29 resultados para YÁNEZ COSSÍO, ALICIA, 1929-

em Chinese Academy of Sciences Institutional Repositories Grid Portal


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讨论了光波在水平大气湍流中传输时的情况。计算结果表明自适应光学系统的补偿效果与光波传播路径上的横向风有很大的关系。大气湍流的强度越大, 自适应光学系统的截止频率越高, 横向风的影响也越大。计算结果还表明在相同的r0 或者相同的大气湍流强度下, 球面波所受大气扰动的自适应光学补偿效果受横向风的影响要比平面波的厉害。本文还将理论分析的结果和数值模拟的结果进行了比较, 表明数值模拟结果受横向风的影响比理论分析结果受横向风的影响大。最后, 文中分析了以上现象并对此作出了合理的解释。

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在中性原子的磁囚禁实验中,磁阱线圈的电流噪声会激发磁阱中的原子运动,势必对原子团的温度和寿命产生不可忽视的影响。对于非简谐阱,这种激发具有能量选择特性,它又取决于电流噪声的频谱分布。选择了实验中常用的四极阱为研究对象,用直接模拟蒙特卡罗方法来模拟四极阱中原子运动的参变激发现象,得到了原子温度与原子数损失随激发频率的变化关系,并进一步计算了两个共振峰处原子温度随调制时间和调制深度的变化曲线。此外,还研究了弹性碰撞速率对参变激发过程中原子温度上升的影响。这些结果对四极阱参变激发的实验有较好的参考价值。

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青藏高原地区是我国植物物种多样性和特有性最高的地区,且作为东亚植物区系的一个现代分化中心受世人瞩目。长花马先蒿是青藏高原高山草甸的广布种,其地理分布格局的形成与高原的隆升和气候变迁有着密切关系。因此,对长花马先蒿进行谱系生物地理学研究,有助于探讨青藏高原地区物种快速分化的机制和群体建立过程。 本研究对长花马先蒿11个居群、188个个体的叶绿体DNA trnT-trnF区进行了序列分析,发现该片段的长度变异范围为1441-1472bp。对位排列后的矩阵(含外类群)长1534bp,内类群中含33个碱基替换和 17 个插入/缺失,可分为20种单倍型。11个地理居群的总核苷酸多态性(π)为0.00468,单倍型多态性(Hd)为0.853,居群间的遗传变异(FST)高达88.2%,说明长花马先蒿具有很高的遗传多样性,且居群间发生了强烈遗传分化。 系统发育和遗传多样性分析发现长花马先蒿的20种叶绿体单倍型可归于四个地理单元——川西高海拔地区、川北地区、云南德钦地区及川藏地区。进一步分析发现:4个地理单元间存在着显著的遗传分化, 说明长花马先蒿具有明显的谱系地理分布格局。其中川西高海拔地区的四种主导单倍型构成了系统发育树最基部的一支,而以川西地区为中心、向南扩展至云南的两个居群所包含的几种单倍型均属于比较进化的类型。单倍型的网络关系(Network) 显示出西藏、青海、云南及四川北部的一些单倍型间遗传差异很小,亲缘关系很近。上述结果表明:长花马先蒿群体在冰期后的重新扩张过程主要表现为由南往北的递进式扩散,第四纪冰期气候的反复波动导致了该物种居群随生境变化而不断扩张或收缩,形成了现今的分布格局。初步推测川西地区很可能曾是长花马先蒿在第四纪冰期时的重要避难所,瓶颈效应和奠基者效应对其遗传多样性分布格局有重要影响。

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采用蛋白电泳技术对云南的3种姬鼠的蛋白多态性进行了分析, 共检测遗传座位27个, 发现21个座位存在多态性。根据蛋白多态性的数据对研究对象进行了遗传分化关系的探讨, 并得到了一棵无根系统树。

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泉水鱼(Pseudogyrinocheilus prochilus)是我国特有的一种鲤科鱼类,它广泛分布于宜昌以上长江上游干流、长江在四川境内的支流和乌江中,常栖息于山溪溪流及具流水的岩洞中;以舔刮底栖生物为食。它具有十分独特的口唇结构。不少学者对其分类作过研究,Sauvage et Dabry(1880)将泉水鱼认作一个种,置于Discognathus属中,名之为D.prochilus;Tchang;(张春霖,1929)将泉水鱼鉴定为两个种,归入Gyrinocheilus属中,命名为G.pellegri

