Diffusion factor

The disposable parameters in these equations are the permeability 0, the surface diffusion factor y, the tortuosity function . (a) (which also... 

Lieblein, S., Schwenk, F.C., and Broderick, R.L., Diffusion Factor for Estimating Losses and Limiting Blade Loading in Axial-Flow Compressor Blade Elements, NACA RM 53001 (1953). 

The dimensionless number Le is called the Lewis number (m Russian literature it is called the Luikov number). The Lewis number incorporates the specific heat capacity of humid air pCp (J/m C), the diffusion factor of water vapor in... 

The diffusion factor D, which is contained in the Lewis number, is inversely related to the total pressure ... 

Temperature rc) Humidity kg HjO/kg dry air) Water vapor partial pressure (kPa) Water v K>r partial density (kg/m ) Water vaporization heat M/kg) Mixture enthalpy (kj/kg dry air) Dry air partial density (lKinematic viscosity (I0< mJ/s) Specific heat (kJ/K kg) Heat conductivity (W/m K) Diffusion factor water air (1 O mJ/s) Temperature rc)... 

For the mass balance of component A, diffusion velocity and the corresponding diffusion factor are defined with regard to the mean molar velocity V, defined by the equation... 

In a boundary layer equation the mass center is considered with the help of the velocity (u, Uy, u ) and therefore a distribution of the velocity of the mass center is desirable. The diffusion velocity and diffusion factor are determined with regard to velocity v, giving a formula for Vax /x, but not for /ax - x useful approach is offered by Eq. (4.268c), using the artificial multiplication factor (v - ax /... 

Note the diffusion factor appearing in the Schmidt number, D a/, ==... 

It is not possible to translate the above reasoning to turbulent flow, as turbulent flow equations are not reliable. However, in practice it is typical to assume that the same analogy is also valid for turbulent flow. Because of this hypothesis level, it is quite futile to use the diffusion factor D g in the Schmidt number instead we will directly use the number D g as in the Sherwood number. Hence in practical calculations Sc = v/D b-... 

If temperature gradients are small, Cr may be regarded as effectively constant. Furthermore, Kart is a function of composition, being approximately proportional to the product x, Xr. It is therefore useful to work in terms of the thermal diffusion factor a, where ... 

Equation 10.61 gives the mole fraction of the two components A and B as a function of the absolute temperatures and the thermal diffusion factor. 

Table 10.5. Values of thermal diffusion factor (a) for binary gas mixtures (A is the heavier component, which moves towards the cooler end)...

Electrochemical macrokinetics deals with the combined effects of polarization characteristics and of ohmic and diffusion factors on the current distribution and overall rate of electrochemical reactions in systems with distributed parameters. The term macrokinetics is used (mainly in Russian scientific publications) to distinguish these effects conveniently from effects arising at the molecular level. 

Different. Ingham (1975) diffusion deposition but corrected by turbulent diffusion factors in airways 0 to 6 as measured by Cohen (1986). 

It is well known that enhanced deposition in the first few airways occurs due to the turbulence produced. Turbulent diffusion is accounted for by using factors (ratio of observed deposition to calculated diffusion deposition) to correct the diffusion deposition. These had formerly been measured by Martin and Jacobi (1972) in a dichotomous plastic model of the upper airways. The data used here are from measurements performed by Cohen (1986) using hollow casts of the upper bronchial tree which included a larynx. This cast was tested using cyclic flow with deposition measured for 0.03, 0.15 and 0.20 urn diameter particles. Her turbulent diffusion factors are used in the calculation here (14 for generation 0, and 2 for generations 1 to 6). 

A kinetic model based on the Flory principle is referred to as the ideal model. Up to now this model by virtue of its simplicity, has been widely used to treat experimental data and to carry out engineering calculations when designing advanced polymer materials. However, strong experimental evidence for the violation of the Flory principle is currently available from the study of a number of processes of the synthesis and chemical modification of polymers. Possible reasons for such a violation may be connected with either chemical or physical factors. The first has been scrutinized both theoretically and experimentally, but this is not the case for the second among which are thermodynamic and diffusion factors. In this review we by no means pretend to cover all theoretical works in which these factors have been taken into account at the stage of formulating physicochemical models of the process... 

This is known as the quadratic driving force equation. A plot of ln[l — (Cs/C )2] against t gives a straight line and the diffusion factor icDs/r2 may be obtained from the slope. 

APOE is expressed at high levels in hepatocytes, macrophages, fibroblasts and astrocytes. Neurons also express APOE at lower levels than astrocytes in response to various physiological and pathological conditions, including excitotoxic stress. Neuronal expression of APOE is regulated by a diffusible factor or factors released from astrocytes, and this regulation depends on the activity of the Erk kinase pathways in neurons (499). 

Our data suggests that hematopoiesis can be sustained for prolong cultivation periods in the presence of feeder layer cells or condition media supported culture models. Prolonged support of primitive hematopoietic cells (undifferentiated cells such as promyelocytes, myelocytes and metamyelocytes) and their clonogenic capacity and functional characteristics in feeder layer positive cultures, indicates that diffusible factors are sufficient and that direct cell-to-cell contacts may not be exclusively required for successful long term in K/fro hematopoiesis. 

Detailed analysis of the cultured cells indicated, that direct cell-to-cell contact of the stromal and hematopoietic cells are not necessary for hematopoiesis, and that diffusible factors produced by feeder layers are sufficient. Prevailing proliferation in AC133+ cultures with feeder layers, the ability of cells to form... 

Most parasites have to survive prolonged periods of time apart from the host plant. Consequently, the formation of resting propagules, such as sclerotia, constitutes a critical part of the parasite s life cycle. Several observations indicate that formation of sclerotia may be stimulated by allelochemicals (, 9). Brandt and Reese (10) concluded that Verticillium dahliae produces a diffusible morphogenetic factor that stimulates production of microsclerotia. When low concentrations of the diffusible factor were added to cultures of the pathogen, the hyphae swelled and became constricted, septation was increased, and cell walls became thickened. 

The above discussion shows that the progress of deactivation may occur in different ways depending on the type of decay reaction occurring and on the value of the pore diffusion factor. For parallel and series poisoning, the Thiele modulus for the main reaction is the pertinent pore diffusion parameter. For side-by-side reactions, the Thiele modulus for the deactivation is the prime parameter. 

To reveal factors which influence activities of acid-base catalysts in alkylation and isomerization is the challenge to activity in this field. Q he greatest amount of work has been done in connection with the effect of para-selectivity, which is observed in alkylation of aromatic hydrocarbons on ZSM-5 type zeolites [1]. This effect has been explained by a number of authors either by the influence of diffusion factors [2,3] or by the isomerizing activity of the external surface of zeolite crystals [4]. In refs. [5,6] and especially in ref.[7] the para-selective effect of ZSM-5 type zeolites is shown to be due to decreasing their isomerizing activity becaiase of the decrease in the concentration of strong protic centres as a result of modifiers introduced. Para-selective effect is related to the action of chemical factors. However, in... 

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