bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spectroscopic Determination of Caffeine Solubility in Supercritical Carbon Dioxide
Authors: Ebeling H. , Franck E. U. 
Published: July 2012

AbstractThe solubility of caffeine in supercritical carbon dioxide was measured from 50°C to 160°C and with CO2‐densities from 3 mol dm−3 to 15 mol dm−3 (5 MPa to 25 MPa). Gas phase concentrations were derived from the UV‐absorption of caffeine at 273 nm. The high pressure optical cell and additional equipment are described. Results are given as “Enhancement Factors”. Enhancement factors up to 106 were found. The factors increase with solvent density and decrease with temperature at isochoric conditions. Virial coefficients B12 are derived between 323 K and 433 K and also calculated assuming a square‐well interaction potential. In addition the sublimation pressure curve of pure caffeine was determined spectroscopically.
Phase Equilibria Related to Supercritical‐Fluid Solvent Extractions (Invited Lecture)
Authors: Paulaitis M. E. , Kander R. G. , Diandreth J. R. 
Published: July 2012

AbstractProcess concepts for supercritical‐fluid solvent extraction are discussed with emphasis on the fluid‐phase equilibria for ternary and multicomponent mixtures. Experimental data for well‐characterized model systems are presented to illustrate important equilibrium phase behavior. Several existing processes are described to demonstrate the utility of supercritical‐fluid solvents in separation and extraction processes.
Chemical Engineering Applications of Supercritical Solvents (Invited Lecture)
Authors: Peter S. 
Published: July 2012

AbstractThe process conditions of extraction with supercritical solvents are dicussed. Treated are a) extraction of substances from solid materials; b) counter‐current extraction for separating low volatile temperature sensitive substances in presence of an entrainer; c) separation of solids from viscous media under supercritical conditions with respect to all involved components. Also considered are some economical aspects of extraction with supercritical solvents.
Supercritical Fluid Extraction: A Film Demonstration (Invited Lecture)
Authors: Eisenbach Wilhelm 
Published: July 2012

AbstractSome of the phenomena associated with supercritical fluid extraction are discussed and illustrated by a film. A number of isolation techniques to remove the dissolved product from the loaded supercritical phase are presented, special emphases is given to the effect of variation of the isolation techniques when mixtures of homologous compounds are to be fractionated. As an example the separation of eicosapentaenoic acid ethyl ester (C20‐−5) from a mixture of fatty acid ethyl esters from codfish oil which consists of saturated and unsaturated fatty acid ethyl esters from C14to C22containing up to 6 double bonds is discussed.
Applications of Atmospheric Gases in High Pressure Extraction
Authors: Jasper Gährs Hans 
Published: July 2012

AbstractThe paper presents results of solubility measurements as well as extraction experiments using CO2 and mixtures of CO2 with atmospheric gases like N2 or Ar as solvents under high pressures. Influences of additional components to a single component gaseous solvent are discussed with respect to solvent properties and possible new applications of the HPE‐process.
Utilization of Supercritical Fluid Solvent‐Effects in Heterogeneous Catalysis
Authors: Tiltscher H. , Wolf H. , Schelchshorn J. 
Published: July 2012

AbstractComparative studies on fixed‐bed catalytic isomerization of 1‐hexene and disproportionation of 1,4‐diisopropylbenzene were performed under liquid, gaseous or supercritical conditions. The kinetic measurements show that by variation of pressure in the different fluid states catalytic surface reactions as well as mass transfer effects between catalyst and fluid phase and/or transport processes inside porous catalysts can be influenced in a very sensitive way. Conclusions are drawn in view of new possibilities for the direction of yield and selectivity of multiple reactions, for the prolongation of catalyst lifetime, and the study of deactivation mechanisms on heterogeneous catalysts.
Photo‐Chemistry of Colloidal Metal Sulfides 8. Photo‐Physics of Extremely Small CdS Particles: Q‐State CdS and Magic Agglomeration Numbers
Authors: Fojtik A. , Weller H. , Koch U. , Henglein A. 
Published: July 2012

