Wild-type and molten globular chorismate mutase achieve comparable catalytic rates using very different enthalpy/entropy compensations

The origin of the catalytic power of enzymes with a meta-stable native state,e.g.molten globular state,is an unsolved challenging issue in biochemistry.To help understand the possible differences between this special class of enzymes and the typical ones,we report here computer simulations of the catalysis of both the well-folded wild-type and the molten globular mutant of chorismate mutase.Using the ab initio quantum mechanical/molecular mechanical minimum free-energy path method,we determined the height of reaction barriers that are in good agreement with experimental measurements.Enzyme-substrate interactions were analyzed in detail to identify factors contributing to catalysis.Computed angular order parameters of backbone N–H bonds and side-chain methyl groups suggested site-specific,non-uniform rigidity changes of the enzymes during catalysis.The change of conformational entropy from the ground state to the transition state revealed distinctly contrasting entropy/enthalpy compensations in the dimeric wild-type enzyme and its molten globular monomeric variant.A unique catalytic strategy was suggested for enzymes that are natively molten globules:some may possess large conformational flexibility to provide strong electrostatic interactions to stabilize the transition state of the substrate and compensate for the entropy loss in the transition state.The equilibrium conformational dynamics in the reactant state were analyzed to quantify their contributions to the structural transitions enzymes needed to reach the transition states.The results suggest that large-scale conformational dynamics make important catalytic contributions to sampling conformational regions in favor of binding the transition state of substrate.

Synthesis of Cardanol Sulfonate Gemini Surfactant and Enthalpy-Entropy Compensation of Micellization in Aqueous Solutions

A novel cardanol sulfonate Gemini surfactant with high surface properties was synthesized by cashew phenol, 1,3-dibromopropane and chlorosulfonic acid through three steps procedure of etherification, sulfonation and neutralization. A surface tension method was employed to investigate the thermo-dynamic properties of micellization in aqueous solution for cardanol sulfonate Gemini surfactant synthesized in laboratory. As a result, the micellization of cardanol sulfonate Gemini surfactant in aqueous solutions is spontaneous and entropy-driven. The micellization process is enthalpy-entropy compensated with the compensation temperature (Tc) of 308 ± 1 K.

A Statistical Examination on the Compensation between the Enthalpies and Entropies Obtained from the Calorimetric Methods

The validity of the compensation between the enthalpies and entropies obtained from the calorimetric methods was statistically examined for the first time based on computer simulations. It turned out that several claimed enthalpy-entropy compensations in literature based upon the calorimetric measurements were statistically correct. Interestingly, a linear relationship between the slopes and correlation coefficients of the T DeltaS-DeltaH plots of different physical origin of the compensation behavior.

DETERMINATION OF THE ENTROPY CHANGE FOR ELECTRODE REACTION AND DILUTE ENTHALPY OF SOME IONS BY THERMO-ELETROCHEMICAL TECHNOLOGY

Based on thermoelectrochemical equation for an electrode reaction, the entropy change of it can be obtained by the thermoelectrochemical technology(TECT). The entropy changes of Fe(CN)-36/Fe(CN)-46,H+/H2(P0), Cu+2/Cu and Zn+2/Zn electrode reaction systems and the dilute enthalpies of the H+, Cu2+ and Zn2+ ions under the ion concentrations studied have been determined by a specially designed thermoelectrochemical equipment. The enthalpy change and entropy change for the five systems at unlimitedly diluted concentrations agree well with the literature.

Vapor Pressure, Vaporization Enthalpy, Standard Enthalpy of Formation and Standard Entropy of n-Butyl Carbamate

The vapor pressures of n-butyl carbamate were measured in the temperature range from 372.37 K to 479.27 K and fitted with Antoine equation. The compressibility factor of the vapor was calculated with the Virial equation and the second virial coefficient was determined by the Vetere model. Then the standard enthalpy of vaporization for n-butyl carbamate was estimated. The heat capacity was measured for the solid state(299.39–324.2 K) and liquid state(336.65–453.21 K) by means of adiabatic calorimeter. The standard enthalpy of formation ΔfH[crystal(cr),298.15 K] and standard entropy S(crystal,298.15 K) of the substance were calculated on the basis of the gas-phase standard enthalpy of formation ΔfH(g,298.15 K)and gas-phase standard entropy S(g,298.15 K), which were estimated by the Benson method. The results are acceptable, validated by a thermochemical cycle.

