Structure-activity Relationships of Vasorelaxing Effect of Polyarginine Oligopeptides

Based on the EDRF(endothelium derived relaxing factor)-like effects for polyarginine Arg-Arg-oH was selected as the lead compound and its derivatives Arg-Arg- OCH_3.Arg Arg-Arg-OH,HO-ArgCOCH_2CH_2COArg-OH,HO-ArgCOCH_2COArg-OH,were synthesized.These substances showed on bioassay various degrees of vasorelaxant activities. With protection for the C-terminal of Arg-Arg-OH with a methyl ester.the vasorelaxing ac- tivitv was decreased.In contrast.when the N-terminal of Arg-OH was protected with mal- onic acid or butane diacid.the biological activites were lower than those of Arg-Arg-OH due to the lowered metabolic rate.With protection of N-terminal of Arg-Arg-OH with L-Arg residue.Arg-Arg-Arg-OH was obtained,which showed a vasorelaxing activity better than that of Arg-Arg-OH.The bioactivities observed on the Wister's rats for the former com- pound become the experimental basis for prodrug design of EDRF.

A time domain induced polarization relaxation time spectrum inversion method based on a damping factor and residual correction

Relaxation time spectra （RTS） derived from time domain induced polarization data （TDIP） are helpful to assess oil reservoir pore structures. However, due to the sensitivity to the signal-to-noise ratio （SNR）, the inversion accuracy of the traditional singular value decomposition （SVD） inversion method reduces with a decrease of SNR. In order to enhance the inversion accuracy and improve robustness of the inversion method to the SNR, an improved inversion method, based on damping factor and spectrum component residual correction, is proposed in this study. The numerical inversion results show that the oscillation of the RTS derived from the SVD method increased with a decrease of SNR, which makes it impossible to get accurate inversion components. However, the SNR has little influence on inversion components of the improved method, and the RTS has high inversion accuracy and robustness. Moreover, RTS derived from core sample data is basically in accord with the pore-size distribution curve, and the RTS derived from the actual induced polarization logging data is smooth and continuous, which indicates that the improved method is practicable.

Disorder-enhanced nuclear spin relaxation at Landau level filling factor one

The nuclear spin relaxation rate （l/T1） is measured for GaAs two-dimensional （2D） electron systems in the quantum Hall regime with an all-electrical technique for agitating and probing the nuclear spins. A ＂tilted plateau＂ feature is observed near the Landau level filling factor v = 1 in 1/T1 versus v. Both the width and magnitude of the plateau increase with decreasing electron density. At low temperatures, lIT1 exhibits an Arrhenius temperature dependence within the tilted plateau regime. The extracted energy gaps are up to two orders of magnitude smaller than the corresponding charge transport gaps. These results point to a nontrivial mechanism for the disorder-enhanced nuclear spin relaxation, in which microscopic inhomogeneities play a key role for the low energy spin excitations related to skyrmions.

Effect of ocean environmental factors on sound absorption by boric acid relaxation in sea water

By using the expressions for the maximum absorption per wavelength (αλ),and the relaxation frequency fr of the boric acid relaxation derived previously by the author and employing the related oceanographic literatures, the effects of pressure, temperature, pH and salinity on (αλ)r and ∫r of the boric acid relaxation in sea water have been estimated. Results show that ( αλ), not only increases with pH but also increases approximately linearly with pressure and temperature, and is nearly proportional to the 1. 35 power of salinity. However, pressure, pH and salinity have negligible effect on ∫r; therefore, ∫r, can be approximately expressed as a function of temperature only. Comparisons of the predicted with the measured ( αλ)r and ∫r in different ocean areas are given.

Endothelium derived relaxation factors reduce sulfur dioxide-induced aortic relaxation

The endothelium plays a key role in the control of vascular patency and tone. Thus, the main objective of the study was to determine the role of endothelium and its derived relaxation factors in mediating relaxation of rat thoracic aorta, in response to sulfur dioxide (SO2) derivatives “1:3 M/M sodium bisulfite (NaHSO3) and sodium sulfite (Na2SO3)” using PowerLab tissue bath system. Endothelial denudation enhanced relaxation responses of SO2 derivatives with an IC50 of 6.11 mM as compared to control rings with an IC50 of 6.21 mM, as well as the maximum relaxation (Emax) was increased from 62.026% ± 6.527% to 83.13% ± 14.755%. Furthermore, the relaxation responses to SO2 derivatives in aortic rings were significantly enhanced by indomethacin, clotrimazole and methylene blue with IC50’s of 4.8 mM, 5.33 mM and 4.01 mM, and Emax were raised to 101.1% ± 6.537%, 66.92 ± 7.538 and 104.68 ± 3.575, respectively. Meanwhile, L-NAME did not alter dose-dependent relaxation of SO2 derivatives in comparison to control aortic rings. The results of this study had shown that endothelium denudation and blocking of endothelium derived-relaxation factors enhanced vasodilator effect of SO2;this may clarify the role of endothelium in the vasodilatory mechanism of SO2.

