bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-temperature chemical vapor deposition. An effective tool for the production of coatings
Authors: Wahl G. , Stadel O. , Gorbenko O. , Kaul A. 
Published: October 2007

Abstract
Chemical vapor deposition (CVD) processes have a large throwing power and can operate at atmospheric pressure. Therefore, they are economical for many applications. High-temperature CVD processes give a good control of the crystal structure (e.g., epitaxial layers or other special layer structures) and support diffusion processes. The are used, for example, for the following deposition processes: 1) perovskites, 2) yttrium-stabilized ZrO2 layers as ion conductors or heat barrier coatings, 3) aluminide diffusion coatings in long tubes for corrosion protection, and 4) BN on fibers for fiber-reinforced materials. The special properties of the perovskite CVD are discussed in more detail. These processes are described for small- and large-scale applications. The CVD process is simulated by the computer code Fluent.
Modeling and experimental studies on the effect of thermophysical properties on field-activated combustion synthesis reactions
Authors: Munir Z. A. 
Published: October 2007

Abstract
The influence of thermal and electrical conductivities and relative density on the dynamics of self-sustaining reactions activated by an electric field was investigated by modeling. Under a given field, the variation of the wave velocity and maximum temperature with normalized electrical and thermal conductivities and density exhibited a maximum at an optimum value of each of the three parameters. The results are discussed in terms of a Fourier relationship modified by the Joule heat contribution of the imposed field. A simulation was also made to investigate the configuration of the reaction front in systems that are ignited and sustained by a current. A transition from a volume (uniform) combustion reaction to a wavelike form was found to occur as the sample size is increased. These changes are also attributed to the interrelation between the thermophysical parameters.
Mechanism of Fe(OH)2+(aq) photolysis in aqueous solution(Technical Report)
Authors: Pozdnyakov Ivan P. , Glebov Evgeny M. , Plyusnin Victor F. , Grivin Vyacheslav P. , Ivanov Yuri V. , Vorobyev Dmitry Yu. , Bazhin Nikolai M. 
Published: October 2007

Abstract
Experiments on laser flash photolysis (308 nm) of Fe(OH)2+(aq) complex in aqueous solution with addition of nitrobenzene demonstrate the formation of hydroxyl radical in the primary photochemical process.
Foliar Interception and Retention Values after Pesticide Application. A Proposal for Standardized Values for Environmental Risk Assessment (Technical Report)
Authors: Linders J. , Mensink H. , Stephenson G. , Wauchope D. , Racke K. 
Published: October 2007

Abstract
In performing risk assessments for plant protection products by applicants or regulators in relation to the registration of the products, an important aspect to take into account is the foliar interception and retention of the active substance of the product on the plant. An overview is given of the approaches to this item in several parts of the world. The relevant circumstances and influencing variables, such as growth phase, planting density, and some physicochemical characteristics (e.g., vapor pressure and Henry's coefficient) are dealt with. Finally, a proposal is presented for how to take into account the phenomenon of foliar interception and retention in the initial phase, first tier, of the risk assessment process.
From rotaxanes to knots. Templating, hydrogen bond patterns, and cyclochirality
Authors: Reuter Carin , Schmieder Roland , Vögtle Fritz 
Published: October 2007

Abstract
Rotaxanes of the amide type have been accessible in preparative yields by a variety of reactions. Beneath SN2- and SN2t-mechanisms we developed a synthesis of [2]rotaxanes that comes off a Michael addition. The motif of the attractive interactions between an axle-shaped and a macrocyclic wheel part to form rotaxanes consists of multiple hydrogen bonds in the nonionic strategy (threading), as well as in a new high yield anionic template synthesis (trapping). We introduce new synthetic routes for the preparation of [n]rotaxanes using nonionic as well as anionic templates. Furthermore, we report on the latest results of the statistical synthesis (slipping) by melting together axle and wheel to form rotaxanes. The chiroptical properties of a homologous series of cycloenantiomeric [1]rotaxanes as well as a cyclodiastereomeric [3]rotaxane have been described. The differences in the Cotton effects obtained show that small structural changes have an impact on the chiroptical properties of rotaxanes. The first X-ray structures obtained of cycloenantiomerically chiral amide-based [2]- and [1]rotaxanes as well as of the first topologically chiral amide-based knot compound were solved which show networks of H-bonds between the entities of the rotaxanes and the segments of the knot-shaped molecule. Our investigations in template effects based on hydrogen bonding for the synthesis of supramolecular structures open up a variety of strategies for the preparation of catenanes, rotaxanes andrecentlyeven molecular knots.
Mechanisms and consequences of oxygen transfer reactions
Authors: Beak Peter , Anderson David R. , Jarboe Stephen G. , Kurtzweil Mitchell L. , Woods Keith W. 
Published: October 2007

