Magnetic properties of two double‐layer structures built from hydroxy­naphthoic acids and manganese

Double‐layer structures consisting of alternating polar and non‐polar layers have been prepared using Mn²⁺ ions and o‐hydroxy­naphthoic acids. The polar layers contain the Mn²⁺ ions, carboxylate groups, hydr­oxy groups and water mol­ecules. The non‐polar layers are built up from the naphthalene moieties. In catena‐poly[[diaqua­manganese(II)]bis­(μ‐3‐hy­droxy‐2‐naphthoato‐κ²O:O′)] (also called manganese 3‐hy­droxy‐2‐naphthoate dihydrate), [Mn(C₁₁H₇O₃)₂(H₂O)₂]_n, (I), the Mn²⁺ ions are connected by carboxylate groups to form two‐dimensional networks. This compound shows distinct antiferromagnetic inter­actions and long‐range ordering at low temperature. In contrast, tetra­aqua­bis(1‐hydr­oxy‐2‐naph­thoato‐κO)manganese(II), [Mn(C₁₁H₇O₃)₂(H₂O)₄], (II), which lacks a close linkage between the Mn²⁺ ions, reveals purely paramagnetic behaviour. In (II), the Mn²⁺ ion lies on an inversion centre.     

图像深度估计的光学微分方法

讨论了光学微分方法在图像深度估计问题中的应用。基于线性成像理论对Farid提出的光学微分模型进行了推广,即用于图像深度估计的两幅图像在成像过程中可以满足任意阶的线性微分关系。此模型拓宽了光学微分的概念,使两次成像之间关系有了更多的光学微分形式。围绕如何选择合适的光学微分关系以使系统的整体性能达到最优,分析了光学成像系统的参量对于图像深度估计的精度以及纵向分辨力的影响,并且对光学微分方法中的关键光学元件—光学掩模板的构建方法及优化问题也作了初步的探讨。     

基于敏感Fabry-Perot腔光纤角位移传感器的原理与设计

提出了一种全角度并且可以连续测量微小角位移(秒级）的新型光纤角位移传感器.利用微小光学谐振腔的基本理论,主要是基于光学法布里-珀罗(Fabry-Perot）腔的基本原理研究特定光波下光强度的变化与角位移的线性变化关系,利用光纤技术、敏感技术融合微机械技术研发而成.适合于一些特定领域中对角位移的精确测量.     

1,2‐, 1,7‐ and 1,12‐Dicarba‐closo‐dodecaborane(12) Derivatives Revisited by 13C NMR Spectroscopy and DFT Calculations. First Observation of Isotope‐Induced Chemical Shifts 1Δ10/11B(13C), and the Signs and Magnitudes of Coupling Constants 1J(13C,13C) and 1J(13C,11B)

The origin of broadening of ¹³C(carborane) NMR signals of 1,2‐, 1,7‐ and 1,12‐dicarba‐closo‐dodecaboranes(12) and several diphenylsilyl derivatives has been examined in detail and could be traced only partially to unresolved ¹³C–¹¹B spin‐spin coupling. Other contributions to the line widths arise from ¹³C–¹H dipole‐dipole interactions and, in particular, from isotope‐induced chemical shifts ¹Δ^10/11B(¹³C), observed here for carboranes for the first time. In the case of 1‐diphenylsilyl‐1,2‐dicarba‐closo‐dodecaborane(12), the coupling constant ¹J(¹³C,¹³C) = 9.3 Hz was measured in natural abundance of ¹³C. The small value of this coupling constant and its negative sign is predicted by calculations based on optimised structures [B3LYP/6‐311+G(d,p) level of theory] of the parent carboranes and 1‐silyl‐1,2‐dicarba‐closo‐dodecaborane(12) as a model compound [calcd. ¹J(¹³C,¹³C) = –10.5 Hz]. Calculated coupling constants ¹J(¹³C,¹¹B) are small (<7 Hz), in contrast to published assumptions, and of either sign, whereas ¹J(¹¹B,¹¹B) are all positive and range up to 15 Hz.     

Fulvalenediyl-bridged heterobimetallic complexes consisting of sandwich and half-sandwich compounds with early-late transition metals

A straightforward synthesis methodology for the preparation of heterobimetallic [(η⁵-C₅H₅)(η⁵-C₅H₄-C₅Me₄)M] (3a, M = Fe; 3b, M = Ru) and [(η⁵-C₅H₅)((μ-η⁵:η⁵-C₅H₄-C₅Me₄)TiCl₃)M] (4a, M = Fe; 4b, M = Ru) in which early and late transition metals are connected by a fulvalenediyl bridge is reported.The structures of molecules 3b and 4a in the solid state are discussed. Most noteworthy in 4a is the exo arrangement of the iron and titanium atoms coordinated by the fulvalenediyl unit which itself is twisted with a dihedral angle between the joined cyclopentadienyl rings of 19.33(9)°. Electrochemical, UV/Vis/NIR spectroscopic and spectroelectrochemical experiments on 4a and Cp∗TiCl₃, for comparison, provide evidence for some transfer of electronic information between the conjoined ferrocene and half-sandwich titanocene trichloride subunits of 4a. Evidence comes from systematic potential shifts and the presence of a fairly intense Fe → Ti charge-transfer absorption band that vanishes upon oxidation and reduction of 4a.     

