Effect of rehydration

Figure 8. Effect of rehydration pH on concentration loss in static tests...

Waldhausl W, Kleinberger G, Korn A, Dudcza R, Bratusch-Marrain P Nowatny P Severe hyperglycemia effects of rehydration on endocrine derangements and blood glucose concentration. Diabetes 28 577-584,1979. 

Figure 5 Effects of rehydration (with deuterium oxide) on deuteroxyl bands of ZSM-5 [1.35% A120 3). Pretreatment a.

It is important to emphasize that spectroscopic evidence shows that water transforms the Lewis acid sites of sulfated zirconia into Bronsted acid sites [80]. At the same time, water promotes isomerization reactions over sulfated zirconia for a moderate extent of catalyst dehydration. Similarities were reported between the effect of rehydration on the isomerization activity of sulfated zirconia [81] and on that of other oxide catalysts [49] that are consistent with the role of surface donor sites in hydrocarbon isomerization reactions. However, when spectroscopic methods using basic probes were used to compare sulfated zirconia and zeolites in terms of the strength of their acid sites, the results were inconsistent with all catalytic data. These findings illustrate the danger of comparing the acidity of catalyst systems that differ in structure and composition, such as zeolites and sulfated zirconia in these systems the "catalytic" and the "physicochemical" scales for the strength of acid-base interaction may contain significantly different parameters. 

Gonzalez A, Vicente C, Legaz ME (1984) A simple Assay Demonstrating the Effect of Rehydration on the Orsellinate Depside Hydrolase Activity of Evernia prunastri J Plant Physiol 116 219... 

Some of our experimental adsorption data has already been analysed in detail, and from a rather different point of view, in a proceeding paper [9]. As the reversibility of the decomposition might be expected to throw some additional light on the structure of the decomposition products, additional results concerning the effect of rehydration were also obtained and are presented here. The structure of the decomposition products and the mechanism of decomposition are discussed in the light of these new results. 

The formation of niclosamide hydrates, and the effect of relative humidity on the solvatomorphs obtained from acetone and ethyl acetate has been studied [79], The acetone and ethyl acetate solvatomorphs could be desolvated, and exposure to elevated humidity resulted in the formation of two hydrate structures. Each hydrate could be dehydrated into a different anhydrate phase, but only the hydrate formed from the acetone desolvate could be rehydrated to form a hydrate phase. Dynamic vapor sorption has been used to develop a method for determining the onset relative humidity of a glass transition and associated crystallization process [80]. 

Figure 15.14 The effect of ethanol on RNase A structure (a) far-UV and (b) near-UV CD spectra of 0.65mg/mL solutions of RNase A. Curve 1, native RNAse A in PBS curve 2, native RNase A incubated under 100% ethanol for 1 week and then rehydrated in PBS curve 3, RNase A kept in 10% formalin for 1 week curve 4, RNase A fixed in 10% formalin, incubated under 100% ethanol for 1 week, and then rehydrated in PBS. See Fowler et al.12 for details.

Lima AA, Carvalho GH, Figueiredo AA, Gi-foni AR, Soares AM, Silva EA, Guerrant RL Effects of an alanyl-glutamine-based oral rehydration and nutrition therapy solution on electrolyte and water absorption in a rat model of secretory diarrhea induced by cholera toxin. Nutrition 2002 18 458-462. 

Lenart, A. 1991. Effect of saccharose on water sorption and rehydration of dried carrots. In Drying 91 (AS. Mujumdar and I. Filkova, eds), pp. 489 496. Elsevier Science, Amsterdam, The Netherlands. 

Such special atmosphere is often necessary in decomposition and rehydration studies of hydroxides, hydrates etc. Furthermore also the catalytic effect of water vapor on certain reactions is of interest. For such studies the gas is saturated with water, or other vapors e.g. D20, alcohol, CS2, etc. When higher water vapor concentrations are required special furnaces are available (see Sect. 2.4). 

The assay microorganisms in Polytox are a blend of bacterial strains originally isolated from wastewater [48]. The Polytox kit (Microbiotest Inc., Nazareth, Belgium), specifically designed to assess the effect of toxic chemicals on biological waste treatment, is based on the reduction of respiratory activity of rehydrated cultures in the presence of toxicants. The commercially available kit is specihcally designed for testing wastewaters. Quantative results can be obtained in just 30 minutes. 

Pereira et al. (1993) evaluated postoperative pain relief and incidence of side-effects of the combination of epidural morphine (0.5 mg) and sublingual nifedipine (10 mg). In this double-blind, placebo-controlled study 36 women were submitted to elective operations (hysterectomy and colpoperineoplasty). The nifedipine-treated group showed a significant drop in blood pressure which was controlled by rehydration. The results indicate that epidural morphine-induced postoperative pain relief may be enhanced by systemic administration of nifedipine with easily controlled side-effects. 

Silica gel is a polar material. The presence of silanol groups is responsible for the acidic catalytic effect of this material (the pK of Si OH is comparable to that of phenol). The mode of action of silica gel is based on adsorption (Fig. 3.9), a phenomenon that leads to the accumulation of a compound at the interface between the stationary and mobile phases. In the simplest case, a monolayer is formed (known as a Langmuir isotherm) but there is also some attraction and interaction between molecules that are already adsorbed and those still in solution. This contributes to the asymmetry of the elution profile. Although it demonstrates good resolution and a high adsorption capacity, bare silica gel is seldom used for analytical purposes. For most applications, it must be deactivated by partial rehydration (in 3-8% water). 

The relationship of Lewis and Brpnsted acid site concentrations on H—Y zeolite was explored further in a study by Ward (156) of the effect of added water. At low calcination temperatures (<500°C) only a small increase in the Brpnsted acid site concentration occurred upon addition of water to the sample. Rehydration of samples dehydroxylated by calcination above 600°C resulted in a threefold increase in the amount of Brpnsted-bound pyridine. However, no discreet hydroxyl bands were present in the infrared spectrum after rehydration. Thus, the hydroxyl groups reformed upon hydration must be in locations different from those present in the original H—Y zeolite, which gave rise to discreet OH bands at 3650 and 3550 cm-1. 

The movement of Na+ and glucose from the lumen of the intestine across the epithelial cell to the blood sets up a difference in osmotic pressure across the cell. As a result, water flows through the cell, across the apical and basolateral membranes by simple diffusion. Hence the uptake of water requires both Na+ and glucose (or amino acids) to be present in the lumen of the intestine. The presence of water alone in the lumen of the intestine is much less effective. This is the basis of glucose rehydration therapy as a remedy for dehydration a solution of glucose and salt (NaCl) is administered to the patient. This is a simple, inexpensive but extremely important treatment which has saved the lives of many infants in developing countries who would have otherwise died of the effects of dehydration, usually associated with diarrhea. 

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