Abstract
The geometry about oxygen in the transition-state structures for oxygen transfers from a nitrone to phosphorous, from a percarboxylic acid to a carbon­carbon double bond, and from an N-sulfonyl oxaziridine to a carbon­carbon double bond have been evaluated by the endocyclic restriction test. The former can proceed at an oblique angle, while the latter two require a large angle between the entering and leaving groups on oxygen. This information is used to determine the mechanism of the aldehyde-dependent oxygen transfer from molecular oxygen to a carbon­carbon double bond.
Adventures in molecular recognition. The ins and outs of templating
Authors: Sanders Jeremy K. M. 
Published: October 2007

Abstract
Two different approaches are described for the creation of supramolecular systems potentially capable of recognition and catalysis. Using the design approach, we have been able to accelerate and influence two different Diels­Alder reactions within the cavities of porphyrin dimers and trimers; this is templating from the outside inwards. The selection approach is a synthetic chemical attempt to capture some of the key evolutionary features of biological systems: dynamic combinatorial chemistry is used to create equilibrating mixtures of potential receptors, and then a template is used to select and amplify the desired system. Five potential reactions for such dynamic chemistry are discussed: base-catalyzed transesterification, hydrazone exchange, disulfide exchange, alkene metathesis, and Pd-catalyzed allyl exchange, and preliminary templating results (inside outwards) are presented.
Microreactor-controlled selectivity in organic photochemical reactions
Authors: Tung Chen-Ho , Wu Li-Zhu , Zhang Li-Ping , Li Hong-Ru , Yi Xiu-Yu , Song Kai , Xu Ming , Yuan Zhen-Yu , Guan Jing-Qu , Wang Hong-Wei , Ying Yun-Ming , Xu Xiao-He 
Published: October 2007

Abstract
Molecular-sieve zeolites, Nafion membranes, low-density polyethylene films, and mixed surfactant vesicles have been used as microreactors to carry out organic photochemical reactions. The photo-cycloadditions of diaryl compounds with long flexible chains included in NaY zeolite or low-density polyethylene films yield intramolecular photocyclomers to the exclusion of intermolecular products. The photosensitized oxidation of alkenes included in pentasil zeolites or Nafion membranes or vesicles can be directed selectively toward either the singlet oxygen-mediated or the superoxide radical anion-mediated products by controlling the status and location of the substrate and sensitizer molecules in the reaction media. The photo-Fries rearrangement of phenyl phenylacetates included within NaY and pentasil zeolites or Nafion membranes gives either ortho-hydroxyphenones or decarbonylation products depending on the size/shape of the microreactors and the substrate molecules. All these results demonstrate the utility of microreactors to control the product selectivity in organic photochemical reactions.
Carbenium and carbonium ions in liquid- and solid-superacid-catalyzed activation of small alkanes
Authors: Sommer J. , Jost R. 
Published: October 2007

Abstract
Acid-catalyzed hydrocarbon reactions involve by far the largest amount of catalyst and the largest volume of transformation in oil refinery and chemical industry. However, despite the general agreement on the carbocationic nature of the reaction intermediates, the initial steps and the true nature of the cations on the surface are still open to debate. On these points our basic knowledge has gained enormously from landmark experiments in physical organic chemistry with spectroscopic observations using liquid superacids as solvents. As the range of superacidity covers over 11 logarithmic units of the Hammett acidity scale, the mechanistic behavior of small alkanes vary accordingly. This allows for comparison with strong solid acids such as zeolite or others used in industry. Isotopic labeling of the alkane and the acids is a powerful tool used to understand the nature of the intermediates, as well as the reaction mechanism in which carbenium and carbonium ions intervene.
Concepts of metal-mediated methane functionalization. An intersection of experiment and theory
Authors: Schwarz Helmut , Schröder Detlef 
Published: October 2007