Survival of charged ρ condensation at high temperature and density

The charged vector ρ mesons in the presence of external magnetic fields at finite temperature T and chemical potential μ have been investigated in the framework of the Nambu-Jona-Lasinio model.We compute the masses of charged ρ mesons numerically as a function of the magnetic field for different values of temperature and chemical potential.The self-energy of the ρ meson contains the quark-loop contribution,i.e.the leading order contribution in 1/N_C expansion.The charged ρ meson mass decreases with the magnetic field and drops to zero at a critical magnetic field eB_c,which indicates that the charged vector meson condensation,i.e.the electromagnetic superconductor can be induced above the critical magnetic field.Surprisingly,it is found that the charged ρ condensation can even survive at high temperature and density.At zero temperature,the critical magnetic field just increases slightly with the chemical potential,which indicates that charged ρ condensation might occur inside compact stars.At zero density,in the temperature range 0.2 — 0.5 GeV,the critical magnetic field for charged ρ condensation is in the range of 0.2 — 0.6 GeV~2,which indicates that a high temperature electromagnetic superconductor might be created at LHC.     

p型掺杂晶体硅的低温液相(001)外延生长研究

为寻求以低成本制备n型太阳电池的pn结,进行了Al-17.6wt;Si合金熔体中(001)n型单晶硅衬底上液相外延生长p型掺杂硅实验.所用方法为垂直浸渍法,实验了过冷恒温生长与回熔处理后连续冷却生长两种模式,过程中体系以流动高纯氩保护.对所得外延生长晶体结构、形貌及所得pn结开路电压进行了分析和测定.结果显示,合金熔体中硅晶体(001)液相外延生长能够实现,但一般呈离散分布的金字塔型岛状生长;只有衬底回熔处理后原位连续降温生长模式可获得连续外延薄膜,之后在其上出现岛状生长,呈现Stranski-Krastanov生长模式.所得连续外延薄膜形成的pn结开路电压比恒温生长所得的提升约100 mV;连续外延薄膜形成后期出现的岛状生长使开路电压明显下降;生长速度提高会使连续降温外延生长pn结开路电压略有降低.     

The 3D characteristics of post‐traumatic syringomyelia in a rat model: a propagation‐based synchrotron radiation microtomography study

Many published literature sources have described the histopathological characteristics of post‐traumatic syringomyelia (PTS). However, three‐dimensional (3D) visualization studies of PTS have been limited due to the lack of reliable 3D imaging techniques. In this study, the imaging efficiency of propagation‐based synchrotron radiation microtomography (PB‐SRµCT) was determined to detect the 3D morphology of the cavity and surrounding microvasculature network in a rat model of PTS. The rat model of PTS was established using the infinite horizon impactor to produce spinal cord injury (SCI), followed by a subarachnoid injection of kaolin to produce arachnoiditis. PB‐SRµCT imaging and histological examination, as well as fluorescence staining, were conducted on the animals at the tenth week after SCI. The 3D morphology of the cystic cavity was vividly visualized using PB‐SRµCT imaging. The quantitative parameters analyzed by PB‐SRµCT, including the lesion and spared spinal cord tissue area, the minimum and maximum diameters in the cystic cavity, and cavity volume, were largely consistent with the results of the histological assessment. Moreover, the 3D morphology of the cavity and surrounding angioarchitecture could be simultaneously detected on the PB‐SRµCT images. This study demonstrated that high‐resolution PB‐SRµCT could be used for the 3D visualization of trauma‐induced spinal cord cavities and provides valuable quantitative data for cavity characterization. PB‐SRµCT could be used as a reliable imaging technique and offers a novel platform for tracking cavity formation and morphological changes in an experimental animal model of PTS.     

硅异质结太阳电池的物理机制和优化设计

硅异质结太阳电池是一种由非晶硅薄膜层沉积于晶硅吸收层构成的高效低成本的光伏器件,是一种具有大面积规模化生产潜力的光伏产品.异质结界面钝化品质、发射极的掺杂浓度和厚度以及透明导电层的功函数是影响硅异质结太阳电池性能的主要因素.针对这些影响因素已经有大量的研究工作在全世界范围内展开,并且有诸多研究小组提出了器件效率限制因素背后的物理机制.洞悉物理机制可为今后优化设计高性能的器件提供准则.因此及时总结硅异质结太阳电池的物理机制和优化设计非常必要.本文主要讨论了晶硅表面钝化、发射极掺杂层和透明导电层之间的功函数失配以及由此形成的肖特基势垒;讨论了屏蔽由功函数失配引起的能带弯曲所需的特征长度,即屏蔽长度;介绍了硅异质结太阳电池优化设计的数值模拟和实践;总结了硅异质结太阳电池的研究现状和发展前景.