Angular distributions of channeled pions and protons up to 250 GeV/c

Channeling phenomena are observed for positive particles of momentum up to 250 GeV/c in a germanium crystal. The polar angular distributions of the channeled particles are compared with theoretical predictions based on a diffusion model. The results indicate that at high particle energy there may be additional mechanisms besides those operative at low energy leading to dechanneling of the particles. In spite of this, channeling effects are observed for particles incident at up to several times the critical angle, in contrast with the results from low energy channeling. Statistical equilibrium in the azimuthal angular distribution has also been observed at all measured beam momenta to about twice the calculated channeling critical angle. The breakdown of statistical equilibrium for the 2 cm crystal used occurs at an incident angle 2–3 times smaller than predicted theoretically.     

Inhibition of acidic corrosion of carbon steel by some mono and bis azo dyes based on 1,5 dihydroxynaphihalene

Inhibition of the corrosion of carbon steel in hydrochloric acid solution by some mono- and bis-azo dyes based on 1,5-dihydroxynaphthalene was studied in relation to the concentration of inhibitors using weight loss and potentiostatic polarization techniques. The percentage inhibition efficiency calculated from two methods is in a good agreement with each other. The inhibition mechanism of the additives was ascribed to the formation of complex compound adsorbed on the metal surface. The adsorption process follows Freundlich adsorption isotherm. The formation of the complex compound was studied by conductometric and potentiometric titrations. The stability constants of the Fe-complexes were determined using the latter technique and related to the inhibition efficiency.     

A robust combination of dysprosium vanadate/halloysite nanotubes: the electrochemical system for dimetridazole detection

Dimetridazole (DMD) is one of the significant antibiotic drugs of nitroimidazoles derivates that have attracted increasing attention in the medical field due to its pharmacological and toxicological activity. The development of high-performance sensors for continuous monitoring of DMD in food and environments is receiving increasing attention. Herein, an electrochemical platform was designed based on a dysprosium vanadate/halloysite nanotubes (DyV/HNTs) nanocomposite for the detection of DMD. The DyV/HNTs nanocomposite was examined by various spectroscopic and analytical techniques. The DyV/HNTs based electrochemical sensor reveals a distinctly higher electrocatalytic response to the reduction of DMD due to the good physiochemical properties compared to other electrodes. The DyV/HNTs based electrochemical sensor for DMD covered two linear ranges of 0.001–0.54 and 0.54–188 μM with a detection limit of 0.9 nm through the amperometric method, which is better than those previously reported. Furthermore, selectivity, stability, repeatability, and reproducibility studies were performed. Moreover, the fabricated DyV/HNTs sensor was successfully applied for the reliable discrimination of DMD in biological and water samples with satisfactory recovery values. The results indicated that this DyV/HNTs nanocomposite may be a promising electrochemical sensing platform for the determination of DMD.     

Rice straw and energy reed fibers reinforced phenol formaldehyde resin polymeric biocomposites

Cellulose - Herein, natural fiber (energy reeds and rice straw) reinforced with phenol formaldehyde (PF) polymeric resin biocomposites are developed and reported in this study. The dimensions of...     

Novel HPTLC-densitometric method for concurrent quantification of linalool and thymol in essential oils

Monoterpenes, linalool and thymol have been widely used in not only the treatments of several diseases but also food flavouring, dental, perfumery, and toilet products. Plants of the several Lamiaceae family are good sources of linalool and thymol. A rapid, simple, and precise high-performance thin layer chromatography (HPTLC) method was developed for the concurrent estimation of linalool and thymol, and this method was orchestrated using the essential oils extracted from two Lamiaceae plants leaves i.e. O. basilicum and T. vulgaris. Two standards were separated using pre-coated thin-layer chromatography glass plates. The developed HPTLC method was validated by following ICH guidelines (linearity; limit of detection, LOD; limit of quantitation; specificity; accuracy; precision; and robustness). The calibration curves of both the compounds were linear (100–700 ng/spot), with a correlation coefficient (r²) of >999. The developed HPTLC method was effectively applied to the concurrent detection and quantification of linalool and thymol in commercial essential oils.     

Anomalous Metallic State of Cu0.07TiSe2: an optical spectroscopy study

We report an optical spectroscopy study on the newly discovered superconductor Cu0.07TiSe2. Consistent with the development from a semimetal or semiconductor with a very small indirect energy gap upon doping TiSe2, it is found that the compound has a low carrier density. Most remarkably, the study reveals a substantial shift of the screened plasma edge in reflectance towards high energy with decreasing temperature. This phenomenon, rarely seen in metals, indicates either a sizable increase of the conducting carrier concentration or/and a decrease of the effective mass of carriers with reducing temperature. We attribute the shift primarily to the latter effect.     

Origin of diastereoselectivity in the synthesis of chiral bicyclic lactams: pi-facial selective attack of singlet oxygen induced by hindered internal rotation

Previously reported experimental results indicate that photooxygenation of homochiral N-(hydroxyalkyl)-2-methylpyrroles with singlet oxygen yields trans-rather than cis-bicyclic lactams as the major product. In this study, the origin of selectivity in this reaction has been investigated with computational methods. Relative stabilities of homochiral N-(hydroxyalkyl)-2-methylpyrrole conformers and their effect on pi-facial selectivity of 1O2 were extensively studied. Stepwise and concerted reaction mechanisms, starting from the endoperoxide intermediates, were proposed and modeled in vacuum using the UB3LYP method with the 6-31+G** basis set. Solvent calculations were carried out in CH2Cl2, by means of the integral equation formalism-polarizable continuum model (IEF-PCM) at the UB3LYP/6-31+G** level of theory. Free energies of activation leading to both diastereomers were analyzed in an effort to explain the stereoselectivity and product distribution. Steric interactions among the pyrrole substituents were shown to lead to a rotational barrier higher than 10 kcal/mol. Hence, hindered internal rotation is suggested to cause one pyrrole conformer to be substantially overpopulated. This in turn has a major effect on pi-facial selectivity of 1O2, thereby favoring one endoperoxide over the other and leading to the diastereoselective synthesis of trans-pyrrolooxazolones. The importance of hindered internal rotors, for an accurate calculation of the frequency factors of a chemical reaction, has already been mentioned in the literature many times; however, in this work hindered internal rotors also seem to dictate the diastereoselective outcome of the reaction.