Abstract
Concepts for the activation of methane are derived from ion-molecule reactions of mass-selected, ground-state transition-metal cations M+. Elementary steps of industrially important processes are uncovered (e.g., oxygenation of methane or its coupling with carbon dioxide). In addition, the implications of the electronic structures of M(CH2)+ complexes for their reactions with nucleophiles are discussed, and the crucial role of contemporary quantum mechanical calculations in the elucidation of mechanistic details is emphasized.
Analytical advantages of using electrochemistry for atomic spectrometry
Authors: Bulska Ewa 
Published: October 2007

Abstract
Atomic spectrometry and electrochemistry are usually recognized as independent analytical tools used for different purposes. Here, a brief review is given of the advantages of using electrochemistry in the various fields of atomic spectrometry techniques. In the first part, the application of electrochemical preconcentration before the atomic spectrometry will be addressed and exemplified. Electrochemical preconcentration could be used with flame atomic absorption spectrometry (AAS) or graphite furnace AAS as well as with atomic emission plasma sources. The second area of the applications of electrochemistry will be directly focused on the graphite furnace AAS where the electrodeposition onto the graphite surface of the atomizer could be used for both in situ analyte preconcentration or modification of the surface by noble metals.
A glance into the bulk of solvent polymeric pH membranes
Authors: Lindner Ernö , Gyurcsányi Robert E. , Pendley Bradford D. 
Published: October 2007

Abstract
The pH-sensitive chromoionophores brought the dream of the ion-selective membrane scientist close to realization. With the help of these molecules, one can build pH-sensitive, ion-selective electrodes and look into the bulk of solvent polymeric membranes during potentiometric measurements (spectropotentiometry) and image concentration profiles in situ with high spatial and temporal resolution. The combination of electrochemical and optical information helped to interpret non-idealities in the potentiometric responses, suppress or tailor the undesirable transport across sensor membranes, and estimate the residual lifetime of chronically implanted sensors. These novel opportunities provide feedback in membrane optimizations and are expected to lead to sensor systems with picomolar detection limits and superb selectivities.
New developments in anti-HIV chemotherapy
Authors: De Clercq Erik 
Published: October 2007

Abstract
Virtually all the compounds that are currently used, or under advanced clinical trial, for the treatment of HIV infections, belong to one of the following classes: (i) nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs): i.e., zidovudine, didanosine, zalcitabine, stavudine, lamivudine, abacavir, emtricitabine, tenofovir (PMPA), and disoproxil fumarate; (ii) non-nucleoside reverse transcriptase inhibitors (NNRTIs): i.e., nevirapine, delavirdine, efavirenz, and emivirine; and (iii) protease inhibitors (PIs): i.e., saquinavir, ritonavir, indinavir, nelfinavir, and amprenavir. In addition, various other events in the HIV replicative cycle are potential targets for chemotherapeutic intervention: (i) viral adsorption, through binding to the viral envelope glycoprotein gp120; (ii) viral entry, through blockade of the viral coreceptors CXCR4 and CCR5; (iii) virus-cell fusion; (iv) viral assembly and disassembly; (v) proviral DNA integration; and (vi) viral mRNA transcription. Also, new NRTIs, NNRTIs, and PIs have been developed that possess respectively improved metabolic characteristics, or increased activity against NNRTI-resistant HIV strains or, as in the case of PIs, a different, nonpeptidic scaffold. Given the multitude of molecular targets with which anti-HIV agents can interact, one should be cautious in extrapolating from cell-free enzymatic assays to the mode of action of these agents in intact cells.
Continuing evolution of the drug discovery process in the pharmaceutical industry
Authors: Ratti Emiliangelo , Trist David 
Published: October 2007

Abstract
Many early discoveries in the pharmaceutical industry were through serendipity. Later, targets were mainly identified in animals and systematically exploited through the identification of potent and selective molecules. A disease association was normally obtained through the clinical testing of candidate molecules in patients. The technological advances in the last few years offer the possibility of knowing more about the disease, and this is driving the industry toward a disease-based approach where understanding the disease becomes central to the process. This is now possible thanks to the recent explosion in molecular and cellular biology, together with the application of genetics and genomics. New screening technologies have also revolutionized the identification of chemical leads. Now, high-throughput screening allows a wide chemical diversity to be applied in order to obtain tractable leads, which can then be optimized by the medicinal chemist. It is envisaged that these trends of continuously searching for process improvement will continue, being driven by the need to find medicines that add value in treating unmet medical need.
Development of bioreactors for application of biocatalysts in biotransformations and bioremediation
Authors: Burton Stephanie G. 
Published: October 2007

