Polarized x-ray emission from magnetized neutron stars: signature of strong-field vacuum polarization

In the atmospheric plasma of a strongly magnetized neutron star, vacuum polarization can induce a Mikheyev-Smirnov-Wolfenstein type resonance across which an x-ray photon may (depending on its energy) convert from one mode into the other, with significant changes in opacities and polarizations. We show that this vacuum resonance effect gives rise to a unique energy-dependent polarization signature in the surface emission from neutron stars. The detection of polarized x rays from neutron stars can provide a direct probe of strong-field quantum electrodynamics and constrain the neutron star magnetic field and geometry.     

Electrochemical Synthesis of Benzazoles from Alcohols and o‐Substituted Anilines with a Catalytic Amount of CoII Salt

An electrochemical synthesis of benzazoles directly from alcohols and o‐substituted anilines has been developed. The reaction conditions have been optimized by varying the composition of the electrolyte and the metal salt used as catalyst. The cyclization proceeds smoothly with a catalytic amount of a cobalt salt under air at room temperature to afford 2‐substituted benzimidazoles, benzothiazoles, and benzoxazoles in good to excellent yields with a wide substrate scope.     

Triggering Gel Formation and Luminescence through Donor–Acceptor Interactions in a C3‐Symmetric Tris(pyrene) System

Straightforward modulation of the gelation, absorption and luminescent properties of a tris(pyrene) organogelator containing a C₃‐symmetric benzene‐1,3,5‐tricarboxamide central unit functionalized by three 3,3′‐diamino‐2,2′‐bipyridine fragments is achieved through donor–acceptor interactions in the presence of tetracyanoquinodimethane.     

Incarceration of Higher‐Order Fullerenes within Cyclotriveratrylene‐Based Hemicarcerands Allows Selective Isolation of C76, C78, and C84 from a Commercial Fullerene Mixture

Size‐complementary cyclotriveratrylene (CTV)‐based hosts can incarcerate C₇₆, C₇₈, and C₈₄, thus allowing the selective isolation of these higher‐order fullerenes from a commercially available mixture of fullerenes. The hemicarceplexes, formed after the encapsulation of the size‐complementary fullerenes within the hosts, are isolated by column chromatography and released at elevated temperature, thereby leading to the isolation of C₇₆/C₇₈ and C₈₄ in good purities (up to 95 and 88 %, respectively).     

Three new monoterpene glucosides from Sibiraea angustata

Three new monoterpene glycosides, named sibiraglycoside I(1), J(2) and K(3), were isolated from an aqueous extract of the aerial portion of Sibiraea angustata. Their structures were elucidated on the basis of extensive spectroscopic data analysis (including 1D and 2D NMR and MS experiments) and compared to literature data.     

大学物理课程中“高等数学基础”教学——以应用为导向

本文给出了为大学物理课程学习做准备的数学基础的教学中的3个应用性原则,指出教学重点应放在让学生理解微分与导数、积分以及矢量运算几个方面的思想与方法,特别要让学生理解:微分表示变量的微小变化;导数在几何上表示函数曲线上切线的斜率,而且导数中分子和分母两个微分是既相关联又可以分开的量;积分的本质意义是求和,把物理问题转化为积分问题通常包括两个过程,一是积分区域无限细分,其目的在于化变为不变;二是无限求和.通过不定积分与定积分的关系可以帮助学生快速计算一些简单被积函数的积分.讲述积分的过程中,可以引入微分方程的概念及分离变量法求解的思想.矢量运算中的难点是标量积与矢量积的区别以及矢量求导.前者可通过力做功及力矩的概念帮助学生加深理解.而矢量求导可以结合曲线运动中的速度、加速度的计算让学生理解其思想与方法.