Trans diffusion

The process of reorientation during cis—>trans thermal isomerization can be seen at the value of in Equation 3.11, which shows that the cis anisotropy does not contribute to the trans anisotropy if the trans isomer loses total memory of the orientation in the cis isomer Q2 = 0). It is informative to note that in the realistic physical case—i.e., the case of the azobenzene molecule chemically attached to a polymer, where the cis and trans diffusion rates are negligible in comparison to the cis— trans isomerization rate—the relaxation of the cis and trans anisotropy, AA and can be written respectively in the form ... 

We simulated a mild retort process by boiling the T.F.P films in water for predetermined time intervals. Following boiling the film was mounted in the MOCON Ox-Tran diffusion cell and 0% RH gas streams were flushed past both sides of the film. 

Courtney S H, Kim S K, Canonica S and Fleming G R 1986 Rotational diffusion of stiibene in alkane and alcohol solutions J. Chem. See. Faraday Trans. 2 82 2065-72... 

Lennard-Jones J E 1932 Prooesses of adsorption and diffusion on soiid surfaoes Trans. Faraday Soc. 28 333... 

Kirkendall E O 1942 Diffusion of zinc in a-brass Trans. Metall. Soo. AIME 147 104... 

Rabinowitch E 1937 Collision, coordination, diffusion and reaction velocity in condensed systems Trans. Faraday See. 33 1225-33... 

Caldin E F, de Forest L and Queen A 1990 Steric and repeated collision effects in diffusion-controlled reactions in solution J. Chem. See. Faraday Trans. 86 1549-54... 

G. H. Frishat, Ionic Diffusion in Oxide Glasses Trans Tech Pubbcations, Bay Village, Ohio, 1975. 

F. Kamenetski, Diffusion and Heat Exchange in Chemical Kinetics, Princeton University Press, Princeton, N.J., 1955 trans. from Russian by Thanel. 

Condensation of pure vapors under laminar conditions in the presence of noncondensable gases, interfacial resistance, superheating, variable properties, and diffusion has been analyzed by Minkowycz and Sparrow [Int. ]. Heat Ma.s.s Tran.sfer, 9, 1125 (1966)]. 

The stagnant-film model discussed previously assumes a steady state in which the local flux across each element of area is constant i.e., there is no accumulation of the diffusing species within the film. Higbie [Trans. Am. Jn.st. Chem. Eng., 31,365 (1935)] pointed out that industrial contactors often operate with repeated brief contacts between phases in which the contact times are too short for the steady state to be achieved. For example, Higbie advanced the theory that in a packed tower the liquid flows across each packing piece in laminar flow and is remixed at the points of discontinuity between the packing elements. Thus, a fresh liquid surface is formed at the top of each piece, and as it moves downward, it absorbs gas at a decreasing rate until it is mixed at the next discontinuity. This is the basis of penetration theoiy. 

With regard to the liqiiid-phase mass-transfer coefficient, Whitney and Vivian found that the effect of temperature upon coiild be explained entirely by variations in the liquid-phase viscosity and diffusion coefficient with temperature. Similarly, the oxygen-desorption data of Sherwood and Holloway [Trans. Am. Jnst. Chem. Eng., 36, 39 (1940)] show that the influence of temperature upon Hl can be explained by the effects of temperature upon the liquid-phase viscosity and diffusion coefficients. 

Principles of Rigorous Absorber Design Danckwerts and Alper [Trans. Tn.st. Chem. Eng., 53, 34 (1975)] have shown that when adequate data are available for the Idnetic-reaciion-rate coefficients, the mass-transfer coefficients fcc and /c , the effective interfacial area per unit volume a, the physical solubility or Henry s-law constants, and the effective diffusivities of the various reactants, then the design of a packed tower can be calculated from first principles with considerable precision. 

For gas-phase diffusion in small pores at lowpressure, the molecular mean free path may be larger than the pore diameter, giving rise to Knudsen diffusion. Satterfield (Ma.s.s Tran.sfer in Heterogeneous Catalysis, MIT, Cambridge, MA, 1970, p. 43), gives the following expression for the pore dimisivity ... 

Azobenzene [103-33-3] M 182.2, m 68", pK 2.48. Ordinary azobenzene is nearly all in the transform. It is partly converted into the cw-form on exposure to light [for isolation see Hartley J Chem Soc 633 1938, and for spectra of cis- and /ran5-azobenzenes, see Winkel and Siebert Chem Ber 74B 6707947]. trans-Azobenzene is obtained by chromatography on alumina using 1 4 benzene/heptane or pet ether, and crystd from EtOH (after refluxing for several hours) or hexane. All operations should be carried out in diffuse red light or in the dark. 

Deuterium [7782-39-0] M 4. Passed over activated charcoal at -195° [Maciver and Tobin J Phys Chem 64 451 I960], Purified by diffusion through nickel [Pratt and Rogers, J Chem Soc, Faraday Trans 192 1589 1976], Always check deuterium for radioactivity to find out the amount of tritium in it (see D2O below). 

Hydrated bilayers containing one or more lipid components are commonly employed as models for biological membranes. These model systems exhibit a multiplicity of structural phases that are not observed in biological membranes. In the state that is analogous to fluid biological membranes, the liquid crystal or La bilayer phase present above the main bilayer phase transition temperature, Ta, the lipid hydrocarbon chains are conforma-tionally disordered and fluid ( melted ), and the lipids diffuse in the plane of the bilayer. At temperatures well below Ta, hydrated bilayers exist in the gel, or Lp, state in which the mostly all-trans chains are collectively tilted and pack in a regular two-dimensional... 

Glueckauf E. (1955) Theory of Chromatography Part 10 - Formula for Diffusion into Spheres and Their Application to Chromatography, Trans. Faraday Soc. 51 1540-1551... 

Arnold. J.H. Trans. Am. Inst. Chem. Eng. 40 (1944) 361, Studies in diffusion Ilf, Steady-state vaporization and absorption,... 

Danckwkrts. P. V. Trans. Faraday Soc. 46 (1950) 300. Absorption by simultaneous diffusion and chemical reaction. 

Takagi, T. and Xu, Z., Numerical analysis of hydrogen-methane diffusion flames (effects of preferential diffusion), Trans. pn. Soc. Mech. Eng.(B), 59, 607, 1993 (in Japanese). 

Combined FLIP images of OH (green) and PLII images of soot (red). The OH is an indication of the diffusion flame around the soot-rich zone. The flame is approaching the combustion chamber wall on the right. (From Dec, J.E. and Tree, D.R., SAE Trans., 110(3), 1599, 2001. With permission.)... 

If the bulk-liquid phase is well mixed and no diffusion occurs in the solid phase, a simple expression relating the solid-phase composition to the fraction frozen can be obtained for the case in which the distribution coefficient is independent of composition and fraction frozen [Pfann, Trans. Am. Inst. Mech. Eng., 194, 747 (1952)]. 

Van Orman J, Saal A, Bourdon B, Hauri E (2002a) A new model for U-series isotope fractionation during igneous proeesses with finite diffusion and multiple solid phases. EOS Trans, Am Geophys Union 83(47) Fall Meet Suppl Abstract V71C-02... 

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