Abstract
Biotransformation systems, whether used for environmentally benign biocatalysis of synthetic reactions, or bioremediation of pollutants, require suitable biocatalysts and suitable bioreactor systems with particular characteristics. Our research focuses on the bioconversion of organic compounds, many of which are industrial residues, such as phenols, poly-aromatic hydrocarbons, heterocyclic compounds, and polychlorinated biphenyls. The purpose of such biotransformations can be twofold: firstly, to remove them from effluents and convert them to less toxic forms, and secondly, to convert them into products with economic value. We conduct research in utilizing various isolated-enzyme and whole-cell biological agents; bioreactors, including novel membrane bioreactors, are used as a means of supporting/immobilizing, and hence applying, these biocatalysts in continuous systems. In addition, the enzyme systems are characterized biochemically, to provide information which is required in modification, adaptation, and scale-up of the bioreactors. The paper summarizes research on application of biofilms of fungal and bacterial cells and their enzymes, including hydrolases, polyphenol oxidase, peroxidase and laccase, in bioreactor systems including continuously operating membrane bioreactors.
Nanostructured amorphous metals, alloys, and metal oxides as new catalysts for oxidation
Authors: Kesavan V. , Dhar D. , Koltypin Y. , Perkas N. , Palchik O. , Gedanken A. , Chandrasekaran S. 
Published: October 2007

Abstract
The oxidation of cyclohexane with molecular oxygen in the presence of isobutyraldehyde catalyzed by nanostructured iron and cobalt oxides and iron oxide supported on titania has been studied. Nanostructured cobalt oxide on MCM-41 is found to be efficient for catalytic aerobic epoxidation of olefins.
Peroxometal-mediated environmentally favorable route to brominating agents and protocols for bromination of organics
Authors: Bora Upasana , Chaudhuri Mihir K. , Dey Deepa , Dhar Siddhartha S. 
Published: October 2007

Abstract
Higher-valent transition metals react with H2O2 to form peroxometallates, thereby activating the coordinated peroxide. Based on the reaction profiles of peroxometal species, environmentally acceptable newer syntheses of tetrabutylammonium tribromide (TBATB), Bu4NBr3, cetyltrimethylammonium tribromide (CTMATB), cetyl(Me)3NBr3, and tetraethyl-ammonium tribromide (TEATB), Et4NBr3, have been developed from the reactions of the corresponding quaternary ammonium bromides with H2O2 and a catalytic amount of vanadium(V) or molybdenum(VI). Other transition metals capable of activating peroxide give similar results. The quaternary ammonium tribromides (QATBs) thus produced, especially TBATB and CTMATB, very efficiently act as clean and selective brominating agents for a variety of organic substrates. Very facile bromination of organic substrates, including aromatics, is also possible by tetrabutylammonium bromide (TBAB) Bu4NBr, either promoted by V2O5­H2O 2 or catalyzed by MoO4
2­­H2 O2. The scope of the protocols has been underscored, and the relevance to green chemistry has been highlighted.
Catalysis for green chemistry
Authors: Clark James H. 
Published: October 2007

Abstract
The use of heterogenization as a method for achieving clean synthesis is discussed. The chemical modification of mesoporous solids can be used to make a range of catalysts, including solid acids and bases, and stable metal complexes for selective oxidations and other reactions. By avoiding an aqueous quench stage in the separation, the heterogenization of catalysts and reagents can lead to substantial reductions in waste produced in organic chemical manufacturing processes.
Rapid screening and combinatorial methods in homogeneous organometallic catalysis
Authors: Loch Jennifer A. , Crabtree Robert H. 
Published: October 2007

