，影响力v.发酵，影响或改变

　　lubricant　n.润滑剂

　　nebula　n.星云，喷雾剂

　　opiate　n.安眠药，鸦片制剂

　　overdose　n.(药物)过度剂量

　　pesticide　n.杀虫剂

　　placebo　n.安慰剂

　　polish　v.把…擦光亮n.上光剂,(态度等)优雅

　　preservative　adj.n.防腐的,防腐剂

　　reagent　n.试剂(导致化学反应)

　　sedative　adj.n.(药物)镇静的，镇静剂

　　solvent　adj.有偿债能力的，n.溶剂

　　stimulant　n.兴奋剂，刺激物

　　tranquillizer　n.镇定剂

　　styptic　adj　止血的,n　止血剂

　　deodorant　n　除臭剂，防臭药

　　precipitant　n　　恋　剂，adj　突如其来的

　　obtundent　adj　止痛的n　缓和剂

　　abrasive　n　研磨剂a　研磨的

　　antihistamine　n　抗组胺剂

　　inhibitor　n　止氧剂

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