Distributed Bragg reflector laser(1.8 μm) with 10 nm wavelength tuning range

We report a 1.8 μm two-section distributed Bragg reflector laser using butt-jointed In Ga As P bulk material as the waveguide core layer. The threshold current is 17 m A and the output power is 8 m W on average. The threshold current, output power, and emitting wavelength dependences on temperature are measured. The obtained wavelength tuning range is 10 nm. This device has potential applications in simultaneous multiple-gas detection.     

Electrochemical performance of lithium ion capacitors with different types of negative electrodes

The electrochemical properties of various commercial carbon materials (activated carbon (AC), graphite (GP) and hard carbon (HC)) have been investigated for use as negative electrode for lithium ion capacitors. The rate capabilities and cycle durabilities are tested up to 20 C and 1000 cycles using full cell configurations. It is found that the lithium ion could not efficiently intercalate into the activated carbon materials. The symmetrical AC/AC capacitor shows good cycle durabilities at 10 C with capacity of 17 mA h g^?1. The asymmetrical capacitors AC/GP and AC/HC with intercalated negative electrodes show higher capacities than that of AC/AC capacitor. Moreover, the AC/HC has better rate capabilities than AC/GP.     

Electrochemical performance of pre-lithiated graphite as negative electrode in lithium-ion capacitors

Electrochemical performance of the pre-lithiated graphite and the as-assembled lithium-ion capacitors (LICs) were investigated within the Li/graphite two-electrode cell and activated carbon (AC)/graphite two-electrode cell, respectively. The morphologies of the electrodes were characterized by scanning electron microscopy (SEM). The Li intercalation of Li/graphite two-electrode cell was performed using short circuiting and galvanostatic charging techniques. The Li pre-doping process was characterized by electrochemical impedance spectroscopy (EIS). The cycle performance of the LICs were investigated at the rates of 1–20 C between the cut-off voltage at 2 to 4 V. The results demonstrated that the LIC cells with 8 h pre-doping time have the best cycle performance at the high rate of 10 C. Li pre-doping methodology plays a crucial role in the electrochemical performance of the graphite electrode and the as-assembled LICs.     

Synthesis of an adhesion‐enhancing polysiloxane containing epoxy groups for addition‐cure silicone light emitting diodes encapsulant

Addition‐cure silicone resin is considered as a good choice for light emitting diodes (LEDs); however, it has very poor adhesion to the substrate, which limits its practical application. A novel polysiloxane with self‐adhesion ability and higher refractive index for the encapsulating of high‐power LEDs is prepared and characterized. This polysiloxane containing vinyl groups, phenyl groups, and epoxy groups was synthesized by a sol‐gel condensation process from methacryloxy propyl trimethoxyl silane, γ‐(2,3‐epoxypropoxy)propytrimethoxysilane, and diphenylsilanediol under the catalysis of an anion exchange resin. Then, the resin‐type encapsulation material was prepared by hydrosilylation of methylphenyl hydrogen‐containing silicone resin and the newly synthesized polysiloxane material. The novel polysiloxane was characterized by ¹H‐NMR and Fourier transform infrared spectroscopy. On the basis of higher refractive index, higher transparency, excellent thermal stability, and appropriate hardness, as well as good adhesive strength between the encapsulating material and the LED lead frame (polyphthalamide), the curable silicone resin‐type encapsulation material can be used as an encapsulant for LEDs. Copyright © 2014 John Wiley & Sons, Ltd.     

Microcalorimetric investigation on antibacterial activity of the peptide from Plutella xylostella

The antibacterial activities of a kind of novel peptide from Plutella xylostella (pxCECA1) on methicillin-resistant staphylococcus aureus (MRSA) and Escherichia coli (E. coli) growth were investigated by microcalorimetry. The heat flow power–time curves of MRSA and E. coli growth in the presence of pxCECA1 were recorded using the 3114/3115 Thermal Activity Monitor Air Isothermal Calorimeter based on ampoule mode at 37 °C. Some parameters including growth rate constant k, maximum power output P _max, total heat output Q_t, generation time t _g, growth inhibitory ratio I, and half-inhibitory concentration of the drugs IC₅₀ were obtained to elucidate the antibacterial activity of pxCECA1. The results showed that k, P _max, and Q _t decreased, but I and t _g increased or delayed with the increase in pxCECA1 concentration. The IC₅₀ of pxCECA1 on E. coli was 6.122 μg mL^?1 and MRSA was 7.809 μg mL^?1. It could be concluded that pxCECA1 had stronger inhibitory effect on E. coli than MRSA. In vivo test was simultaneously performed using an E. coli and MRSA infection model to validate the antibacterial activity of pxCECA1. The results revealed that pxCECA1 with broad spectrum antimicrobial activities hopefully represented a class of promising substitute of antimicrobial agents.     