Abstract
Methods are discussed for rapid screening of soluble and polymer-bound homo-geneous catalysts for activity. A polymer-bound phosphine library is synthesized, and a modular tridentate pincer CNC bis-carbene Pd complex is described. The possibility of C-bound His in metalloenzymes is raised.
Polymer-metal complexes for environmental protection. Chemoremediation in the aqueous homogeneous phase
Authors: Geckeler Kurt E. 
Published: October 2007

Abstract
The concept of chemoremediation in the liquid homogeneous phase using polymer reagents as a green technology is presented and outlined. It is based on the retention of polymer­metal complexes in aqueous solution according to their molecular size by using membrane filtration. The fundamentals of the metal ion interaction with respect to enrichment and separation procedures are discussed, and the role of polymer­metal complexes is assessed. The formation conditions of these polymer­metal complexes as well as major factors influencing the process are investigated. In addition, recent developments using this method are evaluated, and several application examples are highlighted.
Human exposure to traffic pollution. Experience from Danish studies
Authors: Hertel Ole , Jensen Steen Solvang , Andersen Helle Vibeke , Palmgren Finn , Wåhlin Peter , Skov Henrik , Nielsen Ivan Vejsgaard , Sørensen Mette , Loft Steffen , Raaschou-Nielsen Ole 
Published: October 2007

Abstract
Air pollution may have severe long-term as well as short-term health effects. The determination of possible links between pollution levels and impact on human health is, however, not a straightforward task. A key problem is the assessment of human exposure to ambient pollution levels. In later years, the possible role of particulate pollution as a health hazard has drawn major attention and is, therefore, the subject of research projects in many countries including Denmark. The present paper gives a review of recent and ongoing/planned Danish air pollution exposure studies. Furthermore, key results from Danish studies of ultrafine particles from urban traffic are outlined. The exposure studies show that air pollution models may be strong tools in impact assessment studies, especially when used in combination with personal exposure monitoring and application of biomarkers. Personal exposure measurements in Copenhagen indicate that indoor pollution levels may be very important for the personal exposure to fine fraction particles (PM2.5). Measurements with a differential mobility analyzer (DMA) in Danish urban areas show that number concentrations of ultrafine particles (&lt;100 nm) in busy streets are strongly correlated with classic traffic pollutants such as nitrogen oxides and carbon monoxide. The number concentrations in urban Danish streets have decreased considerably between two campaigns in 1999 and 2000, apparently as a result of reductions in sulfur contents in Danish diesel fuels that took place in July 1999.
Reactivity and selectivity under microwaves in organic chemistry. Relation with medium effects and reaction mechanisms
Authors: Loupy André , Perreux Laurence , Liagre Marion , Burle Karine , Moneuse Michel 
Published: October 2007

Abstract
Typical applications of solvent-free conditions and microwave activation are described. Non-purely thermal specific effects are evidenced and discussed in terms of reaction medium and mechanisms, taking into account the variations in polarity of the systems.
Selective biotransformation reactions on (±)-aryl alkyl ketones, (±)-benzoxazines, and d-arabino- and d-threo-hydroxyalkyltriazoles
Authors: Raunak  , Prasad Ashok K. , Shakil Najam A. , Himanshu  , Parmar Virinder S. 
Published: October 2007

Abstract
The capabilities of porcine pancreatic lipase (PPL), Candida antarctica lipase (CAL), and Candida rugosa lipase (CRL) were evaluated for enantio- and/or regioselective acetylation/deacetylation of (±)-2,4-diacetoxyphenyl alkyl ketones, (±)-4-alkyl-3,4-dihydro-3-hydroxyalkyl-2H-1,3-benzoxazines, and d-arabino and d-threo-polyhydroxyalkyltriazoles in organic solvents. PPL in tetrahydrofuran (THF) exhibited high to moderate enantioselectivity during the deacetylation of (±)-2,4-diacetoxyaryl alkyl ketones and acetylation of (±)-3-hydroxyalkyl-2H-1,3-benzoxazines. Together with enantioselectivity, PPL in THF also showed exclusive regioselectivity for the deacetylation of para-acetoxy over the ortho-acetoxy function, with respect to the nuclear carbonyl group in 2,4-diacetoxyphenyl alkyl ketones. CAL in diisopropyl ether (DIPE) and PPL in THF exhibited exclusive selectivity for the acetylation of primary hydroxyl over secondary hydroxyl group(s) of d-arabino- and d-threo-polyhydroxyalkyltriazoles.