Transport transverse

The continuous change of flow direction in zig-zag channels can induce secondary flow patterns at sufficiently high Re, which besides diffusion can act as a mixing mechanism. By means of recirculation patterns, material is transported transverse to the flow direction and improves the mixing. 

NMR is an important teclnhque for the study of flow and diflfiision, since the measurement may be made highly sensitive to motion without in any way influencing the motion under study. In analogy to many non-NMR-methods, mass transport can be visualized by imaging the distribution of magnetic tracers as a fiinction of time. Tracers may include paramagnetic contrast agents which, in particular, reduce the transverse... 

Membrane asymmetries in the transverse direction (from one side of the membrane to the other) can be anticipated when one considers that many properties of a membrane depend upon its two-sided nature. Properties that are a consequence of membrane sidedness include membrane transport, which is driven in one direction only, the effects of hormones at the outsides of cells, and the immunological reactions that occur between cells (necessarily involving only the outside surfaces of the cells). One would surmise that the proteins involved in these and other interactions must be arranged asymmetrically in the membrane. 

Proteins that can flip phospholipids from one side of a bilayer to the other have also been identified in several tissues (Figure 9.11). Called flippases, these proteins reduce the half-time for phospholipid movement across a membrane from 10 days or more to a few minutes or less. Some of these systems may operate passively, with no required input of energy, but passive transport alone cannot establish or maintain asymmetric transverse lipid distributions. However, rapid phospholipid movement from one monolayer to the other occurs in an ATP-dependent manner in erythrocytes. Energy-dependent lipid flippase activity may be responsible for the creation and maintenance of transverse lipid asymmetries. 

AT-tubule is a transverse invagination of the sarcolem-ma, which occurs at characteristic sites in animal species and organs, i.e. at the Z-membrane in cardiac ventricle muscle and non-mammalian vertebrate skeletal muscle and at the A-I junction in mammalian skeletal muscle. It is absent in all avian cardiac cells, all cardiac conduction cells, many mammalian atrial cells and most smooth muscle cells. It serves as an inward conduit for the action potential. The surface area in the skeletal muscle can reach 6-8 times that of a cylinder with the same radius. In the T-tubule, Na-channel, Ca-channel and other important channels and transporters can be detected. 

Transmembrane Signaling Transport ATPase Transporter Transposon Transverse Tubule Triazenes... 

Transformations in Hilbert space, 433 Transition probabilities of negatons in, external fields, 626 Transport theory, 1 Transportation problems, 261,296 Transversal amplitude, 552 Transversal vector, 554 Transverse gauge, 643 Triangular factorization, 65 Tridiagonal form, 73 Triple product ensemble, 218 Truncation error, 52 Truncation of differential equations/ 388... 

Boundary layer similarity solution treatments have been used extensively to develop analytical models for CVD processes (2fl.). These have been useful In correlating experimental observations (e.g. fi.). However, because of the oversimplified fiow description they cannot be used to extrapolate to new process conditions or for reactor design. Moreover, they cannot predict transverse variations In film thickness which may occur even In the absence of secondary fiows because of the presence of side walls. Two-dimensional fully parabolized transport equations have been used to predict velocity, concentration and temperature profiles along the length of horizontal reactors for SI CVD (17,30- 32). Although these models are detailed, they can neither capture the effect of buoyancy driven secondary fiows or transverse thickness variations caused by the side walls. Thus, large scale simulation of 3D models are needed to obtain a realistic picture of horizontal reactor performance. 

In the sarcoplasm of resting muscle, the concentration of Ca + is 10 to 10 mol/L. The resting state is achieved because Ca + is pumped into the sarcoplasmic reticulum through the action of an active transport system, called the Ca + ATPase (Figure 49-8), initiating relaxation. The sarcoplasmic reticulum is a network of fine membranous sacs. Inside the sarcoplasmic reticulum, Ca + is bound to a specific Ca -binding protein designated calsequestrin. The sarcomere is surrounded by an excitable membrane (the T tubule system) composed of transverse (T) channels closely associated with the sarcoplasmic reticulum. 

Excluding gold complexes that caimot transverse the membrane such as AuSTm, intracellular gold concentrations must approach equilibrium with extracellular gold concentrations if active transport is not at work. The balance of gold between the environment of a cell and within the cell will depend on the ligands available. 

Sirkar and Hanratty (S13) showed, by means of refined measurements using strip electrodes at different orientations with respect to the mean flow, that transverse velocity fluctuations play a significant part in the turbulent transport very close to the wall, and that the eddy diffusivity may well be dependent on the cube of the distance y+, leading to a Sc1/3 dependence of mass-transfer correlations, which is often found experimentally. 

Dispersion in packed tubes with wall effects was part of the CFD study by Magnico (2003), for N — 5.96 and N — 7.8, so the author was able to focus on mass transfer mechanisms near the tube wall. After establishing a steady-state flow, a Lagrangian approach was used in which particles were followed along the trajectories, with molecular diffusion suppressed, to single out the connection between flow and radial mass transport. The results showed the ratio of longitudinal to transverse dispersion coefficients to be smaller than in the literature, which may have been connected to the wall effects. The flow structure near the wall was probed by the tracer technique, and it was observed that there was a boundary layer near the wall of width about Jp/4 (at Ret — 7) in which there was no radial velocity component, so that mass transfer across the layer... 

Here

l and Dy are the coefficients of hydro-dynamic dispersion (cm2 s-1) in the longitudinal (along the flow) and transverse (across the flow) directions. Parallel equations are written for components w, k, and m, in terms of Cw, Q, and Cm, as defined in the previous section. By these equations, we see that dispersion transports a component from areas of high to low concentration, working to smooth out the component s distribution. 

Only laminar transport processes are considered in the transverse y direction. 

Kroodsma (6) studied the use of a filter to separate the urine and the faeces. The main target is to transport the mixture of faeces and some straw to arable farmers and spread the urine on own farmland. But a side effect of direct separation is a reduction of the emission of odours. This separation system is relative expensive, especially in modem pighouses with transverse channels. For a 500-pig unit the extra investment is at least Dfl. 70,- per pig place. The total annual costs are Dfl. 5,- per pig place. In a pighouse with channels in length this system is cheaper and this difference increases when the house is longer. 

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