The surface-assisted alignment of a nematic liquid crystal yields a persistent ordered structure upon cationic photopolymerization of liquid-crystalline epoxides. Linearly polarized light irradiation of a photocrosslinkable polymer containing azobenzene moieties played a crucial role in this procedure since the photoinduced alignment is not deteriorated by heating for polymerization. 相似文献
The title compound was synthesized and structurally characterized. Theoretical IR, NMR (with the GIAO technique), UV, and nonlinear optical properties (NLO) in four different solvents were calculated for the compound. The calculated HOMO–LUMO energies using time-dependent (TD) DFT revealed that charge transfer occurs within the molecule, and probable transitions in the four solvents were identified. The in silico absorption, distribution, metabolism, and excretion (ADME) analysis was performed in order to determine some physicochemical, lipophilicity, water solubility, pharmacokinetics, drug-likeness, and medicinal properties of the molecule. Finally, molecular docking calculation was performed, and the results were evaluated in detail. 相似文献
Magnetic resonance imaging (MRI) was performed in 22 patients at various times (0-3) years) following radiation therapy to the spine. T1 and T2 weighted images were obtained at 0.5 Tesla. Increased signal was seen after 800-6000 rads (8-60 Gy). Marrow effects corresponded to radiation ports. Recurrent tumor was clearly separated from fatty replacement. This was much better seen on T1 weighted images. Five patients that had MRI during their course of radiotherapy (XRT) did not have increased signal on T1 images of the bone marrow. The earliest fatty marrow change was seen nine days following completion of 3000 rads (30 Gy) XRT over one month's duration. One patient who received 800 rads (8 Gy) to the upper thoracic spine for eosinophilic granuloma had no radiation effects on MRI when imaged 16 days following completion of XRT given over five days. Fatty marrow change was seen in this patient on MRI six months later. MRI was particularly useful in defining the extent of prior radiation effects when repeat therapy was needed. 相似文献
A sequence of coefficients that appeared in the evaluation of a rational integral has been shown to be unimodal. The original proof is based on a inequality for hypergeometric functions. A generalization is presented. 相似文献
This article presents a branch-and-bound algorithm for globally solving the nonlinear sum of ratios problem (P). The algorithm economizes the required computations by conducting the branch-and-bound search in p, rather than in n, where p is the number of ratios in the objective function of problem (P) and n is the number of decision variables in problem (P). To implement the algorithm, the main computations involve solving a sequence of convex programming problems for which standard algorithms are available. 相似文献
The purity P of laboratory chemicals is often declared in the form P > or = xy% (e.g., P > or = 97%). With a randomly chosen set of 40 compounds we found that their purity is generally closer to 100% than to the lower limit. The distribution of the purity data as found in the laboratory depends on the analytical technique used. Whereas purities determined by chromatography do not exceed 100% (because the sum of all observed peak areas is set to 100%), the purities obtained by titration can exceed 100% (because the functionality of the compound is measured). Therefore, the data for these two groups need to be dealt with in different ways. For purities based on titration we propose to use a rectangular distribution with a range from Pmin to 101%, an expected purity value which is the mean and a standard uncertainty of the purity u(P) of 29% of the range. Purities determined by chromatography can be described with a triangular distribution (ramp function). One leg of the triangle represents the range from Pmin to 100% and the right-angle is located at 100%. The expected value is the median and the uncertainty u(P) is 24% of the range. These proposals match the experimental data well. 相似文献
Observations are reported of the effect of the buffer gases He, Ne, and CF4, in the pressure range of 0–30 torr, on the branching ratio [HCl]/[DCl] of the unimolecular decomposition The ratio R = kH/kD has been measured in high-pressure thermal decomposition (670–1100 K) and was shown to give a unique measure of the internal energy of the decomposing molecules and hence, with RRKM theory and pressure fall-off data, a time scale for their decomposition. Applying the thermal data to the photolysis leads to the conclusion that excitation and decomposition are produced by the laser spike (high intensity, 70 ns FWHM) and also at a slower rate by the larger, less intense tail (1.6 μs). Added buffer gases quench the latter, leaving the former which, from measurements of R, is shown to correspond to excitations of 115 ± 15 kcal/mol and lifetimes of ~30 ps. No bond breaking is seen despite the high energies, in accord with theoretical expectations. The results require an enhanced rate of photon absorption by the highly excited molecules, which are about hundredfold greater than that observed for 300 K molecules. Data are also reported for C2H2F2 and the secondary multiphoton photolysis of the ethylenes produced. Effects of beam geometry and wavelength are explored. 相似文献
The rate of the reaction CH2I2 + HI ? CH3I + I2 has been followed spectrophotometrically from 201.0 to 311.2°. The rate constant for the reaction fits the equation, log (k1/M?1 sec?1) = 11.45 ± 0.18 - (15.11 ± 0.44)/θ. This value, combined with the assumption that E2 = 0 ± 1 kcal/mole, leads to ΔH (CH2I, g) = 55.0 ± 1.6 kcal/mole and DH (H? CH2I) = 103.8 ± 1.6 kcal/mole. The kinetics of the disproportionation, 2 CH3I ? CH4 + CH2I2 were studied at 331° and are compatible with the above values. 相似文献