Nanoscale Defect Engineering and the Resulting Effects on Domain Wall Dynamics in Ferroelectric Thin Films

Defect engineering is one of the cornerstones of the modern electronics industry. Almost all electronic devices include materials that have been doped by ion bombardment. For materials where crystallinity is essential, such as ferroelectrics, defect type and concentration can vastly influence properties and are often used to optimize device performance. This study shows a method to effectively control the density and position on the nanoscale of defect sites in thin films of Pb(Zr,Ti)O₃ via focused ion beam microscopy. This allows for exceptional clarity of observation of the role of defects in nucleation, polarization switching, and domain wall interaction through investigation with piezoresponse force microscopy and transmission electron microscopy, adding insight to accepted but seldom‐demonstrated facts on defect‐induced effects. This nanoscale defect engineering can be used as a tool to control material properties, and furthermore, a route is demonstrated toward a practical application.     

双型钢混凝土梁正截面受弯性能的研究

介绍一种新型组合结构形式梁——双型钢混凝土梁,通过6组梁的四点加载静力弯曲试验研究双型钢混凝土梁的正截面抗弯承载力、变形、延性、极限曲率和极限弯矩等性能指标。试验结果显示,双型钢混凝土梁具有较高的承载能力和较好的变形延性,箍筋率、型钢翼缘尺寸、型钢间距、纵筋配筋率和销钉布置均对双型钢混凝土梁的开裂荷载和极限荷载有一定的影响。通过对比试验数据,对我国JGJ 138—2001《型钢混凝土技术规程》和YB 9082—97《钢骨混凝土结构设计规程》中抗弯计算式的混凝土部分和整体部分系数做了修正,得出双型钢混凝土梁的抗弯计算式。     

How receptor diffusion influences gradient sensing

Chemotaxis, or directed motion in chemical gradients, is critical for various biological processes. Many eukaryotic cells perform spatial sensing, i.e. they detect gradients by comparing spatial differences in binding occupancy of chemosensory receptors across their membrane. In many theoretical models of spatial sensing, it is assumed, for the sake of simplicity, that the receptors concerned do not move. However, in reality, receptors undergo diverse modes of diffusion, and can traverse considerable distances in the time it takes such cells to turn in an external gradient. This sets a physical limit on the accuracy of spatial sensing, which we explore using a model in which receptors diffuse freely over the membrane. We find that the Fisher information carried in binding and unbinding events decreases monotonically with the diffusion constant of the receptors.     

面向多级调度管理的融合型搜索引擎

云计算、物联网、社交网络等新兴服务模式的产生与发展,使得数据转变为一种基础资源,面向数据管理和取用的信息检索技术的重要性不断提高。结合调度管理业务的典型搜索需求,文中将信息服务模式的技术特征应用于调度管理领域,提出一种面向大电网多级调度管理一体化的融合型搜索引擎设计方法。该方法通过对不同类型数据的搜索集成,实现了分布式环境下的异构数据资源整合。针对所述算法进行了实验仿真和原型验证,对搜索算法进行了可行性评估和应用展望。     

PIXE and PIGE techniques for the analysis of Antarctic ice dust and continental sediments

An analytical procedure has been implemented in this work for an accurate geochemical characterization and quantitative analysis of the fine dust (particles diameter < 5 μm) trapped in Antarctic ice cores and the fine fraction of potential source areas (PSA) sediments by size selection, filtering and PIXE-PIGE combined measurements. The underestimation of concentrations of the lighter elements, like Na, Mg, Al and Si, due to X-ray self-absorption inside each individual aerosol particle, was also evaluated and the analytical overall accuracy tested by means of measurements performed on size selected certified mineral standards.     

