Ca and Mg determination from inhabitants of Brazil using neutron activation analysis

In this study the neutron activation analysis (NAA) technique was applied to determine Ca and Mg in whole blood from inhabitants of Brazil for the purpose of establishing concentration ranges indicative of sex and age. The initiative to perform these measurements is related to the increase in heart disease. According to recent statistics from WHO, the average is one death due to heart attack in Brazil, every five minutes. The measures were performed considering lifestyle factors (non-smokers, non-drinkers and no history of toxicological exposure) of Brazilian inhabitants. A healthy group constituted of male (n = 94) and female (n = 84) blood donors, ages between 18 and 70 years and above 50 kg, was selected from the blood banks and hematological laboratories of Brazil. The influence of sex was also investigated considering several age ranges (18–29, 30–40, 41–50, >50 years). The results show significant differences when a comparison is made by sex and age and may be useful to identify or prevent clinical diseases. These results emphasize the need to perform periodic evaluation of Ca and Mg in blood.     

Geographical influences of an emerging network of gang rivalries

We propose an agent-based model to simulate the creation of street gang rivalries. The movement dynamics of agents are coupled to an evolving network of gang rivalries, which is determined by previous interactions among agents in the system. Basic gang data, geographic information, and behavioral dynamics suggested by the criminology literature are integrated into the model. The major highways, rivers, and the locations of gangs’ centers of activity influence the agents’ motion. We use a policing division of the Los Angeles Police Department as a case study to test our model. We apply common metrics from graph theory to analyze our model, comparing networks produced by our simulations and an instance of a Geographical Threshold Graph to the existing network from the criminology literature.     

A combined crossed molecular beam and quasiclassical trajectory study of the Titan-relevant N(2D) + D2O reaction

Following a recent investigation on the N(²D) + H₂O reaction [Homayoon et al., J. Phys. Chem. Lett. 5, 3508 (2014)], we report on an experimental and theoretical study of the isotopologue N(²D) + D₂O reaction. Crossed molecular beam (CMB) experiments were conducted at a collision energy of 10.3 kcal mol^–1. Quasiclassical trajectory calculations were performed on a recent potential energy surface to derive the centre-of-mass functions necessary to simulate the CMB laboratory distributions. Excellent agreement was found. The importance of the channel leading to HON/DON was confirmed. The inclusion of this channel, in addition to that leading to the isomer HNO/DNO, can affect the models considering the coupling between nitrogen and oxygen chemistry in the upper atmosphere of Titan.     

Synthesis and Characterization of Triphenylphosphine Oxide-Containing Poly(Aryl Imide)-Poly(Dimethyl Siloxane) Randomly Segmented Copolymers

Abstract

Poly(aryl imide)-poly(dimethyl siloxane) randomly segmented copolymers were synthesized by essentially a one-step solution imidization process in a solvent system consisting of predominately o-dichlorobenzene with a small amount of n-methylpyrolidone. This solvent combination was selected because of its ability to afford homogeneous solutions throughout the polymerization process. This enabled copolymers of any desired poly(dimethyl siloxane) composition to be prepared. A hydrolytically stable triphenylphosphine oxide containing diamine, bis(3-amino-phenoxy-4′-phenyl)phenylphosphine oxide, was utilized as a chain extender and together with oxydiphthalic anhydride formed the hard segment in these copolymers. The soft segment was formed from α,ω-aminopropyl poly(dimethyl siloxane) oligomers of controlled molecular weight. The presence of phosphorus and silicon contributes several unique properties to the system, including enhanced solubility, thermal stability, and flame resistance. High molecular weight copolymers containing up to 60% (w/w) of the poly(dimethyl siloxane) segments were successfully prepared using this method. Gel permeation chromatography analysis, based on a universal calibration curve in CHCl₃, was performed to determine the molecular weights and distribution. These copolymers with 40-60% (w/w) poly(dimethyl siloxane) exhibited upper T_g values ranging from 130 to 180°C and showed substantial char yields at 750°C in air, which increased with siloxane content. Dynamic mechanical analysis confirmed the anticipated microphase behavior by the presence of two separate glass-transition regions. Both small angle x-ray scattering and transmission electron microscopy measurements determined on well-characterized transparent cast films were used to better demonstrate the multiphase nature of these copolymers.