Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Involvement procedures

The Grank-Nicholson implicit method and the method of lines for numerical solution of these equations do not restrict the racial and axial increments as Eq. (P) does. They are more involved procedures, but the burden is placed on the computer in all cases. [Pg.2081]

It can be seen from the previous description that the design of both a cold-feed stabilizer and a stabilizer with reflux is a rather complex and involved procedure. Distillation computer simulations are available that can be used to optimize the design of any stabilizer if the properties of the feed stream and desired vapor pressure of the bottoms product are known. Cases should be run of both a cold-feed stabilizer and one with reflux before a selection is made. Because of the large number of calculations required, it is not advisable to use hand calculation techniques to design a distillation process. There is too much opportunity for computational eiToi. [Pg.137]

Gas thermometers that employ equation (1.10) can be constructed to measure either pressure while holding the volume constant (the most common procedure) or volume while holding the pressure constant. The (pV) product can be extrapolated to zero p. but this is an involved procedure. More often, an equation of state or experimental gas imperfection data are used to correct to ideal behavior. Helium is the usual choice of gas for a gas thermometer, since gas imperfection is small, although other gases such as hydrogen have also been used. In any event, measurement of absolute temperature with a gas thermometer is a difficult procedure. Instead, temperatures are usually referred to a secondary scale known as the International Temperature Scale or ITS-90. [Pg.12]

A similar (although more involved) procedure can be used to obtain the partition function for a nonlinear molecule. The result is... [Pg.539]

Microchemistiy - a branch of analytical chemistry that involves procedures that require handling of very small quantities of materials. Specifically it refers to carrying out various chemical operations (weighing, purification, quantitative and qualitative analysis) on samples ranging from 0.1 to 10 milligrams. (The Condensed Chemical Dictionary 1971). [Pg.127]

Applications to and harvest of major crops such as coffee, bananas, and pineapples frequently involve procedures and equipment for which standard operating procedures have not been written. These must be identified in the planning stage, so that the Study Director or Principal Investigator can write these procedures with sufficient time to allow for review and approval. If a procedure is specific to the trial at hand, the process may be described in an addition or amendment to the protocol, but this still requires QA and management approval. In some cases, SOPs specific to a local crop are maintained at a regional site. SOPs must also be available at the site at which the raw data are archived. [Pg.209]

It is also necessary, from the military point of view, that the insecticides supplied to troops in the field be readily convertible into end-use items. It should not be necessary to go through an involved procedure in preparing insecticides for field utilization. For example, the earliest lots of DDT that were received in the North African theater were of the consistency of beeswax, and were extremely difficult to get into solution. It was necessary to process all this material through meat grinders, of the hamburg variety, requisitioned from the civilian economy before this material could be satisfactorily dissolved in Diesel oil. Such a situation complicates field operations unnecessarily, and should be avoided in the development of future insecticides. [Pg.216]

Preparation of a Rhodium Hydride Catalyst Precursor from Spent Catalyst. If, for whatever reason, none of the reactivation procedures above are suitable, one is faced with the option of returning the catalyst concentrate to a vendor for conversion into a catalyst precursor. If the recovery involves reduction of the catalyst concentrate to a rhodium ash, significant expense is involved. Procedures that avoid rhodium ashing may be more economic. [Pg.36]

The risk-benefit assessments depend on whether the research involves the use of interventions that have the intent and reasonable possibility of providing a benefit to the participant, or whether it only involves procedures for research purposes. In research containing interventions expected to provide direct benefit to the participants, a certain amoxmt of risk is justifiable. In research where no direct benefits are anticipated, the IRB should evaluate whether the risks presented by procedures only to obtain generalized knowledge are ethically acceptable. ... [Pg.434]

Boron-containing natural products are not as rare as once supposed. Traditional methods for the isolation and purification of organic natural product compounds involve procedures that typically result in the hydrolytic removal and loss of boron. Thus only in recent years have significant numbers of boron-containing natural products become recognized. [Pg.20]

Assessment methods that determine mental functioning (attention, orientation, memory, speech, understanding of speech, psychomotor functions) in a simple, practical way are recommended for a rough estimation of the severity of dementia. The best-known instrument is the Mini-Mental State Examination (MMSE. Folstein et al.. 1975), which allows the grading of dementia on a 30-point scale on the basis of a simple 5 10-min examination. Other, rather more involved procedures include the Dementia Rating Scale (DRS) of Mattis (1976) and the Alzheimer Disease Assessment Scale (ADAS) of Rosen et al. (1984). The... [Pg.254]

An alternative to establishing a new mechanism is adopting (without change) an existing mechanism from the literature to model the system of interest. When a literature mechanism is chosen, it is important to make sure that it is reliable under the conditions of interest. This involves procedures similar to those described above, that is, comparison of modeling predictions with global experimental data and refinement of the mechanism, if necessary. The validation procedure is facilitated if a so-called comprehensive mechanism is available. A mechanism is comprehensive if it has been validated over a wide range of conditions. [Pg.568]

It will be almost superfluous to mention that such involved procedures are possible nowadays due to the availability of computerized systems [54, 86—90] which organize the measurements as well as the on-line data analysis. On the other hand, many analytical problems may still be attacked by means of the classical d.c. polarogram and, moreover, many other technical or fundamental improvements of polarographic methods have been introduced during the last decade, as can be inferred from recent textbooks [21, 51). In fact, it is lack of knowledge about theoretical backgrounds of (particular) electrode reactions that hampers the reliable application of electroanalytical techniques, especially in more involved practical systems. [Pg.273]