Human umbilical cord blood-derived stem cells and brain-derived neurotrophic factor protect injured optic nerve:viscoelasticity characterization

The optic nerve is a viscoelastic solid-like biomaterial.Its normal stress relaxation and creep properties enable the nerve to resist constant strain and protect it from injury.We hypothesized that stress relaxation and creep properties of the optic nerve change after injury.Moreover,human brain-derived neurotrophic factor or umbilical cord blood-derived stem cells may restore these changes to normal.To validate this hypothesis,a rabbit model of optic nerve injury was established using a clamp approach.At 7 days after injury,the vitreous body received a one-time injection of 50 μg human brain-derived neurotrophic factor or 1 × 106 human umbilical cord blood-derived stem cells.At 30 days after injury,stress relaxation and creep properties of the optic nerve that received treatment had recovered greatly,with pathological changes in the injured optic nerve also noticeably improved.These results suggest that human brain-derived neurotrophic factor or umbilical cord blood-derived stem cell intervention promotes viscoelasticity recovery of injured optic nerves,and thereby contributes to nerve recovery.

A branch-and-bound algorithm for discrete multi-factor portfolio optimization model

In this paper, a new branch-and-bound algorithm based on the Lagrangian dual relaxation and continuous relaxation is proposed for discrete multi-factor portfolio selection model with roundlot restriction in financial optimization. This discrete portfolio model is of integer quadratic programming problems. The separable structure of the model is investigated by using Lagrangian relaxation and dual search. Computational results show that the algorithm is capable of solving real-world portfolio problems with data from US stock market and randomly generated test problems with up to 120 securities.

Role of testosterone in NO/EDRF-induced relaxation of the rabbit aorta

To determine whether the therapeutic effectiveness of testosterone in male elderly coronary heart disease patients is related to the production of nitric oxide (NO), which accounts for the biological activity of endothelium derived relaxing factor (EDRF), we studied the regulatory effect of testosterone on production of NO/EDRF in the aorta and cultured vascular endothelial cells. The production of NO/EDRF was detected by the stimulation of cGMP formation in rabbit fetal lung-6 cells. The results showed that testosterone stimulated the production of NO/EDRF in both the aorta and cultured vascular endothelial cells, suggesting that NO/EDRF-dependent vasodilation is one of the mechanism by which testosterone alleviates angina pectoris and improves myocardial ischemia in elderly male coronary heart disease patients.

基于净能力及二阶锥规划的分布式光储多场景协同优化策略

针对现有配电网中分布式光储调度模型存在资源协同不足、求解复杂等问题,提出了一种基于净能力及二阶锥规划的分布式光储多场景协同优化调度策略。通过引入储能接入配电网后的功率转移分布因子,提出一种基于系统净能力的储能最优选址计算方法;综合考虑储能的运行特性和分布式光伏的出力不确定性,建立以系统日综合成本和削峰填谷为目标的分布式光储多场景协同优化调度模型;利用二阶锥松弛和Big-M法对潮流约束、储能运行约束进行处理,将原规划模型转化为混合整数二阶锥规划问题。以IEEE 33节点系统和西北某实际系统为算例进行仿真分析,结果表明所提方法能在降低负荷峰谷差和日综合成本、平抑负荷波动的同时,显著提高对分布式光伏的消纳能力,验证了所提方法的有效性和可行性。

无机玻璃结构弛豫及影响因素综述

本文介绍了玻璃结构弛豫的假想温度与弛豫动力学理论,并阐述了这些理论的建立、发展及研究现状。假想温度理论重点关注玻璃热历史,给出了玻璃结构弛豫进展方向与快慢的热力学判据;弛豫动力学则重点关注玻璃化转变现象,揭示了玻璃结构弛豫的微观机制与演变过程。热历史、玻璃成分、杂质缺陷、温度等是影响无机玻璃结构弛豫的关键因素,也是玻璃生产与应用过程中的重要切入点。目前,玻璃结构弛豫理论发展较为完善,但复杂体系无机玻璃结构弛豫的试验研究依然存在诸多空白,具体微观机制有待进一步完善,并且微晶玻璃和玻璃基复合材料的结构弛豫还未受到广泛关注,此类“瓶颈”问题的突破有望支撑无机玻璃材料在更为严苛的应用环境中长期安全服役。

