Decrease in optical density as a results of germination of Alicyclobacillus acidoterrestris spores under high hydrostatic pressure

Alicyclobacillus acidoterrestris is a spore-forming bacterium, causing spoilage of juices. The spores of these bacteria have the ability to survive in the typical conditions used for thermal pasteurization. Therefore, the use of other techniques such as high hydrostatic pressure is considered for their inactivation. The effect of hydrostatic pressure of 200–500 MPa, at temperatures 4–50 °C for 15 min, on the dynamics of germination of A. acidoterrestris spores in apple juice and pH 4 buffer was studied. To estimate the share of germinated spores, the method of determining the optical density at a wavelength of 660 nm (OD₆₆₀) was used. Parameters of hydrostatic pressure treatment used in this work affected the dynamics of germination of A. acidoterrestris spores in apple juice, and the temperature had the greatest effect. The results indicate that nutrients present in apple juice can promote the germination of A. acidoterrestris spores.     

高压电导研究

高压下物质结构和性质会发生很大的改变，电导对于认识压力的作用效应和寻找新的导电材料具有重要意义．高压电导研究所采用的设备主要有金刚石压腔、超高压大腔体装置(大压机)以及高压电导池三种．金刚石压腔可达550GPa压力；超高压大腔体装置压力一般在30GPa以下，可以提供较大体积的样品；高压电导池主要进行流体的电导研究，压力在400MPa以下，有静止和流动两种类型，流动式高压电导池是近年来才发展起来的，其准确方便．文章对目前高压电导的研究进行简单的介绍和分析．     

高压电导研究

高压下物质结构和性质会发生很大的改变,电导对于认识压力的作用效应和寻找新的导电材料具有重要意义.高压电导研究所采用的设备主要有金刚石压腔、超高压大腔体装置（大压机）以及高压电导池三种.金刚石压腔可达550GPa压力;超高压大腔体装置压力一般在30GPa以下,可以提供较大体积的样品;高压电导池主要进行流体的电导研究,压力在400MPa以下,有静止和流动两种类型,流动式高压电导池是近年来才发展起来的,其准确方便.文章对目前高压电导的研究进行简单的介绍和分析.     

The variability of times to detect growth from individual Clostridium botulinum type E endospores is differentially affected by high pressure treatments

High pressure thermal (HPT) processing is a candidate technology for the production of safe and stable food. However, little is known about the effect of HPT or high hydrostatic pressure (HHP) treatments at ambient temperature on the variability of times to detect growth from individual spores. We investigated this effect by treating Clostridium botulinum type E spores with HHP (200–600?MPa, 20°C) and HPT (600?MPa, 80°C and 800?MPa, 60°C). Our results indicate that the mean detection times increase and the frequency distribution shifts toward longer times when HHP treatment intensity is increased. HPT treatments result in a highly scattered distribution. In contrast, pressure levels ≤300?MPa decrease detection times and heterogeneity of their distribution, which could lead to an increase in the potential risk originating from C. botulinum type E spores. Data provided here could help to refine risk assessment regarding this important food intoxicator.     

Phase transition of samarium under high pressure

Abstract

The DAC X-ray power photograph method was employed for studing the phase transition of samarium up to 26.3 GPa. The experimental results show that the dhcp and fcc high pressure phase of Sm appeared at about 4.0 and 12.5 GPa and room temperature respectively. The dhcp phase was kept until 19.6 GPa. A model for Sm-type -? dhcp -? fcc phase transition is provided in this paper.     

Gold under high pressure

Abstract

First principle predictions for the equation of state of gold using solid and liquid state theories are compared up to combined pressures and temperatures of 600 GPa and 17 000 K with static diamond anvil cell compression, ultrasonic measurements and shock Hugoniot data which include a recent laser driven shock Hugoniot points at 600 GPa. Excellent agreement between theoretical and experimental data is observed. The theoretically estimated 300 K isotherm agrees to within 2 GPa with the isotherm that has been measured to 70 GPa using the diamond anvil cell. The structural energy estimates show that the normal f.c.c. phase remains stable under pressure. The estimate of the shock Hugoniot temperature of gold at 600 GPa based on a liquid state model is consistent with the measurements of laser induced shock luminescence, which in fact provides an experimental determination of the temperature of gold above its Hugoniot melting point. The powerful means provided by theory in the prediction of material properties of gold at ultra high pressures and temperatures is significant because gold is an efficient converter of laser energy into soft X-rays and is a potential candidate as a standard for high pressure, high temperature work.     

