Recent Research

Diethyl aryl(chloro)methylenemalonates (1670) were reacted with aniline in the presence of triethylamine at 90°C for 12 hr to give aryl(phenyl-amino)methylenemalonates (1671) in 57-66% yields (90JOC2513). The thermal cyclization of compound 1671 (Ar = 3-furyl) at 250°C gave quinoli-necarboxylate (1672) in 85% yield. The cyclizations of compounds 1671 (Pr = Ph, 3-thienyl) in polyphosphoric acid at 210-230°C for 5 min afforded tetracyclic derivatives (1673) in 50-75% yields. 

Diethyl malonate was reacted with 2,3,4-trifluorophenyl isothiocyanate in the presence of sodium hydride in THF at 5-10°C for 40 min, and then at ambient temperature for 105 min, to give the sodium salt of diethyl (2,3,4-trifluorophenylamino)(mercapto)methylenemalonate. The latter was then treated with l-acetoxy-3-chloroacetone or p-methoxybenzyl 

Dimethyl bis(methylthio)methylenemalonate was reacted with 4-[(2-aminoethylmercapto)methyl]-5-methylimidazole in ethanol and then with methylamine to give bisaminomethylenemalonate (1674) in 15% yield (82AP680). 

Diethyl benzothiazol-2-ylidenemalonate (1675) was prepared in the reaction of diethyl bis(methylthio)methylenemalonate and 2-aminothiophenol in boiling ethanol for 16 hr in 78% yield (90CB541). 

Cyclization of diethyl N-[cyclohepta(6)pyrrrol-2-yl]aminomethylene-malonates (1676), by heating in xylene, t-butylbenzene, or tetralin at reflux temperature, gave cyclohepta[4,5]pyrrolo[l, 2-a]pyrimidine-3-carboxyl-ates (1677) in 46-90% yields (87BCJ1053). Cyclization were also carried out in a mixture of phosphoryl chloride and polyphosphoric acid. While compound 1676 (R = COOEt) gave 1677 (R = COOEt) in 95% yield, the unsubstituted 1676 (R = H) afforded a mixture of 1677 (R = H) and 4-hydroxycyclohepta[4,5]pyrrolo[2,3-b]pyridine-3-carboxylate (1678) in 7% and 48% yields, respectively. The nitrogen bridgehead compound (1677, R = H) could not be transformed into pyridine derivative (1678). 

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Recent research (1995-) has produced at very low temperatures (nanokelvins) a Bose-Einstein condensation of magnetically trapped alkali metal atoms. Measurements [41] of the fraction of molecules in the ground... 

This review has covered many of the essential features of the physical chemistry of nanocrystals. Rather than provide a detailed description of the latest and most detailed results concerning this broad class of materials, we have instead outlined the fundamental concepts which serve as departure points for the most recent research. This necessarily limited us to a discussion of topics that have a long history in the community, leaving out some of the new and emerging areas, most notably nonlinear optical studies [152] and magnetic nanocrystals [227]. Also, the... 

Even if It could be shown that RNA preceded both DNA and proteins in the march toward living things that doesn t automatically make RNA the first self replicating molecule Another possibility is that a self replicating polynucleotide based on some carbo hydrate other than o ribose was a precursor to RNA Over many generations natural selection could have led to the replacement of the other carbohydrate by D ribose giving RNA Recent research on unnatural polynucleotides by Professor Albert Eschenmoser of the Swiss Federal Institute of Technology (Zurich) has shown for example that nucleic acids based on L threose possess many of the properties of RNA and DNA... 

More recent research provides reversible oxidation-reduction potential data (17). These allow the derivation of better stmcture-activity relationships in both photographic sensitization and other systems where electron-transfer sensitizers are important (see Dyes, sensitizing). Data for an extensive series of cyanine dyes are pubflshed, as obtained by second harmonic a-c voltammetry (17). A recent "quantitative stmcture-activity relationship" (QSAR) (34) shows that Brooker deviations for the heterocycHc nuclei (discussed above) can provide estimates of the oxidation potentials within 0.05 V. An oxidation potential plus a dye s absorption energy provide reduction potential estimates. Different regression equations were used for dyes with one-, three-, five-methine carbons in the chromophore. Also noted in Ref. 34 are previous correlations relating Brooker deviations for many heterocycHc nuclei to the piC (for protonation/decolorization) for carbocyanine dyes the piC is thus inversely related to oxidation potential values. 

Because of the unique nature of electron-transfer reactions, these have been of great theoretical interest. More recently, research has centered on a microscopic picture of the electron-transfer reactions and predicting reaction rate constants (5,6). 

