Measurement of prompt charm meson production cross sections in pp collisions at square root s = 1.96 TeV

We report on measurements of differential cross sections dsigma/dp(T) for prompt charm meson production in ppmacr; collisions at sqrt[s]=1.96 TeV using 5.8+/-0.3 pb(-1) of data from the CDF II detector at the Fermilab Tevatron. The data are collected with a new trigger that is sensitive to the long lifetime of hadrons containing heavy flavor. The charm meson cross sections are measured in the central rapidity region |y|K-pi(+), D(*+)-->D0pi(+), D+-->K-pi(+)pi(+), D(+)(s)-->phipi(+), and their charge conjugates. The measured cross sections are compared to theoretical calculations.     

Experimental characterization of transition to chaos in the presence of noise

Transition to chaos in the presence of noise is an important problem in nonlinear and statistical physics. Recently, a scaling law has been theoretically predicted which relates the Lyapunov exponent to the noise variation near the transition. Here we present experimental observation of noise-induced chaos in an electronic circuit and obtain the fundamental scaling law characterizing the transition. The experimentally obtained scaling exponent agrees very well with that predicted by theory.     

激光导致的透明固体损伤模型

详细分析了描述激光导致损伤的"移动的损伤"模型,发现该模型不适用于常见的飞秒激光对绝缘性透明固体材料处理的情况(如:800nm的100fs激光脉冲,0.65NA紧聚焦系统),此时脉冲与物质间相互作用区域和聚焦系统的瑞利长度可以比拟.对模型做了改进,改进后的模型可以很好地预期飞秒激光脉冲在固体中产生损伤的时间和空间形态.     

Numerical and experimental investigation of the effect of filtering on chaotic symbolic dynamics

Motivated by the practical consideration of the measurement of chaotic signals in experiments or the transmission of these signals through a physical medium, we investigate the effect of filtering on chaotic symbolic dynamics. We focus on the linear, time-invariant filters that are used frequently in many applications, and on the two quantities characterizing chaotic symbolic dynamics: topological entropy and bit-error rate. Theoretical consideration suggests that the topological entropy is invariant under filtering. Since computation of this entropy requires that the generating partition for defining the symbolic dynamics be known, in practical situations the computed entropy may change as a filtering parameter is changed. We find, through numerical computations and experiments with a chaotic electronic circuit, that with reasonable care the computed or measured entropy values can be preserved for a wide range of the filtering parameter.     

A novel synthesis of 5-functionalized oxazolidin-2-ones from enantiomerically pure 2-substituted N-[(R)-(+)-alpha-methylbenzyl]aziridines

5-Funtionalized enantiomerically pure oxazolidin-2-ones were prepared in one pot from commercially available chiral aziridines bearing an electron-withdrawing group at C-2 with retention of the configuration in high yields by regioselective aziridine ring-opening followed by intramolecular cyclization.     

Enantiospecific synthesis of carbapentostatins

In this paper we describe enantioselective syntheses of (+)-carbapentostatin (8) and its cyclopentyl analogue 12b. A new and efficient one-pot, two-step preparation of aldehyde 15 has been developed, based on the borane reduction of N-Pf-protected L-aspartic acid gamma-methyl ester (13) and Swern oxidation of the resulting alcohol. Homologation to diester 18 and ring formation by Dieckman cyclization, followed by reduction and dehydration steps, afford the 4-amino-1-cyclopentenemethanol derivative 22. Hydroboration and oxidation transform this compound stereospecifically into aminocyclopentanol 26, the key aminocyclitol component for an asymmetric synthesis of (+)-carbapentostatin.     

Rapid and high-capacity immobilization of enzymes based on mesoporous silicas with controlled morphologies

Very rapid (< 10 min to reach equilibrium) and high-capacity (up to 533 mg g(-1)) immobilization of enzymes within mesoporous silica has been achieved by finely tuning their morphologies.     

Synthesis, cyclic voltammetric studies, and electrogenerated chemiluminescence of a new phenylquinoline-biphenothiazine donor-acceptor molecule

We report the synthesis, electrochemistry, and luminescence of a novel ECL emitting compound containing two electron-accepting hexyl-phenylquinoline groups covalently attached to the 3,3'-positions of the electron-donating 10,10'-dimethylbiphenothiazine group. The optimized geometry as determined from semiempirical MNDO calculations shows that the two quinoline groups are twisted 82.5 degrees from the two phenothiazine rings, indicating a lack of electron delocalization among these groups. This unique geometry allows generation of localized radical cations and radical anions capable of generating ECL upon annihilation. However, the phenothiazine rings are twisted 46.5 degrees relative to each other, suggesting possible interactions between the two moieties. This is evident in the electrochemical behavior in which two closely spaced one-electron oxidations, rather than a single two-electron oxidation wave, were observed. The photophysical properties of BHQ-BPZ show strong resemblances to the parent compound, BPQ-PTZ, which contains a single phenothiazine moiety. In addition, the ECL spectrum produced via radical ion annihilation shows good agreement with the fluorescence emission of the compound.