Lipase TL-mediated kinetic tesolution of 5-benzyloxy-1-tert-butyldimethylsilyloxy-2-pentanol at low temperature: concise asymmetric synthesis of both enantiomers of a piperazic acid derivative

Lipase TL-mediated kinetic resolution of (+/-)-5-benzyloxy-1-tert-butyldimethylsilyloxy-2-pentanol (5) at low temperature proceeded to give the corresponding (S)-alcohol 5 and (R)-acetate 6 in quantitative yields with high enantiomeric purity. The addition of bases such as pyridine, DMAP, 2,4- and 2,6-lutidines, or triethylamine considerably enhanced the rate of kinetic resolution. The alcohol (S)-5 and the acetate (R)-6 were converted to piperazic acid derivatives (R)- and (S)-3, respectively, via the intramolecular Mitsunobu reaction as a key step.     

Novel synthesis of highly active Pt/C cathode electrocatalyst for direct methanol fuel cell

A 40 wt% Pt/C cathode electrocatalyst with controlled Pt particle size of approximately 2.9 nm showing better performance than commercial catalyst for direct methanol fuel cell was prepared by a polyol process with water but without using stabilizing agent.     

Synthesis of a new insoluble polymer-supported chiral alcohol auxiliary and its first application to nucleophilic addition to ketenes

The preparation of a new optically active alcohol with a carboxylic function that allowed its attachment to an amine-functionalized insoluble polymer is described. Its first use as a polymer supported chiral auxiliary is demonstrated by asymmetric transformation of two racemic aryl propionic acids via ketene formation (95-96% ee).     

Synthesis of main‐chain poly(carbazole)s via CuAAC

The synthesis and characterization of a novel family of main‐chain carbazole‐containing polymers using copper‐catalyzed azide‐alkyne cycloaddition chemistry is reported. The reactions were performed under mild conditions using readily available copper catalysts and ligands, which afforded polymeric products with M_ws up to 18 kDa. Using a range of techniques, the polymers were found to exhibit a glass transition temperature (T_g) of 85 °C, high thermal stability (T_d = 274 °C), and high photoluminescent quantum efficiency (?_f = 0.29; λ_em = 448 nm), which underscore their potential for use in organic light‐emitting diodes or other emissive devices, particularly where efficient blue emission is of value. The approach described offers practical advantages over other synthetic methods used to prepare main‐chain carbazole‐containing polymers, especially with regard to the lack of need for rigorously inert conditions and the absence of byproducts generated during the polymerization reaction. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Mode decomposition of a noise suppressed mixing layer

Noise is generated in atwo-dimensional mixing layer due to the growing of instability waves and vortex pairings. The adjoint-based control methodology has shown to be arobust tool to suppress noise radiation. The mode decomposition algorithms such as the compressible versionof proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) are employed toanalyze thespatial/spatial-temporal coherent structures for a consecutive data sets of the controlled mixing layer and itsuncontrolled counterpart. The analyses of POD indicate that the y-direction body forcecontrol mainly modify themost energetic spatialstructures, and increase the uniformity of the flow. The analyses of DMD show us prevalent frequencies andcorresponding mode structures, and the stability characteristics of each mode can be obtained fromDMD-spectrum. The spectral signatures illustrate that a lot of neutral/slightly damping modesemerging in uncontrolled flow within the frequency range (ω < 0.4) are suppressed due to control, relevant spatial-temporal structures are also varied, which iscoincident with the change of far-field noise spectra. From the view of mode decomposition, the action of control redistribute the energy forfrequency components of ω < 0.4 by weakening nonlinearities and regularizing corresponding dynamicstructures in streamwise direction, and thus suppress the noise radiation. Moreover, the POD- and DMD-analysis in this studydemonstrate that DMD can serve as an important supplement for POD in analyzing a time-resolved physicalprocess.     

激光器机理及激光功率表达式的实验验证

运用光反馈的原理和技术演示并验证激光功率表达式，说明激光介质和光学谐振腔的性质和作用。     

One Pot Synthesis of Amphiphilic Hyperbranched Poly-(amino ester)and Its Dynamic Surface Activity

Amphiphilic hyperbranched poly(amino ester)s with hydrophilic multi‐ethoxylated triacrylate backbone and hydrophobic long alkyl side chain were firstly synthesized via one pot Michael addition polymerization. The poly‐(amino ester) could dissolve in cold water and self‐assemble into loose micelle. Under 50–1000 ms bubble, the dynamic surface tension (DST) of the poly(amino ester) aqueous solution (0.5 wt%) still maintained in the range of 32–28 mN/m. The aqueous solutions of poly(amino ester)s with different molecular weights showed the lower critical solution temperature (LCST) in the range of 8–50°C, which could also be tuned by its pH. Capped with hydrophobic groups on the terminal units and partially neutralized with acid, the poly(amino ester)s still kept their stable dynamic surfactant behaviors, indicating promising application.     

β-NMR in II–VI semiconductors

β-active probe nuclei are implanted in nominally undoped ZnSe crystals. β-radiation detected nuclear magnetic resonance (β-NMR) studies are described for two different probe nuclei, ⁸Li and ¹²B. This way, the implantation behavior of two “opposite”dopants, one acceptor (Li) and one donor (B) can be characterized by the same microscopic technique. Such characterizations are attempted in terms of the structure of intermediate or final lattice sites, defect charge states, or the kinetics of defect reactions and site changes. This revised version was published online in July 2006 with corrections to the Cover Date.