bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecularly imprinted electrochemical sensor for the determination of ampicillin based on a gold nanoparticle and multiwalled carbon nanotube‐coated pt electrode
Authors: Wei Shoulian , Liu Yong , Hua Tao , Liu Ling , Wang Hongwu 
Published: March 2014

ABSTRACTA novel molecularly imprinted electrochemical sensor was developed for the sensitive and selective determination of ampicillin (AMP). The sensor was prepared on a platinum electrode modified with multiwalled carbon nanotubes (MWCNTs), gold nanoparticles (AuNPs), and a thin film of molecularly imprinted polymers (MIPs). MWCNTs and AuNPs were introduced to enhance the sensor's electronic transmission and sensitivity. The molecularly imprinted polymer (MIP) was synthesized using AMP as the template molecule, methacrylic acid as functional monomer, and ethylene glycol maleic rosinate acrylate (EGMRA) as cross‐linker. The performance of the proposed imprinted sensor was investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The results showed that the imprinted film displayed a fast and sensitive response to AMP. Under optimal conditions, response peak current had a linear relationship with the concentration of AMP in the range of 1.0 × 10−8 mol/L to 5.0 × 10−6 mol/L and a detection limit of 1.0 × 10−9 mol/L (S/N = 3). This imprinted sensor was used to detect AMP in food samples with recoveries of 91.4–105%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40613.
A comparative study of ethylene and propylene polymerization over titanium–magnesium catalysts of different composition
Authors: Nikolaeva Marina , Matsko Mikhail , Mikenas Tatiana , Zakharov Vladimir 
Published: March 2014

ABSTRACTNew data on the molecular weight characteristics of polypropylene (PP) and polyethylene (PE) were obtained from the polymerization over supported titanium–magnesium catalysts differing in their compositions (presence and absence of internal and external donors). Internal and external donors were found to affect the molecular weight of polymers in a different manner for ethylene and propylene polymerization. The introduction of the internal donor increases the molecular weight of PP and does not affect the molecular weight of PE. The effect of external donor introduced to catalytic system on the polymer molecular weight depends on catalyst composition: for a catalyst without internal donor, the introduction of the external donor increases the molecular weight of PP and does not affect that of PE. In the case of catalyst with the internal donor, the introduction of the external donor increases the molecular weight of PP and substantially decreases that of PE. The data on polymerization degree of the polymers produced under conditions when chain transfer with hydrogen was the dominant reaction were used to calculate the
values for ethylene polymerization over the catalysts of different composition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40658.
Influence of fillers and bonding agents on the viscoelasticity of highly filled elastomers
Authors: Azoug Aurélie , Nevière Robert , Pradeilles‐Duval Rachel‐Marie , Constantinescu Andrei 
Published: March 2014

ABSTRACTHighly filled elastomers such as solid propellants exhibit a complex nonlinear viscoelastic behavior. This work aimed at determining the influence of binder–filler and filler–filler interactions on the microstructure and the viscoelastic properties of the propellant using a design of experiments method. The influences of the filler fraction and of the filler–binder bonding agents (FBBA) were measured by swelling experiments and prestrained dynamic mechanical analyses. The results showed that FBBA react on the filler surface and concentrate the curing agents in the vicinity of the fillers. The nonlinearity of the viscoelastic behavior originated from filler–filler interactions that created high stress zones between fillers and therefore constrained the movements of the macromolecules of the binder. Filler–binder interactions induced by the FBBA increased the filler effective volume as well as the heterogeneous stress distribution in the microstructure. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2014,131, 40664.
Differential Thermal Analysis under High Pressure I: Investigation of the Polymerisation of Liquid Sulfur
Authors: Kuballa M. , Schneider G. M. 
Published: March 2014

AbstractA DTA apparatus constructed for pressures up to 4000 bar and temperatures to 500°C is described.It was applied to the qualitative and calorimetric investigation of the monomer‐polymer equilibrium in liquid sulfur (commonly called Sλ‐Sμ transition). A resulting polymerisation line determined by the connection of the floor temperatures at different pressures shows only a slight negative pressure dependence; it starts at 159°C at normal pressure and intercepts the melting curve at approx. 155°C and 1300 bar the slope of the P(T)‐curve becoming increasingly steeper.The increase of polymer formation in liquid sulfur at the Sλ‐Sμ transition can be deduced quantitatively from the calorimetric measurements.
Die Katalyse der Isotopenaustauschreaktion HTO + H2= HT + H2O an der intermetallischen Verbindung NiGa
Authors: Best K. J. , Grabke H. J. 
Published: March 2014