Direct Resolution of Enantiomers of DL-Amino Acids by Thin-Layer Chromatography with Vancomycin as Impregnating Agent

JPC – Journal of Planar Chromatography – Modern TLC -     

Enzymatic Desymmetrising Redox Reactions for the Asymmetric Synthesis of Biaryl Atropisomers

Atropisomeric biaryls carrying ortho‐hydroxymethyl and formyl groups were made enantioselectively by desymmetrisation of dialdehyde or diol substrates. The oxidation of the symmetrical diol substrates was achieved using a variant of galactose oxidase (GOase), and the reduction of the dialdehydes using a panel of ketoreductases. Either M or P enantiomers of the products could be formed, with absolute configurations assigned by time‐dependent DFT calculations of circular dichroism spectra. The differing selectivities observed with different biaryl structures offer an insight into the detailed structure of the active site of the GOase enzyme.     

Synthesis of Site‐Specifically Phosphate‐Caged siRNAs and Evaluation of Their RNAi Activity and Stability

A complete set of new photolabile nucleoside phosphoramidites were synthesized, then site‐specifically incorporated into sense or antisense strands of siRNA for phosphate caging. Single caging modification was made along siRNA strands and their photomodulation of gene silencing were examined by using the firefly luciferase reporter gene. Several key phosphate positions were then identified. Furthermore, multiple caging modifications at these key positions led to significantly enhanced photomodulation of gene silencing activity, suggesting a synergistic effect. The caging group on both the terminally phosphate‐caged siRNA and the single‐stranded caged RNA has comparatively high stability, whereas hydrolysis of the caged group from the internally caged siRNA was observed, irrespective of the presence of Mg²⁺. Molecular dynamic simulations demonstrated that enhanced hydrolysis of the caging group on internally phosphate‐caged siRNAs was due to easy fragmentation of the caging group upon formation of the pentavalent intermediate of the phosphotriester with attack by water. The caging group in the terminally phosphate‐caged siRNA or single‐stranded caged RNA prefers to form π–π stacks with nearby nucleobases. In addition to providing explanations for previous observations, this study sheds further light on the design of caged oligonucleotides and indicates the direction of future development of nucleic acid drugs with phosphate modifications.     

Highly Enantioselective Catalytic System for Asymmetric Copolymerization of Carbon Dioxide and Cyclohexene Oxide

A new ligand can be easily prepared, and its intramolecular dinuclear zinc complexes act as a high performance catalyst for the asymmetric alternating copolymerization of cyclohexene oxide and CO₂ under very mild conditions (1 atm CO₂, room temperature), affording completely alternating polycarbonates with up to 93.8 % enantiomeric excess (ee) and 98 % yield. A high M_n value of 28 600 and a relatively narrow polydispersity (M_w/M_n ratio) of 1.43 were also achieved.     

Gold‐Catalyzed Cycloisomerization of Yne‐Vinylidenecyclopropanes: A Three‐Carbon Synthon for [3+2] Cycloadditions

A novel type of yne‐vinylidenecyclopropanes (VDCPs) has been synthesized and applied in gold‐catalyzed cycloisomerization reactions. It was found that these compounds can undergo an intramolecular cycloisomerization and perform as a three‐carbon synthon for [3+2] cycloaddition under gold catalysis to give fused [4.3.0] and [5.3.0] bicyclic derivatives and VDCP rearranged products in moderated to good yields under mild conditions. The substrate scope of these novel transformations has been explored and plausible reaction mechanisms have been presented on the basis of deuterium labeling experiments and DFT calculations.