Time-dependent concentration depolarization: A Monte Carlo study

The phenomenon of time-dependent concentration depolarization is examined by a Monte Carlo procedure. The method described is general and versatile, and allows one to arbitrarily choose absorption and emission molecular polarizations, energy transfer mechanisms, and radial and orientational distribution functions. Comparison is made with recent theoretical results on time-dependent depolarization, and with experimental results on the “steady-state” depolarization of the phosphorescence of phenanthrene-d₁₀. Good agreement is obtained for a wide range of concentrations.     

Study of structural and electronic transport properties of Ce-doped LaMnO3

The structural and electronic transport properties of La_1−x Ce _x MnO₃ (x=0.0–1.0) have been studied. All the samples exhibit orthorhombic crystal symmetry and the unit cell volume decreases with Ce doping. They also make a metal-insulator transition (MIT) and transition temperature increases with increase in Ce concentration up to 50% doping. The system La_0.5Ce_0.5MnO₃ also exhibits MIT instead of charge-ordered state as observed in the hole doped systems of the same composition.     

On regularization in parameter-free shape optimization

This contribution is concerned with a parameter-free approach to computational shape optimization of mechanically-loaded structures. Thereby the term ’parameter-free’ refers to approaches in shape optimization in which the design variables are not derived from an existing CAD-parametrization of the model geometry but rather from its finite element discretization. One of the major challenges in using this type of approach is the avoidance of oscillating boundaries in the optimal design trials. This difficulty is mainly attributed to a lack of smoothness of the objective sensitivities and the relatively high number of design variables within the parameter-free regime. To compensate for these deficiencies, Azegami introduced the concept of the so-called traction method, in which the actual design update is deduced from the deformation of a fictitious continuum that is loaded in proportion to the negative shape gradient. We investigate a discrete variant of the traction method, in which the design sensitivities are computed with respect to variations of the design nodes for a given finite element mesh rather than on the abstract level by means of the speed method. Moreover, the design update process is accompanied by adaptive mesh refinement based on discrete material residual forces. Therein, we consider radaptive node relocation as well as hadaptive mesh refinement. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

The addition of phenylsulfenyl chloride to 5-methylene-2-norbornene synthesis of tricyclo-eka-santalol

Phenylsulfenyl chloride adds to 5-methylene-2-norbornene to give 1-chloromethyl-3-nortricyclyl phenyl sulfide in good yield. This reaction is used in a tricyclo-eka-santalol synthesis.     

First diastereoselective formation of lanthanide triple helical complexes with a terdentate chiral C2 symmetric ligand

Steric interactions between three enantiopure terdentate ligands leads to the diastereoselective formation of luminescent triple helical lanthanide complexes.     

On the magnetic field dependence of nuclear spin relaxation (NRS) on surfaces

We have measured the nuclear spin relaxation rate for nuclear spin polarized⁷Li atoms adsorbed on a hot O-W(110) surface and found that it increases as the magnetic field strength approaches zero. The trend of the nuclear spin relaxation rate generally agrees with a logarithmic divergence, a consequence of the correlation function for two-dimensional diffusion. In principle, such experiments yield information on absolute values of diffusion rates for the adsorbed atoms. Supported in part by a Travel Grant from the North Atlantic Treaty Organization.     

Pressure and temperature dependence of the static dielectric constant of KBr

The static dielectric constant and the temperature and pressure derivatives of the static dielectric constant of KBr have been measured at several temperatures between 4·3°K and room temperature. The sample was prepared in the form of a three-terminal parallel-plate capacitor and the dielectric constant was determined from measurements of the capacitance with a high precision bridge. The dielectric constant decreases with temperature as does the magnitude of the temperature dependence and the magnitude of the pressure dependence. The data were used to calculate the fixed-volume temperature derivative of the dielectric constant. This quantity, (? ln ε/?T)_v, exhibiting lattice-anharmonicity effects, decreases slightly from its room temperature value as the temperature is lowered, rises to a maximum value at about 33°K and then decreases rapidly at lower temperatures.     

Synthesis with benzenesulfenyl chloride. On the structure of a C12H18 hydrocarbon from East Indian sandalwood oil

The tetracyclic hydrocarbon $\text{1}$ was synthesized by means of the electrophilic addition of benzenesulfenyl chloride to an appropriately substituted methylenenorbornene $\text{7}$. The synthetic methodology used to prepare this letter compound includes a mild enol ether hydrolysis with acidic silica gel.