聚偏氟乙烯基含氟聚合物介电和储能研究进展

聚偏氟乙烯（PVDF）和偏氟乙烯（VDF）／三氟乙烯（TrFE）二元共聚物以其优异的铁电、压电性能而备受关注。近年来,该类聚合物经物理／化学改性后表现出非常优异的介电、储能性能,尤其在高储能放电电容器领域被寄予厚望。经分子组成优化和挤出拉伸处理的PVDF基含氟聚合物在室温下具有高介电常数（12～60）,高击穿电场强度,...     

Protonation sites and dissociation mechanisms of t-butylcarbamates in tandem mass spectrometric assays for newborn screening

Structures of tert-butylcarbamate ions in the gas-phase and methanol solution were studied for simple secondary and tertiary carbamates as well as for carbamate-containing products and internal standards for lysosomal enzyme assays used in newborn screening of a α-galactosidase A deficiency (Fabry disease), mucopolysaccharidosis I (Hurler disease), and mucopolysaccharidosis II (Hunter disease). The protonation of simple t-butylcarbamates can occur at the carbonyl group, which is the preferred site in the gas phase. Protonation in methanol solution is more favorable if occurring at the carbamate nitrogen atom. The protonation of more complex t-butylcarbamates occurs at amide and carbamate carbonyl groups, and the ions are stabilized by intramolecular hydrogen bonding, which is affected by solvation. Tertiary carbamates containing aminophenol amide groups were calculated to have substantially greater gas-phase basicities than secondary carbamates containing coumarin amide groups. The main diagnostically important ion dissociation by elimination of 2-methylpropene (isobutylene, i-C(4)H(8)) and carbon dioxide is shown by experiment and theory to proceed in two steps. Energy-resolved collision-induced dissociation of the Hurler's disease enzymatic product ion, which is a coumarin-diamine linker-t-butylcarbamate conjugate (3a(+)), indicated separate energy thresholds for the loss of i-C(4)H(8) and CO(2). Computational investigation of the potential energy surface along two presumed reaction pathways indicated kinetic preference for the migration of a t-butyl hydrogen atom to the carbamate carbonyl resulting in the isobutylene loss. The consequent loss of CO(2) required further proton migrations that had to overcome energy barriers.     

广义n-表现模

本文研究了模的投射维数与环的总体维数的计算问题.利用n-表现模的性质,得到了广义n-表现模的结构定理和右n-凝聚环的总体维数的计算方法,推广了已有的维数计算方法.     

模范畴Recollement的Koenig定理

Koenig定理描述了环的导出范畴允许recollement的一个充分必要条件.本文给出环的模范畴版本的Koenig定理及其应用.应用一是可以导出Morita等价定理,应用二是可以描述三角矩阵环与模范畴的recollement之间的密切联系.     

On ω-Linked Overrings

Let R (C) T be an extension of commutative rings. T is called ω-linked over R if T as an R-module is a ω-module. In the case of R (C) T (C) Q0(R), T is called a ω-linked overring of R. As a generalization of Wang-McCsland-Park-Chang Theorem, we show that if R is a reduced ring, then R is a ω-Noetherian ring with ω-dim(R) ≤1 if and only if each ω-linked overring T of R is a ω-Noetherian ring with ω-dim(T) ≤ 1. In particular, R is a ω-Noetherian ring with ω-dim(R) = 0 if and only if R is an Artinian ring.     

A new target for synthesis of sandwiched beryllium, magnesium, and calcium dimers: C5H7-M-M-C5H7 and C4H4P-M-M-C4H4P

Group 2 bis-element sandwiches formed by homoleptic open sandwiches with formula C₅H₇-M-M-C₅H₇ and C₄H₄P-M-M-C₄H₄P (M = Be, Mg, and Ca) have been studied at the B3LYP/cc-PVDZ and BP86/6-311G(d,p) levels of theory. The predicted M-M bond distances are much shorter than in the equivalent isolated M-M dimer and indicate substantial Be-Be, Mg-Mg, and Ca-Ca bonding. An NBO analysis shows that each M-M unit contains a single covalent bond and that the unit is linked to the open pentadienyl and phospholyl ring via ionic bonds. We thus predict that these new compounds are viable synthetic targets.