Gaseous Formaldehyde Degrading by Methylobacterium sp. XJLW

Applied Biochemistry and Biotechnology - Formaldehyde is harmful to human beings. It is widely used in chemical industry, medicine, and agriculture and is frequently discharged into the sewage....     

溴鎓离子的结构解析

溴鎓离子是烯烃与溴加成历程中的环状中间体,详细解析其结构对理解不同烯烃与溴的加成历程以及判断加成产物都大有裨益。目前,国内外的教材还没有关于溴鎓离子结构的详细介绍,本文将对溴鎓离子三元环中各原子的杂化方式和电荷分布及后续的亲核取代历程等方面进行分析,以期为有机化学教材提供适当的补充。     

液晶人工神经元阵列的研制

研制了一种液晶灵巧像素光学神经元阵列器件，它利用光电混合集成技术，以非晶硅作光敏材料，以液晶实现光调制，通过特殊设计的器件结构，能实现对两束光的相减和非线性取阈等人工神经元功能。该器件具有８×８个神经元，以全并行方式工作     

一种用于多目标旋转不变分类识别的神经网络模型及算法

提出了一种适于光学实现的神经网络模型和算法，通过对３种飞行器平面内旋转投影较的识别，证明了该方法具有对多目标转动不变的模式识别能力。     

Al6FeYb合金中十次准晶相关晶体相的高压形成

 对掺稀土钇的铝铁合金（Al₆FeYb）进行了静高压（4.8 GPa）熔态（1 400 ℃）淬火（冷却速率100 ℃/s）研究。使用透射电镜对样品中形成的微结构进行了观察。首次在该系统中发现了一个十次准晶相关晶体相。实验分析表明，该相为底心正交晶体相，电镜测得的晶胞参数为a＝0.716 nm，c＝2.195 nm。用已有的理论对该相的结构形成进行了讨论。     

Sampling of states for estimating the folding funnel entropy and energy landscape of a model alpha-helical hairpin peptide

Protein folding times are many orders of magnitude shorter than would occur if the peptide chain randomly sampled possible configurations, which implies that protein folding is a directed process. The detailed shape of protein's energy landscape determines the rate and reliability of folding to the native state, but the large number of structural degrees of freedom generates an energy landscape that is hard to visualize because of its high dimensionality. A commonly used picture is that of an energy funnel leading from high energy random coil state down to the low energy native state. As lattice computer models of protein dynamics become more realistic, the number of possible configurations becomes too large to count directly. Statistical mechanic and thermodynamic approaches allow us to count states in an approximate manner to quantify the entropy and energy of the energy landscape within a folding funnel for an alpha-helical protein. We also discuss the problems that arise in attempting to count the huge number of individual states of the random coil at the top of the funnel.     

高岭土负载SO2-4/ZrO2-TiO2催化剂的制备及其在缩酮合成中的应用

以经H2SO4处理焙烧的高岭土为载体,制备了以其负载的SO4(2-)/ZrO2-TiO2固体酸催化剂.用FT-IR、XRD和NH3-TPD等测试技术表征了催化剂的微观结构及酸强度,考察了对环己酮乙二醇缩酮反应的催化活性及稳定性.结果表明,酸化处理使高岭土表面酸量增加,但酸强度变化不大,而其负载SO4(2-)/ZrO2-TiO2后,经500℃焙烧3 h其酸量及酸强度显著升高.环己酮用量为0.2 mol、乙二醇0.24 mol、催化剂1.2 g、带水剂环己烷15 mL,回流反应70 min后,缩酮收率可达96.8%,催化剂重复使用5次收率保持在90%以上.     

Theoretical studies of ground and excited states in a series of Zn(II) complexes,derived from thiourea and thiosemicarbazide

Theoretical studies for a series of mono- and binuclear zinc (II) complexes Zn(CH₃COO)₂(H₂L)₂ [H₂L = N-2-propenyl-N ^′-2-pyridinylthiourea] (A), Zn₂(CH₃COO)₂(H₃L-a)₂ [H₃L-a = 2-[(2-hydroxy phenyl)methylene]hydrazine-N-phenylcarbothioamide] (B), and Zn(H₃L-b)₂ [H₃L-b = 2-[(2-hydroxy phenyl)methylene]hydrazine-N-(2-propenyl)carbothioamide] (C) have been performed on their structures and excited-state absorption spectra. The singlet ground-state geometries are fully optimised at three DFT levels, i.e., B3LYP, B3PW91, and M06. Different geometries, i.e., strongly distorted tetrahedral coordination environment in complex A, distorted square-pyramidal environment in complex B, and irregular octahedral mode in complex C are identified. Consequently, the spectroscopic properties are calculated by means of time-dependent density functional theory (TDDFT) with the Polarisable Continuum Model (PCM) based on the optimised gas-phase geometries. Three absorption peaks are identified for every complex, which are in good agreement with the experimental ones. For complex A, all three absorption peaks centered at 280.33 nm, 268.09 nm, and 250.87 nm, respectively, are ascribed to the (p,π) → π* transition with a mixed intraligand charge-transfer (ILCT)/ligand-ligand charge-transfer (LLCT) character. The composition of frontier orbitals involved in major absorption bands for the three complexes shows similarities, which results in the almost homologous transition attributions and characteristics. A remarkable bathochromic shift in the lowest-lying absorption band is observed for complexes B and C as compared with complex A, which is attributed to the decreased H (HOMO)-L (LUMO) energy gap (ΔE |HOMO-LUMO|) by the formation of conjugate metallocycles in complexes B and C.     

Electrical property of nanocrystalline γ-Fe2O3 under high pressure

Using a microcircuit fabricated on a diamond anvil cell, in situ conductivity measurements on nanophase (NP) γ-Fe₂O₃ are obtained under high pressure. For NP γ-Fe₂O₃, the abrupt increase in electrical conductivity occurs at a pressure of 21.3 GPa, corresponding to a transition from maghemite to hematite. Above 26.4 GPa, conductivity increases smoothly with increasing pressure. No distinct abnormal change is observed during decompression, indicating that transformation is irreversible. The temperature-dependence of the conductivity of NP γ-Fe₂O₃ was investigated at several pressures, indicating the electrical conductivity of the sample increases with increasing pressure and temperature, and that a remarkable phenomenon of discontinuity occurs at 400 K. The abnormal change is attributed to the electronic phase transitions of NP γ-Fe₂O₃ due to the variation of inherent cation vacancies. Besides, the temperature-dependence of the electrical conductivity displays semiconductor-like behavior before 33.0 GPa.     

免光学间隔层的高效聚合物太阳能电池

使用相对聚(3乙基噻吩)(P3HT)具有更低能带结构的聚{[9-(1辛基壬基)-9H-咔唑-2,7-2基]-2,5-噻吩二基-2,1,3-苯并噻二唑-4,7-二基-2,5噻吩二基}(PCDTBT)作为电子给体材料和较C60衍生物(PC60BM)具有更广光谱吸收能力的C70衍生物(PC70BM)作为电子受体材料构建共混体系活性层,制备有机聚合物太阳能电池。通过控制活性层薄膜生长速度、环境得出在N2环境中静置10min时聚合物电池达到了5.65%的高光电转换效率(PCE)。然后,通过进一步优化活性层薄膜厚度短路电流密度大幅提升至14.2mA/cm2,PCE达到5.84%。结果表明,在不使用TiOx等光学间隔层的情况下,通过控制活性层薄膜生长过程和优化活性层薄膜厚度也可以大幅增加短路电流密度,获得高的PCE。