Titanocen-cyandithioformiat-Komplexe

The reaction of titanocene dichloride,Cp ₂TiCl₂ (Cp=723l3lgjn7307/xxlarge951.gif" alt="eegr" align="MIDDLE" BORDER="0">⁵-C₅H₅), with one or two equivalents of sodium cyanodithioformate affords the new mono- or bis(dithiocarboxylato) derivativesCp ₂TiCl(S₂CCN) (1) andCp ₂Ti(S₂CCN)₂ (2). Elimination of sulfur converts2 into the metallacyclicCp ₂TiS₂C₂(CN)₂ (3), which does not react with the diene isoprene, but can be reconverted into the appropriate titanocene dihalides by chlorine or bromine.

     

G.723.1双速率语音编解码算法在TMS320VC5402上的实现

本文先简单介绍了G.723.1双速率编解码算法标准，然后根据TI公司的DSP芯片TMS320VC5402的性能特征，在深入分析G.723.1标准的C源代码后，对算法进行了一系列优化。文中详述了这些优化方法。最后介绍了一个实际的硬件实现。     

On the packing chromatic number of some lattices

For a positive integer k, a k-packing in a graph G is a subset A of vertices such that the distance between any two distinct vertices from A is more than k. The packing chromatic number of G is the smallest integer m such that the vertex set of G can be partitioned as V₁,V₂,…,V_m where V_i is an i-packing for each i. It is proved that the planar triangular lattice T and the three-dimensional integer lattice Z³ do not have finite packing chromatic numbers.     

Action des hydrazines fluoroalkylées sur les phosphoallènes: synthèse d’hydrazones N-fluoroalkylées β-phosphonatées

Ten phosphorylated β-hydrazones of structure R₂P(O)C(NNHR_F)CHR₂′ were prepared in 54-91% yield by heating the allenes R₂P(O)CHCCR₂′ with fluorinated hydrazines H₂NNHR_F in chloroform or methanol [R=Ph, OCH₂C(Me)₂CH₂O or OCH₂C(Me)(Pr)CH₂O, R′=H or Me and R_F=CH₂CF₃ or C₆F₅]. Two cyclohexyl derivatives were prepared similarly from R₂P(O)CHCCy. The triphenyl derivatives Ph₂P(O)CH₂C(NNHCH₂CF₃)Ph and Ph₂P(O)CH₂C(NNHC₆F₅)Ph were made in 91 and 68% yield by heating the ketones Ph₂P(O)CH₂C(O)Ph with an ethanol solution of the corresponding hydrazines. The stereochemistry of the hydrazones was determined by multinuclear NMR experiments. Compounds with C(NNHR_F)Me groups exist as a mixture of Z and E isomers, with the Z form predominating (fluorinated group syn to phosphorus). Those with C(NNHR_F)CHMe₂, C(NNHR_F)Cy or C(NNHR_F)Ph groups were formed selectively, the Z isomers being the only products. The results are explained by steric hindrance, the bulkier isopropyl, cyclohexyl or phenyl group disfavouring the E configuration. , , , NMR data, coupling constants and IR data are reported.     

新型语音压缩芯片CT8022

介绍了DSPG公司生产的语音压缩专用芯片CT8022的引脚功能和主机与存储器的接口，给出了CT8022的工作原理，工作模式，工作流程和使用方法，最后给出了CT8022与主机组成的语音压缩应用电路的连接方法。     

Diastereoselectivity in theLewis acid mediated aldol reaction of chiral α, β-epoxyaldehydes with a ketene silyl acetal

Summary The Lewis acid mediated aldol reaction of chiral 723/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">, 723/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-cis andtrans epoxyaldehydes1 and2 withtert-butyl ketene silyl acetal proceeds mainly withanti diastereofacial preference. The best results were obtained forcis epoxyaldehyde1 in the presence of catalytic amounts of BiCl₃·1.5 eq. ZnI₂ (anti:syn 723/xxlarge8764.gif" alt="sim" align="MIDDLE" BORDER="0"> 13:1), whereas the poorest stereoselectivity was observed when an excess of LiClO₄ was used (anti:syn 723/xxlarge8764.gif" alt="sim" align="MIDDLE" BORDER="0"> 1:1). The more stable epoxyaldehyde conformers were determined and the diastereofacial preference was found to be in agreement with a nucleophilic attack on the energetically more favoured conformers.

