Researchers/research studies solvents

Researchers studying polypeptide and polypeptide hybrid systems have also processed vesicles using two solvents. This method usually involves a common organic solvent that solubilizes both blocks and an aqueous solvent that solublizes only the hydrophilic block. The two solvents can be mixed with the polypeptide or polypeptide hybrid system at the same time or added sequentially. The choice of organic solvent depends heavily upon the properties of the polypeptide material, and commonly used solvents include dimethylformamide (DMF) [46, 59], methanol (MeOH) [49], dimethyl sulfoxide (DMSO) [50, 72], and tetrahydrofuran (THF) [44, 55]. Vesicles are usually formed when the organic solvent is slowly replaced with an aqueous solution via dialysis or removed through evaporation however, some vesicles have been reported to be present in the organic/aqueous mixture [49]. 

A paper contributed by J. E. Desnoyers, R. Beaudoin, C. Roux, and C. Perron described the use of microemulsions as a possible tool for the extraction of oil from tar sands. Using a technique called flow microcalorimetry recently developed at the University of Sherbrooke, these researchers studied the structure and stability of organic microphases in aqueous media. These microphases can be stabilized by surfactants and can dissolve large quantities of oil. In a similar vein, D. F. Gerson, J. E. Zajic, and M. D. Ouchi (University of Western Ontario) described the extraction of bitumen from Athabasca tar sands by a combined solvent-aqueous-surfactant system. 

Volatile ginger oil obtained from steam distillation has been the subject of many research studies (5-12). However, the thermal degradative effects of steam distillation upon volatile and nonvolatile components of ginger were seldom discussed. Recently, Moyler (1) compared the advantages of liquid carbon dioxide extraction over conventional methods such as solvent extraction or steam distillation by showing reconstructed GC chromatograms which clearly displayed the differences. However,quantitative results showing the differences were not mentioned. 

Another weak point of many allelopathic research studies reported in the literature is the lack of proper statistical analysis. Probably the two most critical errors are the lack of proper controls and insufficient replication. Appropriate controls need to be included even when a minimal amount of a solvent [e.g., dimethyl sulfoxide (DMSO), acetone, etc.] is used to solublilize a compound or for extraction of the test plant material. In this situation, it is also helpful to include positive controls (known compounds at similar concentrations) for comparison to the unknown or suspected allelochemicals. As discussed earlier, it is also useful to include various species so that a range of sensitivity to the test material can be observed. For example, a bioassay using seed germination might include lettuce seed, generally a sensitive species, and other species which might vary in response to the allelochemical(s) or extract. Such selection can demonstrate plant... 

In order to conduct research studies on this novel lipid mediator, it is necessary to have available a sufficient quantity of purified, well-defined material. This has not been an easy task, but an approach to preparation of sphingosine-l-P in milligram amounts was outlined by Van Veldhoven et al. (1989). In this procedure, a commercial preparation of sphingosylphospho-choline (which contains a free amine group due to removal of a fatty acyl residue from initial substrate, sphingomyelin) is incubated with phospholipase D in an ammonium acetate buffer at pH 8.0 for 1 hr. An insoluble reaction product is collected and subjected to purification by dissolution in water at room temperature followed by cooling to 4°C. A precipitate forms again and is collected and treated in a similar manner as above except that acetone is used as the solvent. 

Research on solvent based polymer separation processes is by no means in its infancy. One of Ae first studies on mixed plastics was conducted by Sperber and Rosen [24,25] in the mid 1970 s. These investigators used a blend of xylene and cyclohexanone to separate a mixture of polystyrene (PS), poly(vinyl chloride) (PVC), high density polyethylene (HOPE), low density polyethylene (LDPE), and polypropylene (PP) into three separate phases. In adAtion, many United States and foreign patents dating from the 1970 s were granted for the solvent recovery of thermoplastic jwlymers [26-30]. The interest in solvent processes waned in the late 1970 s as the oil crisis eased, but the growing need to develop solutions to Ae solid waste problem has renewed Ae research effort [31-33]. 

I hope that this volume will contribute to the studies of organic chemists in industry and academia and will encourage the pursuit of further research into solvent-free organic synthesis. 

