Stable variable

Soil temperature (ST) is one of the most stable variables, although differences can be detected considering 100% at the edge (18°C on average) is reduced to 25% in the interior. 

STM instruments have evolved from a complicated homebuilt instrument sensitive to vibrations into a compact, rigid, stable variable-temperature microscope, available commercially at fairly low cost. The availability of the instrumentation for STM has led to a tremendous diversification of the application of the technique, and new areas of applications are constantly being developed. 

Va.st. (variable stability) scaling [62] (it consists of down-weighting those variables that are the least stable and focusing on stable variables, using the standard deviation and the so-called coefficient of variation as scaling factor). 

A general prerequisite for the existence of a stable interface between two phases is that the free energy of formation of the interface be positive were it negative or zero, fluctuations would lead to complete dispersion of one phase in another. As implied, thermodynamics constitutes an important discipline within the general subject. It is one in which surface area joins the usual extensive quantities of mass and volume and in which surface tension and surface composition join the usual intensive quantities of pressure, temperature, and bulk composition. The thermodynamic functions of free energy, enthalpy and entropy can be defined for an interface as well as for a bulk portion of matter. Chapters II and ni are based on a rich history of thermodynamic studies of the liquid interface. The phase behavior of liquid films enters in Chapter IV, and the electrical potential and charge are added as thermodynamic variables in Chapter V. 

Excitable media are some of tire most commonly observed reaction-diffusion systems in nature. An excitable system possesses a stable fixed point which responds to perturbations in a characteristic way small perturbations return quickly to tire fixed point, while larger perturbations tliat exceed a certain tlireshold value make a long excursion in concentration phase space before tire system returns to tire stable state. In many physical systems tliis behaviour is captured by tire dynamics of two concentration fields, a fast activator variable u witli cubic nullcline and a slow inhibitor variable u witli linear nullcline [31]. The FitzHugh-Nagumo equation [34], derived as a simple model for nerve impulse propagation but which can also apply to a chemical reaction scheme [35], is one of tire best known equations witli such activator-inlribitor kinetics ... 

Fig. 1. The dependence of the stable stationary values of the adsorption and conformational variables on the control parameter, Xe. a-total adsorption per the mole of the nucleotides, b-the probability of finding of an arbitrary NA unit in the A form, c-the probability of finding of an arbitrary NA unit in the B-form. Param-(ders values used to obtain numerical results Vmi = 3,nL = 15.4, = 3.24,6° =...

Fig. 2. The dependence of the stable stationary values of the adsorption and conformational variables on the control parameter, for 0 < < 0.9. a-total adsorption...

Algorithms based on the last approach usually provide more flexible schemes than the other two methods and hence are briefly discussed in here. Hughes et al. (1986) and de Sampaio (1991) developed Petrov-Galerkin schemes based on equal order interpolations of field variables that used specially modified weight functions to generate stable finite element computations in incompressible flow. These schemes are shown to be the special cases of the method described in the following section developed by Zienkiewicz and Wu (1991). 

X 10 J/T (5.71 //g) at room temperature. It is air stable at 25°C, but is slowly converted to Fe202 and bromine at 310°C. The light yellow to brown hydroscopic sohd is soluble ia water, alcohol, ether, and acetonitrile. Iron(II) bromide forms adducts with a wide range of donor molecules. Pale green nona-, hexa-, tetra-, and dihydrate species can be crystallized from aqueous solutions at different temperatures. A hydrate of variable water content,... 

Formaldehyde may react with the active hydrogens on both the urea and amine groups and therefore the polymer is probably highly branched. The amount of formaldehyde (2—4 mol per 1 mol urea), the amount and kind of polyamine (10—15%), and resin concentration are variable and hundreds of patents have been issued throughout the world. Generally, the urea, formaldehyde, polyamine, and water react at 80—100°C. The reaction may be carried out in two steps with an initial methylolation at alkaline pH, followed by condensation to the desired degree at acidic pH, or the entire reaction may be carried out under acidic conditions (63). The product is generally a symp with 25—35% soHds and is stable for up to three months. 

Hydrated Stannic Oxide. Hydrated stannic oxide of variable water content is obtained by the hydrolysis of stannates. Acidification of a sodium stannate solution precipitates the hydrate as a flocculent white mass. The colloidal solution, which is obtained by washing the mass free of water-soluble ions and peptization with potassium hydroxide, is stable below 50°C and forms the basis for the patented Tin Sol process for replenishing tin in staimate tin-plating baths. A similar type of solution (Staimasol A and B) is prepared by the direct electrolysis of concentrated potassium staimate solutions (26). 

In general, exempt colorants have less coloring power than certified colorants and thus have to be used at higher concentrations. Some, particularly those of plant origin, tend to be less stable, more variable in shade, and therefore more compHcated to use than certified colorants, and are more likely to introduce undeskable flavors and odors into the products in which they are incorporated. Also, depending on thek nature and origin, exempt colorants can vary substantially in composition from batch to batch, are more likely to be contaminated with undeskable trace metals, insecticides, herbicides, and bacteria such as Salmonella and can be more difficult to obtain in steady supply compared with certified colorants. 

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