Hydrogen evolution across nano-Schottky junctions at carbon supported MoS2 catalysts in biphasic liquid systems

The activities of a series of MoS(2)-based hydrogen evolution catalysts were studied by biphasic reactions monitored by UV/Vis spectroscopy. Carbon supported MoS(2) catalysts performed best due to an abundance of catalytic edge sites and strong electronic coupling of catalyst to support.     

Algebraic equations on the adèlic closure of a Drinfeld module

Let k be a field of positive characteristic and K = k(V) a function field of a variety V over k and let A _K be the ring of adèles of K with respect to the places on K corresponding to the divisors on V. Given a Drinfeld module $\Phi :\mathbb{F}[t] \to End_K (\mathbb{G}_a )$ over K and a positive integer g we regard both K ^g and A _K ^g as $\Phi \left( {\mathbb{F}_p [t]} \right)$ -modules under the diagonal action induced by Φ. For Γ ? K ^g a finitely generated $\Phi \left( {\mathbb{F}_p [t]} \right)$ -submodule and an affine subvariety $X \subseteq \mathbb{G}_a^g$ defined over K, we study the intersection of X(A _K ), the adèlic points of X, with $\bar \Gamma$ , the closure of Γ with respect to the adèlic topology, showing under various hypotheses that this intersection is no more than X(K) ∩ Γ.     

一种HBV多聚酶基因检测系统的光学系统设计

基于荧光偏振理论,设计了一套HBV多聚酶基因检测光学系统。该光学系统包括荧光激发系统和荧光检测系统。使用荧光激发系统对激发样品产生荧光,由荧光检测系统对荧光进行水平和垂直两个方向的荧光强度检测,从而获得荧光的偏振度。通过更换该套系统中的滤光片可实现对400～550nm范围内的样品荧光偏振度的检测。运用该光学系统进行了临床实验,结果表明,系统测试方法具有简单易行、灵敏度高、精确可靠、抗干扰能力强的特点。     

Meromorphic groups

We show that a connected group interpretable in a compact complex manifold (a meromorphic group) is definably an extension of a complex torus by a linear algebraic group, generalizing results of Fujiki. A special case of this result, as well as one of the ingredients in the proof, is that a strongly minimal modular meromorphic group is a complex torus, answering a question of Hrushovski. As a consequence, we show that a simple compact complex manifold has algebraic and Kummer dimension zero if and only if its generic type is trivial.

     

Study of oxygen ion transport in acceptor doped samarium cobalt oxide

Dense samples of the perovskite Sm_1−xSr_xCoO₃ (where x=0, 0.2, 0.4, 0.5 and 0.6) have been prepared. The samples were¹⁸O/¹⁶O isotopically exchanged at a variety of temperatures between 500°C and 900°C. Subsequent analysis of the diffusion profile using Secondary Ion Mass Spectrometry (SIMS) allowed the oxygen self-diffusion coefficient, D*, and surface exchange co-efficient, k, to be determined. From the temperature dependence of these parameters the activation energies for both processes were evaluated. The surface coverage of samarium, cobalt and oxygen in SmCoO₃ was determined from calibration samples using Low Energy Ion Scattering (LEIS). LEIS was used to determine the effect of strontium doping on the surface composition and the¹⁸O-concentration at the surface of a number of the¹⁸O-exchanged samples. Paper presented at the 1st Euroconference on Solid State Ionics, Zakynthos, Greece, 11 – 18 Sept. 1994.     

Gas phase radiation chemistry of hexafluoroethane

The Co-60 gamma radiolysis of gaseous C₂F₆ was investigated at 50 Torr pressure, both pure and with 10% oxygen added. For the pure system, the radiolytic products and their respective C values were CF₄, 2.27; C₃F₈, 0.23; C₄F₁₀, 0.09; C₅F₁₂, 0.015; and C₆F₁₄, 0.009. All radiolysis products except for CF₄ (C = 0.61) were eliminated when 10% O₂ was added as scavenger. The results are discussed mainly in terms of the decomposition of excited C₂F₆ into free radicals, which can then combine. The unscavenged CF₄ is accounted for by the ion-molecule reaction CF₃⁺ + C₂F₆ → CF₄ + C₂F₅⁺.     