AbstractExtremely small CdS particles were prepared in propanol−2 solution at − 78°C and in aqueous solution in the presence of sodium hexametaphosphate at room temperature. These colloids are colorless. Their UV absorption spectra exhibit several maxima. Aging of the colloids is accompanied by intensity variations in the absorption maxima and by a shift of the onset of absorption to longer wavelengths. These small CdS particles hardly possess semiconductor properties (Q‐state CdS). A semi‐classical treatment of the energies of an electron‐hole pair in these particles yielded the wavelengths of their absorption spectra. At the small particle sizes used, the first excited state was reached by photon‐absorption in the UV, and the second excited state was generally not reached at all. The various maxima in the absorption spectra are explained in terms of a size distribution of the colloids with preferential agglomeration numbers. Reasons for the formation of such a structured size distribution are given. The fluorescence and fluorescence excitation spectra of the small particles were also investigated. Particles below a certain size have only one broad fluorescence band at a much longer wavelengths than the onset of absorption. As the particle size increases, this band is shifted towards longer wavelengths, and finally an additional rather sharp band appears at the threshold of absorption. CdS colloids in the Q‐state can be made which fluoresce as desired anywhere between the red and the blue. Also reported are the first experiments in which the preparation of Q‐type CdS in the solid state is achieved by evaporating the solvent from the colloidal solutions.
Mean Polarizabilities and Second Virial Coefficients of the Gases Ar, CH4, C2H6, C3H8 and C(CH3)4
Authors: Kerl K. , Häusler H. 
Published: July 2012

AbstractMean polarizabilities α0(λ0, T) and second virial coefficients B(T) of the gases Ar, CH4, C2H8, C3H8 and C(CH3)4 are determined from refractive indices measured with an interferometer in the ranges 260 K ≤ T ≤ 366 K, 0 ≤ p ≤ 3 bar of temperature T and pressure p (λ0 = 546.266 nm). The following results are discussed:

α0 depends linearly on T.
For each gas B(T)/Vc respectively B(T)/AR can be fitted best versus (Tc/T)2 by two straight lines, which are different for the ranges Tc < T and Tc > T (Tc = critical temperature, Vc = molar critical volume, AR = 4 πNA α0/3).
In the range T > Tc the straight line is common to all gases, whereas in the range T < Tc the straight lines are different for all gases.
For all gases a linear correlation between α0 respectively AR and Vc exists.
Präzisionsmessungen des Viskositätskoeffizienten von Stickstoff und den Edelgasen zwischen Raumtemperatur und 650 K
Authors: Vogel E. 
Published: July 2012

AbstractThe viscosity coefficients of nitrogen and of the rare gases have been determined at atmospheric pressure and within the temperature range 300 – 650 K using an oscillating‐disk viscometer with small gaps completely made of quartz glass. The results have been compared with direct experimental data as well as some data correlations. At room temperature there are only deviations of ±0.1% between our results and experimental data obtained by Kestin et al. Above room temperature differences between our data and values reported by other workers have been found. Some of them exceed 0.5% or even 1.0% and are larger than the mutual uncertainties of different viscometers. Comparisons with values calculated for XC potentials of neon, argon, and krypton and with results calculated for the extended law of corresponding states of Kestin, Ro, and Wakeham have shown that the uncertainty of our data should be at 600 K ± 0.2 to ±0.3%.
Self‐Diffusion in Water‐Alcohol Mixtures Part II. Water‐Methanol Solutions of LiCl and NaCl
Authors: Hawlicka E. 
Published: July 2012

