级联二阶非线性法布里-珀罗谐振腔特性分析

在小信号近似下,得出了级联二阶过程的表达式。利用该式的有效三阶极化率的表达式,讨论了存在二阶非线性光学晶体的法－珀谐振腔的非线性光学特性。分析表明,由于谐振腔的存在,通过非线性晶体的功率密度超过入射功率密度几十倍以上,因而产生较大的、随相位失配变化的非线性相位漂移。当相位失配接近２π时,获得基叔光的最大相位漂移。该最大相位漂移对应的相位失配随着入射功率密度、非线性晶体的地阶极化率和晶体长度而变化。     

Rapid computer simulation of ESR spectra. Conventional ESR of axially symmetric 14N-nitroxide spin labels

A computer algorithm is presented for the simulation of the effect of molecular tumbling on ESR spectra, and is applied to simulation of the conventional ESR signal (the absorption signal detected at the first harmonic of the modulation frequency and in-phase with the modulation frequency, in the limit of low microwave and modulation power) of axially symmetric ¹⁴N-nitroxide spin labels. The algorithm is extremely fast and is economical in terms of computer memory requirements.     

Non planéité de cyclopenténones substituées analyse conformationnelle par résonance magnétique nucléaire

The stereochemistry of substituted cyclopent-2-en-1-ones was studied by NMR. The existence of non-planar rings is indicated and conformational analysis, based principally upon examination of the coupling constants enables the conformational population to be estimated; trans dihalogeno derivatives, for example, occur predominantly in the diaxial form.     

Crystal structure and magnetic structure of TbOOH

The monoclinic modification of terbium oxide hydroxide, TbOOH, was prepared using hydrothermal technique. The crystal structure was investigated by three-dimensional single-crystal X-ray analysis and was refined to a conventional R-value of 8.1%. The space group is $\text{P2}{}_1\text{m}$, No. 11, with a = 6.04 Å, b = 3.69 Å, c = 4.33 Å, and β = 109.0°. The terbium atom is seven coordinated with oxygen atoms, and the structure is not hydrogen bonded.The compound is antiferromagnetic with a Néel temperature of 10°K. Neutron diffraction powder patterns were measured at 300°K and 4.2°K. The magnetic super lattice reflections were indexed on the basis of a monoclinic unit cell with the dimensions a_M = 2a, b_M = b, c_M = c, and β_M = β, where a, b, c, and β are the dimensions of the chemical unit cell. The structure contains two independent magnetic atoms. A nonclinear antiferromagnetic arrangement of the spins describes the magnetic structure. The spin at one atom has an angle of 43° with the ac plane and the projection of the spin on the ac plane has an angle of 59° with the a axis. The spin on the other atom has an angle of ?43° with the ac plane, the projection having the same angle of 59° with the a axis.     

The Fe-N-C Nanozyme with Both Accelerated and Inhibited Biocatalytic Activities Capable of Accessing Drug–Drug Interactions

Emerging as a cost-effective and robust enzyme mimic, nanozymes have drawn increasing attention with broad applications ranging from cancer therapy to biosensing. Developing nanozymes with both accelerated and inhibited biocatalytic properties in a biological context is intriguing to peruse more advanced functions of natural enzymes, but remains challenging, because most nanozymes are lack of enzyme-like molecular structures. By re-visiting and engineering the well-known Fe-N-C electrocatalyst that has a heme-like Fe-N_x active sites, herein, it is reported that Fe-N-C could not only catalyze drug metabolization but also had inhibition behaviors similar to cytochrome P450 (CYP), endowing it a potential replacement of CYP for preliminary evaluation of massive potential chemicals, drug dosing guide, and outcome prediction. In addition, in contrast to electrocatalysts, the highly graphitic framework of Fe-N-C may not be obligatory for a competitive CYP-like activity.     

Sol-Gel Preparation and Raman Characterization of CdTiO3

Cadmium titanate (CdTiO₃) has been prepared by a room-temperature sol-gel technique. The powders were characterized by means of X-Ray Diffraction. Samples treated at 800°C give rise only to the ilmenite-like phase, but, after a treatment at 1100°C for about four hours, the orthorhombic perovskite is the only crystalline phase observed. The Raman spectrum of the perovskite phase is reported for the first time and that of the ilmenite phase is compared with the spectrum of CdTiO₃ bulk crystals. The effects of the starting stoichiometry on the purity of the final phases, relative to the presence of TiO₂ (anatase and rutile) or CdO, are investigated.