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Diastereoselektivität derLewis-Säure-katalysierten Aldolreaction zwischen chiralen 723/xhuge945.gif" alt="agr" align="BASELINE" BORDER="0">, 723/xhuge946.gif" alt="beta" align="MIDDLE" BORDER="0">-Epoxyaldehyden und einem Ketensilylacetal

Zusammenfassung DieLewis-Säure-katalysierte Aldolreaktion der chiralen 723/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">, 723/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-cis- und -trans-Epoxyaldehyde1 und2 mittert-Butylketensilylacetal verläuft stereoselektivanti. Die besten Ergebnisse wurden für dencis-Epoxyaldehyd1 in Gegenwart katalytischer Mengen BiCl3·1.5 eq. Znl₂ erhalten (anti:syn 723/xxlarge8764.gif" alt="sim" align="MIDDLE" BORDER="0"> 13:1). Die geringste Stereoselektivität trat auf, wenn LiClO₄ im Überschuß eingesetzt wurde (anti:syn 723/xxlarge8764.gif" alt="sim" align="MIDDLE" BORDER="0"> 1:1). Das beobachtete Verhalten steht mit einem nucleophilen Angriff am energetisch günstigeren Konformeren im Einklang.

     

minimum dominating set of queens: A trivial programming exercise?

minimum dominating set of queens is one of the typical programming exercises of a first year’s computer science course. However, little work has been published on the complexity of this problem. We analyse here several algorithms and show that advanced algorithmic techniques may dramatically speed up solving this problem.     

Internal correction of hafnium oxide spectral interferences and mass bias in the determination of platinum in environmental samples using isotope dilution analysis

A method has been developed for the accurate determination of platinum by isotope dilution analysis, using enriched ¹⁹⁴Pt, in environmental samples containing comparatively high levels of hafnium without any chemical separation. The method is based on the computation of the contribution of hafnium oxide as an independent factor in the observed isotope pattern of platinum in the spiked sample. Under these conditions, the ratio of molar fractions between natural abundance and isotopically enriched platinum was independent of the amount of hafnium present in the sample. Additionally, mass bias was corrected by an internal procedure in which the regression variance was minimised. This was possible as the mass bias factor for hafnium oxide was very close to that of platinum. The final procedure required the measurement of three platinum isotope ratios (192/194, 195/194 and 196/194) to calculate the concentration of platinum in the sample. The methodology has been validated using the reference material “BCR-723 road dust” and has been applied to different environmental matrices (road dust, air particles, bulk wet deposition and epiphytic lichens) collected in the Aspe Valley (Pyrenees Mountains). A full uncertainty budget, using Kragten’s spreadsheet method, showed that the total uncertainty was limited only by the uncertainty in the measured isotope ratios and not by the uncertainties of the isotopic composition of platinum and hafnium. Figure Simultaneous correction of hafnium oxide spectral interferences and mass bias in the determination of platinum in environmental samples using isotope dilution analysis Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

Counting BPS operators in SYM

The free field partition function for a generic U(N) gauge theory, where the fundamental fields transform in the adjoint representation, is analysed in terms of symmetric polynomial techniques. It is shown by these means how this is related to the cycle polynomial for the symmetric group and how the large N result may be easily recovered. Higher order corrections for finite N are also discussed in terms of symmetric group characters. For finite N, the partition function involving a single bosonic fundamental field is recovered and explicit counting of multi-trace quarter BPS operators in free super-Yang–Mills discussed, including a general result for large N. The partition function for quarter BPS operators in the chiral ring of super-Yang–Mills is analysed in terms of plane partitions. Asymptotic counting of BPS primary operators with differing R-symmetry charges is discussed in both free super-Yang–Mills and in the chiral ring. Also, general and explicit expressions are derived for SU(2) gauge theory partition functions, when the fundamental fields transform in the adjoint, for free field theory.     

G.723.1语音编码器算法的聚类优化策略及其应用

在实现G.723.1编码器算法的基础上,提出了一种针对码本搜索的聚类优化策略,利用聚类分析的结果,对原始码本进行了分组及重构等处理,从而实现了快速搜索。测试及系统的实际运行情况表明,在使算法复杂度下降约1.46MIPS的条件下,优化结果仍能保证解码端的音质无明显下降。