979 resultados para Ely, Ezra Stiles, 1786-1861.
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Nesse trabalho apresentamos a função e determinamos a natureza das convenções e hipóteses para os fundamentos científicos segundo a corrente convencionalista que surgiu na França na virada do século XIX para o XX, composta por Henri Poincaré, Pierre Duhem e Édouard Le Roy. Além disso, analisamos a relação que as convenções e hipóteses podem estabelecer com teses metafísicas através dos critérios utilizados pelos cientistas para determinar a preferência por certas teorias. Para isso, promovemos uma interpretação imanente das obras publicadas entre 1891 e 1905. Como resultado, revelamos que os autores, apesar de serem classificados como pertencentes a uma mesma corrente, não possuem apenas posições comuns, mas também divergências. Poincaré e Le Roy concordam que as convenções geométricas são escolhidas de acordo com o critério de conveniência. Contudo, eles discordam sobre o valor que a conveniência agrega ao conhecimento científico. Em relação aos fenômenos naturais, os três autores concordam que a realidade não pode ser descrita univocamente por um mesmo conjunto de convenções e hipóteses. Porém, Poincaré e Duhem acreditam que há critérios que tornam umas teorias mais satisfatórias que outras. Analisamos os critérios experimentais, racionais e axiológicos que justificam a satisfação dos cientistas com certas teorias e apontamos como estes critérios se relacionam com a metafísica. Concluímos que os convencionalistas, mesmo que cautelosamente e de modo implícito, buscaram se aproximar da metafísica com o intuito de justificar a própria atividade científica.
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古民族植物学(Paleoethnobotany)在我国尚属一个比较年轻的学科,其主要研究对象是先民们所栽培或利用过的植物遗存(Plant remains),目的在于揭示古代人们对食物的选择,栽培植物的起源,早期农业的出现以及居址周围的自然与生态环境。吐鲁番地区降水稀少。干燥的环境,使得考古遗址中的植物遗存得以完好的保存。本论文首次对吐鲁番洋海墓地(2500 B. P. )的包括木材、果实、种子、茎杆、叶片等在内的植物遗存进行了系统的研究,依此分析了当时的植被及环境,并对与当时的土著居民密切相关的植物类群进行了详细研究。 研究表明,吐鲁番洋海墓地植物群包括木材、禾本科粮食作物、杂草及其它植物共18 种。其中我们详细研究了14 种,隶属于7 科14 属,它们分别为禾本科黍属中的黍(Panicum miliaceum),大麦属中的青稞(Hordeum vulgare var. nudum),小麦属中的普通小麦(Triticum aestivum),芦苇属的芦苇(Phragmites australis),虎尾草属的虎尾草(Chloris virgata),小獐毛属的小獐毛(Aeluropus pungens var. pungens),稗属的稗子(Echinochloa crusgali),大麻科大麻属中的大麻(Cannabis sativa),紫草科紫草属中的小花紫草(Lithospermum officinale), 豆科槐属中的苦豆子(Sophora alopecuroides var. alopecuroides),茄科枸杞属中的黑果枸杞(Lycium ruthenicum),松科云杉属中的云杉属未定种(Picea sp.), 杨柳科杨属的胡杨(Popules euphratica)及柳属未定种(Salix sp.)。研究表明,这些植物遗存渗透到古洋海人生活的方方面面。其中,粮食作物为可能以黍为主,以普通小麦及青稞为辅;用以作装饰的为小花紫草的小坚果;可能与其原始宗教及医药相关的为大麻;与建筑相关的植物有芦苇、黑果枸杞、云杉(Picea sp.)、胡杨及柳(Salix sp.)等;与当地居民意义不大的杂草有稗子、苦豆子、小獐毛、虎尾草等。其中,大麻及小花紫草遗存的出土意味着当时的土著居民对当地的植物已经有了很高的认识水平;黍、青稞及普通小麦的出土意味着他们可能与东西方文化均有接触,为东西方文明的交融起了桥梁作用;所出土的部份植物如小獐毛、小花紫草、柳、苦豆子,尤其是稗子、芦苇及香蒲属植物等都属于喜湿植物。这说明,在当时的洋海墓地周边环境与今天相似,亦为一块植被丰富的绿洲,其中可能有大面积的湿地。
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EXTRACT (SEE PDF FOR FULL ABSTRACT): We examined atmospheric circulation conditions conducive to occurrence of winter floods that exceed the 10-year peak discharge on rivers in six hydroclimatic subregions in Arizona, southern Utah, Nevada, and California. ... This relationship between flooding and broad-scale atmospheric patterns in the modern record will aid in paleoclimatic interpretations of paleoflood records over the last few thousand years.
