Complementary freeze fracture replication: An example of its use in the study of horizontal cell gap junctions of the carp retina

Dark-adapted carp retinas were fixed with glutaraldehyde, frozen in liquid nitrogen slush, and their complementary replicas were harvested using a bipolar-vacuum evaporater. On montage pictures, plasmic (PFF) and ectoplasmic fracture faces (EFF) of the external horizontal cells (EHC) were marked, and PFF of gap junction (GJ) areas were scrutinized by virtue of particulate aggregation visible at relatively low magnification. Summation of digitized values obtained from a complementary pair of replicas was taken to represent all existent GJ areas in an examined EHC surface. A similar method was applied to large horizontal processes (LHP) that are located in the inner-most part of the internal nuclear layer and currently accepted to be extensions of EHC. The occurrence of fractured faces of plasma membrane was smaller in EHC than LHP. The percentage of GJ areas was about ten times larger in EHC than LHP. Examining complementary replicas at relatively low magnification appears to be useful for facilitating quantitative analysis of intercellular coupling by GJ structures.     

Time-Dependent Ginzburg–Landau: From Single Particle to Collective Behavior

The Ginzburg–Landau theory of phase transitions is one of the most successful and elegant theories that have a very general applicability to a large variety of phenomena. Moreover, its extension into time domain has produced a wealth of interesting new predictions and applications all the way from materials science to cosmology. Here, we describe applications of time-dependent Ginzburg–Landau theory to conventional superconductors and show that there is a clear-cut transition in the time dependence from single particle to collective behavior as a function temperature.     

丝绸业与中国古代自然科学关系撷零

丝绸业与中国自然科学之间自古就有着非常密切的关系。这是马克思主义的人类的生产活动决定着科学的发生和发展原理的一种具体的体现。——本文是笔者对这一方面的若干问题的一些看法。     

电机定转子片冲模制造公差的取值

本文对电机定转子片冲模制造公差的取值方法进行了对比论证 ,并给出了一种 2 3公差取值的合理方法。     

Distribution of Occurrence Days of Runoff Peaks in Israel and its Shifts for High-Discharge Events

Knowledge of the pattern of occurrence of peak runoff events is valuable for managing activities in watercourses and their environs. Current approaches consider the inter-arrival intervals between events as being exponentially distributed with a fixed seasonal parameter. In a new approach (Ben-Zvi and Meirovich, Stochastic Hydrology and Hydraulics, 1997) the occurrence day is considered as a random variable to whose series a gradually-varied distribution, such as the normal or Pearson III function, can be fitted. The statistical moments of occurrence days facilitate such fits. The present work extends the consideration, via a case study of partial duration series, to the occurrence times of high-discharge events. The first three statistical moments of occurrence days in series of runoff peaks have been determined for a sample of nine hydrometric stations in Israel. The mean occurrence day of high peaks at eight stations falls earlier than that of respective low peaks, whilst for one station the opposite trend is observed. The shifts at five stations are found statistically significant. The standard deviations of occurrence days in partial duration series for the sample stations are mostly shorter than those in the respective complete series of events. The occurrence days of runoff events in the complete series at seven stations are about evenly distributed around their respective mean, whereas most of the other occurrence series are skewed.     

Relations between uncertainty structures in identification for robust control

Various techniques of system identification exist that provide a nominal model and an uncertainty bound. An important question is what the implications are for the particular choice of the structure in which the uncertainty is described when dealing with robust stability/performance analysis of a given controller and when dealing with robust synthesis. It is shown that an amplitude-bounded (circular) uncertainty set can equivalently be described in terms of an additive, Youla parameter and ν-gap uncertainty. As a result, the choice of structure does not matter provided that the identification methods deliver optimal uncertainty sets rather than an uncertainty bound around a prefixed nominal model. Frequency-dependent closed-loop performance functions based on the uncertainty sets are again bounded by circles in the frequency domain, allowing for analytical expressions for worst-case performance and for the evaluation of the consequences of uncertainty for robust design. The results can be used to tune optimal experimental conditions in view of robust control design and in the further development of experiment-based robust control design methods.     

杨凌地区‘媚丽’葡萄的采收期确定

通过比较‘野酿2号’毛葡萄不同采收期葡萄酒的理化指标与香气成分,以期探索‘野酿2号’毛葡萄酒酿造的最适采收期。分别对8月15日、9月10日和9月23日采收的‘野酿2号’毛葡萄酒进行酿造,并测定相关理化指标和香气成分。结果表明,随着采收期的延迟,葡萄中的总糖含量增加,而总酸含量降低;酒中的酒度、单宁、总酚、总类黄酮含量逐渐增加,残糖和总酸含量则逐渐降低,各不同采收期差异显著（P<0.05）。3种毛葡萄酒中共检测到89种香气成分,其中包括22种醇类、37种酯类、7种酸类、5种醛类、5种萜烯类及13种其它物质。9月23日的葡萄酒中香气物质含量最高,为852370.83 μg/L。‘野酿2号’毛葡萄酒的香气特征主要表现为果香味、花香味、焦糖味、化学味和脂肪味等,但不同采收期的毛葡萄酒由于香气成分的香气活性值不同而导致香气特征存在差异。8月15日的毛葡萄酒由于异戊酸、辛酸较高的香气活性值而具有较浓的脂肪味;9月10日的毛葡萄酒则由于苯乙醛、β-大马酮、TDN等较高的香气活性值而具有较浓的花香味和焦糖味;9月23日的毛葡萄酒由于己酸乙酯较高的香气活性值而具有较浓的果香味。从果实品质和毛葡萄酒香气特征分析表明,‘野酿2号’毛葡萄在当地的最佳采收期为9月10日至9月23日。     

读图时代如何构建和谐师生关系

分析了衍生的读图时代的文化因素影响着师生关系,师生关系出现了短暂化、虚化、固定化、庸俗化等现象,试图从中找到读图时代下的和谐师生关系的办法和建议,以加深对师生关系的进一步认识,有助于我们清晰读图时代下各种观念的冲击,明确教育背景,从而更好地发展高等教育。     

Dielectric properties of low molecular weight poly(ethylene glycol)s

This paper reports the measured values of dielectric permittivity ε′ and dielectric loss ε″ of ethylene glycol, diethylene glycol and poly(ethylene glycol)s of average molecular weight 200, 300, 400 and 600 g mol⁻¹ in the pure liquid state. The measurements have been carried out in the frequency range 200 MHz to 20 GHz at four different temperatures of 25, 35, 45 and 55 °C. The complex plane plots (ε″ versus ε′) of these molecules are Cole–Cole arcs. The static dielectric constant ε₀, high‐frequency limiting dielectric constant ε_∞, average relaxation time τ₀ and distribution parameter α have been determined from these plots. The value of the Kirkwood correlation factor g and the dielectric rate free energy of activation ΔF have also been evaluated. The dependence of relaxation time on molecular size and viscosity has been discussed. A comparison has also been made with the dielectric behaviour of these molecules in dilute solutions of non‐polar solvents, which were carried out earlier in this laboratory. The influences of intermolecular hydrogen bonding and molecular chain coiling on the dielectric relaxation of these molecules have been recognized. © 2000 Society of Chemical Industry