AbstractUsing radioactive tracers the self‐diffusion coefficients of methanol, DM, and water, Dw, in methanol solutions of LiCl and NaCl at 298.2 K have been measured in the whole range of solvent composition. A significant effect of electrolytes on water self‐diffusion coefficient has been observed. The interrelation between the viscosity of the solution and the component self‐diffusion coefficients in mixed solvent solutions of electrolytes is discussed. The important influence of the nature of anions on the disruption of the solvent structure is pointed out.
Exploring the combinatorial genomic space in Escherichia coli for ethanol tolerance
Authors: Nicolaou Sergios A. , Gaida Stefan M. , Papoutsakis Eleftherios T. 
Published: July 2012

AbstractStrain tolerance to toxic chemicals is desirable for biologically producing biofuels and chemicals. Standard genomic libraries can be screened to identify genes imparting tolerance, but cannot capture interactions among proximal or distant loci. In search of ethanol tolerance determinants, we expanded the genomic space combinatorially by screening coexisting genomic libraries (CoGeLs) of fosmids (large inserts) and plasmids (smaller inserts) under increasing ethanol concentrations. Such screening led to identification of interacting genetic loci imparting ethanol tolerance. One pair of fragments ([galT, galE] and [recA, pncC, mltB]) increased survival under 50 g/L ethanol by 38% when coexpressed, but individually the fragments had no effect. Coexpression of two genomic fragments ([sfsB, murA, yrbA, mlaB, mlaC, mlaD, mlaE, mlaF, yrbG] and [yrbA, mlaB, mlaC]) enhanced Escherichia coli survival to 50 g/L ethanol by up to 115%. A 35‐kb fosmid fragment increased tolerance to 63 g/L ethanol by 160%. While the tolerance levels of these strains compare favorably to or exceed the performance of previously reported engineered strains, more significantly, this study demonstrates that combinatorial library screening and screening fosmid libraries offer new, previously unexplored tools for identifying genetic determinants of ethanol, and by extrapolation, other alcohol tolerance.
Hydride Ligands Make the Difference: Density Functional Study of the Mechanism of the Murai Reaction Catalyzed by [Ru(H)2(H2)2(PR3)2] (R=cyclohexyl)
Authors: Helmstedt Ulrike , Clot Eric 
Published: July 2012

AbstractThe catalytic cycle for the Murai reaction at room temperature between ethylene and acetophenone catalyzed by [Ru(H)2(H2)2(PMe3)2] has been studied computationally at the B3PW91 level. The active species is the ruthenium dihydride complex [Ru(H)2(PMe3)2]. Coordination of the ketone group to Ru induces very easy CH bond cleavage. Coordination of ethylene after ketone de‐coordination, followed by ethylene insertion into a RuH bond, creates the Ruethyl bond. Isomerization of the complex to a RuIVintermediate creates the geometry adapted to CC bond formation. Re‐coordination of the ketone before the CC coupling lowers the energy of the corresponding TS. The highest point on the potential energy surface (PES) is the TS for the isomerization to the RuIVintermediate, which prepares the catalyst geometry for the CC coupling step. Inclusion of dispersion corrections significantly lowers the height of the overall activation barrier. The actual bond cleavage and bond forming processes are associated to low activation barriers because of the presence of hydrogen atoms around the Ru center. They act as redox buffers through formation and breaking of HH bonds in the coordination sphere. This flexibility allows optimal repartition of the various ligands according to the change in stereoelectronic demands along the catalytic cycle.
Two‐Dimensional Oxides: Multifunctional Materials for Advanced Technologies
Authors: Pacchioni Gianfranco 
Published: July 2012

