Measurement of the hyperfine splitting of the 9 S1/2 level in Cesium by Doppler-free two-photon spectroscopy

The hyperfine splitting for the ¹³³Cs isotope for the 6s ²S_1/2 → 9s ²S_1/2 transition has been measured using Doppler-free two-photon fluorescence spectroscopy in a gas cell for the first time to our knowledge. The hyperfine splitting between the two components was measured to be 8754 (1) MHz and the magnetic dipole coupling constant (A) for the excited 9s ²S_1/2 level was determined to be 109.7 (3) MHz for the ¹³³Cs isotope. The measured values are in good agreement with the earlier reported results.     

Significance of Mg doped LiMn2O4 spinels as attractive 4 V cathode materials for use in lithium batteries

LiMn₂O₄ spinel is one of the most promising cathode materials for lithium-ion batteries because of its cheapness and eco-friendliness. Due to Jahn-Teller distortion, the capacity fades, however, upon repeated cycling. Attempts are being made to improve the cycle life of the spinel by substitution of manganese with other cations. In this paper we report the effect of partial substitution of manganese by Mg²⁺ ions in the LiMn₂O₄ phase. LiMg_yMn_2−yO₄ (y=0 – 0.3) has been synthesized by a thermal method and characterized using XRD, TG/DTA and FTIR. The electrochemical performance is correlated with the dopant concentration.     

On the Proportional Odds Model in Survival Analysis

The proportional odds (PO) model with its property of convergent hazard functions is of considerable value in modeling survival data with non-proportional hazards. This paper explores the structure, implications, and properties of the PO model. Results proved include connections with geometric minima and maxima, ageing characteristics, and bounds on mean and variance of survival times.     

Quantification of pentaerythritol tetrastearate,a mold release agent used in polycarbonate,by non‐aqueous RP HPLC method

A new non‐aqueous high‐performance liquid chromatography method for the quantitative determination of mold release agent pentaerythritol tetrastearate in polycarbonate matrix has been developed and validated. The analyte calibration curve was linear over range of 0.05–0.2 mg/mL (Coefficient of determination > 0.999), with limit of detection of 0.03 mg/mL. The repeatability of method was satisfactory with relative standard deviation of 1.6%. The obtained recovery was ranging from 100–101%. Detailed high‐resolution mass spectrometric characterization of the principle peak confirmed that all the five components of pentaerythritol tetrastearate elutes as a single peak under the established chromatographic conditions. The new method is reliable and independent of any variation in composition of analyte in the samples compared to pentaerythritol tetrastearate reference standard used for calibration. The new high‐performance liquid chromatography method is robust and easy to implement in quality control laboratories for quantitative estimation of the mold release agent added in commercial polymer.     

Bio-Marangoni convection flow of Casson nanoliquid through a porous medium in the presence of chemically reactive activation energy

Applied Mathematics and Mechanics - Bioconvection research is primarily focused on the augmentation of energy and mass species, which has implications in the processes intensification, mechanical,...     

SO4−2/SnO2–catalyzed cyclocondensation for the synthesis of fully functionalized pyridines

An efficient and promising synthetic approach to assemble skeletons of multifunctionalized pyridine derivatives in presence of recyclable heterogeneous sulfated tin oxide (STO) catalyst has been evolved. The STO catalyst was used as a promoter for the cyclocondensation process in ethanol at 70°C. Overall performance of this catalyst was attributed to the cooperative contribution of its Lewis and Brønsted-Lowry acidic sites. Nanosized STO catalyst was synthesized by using sol-gel process and characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), ¹H-NMR, and scanning electron microscopy (SEM). This catalyst tolerates most of the substrates, and protocol shows precious capabilities consist of high yields, operational simplicity, less reaction time, and eco-friendly conditions. The newly synthesized heterogeneous catalyst was easily separated and reused. All the reactions are carried out for subsequent cycles without significant loss of catalytic activity and with good proficiency.     

Emulsification of Vegetable Oils using a Blend of Nonionic Surfactants for Cosmetic Applications

Sunflower oil and sesame oil contain fairly high percentage of tocopherols and tocotrienols. These oils were emulsified by using a combination of non‐ionic surface‐active agents viz. Span‐80 and Tween‐20 surfactants to get cosmetic emulsions. Stability of the emulsions was enhanced by using natural polymer additives. The effect of various parameters such as pH, oil content, emulsifier content, HLB of blend of emulsifier concentration of additives and temperature on the stability of cosmetic emulsion was studied. These emulsions are “skin compatible” being stable at neutral pH. Xanthan gum was found to be the most effective additive as compared to the other natural polymers. The emulsions showed a “pseudoplastic” flow behavior.     

Total synthesis of gabosines via an iron-catalyzed intramolecular tandem aldol process

Several gabosines, belonging to polyhydroxy-cyclohexenone and cyclohexanone class of natural products, are synthesized in various stereoforms using an intramolecular iron-catalyzed tandem aldol process. The reaction, which starts from vinylic pyranoses, is compatible with two different OH protecting groups (acetyl and benzyl). Further, like the Ferrier carbocyclisation, it is not sensitive to the stereochemistry of sugar molecules used as precursors: six different gabosine-type molecules have been prepared by this route starting from d-Glucose, d-Mannose, and d-Galactose derivatives.