Applications of the channel flow cell for UV-visible spectroelectrochemical studies. Part 2: Transient signals

The use of the channel flow cell for ultraviolet-visible (UV-vis) spectroelectrochemical experiments has been developed to determine the diffusion coefficients of electrogenerated species by means of monitoring the transient absorbance response resulting from a potential step at a working electrode immediately upstream of the incident spectrophotometric beam. The technique is applied to measure the diffusion coefficient of tris(4-bromophenyl)amine (TBPA) radical cation in acetonitrile at 25°C. It is shown that the diffusion coefficient of electrogenerated TBPA radical cation (1.64 ± 0.02 × 10⁻⁵ cm² s⁻¹) is very close to that of the parent molecule (1.57 ± 0.03 × 10⁻⁵ cm² s⁻¹).     

Conformation and absolute configuration of nocathiacin I determined by NMR spectroscopy and chiral capillary electrophoresis

Nocathiacin I (BMS-249524) is a highly cross-linked thiazolyl peptide that displays potent activity against Gram-positive bacteria, including a number of antibiotic-resistant strains. This natural product contains 10 chiral centers. NMR studies have been performed to characterize the solution structure of nocathiacin I. A uniformly 13C,15N-labeled sample was used to obtain NMR assignments. Restrained simulated annealing calculations were performed by using accurately determined NOE distance restraints. All of the chiral centers were allowed to float during the simulated annealing protocol. Two clusters of structures were obtained that satisfy the NOE restraints very well and that are reasonably consistent with vicinal J-coupling constants. Within each cluster, all 10 chiral centers are uniquely defined. The two clusters are effectively mirror images of each other: all chiral centers that have the R(S) configuration in one cluster have the S(R) configuration in the other. The single threonine residue in nocathiacin I was subsequently determined to be l-threonine by chiral capillary electrophoresis, allowing the absolute configurations of all 10 chiral centers to be defined.     

“手”望相助，志虑忠“醇”

Through three stories about alcohol antiseptics, "hand" messengers, characters of the article find the best choice of alcohol, and method of application. This article introduces proper ways to use alcohol antiseptics in daily life from the following three aspects. The ethanol and propanol can be used, the best concentration for daily use is 70%, and the optimal use of alcohols is considered under different circumstances.     

Synthesis of (Alkynyl)phenyl Porphyrins by Palladium Catalysed Cross Coupling Reactions

meso-para and meso-meta-(phenyltriflate)tritolyl porphyrins and the zinc complexes are coupled with alkynyl stannanes or terminal alkynes with palladium catalyst to give the meso-para and meta(m-alkynylphenyl)tritolylylkphenyl porphyrins as well as the zinc complex in good yields.     

Effect of the Water Quenched Slag‐epoxy Resin Composite on Microwave Absorbing Properties

Although in recent years, the ash residues produced from municipal solid waste incinerators (MSWI) in Taiwan have been decreased gradually due to the public awareness of waste classification, it is still necessary to find a suitable landfill site to dispose these wastes safely and economically. For this reason, the plasma melting technology was selected to convert the unwanted ash residues into harmless water quenched slag. More importantly, the effect of the dielectric and magnetic properties of microwave absorber composed of water quenched slag‐epoxy resin composite was studied. The absorbing performance of water quenched slag‐epoxy composites at same sample thickness and at various sample thickness were also studied by measuring complex permittivity, complex permeability and reflection loss in the 2–18 and 18–40 GHz microwave frequency range using the free space method. It was found that the optimum thickness of absorber needed to yield the best reflection loss could be obtained and an absorption frequency range shifting at the frequency range of 2–18 and 18–40 GHz.     

Fabry-Perot optical fiber tip sensor for high temperature measurement

We propose a novel Fabry-Perot optical fiber tip sensor for high temperature measurement. The sensor consists of a short section of a special all-silica photonic crystal fiber spliced at one end to a silica single-mode fiber. Because of its all-silica structure, the sensor allows linear and stable measurements of temperature up to 1200 °C with a high sensitivity. The sensor is easy and inexpensive to fabricate and could find wide applications in mechanics, aeronautics, and metallurgy.     

A margin scheme that advises on when to change required margin

The purpose of a margin requirement is to protect a clearinghouse from members’ defaults resulting from big losses due to adverse movement of futures prices. To decide on how much a margin is required, a clearinghouse may refer to a benchmark margin defined as a constant multiple of the forecasted volatility. However, a benchmark margin only advises on a desirable margin level. It gives no advice on whether a clearinghouse should alter existing required margin. This paper proposes a margin scheme that can advise on when to change the required margin and if a change is recommended, to what level it should be changed. The proposed margin scheme can be devised so that the coverage probability and change frequency are controlled at target levels deemed appropriate by the clearinghouse. The proposed margin scheme needs a volatility forecast as input. This paper shows that among a large number of volatility forecasts, implied volatility gives the best results. This confirms a conjecture that implied volatility may have more information content than other volatility forecasts as far as margin setting is concerned.     

Strongly Phosphorescent Neutral Rhenium(I) Isocyanoborato Complexes: Synthesis,Characterization, and Photophysical,Electrochemical, and Computational Studies

A new series of neutral isocyanoborato rhenium(I) diimine complexes [Re(CO)₃(N^N)(CNBR₃)], where N^N=bpy, 4,4′‐Me₂bpy, phen, 4,7‐Me₂phen, 2,9‐Me₂phen, 3,4,7,8‐Me₄phen; R=C₆F₅, C₆H₅, Cl, 4‐ClC₆H₄, 3,5‐(CF₃)₂C₆H₃, with various isocyanoborate and diimine ligands of diverse electronic and steric nature have been synthesized and characterized. The X‐ray crystal structures of six complexes have also been determined. These complexes displayed intense bluish green to yellow phosphorescence at room temperature in dichloromethane solution. The photophysical and electrochemical properties of these complexes had been investigated. To elucidate the electronic structures and transitions of these complexes, DFT and TD‐DFT calculations have been performed, which revealed that the lowest‐energy electronic transition associated with these complexes originates from a mixture of MLCT [dπ(Re)→π*(N^N)] and LLCT [π(CNBR₃)→π*(N^N)] transitions.