AbstractThe last decade has seen spectacular progress in the design, preparation, and characterization down to the atomic scale of oxide ultrathin films of few nanometers thickness grown on a different material. This has paved the way towards several sophisticated applications in advanced technologies. By playing around with the low‐dimensionality of the oxide layer, which sometimes leads to truly two‐dimensional systems, one can exploit new properties and functionalities that are not present in the corresponding bulk materials or thick films. In this review we provide some clues about the most recent advances in the design of these systems based on modern electronic structure theory and on their preparation and characterization with specifically developed growth techniques and analytical methods. We show how two‐dimensional oxides can be used in mature technologies by providing added value to existing materials, or in new technologies based on completely new paradigms. The fields in which two‐dimensional oxides are used are classified based on the properties that are exploited, chemical or physical. With respect to chemical properties we discuss use of oxide ultrathin films in catalysis, solid oxide fuel cells, gas sensors, corrosion protection, and biocompatible materials; regarding the physical properties we discuss metal‐oxide field effect transistors and memristors, spintronic devices, ferroelectrics and thermoelectrics, and solar energy materials.
Solution and Solid‐State Dynamics of Metal‐Coordinated White Phosphorus
Authors: Mirabello Vincenzo , Caporali Maria , Gallo Vito , Gonsalvi Luca , Gudat Dietrich , Frey Wolfgang , Ienco Andrea , Latronico Mario , Mastrorilli Piero , Peruzzini Maurizio 
Published: July 2012

AbstractThe dynamic behavior in solution of eight mono‐hapto tetraphosphorus transition metal‐complexes, trans‐[Ru(dppm)2(H)(η1‐P4)]BF4 ([1]BF4), trans‐[Ru(dppe)2(H)(η1‐P4)]BF4 ([2]BF4), [CpRu(PPh3)2(η1‐P4)]PF6 ([3]PF6), [CpOs(PPh3)2(η1‐P4)]PF6 ([4]PF6), [Cp*Ru(PPh3)2(η1‐P4)]PF6 ([5]PF6), [Cp*Ru(dppe)(η1‐P4)]PF6 ([6]PF6), [Cp*Fe(dppe)(η1‐P4)]PF6 ([7]PF6), [(triphos)Re(CO)2(η1‐P4)]OTf ([8]OTf), and of three bimetallic Ru(μ,η1:2‐P4)Pt species [{Ru(dppm)2(H)}(μ,η1:2‐P4){Pt(PPh3)2}]BF4 ([1‐Pt]BF4), [{Ru(dppe)2(H)}(μ,η1:2‐P4){Pt(PPh3)2}]BF4 ([2‐Pt]BF4), [{CpRu(PPh3)2)}(μ,η1:2‐P4){Pt(PPh3)2}]BF4 ([3‐Pt]BF4), [dppm=bis(diphenylphosphanyl)methane; dppe=1,2‐bis(diphenylphosphanyl)ethane; triphos=1,1,1‐tris(diphenylphosphanylmethyl)ethane; Cp=η5‐C5H5; Cp*=η5‐C5Me5] was studied by variable‐temperature (VT) NMR and 31P{1H} exchange spectroscopy (EXSY). For most of the mononuclear species, NMR spectroscopy allowed to ascertain that the metal‐coordinated P4 molecule experiences a dynamic process consisting, apart from the free rotation about the MP4 axis, in a tumbling movement of the P4 cage while remaining chemically coordinated to the central metal. EXSY and VT 31P NMR experiments showed that also the binuclear complex cations [1‐Pt]+–[3‐Pt]+ are subjected to molecular motions featured by the shift of each metal from one P to an adjacent one of the P4 moiety. The relative mobility of the metal fragments (Ru vs. Pt) was found to depend on the co‐ligands of the binuclear complexes. For complexes [2]BF4 and [3]PF6, MAS, 31P NMR experiments revealed that the dynamic processes observed in solution (i.e., rotation and tumbling) may take place also in the solid state. The activation parameters for the dynamic processes of complexes 1+, 2+, 3+, 4+, 6+, 8+ in solution, as well as the X‐ray structures of 2+, 3+, 5+, 6+ are also reported. The data collected suggest that metal‐coordinated P4 should not be considered as a static ligand in solution and in the solid state.
Innovative Surfaces to Reduce the Soiling in Food Industry
Authors: Bellmann Cornelia , Calvimontes Alfredo , Caspari Anja , Marx Sandra , Mauermann Marc 
Published: July 2012