AbstractDer Austausch von Tritium in strömenden H2O  H2‐Gemischen nach HTO + H2= HT + H2O wurde an Ni, Fe und Legierungen aus dem Homogenitätsbereich der intermetallischen Phase NiGa bei Temperaturen oberhalb 500°C untersucht. Im Homogenitätsbereich des NiGa zwischen 49 und 56 a/o Ga ändern sich die Fermienergie, die Konzentrationen an Punktfehlstellen und die Enthalpie der Sauerstoffadsorption merklich; der Zusammenhang dieser physikalischen und chemischen Eigenschaften mit den katalytischen Eigenschaften der Verbindung wird diskutiert.Die Abhängigkeit der Reaktionsgeschwindigkeit von der SauerstoffaktivitätpH2O/PH2=a0ergibt Aussagen über das Adsorptionsgleichgewicht H2O = H2+ O(ad) an den untersuchten Metallen. Die Enthalpie und Enthalpie der Sauerstoffadsorption wurden bestimmt. Am Eisen wurden bei hoher Sauerstoffaktivität reversible Änderungen der Oberflächenstruktur (Reliefbildung) und der Kinetik der Oberflächen‐reaktion beobachtet, ähnliche, aber irreversible Änderungen treten beim NiGa auf.
Kinetics of a Simple Charge Transfer Reaction at a Slurry Electrode
Authors: Hurwitz H. D. , Srinivasan S. , Litt M. 
Published: March 2014

AbstractA theoretical treatment is presented for an electrochemical cell in which a suspension of catalytically active particles and fuel stream through the anodic compartment. The overall rate of discharge of the particles at the collector electrode is supposedly controlled either by electrochemical oxydation of chemisorbed species on the particle surface (case of hydrogen reaction) or by charge transfer through a resistance at the contact‐making spot between the collector electrode and the catalyst particle. Special emphasis is given to hydrodynamic determination of collision frequencies with the collector electrode of suspended particles, as a function of their dimension and of the state of turbulency, in order to derive current efficiencies of slurry electrodes under various experimental conditions.
Molekulargewichtsverteilung von Formaldehyd in wäßrigen Lösungen
Authors: Koberstein E. , Müller K.‐P. , Nonnenmacher G. 
Published: March 2014

AbstractZur Entwicklung eines vereinfachten Strukturmodells für die Formaldehydpolymerisation in wäßriger Lösung werden Ergebnisse von 1H‐NMR‐Untersuchungen herangezogen. Es wird gezeigt, daß ein Modell mit nur einer einzigen Gleichgewichtskonstanten die Molekulargewichtsverteilung in wäßrigen Formaldehydlösungen quantitativ beschreibt.
NMR‐spektroskopische Untersuchungen über die Eigenassoziation von Karbonsäuren in inerten Lösungsmitteln I. Iterative Berechnung thermodynamischer Größen für Essigsäure
Authors: Jentschura U. , Lippert E. 
Published: March 2014

AbstractSorgfältig hergestellte Proben erlaubten die Messung der chemischen Verschiebung δ des Essigsäure‐COOH‐PMR‐Signals gegen TMS bis herab zu Essigsäurekonzentrationen c = 2,7 · 10−4 mol/l in Cyclohexan bzw. 6,3 · 10−4 mol/l in Tetrachlorkohlenstoff. Bis herauf zu c ≈︁ 0,04 bzw. 0,06 mol/l hängt ∂ im wesentlichen nur vom Monomer‐Dimer‐Gleichgewicht ab, während bei den Werten c = 0,4 bzw. 0,7 mol/l, bei denen ∂ = f(c) ein Minimum besitzt, auch größere Assoziate (Multimere) eine Rolle spielen. Die Frequenzen vm für das Monomere (mit dvm/dT ≈︁ 0) und vD für das Dimere (mit dvD/dT < 0) werden iterativ bestimmt. Die ermittelten Assoziationskonstanten (T = 300°K) liegen in der Größenordnung 103 < Kc < 104l/mol. Aus deren Temperaturabhängigkeit im Bereich von 300 bis 360°K wird die Assoziationsenthalpie zu — ΔH = (12460 ± 160) bzw. (11350 ± 150) cal/mol bestimmt.Dieser Wert stimmt innerhalb der Fehlergrenzen mit dem IR‐spektroskopischer Arbeiten überein. Widersprüchliche Ergebnisse früherer PMR‐spektroskopischer Untersuchungen werden diskutiert.
Matrix‐Isolation Applied to High‐Temperature and Interstellar Molecules: A Review
Authors: Weltner William 
Published: March 2014

AbstractThe contributions of optical and electron‐spin‐resonance (ESR) spectroscopy at 4 K to the determination of the electronic, vibrational, and magnetic properties of high‐temperature and interstellar molecules are briefly reviewed. The present status of the ground state properties of the transition‐metal oxide, nitride, carbide, and hydride molecules are considered. Other molecules produced by the vaporization of beryllium, carbon, silicon, silicon carbide, boron, and boron carbide are also discussed. Numerous metastable molecules for which spectral data are lacking remain to be detected in interstellar space. It is probable that the role of matrix‐isolation, as exemplified by the identification of the interstellar ethynyl and cyanoethynyl radicals via ESR studies at 4 K, will become increasingly important because of the difficulties in observing many reactive molecules in the gas phase.
Photoemission Studies on Rare Gas Matrices
Authors: Koch E. E. , Nürnberger R. , Schwentner N. 
Published: March 2014