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<正> 复殖吸虫是体内寄生的扁形动物,很多寄生虫学者常把体内寄生作为区分复殖吸虫目与单殖吸虫目的特征之一。但在复殖吸虫目中,亦有少数例外营体外寄生的。目前世界上发现的体外寄生复殖吸虫有三个科(Yamaguti,1971):横形科(Transversotrematidae Yamaguti,1954)、连肠科(Syncoeliidae Odhner,1929)和囊双科(Didymozoidae Poche,1907)。除囊双科外,余二科仅包括少数种类。囊双科和连肠科吸虫主要寄生在海水鱼类的鳃部

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<正> 一.引言沙壳纤毛虫亚目(Tindnnoinea)是一类披有外壳的浮游寡毛类(Oligotricha)原生动物,种类极为繁多。根据郭甫德与肯培尔(Kofoid & Campbell,1929)的统计,此类动物在文献上的记录已超出了1750个种、亚种、变种或型的描述。又据羽田(Hada,1939)的报告,淡水裹的沙壳纤毛虫主要是包括筒壳虫(Tintinnidium)和似铃壳虫(Tintinnopsis)两属,而这两属在科学上有过记录的淡水种类,还祇有10种左右。由此可见,海洋与淡水里的沙壳纤毛虫的种类

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Photoluminescence (PL) and photo induced current transient spectroscopy (PICTS) have been used to study deep levels in semi-insulating (SI) InP prepared by annealing undoped InP in pure phosphorus (PP) and iron phosphide (IP) ambient. Defects are much fewer in IP SI-InP than in PP SI-InP. Deep-level-related PL emission could only be detected in IP SI-InP. The results indicate that Fe diffusion inhibits the thermal formation of a number of defects in annealed InP. A complex defect has been formed in the annealing process in the presence of Fe.

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失效检测是分布式系统的基本可靠性保障技术,它对运行时系统的存活状态进行及时检测.作为网络分布计算环境中的主流中间件,Web应用服务器(Web application server简称WAS)需要提供良好的检测机制,并且要能满足适应性的需求.适应性失效检测要求失效检测器能够根据应用需求和系统环境的变化而动态地改变检测的质量.首先给出了WAS的多层失效检测模型,然后基于失效检测器的服务质量规约,提出了适应性失效检测算法,并设计了一个WAS的适应性失效检测框架.它能够满足动态调整失效检测质量和灵活集成失效检测器的要求.该工作在OnceAS应用服务器中进行了实现,并给出了OnceAS平台上的实验及数据.

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中国科学院知识创新方向性项目(061Z291213) 资助课题

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Theoretical and experimental investigations were performed to show the application of x-ray crystal truncation rod scattering combined with x-ray reflectivity in the measurements of surface roughness and near-surface damage of mechanochemically polished wafers. By fitting the measured crystal truncation rod curves it has been shown that polished wafers are divided into three parts -irregular steps on the surface, a damaged thin layer beneath the surface and a perfect bulk. The results show that the root mean square of the surface roughness of mechanochemically polished Fe-doped and/or S-doped InP wafers is one to two atom layers, and that the lateral correlation length of the surface roughness is about 3000-7500 Angstrom. The thickness of the damaged region is found to be about 1000 atom layers.

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By extending our microscopic model on optical-phonon modes in quantum wells to one-dimensional (1D) quantum-well wires (QWW), the optical displacements and associated electrostatic potentials of optical-phonon modes in 1D QWW are calculated. The modes can be clearly divided into confined LO bulklike, TO bulklike modes, and extended interfacelike modes provided the bulk phonon dispersion is ignored. The character of each type of mode is illustrated with special attention to the interfacelike modes, which are hybrids of longitudinal- and transverse-optical waves from the corresponding bulk materials. Based on the numerical results, approximate analytical formulas for bulklike modes are presented. As in 2D wells, both the optical displacements and Frohlich potentials for the bulklike modes vanish at the interfaces. The finite dispersion of bulk phonons has a more pronounced effect on the 1D phonon modes because interfacelike modes show mixed characteristics of 2D interface and bulklike modes.