Factors Determining Viscosity

It is important from a practical viewpoint to predict the shear viscosity of mixtures from those of pure melts. For alkali nitrate melts, a linear dependence has been found between the reorientational line width obtained by Raman measurements and the ratio of temperature divided by shear viscosity.For NO3 ions, the depolarized Raman scattering from 1050cm total stretching vibrational mode (Al) has a contribution to the line width L, which is caused by the reorientational relaxation time of the Csv axis of this ion. The Stokes-Einstein-Debye(SED) relation establishes a relation between the shear viscosity r of a melt and the relaxation time for the reorientation of a particle immersed in it  

The occurrence of a term Fg besides the term is analogous to that in Eq. (83) implies that there are at least two different types of elementary 

A review article has been published on depolarized Raman spectroscopy in molten salts, and it is discussed briefly here for the case of molten nitrates. Polarized (VV) and depolarized (HV) Raman scattering of the 1050 cm line was used. The intensity of the isotropic part of the 

The shapes of both /w and 7hv lines are assumed to be represented by simple Lorentzians. For a totally symmetric vibration with a low polarization ratio as in the present case, the vibrational and reorientational relaxation times Tv and can be determined from the half-widths of the isotropic and anisotropic spectra. Since the value of /hv is much smaller than that of /w for the 1050 cm line, the contribution of /gv to the isotropic intensity can be neglected  

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Having thus seen that enviromental factors determine viscosity largely by their effect on free volume let us now consider the influence of molecular factors which affect viscosity largely by entanglement effects. 

Factors determining resistance to airflow are also analogous to those determining the resistance to blood flow and include viscosity, length of the airway, and airway radius. Under normal conditions, the viscosity of the air is fairly constant and the length of the airway is fixed. Therefore, airway radius is the critically important physiological factor determining airway resistance ... 

Shand et al. (2002) have shown that, compared with placebo-treated subjects, long-term raloxifene treatment in postmenopausal women, at a dose of either 60 or 120 mg/d, was not associated with adverse changes in hemorheological factors (determinants of blood viscosity) that may contribute to venous thromboembolism. 

Normally, the various factors do not influence the bubble size to the same extent over the entire range of the other variables. Thus surface tension, which is one of the most important factors determining the bubble size at vanishingly small flow rates, assumes much less importance at higher flow rates. Similarly, the viscosity of the liquid is much more important at higher flow rates than at the lower ones. 

The understanding of the temperature and conversion dependence of the crosslinking kinetics is one of the prerequisites for understanding the changes in viscosity and viscoelastic properties as a function of reaction time and reaction temperature ( ). Three main factors determine these relations the reaction kinetics determined by temperature and conversion, the changes in structure determined primarily by conversion and the changes in Tg determined primarily also by conversion. 

In practice, it is the viscosity that is experimentally determined, and the correlations are used to determine axial ratios and shape factors. The viscosity can be determined by any number of techniques, the most common of which is light scattering. In addition to ellipticity, solvation (particle swelling due to water absorption) can have an effect on... 

With all of the hydrocarbons except amyldiphenyl, phytotoxicity appeared to be a direct function of concentration of the hydrocarbon—i.e., the lower the concentration, the lower the toxicity. For amyldiphenyl, however, concentrations of 30 to 50% produced more rapid injury and a greater degree of injury than did higher concentrations. The reasons are not clear for the apparently anomalous action of amyldiphenyl and for the apparent decrease in acute toxicity of hydrocarbons with increasing boiling points above about 500 F. Chemical properties alone may be responsible, but it is more likely that some physical property such as viscosity, surface tension, or size of molecule may be involved. Viscosity is probably the factor determining acute or chronic tjrpe of injury. 

Mode coupling theory provides the following rationale for the known validity of the Stokes relation between the zero frequency friction and the viscosity. According to MCT, both these quantities are primarily determined by the static and dynamic structure factors of the solvent. Hence both vary similarly with density and temperature. This calls into question the justification of the use of the generalized hydrodynamics for molecular processes. The question gathers further relevance from the fact that the time (t) correlation function determining friction (the force-force) and that determining viscosity (the stress-stress) are microscopically different. 

The main factor determining the stability of such foams is the rate and extent of drainage from the thin liquid film. In general, this type of foam is relatively unstable. The stability may be enhanced by increasing the viscosity of the liquid by increasing the dry matter content or adding certain hydrocolloids. The foam stability may also be enhanced with hydrocolloids, in particular microcrystalline cellulose. 

Since the apparent viscosity of a non-Newtonian fluid holds only for the shear rate (as weii as temperature) at which it is determined, the Brookfield viscometer provides a known rate of shear by means of a spindle of specified configuration that rotates at a known constant speed in the fluid. The torque imposed by fluid friction can be converted to absolute viscosity units (centipoises) by a multiplication factor. See viscosity, shear stress. The viscosities of certain petroleum waxes and wax-polymer blends in the molten state can also be determined by the Brookfield test method ASTM D 2669. 

Merely because a substance depresses blood pressure does not make it a true antihypertensive substance. The level of blood pressure is the resultant of several factors the viscosity of the blood, the cardiac output, the volume of circulating blood, and the state of the arterial and arteriolar bed, which determines the peripheral resistance to blood flow, other factors being equal. This discussion has indicated that peripheral resistance through arteriolar constriction may be affected by renal blood flow and the production of circulating pressor agents. Therefore, a definition of a true antihypertensive substance is necessary, in order that we be not misled by depressor substances which lower blood pressure at a detriment to the body s economy. 

Table 1 presents the results obtained from the fermented broth in the different experimental conditions selected after 48 h. Determination of the viscosities indicated that at conditions below the control factors, higher viscosity values were obtained for the fermented broth low values of substrate concentration, aeration, and agitation promoted higher viscosity values in the cultivation broth after 48 h of process. 

By postulating that the primary factor determining the concentration and temperature dependence of viscosities of concentrated polymer solutions is the mobility of each flow unit or a segment of polymer molecule in solution, Fujita and Kishimoto (1961) have derived an equation for the viscosity of such solutions. If we denote byBj, the value of B corresponding to the minimum hole required for one flow unit to allow of a considerable displacement, their equation can be put in the form ... 

The ratio of surface energies is the main factor determining the distribution of phases after a melt has formed in the material. This ratio will decide whether the melt will wet the solid surfaces and whether it will penetrate into the capillaries. The behaviour of a melt in pores of a solid system can be characterized by the contact angle O. Perfect wetting takes place when 0 = 0. The rate at which a liquid spreads over a surface or penetrates into the pores is given by its viscosity. 

An important conclusion of the above approximate Analysis is that the effective kinematic viscosity of the emulsion is the dominant factor determining both the initial growth of instabilities and the most sensitive wave number. Thus, prediction of the effect of system properties on bubble stability depends on prediction of the effect on the effective kinematic... 

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