Research of Velocity Compensation Method Based on Range Profile Feature

In this paper,based on the feature of high resolution one-dimensional range profile,two effective motion compensation methods are presented. Firstly,the processing method of stepped-frequency and the response of target moving to range profile are analyzed. Secondly,the function of range profile entropy and range profile contrast are presented for velocity compensation,and then the theory analysis,math model,and solution method are analyzed in detail. Finally,several simulation experiments are designed to prove the accuracy and effectiveness of these two methods. From the final theory analysis and simulation experiments,the conclusion can be drawn that these two methods are effective,which can get much higher velocity estimation accuracy,well real-time and easy to be used in project application. After motion compens-ation,the high resolution one-dimensional range profile will be much better than that used to be,and is used for the detection, recognition and ranging of moving targets.

Moderate point: Balanced entropy and enthalpy contributions in soft matter

Various soft materials share some common features, such as significant entropic effect, large fluctuations, sensitivity to thermodynamic conditions, and mesoscopic characteristic spatial and temporal scales. However, no quantitative defini- tions have yet been provided for soft matter, and the intrinsic mechanisms leading to their common features are unclear. In this work, from the viewpoint of statistical mechanics, we show that soft matter works in the vicinity of a specific thermo- dynamic state named moderate point, at which entropy and enthalpy contributions among substates along a certain order parameter are well balanced or have a minimal difference. Around the moderate point, the order parameter fluctuation, the associated response function, and the spatial correlation length maximize, which explains the large fluctuation, the sensitivity to thermodynamic conditions, and mesoscopic spatial and temporal scales of soft matter, respectively. Possible applications to switching chemical bonds or allosteric biomachines determining their best working temperatures are also briefly discussed.

Entropy and enthalpy for triggering cutaneous erythema

The molar entropy(OS)and molar enthalpy(△H)for the denaturation event that triggers cutaneous erythema was determined to be △S=190J/(mole K)and△H=146.9×10^(3) J/mole.The experiment involved placing heated water against the skin of the forearm,for a range of termperatures and exposure times.Exposing the skin to 45℃ for 22 s was at the threshold for producing erythema,which was similar to the threshold for a slight degree of pain.

跨省流域横向生态补偿政策与绿色经济发展——基于中国县域面板数据的经验研究

跨省流域横向生态补偿政策是解决流域跨界污染问题的重要手段,其对绿色经济发展的影响备受关注。本文运用熵权法测度2003—2019年中国县域绿色经济发展水平,并以9个跨省流域横向生态补偿政策试点为准自然实验,采取渐进双重差分法探究跨省流域横向生态补偿政策对试点地区绿色经济发展水平的影响。研究发现:实施跨省流域横向生态补偿政策对于试点地区的绿色经济发展具有显著的促进作用;跨省流域横向生态补偿政策能够通过减少能源消耗量和提升创业活跃度提升试点地区的绿色经济发展水平;相较于位于流域下游和东部省份的地区,对于位于流域上游和中西部省份的地区,跨省流域横向生态补偿政策在提升绿色经济发展水平方面的效果更为显著;绿色经济发展水平提高的主要来源为污染减排效应的提升,而经济增长效应的提升仅出现在上游地区。

Formation condition of solid solution type high-entropy alloy

Formation condition of high-entropy alloys with solid solution structure was investigated. Seventeen kinds of the high-entropy alloys with different components were prepared, the influencing factors （the comprehensive atomic radius difference δ, the mixing enthalpy AH and the mixing entropy AS） of phase composition of the alloys were calculated, and the microstructure and phase compositions of alloys were analyzed by using SEM and XRD. The result shows that only the systems with δ≤2.77 and △H≥-8.8 kJ/mol will form high entropy alloy with simple solid solution. Otherwise, intermetallic compounds will exist in the alloys. So, selection of the type of element has important effects on microstructure and properties of high entropy alloys.

负焓合金化设计获得高强韧材料

高熵合金是近年来发展的一种新型合金体系,具有较大的晶格畸变特征,展示出了高强度、高硬度、高耐磨性等力学特性。高熵合金通常呈现出高熵驱动的理想随机固溶体结构。因此,类似于传统金属及合金材料,缺乏调控位错等塑性变形载体的能力,高熵合金的强度与韧性之间依旧存在倒置矛盾关系。根据Gibbs自由能理论,混合焓是调控材料显微结构与力学性能的另一个抓手,其完全独立于混合熵并且与其相互竞争。然而,利用混合焓调控材料微观结构及力学性能在国际领域基本属于空白。课题组通过对系列高熵合金研究结果的梳理与总结,并结合对材料热力学与电子显微学的认识,阐明了混合焓对材料显微结构与力学性能的影响机制。本文综述了课题组针对材料混合焓-微观结构-力学性能相关性的研究工作,揭示了负混合焓是局部化学有序及成分波动等异质结构形成的本质原因,阐明了负焓合金的强韧化机理,探索了负焓强韧化合金设计路线,建立了混合焓、显微结构与力学性能的内在联系。负焓合金化设计理念不仅为高强韧合金设计提供了范例、更有助于发展先进结构材料新体系,同时也为传统材料的合金化设计提供数据支撑和理论支持。

