Elasticity and photoelasticity relationships for polyethylene terephthalate fiber networks by molecular simulation

We present a framework for the development of elasticity and photoelasticity relationships for polyethylene terephthalate fiber networks, incorporating aspects of the primary molecular structure. Semicrystalline polymeric fiber networks are modeled as sequentially arranged crystalline and amorphous regions. Rotational isomeric states-Monte Carlo simulations of amorphous chains of up to 360 bonds (degree of polymerization, DP=60), confined between and bridging infinite impenetrable crystalline walls, have been characterized by Omega, the probability density of the intercrystal separation h, and Deltabeta, the polarizability anisotropy. ln Omega and Deltabeta have been modeled as functions of h, yielding the chain deformation relationships. The development has been extended to the fiber network to yield the photoelasticity relationships. We execute our framework by fitting to experimental stress-elongation data and employing the single fitted parameter to directly predict the birefringence-elongation behavior, without any further fitting. Incorporating the effect of strain-induced crystallization into the framework makes it physically more meaningful and yields accurate predictions of the birefringence-elongation behavior.     

Kinetics,isotherm and thermodynamics for Cr(III) and Cr(VI) adsorption from aqueous solutions by crystalline hydrous titanium oxide

The synthetic crystalline hydrous titanium(IV) oxide (CHTO), an anatase variety and thermally stable up to 300 °C, has been used for adsorption of Cr(III) and Cr(VI) from the aqueous solutions, the optimum pH-values of which are 5.0 and 1.5, respectively. The kinetic data correspond very well to the pseudo-second order equation. The rates of adsorption are controlled by the film (boundary layer) diffusion, and increase with increasing temperature. The equilibrium data describe very well the Langmuir, Redlich–Peterson, and Toth isotherms. The monolayer adsorption capacities are high, and increased with increasing temperature. The evaluated ΔG^° (kJ · mol^?1) and ΔH^° (kJ · mol^?1) indicate the spontaneous and endothermic nature of the reactions. The adsorptions occur with increase in entropy (ΔS^° = positive), and the mean free energy (E_DR) values obtained by analysis of equilibrium data with Dubinin–Radushkevick equation indicate the ion-exchange mechanism for Cr(III) and Cr(VI)-adsorptions.     

Crystal and molecular structure of 2,2′-di-N-methylamino-1,1′ -di-p-hydroxyphenyldiethyleneether dihydrobromide, (C9H12ON·HBr)2O

The structure of the title compound (C₉H₁₂ON·HBr)₂O was determined by X-ray diffraction methods. The crystals are monoclinic:C2/c,a=7.645(2),b=19.777(3),c=13.704(3) Å,=98.32(2)°,V _c =2050.2 ų,Z=4,F(000)=968,D _m =1.62,D _c =1.615 Mg m^–3; MoK radiation (graphite crystal monochromator, =0.71073 Å),(MoK)=4.39 mm^–1. FinalR factor=0.061 andR _w =0.045 for 1566 reflections. The structure was solved by the heavy-atom Fourier method and refined by least-squares procedures. Each asymmetric unit in the unit cell contains one-half of the molecule, with oxygen atom O(2) at a special position with half-occupancy. The molecules are protonated at their nitrogen sites. The structure is stabilized by a three-dimensional network of hydrogen bonds. The ethylamine side chain in the molecular fragment in the asymmetric unit exhibits an extended (trans) conformation that is also found in most of the other adrenergic phenylethylamines.     

Crystal and molecular structure of chloramphenicol

Chloramphenicol, C₁₁H₁₂Cl₂N₂O₅, is orthorhombic, space groupC222₁,a = 17.495(3),b = 7.321(2),c = 22.130(4) Å, andZ = 8. The structure was solved by direct methods and refined to a finalR value of 0.068 for 1186 counter-reflections. Estimated standard deviations for bond lengths and bond angles involving nonhydrogen atoms average 0.009 Å and 0.6 °, respectively. All the hydrogen atoms that are bonded to O or N and are available for hydrogen-bond formation take part in the hydrogen-bonding network. The crystals become brown in color on prolonged exposure to X-rays and -rays. Our structural investigation with colored crystal does not indicate any structural change.     