The second report of catalytic enantioselective organolithium additions to the imine group came in 1991 from the laboratories of Itsuno and co-workers [23aj. These researchers studied the addition of -BuLi to AT-(trimethylsilyl)benzalde-hyde imine 5a in the presence of chiral modifiers such as alcohols, diols, and amino alcohols (<1 g of imine, ca. 0.13 M). The chiral ligands used were easily prepared according to literature procedures. The enantiomerically enriched primary amine 6 was obtained in 27-90% yield after appropriate workup, depending on the nature of the chiral ligand and the reaction solvent (Scheme 4). 

The extensive use of liquid water as a solvent and reagent in chemical reactions, the widespread occurrence of water on the planet Earth, and the unique role of water as a biological life-support system combine to make an understanding of the properties of liquid water in terms of structure a matter of central importance to chemistry, the earth sciences and biology. The focus of this chapter is to review recent research studies of the structure of water at ordinary temperature and pressure, and to present an opinion on the state of knowledge about this system considered both as a structural problem in physical chemistry and as a methodological problem in computer simulation of the liquid state. ... 

Research on solvent-free polymer-salt complexes accelerated after the pioneering studies of PEO-alkali metal salt complexes conducted by Armand (7,8) and Wright (9-11). 

Water samples for analysis of EDCs and PPCPs are usually collected in amber glass containers, which have been predeaned with reagent water and organic solvents such as methanol and acetone. Discrete or composite samples are sampled in the research studies, but it is appropriate to collect composite samples if the aim of the study is to evaluate the performance of WWTPs. Twenty-foiu hour-composite samples have often been used to represent samples of the WWTPs. 

When the raw material was switched from corn to molasses, many new patents were issued for the molasses-based fermentation processes, and many newly isolated bacteria for these processes were named in the patents (Beesch 1952). Public culture collections have maintained some of these molasses-fermenting solvent-producing clostridia, most of which were referred to as strains of C. acetobutylicum either hy the culture collections or by the investigators. When research on solvent fermentation became active again in the late 1970s, several strains of C. acetobutylicum from puhhc and private culture collections were extensively studied, and these C. acetobutylicum strains displayed surprisingly different properties (Johnson and Chen 1995 Keis et al. 1995). 

Several research studies have focused on oil yield (Fattori et al., 1988 Bozan and Temelli, 2002 Dunford and Temelli, 1997 Pradhan et al., 2010), fatty acid composition (Chang et al., 2000 Jenab et al., 2006 Soares et al., 2007) and oxidative stability of extracted oils (Przbylski et al., 1998 Jenab et al., 2006) using SC-CO2 when compared to solvent extraction. The extraction of commodity oils is predictable. Oil extraction yields increase with increasing pressure up to a certain pressure, which depends on the extraction temperature and then the yield decreases with increasing pressure. This maximum extraction pressure, which occurs before the observed decline in oil extraction yield, increases with temperature (Jiao et al., 2008 Xu et al., 2008 Ixtaina et al., 2010). 

A selection of an additive would be simplified if theoretical prediction is possible and physical data required to make such prediction are available. The actual advancement of research on solvents and plasticizers does not allow us to predict which polymer will be dissolved by which solvent or plasticizer, but it is possible to predict which solvents/plasticizers will not be capable of dissolving a particular polymer. Some results of similar studies are available for additives discussed here and they provide important insight into the behavior of these substances in multi-component systems as well as showing directions for further studies. 

Injection molded parts are known to degrade under the influence of UV or chemical environment (environmental stress cracking) at certain areas of stress concentration. Release agents may play certain role in these processes because they may help to release part before its core has solidified. Also, uneven distribution of release agent on surface may induce tension into a part skin. Any internal stress potentially increases risk of material degradation, under the influence of radiation or contact with solvents. The essential parameters, which contribute to stress formation, are evaluated in a broad research study. ... 

Initial studies on membrane contactors focused on the absorption process, but this has been extended to solvent regeneration. Only a few research studies have reported their outcomes and comprehensive studies are required in this area because the operation involves high operating temperatures. This is because when operated at higher temperature, both liquid absorbent and membrane properties may be altered. This will affect the membrane stability, thus the membrane becomes susceptible to wetting. 

This thesis describes a study of catalysis of Diels-Alder reactions in water. No studies in this field had been reported at the start of the research, despite the well known beneficial effects of acpieous solvents as well as of Lewis-add catalysts on rate and endo-exo selectivity of Diels-Alder reactions in organic solvents. We envisaged that a combination of these two effects might well result in extremely large rate enhancements and improvements of the endo-exo selectivity. 

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