Strong magnetic instability in correlated metallic Bi(2)Ir(2)O(7)

We report an experimental/theoretical study of single-crystal Bi(2)Ir(2)O(7) that possesses a metallic state with strongly exchange-enhanced paramagnetism. The ground state of Bi(2)Ir(2)O(7) is characterized by the following features: (1) a divergent low-temperature magnetic susceptibility that indicates no long-range order down to 50?mK; (2) strongly field-dependent coefficients of the low-temperature T and T(3) terms of the specific heat; (3) a conspicuously large Wilson ratio R(W)?≈?53.5; and (4) unusual temperature and field dependences of the Hall resistivity that abruptly change below 80?K, without any clear correlation with the magnetic behavior. All these unconventional properties suggest the existence of an exotic ground state in Bi(2)Ir(2)O(7).     

三硼酸铋晶体及其高温熔体结构的拉曼光谱研究

测量了BiB3O6晶体从常温到熔融态的拉曼光谱,考察了其温致结构变化和预测了熔体的结构基元。同时,采用量子化学从头计算和密度泛函理论对拉曼光谱进行了计算和结构分析。结果表明,随着温度的升高,对包含阳离子Bi的外部晶格和[BO3]3-硼氧三角形基团结构的温致结构影响有限,却有效地削弱了[BO4]5-硼氧四面体基团结构,其松弛度增加,稳定性变差,并在熔体结构中彻底消失。研究表明BiB3O6熔体主要以硼氧六元环[B6O12]6-的形式存在,阳离子Bi起电荷平衡作用,其氧配位数为3,有别于晶体中的6。     

Bacterial Reduction of Cr(VI) at Technical Scale—The Malaysian Experience

The bacterial reduction of Cr(VI) from industrial wastewater was evaluated using a 2.0-m³ bioreactor. Liquid pineapple waste was used as a nutrient for the biofilm community formed inside the bioreactor. The use of rubber wood sawdust as packing material was able to immobilize more than 10⁶?CFU?mL^?1 of Acinetobacter haemolyticus cells after 3?days of contact time. Complete reduction of 15?C240?mg?L^?1 of Cr(VI) was achieved even after 3?months of bioreactor operation. Cr(VI) was not detected in the final effluent fraction indicating complete removal of Cr from solution from the flocculation/coagulation step and the unlikely re-oxidation of Cr(III) into Cr(VI). Impatiens balsamina L. and Gomphrena globosa L. showed better growth in the presence of soil?Csludge mixture compared to Coleus scutellarioides (L.) Benth. Significant amounts of Cr accumulated at different sections of the plants indicate its potential application in Cr phytoremediation effort. The bacterial-based system was also determined not to be detrimental to human health based on the low levels of Cr detected in the hair and nail samples of the plant operators. Thus, it can be said that bacterial-based Cr(VI) treatment system is a feasible alternative to the conventional system especially for lower Cr(VI) concentrations, where sludge generated can be used as growth supplement for ornamental plant as well as not detrimental to the health of the workers.     

The Impact of Long-Term In Vitro Expansion on the Senescence-Associated Markers of Human Adipose-Derived Stem Cells

Human adipose-derived stem cells (ASCs) have generated a great deal of excitement in regenerative medicine. However, their safety and efficacy issue remain a major concern especially after long-term in vitro expansion. The aim of this study was to investigate the fundamental changes of ASCs in long-term culture by studying the morphological feature, growth kinetic, surface marker expressions, expression level of the senescence-associated genes, cell cycle distribution and ß-galactosidase activity. Human ASCs were harvested from lipoaspirate obtained from 6 patients. All the parameters mentioned above were measured at P5, P10, P15 and P20. Data were subjected to one-way analysis of variance with a Tukey post hoc test to determine significance difference (P?相似文献   

Shear and extensional rheology of polyacrylonitrile solution: effect of ultrahigh molecular weight polyacrylonitrile

The effect of ultrahigh molecular weight polyacrylonitrile (UHMWPAN) on the shear and extensional rheological behavior of PAN solutions were studied. The PAN solutions were prepared by dissolving medium molecular weight polyacrylonitrile in dilute UHMWPAN/dimethyl sulfoxide solutions. The results of shear rheological measurements indicated that the existence of UHMWPAN reduced the shear-thinning but increased the characteristic relaxation time and the elasticity of PAN solutions. Moreover, the PAN solutions containing UHMWPAN exhibited much more evident strain-hardening behavior than the solution without UHMWPAN. It was found from the results of extensional rheological measurements that the strain hardening and elasticity of PAN solutions increased greatly with the increase of molecular weight or content of UHMWPAN in the solutions. PAN solutions containing a small amount of UHMWPAN have better drawability and favor the increase of jet stretch ratio in dry-jet wet spinning of PAN precursor fibers.     

