μ-PD法蓝宝石纤维晶体生长中传热传质的数值模拟

在μ-PD法纤维蓝宝石单晶生长中,利用Comsol软件数值分析了陶瓷管开裂现象、熔体对流和磁场分布.结果表明,试验中陶瓷管保温层总是在距底部0.03 m处断裂,数值模拟发现该处为温度和Von Mises应力最高点位置,验证了数值模拟的准确性;适当增大陶瓷管保温层厚度有利于降低陶瓷管温度,从而降低其开裂概率;熔体对流中Marangoni对流占主导,浮力对流可忽略;磁场分布能够满足μ-PD法蓝宝石晶体生长需求,“趋肤效应”使最高温度位于铱坩埚最上端.     

磁珠富集法筛选池蝶蚌微卫星分子标记

通过磁珠富集的方法分离池蝶蚌(Hyriopsis Schlegelii)的微卫星分子标记。将池蝶蚌基因组DNA酶切,连接Brown接头,采用PCR技术富集,与探针杂交后杂交复合物结合到包被有链霉亲和素的磁珠上,再将这些片段洗脱,PCR扩增,克隆构建含有微卫星片段的"基因组文库",所得到的阳性克隆进行测序。从所获得的212个阳性克隆中选取110个进行测序,其中54.5%含有微卫星序列,80%的重复序列重复数在10以上,微卫星序列中21.4%为完美型。除探针中使用的AC、AG等重复单元外,还观察到CT、GA、ATG等重复序列。设计获得60对微卫星引物,合成其中的30对经PCR筛选,结果有10对引物扩增出多态性条带。该实验表明:磁珠富集法是获得池蝶蚌微卫星分子标记的一种有效的方法,同时,制备出的微卫星标记可为今后研究池蝶蚌分子遗传多样性提供有用的遗传标记。     

Quantum tunneling of ultracold atoms in optical traps

We review our theoretical advances in quantum tunneling of BoseEinstein condensates in optical traps and in microcavities. By employing a real physical system, the frequencies of the pseudo Goldstone modes in different phases between two optical traps are studied respectivdy, which are tile crucial feature of the non-Abelian Joseptmon effect. When the optical lattices are under gravity, we investigate the quantum tummling in the ＂Wannier-Stark localization＂ regime and ＂Lan（lau Zener tunneling＂ regime. We finally get the total decay rate and the rate is valid over the entire range of temperatures. At high temperatures, we show how the decay rate reduces to the appropriate results for the classical thermal activation. At hltermediate temperatures, the results of tile total decay rate are consistent with the thermally assisted tunneling. At low temperatures, we obtain the pure quantmn tunneling ultimately. And we study the alternating-current and direct-current （ac and de） photonic 3osephson effects in two weakly linked microcavities containing ultracold two-level atones, which allows for direct observation of the effects. This enables new investigations of the effect of maw-body physics in strongly coupled atom-cavity systems and provides a strategy for constructing novel interference devices of coherent photons. In addition, we propose the experimental protocols to observe these quantmn tunneling of Bose- Einstein condensates.     

地球重力场空间探测: 回顾与展望

地球重力场的科学数据在地球测绘学、冰川学、陆地水循环、固体地球物理、灾害监控及国防军事等领域具有重要应用价值. 美、德合作研制的地球重力场反演与气候实验(gravity recovery and climate experiment, GRACE)卫星, 有力地推动了地球重力场测量、反演和应用. 为进一步提高重力卫星科学数据的时、空分辨率, 扩展应用领域, 中国及欧美等国都考虑发射升级的重力卫星, 即后GRACE 计划(GRACE-follow-on). 本文将简单回顾重力卫星的发展历程, 介绍重力卫星的数据采集技术和反演方法, 亦着重阐述后GRACE计划的测量方法学、关键技术及预期结果.      

基于低空成像高光谱系统探测植被日光诱导叶绿素荧光

植被叶绿素荧光与光合作用关系密切,被认为是光合作用的有效探针。该研究利用成像高光谱传感器和无人飞艇构建了一套适用于低空叶绿素荧光探测的系统。针对低空叶绿素荧光探测中,太阳下行辐射光谱难以获取的情况,基于已有的aFLD方法,提出一种新的叶绿素荧光提取方法a3FLD,该方法利用了非荧光发射体,且考虑植被反射率在夫琅和费线附近的变化。通过模拟数据以及实测数据对两种提取结果进行了比较。模拟数据分析结果显示：当地物的反射率在夫琅和费线附近存在一定的变化时,a3FLD计算得到的荧光值误差小于aFLD,地物反射率变化越大,a3FLD的改进越明显。对低空高光谱影像数据的分析显示：aFLD和a3FLD提取不同植被的日光诱导叶绿素荧光相对大小关系相一致,与作物所处的生长阶段吻合。但aFLD荧光提取值比a3FLD高15%左右。aFLD的结果中有部分非荧光发射体得到较强荧光,a3FLD能改进此问题。结果显示,利用该系统和方法能够成功地提取到植被叶绿素荧光,且所提出a3FLD方法提取的结果优于aFLD方法。     

