The effect of TiO<Subscript>2</Subscript> coating on the electrochemical performance of ZnO nanorod as the anode material for lithium-ion battery

ZnO nanorods were coated with TiO₂ thin film using the atomic layer deposition (ALD) process. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used to characterize the crystal structure and surface morphology of the coated composites. Results of galvanostatic charge and discharge tests and cyclic voltammograms suggest that lithium ions can reversibly intercalate into and deintercalate from TiO₂-coated ZnO nanorods, and that stable cycling behavior in an ethylene carbonate-based electrolyte can be achieved. The TiO₂ coating is believed to reduce the degree of reaction electrodes have with the electrolyte during the charge–discharge process since the inactive coating layer prevents the electrode from having direct contact with the electrolyte. Furthermore, the one-dimensional nanorods provide a relatively higher surface area than those of their bulk form or thin film, which allows a much greater portion of atoms on the surface to undergo the electrochemical reaction. The electrochemical study indicates that the TiO₂-coated ZnO nanorod arrays might be a candidate for the anode material in Li-ion batteries.     

The mechanism of Zn-phthalocyanine photosensitized lysis of human erythrocytes

The phthalocyanines have recently been suggested as one of most effective possible sensitizers for photodynamic therapy and the blood viral inactivation. The further characterisation of the mechanism of human red blood cell lysis and membrane alterations upon photodynamic treatment in the presence of Zn-phthalocyanine was the aim of this study. It was found that there were (2.7+/-0.4).10(7) dye binding sites per red blood cell with the association constant equal to (1.4+/-0.3).10(4) M(-1). Two types of the photosensitized haemolysis: haemolysis during irradiation ("light" haemolysis) and post-irradiation haemolysis ("dark" haemolysis) were studied. The erythrocyte membrane hyperpolarisation, membrane fluidisation and cell swelling preceded the "light" haemolysis. The modification of the erythrocyte membrane band 3 protein by DIDS (an inhibitor of anion exchange) increased the rate of the "light" haemolysis. The rate of "dark" haemolysis was higher and that of "light" haemolysis was lower in potassium media in comparison to sodium ones. The rates of photohaemolysis depended on the erythrocyte membrane potential: a decrease of membrane potential inhibited both types of haemolysis. The cell shrinkage in the presence of sucrose (up to 15 mM) inhibited the "dark" haemolysis but significantly increased the "light" haemolysis. Oxidation of intracellular oxyHb to metHb by nitrite, which drastically decreases intracellular oxygen concentration, as well as GSH concentration, inhibited the rate of the "light" haemolysis. The results allow for the conclusion that the mechanism of photochemical ("light") haemolysis is not of a colloid-osmotical type, in contrast to the post-irradiation ("dark") haemolysis. The photochemical oxidation or denaturation of band 3 protein plays a significant role in the formation of haemolytic holes. The membrane lipid peroxidation, as well as glutathione oxidation, does not participate in the process of photosensitized haemolysis. From the inhibition of "dark" haemolysis by sucrose the apparent pore radius was estimated to be about 1.1 nm. The pores appear to be transient short-lived ones, the average pore number per cell was 0.02.     

The Diophantine equation

Let be a rational prime and a positive rational integer coprime with . Denote by the number of solutions of the equation in rational integers and . In a paper of Le, he claimed that without giving a proof. Furthermore, the statement has been used by Le, Bugeaud and Shorey in their papers to derive results on certain Diophantine equations. In this paper we point out that the statement is incorrect by proving that .

     

Oxidation of Benzylic Methyl Groups by Supported MnO2/Al2O3 Oxidant

An investigation of benzylic oxidations with manganese dioxide supported on neutral alumina has been carried out. Isolation of intermediated products, which is possible in some cases, gives strong support for the reaction mechanism proposed. With 2,6-di-tert-butyl-4-methylphenol, 4,4′-dihydroxy-3,5,3′,5′-tetra-tert-butyldiphenylmethane,2,6-di-tert-butylphenol and 4-methyl-phenol, selective formation of essentially a single product in excellent yield was obtained.     