化工尾气提浓碳源气相态实验测定和热力学预测模型研究

化工厂提浓CO_(2)尾气是吉林油田注CO_(2)驱油主要气源,掌握提浓碳源气相态性质是设定后续注气工艺参数的基础。本文首先测定了吉林油田周边三个大型化工厂提浓碳源气在273~333 K、0.5~33 MPa范围内的相态性质,掌握了碳源气泡/露点条件、两相区宽度、偏差因子的变化规律和程度。以实验结果为基础,修正SRK状态方程引力相参数和构建CO_(2)与其余组分之间二元交互作用关联性,建立了碳源气压缩因子热力学预测模型,模拟值和实验值相对偏差小于2.5%。进一步结合建立的单组分热熔计算关联式,计算获得了各碳源气的焓和熵值,掌握了其变化规律。本文为碳源气的后续应用提供了重要基础数据和理论支撑。

具有BCC或FCC晶体结构的固溶体高熵合金设计

高熵合金最初报道于21世纪初期,该类合金具有较高的混合熵值,使其具有优异的热稳定性;较大的晶格畸变,产生了强烈固溶强化效果;较大的负焓值导致在晶粒内部形成团簇结构,有效阻碍了位错运动,进一步提高了合金强度。高熵合金独有的这些特性,使其在低温和高温条件下均有望表现出优异的物理性能和力学性能,引起了广泛的关注,研究报道呈爆发性增长。本文根据已有的BCC和FCC结构高熵合金物理-力学性能数据,分析了电子浓度、晶格常数、原子错配度、混合焓、硬度、弹性模量和归一化硬度等参数之间的关系,提出了BCC和FCC晶体结构的高熵合金弹性模量和硬度的经验计算公式,在此基础之上,综合考虑合金密度、塑性和服役工况等条件,提出了BCC和FCC结构的高熵合金成分设计方法。最后指出高熵合金的持久性能、大尺寸铸锭的成分和性能均匀性以及大尺寸合金锭的制备是高熵合金工程应用需解决的关键问题。

生态系统调节服务价值的熵增曲面模型横向补偿方法研究

横向补偿通常多限于单要素或功能的生态系统服务补偿,如何向调节服务功能贡献区实施多要素综合补偿,仍缺少有效解决方法。本研究基于最大熵增理论本研究提出了“熵增曲面法”,构建调节服务价值扩散的曲面模型。此模型更符合生态系统物质能量流动特点,视调节服务价值为有形的正态分布曲面,曲面动态稳定的扩展状态表达了价值的对外输出。本文以梁子湖流域为例,先利用当量因子法计算出研究区各区的生态调节价值,再用上述方法对区域间调节服务价值补偿问题进行分析,并讨论了考虑环境激励的补偿优化办法。结果显示,研究区内武汉市东湖高新技术开发区(e区)应支付给武汉市江夏区(a区)、鄂州市梁子湖区(b区)、咸宁市咸安区(c区)和大冶市金牛镇(d区),分别为303.8万元、1866.6万元、582.4万元、615.2万元,共3368.0万元。该方法能明确“谁补谁、补什么、补多少”的补偿问题,对邻近区域性的调节服务补偿均可展开分析,为多要素、综合性、系统化的生态补偿方向提供了新的思路。

天基逆合成孔径雷达脉内脉间运动补偿及高分辨成像

近年来,太空态势感知在军用和民用领域都得到了越来越多的关注。天基逆合成孔径雷达(SBISAR)能够实现对空间目标的高分辨成像,支撑部件提取、姿态估计、类型识别等后续任务,是太空态势感知的重要工具。然而,在SBISAR成像场景下,平台与空间机动目标间存在复杂的相对高速运动,传统距离-多普勒成像方法不再适用,必须进行运动补偿。本文针对高速径向速度下传统“停—走—停”模型失效、长相干积累时间内目标转速不一致的两个典型误差来源,分别设计了脉内运动及脉间运动补偿算法。首先,建立SBISAR成像的信号模型。然后,基于最小熵准则构建参数估计代价函数,通过估计目标对应回波信号的调频率,构造补偿项进而实现脉内补偿。同时,建立图像熵代价函数,在估计转动参数后,完成对目标转动的空变相位补偿。所提算法有效解决了天基高速机动背景下传统距离-多普勒成像方法的距离像展宽、方位散焦问题,实现了SBISAR对空间目标的高分辨成像。通过基于仿真数据的实验分析,验证了所提算法的有效性。

