Halogen Bond Catalyzed Bromocarbocyclization

A halogen bond catalyzed bromo‐carbocyclization of N‐cinnamyl sulfonamides and O‐cinnamyl phenyl ethers has been developed. N‐methyl 4‐iodopyridinium triflate is used as the halogen‐bonding organocatalyst and the reaction is highly chemoselective. This report represents the first proof‐of‐concept for halogen‐bonding organocatalyst‐promoted electrophilic halogenation. Mechanistic study suggests the autocatalytic nature of this reaction.     

Influence of Solvent and Bridge Structure in Alkylthio‐Substituted Triphenylamine Dyes on the Photovoltaic Properties of Dye‐Sensitized Solar Cells

Three new triphenylamine dyes that contain alkylthio‐substituted thiophenes with a low bandgap as a π‐conjugated bridge unit were designed and synthesized for organic dye‐sensitized solar cells (DSSCs). The effects of the structural differences in terms of the position, number, and shape of the alkylthio substituents in the thiophene bridge on the photophysical properties of the dye and the photovoltaic performance of the DSSC were investigated. The introduction of an alkylthio substituent at the 3‐position of thiophene led to a decrease in the degree of redshift and the value of the molar extinction coefficient of the charge‐transfer band, and the substituent with a bridged structure led to a larger redshift than that of the open‐chain structure. The introduction of bulky and hydrophobic side chains decreased the short‐circuit photocurrent (J_sc), which was caused by the reduced amount of dye adsorbed on TiO₂. This resulted in a decrease in the overall conversion efficiency (η), even though it could improve the open‐circuit voltage (V_oc) due to the retardation of charge recombination. Furthermore, the change in solvents for TiO₂ sensitization had a critical effect on the performance of the resulting DSSCs due to the different amounts of dye adsorbed. Based on the optimized dye bath and molecular structure, the ethylene dithio‐substituted dye ( ATT3 ) showed a prominent solar‐to‐electricity conversion efficiency of 5.20 %.     

Vertically constrained CO2 retrievals from TCCON measurements

Partial column-averaged carbon dioxide (CO₂) mixing ratio in three tropospheric layers has been retrieved from Total Carbon Column Observing Network (TCCON) spectra in the 1.6 μm CO₂ absorption band. Information analysis suggests that a measurement with ～60 absorption lines provides three or more pieces of independent information, depending on the signal-to-noise ratio and solar zenith angle. This has been confirmed by retrievals based on synthetic data. Realistic retrievals for both total and partial column-averaged CO₂ over Park Falls, Wisconsin on July 12, 15, and August 14, 2004, agree with aircraft measurements. Furthermore, the retrieved total column averages are always underestimated by less than 1%. The results above provide a basis for CO₂ profile retrievals using ground-based observations in the near-infrared region.     

基于高斯光束特性的Mie散射大气激光雷达回波近场信号校正研究

介绍一种基于高斯光束传输特性对Mie散射激光雷达回波信号校正的新方法.首先根据发射激光束的高斯光束特性，对大气激光雷达回波信号作高斯修正，然后在大气近似均匀假定下，对近场区经高斯修正的回波信号距离校正函数进行二次曲线拟合，实现对交叠面积影响的修正，实际计算表明，用此方法对Mie散射激光雷达回波近场信号进行处理，可获得与实际更为接近的反演结果. 关键词： 大气激光雷达 高斯光束 回波近场信号修正 大气消光系数     

太阳光谱方法测量成都地区大气二氧化氮浓度

文章报道的是用太阳光谱方法测量成都地区NO2浓度的实验研究,使用CCD光学多道分析器采集成都市区和西岭雪山的太阳光谱,以大气上界太阳光谱为参考,对五个分立光谱段以最小二乘法进行数据拟合,应用差分吸收原理解谱,获得了成都市区和西岭雪山NO2浓度.成都市区NO2浓度(垂直柱体密度)在3.1×1016至5.8×1016(molecule·cm-2)之间,西岭雪山的NO2浓度在0.7×1016至1.0×1016(mole-cule·cm-2)之间.随大气温度的上升,NO2浓度有上升趋势.     

Collapse of magnetized hypermassive neutron stars in general relativity

Hypermassive neutron stars (HMNSs)--equilibrium configurations supported against collapse by rapid differential rotation--are possible transient remnants of binary neutron-star mergers. Using newly developed codes for magnetohydrodynamic simulations in dynamical spacetimes, we are able to track the evolution of a magnetized HMNS in full general relativity for the first time. We find that secular angular momentum transport due to magnetic braking and the magnetorotational instability results in the collapse of an HMNS to a rotating black hole, accompanied by a gravitational wave burst. The nascent black hole is surrounded by a hot, massive torus undergoing quasistationary accretion and a collimated magnetic field. This scenario suggests that HMNS collapse is a possible candidate for the central engine of short gamma-ray bursts.     

Structure and thermophysical properties of single-wall Si nanotubes

In this work, molecular dynamics (MD) simulation based on the environment-dependent interatomic potential is carried out to explore the structure, atomic energy distribution, and thermophysical properties of single-wall Si nanotubes (SWSNTs). The unique structure of SWSNTs leads to a wider range energy distribution than crystal Si (c-Si), and results in a bond order in the range of 4.8–5. The thermal conductivity of SWSNTs is much smaller than that of bulk Si, and shows significantly slower change with their characteristic size than that of Si films. Out of the three types of SWSNTs studied in this work, pentagonal SWSNTs have the highest thermal conductivity while hexagonal SWSNTs have the lowest one. The specific heat of SWSNTs is a little larger than that of bulk c-Si. Pentagonal and hexagonal SWSNTs have close specific heats, which are a little larger than that of rectangular SWSNTs.     

利用激光雷达测量都市上空气溶胶的浓度分布

测量都市上空气溶胶浓度分布的最方便方法是水平米散射激光雷达。因激光雷达是主动遥感监测系统,其测量距离可达到几公里,而且具有高时空分辨率的特点。同时,其设计也可以达到激光安全标准。本研究所用的激光雷达系统是安装在海拔118米高的山上。在观测时可以测量稠密市区上空的气溶胶分布与及监察从发电厂排放出的微粒。本文介绍这激光雷达系统的设计及激光雷达反演的方法。会对激光雷达量度的消光系数与大气监测的可悬浮粒子浓度之间的相关性进行考证。