Structure relative humidity

However, the B.E.T. and modificated B.E.T as well as isotherm of d Arcy and Watt fit the experimental data only in some range of the relative humidities up to about 80-85%. At the same time the adsorption in the interval 90-100% is of great interest for in this interval the A— B conformational transition, which is of biological importance, takes place [17], [18]. This disagreement can be the result of the fact that the adsorbed water molecules can form a regular lattice, structure of which depends on the conformation of the NA. To take into account this fact we assume that the water binding constants depend on the conformational variables of the model, i.e ... 

The substitution of the two-sided tape with a film of an ionic conductor gives (Fig. 24) a triple-layered muscle working in air.114 The tape now acts as a solid electrolyte. Nevertheless, the system only works if the relative humidity in air surpasses 60%. Under these conditions, movements and rates similar to those shown by a triple layer working in aqueous solution were obtained. This device was developed in cooperation with Dr. M. A. De Paoli from the Campinnas University (Campinnas, Brazil). At the moment several groups are developing actuators, muscles, and electrochemomechanical devices based on bilayer or multilayer structures.115-125... 

Although most of the water in the meniscus evaporates once the tip has been retracted, residual structures can be observed in a radius of several tens of micrometers (depending on humidity and contact time) around the original contact point. For the tip radius and loads used in these experiments, the contact radius is approximately 10 A. The residual structures are in the form of flat islands and sometimes droplets. In our first experiments the perturbation created by a brief tip contact was not fuUy appreciated. Accidental tip contacts during approach of the tip to the surface do often occur. In such cases the tip is subsequently moved to an adjacent area, several micrometers away, to study the unperturbed surface. However, as stated already, the perturbed areas can extend over tens of micrometers away from the contact point. Droplets can be observed when the relative humidity is... 

Drugs that associate with water to produce crystalline forms are called hydrates. Water content of the hydrate forms of sodium cefazolin as a function of relative humidity is seen in Fig. 1. As shown in Fig. 1, the sesquihydrate is the most stable structure when exposed to extreme humidity conditions [6], This figure also shows the importance of choosing the proper combination of hydrate and humidity conditions when designing a manufacturing process or facility. 

The effect of relative humidity and temperature on the physical and structural properties of the 1 1 isopropanol solvatomorph of warfarin has been studied [58], Below the critical relative humidity of 60-68% the solid is not hygroscopic, but becomes deliquescent at higher values of relative humidity without exchange of water for isopropanol. Storage of the solvate-morph at elevated temperatures causes formation of an amorphous solid owing to loss of isopropanol, which may proceed through an intermediate crystalline phase. 

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]. 

The physical state of the skin is considerable affected by external factors such as relative humidity, temperature, and air movement at the skin surface. If this contact is broken (for example, by external applications of ointments or creams), it is reasonable to assume that the new skin will change in some way, sometimes to an extent that creates new conditions of permeability for the test material. This would be the case, for example, if the stratum comeum becomes more hydrated than normal due to the topical delivery form. Temperature might also have an effect, as is the case when any constituents of the vehicle affect the inner structure of the skin through interactions with endogenous skin substances. Often several of these processes occur together. 

FIGURE 3 CE-ESI/MS analysis of a stressed galantamine sample (18 months, 25°C, 60% relative humidity) with structures and MS/MS spectra of both identified degradation products (peaks I and 2, m/z 302 and 274, respectively). Adapted from reference 169 with permission from Wiley-VCH Verlag GmbH. 

The molecular structure of arsphenamin is a typical representative of a thermotropic mesogen. With its symmetrical arrangement of the atoms the same holds for disodium cromoglycate, DNCG [20], which forms both thermotropic liquid crystals and lyotropic mesophases in the presence of water. Micronized DNCG powder applied to the mucosa of the nose or the bronchi absorbs water from the high relative humidity of the respiration tract and is first transformed into a lyotropic mesophase and then into a solution depending on the amount of water available. 

Changes in such physical factors as light, temperature (particularly maximums and minimums), relative humidity, and wind speed in forest communities subject to structural alteration by mortality of susceptible species could change the suitability of some sites for growth, reproduction, and re-establishment of survivor species. We can only speculate on some of the possible secondary effects until more data are gathered. ... 

Volume deformations under drying conditions It is under conditions where moisture is lost from concrete that volume deformations under loaded or unloaded conditions occur to any magnitude. It is difficult to say what degree of relative humidity structural concrete will be subjected to in actual practice, but certainly for thin sections or near the surface of large sections, considerable interchange of water due to changing climatic conditions will occur. 

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