A theory is developed to describe the one-dimensional movement of electrolyte in clay-electrolyte systems that are free to swell in the direction of electrolyte movement. This theory develops from the observation that Darcy's law describes flow of fluid relative to the comparatively immobile particles of clay, and is based on a scale of length defined with reference to the distribution of mass of the clay rather than the more conventional fixed scale of length. It is shown, theoretically and experimentally, that in this scale of length the appropriate equation is the diffusion equation, for the use of which there exists a large body of information in soil physics and other literature.
Background and purpose:We have previously shown that treatment with zinc plus cyclo-(His-Pro) (CHP) significantly stimulated synthesis of the insulin degrading enzyme and lowered plasma insulin and blood glucose levels, alongside improving oral glucose tolerance in genetically type 2 diabetic Goto-Kakizaki (G-K) rats and in aged obese Sprague-Dawley (S-D) rats. Thus, we postulated that zinc plus CHP (ZC) treatment might also improve body weight control in these rats. We therefore determined the effects of ZC treatment on body weights in both genetically diabetic, mature G-K rats and non-diabetic, obese S-D rats. Experimental approach: G-K rats aged 1.5-10 months and non-diabetic overweight or obese S-D rats aged 6-18 months were treated with 0-6 mg CHP plus 0-10 mg zinc·L -1 drinking water for 2-4 weeks, and changes in weight, serum leptin and adiponectin levels, food and water intakes were measured. Key results: The optimal dose of CHP (in combination with zinc) to reduce weight and plasma leptin levels and to increase plasma adiponectin levels was close to 0.1 mg·kg, in either mature G-K rats and aged overweight or obese S-D rats. Food and water intake significantly decreased in ZC treated rats in both aged S-D rats and mature G-K rats, but not in young S-D and G-K rats. Conclusions and implications: ZC treatment improved weight control and may be a possible treatment for overweight and obesity.
Examination of the existing outflow methods reveals that none of the available methods consider membrane impedance without simultaneously involving subjective curve matching. A method is proposed that meets both these requirements and also allows determination of hydraulic conductivity after only small changes of moisture content; the results are therefore easier to interpret. A comparison is made between results obtained from the proposed method and from published outflow methods, as well as from the horizontal infiltration and 'air-pressure' methods. The results obtained exhibit hysteresis for both diffusivity and hydraulic conductivity as functions of moisture content. An hypothesis explaining occurrence of hysteresis in hydraulic conductivity at low moisture contents is presented. It is concluded that the proposed outflow method is experimentally suited to the dry end of the moisture content range, because of the restriction imposed at high moisture contents by the membrane impedance being large relative to the sample impedance. A simple criterion to determine the range of validity of the method is proposed.
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