Facilitated transport and

Absorption. No studies were located regarding the mechanism of absorption in humans or animals after inhalation, oral, or dermal exposure to diisopropyl methylphosphonate. Both facilitated transport and diffusion through the lipophilic portions of the membrane could be involved in absorption processes. No data were found regarding lipid solubility or partition coefficients. 

In reference to this, it is possible to describe examples of facilitated transport and active transport. 

Johnson, W.P. (2000). Sediment control of facilitated transport and enhanced desorption. J. Environ. Eng., 126, 47-57. 

Johnson, W.P., and Amy, G.L. (1995). Facilitated transport and enhanced desorption of polycyclic aromatic hydrocarbons by natural organic matter in aquifer sediments. Environ. Sci. Technol., 29, 807-817. 

Figure 11.1 Schematic examples of passive diffusion, facilitated transport and coupled transport. The facilitated transport example shows permeation of oxygen across a membrane using hemoglobin as the carrier agent. The coupled transport example shows permeation of copper and hydrogen ions across a membrane using a reactive oxime as the carrier agent...

In carrier-mediated transport studies, two terms are used, namely, facilitated transport and coupled transport. Facilitated transport is generally referred to as the case where the transport mechanism is independent of any other ion, while in case of coupled transport the transport rate of a particular ion is dependent on the concentration of another ion. The mechanism of facilitated transport is shown in Figure 31.3 a, while those of the two different types of coupled transport (cotransport and counter-transport) are schematically explained in Figure 31.3b and 31.3c. In case of cotransport, the metal ion is transferred along with a counter-anion, while simultaneous transport of another ion from receiver phase to source phase occurs in case of counter-transport. 

Figure 1. Schematic representation of facilitated transport and Fickian diffusion...

Facilitated transport (or facilitated diffusion) - Includes pore-facilitated transport and carrier-facilitated transport systems. One notable feature of facilitated transport systems is that even though the driving force is also the process of diffusion and the end result is the same as diffusion, facilitated transport systems speed up diffusion by a factor of up to 10,000,000-fold. 

The slow process of diffusion is insufficient to transport many needed molecules across cellular membranes, so cells have evolved a variety of mechanisms for speeding up diffusion. This process, called facilitated transport, includes pore-facilitated transport and carrier-facilitated transport. It is important to note, however, that though pores or carriers speed the diffusion process, the driving force for each process is still diffusion, with all of its built-in limitations. 

Melck, D., Bisogno, T, De Petrocellis, L, Chuang, H., Julius, D., Bifulco, M., and Di Marzo, V. (1999) Unsaturated long-chain N-acyl-vanillyl-amides (N-AVAMs) vanilloid receptor ligands that inhibit anandamide-facilitated transport and bind to CBl cannabinoid receptors. Biochem Biophys Res Commn. 262 275-284. 

The composition of the lipid itself may influence its transport because ingredients that either lower the surface tension of the sebum or increase its fluid nature (make it less viscous) can facilitate transport and even increase the perception of oiliness. In addition, other ingredients left behind on the hair surface (e.g., conditioning agents) may exacerbate oiliness in an analogous manner. 

The PIM mass transfer process is often referred to as facilitated transport, and it allows transport of the extracted species from a feed solntion with a lower concentration to a receiver solution with a higher concentration. Thus, it is possible to transfer qnantitatively the extracted species from the feed to the receiver solution without using an external force (e.g., pressure, electrical field). It should be pointed out that despite the uphill character of the overall transport between the feed and receiver solutions, the transport of the complex or ion-pair of the extracted species within the manbrane is always downhill, that is, along the corresponding concentration gradient. 

Extraction of metals by the liquid membrane process falls into the category of facilitated transport and any of the complex-ing agents can be employed as metal carrier across the membrane phase. Consider, as an example, a reaction as given by eqn (1) with the corresponding equilibrium constant given by eqn (4)... 

Regarding the thermo-physical properties of GFRP profiles, the following behavioural aspects are outlined (i) reduced self-weight, about four to five times less than that of steel (the main competitor within structural materials), which facilitates transport and handling operations on site (ii) thermal... 

Table 9.4 presents typical ranges of variation for several physical and mechanical properties of FRP bars made of glass (GFRP), carbon (CFRP) and aramid (AFRP) reinforcement. For the typical fibre content, all FRP reinforcing bars present low density, about one-sixth to one-quarter that of steel bars (again, the main competitor), which facilitates transport and... 

Koster R, Wangner T, Delay M, Frimmel FH. Release of contaminants from bottom ashes-coUoid facilitated transport and colloid trace analysis by means of laser-induced breakdown detection (LIBD). In Frimmel FH, von der Kammer F, Flemming H-C (Eds.), Colloidal Transport in Porous Media. Springer, Berlin,... 

A typical process plant can include a large number of pressure vessels completely manufactured and tested in the Supplier s premises and delivered on site as a complete finished item. Exceptionally a large vessel may be delivered in two pieces to facilitate transport and then be welded together on site. This operation would almost certainly be carried out by the supplier s personnel. For pressure vessels the requirements of the concerned authority will be very much to the forefront. There will be a quality file established in the country of manufacture with records of materials used, manufacturing processes, in particular concerning welding, with trace-ability, and the records of inspections and tests carried out. Cold-stamping on the vessel itself and on the name/data plate may be an indication of its conformity and acceptance status. 

The design shall incorporate appropriate features to facilitate transport and handling of fresh fuel, spent fuel and radioactive waste. Consideration shall be given to access to facilities and lifting and packaging capabilities. 

Substances move through cell membranes by diffusion (passive transport), facilitated transport, and active transport. 

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