环境关注对居民森林生态补偿参与意愿的影响——基于安图县的调研数据

阐述了国家重点森林生态功能区中的当地居民是生态保护的最终实施者,也是生态补偿成效的直接受益者。研究了居民的环境关注通过心理变量对生态保护意愿的影响,及其对提升生态保护补偿效果具有的重要意义。基于安图县下辖7个镇、2个乡的967份有效调查问卷,在分析居民生态保护补偿意愿及影响机制的基础上,在传统计划行为理论中加入了环境关注这一前因变量,选用熵值法和多元线性回归分析模型为研究方法展开分析。实证研究结果表明:(1)环境关注与行为态度、主观规范和感知行为控制三个心理变量的正相关关系显著;(2)行为态度、主观规范、感知行为控制三个心理变量与居民生态保护意愿的正相关关系显著,其中主观规范对居民生态保护意愿的影响最为显著。据此,从加强生态保护补偿理念的宣传、制定合理的生态补偿政策两个方面提出提升安图县居民生态补偿参与意愿的建议。

基于熵权TOPSIS的流域生态补偿政策绩效评价——以黄山市为例

流域生态补偿政策是兼顾生态保护与经济发展的一项重要举措,科学评价流域生态补偿政策绩效对进一步完善、推广流域生态补偿政策具有重要意义。采用熵权TOPSIS评价2012—2021年黄山市生态补偿政策绩效水平,并利用障碍度模型探究影响黄山市生态补偿政策绩效水平的主要障碍因子。结果表明:(1)黄山市生态补偿政策综合绩效水平由0.301上升到0.665,整体呈现上升趋势,从较差水平提升至良好水平。(2)黄山市生态补偿政策实施对生态、经济和社会的影响程度不尽相同,经济绩效、社会绩效、生态绩效年均增长分别为0.071、0.036、0.032。(3)影响黄山市生态补偿政策绩效水平的主要障碍因子是工业废水中化学需氧量、工业废水排放量和人均GDP等,各障碍因子对流域生态补偿政策绩效的约束作用存在显著差异。

基于多种模型融合的电能计量互感器误差自动化补偿方法

为电能精准计量提供保障,提出基于多种模型融合的电能计量互感器误差自动化补偿方法。获取影响电能计量互感器误差的关键特征数据,作为改进LSTM与SVR输入,得到对应子模型的预测输出,计算子模型的权重系数,通过平均加权法融合模型的预测结果,确定电能计量互感器运行数据预测值,利用自回归积分滑动平均模型实现电能计量互感器误差的动态补偿。实验结果表明,特征数据选择可有效降低电能计量互感器比差和角差波动幅度;误差补偿后的二次电压曲线平滑,且更加接近理想的正弦波形。

新的理想气体焓、熵计算公式

ISO 20765-1:2005“Natural gas-Calculation of thermodynamic properties-Part 1:Gas phase properties for transmission and distribution applications”(GB/T 30491.1-2014《天然气热力学性质计算第1部分:输配气中的气相性质》)是以AGA8方程为基础计算管输天然气热力学性质,根据亥姆霍兹自由能及其关于温度和密度的导出函数来求解,推导严格。但是,标准中的计算公式仍然有些复杂,不容易理解,并且没有明确给出理想气体焓、熵的计算公式;经过研究,利用ISO 20765-1(GB/T 30491.1)中的数据,提出了6个计算理想气体焓、熵的新公式。新公式经过严格的数学推导,是带有双曲函数和指数函数的多项式,使用简单,精确度高,其相对误差平均值小于3×10^(-5)。

Enthalpy-entropy compensation in protein unfolding

Enthalpy-entropy compensation was found to be a universal law in protein unfolding based on over 3 000 experimental data. Water molecular reorganization accompanying the protein unfolding was suggested as the origin-of the enthalpy-entropy compensation in protein unfolding. It is indicated that the enthalpy-entropy compensation constitutes the physical foundation that satisfies the biological need of the small free energy changes in protein unfolding, without the sacrifice of the bio-diversity of proteins. The enthalpy-entropy compensation theory proposed herein also provides valuable insights into the Privalov’s puzzle of enthalpy and entropy convergence in protein unfolding.