Effect of overdischarge (overlithiation) on electrochemical properties of LiMn2O4 samples of different origin

Journal of Solid State Electrochemistry - Overdischarge poses a significant threat to the safety and reliability of lithium ion batteries. In this paper, overdischarge (overlithiation) effect on...     

On the reconstruction of the variation of the metric tensor of a surface on the basis of a given variation of christoffel symbols of the second kind under infinitesimal deformations of surfaces in the euclidean space <Emphasis Type="Italic">E</Emphasis><Subscript>3</Subscript>

We investigate the problem of reconstruction of the variation of the metric tensor of a surface on the basis of a given variation of Christoffel symbols of the second kind under infinitesimal deformations of surfaces in the Euclidean space E ₃.     

Evolution of the defect substructure in V-4Ti-4Cr alloy under severe plastic deformation

The evolution of the defect substructure in V-4Ti-4Cr alloy under its severe plastic deformation by torsion in Bridgman anvils is studied by transmission electron microscopy. Nanoband structural states with a dipole or multipole character of misorientations and a crystallite (or nanoband) size varying from several to several tens of nanometers form in the true logarithmic strain range e ≈ 3.0−6.6. Such crystallites form inside 100-nm submicrocrystallites or coalesce (at e ≥ 6) to yield mesobands with a pronounced vortex character of their propagation. The formation of these states is related to the activation (by the flows of nonequilibrium point defects in stress fields) of quasi-viscous deformation and lattice reorientation mechanisms, which provide the generation and propagation of partial disclination nanodipoles followed by the development of collective effects in a disclination substructure. These effects lead to the group motion of nanodipoles inside the mesobands.     

Catalytic oxidation of toluene by ozone in the acetic acid-sulfuric acid system

Oxidation of toluene by ozone was studied in the system constituted by acetic and sulfuric acids in the presence of manganese(II) acetate and sodium bromide. The effect of sulfuric acid and the catalyst on the yield of benzoic acid and on the oxidation rate was considered. The optimal ozonization conditions were determined. A scheme of redox catalysis that accounts for experimental data was suggested.     

Structure and composition of gallium nitride films produced by processing gallium arsenide single crystals in atomic nitrogen

Thin GaN films are grown on (001) single-crystal GaAs substrates processed in an atmosphere of active nitrogen radicals. Auger electron spectroscopy is applied to take the depth profiles of the basic chemical elements that enter into the composition of the epitaxial GaN films and single-crystal GaAs substrates. It is found that the surface composition of the GaN films is characterized by considerable nonstoichiometry (the excess nitrogen achieves ≈9%), which is caused by the presence of atomic nitrogen in the discharge chamber. With a high-resolution X-ray diffraction method, the structural perfection of the epitaxial layers is investigated. It is shown that low-temperature annealing (at temperatures below 700°C) is responsible for the formation of cubic GaN films on the (001) surface of cubic GaAs, whereas higher temperature annealing results in the growth of the hexagonal films.     

Characterization of Photodegradation of Meta-tetra (Hydroxyphenyl)chlorin (mTHPC) in Solution: Biological Consequences in Human Tumor Cells

The photobleaching of meta -tetra(hydroxyphenyl)chlorin m THPC) (irradiation wavelength 413 nm) in protein-containing solution was evaluated by decay in absorbance in Soret band and in fluorescence (λ_exc= 423 nm, λ_em= 655 nm). Light exposure resulted in a decrease in absorption throughout the spectrum and simultaneous appearance of new absorption bands in the spectral region 325–450 nm. The rate of m THPC photodegradation, followed by decay in absorbance, was 15-fold lower than that observed in fluorescence. This fact reflects the photobleaching of presumably monomeric, fluorescing species of m THPC. In order to determine the consequences of photobleaching of fluorescing m THPC material on cellular uptake and photocytotoxicity, human HT29 colon adenocarcinoma cells were incubated with photobleached m THPC during 5 h with or without following irradiation with the fixed fluence. Surprisingly, but up to the time when the fluorescence decreased by 50%, only a slight decrease in photocytotoxicity was detected. Either aggregated forms that have been taken up undergo intracellular monomerization (but we did not observe increase in fluorescence in living cells) or the photodynamic activity is mostly due to aggregates. The discrepancy of m -THPC-photodynamic therapy (PDT) effect and fluorescence measurements may suggest that aggregated m -THPC plays an important role in m THPC-PDT.     

Photohemolysis Sensitized by the Furocoumarin Derivative Alloimperatorin and its Hydroperoxide Photooxidation Product

The dark and photosensitized effects of alloimperatorin methyl ether 1 (hereafter simply alloimperatorin) and its photooxygenation product alloimperatorin hydroperoxide 2 were investigated on human erythrocytes. The results reveal that the furocoumarin 1 photosensitizes efficiently the hemolysis of erythrocytes. The rate of photohemolysis increases on raising the temperature of the postirradiated incubation from 4°C to 37°C. Thermal activation of the photohemolysis and inhibition by 2,6‐di‐tert‐butyl‐p‐cresol (BHT) suggest that the furocoumarin 1 photosensitizes lipid peroxidation, increasing permeability in the erythrocyte membrane. The hydroperoxide 2 induces dark and photosensitized hemolysis more efficiently than the furocoumarin 1. The rate of hemolysis induced by 2 increases with the incubation temperature and decreases in the presence of tert‐butanol and BHT. The hydroperoxide 2 photosensitizes the formation of lipid peroxidation products as shown by the reaction with thiobarbituric acid. This process is diminished by BHT. Our data imply that the photohemolysis sensitized by the furocoumarin 1 is caused by the in situ‐formed photooxygenation product 2. Such hydroperoxides are potent hemolytic agents in the dark and especially on photosensitization.     

Stress Distribution Around a Crack in Plane Micropolar Elasticity

In this paper we formulate the boundary value problem of plane micropolar elasticity for a domain containing a crack in Sobolev spaces and prove the existence and continuous dependence on the data of the corresponding weak solutions. We consider the cases of both finite and infinite domain and find the solutions in terms of modified single layer and modified double layer potentials with distributional densities.      

Systemic suppression of the contact hypersensitivity by the products of protoporphyrin IX photooxidation

Photodynamic therapy (PDT) is frequently accompanied by induction of systemic immunosuppression. Photochemical mechanisms underlying this effect are not completely understood. Here, we demonstrate the immunosuppressive activity of photooxidation products of protoporphyrin IX dimethyl ester (PPIX) in a murine model of contact hypersensitivity (CHS) to 2,4-dinitrofluorobenzene (DNFB). Intravenous injection of the preirradiated solution of PPIX to mice resulted in fluence-dependent suppression of the CHS. The samples of photodecomposed PPIX with suppressive effect on the CHS contained chlorin-type products, namely, two isomers of photoprotoporphyrin (pPP1 and pPP2) as main photoproducts. Concentration-dependent suppression of the CHS was also induced when purified pPP1 or pPP2 were injected to mice intravenously. These purified photoproducts exerted equal immunosuppressive activity. The highest suppression of the CHS was induced when pPP1 was injected 20 h before sensitization with DNFB. The lowest suppression was at its injection time 24 h before challenge. The pPP1-induced suppression of the CHS was adoptively transferable and was associated with generation of cells with suppressive functions. These suppressor cells inhibited the efferent phase of the CHS. Our results strongly indicate that induction of systemic immunosuppression by PDT with PPIX may proceed through photobleaching of photosensitizer and generation of photoprotoporphyrins, which can affect T cell immunity.