Research directions

In general, the most difficult problems require the determination of local properties in complex materials and the relating of local properties to bulk properties. Problems of this type are becoming more important in quantum chemistry with its shift from chemical physics (concerned primarily with microscopic properties) towards physical chemistry (concerned more with macroscopic properties), a shift occurring as theoretical methods and computer capabilities improve. 

Of high interest would seem to be improved flux and selectivity through a better polymer. Materials are reported every year with good permeability properties but many studies are carried out with relatively thick dense films on the order of 5 to 50pm. In addition, with CO2 any study with pure gas results has to be discounted until mixed gas results are reported because of CO2 plasticization. Also, thin film permeation properties have been demonstrated as different than those of thick films [37]. 

For commercial membranes to be competitive in natural gas treatment they must be reliably manufactured with an active separation layer on the order of 0.1pm. They also have to be resistant to warm and high pressure operating conditions and mechanically resistant to assembly into modules. These are all significant tasks to engineer and inherent permeability of the polymer is only one of the factors involved. 

The observations that very thin cast films lose permeability over time even without external stress is of interest since the active layers of commercial membranes are also thin films. Our commercial modules are pre-stressed with a pressure test to check integrity and can take months to get from the production floor to the customer. How does this thin 

The material science of long-term membrane compaction in asymmetric membranes is not well reported. This phenomenon has been observed in gas separations including this report, but also in reverse osmosis [6] and organic solvent nanofiltration [38]. How to accurately predict multi-year performance in the field with short-term lab tests is a continuing challenge. 

Since installed membrane systems for natural gas treatment are continuing to increase in scale, strategies that reduce the number of required modules and therefore total system cost continue to be of interest. 

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Beginning in the 1980s research directed toward the isolation of new drugs derived from natural sources identified a family of tumor inhibitory antibiotic substances characterized by novel struc tures containing a C C—C=C—C C unit as part of a nine or ten membered ring With one double bond and two triple bonds (-ene + di- + -yne) these com pounds soon became known as enediyne antibiotics The simplest member of the class is dynemian A most of the other enediynes have even more compli cated structures... 

Aspartame is the market leader among artifi cial sweeteners It is a methyl ester of a dipeptide un related to any carbohydrate It was discovered in the course of research directed toward developing drugs to relieve indigestion... 

Further research directed toward optimizing bleach sequences, as well as development of biotechnologies to produce other enzymes that can directly delignify pulps with high specificity of action, can be expected. 

The last two problems have been realized only recently, and additional progress in these research directions may be expected in the near future. At present it is clear that with the standard geometry approximation all time step limitations below 10 fs can be overcome rather easily. This time step increase gives a substantial net increase in performance compared to conventional MD. The possibility of larger step sizes now looks problematic, although it has been demonstrated for small molecules. Larger steps should be possible, however, with constraints beyond the standard geometry approximation. 

There are two great families of synthetic polymers, those made by addition methods (notably, polyethylene and other polyolefines), in which successive monomers simply become attached to a long chain, and those made by condensation reactions (polyesters, polyamides, etc.) in which a monomer becomes attached to the end of a chain with the generation of a small by-product molecule, such as water. The first sustained programme of research directed specifically to finding new synthetic macromolecules involved mostly condensation reactions and was master-... 

The goal of this book is thus to assess progress in the field, to identify fruitful new research directions, to summarize the substantial progress that has thus far been made with theoretical studies, and to clarify some unusual features of carbon-based materials that are relevant to the interpretation of experiments on carbon nanotubes that are now being so actively pursued. A second goal of this book is thus to stimulate further progress in research on carbon nanotubes and related materials. 

The effectiveness of penicillin in the treatment of infections prompted research directed toward finding new antibiotics with a wider range of antibacterial activity. The cephalosporins are a valuable group of drugp that are effective in the treatment of almost all of the strains of bacteria affected by the penicillins, as well as some strains of bacteria that have become resistant to penicillin. The cephalosporins are structurally and chemically related to penicillin. 

The mechanistic investigations presented in this section have stimulated research directed to the development of advanced ruthenium precatalysts for olefin metathesis. It was pointed out by Grubbs et al. that the utility of a catalyst is determined by the ratio of catalysis to the rate of decomposition [31]. The decomposition of ruthenium methylidene complexes, which attribute to approximately 95% of the turnover, proceeds monomolecularly, which explains the commonly observed problem that slowly reacting substrates require high catalyst loadings [31]. This problem has been addressed by the development of a novel class of ruthenium precatalysts, the so-called second-generation catalysts. 

The research detailed in previous sections outlines productive steps toward increased certainty in global quantification of the effects that climate has on carbon cycle processes. Presented here is a short summary of future research directions. 

Discussion of possible future research directions in the area is welcome. 

At least some of the antioxidant nutrients are essential to human health, and others (such as carotenoids) may be highly beneficial, particularly in preventing cancer (e.g. Block et /., 1992). However, we do not yet know what dietary intakes are optimal. In principle, this could be investigated by varying the dietary intake of antioxidants and measuring free-radical damage in the human body. This is one of our current research directions. 

Field techniques for performing worker exposure/re-entry research direct measurement of exposure... 

This paper describes the initial phase of research directed toward the discovery of compounds produced by soil microorganisms, primarily actinomycetes, having potential for development as herbicides. Our interests include both new compounds, as well as previously known ones having heretofore unrecognized herbicidal properties. 

Liao, B.Q., Kraemer, J.T., and Bagley, D.M., Anaerobic membrane bioreactors Applications and research directions, Critical Reviews in Environmental Science and Technology, 36 (6), 489-530, 2006. 

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