Low Mach limit to one-dimensional nonisentropic planar compressible magnetohydrodynamic equations

This paper is concerned with a one-dimensional nonisentropic compressible planar magnetohydrodynamic flow with general initial data, whose behaviors at far fields x→±∞ are different. The low Mach limit for the system is rigorously justified. The limit relies on the uniform estimates including weighted time derivatives and an extended convergence lemma.     

IDose^4迭代重建技术应用于低剂量CT肾动脉血管造影的临床分析

为探讨IDose 4迭代重建技术在低剂量CT肾动脉血管造影中的应用价值,选取205例拟行肾动脉CT血管造影患者,随机将其分为4组,A组(51例)采用管电压100 kV、管电流100 mA,碘海醇370 mg I/mL及IDose 4迭代重建技术,B组(51例)采用管电压100 kV、管电流150 mA,碘海醇270 mg I/mL及IDose 4迭代重建技术,C组(51例)采用管电压80 kV、管电流180 mA,碘海醇270 mg I/mL及IDose 4迭代重建技术,D组(52例)管电压120 kV、管电流120 mA,碘海醇370 mg I/mL及滤波反投影(FBP)重建技术。分析各组图像肾主动脉干CT值、噪声(SD)、信噪比(SNR)和噪声比(CNR),受检者接受CT有效剂量(ED)、容积CT剂量指数(CTDI vol)、剂量长度乘积(DLP)、碘摄入量以及重建图像评分差异和诊断效能。结果显示,A、B、C组重建图像评分优于D组,肾动脉主干CT值、SD、SNR、CNR均高于D组,B、C组肾动脉主干CT值、SD略低于A组。A、B、C组CTDI vol、DLP、ED均低于D组,B组CTDI vol、DLP、ED高于A组。A、B、C、D组诊断肾主动脉狭窄准确率分别为92.68%、86.49%、84.62%、82.86%。证实IDose 4迭代重建技术能降低受试者受辐射和造影剂剂量,提高成像质量,在低剂量CT肾动脉血管造影中具有较高可行性和实用性。     

On well-posedness for some dispersive perturbations of Burgers' equation

We show that the Cauchy problem for a class of dispersive perturbations of Burgers' equations containing the low dispersion Benjamin–Ono equation

${?}_{t}u?D_x^{\alpha }{?}_{x}u={?}_x(u^2),0<\alpha \le 1,$

is locally well-posed in $H^s(\mathbb{R})$ when $s>s_{\alpha }:=\frac{3}{2}?\frac{5\alpha }{4}$. As a consequence, we obtain global well-posedness in the energy space $H^{\frac{\alpha }{2}}(\mathbb{R})$ as soon as $\frac{\alpha }{2}>s_{\alpha }$, i.e. $\alpha >\frac{6}{7}$.     

On the role of a torsion‐like field in a scenario for the Spin Hall Effect

Starting from a field theory action that describes a Dirac fermion, we propose and analyze a model based on a low‐relativistic Pauli equation coupled to a torsion‐like term to study Spin Hall Effect (SHE). We point out a very particular connection between the modified Pauli equation and the (SHE), where what we refer to torsion as field playing an important role in the spin‐orbit (SO) coupling process. In this scenario, we present a proposal of a spin‐type current, considering the tiny contributions of torsion in connection with intrinsic anisotropy of the crystal electric field.     

范德瓦耳斯气液状态方程纵横谈

首先强调了范氏方程是气液系统的状态方程,范氏方程可以很好地说明物质气态和液态的相互转变．分析了焦-汤效应,简述了气体的液化与低温的获得．     

Photophysics of the Lanthanide Complexes with Conjugated Carboxylic Acids by Low Temperature Fluorescent Spectroscopy

In the context, some lanthanide (Eu³⁺, Tb³⁺ and Sm³⁺) complexes with conjugated carboxylic acids (pyridine-carboxylic acids derivatives) have been synthesized and characterized. The low temperature fluorescent spectra for these complexes have been measured at nitrogen atmosphere (77 K), indicating that the central Ln³⁺ ions locate in an equivalent coordination environment with low symmetry for most of these lanthanide complexes belonging to dimeric or polymeric structure. Therefore, the electronic dipole transition (supersensitive transition) (⁵D₀ → ⁷F₂ for Eu³⁺, ⁵D₄ → ⁷F₆ for Tb³⁺, ⁴G_5/2 → ⁶H_9/2 for Sm³⁺) and magnetic dipole transition (⁵D₀ → ⁷F₁ for Eu³⁺, ⁵D₄ → ⁷F₅ for Tb³⁺, ⁴G_5/2 → ⁶H_5/2 for Sm³⁺) show the regular change in the corresponding split number of fluorescent spectra, which can be realized to predict the fine structure of lanthanide complexes.     

Crystallization Behavior of Sol-Gel Derived Films by Self-Seeding Process

We propose the novel preparation method, Self-seeding Process, based on the following concept for low temperature crystallization of oxide films. Introduction of desirable inhomogeneity should give lowering of a crystallization temperature through heterogeneous nucleation accompanied with reduced activation energy. We carried out inspection of the above concept through use of PZT films. PZT gel films with the desirable inhomogeneity of microstructure were prepared, and their crystallization behaviors was examined. The PZT film was successfully crystallized at 500°C by the self-seeding process. The single phase (001) oriented PZT film with 0.55 m in thickness was obtained at 550°C for 5 min. The self-seeding process by microstructure control is efficient for the low temperature process of the oxide thin film.     

Covalent Organic Frameworks for Chemical and Biological Sensing

Covalent organic frameworks (COFs) are a class of crystalline porous organic polymers with polygonal porosity and highly ordered structures. The most prominent feature of the COFs is their excellent crystallinity and highly ordered modifiable one-dimensional pores. Since the first report of them in 2005, COFs with various structures were successfully synthesized and their applications in a wide range of fields including gas storage, pollution removal, catalysis, and optoelectronics explored. In the meantime, COFs also exhibited good performance in chemical and biological sensing, because their highly ordered modifiable pores allowed the selective adsorption of the analytes, and the interaction between the analytes and the COFs’ skeletons may lead to a detectable change in the optical or electrical properties of the COFs. In this review, we firstly demonstrate the basic principles of COFs-based chemical and biological sensing, then briefly summarize the applications of COFs in sensing some substances of practical value, including some gases, ions, organic compounds, and biomolecules. Finally, we discuss the trends and the challenges of COFs-based chemical and biological sensing.     

Hydrosilylation of alkynes by Ni(CO)3-stabilized silicon(II) hydride

Not copy and paste: Although β-diketiminato ligands have been employed for the stabilization of Ge(II) and Sn(II) hydrides, the corresponding Si(II) hydride is not accessible. However, coordination of silicon(II) to a {Ni(CO)(3)} fragment allowed the isolation of the first Si(II) hydride metal complex 1. This complex was used for the first silicon(II)-based and Ni(0)-mediated, stereoselective hydrosilylation of alkynes. R = phenyl, tolyl.     

新型的承载双金属氰化物络合催化剂

用双金属氰化物(DMC)络合催化剂可制得相对分子质量高、相对分子质量分布窄和不饱和度低的聚醚多元醇。为提高DMC催化剂的利用率,降低催化剂和聚醚的生产成本,国外开发了承载的DMC催化剂。它不仅可简化聚醚的后处理工艺,而且使聚醚的连续化大规模生产得以实现,因此代表了DMC催化剂的一个重要发展方向。