Sonolytic Destruction of Trihalomethanes by Ultrasonic Irradiation

Ultrasonic irradiation was employed for the degradation of trihalomethanes (THMs) CHCl₃, CHBrCl₂, CHBr₂Cl, CHBr₃, and CHI₃. The effects of various reaction and sonication conditions on the sonodegradation of THMs were examined and explained by the principles of sonochemistry. Batch experiments were conducted at an ultrasonic frequency of 20 kHz and power of 18.4 W. The sonodegradation rate of the THMs increased with increasing the solution temperature or the acoustic intensity, whereas aqueous solution pH, solute concentration up to 10 mg/L, and water quality did not affect the sonolytic destruction of the THMs. Ultrasonic removal of CHCl₃, CHBrCl₂, CHBr₂Cl, and CHBr₃ was not affected by the presence of other compounds as a mixture in the aqueous solution, while CHI₃ sonolysis was enhanced. Hydrogen peroxide, nitrate, chloride, bromide, and iodide were identified and quantified as the reaction inorganic products. Degradation rates and efficiencies followed the decreasing order of: CHCl₃ > CHBrCl₂ > CHBr₂Cl > CHBr₃ > CHI₃, while the electrical energy consumed per liter of contaminated aqueous solution treated was found to be in inverse order.     

A survey on the intended purposes and perceived utility of preoperative cardiology consultations

N-methyl-D-aspartate (NMDA) antagonists, such as MK801, delay the development of morphine tolerance. Magnesium, a noncompetitive NMDA antagonist, reduces postoperative morphine requirements. The present study was designed to evaluate the effects of intrathecal co-administration of magnesium sulfate with morphine on antinociceptive potentiation, tolerance, and naloxone-induced withdrawal signs. Magnesium sulfate (40-60 microg/h) co-administration for 7 days, similar to MK801 (10 nmol/h), prevented the decline in antinociceptive response compared with morphine (20 nmol/h). Magnesium sulfate (60 microg/h) produced no antinociception, but co-infused with morphine (1 nmol/h), it resulted in potentiated antinociception compared with morphine throughout the 7-day period. Probe morphine doses after 7-day infusions demonstrated a significantly greater 50% effective dose value for morphine 1 nmol/h (109.7 nmol) compared with saline (10.9 nmol), magnesium sulfate 60 microg/h (10.9 nmol), and magnesium sulfate 60 microg/h plus morphine 1 nmol/h (11.2 nmol), which indicates that magnesium had delayed morphine tolerance. Morphine withdrawal signs after naloxone administration were not altered by the co-infusion of magnesium sulfate. Cerebrospinal fluid magnesium levels after intrathecal magnesium sulfate (60 microg/h) for 2 days increased from 17.0 +/- 1.0 microg/mL to 41.4 +/- 23.6 microg/mL, although serum levels were unchanged. This study demonstrates antinociceptive potentiation and delay in the development of morphine tolerance by the intrathecal coinfusion of magnesium sulfate and morphine in the rat. Implications: The addition of magnesium sulfate, an N-methyl-D-aspartate antagonist, to morphine in an intrathecal infusion provided better analgesia than morphine alone in normal rats. These results suggest that intrathecal administration of magnesium sulfate may be a useful adjunct to spinal morphine analgesia.     

The effect of heat convection on drying of porous semi-infinite space

An analytical study is presented for rate processes, including change of phase for a semi-infinite porous substance exposed to a jump in external temperature. The model assumes two distinct regions separated by a moving interface where the change of phase takes place. One region maintains its initial concentration of liquid-solid volatiles while the second is devoid of them. Heat convection by the outflowing gaseous volatiles is accounted for, and its effect on the rate of evaporation and pressure build-up is illustrated for a case of water drying from a porous matrix.     

Water-leaching rates of halides from polymers

Water-leaching experiments of halides from polymers were carried out in batch and continuous systems. The effects of flow rate, temperature, and salt content on the leaching kinetics were investigated. Different thermoplastic polymers were used as the salt carrier, and the release kinetics from them was established. NaCl, NaBr, and NaI were leached out completely from nylons, while NaF could only be partially removed. Release mechanisms involving diffusion, capillary flow, and fracturing were described based upon the leaching kinetics and porosity distribution in the resulting foams.