用于大规模MIMO系统的改进自适应SOR检测算法

大规模多输入多输出(Multiple-Input Multiple-Output,MIMO)系统由于具备较多的天线数,会导致传统线性信号检测算法如最小均方误差(Minimum Mean Square Error,MMSE)的复杂度过高。针对以上问题,提出了F修正的自适应超松弛迭代(F-corrected Adaptive Successive over Relaxation,FA-SOR)检测算法。该算法首先利用超松弛迭代(Successive over Relaxation,SOR)算法避免高阶矩阵求逆运算,降低复杂度;其次使用F修正的公式自动更新SOR算法迭代使用的松弛参数,同时优化迭代的公式与初始解来加快收敛速度。仿真结果表明,不论在理想独立信道还是相关信道下,相比于现有的自适应SOR算法,FA-SOR都能以更低的复杂度达到更低的误码率,同时逼近MMSE算法的性能。

基于IRC法和局部放电法的车载高压电缆绝缘状态评估

为准确评估乙丙橡胶(EPDM)车载电缆的绝缘老化状态,引用了等温松弛电流(IRC)法和局部放电(PD)法,分别讨论了老化因子、局部放电特征信息与电缆老化状态之间的映射关系,结果表明:随着车载电缆运行里程的增加,老化因子、局部放电量、放电次数和放电电流均呈现规律性增长趋势,多种老化应力协同作用是造成车载电缆绝缘劣化的主要原因,绝缘材料内部陷阱的增多和加深是车载电缆老化的微观表现。协同等温松弛电流法和局部放电法对车载电缆绝缘状态的评估具有有效性和可行性,通过建立微观陷阱分布特性与宏观局部放电特性之间的联系,分析可得:深陷阱捕获电荷的能力较强,电荷极易集聚,局部放电容易发生,因此基于IRC法和局部放电法对车载电缆绝缘状态进行评估具有一定的价值意义,可指导高速动车组电网规划及电缆检修工作。

Endothelium-derived Relaxing Factor Activates Calcium-activated Potassium Channels of Resistance Vessel Smooth Muscle Cells

Direct observation was made by using the patch-clamp technique with a specially designed microperfusion system to investigate the effect of acetylcholine (Ach 10^(-6) mol/L) elicited endothelium-derived relaxing factor (EDRF) on the calcium-activated potassium channel (IK(Ca))in the smooth muscle cells of mesenteric resistance vessels in Wistar rats. Activation of IK(Ca) was firstly observed by inducing the elicited EDRF or sodium nitroprusside (SNP 10^(-8) mol/L) under various clamping voltages in cell-attached configuration. While the pipette solution contained KCl 126 mmol/L and the bath solution contained KCl 5.9 mmol/L, two types of conductances of calcium-activated potassium current being 76.4±2.3 pS(mean±S.E. n = 7) and 160.3±7.5 pS (mean±S.E. n= 7) were recorded during the EDRF activation, one type of conductance being 100.5±2.8 pS (mean±S.E. n = 6) was activated by nitric oxide (NO) which is an effective component from SNP. Differences in kinetic characteristics of these channels between EDRF and NO activation were found, particularly the probability of the channel being open in EDRF activation was obviously greater than that in NO stimulation. It has been shown that the potassium channel mechanisms involved in the EDRF and NO actions might be different.

基于违反程度的协同优化方法研究及应用

针对多学科协同优化算法计算量大、收敛速度缓慢、动态松弛因子失效问题,提出了基于系统级设计变量违反程度改进的动态松弛因子,使松弛因子里的系统级搜索范围因子不再是定值而是动态变化,并将各子学科原目标函数动态加权一个递减函数,把它们统一加权到子学科现目标函数中,既减小松弛因子失效的可能性,又加深了各子学科之间的独立性。通过算例对改进的算法进行验证,计算结果表明,改进的算法收敛速度快,结果精度也有明显的提高,最后改进的算法应用在轮胎成型鼓上。

Universal basis underlying temperature, pressure and size induced dynamical evolution in metallic glass-forming liquids

The dramatic temperature-dependence of liquids dynamics has attracted considerable scientific interests and efforts in the past decades, but the physics of which remains elusive. In addition to temperature, some other parameters, such as pressure, loading and size, can also tune the liquid dynamics and induce glass transition, which makes the situation more complicated. Here, we performed molecular dynamics simulations for Ni_(50)Zr_(50) bulk liquid and nanodroplet to study the dynamics evolution in the complex multivariate phase space, especially along the isotherm with the change of pressure or droplet size. It is found that the short-time Debye–Waller factor universally determines the long-time relaxation dynamics no matter how the temperature, pressure or size changes. The basic correlation even holds at the local atomic scale. This finding provides general understanding of the microscopic mechanism of dynamic arrest and dynamic heterogeneity.