基于PASCO数据采集装置的激光测速实验探究

探究了基于光多普勒效应和PASCO数据采集装置的激光测速实验,分别获取了液体流速和固体(光纤探针)运动速度的多普勒信号,利用多普勒信号可以测定它们的速度,并用“双光纤测速法”对比说明了测固体运动速度的精度.     

Al2O3增强的Co2-C98/Al2O3/Si异质结的光伏效应

随着能源危机的加剧,太阳能电池作为开发和利用太阳能的一种普遍形式, 日益受到世界各国的重视.随着太阳能电池向着高效率、薄膜化、无毒性和原材料丰富的方向发展, 单纯的硅系太阳能电池已经无法达到这样的要求,因此新的材料和工艺的开发利用迫在眉睫. 本文研究了碳材料在硅异质节上实现光伏效应的改善及其可能在太阳能电池上的应用. 采用脉冲激光沉积方法制备的Co₂-C₉₈/Al₂O₃/Si异质结构在标准日光照射 (AM1.5, 100 mW/cm²)条件下,可获得0.447 V的开路电压和18.75 mA/cm²的电流密度, 转换效率可达3.27%.通过电容电压特性和暗条件下的电输运性能测量, 证明了氧化铝层的引入不但对单晶硅的表面起到了物理钝化作用,减小了反向漏电流, 使异质结界面缺陷、界面能级和复合中心减少,还起到了场效应钝化作用, 增加了异质结界面的势垒高度,增加了开路电压,使异质结的光伏效应显著增强.     

Origin在太阳能电池基本特性测定实验中的数据处理及分析

本文测试了太阳能电池的输出特性,并利用Origin软件对实验数据进行了计算、绘图和数据拟合,得到较好的实验结果.表明Origin软件为大学物理实验提供了一种简便、适用的实验数据处理方法,提高了实验教学效果.     

Comparison of <Emphasis Type="Italic">c</Emphasis>-Nd:YVO<Subscript>4</Subscript>/YVO<Subscript>4</Subscript> raman lasers and <Emphasis Type="Italic">c</Emphasis>-Nd:YVO<Superscript>4</Superscript> self-Raman lasers

Raman lasers based on c-Nd:YVO₄ crystals can generate 1178 nm Stokes line, which can be frequency-doubled to realize 589 nm sodium lasers. We make comparative experimental studies of c-Nd:YVO₄/YVO₄ Raman lasers and c-Nd:YVO₄ self-Raman lasers. About these two kinds of lasers, the output characteristics of power, center wavelength and beam quality are measured and compared.     

Phase transition,dielectric and piezoelectric properties of NaNbO3–Bi0.5Li0.5TiO3 lead-free ceramics

Lead-free ceramics (1?x)NaNbO₃–xBi_0.5Li_0.5TiO₃ have been fabricated by an ordinary sintering technique, and their electric properties and temperature characteristics have been studied. All the ceramics possess a perovskite structure with orthorhombic symmetry, indicating that (Bi_0.5Li_0.5)TiO₃ diffuses into NaNbO₃ lattices to form a new solid solution. A low (Bi_0.5Li_0.5)TiO₃ doping level transforms the NaNbO₃ ceramics from antiferroelectric to ferroelectric. The ceramics with x ≤ 0.075 are normal ferroelectric, and the ferroelectric-paraelectric phase become diffusives with the doping level of Bi_0.5Li_0.5TiO₃ increasing. As x increases, the Curie temperature of the ceramics decreases linearly, while the relative permittivity ε_r increases. 0.925NaNbO₃–0.075(Bi_0.5Li_0.5)TiO₃ ceramic exhibits the relatively large piezoelectric constant (d₃₃ = 58 pC/N), high Curie temperature (T_C = 228 °C) and good temperature stability, suggesting that the ceramics are one of new possible candidates for lead-free piezoelectric materials.