Water vapor, homogeneity

We consider a finite space, which contains the NA sample and is in contact with a bath of water or water vapor. That allows one to maintain the r.h. in the experimental space at a constant level and change it when necessary. Such a scheme corresponds to the real experiments with wet NA samples. A NA molecule is simulated by a sequence of units of the same type. Thus, in the present study, we consider the case of a homogeneous NA or the case where averaging over the unit type is possible. Every unit can be found in the one of three conformational states unordered. A- or B- conformations. The units can reversibly change their conformational state. A unit corresponds to a nucleotide of a real NA. We assume that the NA strands do not diverge during conformational transitions in the wet NA samples [18]. The conformational transitions are considered as cooperative processes that are caused by the unfavorable appearance of an interface between the distinct conformations. 

Homogeneous Nucleation a process by which gases interact and combine with droplets made up of their own kind. For instance, the collision and subsequent adherence of water vapor to a water droplet is a homogeneous nucleation. See nucleation. 

Chemical equilibria with reactants and products that are all in the same phase are called homogeneous equilibria. Equilibria C, D, and E are homogeneous. Equilibria in systems having more than one phase are called heterogeneous equilibria. Equilibrium F is heterogeneous so too is the equilibrium between water vapor and liquid water in a closed system ... 

Alloys are classified broadly in two categories, single-phase alloys and multiple-phase alloys. A phase is characterized by having a homogeneous composition on a macroscopic scale, a uniform structure, and a distinct interface with any other phase present. The coexistence of ice, liquid water, and water vapor meets the criteria of composition and structure, but distinct boundaries exist between the states, so there are three phases present. When liquid metals are combined, there is usually some limit to the solubility of one metal in another. An exception to this is the liquid mixture of copper and nickel, which forms a solution of any composition between pure copper and pure nickel. The molten metals are completely miscible. When the mixture is cooled, a solid results that has a random distribution of both types of atoms in an fee structure. This single solid phase thus constitutes a solid solution of the two metals, so it meets the criteria for a single-phase alloy. 

The rate constants for both homogeneous and heterogeneous reactions related to the oxides of nitrogen and water vapor should be... 

The homogeneous and heterogeneous reactions of the oxides of nitrogen with water vapor need study. 

Although Eq. 27 appears to be the most likely initiation reaction, we cannot rule out a process in which water vapor and DMTC react, based on the ab initio results described in Sect. 4.6. If this does occur, however, it apparently does not lead to homogeneous nucleation of particles, since anecdotal evidence from the glass industry indicates that DMTC and water vapor can be premixed prior APCVD of tin oxide without substantial buildup of solids in delivery lines. Perhaps this is due to significant kinetic barriers to the decomposition of the tin-water complexes that initially form, so that further gas-phase reaction does not occur until the reactants enter the heated boundary layer above the substrate. 

The term phase defines any homogeneous and physically distinct part of a system which is separated from other parts of the system by definite bounding surfaces. For example, ice, liquid water, and water vapor are three phases. Each is physically distinct and homogeneous, and there are definite boundaries between ice and water, between ice and water vapor, and between liquid water and water vapor. Thus, we say that we have a three-phase system solid, liquid, and gas. One particular phase need not be continuous. For instance, the ice may exist as several lumps in the water. 

The process of pressure distillation through a homogeneous membrane is based first on the common fact that the vapor pressure of any liquid can be increased by compressing it or decreased by placing it under suction, and second on the equally common fact that only pure water vapor escapes from water into vapor or air, leaving nonvolatile salts behind the phase boundary. In operating the processes of vaporization—heat transfer and diffusion across an extremely thin gap—no new phenomena or new properties of materials are required. However, the novel combination of capillary surfaces, pressure, and extremely short paths for heat and diffusion offers an opportunity for improvements in film properties and methods of construction not known before. 

Ordinarily, the system may consist of several phases, whose interior in the state of equilibrium is homogeneous throughout its extent. The system, if composed for instance of only liquid water, is a single phase and if made up for instance of liquid water and water vapor, it is a two phase system. The single phase system is frequently called a homogeneous system, and a multiphase system is called heterogeneous. 

Experimental Details. A fair comparison between the apparent densities of clays immersed in water and of clays with a certain number of preadsorbed monolayers immersed in n-decane requires that each preadsorbed monolayer of water between the unit layers is completed, so that no vacant space within a mono-layer exists. The clay should be in the same state of hydration in the entire system. The selectively accessible void space should be completely filled, as well as capillaries in the clay aggregates. The homogeneous distribution of the adsorption water was achieved by slowly equilibrating thin flakes of clay with almost saturated water vapor. After about one month of equilibration, the uniform state of hydration of the clay was shown by the sharpness and order of the x-ray diffraction pattern. The completion of the monolayers was judged from the amount of water taken up by the clay, with the knowledge that about 100 mg. of water is needed per gram of clay for the formation of a monolayer. 

Alloys are classified broadly in two categories, single-phase alloys and multiple-phase alloys. A phase is characterized by having a homogeneous composition on a macroscopic scale, a uniform structure, and a distinct interface with any other phase present. The coexistence of ice, liquid water, and water vapor meets the criteria of composition and structure, and distinct boundaries exist between the states so there are three phases present. 

It was found by Wilson (1897) that when air at 20°C, initially saturated with water vapor and free of any condensation nuclei, was expanded with an expansion ratio in excess of 1.37, homogeneous nucleation occurred. What is the value of S implied by this expansion ratio ... 

In piston-gap homogenization, suspension contained in a cylinder passes a very thin gap with an extremely high velocity. Bubbles of water vapor are produced for... 

As a particular example, one can consider the homogeneous nucleation in the pure water vapor at 25° C. The surface tension coefficient of water is a = 71.96 N/m at this temperature. Table 5.1 shows some characteristics of the new phase. When the oversaturation is p/p =8.1, the critical nucleus of 0.5 nm radius is seen to comprise 18 water molecules. The equihbrium pressure of such nuclei is not high (approximately 10 bar). Since the water vapor pressure in real clouds is usually no more than 0.1% over that of the saturated vapor, it is unrealistic to expect in the rea sonable time scale the homogeneous formation of water drops in Earth s atmosphere. 

Particle formation events from gaseous precursors are observed frequently almost everywhere in the troposphere, both in polluted cities and remote clean areas [4]. It is likely that different nucleation mechanisms are at work in different conditions, but no formation mechanism has been identified so far. It is, however, clear that particles are formed by nucleation of a multicomponent vapor mixture. Water vapor is the most abundant condensable gas in the atmosphere, but it can not form particles on its own homogeneous nucleation requires such a high supersaturation, that heterogeneous nucleation on omnipresent pre-existing particles always starts first and consumes the vapor. However, vapor that is un-... 

Debeaufort, F., Martinpolo, M., and Voilley, A. (1993). Polarity Homogeneity and Structure Affect Water-Vapor Permeability of Model Edible Films. J. Food Sci. 58(2), 426. 

P. P. Wegener, Gasdynamics of Expansion Flows with Condensation and Homogeneous Nucleation of Water Vapor, Chapter 4 of Nonequilibrium Flows, vol. 1, part 1, P. P. Wegener, ed.. New York Marcel Dekker, 1969. 

Number of phases into which a given qrstem is divided.— The heterog eous systems studied by the chemist are divided into a certain number of homogeneous masses a stem formed of water and water vapor is divided into a homogeneous mass of liquid water and a homogeneous mass of water vapor. 

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