环境湿度对配电电缆绝缘等温松弛电流的影响

环境湿度是配电电缆绝缘等温松弛电流测试的重要干扰因素之一,对基于松弛电流的绝缘状态评估影响显著。以退役三芯户外终端为试样,测试了不同湿度环境下的等温松弛电流,并开展了绝缘状态评估误差分析。结果表明:在检测系统直流电源输出1 kV电压后,随着环境湿度增加,A、B和C相电缆的等温松弛电流和电缆线芯实际分压均呈现整体快速下降的趋势,这表明等温松弛电流的下降主要与电缆绝缘子伞裙沿面电阻Rh下降相关。A、B和C相电缆等温松弛电流均可通过三阶指数模型模拟,计算出的老化因子A均大于德国判据中“劣化”等级线2.10,且各相A值存在明显区别,这表明其在投后的各相电缆绝缘的老化程度不同,其可能与各相线路的负荷量大小不同导致的绝缘层电热老化进程相关。环境相对湿度在49%以下时,不同湿度等温松弛电流法计算出的老化因子A误差在6%以内,但当湿度进一步提高后,极化电场不足导致老化因子A误差过高,准确性较低,因此在实际应用中应注意环境湿度的影响,建议电缆接头周围的环境相对湿度控制在49%以下。

求解PageRank向量的一种松弛多步分裂迭代方法

基于求解PageRank向量的内外迭代格式,引入一个松弛因子得到一种松弛内外迭代方法。结合已有的多步分裂迭代框架,引入两个不同的松弛因子,提出了求解PageRank向量的松弛多步分裂迭代方法并分析了算法的收敛性。更进一步地,利用松弛内外迭代格式构造了加速投影子空间方法的预处理矩阵,理论分析相关谱分布情况,并给出了松弛多步分裂迭代方法及预处理矩阵中参数的选取准则。几个数值例子验证了松弛多步分裂迭代方法和预处理矩阵的有效性,通过选取合适的松弛因子,与多步分裂迭代方法相比具有更高的运算效率。

低磁场条件下天然气核磁共振特性的实验研究

研究天然气在低磁场条件下的核磁共振弛豫特性及含烃因子的变化对天然气的勘探和开发工作具有重要意义 ,由于受核磁共振仪器耐温、耐压条件的限制 ,这方面的研究工作非常少 ,国内还是空白 .本文在一套自行研制的耐高温、耐高压的低磁场 (磁场强度 0 .0 5 6T)核磁共振设备上 ,对我国大庆油田深层天然气的核磁共振特性进行了实验研究 ,获得了天然气的T1 弛豫时间、含烃因子随温度和压力变化的函数关系 .

提高充型过程数值模拟运算速度的动态超松弛迭代算法

在模拟铝合金压铸件型腔充型过程时 ,采用传统的固定松弛因子ω(0 <ω <2 )不能有效地减少运算中的迭代次数 ,而采用一种提高充型过程数值模拟运算速度的新算法—动态超松弛迭代算法 ,在 0 <ω <2范围内 ,运用自适应计算方法 ,根据运算的迭代次数的增减可以决定松驰因子的增大或减少 ,动态调整松弛因子可使运算中的迭代次数减少。经实际运算检验 ,运用该方法可以大幅度提高运算速度 ,运算的迭代次数减少 2 5 %。

波动性高糖对内皮细胞血管舒张因子合成的影响

目的对比研究波动性与恒定性高糖对血管内皮细胞血管舒张因子合成的影响。方法以体外培养人脐静脉内皮细胞为研究对象,分别测定波动性高浓度葡萄糖(5或20 mmol/L)与恒定性高浓度葡萄糖(20 mmol/L)环境下内皮细胞合成的血管舒张因子前列环素及一氧化氮的含量,同时观察培养液中丙二醛含量的变化。前列环素应用放射免疫法测定其稳定代谢产物,而一氧化氮及丙二醛的检测则分别应用Griess法与Schuh法。结果波动性高糖组前列环素与一氧化氮均明显低于恒定高糖组(分别为21±6 ng/L比36±8 ng/L,P<0.01;13.6±2.0mmol/L比18.2±3.7 mmol/L,P<0.001),而波动性高糖组的丙二醛则明显高于恒定性高糖组(16.5±2.7 mmol/L比13.2±2.2 mmol/L,P<0.05)。结论波动性高血糖较恒定性高血糖对血管内皮细胞可能具有更强的损伤效应。