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Scale-down

Although in teraetion s between vicinal I 4 atom s arc n om in ally treated as non bonded interactions, triost of the force fields treat these somewhat differently from normal 1 5 and greater non-bonded interactions. HyperCbern allows each of these 1 4 non-bonded interactions to be scaled down by a scale factor < 1.0 with AMBHR or OPI-S. bor HIO+ the electrostatic may be scaled and different param eters rn ay be ti sed for I 4 van dcr Waals interactions, fh e. AMBHR force field, for exam pie, n orrn a lly uses a seal in g factor of 0.5 for both van der Waals an d electrostatic interactions. [Pg.182]

Fhe van der Waals and electrostatic interactions between atoms separated by three bonds (i.c. the 1,4 atoms) are often treated differently from other non-bonded interactions. The interaction between such atoms contributes to the rotational barrier about the central bond, in conjunction with the torsional potential. These 1,4 non-bonded interactions are often scaled down by an empirical factor for example, a factor of 2.0 is suggested for both the electrostatic and van der Waals terms in the 1984 AMBER force field (a scale factor of 1/1.2 is used for the electrostatic terms in the 1995 AMBER force field). There are several reasons why one would wish to scale the 1,4 interactions. The error associated wilh the use of an repulsion term (which is too steep compared with the more correct exponential term) would be most significant for 1,4 atoms. In addition, when two 1,4... [Pg.229]

All of this careful addition is to keep the reaction from starting before the bomb is sealed. It is also important to note that the chemist must scale up or scale down the amount of reactants so that the total amount of all the ingredients consumes no less than 90 of the volume space of her particular pipe bomb. Too much head space with its atmospheric air will lower the yield. The bomb is heated in an oil bath or oven at 105-115°C for 18-24 hours and the contents are then distilled with the 1,3 benzodioxole coming over at about 170-175°C with no vacuum, Alternatively, the chemist can only distill off the methanol, wash with dilute NaOH solution and extract with ether, etc. [Pg.216]

Usually, atoms with a vicinal relationship or more are considered to be nonbonded. Sometimes, however, only atoms with a 1-5 relationship are considered to be fully nonbonded and the atoms with a relationship have scaled down nonbonded interactions or are deleted completely from the nonbonded computations, or different parameters are used. [Pg.179]

In general, the larger the pilot unit, the more reliable the pre-dic tion oflarge-scale performance. The pilot unit should be a prototype with all dimensions properly scaled down. [Pg.1768]

Regardless of the machine device, centrifuges are typically maintenance-intensive. Filters can be cheaper in terms of capital and maintenance and should be considered first unless centrifugal equipment already exists. Small facilities (<1000 liters) use filtration, since centrifugation scale-down is constrained by equipment availability. Comparative economics of the two classes of operations are discussed by Datar and Rosen (loc. cit.). [Pg.2058]

Once a plant is built, the conditions of agitation, aeration, oxygen transfer, and heat transfer are more or less set, and sterilization cycles are defined. Those environmental conditions achievable in plant-scale equipment should be scaled down to the pilot plant and laboratoiy equipment (shaken flasks) to insure that results can be translated. [Pg.2141]

The moduli of wood can be understood in terms of the structure. When loaded along the grain, the cell walls are extended or compressed (Fig. 26.5a). The modulus E ,ll of the wood is that of the cell wall, E, scaled down by the fraction of the section occupied by cell wall. Doubling the density obviously doubles this section, and therefore doubles the modulus. It follows immediately that... [Pg.282]

In Figure 1.1.1 a,b an example is shown for scale-down to experimental conditions for the hydrogenation of crotonaldehyde to butanol ... [Pg.6]

Figure 1.3.1 a Scale-down of commercial catalytic converters. [Pg.10]

Figure 1.3.2 gives another perspective for scale-down to recycle reactor studies. In this actual case, after preliminary studies in a recycle reactor, a 5-stage adiabatic reactor was envisioned (Betty 1979.) Scaling down the proposed commercial reactor, a 3 diameter tube was designed with elaborate temperature compensation (heating and insulation) for pilot-plant studies (Betty 1968, 1969.) Small squares in the proposed reactor represent side views of cylindrical catalyst cutouts for the recycle reactor... [Pg.13]

Study. Their location represents the range of the conditions that should be used in a statistically designed set of experiments for kinetic studies and not actual conditions at the particular location. This way, the same flow is again maintained on all three scales and the troublesome effect of changing flow conditions on scale-up can be eliminated. The proposed idea, for scale-up by scale-down from the view point of the catalyst, was proven to be effective in many industrial projects. [Pg.14]