AbstractEs hat sich gezeigt, dass Foulingprozesse sehr komplexer Natur sind. Sie werden weitestgehend durch die Wechselwirkungskräfte zwischen der entsprechenden Festkörperoberfläche und den adhärierenden Molekülen bestimmt. In diesem Beitrag werden entsprechend der DLVO‐Theorie van‐der‐Waals‐ und elektrostatische Wechselwirkungen betrachtet, wobei auch die Oberflächentopographie der Festkörperoberfläche mit einbezogen wird. Es kann gezeigt werden, dass eine Vielzahl an Einflussgrößen das Adsorptionsverhalten bestimmt. Mithilfe dieser Ergebnisse können Anforderungen an eine Festkörperoberfläche gestellt werden, die eine Verunreinigung weitestgehend verhindern.
Wood‐Plastic Composites: Rheological Characterization and Filling Behavior during Injection Molding Process
Authors: Kirchhoff Nadine , Schröder Cathrin , Stute Daniel , Moritzer Elmar , Schmid Hans‐Joachim 
Published: July 2012

AbstractWood‐Plastic‐Composite (WPC) zeigen im Vergleich zu reinen Kunststoffen ein sehr unterschiedliches und überaus komplexes Material‐ und Fließverhalten. Letzteres ist für die Verarbeitung der Composite von entscheidender Bedeutung. Im Folgenden werden die Ergebnisse rheologischer Charakterisierungen sowie einiger Untersuchungen zum Füllverhalten im Spritzgießprozess dargestellt. Dabei werden auch auftretende Herausforderungen und mögliche Lösungsansätze diskutiert.
Increased Energy and Material Efficiency of Steelmaking in the Electric Arc Furnace
Authors: Kleimt Bernd , Dettmer Bernd , Haverkamp Vico , Deinet Thomas , Tassot Patrick 
Published: July 2012

AbstractDer Elektrolichtbogenofen ist das wichtigste Verfahren zur Stahlerzeugung über das Recycling von Stahlschrott. Ein erheblicher Teil der Produktionskosten entsteht durch den Verbrauch an elektrischer und chemischer Energie sowie durch die Einsatzstoffe. Die Energie‐ und Materialeffizienz des Verfahrens kann durch eine Reduzierung der thermischen Verluste sowie eine dynamische Prozessführung basierend auf mathematischen Prozessmodellen und einer kontinuierlichen Abgasanalyse erhöht werden. Erste Ergebnisse hierzu werden vorgestellt.
Synthesis of Stable Genipin Derivatives and Studies of Their Neuroprotective Activity in PC12 Cells
Authors: Luo Jun , Wang Rikang , Huang Zhao , Yang Jian , Yao Xinsheng , Chen Heru , Zheng Wenhua 
Published: July 2012

AbstractModifications at C1, C7, C8, and C10 of genipin were conducted, and the neurotrophic effects of all derivatives were studied. Genipin derivatives 1–4 were obtained in mild to high yield. Compounds 1 and 4 are more stable than genipin if exposed to nucleophiles. All the derivatives display higher neurotrophic activities than genipin. Compound 4 is the most active, with the least optimal dose. Both genipin and 4 up‐regulated the activity of nNOS in PC12 cells. The effect of 4 is inhibited not only by 7‐NI, a specific inhibitor of nNOS, but also by L‐NIO, a specific inhibitor of eNOS; in the case of genipin, its effect is only inhibited by 7‐NI. All the results indicate that 4 is a promising lead compound for the development of new drugs in the treatment of neurodegenerative diseases with the ability to address multiple drug targets.
Microstructural and optoelectrical properties of transparent conducting ZnO:Al thin films for organic solar cells
Authors: You Zhong Zhi , Hua Gu Jin , Yong Yang Chun , Jin Hou 
Published: July 2012

