Maximum surface area

Fiber dimensions have been studied for hemodialysis. When blood is circulated through the fiber lumen (m vivo), a significant reduction in apparent blood viscosity may occur if the flow-path diameter is below 100 p.m (11). Therefore, current dialy2ers use fibers with internal diameters of 180—250 p.m to obtain the maximum surface area within a safe range (see Dialysis). The relationship between the fiber cross section and the blood cells is shown in Figure 5. In many industrial appUcations, where the bore fluid is dialy2ed under elevated pressure (>200 kPa or 2 atm), fibers may burst at points of imperfection. Failure of this nature is especially likely for asymmetric fibers that display a large number of macro voids within the walls. 

Cell Assembly. The methods for cell assembly, starting with the processed plaques depend on whether the cells are to be vented or sealed. For vented cells, processed plaques are usually compressed to 85 —90% of their processed thickness allowing sufficient porosity for electrolyte retention and strengthening the plate stmcture. For sealed cells, sizing of the negative plaques is usually avoided because maximum surface area is important to oxygen recombination. 

Subcatchment 057 (Ebro River) This catchment is located at the headwaters of the Ebro River basin, and it feeds the Embalse del Ebro reservoir, the largest of the basin (E801, built in 1952, with 62.50 km2 of maximum surface area and a capacity of 540 x 106 m3). Because of its size, this reservoir plays a major role in downstream streamflows. 

Measurements of pressure-area (jc-A) isotherms and transfers of monolayers on a substrate were carried out by using a computer-controlled film balance system (San-Esu Keisoku, Co., Fukuoka, FSD-20). Maximum surface area on the trough was 475 X 150 mm2. The trough surface and the moving barrier were coated with Teflon, and the subphase was temperature-controlled with a thermostat (20 0.5 °C). The concentration of lipid solutions was 1 mg/ml and the spreading amount of lipid solutions was 50 - 150 pi. After solvent evaporation, the monolayer was compressed at the speed of 0.60 cm2 s-i. Measurements of n-A isotherms and transfers of monolayer on a QCM substrate were performed automatically with the usual manner [26,27]. 

The sample used by Naono et al. (1982) was a non-porous one (based on a t-plot) (Fig. 14.8) with a BET surface area of 22 m g . It developed a maximum surface area of 178 m g at 200 °C due to the formation of a system of slit-shaped pores ca. one nm wide (see Fig. 14.2 c). During this process, a contraction of ca. 30% occurred along [100] and [010], but not along [001], i.e. not along the tunnels. With increasing temperature, the pores widened to mesopores and irregular macropores. The surface area of the hematite that finally formed at 500 °C was only 23 m g . ... 

Similarly, we can ask what would be the best catalyst for hydrogenating an olefin such as ethylene. Since olefins (alkenes) are more strongly chemisorbed than hydrogen, we choose a metal that just barely chemisorbs H2—this means Co, Rh, Ir, Ni, Pd, or Pt. In practice, nickel is the least expensive choice. Again, it should be finely divided (maximum surface area) for greatest catalytic efficiency and be dispersed on the internal surfaces of a porous support such as alumina with surface area on the order of 200 m2 g 1.8... 

La-hexaaluminates showed higher catalytic activity for all the M-substituted systems with respect to Ba-hexaaluminates.15 27 A similar promoting effect was also found for the composition Sro.gLao.aMn lnO, 15,16,26 which also exhibits the maximum surface area, but only when prepared via hydrolysis of alkoxides. 

ISO previously had two methods for relaxation in compression, a general method using disc test pieces and a method using ring test pieces mainly for tests in liquids. The use of rings reflects the importance of O ring seals and allows the maximum surface area of test piece to be exposed to a test liquid. However, these have now been combined into one standard, IS033845. 

Based upon the theoretical maximum surface area (S01) and the measured surface area (SBEX, cfr. chapter 2), the average coordination number of the primary particles in the aggregate can be calculated as ... 

The pool, as shown in Figure 7.3, has reached its maximum diameter. Therefore, the maximum surface area for evaporation is present. 

Not until 2700 seconds into the event has the discharge rate from the tank decreased to less than the evaporation rate. This means that until this time the pool is continuing to grow, providing the maximum surface area for evaporation. 

For both releases the growth of the pool is shown in Figure 7.9. The figure shows that the surface inside the dike is quickly covered after the release of n-pentane and the maximum surface area for vaporization remains constant for the full 3600 seconds of the incident. 

For denatured proteins (maximum surface area), A = 1.44MA2. 

Chemical desulfurization techniques have a common drawback. They require pulverizing the coke to expose maximum surface area to the reactant(s). Thus, the end product is low sulfur coke with no... 

Vleesschauwer (1970) prepared two series of mesoporous batches of MgO by the heat treatment of crystalline MgCOj (magnesite) and crystalline MgC03.3H20 (nesquehonite). A maximum surface area of about 350 m2 g 1 was obtained by calcination of the latter precursor at 400°C. Although the thermal decomposition of magnesite resulted in the development of lower surface areas (< 140 m2 g 1) the products appeared to have a more uniform mesopore structure. Thus, the nitrogen isotherm determined on a sample calcined for 24 hours at 800°C exhibited a narrow, almost vertical, hysteresis loop at p/p° 0.9. 

Figure 1. Compilation of platinum mass activities as a function of platinum B.E.T. surface area [ ] Watanabe et alJ [0] Buchanan et al.s [ ] Buchanan et al. and [0] Bregoli6. The solid line is 0.6A.m 2 constant specific activity platinum. The broad arrow on the abscissa denotes the maximum surface area for a platinum crystallite when all of the atoms are located at the surface (275 m2 g 1 Pt). Phosphoric acid at 190 °C and 0.9 V vs. hydrogen in the same electrolyte, (a) Data up 210 m2g" Pt. (b) Data below 100m2g Pt m Bregoli6 results on unsupported platinum black.

However, as shown by the curves in Figure 17, bleaching efficiency for Clay C does not attain maximum activity levels untU well after the surface area curve has peaked and started to decline. Note also that both clays achieve practically identical maxima in chlorophyll bleaching efficiencies (albeit requiring different acid dosages), but Clay C only achieves a maximum surface area of about 300 m /g, whereas Clay A achieves a maximum surface area of nearly 500 m /g. Clearly, surface area, per se, is not correlated with chlorophyll adsorption capacity. Similar curves (not shown) were obtained for carotene adsorption (12). 

Generally, one considers that the maximum surface area for the support or catalyst is the best possible arrangement but this is not always true. First it must be recognized that the surface area is not only associated with the external surface of the particle but also with the surface of all the pores within the particles. A particle having small diameter pores will have a higher surface area than one... 

Pd/C means palladium metal dispersed on a charcoal support—usually 5-10% by mass Pd and 90-95% C. It is made by suspending charcoal powder in a PdCl2 solution, and then reducing the PdCb to Pd metal, usually with H2 gas, but sometimes with fomnaldehyde, HCHO (which becomes oxidized to formic acid, HCO2H). The palladium metal precipitates on to the charcoal, which can be filtered off and dried. The fine Pd particles present maximum surface area to the reaction they catalyse and, while Pd is an expensive metal, it is recyclable since the Pd/C is insoluble and can be recovered by filtration. 

The packing promotes good contact between the phases by dividing the two feed streams into many parallel interconnected paths. Ideally, you would like the liquid to flow downward as a thin film over the surface of the packing. This would give the maximum surface area of contact between the gas and liquid. 

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