Molecular Dynamics of Neutral Polymer Bonding Agent (NPBA) as Revealed by Solid-State NMR Spectroscopy

Neutral polymer bonding agent (NPBA) is one of the most promising polymeric materials, widely used in nitrate ester plasticized polyether (NEPE) propellant as bonding agent. The structure and dynamics of NPBA under different conditions of temperatures and sample processing are comprehensively investigated by solid state NMR (SSNMR). The results indicate that both the main chain and side chain of NPBA are quite rigid below its glass transition temperature (Tg). In contrast, above the Tg, the main chain remains relatively immobilized, while the side chains become highly flexible, which presumably weakens the interaction between bonding agent and the binder or oxidant fillers and in turn destabilizes the high modulus layer formed around the oxidant fillers. In addition, no obvious variation is found for the microstructure of NPBA upon aging treatment or soaking with acetone. These experimental results provide useful insights for understanding the structural properties of NPBA and its interaction with other constituents of solid composite propellants under different processing and working conditions.National Natural Science Foundation (China) (21120102038)National Natural Science Foundation (China) (21373265)National Natural Science Foundation (China) (21003154

The OpenMolcas Web: A Community-Driven Approach to Advancing Computational Chemistry

The developments of the open-source OpenMolcas chemistry software environment since spring 2020 are described, with a focus on novel functionalities accessible in the stable branch of the package or via interfaces with other packages. These developments span a wide range of topics in computational chemistry and are presented in thematic sections: electronic structure theory, electronic spectroscopy simulations, analytic gradients and molecular structure optimizations, ab initio molecular dynamics, and other new features. This report offers an overview of the chemical phenomena and processes OpenMolcas can address, while showing that OpenMolcas is an attractive platform for state-of-the-art atomistic computer simulations

Optimization of Indirect Photometric Detection of Anions in High-Performance Capillary Electrophoresis

Optimization of the indirect photometric detection in high-performance capillary electrophoresis is demonstrated. The influences of background electrolyte (BGE) concentration, capillary diameters, linear polymers, pH of BGE and types of BGE have been studied and assessed in terms of theoretical predictions. The experimental results fit the theoretical deduction very well. At optimized conditions, sub-femtomoles of simple anions can be detected, offering a 500-fold improvement compared to previous studies, and being close to the predicted limit of detection

Gender bukan tabu: catatan perjalanan fasilitasi kelompok perempuan di Jambi

Cross-coupling of nitrogen with hydrocarbons under fragment coupling conditions stands to significantly impact chemical synthesis. Herein, we disclose a C­(sp³)–N fragment coupling reaction between terminal olefins and <i>N</i>-triflyl protected aliphatic and aromatic amines via Pd­(II)/SOX (sulfoxide-oxazoline) catalyzed intermolecular allylic C–H amination. A range of (56) allylic amines are furnished in good yields (avg. 75%) and excellent regio- and stereoselectivity (avg. >20:1 linear:branched, >20:1 <i>E</i>:<i>Z</i>). Mechanistic studies reveal that the SOX ligand framework is effective at promoting functionalization by supporting cationic π-allyl Pd

Determination of Total Polyamines in Tumor Cells by High-Performance Capillary Zone Electrophoresis with Indirect Photometric Detection

Tumor cells contain much higher levels of common poly amines such as putrescine, spermidine, and spermine than normal cells. Our previous work demonstrated that high-performance capillary zone electrophoresis with Indirect photometric detection was suitable for the determination of underlvatized free polyamines in tumor cells. We now report Improved sensitivity (7-fold), greater quantitative reproducibility, and quantitation of both bound and free, underlvatized polyamines in PC 12 tumor cells. 1,7-Diaminoheptane was used as an internal standard for quantification. Femtomoles of three polyamines and simple cations such as K+ and Na+ were easily separated in less than 10 min. The quantitations for total spermidine and spermine (bound and free) were found to be 2-fold higher than the quantitation for free, unbound polyamines using our previous method. The signal response was linear over 2 orders of magnitude. The method described here provides a fast and simple technique for quantitation of bound, unbound, and total polyamines for use in the study of the biological role of polyamines

Simultaneous Detection and Quantitation of Sodium, Potassium, Calcium and Magnesium in Ocular Lenses by High-Performance Capillary Electrophoresis with Indirect Photometric Detection

A high-performance capillary electrophoresis (HPCE) method which can be used to quantitatively determine Na+, K+, Ca2+ and Mg2+ simultaneously in ocular lenses has been developed. The proteins in the lens aqueous homogenates were precipitated by 10% trichloroacetic acid. The precipitated proteins were removed after a brief centrifugation, and the supernatant containing the cations was washed with ether and directly used for HPCE analysis. A 50 µm x 75 cm fused-silica capillary was used for separation and the detection wavelength was set at 214 nm. A 20-mM imidazole at pH 6.0 containing 0.1% hydroxypropyl methyl cellulose was used as background electrolyte. Sample solution was injected at 15 kV for 10 s, and the electrophoresis was carried out at 15 kV. All the cations can be separated and quantified from the peak areas within 9 min. The values obtained by this method were comparable with commonly used flame atomic absorption and flame atomic emission spectroscopy. It is demonstrated that this HPCE method can be used to quantify all the cation levels simultaneously within a short time even in a small single rat or mice lens

Indirect Photometric Detection of Polyamines in Biological Samples Separated by High-Performance Capillary Eletrophoresis

A rapid separation of polyamines and some related amino acids in cultured tumor cells by high-performance capillary zone electrophoresis with indirect photometric detection is demonstrated. 60 cm x 75 µm I.D. fused-silica capillary was used for the separation and quinine sulfate was used as a background electrolyte (BGE). Several polyamines (putrescine, spermidine and spermine), amino acids (lysine, arginine, histidine) and simple cations (K+, Na+) were easily separated in less than 10 min. Using the indirect photometric detection method, femtomole amounts of polyamines extracted from the tumor cells were detected from nanoliter injection volumes, and the signal response was linear over two orders of magnitude

Research on light weight of thin-walled beam for automobile body

The developing trend of the light-weight car is the using of new light-weight materials and the optimization of the car body structure. The beam construction is the major bearing part of the car body. The thin–walled beam of the light-material plays a significant role in lightening the car' own weight, saving the materials, reducing fuel consumption and air pollution. Firstly, the relationship between the thin-walled beam that is fixed in both points and the attribute of the material can be infered from the stiffness coefficient which used as the quantitative index to estimate materials. Then take the body-in-white produced by domestic car factory as an object of study, and use Cu or Al or Mg as the materials of the thin-walled beam to calculate the bending rigidity and torsional stiffness of thewhole car body by using the FEM simulation conducted in HyperMesh.The results show that under the condition of bending and torsion, the SME value is lower when the lighten materials such as Al or Cu are used as the bodywork of the thin-walled beam than steel is. Lighten material can greatly reduce the weight of the vehicle. But it also decreased the bending and torsional stiffness of the bodywork. Therefore, in order to avoid decreasing mechanical properties which caused by adopting lighten materials, we must consider the structural design of the thin-walled beam when adopt material for lightweight