In situ studies of electrode reactions: The mechanism of lithium intercalation in TiS2

The mechanism of lithium intercalation into TiS₂ is poorly understood even though the system Li_xTiS₂ (0 ? x ? 1) has been extensively studied. This mechanism is critical in the functioning of $\text{Li}\text{TiS}{}_2$ nonaqueous batteries. In this report we describe several techniques which are used to study this mechanism. These methods consist of ex situ and in situ optical and X-ray techniques which yield information regarding the mechanism of lithium intercalation and factors which effect this process during the operation of $\text{Li}\text{TiS}{}_2$ batteries.     

A soft on/off switch based on the electrochemically reversible H–J interconversion of a floating porphyrin membrane

Soft molecular assemblies that respond reversibly to external stimuli are attractive materials as on/off switches, in optoelectronic, memory and sensor technologies. In this Edge Article, we present the reversible structural rearrangement of a soft porphyrin membrane under an electrical potential stimulus in the absence of solid-state architectures. The free-floating porphyrin membrane lies at the interface between immiscible aqueous and organic electrolyte solutions and is formed through interfacial self-assembly of zinc(ii) meso-tetrakis(4-carboxyphenyl)porphyrins (ZnPor). A potential difference between the two immiscible electrolyte solutions induces the intercalation of bis(triphenylphosphoranylidene)ammonium cations from the organic electrolyte that exchange with protons in the porphyrin membrane. In situ UV/vis absorbance spectroscopy shows that this ionic intercalation and exchange induces a structural interconversion of the individual porphyrin molecules in the membrane from an H- to a J-type molecular configuration. These structural rearrangements are reversible over 30 potential cycles. In situ polarisation-modulation fluorescence spectroscopy further provides clear evidence of structural interconversion of the porphyrin membrane, as intercalation of the organic electrolyte cations significantly affects the latter''s emissive properties. By adjusting the pH of the aqueous phase, additional control of the electrochemically reversible structural interconversion can be achieved, with total suppression at pH 3.

The structural rearrangement of a porphyrin membrane self-assembled at a “soft” liquid|liquid interface from a H- to J-molecular configuration is reversibly modulated by externally manipulating the interfacial Galvani potential difference.     

2‐Nitroveratryl as a Photocleavable Thiol‐Protecting Group for Directed Disulfide Bond Formation in the Chemical Synthesis of Insulin

Chemical synthesis of peptides can allow the option of sequential formation of multiple cysteines through exploitation of judiciously chosen regioselective thiol‐protecting groups. We report the use of 2‐nitroveratryl (oNv) as a new orthogonal group that can be cleaved by photolysis under ambient conditions. In combination with complementary S‐pyridinesulfenyl activation, disulfide bonds are formed rapidly in situ. The preparation of Fmoc‐Cys(oNv)‐OH is described together with its use for the solid‐phase synthesis of complex cystine‐rich peptides, such as insulin.     

Characterization of the N-methyltransferase activities of the multifunctional polypeptide cyclosporin synthetase

This study demonstrates a critical role for N-methylation in cyclosporin biosynthesis and maintenance of the biologically active cyclosporin conformation. The structural requirements for the AdoMet binding to CySyn were defined. N-methylation of specific amide positions in the cyclosporin backbone is critical for the complete assembly and cyclization of the cyclosporin peptide. A maximum of two desmethyl positions is tolerated before peptide assembly stalls. Subinhibitory concentrations of AdoMet analogs directed peptide assembly towards cyclosporins with less than seven N-methylated amide bonds. Molecular modeling and nuclear magnetic resonance analyses indicate that N-methylation of specific amide bond positions in the cyclosporin backbone is mandatory for the formation of a product-like conformation and recognition by the acceptor site of the downstream peptide bond forming C-domain.