高温超导的压力效应研究

从修正的依赖时间的金兹堡-朗道方程出发研究高温超导体的压力效应，考虑序参量为一个复数. 在外界压力作用下，理论上获得了压强与高温超导温度的一些表达式.在一些特殊情况下，得到高温超导的临界温度T随外压强的增加而降低；在另外某些条件下高温超导的临界温度T_C随外压强的增加而增加.外部施加的压强，只有一部分反映在高温超导态. 关键词： 高温超导 压强 临界温度     

高温高压下钙钛矿晶体结构变化

最近高压单晶X射线衍射实验明确显示正交晶系（Pbnm或Pnma）（钙钛矿）ABO3的高压压缩行为完全由晶体框架结构（framework）中的BO6八面体和AO12多面体的相对压缩性所确定,即对一些钙钛矿晶体,BO6较AO12多面体更易压缩时,压力导致晶体结构向高对称性结构演变;对另外一些钙钛矿,BO6较AO12多面体更不易压缩时,压力导致晶体结构向低对称性结构演变.基于价键匹配关系假设,建立多面体压缩率之间关系：βB/βA=MA/MB,由价键参数和常压晶体结构数据计算参量Mi,可以估计BO6和AO12多面体的相对压缩率,从而正确地预言高压压缩行为.文章最后引入高温高压钙钛矿倾斜相变的一般性规律,即MA/MB＞1时,相变温度和高压关系为dTc/dP＜0,当MA/MB＜1时,dTc/dP＞0。     

高温高压下钙钛矿晶体结构变化

最近高压单晶X射线衍射实验明确显示正交晶系(Pbnm或Pnma) （钙钛矿）ABO3的高压压缩行为完全由晶体框架结构(framework)中的BO6八面体和AO12多面体的相对压缩性所确定,即对一些钙钛矿晶体,BO6较AO12多面体更易压缩时,压力导致晶体结构向高对称性结构演变;对另外一些钙钛矿,BO6较AO12多面体更不易压缩时,压力导致晶体结构向低对称性结构演变.基于价键匹配关系假设,建立多面体压缩率之间关系,由价键参数和常压晶体结构数据计算参量, 可以估计BO6和AO12多面体的相对压缩率,从而正确地预言高压压缩行为.文章最后引入高温高压钙钛矿倾斜相变的一般性规律.     

极端条件下锆的动力学稳定性研究

过渡金属Zr具有优良的物理、化学及力学性能, 具有广泛的应用价值. 主要通过新近发展的自洽晶格动力学方法, 充分考虑声子间的相互作用, 成功获得了β-Zr的高温高压声子色散曲线, 预测了β-Zr在相图中能够稳定存在的区域, 进一步比较α-Zr, ω-Zr和β-Zr的自由能, 获得了α-β 及ω-β 相变的相边界, 构建了Zr的参考相图. 同时, 也获得了β-Zr的高温状态方程及热膨胀系数, 能够为构建Zr的全区物态方程提供有益的参考.     

FeSi2合金在高压下的凝固

研究了压力对FeSi2合金凝固组织的影响.与常压下凝固的典型共晶组织不同，高压条件下的凝固组织为初生ε相树枝晶加离异共晶.高压下凝固组织的变化主要是与压力对相图的影响和对凝固过程中溶质原子扩散的影响有关.通过引入压力参量，推导了高压凝固过程中的成分过冷判据，并应用该判据分析了高压凝固树枝晶组织的形成机理. 关键词： 高压 凝固 FeSi2     

高温高压下钼的结构稳定性研究

以钼为代表的一系列过渡金属,在高温高压的相变及结构稳定性研究是实验和理论研究的热点.钼在常温常压下是bcc结构,但是在高温高压下可能的相结构一直未能确定.本文首先预测了几种高压下的结构,并计算了其自由能及力学性质.针对可能的hcp结构,我们通过新近发展的自洽晶格动力学方法,充分考虑声子间相互作用,成功获得了hcp结构高温高压声子色散曲线,结果表明hcp相在热力学及动力学上都是能够稳定存在的结构,是一种可能的高压相.     

高压下富氢高温超导体的研究进展

近年来,高压强极端条件下的富氢化合物成为高温超导体研究的热点目标材料体系.该领域目前取得了两个标志性重要进展,先后发现了共价型H3S富氢超导体(Tc=200 K)和以LaH10(Tc=260 K,–13℃),YH6,YH9等为代表的一类氢笼合物结构的离子型富氢超导体,先后刷新了超导温度的新纪录.这些研究工作燃发了人们在高压下富氢化合物中发现室温超导体的希望.本文重点介绍高压下富氢高温超导体的相关研究进展,讨论富氢化合物产生高温超导电性的物理机理,展望未来在富氢化合物中发现室温超导体的可能性并提出多元富氢化合物候选体系.     

