Total synthesis,stereochemical assignment,and biological evaluation of L-755,807

The relative and absolute configurations of L-755,807 were established through total synthesis. All four possible stereoisomers were prepared via a convergent synthetic strategy, including a novel diastereoselective Darzens reaction of an α-alkoxy aldehyde with di-tert-butyl bromomalonate, an E-selective Horner–Wadsworth–Emmons reaction, and late-stage coupling of the ring and side-chain segments. Additionally, biological evaluation of the synthesized compounds revealed their potent inhibitory activities (IC₅₀?=?5–21?μM) against amyloid-β aggregation for the treatment of Alzheimer's disease.     

Pulse shape and molecular orientation determine the attosecond charge migration in Caffeine

The recent reduction of laser pulse duration down to the attosecond regime offers unprecedented opportunities to investigate ultrafast changes in the electron density before nuclear motion sets in. Here, we investigate the hole dynamics in the Caffeine molecule that is induced by an ionizing XUV pulse of 6 fs duration using the approximate time-dependent density functional theory method TD-DFTB. In order to account for ionization in a localized atomic orbital basis we apply a complex absorbing potential to model the continuum. Propagation of the time-dependent Kohn–Sham equations allows us to extract the time-dependent hole density taking the pulse shape explicitly into account. Results show that the sudden ionization picture, which is often used to motivate an uncorrelated initial state, fails for realistic pulses. We further find a strong dependence of the hole dynamics on the polarization of the laser field. Notwithstanding, we observe fs charge migration between two distant functional groups in Caffeine even after averaging over the molecular orientation.     

Raman study on electrochemical lithium insertion into multiwalled carbon nanotubes

We have carried out in situ Raman studies during the electrochemical insertion of lithium ions (Li⁺) into pristine and thermally treated multiwalled carbon nanotubes (MWNTs). We found an improved structural integrity as well as the removal of defects in the thermally treated tubes. The different Li⁺ insertion behaviors above 0.5 V in as‐grown and thermally treated tubes could be explained by the presence of defects on the outer surface of the tubes. No change of Raman spectra from 2.8 to 0.8 V is characterized by the coverage of Li⁺ on the outer surface of tubes, whereas the upshift of G band and the absence of a separated G band below 0.75 V indicate the formation of diluted graphite intercalation below the stage‐2 phase (LiC₁₂). Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis of non-stoichiometric (LaO)CuS thin films by pulse laser deposition

We have attempted to control the photoluminescence spectrum of transparent p-type semiconductor (LaO)CuS to check possibilities of phosphor application using non-stoichiometric thin films prepared by pulse laser deposition method. Two kinds of samples are examined, one is the samples that contain the excess S and the other is the excess Cu. All samples are a single phase without impurities, regardless of heavily doping. Lattice constants for all samples don’t depend on the concentration of excess atoms. Perhaps, this is due to the nature of the layered materials. Introduction of excess atoms leads to change the photoluminescence spectra. The excess S and Cu have much effect on the red and the blue luminescence bands, respectively. We have succeeded in the tuning luminescence band of photoluminescence spectra.     

调制n型掺杂ZnSe/BeTe Ⅱ型量子阱结构的发光特性

报道了调制n型掺杂ZnSe/BeTe/ZnSe Ⅱ型量子阱(type-II QW)在极低温至室温(14—296K)条件下的各种光学性质. 反射光谱显示了对于非掺杂样品,激子(X)的跃迁起着支配作用,而只有在掺杂样品的光谱里展示了一个典型的负的带电激子(X^-)的跃迁特征. PL光谱及其直线偏振度P_l都显著地依赖于n型掺杂量和平行于QW生长方向的外加电场. 这个特征被认为是由n型掺杂导致了内秉电场(built 关键词： 光致发光 二维电子气 带电激子 Ⅱ型量子阱     

The Integrals of Motion for the Deformed W-Algebra $${W_{q,t}(\widehat{gl_N})}$$. II. Proof of the Commutation Relations

We explicitly construct two classes of infinitely many commutative operators in terms of the deformed W-algebra , and give proofs of the commutation relations of these operators. We call one of them local integrals of motion and the other nonlocal, since they can be regarded as elliptic deformations of local and nonlocal integrals of motion for the Virasoro algebra and the W ₃ algebra [1,2]. Dedicated to Professor Tetsuji Miwa on the occasion of the 60th birthday     

Structure and depletion at fluorocarbon and hydrocarbon/water liquid/liquid interfaces

The results of x-ray reflectivity studies of two oil/water (liquid/liquid) interfaces are inconsistent with recent predictions of the presence of a vaporlike depletion region at hydrophobic/aqueous interfaces. One of the oils, perfluorohexane, is a fluorocarbon whose superhydrophobic interface with water provides a stringent test for the presence of a depletion layer. The other oil, heptane, is a hydrocarbon and, therefore, is more relevant to the study of biomolecular hydrophobicity. These results are consistent with the subangstrom proximity of water to soft hydrophobic materials.