Serial fraction

Jordan KH, Bruner J, Doan M et al. (2000) Automated Plasma Protein Binding Assay Implementation on a Tecan Genesis 150 and and Zymark RapidPlate. Poster presented at the LRIG SouthEast October 25 2000 Judd RL and Pesce AJ (1982) Free drug concentrations are constant in serial fractions of plasma ultrafiltrates. Clin Chem 28 1726... 

In serial fractionation the permeates are filtered subsequently through the next membrane (see Figure 4.10). 400 mL of feed sample are used and 35 mL of each permeate are sampled. The volumes filtered per stage are listed in Table 4.9. 

Figure 4.10 Schematic of serial fractionation through membranes I, 11, 111, IP and P. Five permeates (PI to PS) and five retentates (R1 to BJ) are produced.

Table 4.9 Feed and permeate volumes for each stage of serial fractionation.

In practice, ideal speedups are difficult to achieve, especially if the number of processes is large. One factor that reduces the speedup is the existence in an algorithm of inherently sequential parts of code that cannot benefit from a parallel implementation. An upper bound on the speedup was formulated by Amdahl, who expressed the maximum attainable speedup for a parallel algorithm in terms of the serial fraction, f, of the algorithm... 

The speedup limit of 1// given by Amdahl s law is derived using the assumption that the fraction of serial code is independent of the problem size. It has been argued by Gustafson, however, that the serial fraction is likely to decrease when the problem size increases, and that the definition of the speedup should reflect this. Gustafson expressed the execution time on p processes and on a single process as follows... 

Speedup curves illustrating commonly encountered performance patterns, (a) ideal (b) superlinear speedup with performance degradation due to, e.g., communication overhead or load imbalance (c) logarithmic communication overhead (d) linear communication overhead (e) incompletely parallelized program (serial fraction of 0.025). See text for details. 

We have used expressions involving the latency, a, and inverse bandwidth, /3, to model the communication time. An alternative model, the Hockney model, is sometimes used for the communication time in a parallel algorithm. The Hockney model expresses the time required to send a message between two processes in terms of the parameters Too and ni, which represent the asymptotic bandwidth and the message length for which half of the asymptotic bandwidth is attained, respectively. Metrics other than the speedup and efficiency are used in parallel computing. One such metric is the Karp-Flatt metric, also referred to as the experimentally determined serial fraction. This metric is intended to be used in addition to the speedup and efficiency, and it is easily computed. The Karp-Flatt metric can provide information on parallel performance characteristics that caimot be obtained from the speedup and efficiency, for instance, whether degrading parallel performance is caused by incomplete parallelization or by other factors such as load imbalance and communication overhead. ... 

Thus, even a small fraction of serial code may dramatically reduce the maximum attainable speedup (e.g., / = I /20 limits the maximum speedup to 20). The serial fraction of code can be made essentially zero for quantum chemistry programs developed specifically for parallel machines, even for modestly sized molecules. Once the sequential sections of code have been practically eliminated, load imbalance and communication overhead become the obstacles preventing perfect speedup. In this case, a more sophisticated performance model is needed to predict the actual speedup. 

Soxhlet extraction of the dry gum (250 g) serially with hexanes, ether, and methanol resulted in an activity rich ether fraction (600 mg, dried in vacuo) that was partitioned between CCI4 and 50% aqueous MeOH. The dried aqueous layer (300 mg) was applied directly to droplet countercurrent chromatography (DCC), CgHg/MeOH/CHC /H ... 

Animal infectivity methods Some viruses do not cause recognizable effects in cell cultures but cause death in the whole animal. In such cases, quantification can only be done by some sort of titration in infected animals. The general procedure is to carry out a serial dilution of the unknown sample, generally at ten-fold dilutions, and samples of each dilution are injected into numbers of sensitive animals. After a suitable incubation period, the fraction of dead and live animals at each dilution is tabulated and an end point dilution is calculated. This is the dilution at which, for example, half of the injected animals die. Although such serial dilution methods are much more cumbersome and much less accurate than cell culture methods, they may be essential for the study of certain types of viruses. 

Size exclusion chromatography (SEC), also known as gel permeation chromatography (GPC), was used for the separation and fractionation of macromolecules on an analytical and preparative scale [17]. The separation occurs predominantly by the hydrodynamic volume of the macromolecules in solution, however, in some cases the polarity of the molecules can also influence the retention times. Like HPLC, the SEC technique is generally very reproducible with regard to its elution times (typically < 1 h) and hence can be used for automated synthesis. But because the cost for an automated SEC system is high, it must be considered as a serial separation technique. In addition, larger scale separations > 100 mg, usually require repetitive injection of small aliquots. 

According to Coimbra et solvents play a central role in the majority of chemical and pharmaceutical industrial processes. The most used method to obtain artemisinin (1) from A. annua is through the use of organic solvents such as toluene, hexane, cyclohexane, ethanol, chloroform and petroleum ether. Rodrigues et al described a low-cost and industrial scaled procedure that enables artemisinin (1) enhanced yields by using inexpensive and easy steps. Serial extraction techniques allowed a reduction of 65% in solvent consumption. Moreover, the use of ethanol for compound extraction is safer when compared to other solvents. Flash column pre-purification employing silicon dioxide (Zeosil ) as stationary phase provided an enriched artemisinin (1) fraction that precipitated in hexane/ethyl acetate (85/15, v/v) solution. These results indicate the feasibility of producing artemisinin (1) at final cost lowered by almost threefold when compared to classical procedures. 

Functions of properties such as the viscosity index or the viscosity gravity constant may be useful. However, the values of a function for a series of fractions of the same oil may be of approximately equal magnitude or may not be serial, as illustrated by the viscosity index (Table I). 

Method 625 for Semivolatiles. This method is a solvent extraction method intended to determine as many of the organic semivolatile priority pollutants as possible. To accomplish this, the sample is serially extracted, first at a pH greater than 11 and then at pH 2. Figure 1 shows a flow diagram of the procedure. The two fractions, base-neutrals and acids, are independently determined by using two separate GC columns. The base-neutrals are determined on a 1.8-m X 2-mm i.d. glass column packed with Supelcoport (100-120 mesh) coated with 3%... 

Standing-Crop Particles. Standing-crop, noncolloidal, particulate matter was sampled by using two techniques 1, niskin casts followed by filtration onto track-etched filters and 2, serial sieve fractionation in-line with continuous-flow centrifugation, which enabled the collection of gram quantities of suspended particles. 

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