Influence of added salts on the cage escape yields in the photoredox quenching of Ru(bpy)2+3 excited states

The influence of electrolytes on the photoredox kinetics and cage escape yields of redox products (π_redox) in the quenching of Ru(bpy)^2+*₃ by methylviologen (MV²⁺), Tl^III and Hg^II have been investigated. For all three quenchers π_redox appears to be strongly dependent on the nature of the anion. Photoelectrochemical cells based on the latter systems are described.     

Visible Light Induced Water Cleavage in CdS Dispersions Loaded with Pt and RuO2, Hole Scavenging by RuO2

Illumination of aqueous CdS dispersions loaded with Pt and RuO₂ by visible light produces hydrogen and oxygen in stoichiometric proportion. No degradation of the photocatalyst is noted after 60 h of irradiation time. The RuO₂ deposit on the particle surface greatly accelerates the transfer of holes from the semiconductor valence band to the aqueous solution thus inhibiting photocorrosion.     

In vitro dielectrophoresis of HEK cell migration for stimulating chronic wound epithelialization

This article describes a dielectrophoresis (DEP)-based simulation and experimental study of human epidermal keratinocyte (HEK) cells for wounded skin cell migration toward rapid epithelialization. MyDEP is a standalone software designed specifically to study dielectric particles and cell response to an alternating current (AC) electric field. This method demonstrated that negative dielectrophoresis (N_DEP) occurs in HEK cells at a wide frequency range in highly conductive medium. The finite element method was used to characterize particle trajectory based on DEP and drag force. The performance of the system was assessed using HEK cells in a highly conductive EpiLife suspending medium. The DEP experiment was performed by applying sinusoidal wave AC potential at the peak-to-peak voltage of 10 V in a tapered aluminum microelectrode array from 100 kHz to 1 MHz. We experimentally observed the occurrence of NDEP, which attracted HEK cells toward the local electric field minima in the region of interest. The DIPP-MotionV software was used to track cell migration in the prerecorded video via an automatic marker and estimate the average speed and acceleration of the cells. The results showed that HEK cell migration was accomplished approximately at 6.43 μm/s at 100 kHz with 10 V, and F_DEP caused the cells to migrate and align at the target position, which resulted in faster wound closures because of the application of an electric field frequency to HEK cells in random locations.     

Stretching and collapse of neutral polymer layers under association with ionic surfactants

We provide experimental evidence for stretching and collapse of neutral polymer layers, already adsorbed at an oil-in-water interface, due to its interaction with surfactants. Upon stretching, the first interaction length (2L(0)) follows a power law dependence on surfactant concentration ( proportional, variant C(x)(s), where x approximately 0.5 for cationic surfactants) and collapses in the presence of salt, as a relatively weak power law (C(-y)(s), where y=0.17), in good agreement with brush length decay for polyelectrolyte brushes.     

Base catalyzed rearrangement of some bicyclic ketol acetates.

The ketol $\text{3a}$ and its acetate $\text{3b}$ when refluxed in methanolic potassium hydroxide (5%) were found to rearrange to 4-methyl-8-acetyl-5,6,7,8-tetrahydro-1-naphthol $\text{4}$. The epimeric acetate $\text{3c}$ also behaved likewise. A mechanism is suggested for the rearrangement.     

Synthesis of aza-, oxa-, and thiabicyclo[3.1.0]hexane heterocycles from a common synthetic intermediate

[reaction: see text] An efficient and stereospecific approach to the synthesis of structurally constrained aza-, oxa-, and thiabicyclo[3.1.0]hexane heterocycles has been achieved through application of the intramolecular cyclopropanation reaction of diazoacetates. The various constrained heterocycles (X = N, O, or S) are conveniently prepared from a common diol intermediate accessible from readily available cinnamyl alcohols. Application of the methodology to the synthesis of conformationally constrained oxazolidinone antibacterials is also discussed.     

Effect of addition of a non-equidiffusional reactant to an equidiffusional diffusion flame

A Burke–Schumann (flame-sheet) formulation is developed for diffusion flames between a fuel and oxidiser with Lewis numbers of unity, subject to addition to the fuel and/or oxidiser stream of a different reactant for which the Lewis number differs from unity. This formulation is applied to laminar counterflow diffusion-flame experiments, reported here, in which hydrogen was added to either methane–nitrogen mixtures or oxygen–nitrogen mixtures at normal atmospheric pressure, with both feed streams at normal room temperature. Experimental conditions were adjusted to fix selected values of the stoichiometric mixture fraction and the adiabatic flame temperature, and the strain rate was increased gradually, maintaining the momentum balance of the two streams, until extinction occurred. At the selected sets of values, the strain rate at extinction was measured as a function of the hydrogen concentration in the fuel or oxidiser stream. The ratio of the fraction of the oxidiser flux that consumes hydrogen to the fraction that consumes fuel was calculated from the new Burke–Schumann formulation, and it was found that, within experimental uncertainty, the ratio of the extinction strain rate with hydrogen addition to that without was the same at any given value of this oxygen flux ratio, irrespective of whether the hydrogen was added on the fuel or oxidiser side. This experimental result was also in close agreement with computational predictions employing detailed chemistry. These results imply that differences in detailed hydrogen concentration profiles within the reaction zone have little or no influence on the chemical kinetics of extinction when the stoichiometric mixture fraction, the adiabatic flame temperature, and the proportion of oxygen that consumes the added fuel are fixed. This same correspondence may be expected to apply for other fuels and additives.     

A mild and efficient method for the oxidation of benzylic alcohols by two-phase electrolysis

Electrochemical oxidation of benzylic and substituted benzylic alcohols by two-phase electrolysis yields the corresponding aldehydes as products. The reaction was carried out in a single compartment cell with platinum electrodes at room temperature in chloroform using an aqueous sodium bromide solution (25%) containing a catalytic amount of HBr. The two-phase electrolysis resulted in high yields (74-96%) of benzaldehyde from primary alcohols and secondary alcohols were oxidized to the corresponding ketone but only in low yields under these conditions.