Resistant starch and colorectal neoplasia

There are several approaches to examining the relationship between resistant starch (RS) and development of colorectal cancer (CRC). These include examination of epidemiological relationships, objective testing of effects of RS given to humans on biological events of relevance to CRC, and studies in animal models where protection and mechanisms of protection can be directly tested. Nine epidemiological studies have examined the relationship between starch and CRC and/or adenomas. Most show a significant protective effect. However, epidemiological tools for measuring consumption of RS are poorly developed and so a benefit for RS can only be inferred. On balance, the magnitude of protection by starch appears to be in the order of 25-50%. Human intervention studies have examined the effect of various types and amounts of RS consumption on colonic biology. To generalize from these studies, RS softens stools and increases stool bulk, decreases pH, increases short-chain fatty acids (SCFAs) including butyrate, reduces products of protein fermentation, and decreases bile salts in fecal water. Such changes seem to be achieved within about 4 weeks of commencing consumption. The greatest effects are seen with the highest doses where increased fecal starch recovery is observed. A modest number of animal studies have been undertaken. Those examining effects of RS on colonic biology and biomarkers for CRC confirm and extend the results in humans. RS modifies the lumenal environment, largely through altered fermentation of polysaccharides and proteins. RS also affects epithelial biology in that it increases apoptotic deletion of genetically damaged cells. More work is needed to define what types and combinations of RS, perhaps with probiotics, exert the greatest effects on colonic environment and epithelial biology, and then to test these in the cancer models for their protective effect. A few studies have examined effect of RS on cancer as an end point in several rodent models, but the results are not clear cut. In conclusion, consumption of RS dramatically affects the colonic lumenal environment and facilitates apoptotic deletion of genetically damaged cells in the colon, several of which are considered to be biomarkers associated with risk for CRC. These effects can be interpreted as reflecting improved colonic health, which might be of benefit in protection against CRC. Direct evidence for protection is still not available.     

Bidentate NHC-based chiral ligands for efficient Cu-catalyzed enantioselective allylic alkylations: structure and activity of an air-stable chiral Cu complex

Cu-catalyzed addition of alkylzinc reagents to a range of allylic phosphates is promoted efficiently and with high enantioselectivity to afford tertiary as well as quaternary carbon centers (up to 98% ee). Reactions proceed to completion with 0.5-5 mol % catalyst loading and are best promoted by commercially available CuCl2.2H2O. The X-ray structure of the chiral NHC-Ag(I) complex used in the study as well as that of a catalytically active NHC-Cu(II) complex are also reported; both complexes are air-stable and are formed in >/=95% isolated yield. The isolated Cu complex, which can be handled in air, is catalytically active. The present report provides the first precedent for efficient Cu-catalyzed allylic alkylations with chiral NHC ligands.     

Fixed and pulsed gradient diffusion methods in low-field core analysis

We review diffusion-weighted relaxation protocols for two-dimensional diffusion/relaxation time (D, T(2)) distributions and their application to fluid-saturated sedimentary rocks at low fields typical of oil-well logging tools (< or = 2 MHz for 1H). Fixed field gradient (FFG) protocols may be implemented in logging tools and in the laboratory; there, pulsed field gradient (PFG) protocols are also available. In either category, direct or stimulated echoes may be used for the diffusion evolution periods. We compare the results of several variant FFG and PFG protocols obtained on liquids and two contrasting sedimentary rocks. For liquids and rocks of negligible internal gradients (g(int)), results are comparable, as expected, for all the studied protocols. For rocks of strong g(int), protocol-dependent artifacts are seen in the joint (D, T2) distributions, consistent with the effects of the internal fields. For laboratory petrophysics, the PFG methods offer several advantages: (a) significantly improved signal-to-noise ratio and acquisition times for repetitions over many samples; (b) freedom from heteronuclear contamination when fluorinated liquids are used in core holders; and (c) a palette of variants--one comparable with the FFG--for the study of rocks of significant g(int). Given suitable hardware, both PFG and FFG methods can be implemented in the same bench-top apparatus, providing a versatile test bed for application in a petrophysical laboratory.     

Surface-emitting second-harmonic generation in AlGaAs/GaAs waveguides

We investigate the impact of waveguide properties on the performance of surface-emitting second-harmonic generation (SESHG) devices. Using multi-layer AlGaAs/GaAs ridge waveguides that are optimized for SESHG at fundamental wavelengths = 1060 and 1550 nm, we achieve nonlinear cross-sections among the highest reported so far. In these devices, characteristics of the guided fundamental wave strongly determine the SESHG performance: multiple reflections in the longitudinal direction affect the conversion efficiency while higher order lateral waveguide modes modify the SESHG farfield. Both effects are significant for applications of SESHG in integrated photonic circuits.     

Kinetics of Oxidation of Diphenylmethane and Derivatives with Ce(IV) in Aqueous Acidic Acetonitrile

In aqueous acidic acetonitrilc solution cerium(IV) oxidizes diphenylmethane (Ph₂CH₂) to produce diphenylmethanol (Ph₂CHOH) first and then benzophenone (Ph₂CO). With the organic reductant in great excess, both the Ce(IV)-Ph₂CH₂ and Ce(IV)-Ph₂CHOH rcactions follow second-order kinetics. The rates of both reactions increase nonlinearly with increasing [H⁺] or with decreasing [H₂O]. Both kinetic and spectrophotometrc results indicate that replacement of water molecules by complex formation through the phenyl or hydroxyl group plays an important role in activating the reaction. Under similar conditions, the order of relative reactivities toward Ce(IV) oxidation is PhCH₂OH > CH₃CH₂OH > Ph2CHOH > Ph₂CH₂ > PhCH₃> (Ph₂CO, C₆H₆). Mechanistic interpretations of the kinetic results are presented.