数字功率发展趋势

最近的行业趋势显示,用于功率转换和功率管理的数字控制日趋成熟,数字功率带来了大量新的设计可能性。例如,在功率管理领域,数字电源支持串行总线通信、电源的远程监控和排序、软件升级,以及老化参数的补偿等等所有新特性,而不仅仅是常规功能。针对功率转换,数字功率能够实现数     

Single-crystal-like materials by the self-assembly of cube-shaped lead zirconate titanate (PZT) microcrystals

We demonstrated the formation of single-crystal-like materials that contain preferentially oriented arrays of lead zirconate titanate (PZT) cube-shaped particles by self-assembly. Hydrothermally synthesized PZT particles with a bulk composition of Zr/Ti = 70/30 were used in making microcrystal arrays. Spreading a suspension containing PZT cube-shaped particles, 2-propanol, and mineral oil at the air-water interface produced a one-dimensional planar array of PZT particles on the water surface. The array so formed was subsequently transferred onto a flat or curved substrate. X-ray diffraction and electron backscattered diffraction analyses revealed that most of the cube-shaped particles in the array were oriented with their pseudocubic (001) direction aligned parallel to the normal direction of the substrate surface. Filling the arrays with matrixes produced monolayer or multilayer textured composites. The piezoelectric properties of oriented cube-shaped micron-sized particles in the self-assembled arrays were measured using a modified atomic force microscope to reveal the ferroelectric nature of the PZT arrays.     

Vibrational spectra of bridging carbonyl groups in transition metal carbonyl clusters

The spherical harmonic model (SHM), previously used for the analysis of the terminal nu(CO) vibrations of transition metal carbonyl clusters, is applied to the corresponding bridging CO modes. The model is applicable, although the spectra show a greater sensitivity to the molecular geometry than is the case for their terminal counterparts. The reasons for this sensitivity are discussed. When both micro(2) and micro(3) CO groups are present in a molecule, a spectral distinction may not be apparent.     

Voltammetric determination of N-nitrosamines in the hypoglycemic agent tolazamide

Summary Exposure to N-nitrosamines has been indicted as one cause of cancer and so their presence has to be controlled. Voltammetry has been used for the detection of N-nitrosamines and has the advantage that it can be applied to both volatile and non-volatile compounds.The proposed method consists in dissolving 50 mg of tolazamide drug in 1 M potassium hydroxide and, after deaeration, the solution is directly submitted to differential pulse polarography. The response at about —1.50 V (vs. Ag/AgCl reference electrode) is proportional to the N-nitrosamine content from 0.5 ppm to more than 1,000 ppm into the tolazamide sample, with a relative standard deviation of ± 3 – 4% at 1 ppm. The sensitivity of the proposed method is essentially limited by a sharp peak due to N-[(hexahydro-1H-azepin)carbonyl]-4-methylbenzensulphonamide (usually present as impurity in tolazamide), that occurs at about –1.23 V (vs. Ag/AgCl reference electrode).

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Voltammetrische Bestimmung von N-Nitrosaminen in dem hypoglykämischen Mittel Tolazamid

     

$${\mathbb{Z}}_2^k$$ -Manifolds are isospectral on forms

We obtain a simple formula for the multiplicity of eigenvalues of the Hodge-Laplace operator, Δ _f , acting on sections of the full exterior bundle over an arbitrary compact flat Riemannian n-manifold M with holonomy group , 1 ≤ k ≤ n − 1. This formula implies that any two such manifolds having isospectral lattices of translations are isospectral with respect to Δ _f . As a consequence, we construct a large family of pairwise Δ _f -isospectral and nonhomeomorphic n-manifolds of cardinality greater than . Supported by Conicet, Secyt-UNC.     

Evaluation of 3- and 4-Phenoxybenzamides as Selective Inhibitors of the Mono-ADP-Ribosyltransferase PARP10

Intracellular ADP-ribosyltransferases catalyze mono- and poly-ADP-ribosylation and affect a broad range of biological processes. The mono-ADP-ribosyltransferase PARP10 is involved in signaling and DNA repair. Previous studies identified OUL35 as a selective, cell permeable inhibitor of PARP10. We have further explored the chemical space of OUL35 by synthesizing and investigating structurally related analogs. Key synthetic steps were metal-catalyzed cross-couplings and functional group modifications. We identified 4-(4-cyanophenoxy)benzamide and 3-(4-carbamoylphenoxy)benzamide as PARP10 inhibitors with distinct selectivities. Both compounds were cell permeable and interfered with PARP10 toxicity. Moreover, both revealed some inhibition of PARP2 but not PARP1, unlike clinically used PARP inhibitors, which typically inhibit both enzymes. Using crystallography and molecular modeling the binding of the compounds to different ADP-ribosyltransferases was explored regarding selectivity. Together, these studies define additional compounds that interfere with PARP10 function and thus expand our repertoire of inhibitors to further optimize selectivity and potency.     

A photocatalytic water splitting device for separate hydrogen and oxygen evolution

A two-compartment Plexiglas cell has been set up and tested for separate hydrogen and oxygen production from photocatalytic water splitting on a thin TiO2 layer deposited by magnetron sputtering on a flat Ti electrode inserted between the two cell compartments.