应用键轨道连接矩阵方法预测烷烃折光率.

应用键轨道连接矩阵方法提取结构参数PX1CC和PX1CH， 并用于建立预测烷烃折光率的QSPR模型．该模型不仅预测精度较高(其误差仅为0.0048)，而且模型中采用的参数表达了直接与分子的折光能力相关的结构信息(即烷烃分子中电子被极化的能力)．此参数提取简单，既具备拓扑指数简单、易算，物理意义明确．     

Ankyrin repeat and SOCS box containing protein 4 (Asb-4) colocalizes with insulin receptor substrate 4 (IRS4) in the hypothalamic neurons and mediates IRS4 degradation

Background

Cigarette smoking enhances the risk of stroke. However, the underlying molecular mechanisms are largely unknown. The present study established an in vivo rat secondhand cigarette smoking (SHS) model and examined the hypothesis that SHS upregulates endothelin receptors with increased cerebrovascular contraction via the Raf/extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinases (MAPK) pathway.

Results

Rats were exposed to SHS for up to 8 weeks. The cerebral artery vasoconstriction was recorded by a sensitive myograph. The mRNA and protein expressions for endothelin receptors in cerebral arteries were studied by real-time PCR and Western blot. Compared to fresh air exposed rats, cerebral arteries from SHS rats exhibited stronger contractile responses (P < 0.05) mediated by endothelin type A (ET_A) receptors. The expressions of mRNA and protein for ET_A receptors in the cerebral arteries from SHS rats were higher (P < 0.05) than that in control. SHS did not affect endothelin type B (ET_B) receptor-mediated contractions, mRNA or protein levels. The results suggest that SHS upregulates ET_A, but not ET_B receptors in vivo. After SHS exposure, the mRNA levels of Raf-1 and ERK1/2, the protein expression of phosphorylated (p)-Raf-1 and p-ERK1/2 were increased (P < 0.05). Raf-1 inhibitor, GW5074 suppressed the enhanced ET_A receptor-mediated contraction, mRNA and protein levels induced by SHS. In addition, GW5074 inhibited the SHS-caused increased mRNA and phosphorylated protein levels of Raf-1 and ERK1/2, suggesting that SHS induces activation of the Raf/ERK/MAPK pathway.

Conclusions

SHS upregulates cerebrovascular ET_A receptors via the Raf/ERK/MAPK pathway, which provides novel understanding of mechanisms involved in SHS-associated stroke.     

A realization of digital wireless transmission for MRI signals based on 802.11b

In this paper, a digital wireless transmission system based on 802.11b standard for magnetic resonance imaging (MRI) application is designed and built for the first time to eliminate the interference aroused by coil array cables. The analysis shows that the wireless receiver has a very high sensitivity to detect MRI signals. The modulation technique of differential quadrature phase shift keyed (DQPSK) can be applied to MRI data transmission with rate of 2 Mbps and bandwidth of 2 MHz. The bench test verifies that this wireless link has a dynamic range over 86 dB supporting up to 3 T MRI system data transmission. The 2D spin echo imaging of phantom is performed and the SNR of the image obtained by the wireless transmission can be comparable with that got by the coaxial cables.     

Mechanism of Striation in Dielectric Barrier Discharge

The mechanism of striations in dielectric barrier discharge in pure neon is studied by a two-dimensional particle- in-cell/Monte Carlo collision （PIC-MCC） model. It is shown that the striations appear in the plasma background, and non-uniform electrical field resulting from ionization and the negative wall charge appear on the dielectric layer above the anode. The sustainment of striations is a non-local kinetic effect of electrons in a stratified field controlled by non-elastic impact with neutral gases. The striations in the transient dielectric barrier discharge are similar to those in dc positive column discharge.     