Figure 2.3.1 (Wachtel, et al, 1972) shows the ARCO reactor that tried to simulate the real reaction conditions in a fluid cracking unit. This was a formal scale-down where many important similarities had to be sacrificed to get a workable unit. This unit was still too large for a laboratory study or test unit, but instead was pilot-plant equipment that could still give useful empirical results Since this serves a very large industry, it may pay off to try it, even if it costs a lot to operate. Figure 2.3.1 (Wachtel, et al, 1972) shows the ARCO reactor that tried to simulate the real reaction conditions in a fluid cracking unit. This was a formal scale-down where many important similarities had to be sacrificed to get a workable unit. This unit was still too large for a laboratory study or test unit, but instead was pilot-plant equipment that could still give useful empirical results Since this serves a very large industry, it may pay off to try it, even if it costs a lot to operate.
The present author was worried about the lack of knowledge concerning the quality of the kinetic models used in the industry. A model is by definition a small, scaled-down imitation of the real thing. (Men should remember tliis when their mothers-in-law call them model husbands.) In the industry all we require from a kinetic model is that it describe the chemical rate adequately by using traditional mathematical forms (Airhenius law, power law expressions and combinations of these) within the limits of its applications. Neither should it rudely violate the known laws of science. [Pg.117]

Professional judgment should be exercised when planning site activities and to document decisions. HAZWOPER is a performance-based standard that emphasizes hazard analyses at all stages. It encourages the development of programs that match the anticipated risk for each work activity. Eor example, professional judgment is used to decide if a comprehensive HASP or a scaled-down version is required for activities with little possibility to cause significant exposure. [Pg.38]

There is no other facet where thin-layer chromatography reveals its paper-chromatographic ancestry more clearly than in the question of development chambers (Fig. 56). Scaled-down paper-chromatographic chambers are still used for development to this day. From the beginning these possessed a vapor space, to allow an equilibration of the whole system for partition-chromatographic separations. The organic mobile phase was placed in the upper trough after the internal space of the chamber and, hence, the paper had been saturated, via the vapor phase, with the hydrophilic lower phase on the base of the chamber. [Pg.124]

A centrifuge on a crystallization process plant is to be scaled down for tests. If the plant centrifuge is 1.0 m diameter and rotates at 25 Hz at what speed should a 100 mm laboratory centrifuge run if it is to duplicate plant conditions ... [Pg.109]

For a complete optimization of all factors, the above-described procedure is not practical. In order to perform this rapidly, parallel synthesis and screening techniques must be developed. These can consist of a scaled-down version of the MIPs in vials that can be handled automatically and analyzed in situ (Fig. 6-13) [85, 86]. [Pg.176]

Hotter and Balannec published one of the first real proposals to use SMB as a production tool for the pharmaceutical industry, and thus to scale down a process already used on a production scale [29]. The first commercially available plant (Licosep) SMB system was offered by Separex in 1991 and was exhibited for the first time in June 1991 during the Achema Exhibition. The system consisted of 24 stainless steel columns with adjustable lengths between a few centimeters up to almost 1 meter, HPLC pumps, and mulitpositional valves. To improve the robustness of the system, a rotary valve replaced two-way valves and the pumps were modified. [Pg.257]

Benzothiadiazole 1,1-dioxide can be conveniently assayed and characterized without isolation by forming its adduct with cyclopentadiene.5 The following procedure illustrates characterization, for assay the same procedure can be applied to an aliquot, with all amounts scaled down in proportion. The dried ether extract of 1,2,3-benzothiadiazole 1,1-dioxide prepared from 1.43 g (0.0080 mole) of sodium 2-aminobenzene-sulfinate is concentrated to about 20 ml at 0°, and 20 ml. of acetonitrile at —20° is added. Twenty milliliters of cold, freshly prepared cyclopentadiene6 is added The mixture is kept overnight at —10° to 0°. Solvent and excess cyclopentadiene are removed by evaporation at 0° under reduced pressure to leave 1.20-1.28 g. (64-68% based on sodium 2-aminobenzenesulfinate) of crude 1-1 adduct, mp. 87° (dec.). For purification it is dissolved in 20 ml. of methylene chloride, 70 ml. of ether is added, and the solution is kept at —70°. Adduct decomposing at 90° crystallizes recovery is about 75%. From pure, crystalline 1, 2, 3-benzothiadiazole 1,1-dioxide the yield of adduct is 92-98%. [Pg.8]


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Scaling down

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