Cause Of Hysteresis Research Articles

Synergistic activation by Ca2+ and Mg2+ as the primary cause for hysteresis in the phosphorylase kinase reactions.

A synergistic activation of phosphorylase kinase by Ca2+ plus Mg2+ was found to be the primary cause of the hysteresis, or lag, in the phosphorylase kinase reaction. Preincubation of the enzyme for short times with Ca2+ plus Mg2+ resulted in an approximately 7-fold increase in the kinase activity in subsequent assays with phosphorylase b or phosphorylase kinase as substrates, whereas preincubation with each metal ion by itself had no effect. Maximal activation through preincubation with Ca2+ plus Mg2+ occurred in 1 min 45 s and was readily reversed by chelation of both metal ions. As a result of the activation, the progress curve of phosphorylase b conversion at pH 6.8 was found to be nearly linear. Activation by Ca2+ plus Mg2+ was not apparent when subsequent assays were carried out at pH 8.2, or when previously autophosphorylated enzyme was used. Furthermore, the synergistic activation was found to occur significantly slower and/or to decrease in the presence of ATP, phosphorylase b, beta-glycerophosphate, and inorganic phosphate. How the synergistic activation by Ca2+ plus Mg2+ relates to autophosphorylation and the lag in the phosphorylase kinase reaction is discussed.

The contact angle of water on polystyrene: A study of the cause of hysteresis

1. 1. It is to be expected that the hysteresis of contact angles on polystyrene would be the effect of a number of simultaneous causes. Whatever the interpretation, the differences in the observed angles found with surfaces that had been formed in different ways point to structural differences among the samples; and the existence of structural differences would indicate that all the surfaces depart appreciably from ideality, e.g., from ideal flatness, rigidity, and homogeneity. 2. 2. We have shown that effects due to film pressure, πe, would be in the opposite direction from those observed in hysteresis. Hence film pressure is not responsible for contact angle hysteresis.

An evaluation of pore structure by mercury penetration

The pore structure of graded series of controlled pore glasses and Nuclepore membranes—both materials having pores with right-cylinder characteristics—were assessed by electron microscopy and mercury penetration. From comparisons of results, parameters in mercury penetration theory were evaluated, the correction for compressibility was examined, the cause of hysteresis was explored, and the general accuracy of the technique was appraised.

Carbon Black Structure in Rubber

Abstract Some of the properties of carbon blacks in rubber are ascribed to its “structure”. This paper presents results on the sinusoidal dynamic straining of rubber/carbon black vulcanizates over an amplitude range including strains less than 0.1% and suggests that an elucidation of structure effects and the nature of the structure underlying them is forthcoming from these results. The dynamic properties are profoundly modified by special processing. Heat treatment of stocks containing structural carbon blacks and particularly the use of N-methyl-N,4-dinitrosoaniline can greatly reduce structure effects. They are absent with attrited blacks. Similar results have been obtained with silica fillers, for which certain metal soaps virtually eliminate structure effects. Structure effects are shown to be not essentially related to the rubber network, including the type of rubber, but to be due to a physical, three-dimensional structure of the filler itself within the rubber; the rubber acts merely as a dispersing medium and a matrix to allow the filler structure to re-form after breakdown. These changes of the filler structure are often the major cause of hysteresis at low extensions. Mixtures of carbon black and organic liquids demonstrate the existence and properties of the physical carbon black structure in absence of rubber. The properties of the rubber have the structural effects of the filler superimposed upon them.

Hysteresis of the Angle of Contact of Mercury against Steel

Experiments have been made to investigate some of the causes of the hysteresis of the angle of contact of mercury against steel. It is shown by experiments in vacuo and in gases at low pressures, that adsorption on the solid surface is a principal cause of hysteresis. In contrast to the results of earlier work, however, roughness does not affect the hysteresis, though the angles of contact themselves are altered. Some agreement with theoretical predictions is obtained.

HYSTERESIS IN SILICA GEL SORPTION SYSTEMS

The hysteresis which normally appears in the isotherms of the silica gel-water system has been attributed by Patrick to the presence of permanent gases in the system. Only one case has been found in which a reversible isotherm has been recorded in the silica gel-water system. For alcohol and benzene only one case of hysteresis has been reported. These results seem to be independent of the presence or absence of air or other gases.The sorption of water, benzene and ethyl alcohol has been examined using the sorption balance. A hysteresis loop appears for water only. This hysteresis may not be eliminated by special methods of evacuation and must be considered as a real effect. The isotherms of alcohol and benzene, on the other hand, are completely reversible. It has been shown that the dimensions of the hysteresis occurring in the water system may be affected by the manner of addition of vapor to the apparatus. Only when the vapor pressures remain reasonably constant during sorption are the dimensions of the effect evident. If very large pressure changes take place the hysteresis may disappear.A comparison of the isotherms for water showing hysteresis, and those of the sulphur dioxide system (upon which the original suggestion as to the cause of hysteresis was based) show that there is not necessarily any relation between the two.