Additional research directions

Notice that when r=Ro equation (30) recovers the correct form for macroscopic diffusion  

If we introduce at this point (30) into (27), we arrive at an expression which is independent of the trapping radius b  

In addition to the mechanical (rheology and adhesion) or chemical (kinetics) studies that we have briefly examined, the 

What happens to reptation when the chain under consideration is immersed in chemically identical chains with different length This aspect is being systematically studied experimentally, yielding rather subtle theoretical situations. 

The crystallization mechanism of polymers in liquid phase is still controversial, as we mentioned in section 1.1 Faraday Transactions, 1979). Nevertheless, for some fast crystallization kinetics, it is possible for a chain to be extended in the amorphous phase by a sucking process which is directly related to reptation (Klein, 1979). 

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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-... 

Although studies directed at measuring the interaction between diverse types of psychotherapy and different medications are complex, additional research in this area is needed. Such studies offer the methodological sophistication required to understand the complicated relationships between interventions that can substantially affect treatment outcomes. 

Specifically for triazines in water, multi-residue methods incorporating SPE and LC/MS/MS will soon be available that are capable of measuring numerous parent compounds and all their relevant degradates (including the hydroxytriazines) in one analysis. Continued increases in liquid chromatography/atmospheric pressure ionization tandem mass spectrometry (LC/API-MS/MS) sensitivity will lead to methods requiring no aqueous sample preparation at all, and portions of water samples will be injected directly into the LC column. The use of SPE and GC or LC coupled with MS and MS/MS systems will also be applied routinely to the analysis of more complex sample matrices such as soil and crop and animal tissues. However, the analyte(s) must first be removed from the sample matrix, and additional research is needed to develop more efficient extraction procedures. Increased selectivity during extraction also simplifies the sample purification requirements prior to injection. Certainly, miniaturization of all aspects of the analysis (sample extraction, purification, and instrumentation) will continue, and some of this may involve SEE, subcritical and microwave extraction, sonication, others or even combinations of these techniques for the initial isolation of the analyte(s) from the bulk of the sample matrix. 

Additional research with Lemna species has indicated that parameters other than direct growth measurements may be more sensitive In this bioassay. Table VII compares growth and chlorophyll content of L. minor as affected by catechln. Final frond number was inhibited by 1000 pM catechln and stimulated at lower concentrations of 50 and 100 pM. Chlorophyll content on a per-frond basis, however, was consistently Inhibited by catechln and was concentration dependent to 100 pM. 

Anonymous. 2001. Stem Cells Scientific Progress and Future Research Directions. Department of Health and Human Services. Available at http //www.stemcells.nih.gov. (Note this website also provides a number of additional reference materials on the subject of stem cells.)... 

X-ray crystallographic structures of myoglobin and hemoglobin were first completed in 19662 and 19753, respectively. Since then, many other X-ray crystallographic studies of deoxy- and oxy- as well as met-myoglobin and hemoglobin have been carried out.22,24 Additionally, researchers have studied the carbon monoxide bound moieties MbCO and HbCO as well as MbNO. Site-directed mutagenesis of residues near the active sites of Mb and Hb have yielded... 

Therefore, an economic analysis must measure the quality of life of the patient to ensure that the value of the drug incorporates the patient s perspective. Quality of life is a concept that usually incorporates the physical, mental and social well-being of the patient. Initial doubts concerning the ability of schizophrenic patients to provide reliable and valid reports of their own quality of life led to the use of proxies for patient interviews. Caregivers and clinicians were consulted most often. However, recent research has shown that the use of proxies can produce very different results to those derived directly from the patient s responses. In addition, research now indicates that schizophrenic patients are able to provide stable, reliable and valid self-reports of their psychological well-being, health status and subjective evaluation of drug therapies (Awad et al., 1995). 

We intend Reactive Intermediate Chemistry to serve as a free-standing resource to be used by the entire chemical community. It should be especially useful for first or second year graduate students, for whom it could form the basis of a course in reactive intermediate chemistry. To that end, each chapter features a concluding section devoted to a summary of the current situation, as well as a roll call of near-term problems and probable research directions. A list of key reviews and suggestions for additional reading accompanies each chapter. 

The materials studied displayed relatively low glass transition temperatures and therefore poor orientational stability. Future studies should be directed to solving this problem. Additional research is required to improve the efficiency of photoinitiation for materials with strong absorptions in the visible region of the spectrum. Other issues such as strain caused by shrinkage during crosslinking need to be addressed. 

The use of different types of membranes for water production and purification is presented here. Solutions are available for good-quality water production at affordable costs. Important related aspects such as environmental and energy issues are presented. Future directions are reviewed. Additional research is required in order to improve the processes and reduce the cost of water produced. The subject of water is one of the most important subjects that humankind must solve, together with renewable energy and environmental problems. 

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