EPSRC 1999 Ri.sk As.ses.sment and Management - A Retrospective Evaluation of the EPSRC s Recent Research Portfolio. Swindon Engineering and Physical Sciences Research Council, UK. http //www.epsrc.ac.uk/... 

It may occasion surprise that an amorphous material has well-defined energy bands when it has no lattice planes, but as Street s book points out, the silicon atoms have the same tetrahedral local order as crystalline silicon, with a bond angle variation of (only) about 10% and a much smaller bond length disorder . Recent research indicates that if enough hydrogen is incorporated in a-silicon, it transforms from amorphous to microcrystalline, and that the best properties are achieved just as the material teeters on the edge of this transition. It quite often happens in MSE that materials are at their best when they are close to a state of instability. 

This kind of simulation requires massive computer power, and much of it is done on so-called supercomputers . This is a reason why much recent research of this kind has been done at Los Alamos. In a survey of research in the American national laboratories, the then director of the Los Alamos laboratory, Siegfried Hecker (1990) explains that the laboratory has worked closely with all supercomputer vendors over the years, typically receiving the serial No. I machine for each successive model . He goes on to exemplify the kinds of problems in materials science that these extremely powerful machines can handle. 

Carbon nanotubes have been studied extensively in relation to fullerenes, and together with fullerenes have opened a new science and technology field on nano scale materials. This book aims to cover recent research and development in this area, and so provide a eonvenient reference tool for all researchers in this field. It is also hoped that this book can serve to stimulate future work on carbon nanotubes. 

Lapp, K. and Werneburg, H. 1991. Recent Research Advancing the Development of Standards for Detonation Flame Arresters. Paper presented at the Marichem 91 Conference, December 3-5, 1991, Cologne, Germany. 

Stock, M., and W. Geiger. 1984. Assessment of vapor cloud explosion hazards based on recent research results. 9th Int. Symp. on the Prevention of Occupational Accidents and Diseases in the Chemical Industry, Luzern, Switzerland. 

Recent research on motivation theories has provided more elaborate models of the factors which drive human behavior and has taken into account issues of individual differences and the influence of the social and cultural... 

Previously, the requirements for molecule specifications for geometry optimizations were more stringent, and a large part of learning to perform geometry optimizations consisted of learning how to set them up properly. However, recent research into alternative coordinate systems and optimization procedures has made aU of this unnecessary. This topic is considered in Exercise 3.8 (page 57) see the references for further information. 

J. Loffler and R. Schobect, in Recent Research Developments in Organic, and Bioorganic Chemistry. (S. G. Pandalai, ed.), Vol. 2, p. 17. Transworld Reseach Network, Trivandrum (India), 1998. 

The efficacy of these diuretics led to their extensive use in the clinic, particularly in treatment of hypertension. In theory at least, reduction of the blood volume by diuresis should lead to a lowering of pressure (PV=RT). This expectation was in fact met in actual practice. Recent research does, however, seem to indicate that the thiazides have an antihypertensive effect beyond that explainable by a simple lowering of blood volume. 

Camphene is the only well-recognised terpene which occurs in nature in the solid condition. It occurs, like pinene, in both optically active forms. The constitution of this terpene has been a matter of considerable difference of opinion, and the constitution assigned to it by Semmler based on its similarity to bomylene was thought by many to be finally accepted. Recent researches, however, have clearly established that the formula assigned to it by Wagner is the correct one. 

Recent research has conclusively demonstrated the presence of extremely low levels of tertiary and allylic chlorines in PVC as structural defects [118]. Such chlorines, which are extremely labile, when present in areas of like-charge concentration in the polymer matrix would be more susceptible to breaking from the chain than the ordinary secondary chlorines. 

The titanium complexes of calixarene were obtained by Olmstead et al. [44] and Bott et al. [45], who examined their x-ray characteristics. Recent research in that field has been conducted by Rudkevich et al, [46]. They prepared calix[4]arene-triacids as receptors for lan-tanides. 

Rubber blends with cure rate mismatch is a burning issue for elastomer sandwich products. For example, in a conveyor belt composite structure there is always a combination of two to three special purpose rubbers and, depending on the rubber composition, the curatives are different. Hence, those composite rubber formulations need special processing and formulation to avoid a gross dissimilarity in their cure rate. Recent research in this area indicated that the modification of one or more rubbers with the same cure sites would be a possible solution. Thus, chlorosulfonated polyethylene (CSP) rubber was modified in laboratory scale with 10 wt% of 93% active meta-phenylene bismaleimide (BMI) and 0.5 wt% of dimethyl-di-(/ r/-butyl-peroxy) hexane (catalyst). Mixing was carried out in an oil heated Banbury-type mixer at 150-160°C. The addition of a catalyst was very critical. After 2 min high-shear dispersive melt mix-... 

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