PbTiO(3) nanorod arrays grown by self-assembly of nanocrystals

Arrays of ferroelectric lead titanate (PbTiO(3)) nanorods have been grown on a substrate by a novel template-free method. Hydrothermal treatment of an amorphous PbTiO(3) precursor in the presence of a surfactant and PbTiO(3) or SrTiO(3) substrates resulted in the growth of PbTiO(3) nanorod arrays aligned perpendicular to the substrate surface. Two steps in the growth mechanism were demonstrated: first an epitaxial layer was formed on the substrate; this was followed by self-assembly of nanocrystals forming a mesocrystal layer which matured into arrays of PbTiO(3) nanorods.     

Genetic Risk Scores for Maternal Lipid Levels and Their Association with Preterm Birth

Maternal lipid profiles are associated with risk for preterm birth (PTB), although the lipid component and effect size are inconsistent between studies. It is also unclear whether these associations are the result of excessive changes in lipid metabolism during pregnancy or genetic variability in genes controlling basal lipid metabolism. This study investigates the association between genetic risk scores (GRS) for four lipid components (high-density lipoprotein [HDL-C], low-density lipoprotein [LDL-C], triacylglycerols [TAG], and total cholesterol [TC]) with risk for PTB. Subjects included 954 pregnant women from California for whom second trimester serum samples were available, of which 479 gave birth preterm and 475 gave birth at term. We genotyped 96 single-nucleotide polymorphisms, which were selected from genome-wide association studies of lipid levels in adult populations. Lipid-specific GRS were constructed for HDL-C, LDL-C, TAG, and TC. The associations between GRS and PTB were analyzed using logistic regression. A higher HDL-C GRS was associated with increased risk for PTB overall and spontaneous PTB. Higher TAG and TC GRS were associated with decreased risk for PTB overall and spontaneous PTB. This study identifies counter-intuitive associations between lipid GRS and spontaneous PTB. Further replication studies are needed to confirm these findings, but they suggest that our current scientific understanding of the relationship between lipid metabolism, PTB, and genetics is incomplete.     

含N、S羟基衍生物的合成及其摩擦学性能

合成了1〖DK〗,2 ［N〖DK〗,N 二正丁基二硫代氨基甲酸基］乙醇（NSO1）和2 ［2 苯并噻唑基］硫代乙醇（NSO2）2种添加剂,并采用FT IR、ESI MS和元素分析手段表征了其结构。考察了NSO1和NSO2的热稳定性及其在菜籽油（RO）中的油溶性。采用四球摩擦磨损试验研究了2种添加剂在菜籽油中的减摩、抗磨以及极压性能。采用扫描电子显微镜（SEM）、能谱分析仪（EDS）观察和分析了钢球磨斑表面形貌及元素组成。结果表明, NSO2的热稳定性优于NSO1, 其摩擦学性能也明显优于NSO1。NSO2优异的摩擦学特性主要得益于其分子中含有杂环结构,在边界润滑中,能够起到极压、抗磨的作用。     

一种含氮硫杂环硼酸酯的制备及摩擦学性能

以2-[2-苯并噻唑基]为原料合成了2-[2-苯并噻唑基]硫代乙醇(BTE),再以该BTE合成了一种含氮硫杂环硼酸酯(SNHB)添加剂,并采用FTIR、元素分析对其结构进行了表征。考察了BTE、SNHB的油溶性、热稳定性以及SHNB的水解稳定性。采用四球摩擦磨损试验研究了BTE及SNHB在菜籽油中的减摩、抗磨以及极压性能。采用SEM、EDS观察和分析了钢球磨斑表面形貌及元素。研究结果表明,合成的产物为目标产物BTE和SNHB;在相同的试验条件下,SNHB和BTE在菜籽油中完全溶解,具有较好的油溶性;SNHB和BTE的分解温度范围分别是从270.50~396.01℃、253.04~326.83℃,两者均具有良好的热稳定性,且SNHB的热稳定性优于BTE;SNHB的水解时间超过7天,而市售的硼酸三异丙酯仅为10 min,SNHB有较好的水解稳定性;在不同载荷、添加比例等条件下SNHB的摩擦学性能明显优于BTE。     

Effect of equine chorionic gonadotropin treatment during a progesterone-based timed artificial insemination program on reproductive performance in seasonal-calving lactating dairy cows