核壳结构AgInS2@ZnS量子点的合成及荧光性能

合成了一种新型核壳结构的AgInS₂@ZnS量子点并研究了其荧光性能. AgInS₂@ZnS的合成包括以变性牛血清白蛋白(dBSA)为稳定剂水相法构建AgInS₂核以及形成ZnS壳两部分. 考察了配方和工艺条件对该量子点荧光性能的影响, 并采用X射线粉末衍射(XRD)等手段对制备的纳米粒子进行了表征. 结果表明, AgInS₂@ZnS是一种核壳结构的纳米物质, 其粒径介于5~7 nm之间, 荧光量子产率达35.3%.     

激光辐照对二茂铁掺杂单壁碳纳米管的影响

以单壁碳纳米管和二茂铁为原料, 采用气相扩散法合成填充率较高的二茂铁掺杂单壁碳纳米管(Fc@SWNTs)的复合材料. 考察激光辐射对样品的影响, 结果表明, 当激光功率达到20 mW时, 对样品进行10 s辐照, 样品的拉曼光谱出现了稳定的新峰. 对比分析发现, 二茂铁在激光辐照后形成了碳化铁, 同时部分碳源转化成碳管形成了双层碳管. 表明碳化铁是二茂铁裂解向内层碳管转化的中间产物.     

无辐射跃迁理论进展

在本文中,我们将介绍运用第一性原理计算包含非谐效应或势能面锥形交叉情况下内转换速率的最新工作。我们同时计算了包含非谐效应的分子吸收和发射光谱,以检验量子化学方法计算得到势能面的准确性。势能面的锥形交叉对内转换过程的影响是学界广泛关注的焦点。本文将介绍如何在内转换速率计算的过程中考虑势能面锥形交叉的影响,并将之运用于吡嗪分子。本文运用绝热近似理论处理了另外一个重要的无辐射过程,分子的振动驰豫过程,并将这个理论应用于水二聚体和苯胺的振动弛豫速率的计算。     

Linear and Nonlinear Optical Properties of Novel Multi-branched Oligomers

We investigate the fluorene-vinylene unit dependent photo-physical properties of multi-branched truxene based oligomers (Tr-OFV_n, n=1-4) employing steady-state absorption and emission spectroscopy, transient absorption spectroscopy, two-photon fluorescence, and z-scan technique. The results show that the increasing of fluorene-vinylene unit leads to a red-shift in the spectra of absorption and fluorescence, and shortens the excited state lifetime. Meanwhile, two-photon fluorescence efficiency and two-photon absorption cross section of truxene based oligomers gradually enhance in company with the extension of π-conjugated length. In addition, the values of two-photon absorption cross section modeled on the sum-over-state approach agree well with the experimental ones. The results indicate multi-branched truxene based oligomers bearing oligo(fluorene-vinylene) arms are promisingorganic materials for two-photon applications.     

Single DNA Condensation Induced by Hexammine Cobalt with Molecular Combing

We investigated the interaction between DNA and hexammine cobalt III [Co(NH₃)₆]³⁺ by a simple molecular combing method and dynamic light scattering. The average extension of ?λ-DNA-YOYO-1 complex is found to be 20.9 μm, about 30% longer than the contour length of the DNA in TE buffer (10 mmol/L Tris, 1 mmol/L EDTA, pH=8.0), due to bis-intercalation of YOYO-1. A multivalent cation, hexammine cobalt, is used for DNA condensation. We find that the length of DNA-[Co(NH₃)₆]³⁺ complexes decrease from 20.9 μm to 5.9 μm as the concentration of the [Co(NH₃)₆]³⁺ vary from 0 to 3 μmol/L. This observation provides a direct visualization of single DNA condensation induced by hexammine cobalt. The results from the molecular combing studies are supported by dynamic light scattering investigation, where the average hydrodynamic radius of the DNA complex decreases from 203.8 nm to 39.26 nm under the same conditions. It shows that the molecular combing method is feasible for quantitative conformation characterization of single bio-macromolecules.