高压下钙钛矿结构MgSiO3的分子动力学研究

利用分子动力学方法,研究了高温高压下钙钛矿结构MgSiO3的状态方程.研究表明,分子动力学模拟结果很好地再现了广泛温度和压强范围内钙钛矿结构MgSiO3的摩尔体积.温度300 K压强上升到120 GPa模拟的钙钛矿结构MgSiO3状态方程和有效的实验结果基本一致.在更高温度和更高压强下模拟的钙钛矿结构MgSiO3状态方程和他人的计算值吻合的很好.另外,还分别计算了温度300 K,900 K,1500 K和2500 K压强上升到120 GPa时MgSiO3的体积压缩率.     

布里奇曼对高压物理学的研究

简述了布里奇曼的生平,回顾了他在高压实验技术和高压物理学领域中的贡献,强调了他在研究中善于抓住机遇,自己动手,作风严谨的风格.     

Density measurements of non-crystalline materials under high pressure and high temperature

Abstract

We have developed a new method for density measurements by means of X-ray absorption under high pressure and high temperature using a multi-anvil apparatus combined with a synchrotron-radiation source. To overcome the effect of the variation of the sample thickness under pressure, a sapphire ball was put in the sample capsule as a calibrant of the thickness, and the intensity of the transmitted X-ray beam was measured as a function of the sample position. The densities of crystalline and liquid tellurium were measured up to 5 GPa and up to 700°C. Discontinuous changes in the density at the Te I-Te 11 transition and at the melting were clearly observed.     

钍基碳化物ThC的高压结构稳定性研究

钍基碳化物ThC是重要的核材料,基于第一性原理计算,我们研究了ThC的结构稳定性及相变.声子色散曲线表明基态结构的晶格能够稳定到42 GPa附近,当压力继续升高时虚频的出现表明了动力学的不稳定.经比较基态Fm-3m及高压相Pnma结构的自由能,发现零温下,相变压力为22.4 GPa,符合声子色散曲线的结果,同时预测了两种结构的相变边界.     

InSe的高压电输运性质研究

高压下对InSe样品进行原位电阻率和霍尔效应测量. 电阻率测量结果显示, 样品在5–6 GPa区间呈现金属特性, 在12 GPa 的压力下发生由斜六方体层状结构到立方岩盐矿的结构相变, 且具有金属特性. 霍尔效应测量结果显示, 样品在6.6 GPa由p型半导体转变成n型半导体, 电阻率随着压力的升高而逐渐下降是由于载流子浓度升高引起的. 关键词： InSe 高压 电阻率 霍尔效应     

钙钛矿CaTiO3的超高压结构研究

利用同步辐射x射线衍射和 DAC 高压技术在室温下测量了钙钛矿CaTiO₃在压力0—44.53 GPa下的结构变化.结果表明，随着压力的增加CaTiO₃的三个晶轴都受到不同程度的压缩，a,b的压缩率相近且相对比较大，c的压缩率最小，但没有证据表明有相变的发生.在压力范围内CaTiO₃的P-V关系用Murnaghan状态方程表示，设定K′0=4，得到V0=0.2245(6)nm3和K0=222(9) GPa.应用赝立方角γpc与压力的关系，初 关键词： 3')" href="#">CaTiO₃ 结构 超高压 状态方程     

Synthesis and superconductivity in yttrium superhydrides under high pressure

Flourishing rare earth superhydrides are a class of recently discovered materials that exhibit near-room-temperature superconductivity at high pressures, ushering in a new era of superconductivity research at high pressures. Yttrium superhydrides drew the most attention among these superhydrides due to their abundance of stoichiometries and excellent superconductivities. Here, we carried out a comprehensive study of yttrium superhydrides in a wide pressure range of 140 GPa—300 GPa. We successfully synthesized a series of superhydrides with the compositions of YH₄, YH₆, YH₇, and YH₉, and reported superconducting transition temperatures of 82 K at 167 GPa, 218 K at 165 GPa, 29 K at 162 GPa, and 230 K at 300 GPa, respectively, as evidenced by sharp drops in resistance. The structure and superconductivity of YH₄ were taken as a representative example and were also examined using x-ray diffraction measurements and the superconductivity suppression under external magnetic fields, respectively. Clathrate YH₁₀, a candidate for room-temperature superconductor, was not synthesized within the study pressure and temperature ranges of up to 300 GPa and 2000 K. The current study established a detailed foundation for future research into room-temperature superconductors in polynary yttrium-based superhydrides.