The aim of this study was to investigate the effect of progesterone (P4)-based timed artificial insemination (TAI) programs on fertility in seasonal-calving, pasture-based dairy herds. A total of 1,421 lactating dairy cows on 4 spring-calving farms were stratified based on days in milk (DIM) and parity and randomly allocated to 1 of 3 treatments: (1) control: no hormonal treatment; cows inseminated at detected estrus; (2) P4-Ovsynch: cows received a 7-d P4-releasing intravaginal device (PRID Delta; CEVA Santé Animale, Libourne, France) with 100 μg of a gonadotropin-releasing hormone (GnRH) analog (Ovarelin; CEVA Santé Animale) at PRID insertion, a 25-mg injection of PGF_2α (Enzaprost; CEVA Santé Animale) at PRID removal, GnRH at 56 h after device removal and TAI 16 h later; (3) P4-Ovsynch+eCG: the same as P4-Ovsynch, but cows received 500 IU of equine chorionic gonadotropin (eCG; Syncrostim; CEVA Santé Animale) at PRID removal. At 10 d before mating start date (MSD), all cows that were ≥35 DIM were examined by transrectal ultrasound to assess presence or absence of a corpus luteum; body condition score (BCS) was also recorded. Pregnancy diagnosis was performed by transrectal ultrasonography 30 to 35 d after insemination. Overall pregnancy/AI (P/AI) was not different between groups (50.9, 49.8, and 46.3% for control, P4-Ovsynch, and P4-Ovsynch+eCG, respectively) but the 21-d pregnancy rate was increased by the use of synchronization (35.0, 51.7, and 47.2%, respectively). Compared with the control group, synchronization significantly reduced the interval from MSD to conception (34.6, 23.0, and 26.5 d, respectively) and consequently reduced the average days open (98.0, 86.0, and 89.0 d). Across all treatment groups, DIM at the start of synchronization affected P/AI (42.3, 49.5, and 53.9% for <60, 60–80, and >80 DIM, respectively), but neither parity (46.5, 50.4, and 48.4% for parity 1, 2, and ≥3, respectively) nor BCS (44.0, 49.4, and 58.6% for ≤2.50, 2.75–3.25, and ≥3.50, respectively) affected the likelihood of P/AI. Two-way interactions between treatment and DIM, parity, or BCS were not detected. In conclusion, the use of TAI accelerated pregnancy establishment in cows in a pasture-based system by reducing days open, but eCG administration at PRID removal did not affect P/AI.     

面向积雨云检测的模糊支持向量机

为解决SVM在积雨云检测中的难题,本文构造了一种模糊支持向量机(FSVM),首先根据训练样本的分布特性,定义了相邻样本距离类中心的距离变化率,然后通过计算距离变化率来剔除训练集中可能的噪声与野值样本,从而有效克服了传统基于紧密度的FSVM在计算最小超球半径时易受噪声与野值干扰的缺点,使得所计算的隶属度能更好地反映不同样本的差异。实验结果表明,对于FY2D卫星云图,采用从不同通道所提取的光谱特征,本文方法的积雨云检测准确率与传统SVM和基于紧密度的FSVM相比,分别平均提高2%和1%,且具有更强的适应性及噪声鲁棒性。     

Nonlinear wave scattering at the flexible interface of a granular dimer chain

Uncompressed granular dimer chains composed of repetitive pairs of heavy-light spherical, linearly elastic beads exhibit interesting intrinsic responses. The dynamics of these highly discontinuous nonlinear media is governed by the mass ratio scaling the mass disparity of each heavy-light pair of beads. In particular, it has been theoretically and experimentally shown that they support countable infinities of anti-resonances at a discrete set of mass ratios leading to solitary pulses propagating through the dimers with no attenuation or distortion. Conversely, they support countable infinities of resonances at a different discrete set of mass ratios, leading to substantial and rapid attenuation of propagating pulses due to energy scattering from low-to-high frequencies and wavenumbers by means of radiating traveling waves. In this work we computationally study nonlinear scattering of impeding pulses at the interface of an impulsively excited dimer chain with a dispersive elastic boundary, namely, a finite linear string resting on an elastic foundation. We develop a computational algorithm which, through iteration and interpolation at successive time steps, accurately computes (and ensures convergence of) the highly discontinuous contact forces and displacements at the flexible interface of the granular medium. This enables accurate computation of wave transmission, reflection, localization or multi-scale nonlinear scattering at the flexible interface for varying mass ratios of the dimer and the interface parameters. We show that, depending on the mass ratio of the dimer and the stiffness of the elastic foundation, the nonlinear scattering at the flexible interface may lead to significant reduction of the maximum contact force at the interface, and, thus, drastically affect the transmitted and reflected energy at the flexible boundary. In fact, an inverse relation between the stiffness of the elastic foundation and the residual energy transferred from the dimer chain to the flexible boundary is found. Moreover, for sufficiently small mass ratios of the dimer chain transient breathers are realized close to the interface in the form of localized “fast” oscillations of light granules of the dimer that entrap shock energy and then release in a slow time scale back to the chain and the flexible boundary. This work paves the way for studying highly discontinuous and nonlinear scattering phenomena at interfaces of granular media with flexible continua.     

Muon kinetics in heat treated Al (–Mg)(–Si) alloys

Al–Mg–Si alloys are heat-treatable and rely on precipitation hardening for their mechanical strength. We have employed the technique of muon spin relaxation to further our understanding of the complex precipitation sequence in this system. The muon trapping kinetics in a material reveals a presence of atom-sized defects, such as solute atoms (Mg and Si) and vacancies. By comparing the muon kinetics in pure Al, Al–Mg, Al–Si and Al–Mg–Si when held at different temperatures, we establish an interpretation of muon trapping peaks based on different types of defects. Al–Mg–Si samples have a unique muon trapping peak at temperatures around 200 K. This peak is highest for samples that have been annealed at 70–150 °C, which have microstructures dominated by a high density of clusters/Guinier–Preston zones. The muon trapping is explained by the presence in vacancies inside these structures. The vacancies disappear from the material when the clusters transform into more developed precipitates during aging.