Grzegorczyn Sławomir, Dylong Iwona, Dolibog Paweł, Ślęzak Andrzej
Department of Biophysics, Faculty of Medical Sciences in Zabrze, Medical University of Silesia, Katowice, Poland.
Collegium Medicum, Jan Dlugosz University, Częstochowa, Poland.
PLoS One. 2024 Dec 12;19(12):e0315508. doi: 10.1371/journal.pone.0315508. eCollection 2024.
The characteristic manifestations of instability were observed in the form of voltage pulsations measured between electrodes immersed directly in solutions of membrane system chambers, in different configurations of membrane systems. The reason for this type of voltage pulsations is Rayleigh-Benard type instabilities of near-membrane layers caused by density gradients of solutions in these layers. The time of build-up of the concentration boundary layer, after which hydrodynamic instability appears is one of important parameters of these phenomena. The concentration characteristics of these times, measured for one- and two-membrane systems, are nonlinear. With increasing differences in the density of solutions on the membrane at the initial moment, the times of build-up of concentration boundary layers were reduced. In two-membrane systems containing ternary solutions (water, NaCl, ethanol), ethanol was used to control the initial differences in the density of solutions on the membrane. The times of hydrodynamic instabilities in two-membrane system were symmetrical due to the concentration of ethanol, for which the densities of solutions on both sides of the membrane were the same at the initial moment. This dependence is similar for both configurations of the membrane system and is characterized by two nonlinear curves converging to the concentration of ethanol at which, at the initial moment, the densities of the solutions in the chambers of the two-membrane system are the same. In turn, the steady-state voltages of the two-membrane system as a function of the initial concentration of ethanol in the middle chamber with the same initial NaCl concentration in the middle chamber, are a complex function depending on the membrane arrangement. These voltages are characterized by a transition in the ethanol concentration range, for which, at the initial moment, the densities of the solutions in the chambers of the two-membrane system are comparable.
在不同配置的膜系统中，通过测量直接浸入膜系统腔室溶液中的电极之间的电压脉动，观察到了不稳定性的特征表现。这种类型的电压脉动的原因是这些层中溶液密度梯度引起的近膜层的瑞利 - 贝纳德型不稳定性。浓度边界层形成的时间（在此之后出现流体动力学不稳定性）是这些现象的重要参数之一。针对单膜和双膜系统测量的这些时间的浓度特性是非线性的。随着初始时刻膜上溶液密度差异的增加，浓度边界层形成的时间缩短。在含有三元溶液（水、氯化钠、乙醇）的双膜系统中，乙醇用于控制膜上溶液密度的初始差异。由于乙醇的浓度，双膜系统中流体动力学不稳定性的时间是对称的，在初始时刻膜两侧溶液的密度相同。对于膜系统的两种配置，这种依赖性是相似的，其特征是两条非线性曲线汇聚到乙醇浓度，在初始时刻，双膜系统腔室中溶液的密度相同。反过来，在中间腔室初始氯化钠浓度相同的情况下，双膜系统的稳态电压作为中间腔室乙醇初始浓度的函数，是一个取决于膜排列的复杂函数。这些电压的特征是在乙醇浓度范围内有一个转变，在初始时刻，双膜系统腔室中溶液的密度在这个范围内是可比的。