High pulse energy mode-locked multicore photonic crystal fiber laser

A high pulse energy passively mode-locked fiber laser operating in the all-normal dispersion regime is demonstrated. The gain material is an Yb-doped multicore photonic crystal fiber with 18 cores in array-type geometry. Robust and self-starting mode locking is achieved using a fast semiconductor saturable absorber mirror. The laser generates 180?nJ chirped pulses at a 14.48?MHz repetition rate for an average power of 2.6?W. The 1.15?ps output pulses are compressed to 690?fs outside the cavity.     

三价羰基硫离子(OCS3+)二体解离过程模拟研究

基于Gaussian量子化学模拟软件采用不同基组(6-31G^**和TZVP)下的B3LYP方法对基态三价羰基硫离子(OCS³⁺)的势能曲线进行分析,得到了三价羰基硫离子可能的解离通道.当固定C—O键长为OCS分子的构型键长时(2.1a.u.),通过模拟基态OCS³⁺离子沿着C—S键断裂的势能曲线,发现沿着C—S键的势能曲线是一个具有小势垒的排斥态;相反,当固定C—S键长为OCS分子的构型键长时(2.9a.u.),基态OCS³⁺离子沿着C—O键的势能曲线是一个势垒较大的排斥态,根据弗兰克-康登原理可知,基态OCS³⁺离子倾向于以断裂C—S键的方式进行解离.通过搜索基态OCS³⁺离子过渡态、IRC路径分析进一步确定了基态OCS³⁺离子具体的解离通道：OCS³⁺→CO⁺+S²⁺.最后通过对反应物和产物的Mulliken电荷分布和键长的分析,得到与前面一致的结论.     

Classification of Curves in 2D and 3D via Affine Integral Signatures

We propose new robust classification algorithms for planar and spatial curves subjected to affine transformations. Our motivation comes from the problems in computer image recognition. To each planar or spatial curve, we assign a planar signature curve. Curves, equivalent under an affine transformation, have the same signature. The signatures are based on integral invariants, which are significantly less sensitive to small perturbations of curves and noise than classically known differential invariants. Affine invariants are derived in terms of Euclidean invariants. We present two types of signatures: the global and the local signature. Both signatures are independent of curve parameterization. The global signature depends on a choice of the initial point and, therefore, cannot be used for local comparison. The local signature, albeit being slightly more sensitive to noise, is independent of the choice of the initial point and can be used to solve local equivalence problem. An experiment that illustrates robustness of the proposed signatures is presented.     

Strong convergence of a new composite iterative method for equilibrium problems and fixed point problems

In this paper, we propose a new composite iterative method for finding a common point of the set of solutions of an equilibrium problem and the set of fixed points of a countable family of nonexpansive mappings in a Hilbert space. It is proved that the sequence generated by the iterative scheme converges strongly to a common point of the set of solutions of an equilibrium problem and the set of fixed points of a countable family of nonexpansive mappings. Our results improve and extend the corresponding ones announced by many others.     

一类具有垂直传播的捕食传染病模型的全局分析

通过假设捕食系统中疾病只在捕食者种群中传播,被传染的易感者经过一段潜伏期后才具有传染性,染病者康复后对该病具有永久免疫力,建立了一类具有垂直传播的捕食系统的传染病模型(SEIR),运用极限系统理论,分两种情形讨论了系统平衡点的存在性及局部稳定性,利用Liapunov函数和二次复合矩阵等方法,得到了平衡点全局渐近稳定的条件.     

光子晶体光纤在熔接夹具中的受力分析

运用接触力学和圆环压溃强度理论对由V型槽固定的光子晶体光纤进行了受力分析。分别考虑了两种极限情况,以推导光纤中的应力分布。第一种情况假设光纤是完全由纯石英材料制成的内部均匀的实芯圆柱体;第二种情况是把光纤假设成一个空芯圆柱体。根据这两种极限情况推导出了光子晶体光纤受力后光纤内部的最大应力点位于平行于接触面的外层空气孔的附近。采用有限元方法验证了此结论,计算出了光子晶体光纤可能承受的最大压力,并给出了光子晶体光纤在V型槽中的应力分布和变形情况。