AbstractThe Al‐doped zinc oxide (ZnO:Al) thin films were grown on glass substrates by the magnetron sputtering technique. The films were characterized with X‐ray diffractometer, four‐point probe and optical transmission spectroscopy, respectively. The dependence of microstructural, electrical and optical properties on deposition temperature was investigated. The results show that all the films have hexagonal wurtzite structure with highly c‐axis orientation. And the microstrural and optoelectrical properties of the films are observed to be subjected to the deposition temperature. The ZnO:Al film prepared at the deposition temperature of 650 K possesses the best optoelectrical properties, with the lowest electrical resistivity (6.1×10−4 Ω·cm), the highest average visible transmittance (85.3%) and the maximum figure of merit (0.41 Ω−1). The optical energy gap of the films was estimated from Tauc's law and observed to be an increasing tendency with the increment of the deposition temperature. Furthermore, the refractive index of the films was determined by the optical characterization methods and the dispersion behavior was studied by the single electronic oscillator model.
Heterophase states and a bridging phase in (1‐x)BiScO3 − xPbTiO3
Authors: Topolov V. Yu. 
Published: July 2012

AbstractHeterophase ferroelectric solid solutions of (1‐x)BiScO3 − xPbTiO3 are studied near the morphotrpic phase boundary (0.60 ≤ x ≤ 0.64). The role of non‐180° domain types of the P4mm and R3m phases in heterophase structures is studied in the context of the phase content. It is shown that the bridging Cm phase coexists with the adjacent phase (either P4mm or R3m), and different variants of an elastic matching ‘single‐domain Cm phase–polydomain P4mm phase’, ‘single‐domain Cm phase–polydomain R3m phase’ and ‘single‐domain Cm phase–near single‐domain R3m phase’ promote the complete stress relief. Based on these concepts and considering a minimum number of the domain types in the coexisting phases, we find a molar‐concentration dependence of the volume fraction of the Cm phase in the heterophase states. A correlation between the predicted volume fraction of the Cm phase and ratios of its unit‐cell parameters is first revealed. The role of the intermediate R3m phase in the phase sequence R3c − R3m − Pm\documentclass{article}\usepackage{amssymb}\begin{document}\pagestyle{empty}$\overline 3$\end{document}m and in the stress relief at x = 0.60 is discussed. Good agreement between the predicted and experimental data on the phase content is reached near the morphotrpic phase boundary.
Selective Conversion of Furfural to Maleic Anhydride and Furan with VOx/Al2O3 Catalysts
Authors: Alonso‐Fagúndez Noelia , Granados Manuel López , Mariscal Rafael , Ojeda Manuel 
Published: July 2012

AbstractFurfural can be converted into maleic anhydride (73 % yield) through selective gas phase oxidation at 593 K with O2 by using VOx/Al2O3 (10 atV nm−2) as solid catalysts. The use of lower temperatures and/or O2 pressures result in the additional formation of furan (maximum 9 % yield). Mechanistically, furfural (C5H4O2) is oxidized stepwise to furan (C4H4O), 2‐furanone (C4H4O2), and finally, maleic anhydride (C4H2O3). The specific structure of the supported vanadium oxides and reaction conditions (temperature and reactants pressures) all influence furfural oxidation catalysis. We have found that Al2O3‐supported polyvanadates are intrinsically more active (2.70 mmol h−1 g‐at V−1) than monovanadates (VO4) and V2O5 crystals (0.89 and 0.70 mmol h−1 g‐at V−1, respectively) in maleic anhydride and furan formation rates (553 K, 1.6 kPa furfural, 2.5 kPa O2). Our alternative approach enables the use of biomass instead of petroleum to synthesize maleic anhydride and furan from furfural. The potential variety of industrial applications is of enormous interest for the development of future biorefineries.