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Fifteen species of polychaete worms, belonging to order Sabellida, are described from the Karachi coast. Of these 10 are new records for Pakistan: Hydroides albiceps (Grube, 1870), H. exaltatus (Marenzellar, 1885), Protula sp. Spirobranchus tetraceros (Schmarda, 1861), Vermiliopsis infundibulum glandigera group, Demonax sp. and Bispira cf tricyclia (Schmarda, 1861).
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本发明属生物医学技术领域,具体地说,涉及普罗托品在制备治疗老年性痴呆症药物中的应用。本发明选用从滇产植物紫金龙中用现有技术提取的纯天然产物普罗托品,通过用普罗托品对小鼠记忆获得障碍、胆碱酯酶、小鼠神经细胞钠、钾和钙离子通道的影响的研究,表明普罗托品具有胆碱酯酶抑制作用和非选择性离子通道阻断作用,即具有胆碱酯酶抑制剂、吡咯烷酮类化合物和银杏叶提取物的优点,对老年性痴呆症等各种记忆障碍会有更好的治疗作用。普罗托品具有作为制备治疗老年性痴呆症等各种记忆障碍药物的用途。
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Phylogeographical analyses on Sinocyclocheilus grahami samples from seven localities within the Lake Dianchi Basin in China were conducted to explore the main factors shaping population structure within this species. Phylogenetic and network analyses reve
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Sustainable aquaculture in Asia is discussed, considering in particular the loss of mangroves associated with the rapid increase in production of cultured shrimp. Southeast Asia's development and population growth brought non-sustainable exploitation of its coastline; the destruction has increased through the years as development proceeded and the international markets entered the scenario. An outline is given of the current status of mangroves in some Asian countries. Some worldwide remedies for sustainable aquaculture are described.
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改变微藻的捕光色素系统比例被认为是提高其光合作用效率的有效途径,但对其基本原理尚不清楚.以空间飞行后分离的微藻突变株为材料,通过对其生长、光合放氧、色素比例、低温荧光发射和电子传递速率等的研究发现,微藻突变株的捕光色素比例改变引起的光能高效传递和利用,有可能是引起其光合作用效率提高及生长加快的原因.
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In this paper we study the optimization of interleaved Mach-Zehnder silicon carrier depletion electro-optic modulator. Following the simulation results we demonstrate a phase shifter with the lowest figure of merit (modulation efficiency multiplied by the loss per unit length) 6.7 V-dB. This result was achieved by reducing the junction width to 200 nm along the phase-shifter and optimizing the doping levels of the PN junction for operation in nearly fully depleted mode. The demonstrated low FOM is the result of both low V(π)L of ~0.78 Vcm (at reverse bias of 1V), and low free carrier loss (~6.6 dB/cm for zero bias). Our simulation results indicate that additional improvement in performance may be achieved by further reducing the junction width followed by increasing the doping levels.
Resumo:
We design, optimize and demonstrate a highly efficient carrier-depletion silicon Mach-Zehnder modulator with very low VπL of ~0.2Vcm. Design consideration, fabrication process and experimental results will be presented. © OSA 2013.