Late-Stage Alkylation of Heterocycles Using N-(Acyloxy)phthalimides

Synthetic methods enabling late-stage modification of heterocycles hold tremendous importance in the pharmaceutical and agrochemical industry and drug discovery. Accordingly, efficient, functional group tolerant and selective late-stage alkylation of valuable molecular entities is of enormous significance and well-acknowledged in medicinal chemistry. Radical alkylation of heteroarenes employing carboxylic acids as the alkyl radical precursor represents one of the most direct ways of C−H functionalizations of heterocycles. Recently, the field has undergone a revolutionary development especially with regard to the generation of alkyl radicals under much milder conditions. In this regard N-(acyloxy)phthalimides (NHPI esters) have emerged as a suitable precursor of a diverse set of alkyl radicals allowing formal C−H alkylation of not only N-heteroarenes but a diverse set of non-aromatic heterocycles under visible light photocatalysis or electrochemical conditions. This review delineates all these discoveries and provides readers a comprehensive overview of this rapidly expanding field.     

Gamma Radiation Induced Biodegradable Shellac Films Treated by Acrylic Monomer and Ethylene Glycol

In this study the mechanical properties of shellac films, prepared by solution casting, were evaluated with varying amounts of Ethylene Glycol (EG) and 2-Ethyl-2-(hydroxymethyl)-1,3-propandiol-trimethacrylate (EHMPTMA). Mechanical properties such as tensile strength (TS) and elongation at break (Eb) of the raw shellac film were found to be 1.86 MPa and 4%, respectively. A series of formulations was prepared using shellac and varying percentages of EG and EHMPTMA in methanol. The films were prepared and irradiated under gamma (Co-60) radiation at different doses (50–500 krad). Grafting of EHMPTMA showed better results compared to raw shellac and EG treated films. Thermal properties, degradation tests in water and soil of the films were also evaluated.     

Quantum mechanics of rapidly and periodically driven systems

This review deals with the dynamics of quantum systems that are subject to high frequency external perturbations. Though the problem may look hopelessly time-dependent, and poised on the extreme opposite side of adiabaticity, there exists a ‘Kapitza Window’ over which the dynamics can be treated in terms of effective time-independent Hamiltonians. The consequent results are important in the context of atomic traps as well as quantum optic properties of atoms in intense and high-frequency electromagnetic fields.      

3-d Model for strain ordering in steel: I Static effects

We present a spring-defect model in 3-dimensions to describe the connection between elastic distortion and interstitial carbon ordering associated with phase transition from a body centred cubic (BCC) to body centered tetragonal (BCT) structure in BCC metals such as α-iron. The presence or the absence of the carbon is modelled in terms of a pseudo spinŝ=+1or -l.An Ising interaction between carbon atoms is recovered after eliminating the lattice degrees of freedom, which is longranged. The coupling between the spin and lattice degrees of freedom allows for a systematic study of ferroelasticity and the variation of the lattice parameter with carbon concentration. The mean field results for the paraelastic to ferroelastic transition, lattice parameter and static compliance are presented. The significant feature of this calculation is not only a derivation of the defect-defect interaction, but also an explicit calculation of the strain dipole tensor associated with each defect, from a microscopic model.     

Dissipative Diamagnetism—A Case Study for Equilibrium and Nonequilibrium Statistical Mechanics

Using the path integral approach to equilibrium statistical physics the effect of dissipation on Landau diamagnetism is calculated. The calculation clarifies the essential role of the boundary of the container in which the electrons move. Further, the derived result for diamagnetization also matches with the expression obtained from a time-dependent quantum Langevin equation in the asymptotic limit, provided a certain order is maintained in taking limits. This identification then unifies equilibrium and nonequilibrium statistical physics for a phenomenon like diamagnetism, which is inherently quantum and strongly dependent on boundary effects. In addition we have shown that our results are directly connected with fluctuation induced diamagnetic susceptibility of superconducting grains. PACS Number: 03.65.Yz, 05.20.-y, 05.20.Gg, 05.40.-a, 75.20.-g