An atomic force microscope study of vanadium-benzene sandwich clusters soft-landed on self-assembled monolayers

Multiple-decker vanadium-benzene sandwich clusters V_n(benzene)_n+1 produced by a laser-vaporization synthesis method were soft-landed onto self-assembled monolayers of alkanethiol (C₁₈H-SAM) and fluorinated alkanethiol (C₁₀F-SAM) at 200 K. Noncontact atomic force microscopy has been used to examine the resulting adsorption states of the clusters landed on the SAMs at room temperature. For each SAM substrate, the aggregates of the deposited clusters were observed at the vacancy islands and near the steps of the SAM surface. The result indicates that, at room temperature, the clusters landed on the SAM substrate thermally diffuse on the surface to form columnar-shape islands around the defect sites of the SAM surface.     

Structure-based discovery of glycolipids for CD1d-mediated NKT cell activation: tuning the adjuvant versus immunosuppression activity

Introduction of an aromatic group into the fatty acyl chain of alpha-GalCer modulates the activity and selectivity of IFN-gamma/IL-4 secretion through CD1d-mediated activation of NKT cells. Compound 14-16 are more potent than alpha-Galcer and biased for IFN-gamma than for IL-4. These new glycolipids may find use as adjuvants or as antimetastatic agents.     

Quantum sieving effect of modified activated carbon fibers on H2 and D2 adsorption at 20 K

Quantum sieving of activated carbon fibers (ACFs) and their fluorides was observed for H(2) and D(2) adsorption at 20 K. Fluorination reduced the slit-shaped pore width of ACFs by 0.2 nm. The activated carbon fibers can act as highly efficient quantum sieves for H(2) and D(2), because the effective size of an H(2) molecule is larger than that of a D(2) molecule due to the uncertainty principle and the molecular size difference between H(2) and D(2) is significant in the micropore space. The D(2)/H(2) selectivity of ACFs evaluated by ideal adsorption solution theory was larger than that of the fluorinated ACFs.     

Arrangement of K Clusters in the K-Doped Zeolite K-LTA

Abstract

K clusters incorporated into zeolite K-LTA causes ferromagnetism below 8 K. Distribution of K⁺ ions in its α-cages was studied by X-ray powder diffraction. On the basis of space group F23, electron-density distribution was determined by Rietveld analysis followed by iteration of analysis by a maximum-entropy method and whole-pattern fitting. K⁺ ions were located in α-cages in such a way that K clusters between adjacent α-cages are not equivalent to each other, which will lead to the ferromagnetism with antiferromagnetic components.     

Synthesis and crystal structure of a layered silicate HUS-1 with a halved sodalite-cage topology

A new layered silicate, HUS-1, was synthesized by hydrothermal synthesis using decomposed FAU- and *BEA-type zeolites as nanosized silica parts. Structural analyses by X-ray powder diffractometry and solid-state magic-angle-spinning (MAS) NMR spectroscopy revealed that HUS-1 has a layered structure containing a silicate layer per unit cell along a stacking direction. Its framework topology is similar to that of SOD-type zeolites and consists of a halved sodalite cage, which includes four- and six-membered Si rings. Structure refinement by the Rietveld method showed that tetramethylammonium (TMA) ions used as a structure-directing agent (SDA) were incorporated into the interlayer. The four methyl groups of the TMA molecule were located orderly in a hemispherical cage in the silicate layer, which suggests restraint of molecular motion. The interlayer distance is estimated at about 0.15 nm, which is unusually short in comparison with that in other layered silicates (e.g., β-HLS or RUB-15) with similar framework topologies. The presence of hydrogen bonding between adjacent terminal O atoms was clearly revealed by the (1)H MAS NMR spectroscopy and by electron-density distribution obtained by the maximum entropy method.     

Hybridization-sensitive fluorescence control in the near-infrared wavelength range

A series of near-infrared fluorescent probes were designed based on the concept of emission control caused by interdye excitonic interaction. The fluorescent probes showed very weak emission in the unhybridized state, whereas they emitted near-infrared fluorescence after hybridization with the complementary nucleic acid. The hybridization-dependent switching of fluorescence emission made it possible to monitor mRNA in human cells in the range of near-infrared wavelengths.     