However, it may happen that a non-linear mechanism cannot a priori be excluded. Therefore we now consider the elaboration of Rct and X for the CECDC mechanism treated in Sect. 4.2.2. It is tedious, but not difficult, to derive from eqn. (123) expressions for the partial derivatives F, O and R in terms of and the mean concentrations c and Cr. It can also be verified that these expressions reduce to simpler ones in the limiting cases for which eqn. (124) holds. The next step is to substitute c 0 and Cr by appropriate functions of c , Cr, and reversible case, this involves procedures similar to those mentioned in Sect. 4.3.1 and one may wonder whether the impedance parameters are of more diagnostic value than the d.c. current itself. [Pg.294]

This, however, is clearly not the only reason for such a problem nor is it the only reason for the inordinately tedious and involved procedures which are often reported and recommended. It is also true that if trace components can be of concern in a sample, then trace components can also be of concern in all the items involved in processing that sample. Thus "other traces" are not necessarily introduced into the system in the same quantity as the sought components. In many cases, they can be expected to exceed that quantity many-fold. As a consequence the sample, as finally prepared for measurement, can almost never be considered as a single, pure component suspended in a single pure matrix. It must still be a highly complex mixture. Were this not so, the elegance of instrumentation and technical training would be a considerable waste since the only need, under those circumstances, would be a precisely sensitive and accurate balance. [Pg.367]

A very different source, vanillin, has also given accurate results. A saturated solution of vanillin is prepared by dissolving vanillin in ethanol and by adding a small portion of this solution to the basic analyte solution, NaOH. This type of olfactory titration is more appealing to students due to the pleasant aroma of the vanillin. Instructors might find this titration more attractive as well since the concentration of the NaOH is only 1M versus the 2 M required to quench the aromas of onions and garlic. A detailed account of the chemistry involved, procedures, and student handouts is available (Neppel et al. 2005). [Pg.216]

The impetus for the development of synthesis and characterization of complexes of lanthanides with organic nitrogen donor ligands is due to the search for more efficient luminescent rare earth compounds. One of the difficulties is the risk of precipitating lanthanide hydroxides in the process of synthesis of lanthanide complexes with organic amines. In the early stages, lanthanide complexes of heterocyclic bases of low basicities were prepared in aqueous alcoholic media [224], In the synthesis section it was appropriately pointed out the need for the anhydrous conditions and involved procedures for the preparation of lanthanide complexes of ligands of non-ionizable nature. Some representative complexes of both aliphatic and aromatic amines are listed in Table 4.19. [Pg.295]

Newton variants are constructed by combining various strategies for the individual components above. These involve procedures for formulating Hk or Hk, dealing with structures of indefinite Hessians, and solving for the modified Newton search direction. For example, when Hk is approximated by finite differences, the discrete Newton subclass emerges.5 91-94 When Hk, or its inverse, is approximated by some modification of the previously constructed matrix (see later), QN methods are formed.95-110 When is nonzero, TN methods result,111-123 because the solution of the Newton system is truncated before completion. [Pg.38]

Solution. An approximate solution could be obtained by inteipolating for values of V at AP = 25 psi and then using two of these values to set up Eq. (38) in the fomi of two equations involving only the two unknowns VF and (AP)l s/a wii. By simultaneous solution, the values of VF and (hP)l s/a wfi could be obtained. The final required area could then be determined directly from Eq. (38). Because this method puts too much reliance on the precision of individual experimental measurements, a more involved procedure using all the experimental data is recommended. [Pg.546]

In general, it will be desired to relate the enhancement factors to the rates of product formation in levels K and L. This requires a rather involved procedure since the level populations rig and change with time, not only by the desired rates rg and r, but also by relaxation, and in principle the set of coupled different equations... [Pg.8]

The synthesis of the first stable compound containing a Bi=Bi double bond, (Tbt)Bi=Bi(Tbt) (Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl), (10), was achieved by a rather involved procedure concerning the deselenation of triselenatribismane with a phosphine reagent." The key intermediate in this synthesis a triselenatribismane. The synthetic procedure continued with the treatment of this intermediate with an excess amount of hexamethylphosphoms triamide and heating for 12h. Finally, the dibismuthene was isolated as deep purple single crystals. This was a significant discovery a homonuclear double bond involving the heaviest stable (i.e. nonradioactive) element on the periodic table. [Pg.5790]

The final required area could then be determined directly from Eq. (38). Because this method puts too much reliance on the precision of individual experimental measurements, a more involved procedure using all the experimental data is recommended. [Pg.546]


See other pages where Involvement procedures is mentioned: [Pg.150]    [Pg.106]    [Pg.66]    [Pg.332]    [Pg.309]    [Pg.759]    [Pg.118]    [Pg.995]    [Pg.8]    [Pg.235]    [Pg.138]    [Pg.264]    [Pg.16]    [Pg.405]    [Pg.584]    [Pg.47]    [Pg.951]    [Pg.176]    [Pg.420]    [Pg.74]    [Pg.470]    [Pg.261]    [Pg.436]    [Pg.665]    [Pg.340]    [Pg.519]    [Pg.179]    [Pg.759]   
See also in sourсe #XX -- [ Pg.100 ]




SEARCH



Electrolytic Procedures Involving Porous Electrodes

General Procedures of Aza MBH Reactions Involving Aliphatic Imines

In Vitro Phototoxicity Testing a Procedure Involving Multiple Endpoints

Investigation procedures, basic involving others

Procedures Involving the 2- and 5-Positions of 4-Thiazolidinone

Safe operating procedures employee involvement

Synthetic procedures involving Grignard reagents

Synthetic procedures involving organolithium reagents

Two-dimensional procedures involving isoelectric focusing

Useful procedures for calculations involving molar concentrations

© 2024 chempedia.info