Desiccation study

The IMS study showed an increased proportion in a-helix structure for both slow and mature drying. Thus, the acquisition of fuU desiccation tolerance is a gradual process that takes place during maturahon, as suggested previously 

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Sodium chlorodifluoroacetate is prepared in quantitative yield by careful neutralization of 130.5 g. (1.00 mole) of chlorodi-fluoroacetic acid (available from Allied Chemical Corp.) in 300 ml. of ether with 53.0 g. (0.500 mole) of anhydrous sodium carbonate, removal of the solvent and water under reduced pressure, and drying over phosphorus pentoxide in a vacuum desiccator. Studies have shown that the best yield of olefin is obtained when a 100% excess of salt is used. 

Tompsett, PB. Desiccation studies in relation to the storage of Araucaria seed, Ann. Appl. Biol, 105, 581,1984. 

Validation of body water measurements, using dilution principles and either of the hydrogen isotopes, can only be achieved from complementary desiccation studies. In fact it has been repeatedly demonstrated in animals that the volume of dilution of deuterium oxide corresponds closely to the total body water space [249—252]. A single report has suggested that the difference between isotope dilution using tritium and desiccation, was statistically significant in the rat and that the former method overestimated body water by 12% of the desiccation value [253]. 

Water content indirectly affects other lens characteristics. Water evaporation from the lens can result in a dry eye sensation and subsequent desiccative erosion of the cornea. Clinical studies have shown the incidence of corneal erosion as a result of lens desiccation to be a material-dependent and water-content-dependent phenomenon (25,26). The nature of water and sodium ions in hydrogels has been studied primarily by nmr and thermal techniques (27,28). An empirical relationship between water mobility in contact lens polymers and desiccative staining has been proposed (29). 

The efficiency ranking of desiccants in drying air is not always the same as that observed in drying other materials. Other materials may interact with the desiccants to reduce drying effectiveness. From a study of the efficiency of some 25 desiccants for drying several families of laboratory solvents and reagents it was concluded that molecular sieves are the desiccants of choice in most cases (9—17). 

Isopiestic or isothermal distillation. This technique can be useful for the preparation of metal-free solutions of volatile acids and bases for use in trace metal studies. The procedure involves placing two beakers, one of distilled water and the other of a solution of the material to be purified, in a desiccator. The desiccator is sealed and left to stand at room temperature for several days. The volatile components distribute themselves between the two beakers whereas the non-volatile contaminants remain in the original beaker. This technique has afforded metal-free pure solutions of ammonia, hydrochloric acid and hydrogen fluoride. 

Loading was accomplished by exposing the activated zeolites to benzene-de vapors. The extent of vapor adsorption was determined by the increase in weight of the zeolite. The samples were found to be extremely hydroscopic and thus kept in a vacuum desiccator until their use. After two or three temperature runs the samples began to adsorb water vapor. Therefore, only the data obtained for the first two variable temperature cycles are presented here. The samples studied are listed in Table I. 

Patnaik, S., T.G. Lenz, and G.O.G Lof, 1990, Performance study for an experimental solar open-cycle liquid desiccant system, Solar Energy, 44 (3), 123-135. 

The major function of cutin is to serve as the structural component of the outer barrier of plants. As the major component of the cuticle it plays a major role in the interaction of the plant with its environment. Development of the cuticle is thought to be responsible for the ability of plants to move onto land where the cuticle limits diffusion of moisture and thus prevents desiccation [141]. The plant cuticle controls the exchange of matter between leaf and atmosphere. The transport properties of the cuticle strongly influences the loss of water and solutes from the leaf interior as well as uptake of nonvolatile chemicals from the atmosphere to the leaf surface. In the absence of stomata the cuticle controls gas exchange. The cuticle as a transport-limiting barrier is important in its physiological and ecological functions. The diffusion across plant cuticle follows basic laws of passive diffusion across lipophylic membranes [142]. Isolated cuticular membranes have been used to study this permeability and the results obtained appear to be valid... 

In a highly replicated kinetic study (House and Eveland, 1993), the dehydration of samples of freshly prepared CaC204-H20 and material that had been stored in a desiccator for a year was studied. It was found that the kinetics of the dehydration reaction did not depend on the particle size, but there was... 

One may wonder why lobsters appear to use urine as a dispersal solvent for chemical signals, whereas terrestrial arthropods such as the well-studied insects use direct release of gland products into the air. Perhaps the answer is that small animals in air (such as insects) are always in danger of desiccation. By contrast, marine lobsters and crabs are relatively large and may experience only minor water loss problems due to osmosis. Thus, it may not be difficult for a 500-g lobster to store 10 ml of urine and release it during a dominance battle at a rate of up to 1 ml/min (27). The advantage of urine-carried pheromones is that the dispersal mechanism already exists urine is injected into the gill current, which in turn injects into ocean currents. 

Soma et al. (9) studied the interaction between a Ru - and CuZ -exchanged montmorillonite and p-dimethoxybenzene (DMBO) under desiccating conditions at room temperature. On the basis of Raman, IR, and VIS absorption spectra, they demonstrated that DMOB is stably adsorbed on Cu + and Ru +-exchanged montmorillonites as a radical cation. Oxidation by the metal cation was found to be reversible in the presence of water vapor ... 

Thermal/humidity stress testing involves exposing samples to various conditions of temperature and humidity. Once the conditions are chosen, the samples are placed in either ovens which control the conditions or saturated solutions of salts in desiccators. The physical appearance of the sample is important and should be monitored throughout the study. In addition, any loss or gain of water should be noted as well. 

Although arsenic was not initially reported in the samples studied by Wesley and Wall, re-examination of one of the samples did show it to be present. The cotton from which this sample came probably had not been desiccated the arsenic could have had its orgin in the soil from earlier days or as fiber residue from chemical pest control during the present cotton-growing season. 

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