Thermodynamic Properties of Alanylpeptide Buffer Systems and Their Potential as Standards in Biological Applications

The second dissociation constants pK ₂of the NH₃ ⁺charge center of the alanylpeptides, alanylglutamine (Ala–Gln), alanylleucine (Ala–Leu), alanylglycine (Ala–Gly), and DL-alanyl–DL-methionine (DL-Ala–DL-Met) were determined at ten temperatures in the range, 5–50°C. These pK ₂values were calculated from the emf of cells containing buffer solutions of these dipeptides. A cell of the type described by Harned and Ehlers,⁽¹⁾utilizing hydrogen and silver–silver bromide electrodes was used. The thermodynamic quantities, H^o, S^o, and C_p ^owere derived from the temperature coefficients of the dissociation constants. The pK ₂values at 25°C, 8.2105 ( Ala–Gln), 8.2668 ( Ala–Leu), 8.2940 ( Ala–Gly), and 8.3054 ( DL-Ala–DL-Met). These values show that different substituent groups on the -carbon atom (which include polar and nonpolar groups), have a small effect on the dissociation of the NH₃ ⁺charge center. These compounds were also found to be suitable as buffers in the pH range(7–9). The thermodynamics of the solute–solvent interaction is interpreted in terms of the mixture model.⁽²⁾     

化学跑合对齿轮胶合的影响

选用了３ 种跑合剂在ＣＬ－１００ 型齿轮试验机上进行满载跑合能力对比试验和齿轮抗胶合载荷级对比试验．结果表明：材质为４５＃ 钢的试验齿轮副和材质为２０ＣｒＭｎＴｉ钢的试验齿轮副用含磨料跑合剂进行１ 次满载跑合试验时,发生严重胶合;而采用化学跑合剂可以实现１ 次满载跑合,且用化学跑合剂跑合后的齿面比用普通油跑合后的齿面抗胶合能力提高１ 个载荷级,显示化学跑合剂在齿轮中的应用很有潜力．     

Skellam Type Processes of Order k and Beyond

In this article, we introduce the Skellam process of order k and its running average. We also discuss the time-changed Skellam process of order k. In particular, we discuss the space-fractional Skellam process and tempered space-fractional Skellam process via time changes in Skellam process by independent stable subordinator and tempered stable subordinator, respectively. We derive the marginal probabilities, Lévy measures, governing difference-differential equations of the introduced processes. Our results generalize the Skellam process and running average of Poisson process in several directions.     

Running Coupling Constants in N-N Interaction

The scalar and vector running coupling constants are derived using the renormalization group method in the σ-ω model. The numerical values of the two running coupling constants are obtained and the physical meaning of the result is discussed.     

Additive mappings that do not increase minimal rank of alternate matrices

Additive mappings, which do not increase the minimal rank of alternate matrices, are completely classified. No condition is imposed on the underlying field.     

欧姆电源逻辑无环流仿真分析及其运行

介绍了HL-2A装置欧姆加热电源逻辑无环流运行的基本原理和实现步骤。通过对系统的理论分析和仿真,提出了正组变流器逆变可靠运行的控制方案。对出现环流以后的控制策略进行了探讨,实验结果验证了分析的正确性。     

聚醚醚酮链段连接方式与其性能关系的研究

利用亲核取代反应,通过缩聚法合成了一种新型聚芳醚酮50％交替共聚物PEDEK-PETMDEK,通过¹HNMR证明其具有预期的结构.通过考察50％无规共聚物、50％交替共聚物、均聚物PEDEK和PET-MDEK的溶解性和热性能,发现聚醚醚酮共聚物的链段连接方式对聚合物性能有很大影响.50％交替共聚物是一种无定形固体,易溶于通常的有机溶剂,而50％无规共聚物却是半结晶聚合物,除浓硫酸外几乎不溶于任何溶剂;50％交替共聚物具有比50％无规共聚物更高的玻璃化转变温度.     

Remarks on the correlation function implied by the Bjerrum theory of ion pairing

The Friedman theory of correlation functions implied by the Bjerrum theory is generalized by taking into account additional terms and by improving the basic expression for the free energy. By combining the mean spherical approximation (MSA) and the mass action law (MAL) good agreement with HNC and MC data is reached.     

On the preparation of simple and universal buffers including polynuclear species

A simple generalized procedure for the calculation of electrolyte concentrations in pH-buffers is proposed. Mixtures of acid-base systems and formation of polynuclear species at high ionic strengths are considered, and a diagram useful for the study and preparation of the buffers is shown.     

动静态气密性分析方法及其在动车组上的应用

随着运行速度的提升, 高速动车组受到的外部激扰愈发剧烈. 尤其是动车组通过隧道和在隧道内交会时, 车体外表面产生的剧烈瞬变压力传入车厢内, 会引起司乘人员耳感不适等问题. 为研究动车组运行过程中的气密性能对车内气压波动和乘客乘坐舒适度的影响关系, 本文采用动静态测试结合的分析方法, 结合时间常数模型和当量泄漏面积模型, 通过在不同车辆内外部布置气压波动监测传感器, 对四级修前后的高速动车组进行了线路运行气动载荷测试; 针对不同部位具体结构特征开发了不同型式的气体泄漏量测试工装, 并对不同车辆的静态气密性进行了测试研究. 搭建了动静态气密性能分析模型并获得了动静态气密指数, 总结了隧道条件、运行速度等因素对车内压力波动和动态气密性能的影响规律, 同时针对典型气密部件的泄漏量和泄漏面积进行了分析, 对气密敏感部件进行了影响度排序并提出了优化方案. 本文提出的方法和相关研究数据对于关键部件的设计方案和修程修制优化具有一定的参考意义.