SYNTHESIS AND REACTIONS OF HALO DERIVATIVES OF 4-ISOPROPYL-2H-1,4-THIAZIN-3-ONE

Abstract

Reaction of 4-isopropyl-2H-1,4-thiazin-3-one 1 (R [dbnd] i-Pr) with N-chloro- and N-bromosuccinimide occurred exclusively at the 6-position to give 6-chloro and 6-bromo derivatives of 1 (R [dbnd] i-Pr), respectively, in high yield, in sharp contrast to the 2-aroyloxylation by benzoyl peroxide or m-chloroperbenzoic acid reported earlier.² Reaction of 1 (R [dbnd] i-Pr) with methanesulfonyl chloride in the presence of aluminum chloride afforded an addition compound, 4-isopropyl-5,6-dichloro-1,4-tetrahydrothiazin-3-one. The 2-chloro derivative 6 of 1 (R [dbnd] i-Pr) was successfully prepared by hydrolysis of the 2-m-chloroben-zoyloxy derivative of 1 (R [dbnd] i-Pr) followed by treatment with thionyl chloride. Derivative 6 reacted readily under mild conditions with water, alcohols, thiols, ammonia and amines to give various 2-substituted compounds of 1 (R [dbnd] i-Pr). With phenol as a nucleophile, 1 (R [dbnd] i-Pr) reacted exclusively at the para position. Reaction at carbon atoms also occurred with N,N-dimethylaniline and 2,6-xylidine.     

SYNTHESES AND SOME PROPERTIES OF SULFOXIDES,SULFILIMINES, AMINOSULFONIUM SALTS AND SULFOXIMINES CONTAINING PYRIDINE NUCLEI

Abstract

Several 2-pyridyl sulfides (1) (e.g., methyl (1a), ethyl (1b), isopropyl (1c), benzyl (1d), 1-phenylethyl (1e), l-menthyl (If) 2-pyridyl sulfides; and bis(2-pyridylthio)methane (1g), and methyl 2-(N-oxy-pyridyl) sulfide (1h) were prepared by the usual method. Sulfoxides (2) were prepared by oxidation of the corresponding sulfides with m-chloroperbenzoic acid in good yields. A few sulfoxides were found to work as phase-transfer catalysts for some typical nucleophilic reactions in nonpolar solvents such as benzene, and in two-phase systems such as benzene-water. S-2-Pyridyl-N-(p-toluenesulfonyl) sulfilimines (3) were prepared upon treatment of sulfides with Chloramine-T. Hydrolysis of N-(p-toluenesulfonyl)-2-pyridyl-o-tolylsulfilimine (3i) with conc. sulfuric acid gave the corresponding free sulfilimine in a moderate yield. S-2-Pyridyl sulfoximines (4) were not obtained by the general method from the sulfoxides and hydrazoic acid. Alkyl-2-pyridyl sulfoximines, however, were obtained by oxidation of the free sulfilimines derived from the corresponding aminosulfonium salts (5) prepared by reaction of the sulfides with mesitylene-sulfonylhydroxylamine (MSH). These free sulfilimines and sulfoximines thus prepared were found to give adducts with a few copper salts.     

基于BICC算法的PIV技术

对基于ＢＩＣＣ（ＢｉｎａｒｙＩｍａｇｅＣｒｏｓｓ－Ｃｏｒｒｅｌａｔｉｏｎ）算法的ＰＩＶ（ＰａｒｔｉｃｌｅＩｍａｇｅＶｅｌｏｃｉｍｅｔｒｙ）技术的原理进行了较详细的介绍．以封闭的正方形容器内的旋转流场为例，用计算机模拟检验了ＢＩＣＣ算法的可靠性，最后利用ＰＩＶ技术对阀腔内真实流场进行了测量．结果表明，ＢＩＣＣ算法能有效地进行图像粒子的识别，利用该算法可以得到精确的ＰＩＶ测量结果．