AbstractPhotoelectron energy distribution measurements with synchrotron radiation are very useful for the determination of energy levels and the band structure of pure and doped solid rare gas matrices and for the investigation of energy transfer processes. The band formation in Xe–Ar alloys with varying concentration and energy transfer processes in Xe doped Ar and Ne matrices are described and discussed.
Adsorptions‐ und Grenzflächenverhalten von Gangliosiden an der Phasengrenze Quecksilber/Elektrolyt
Authors: WÖrner M. , Greiner G. , Rau H. , Rahmann H. , Probst W. 
Published: March 2014

AbstractThe behavior of three sialoglycolipids of different polarity (the gangliosides GM1, GD1a, GT1b) have been investigated at the Hg/electrolyte interface by means of ac polarography. In solution the gangliosides exist as micelles. We have determined the dependence of the differential capacity of the electrical double layer on the potential difference across this layer and on pH, temperature and addition of bivalent cations (Ca2+, Mg+). The structure of the double layer varies at different electrode potentials. At anodic potentials specific adsorption of ganglioside clusters with the charged head groups towards the electrode is observed. At about +0.2 V (NHE) a rearrangement, reversion of the molecules and strong adsorption of their nonpolar hydrocarbon chains between +0.1 V and −0.7 V is observed. At the stationary electrode (HMDE) at a potential of about −0.8 V condensation of the clusters to a monolayer is inferred which is destroyed at about −1.2 V, probably with desorption of the gangliosides from the electrode. Ca2+ ions induce increased stability of the monolayer at the electrode, a specific Ca2+‐effect is verified by comparison with Mg2+. The relevance of these findings for biological membranes is discussed.
Local Defect Equilibria: The Conceptual Difficulties in Treating Solid State Reaction Kinetics
Authors: Pfeiffer T. , Schmalzried H. , Ueshima Y. 
Published: March 2014

AbstractFor an AO — BO interdiffusion process a formal analysis is given. The conceptual difficulties in using either structural elements, building units or components in the framework of irreversible thermodynamics are discussed. The matrix of transport coefficients of a n‐component system is evaluated and is transformed into a matrix of diffusivities. The interdiffusion problem has been solved numerically, starting with a set of two coupled diffusion equations. Point defect relaxation during interdiffusion has been taken into account through a quasi‐homogeneous point defect relaxation term. The calculated supersaturation and undersaturation of point defects result in concentration profiles which cannot be normalized with √t. Experiments with the diffusion couple FeO — MnO demonstrate the theoretically predicted behavior and the influence of the cation vacancy relaxation at the sample surface on the concentration profiles.
Influence of Pressure on the Transition Phenomenon in Diluted Solutions of Poly(diacetylenes)
Authors: Hennecke Manfred , Düll Ines , Fuhrmann Jürgen 
Published: March 2014

AbstractHydrostatic pressure in the range from 1 to 3400 bar induces the transition phenomenon in diluted solutions of polydiacetylenes. With respect to the influence of pressure on the absorption bands, the transition was studied by UV spectroscopy. The transition is shown to depend strongly on the hydrogen bonds between the sidegroups. In the case of P‐DDD which is free of H‐bonds, the temperature and pressure effect on the transition is first‐order‐like in that temperature range where no precipitation occurs. Transient processes, except those involving precipitated particles, occur below the experimental time scale of minutes. In P‐4BCMU, a polydiacetylene with H‐bonds between the sidegroups, the pressure‐induced isothermal transient phenomena are slowed down, and exhibit a nonexponential time law. The transition shows a hysteresis in temperature in such a way that the heating branch of the hysteresis loop is remarkably shifted by pressure to higher temperatures whilst the cooling branch remains nearly unshifted. Hydrostatic pressure is shown to give additional information concerning the molecular origin of the transition phenomenon.
Combustion and Diffusion Flames at High Pressures to 2000 bar
Authors: Schilling W. , Franck E. U. 
Published: March 2014

AbstractThe combustion of methane with oxygen in supercritical homogeneous aqueous fluids has been investigated and stationary diffusion flames generated to pressures of 2000 bar. A reaction autoclave with sapphire windows contains high pressure homogeneous mixtures of water and methane to 500°C. A typical mixture composition is 70 to 30 mole percent of H2O and CH4. A quasi‐circular fluid flow permits the steady injection of oxygen through a 0.5 mm nozzle at rates of 1 — 10 mm3 s−1 at constant pressures. — Above 400°C spontaneous ignition of flames occurred. The flames were observed and recorded with microscope and video camera. Emission spectra in the UV‐region were obtained and samples could be taken for analysis. Below about 400°C flame‐less oxidation is detected. The stationary diffusion flames are cone‐shaped and typically about 3 mm high. Flame examples for pressures between 300 and 2000 bar are shown. Preliminary temperatures derived from OH‐spectra are close to 3200 K. — Water can be replaced by argon.
Rheo‐Optical Fourier‐Transform Infrared Spectroscopy of Polymers 14. Segmental Orientation and Strain‐Induced Crystallization of a Poly(Ether Urethaneurea) Elastomer
Authors: Siesler H. W. 
Published: March 2014

AbstractThe versatility and potential of rheo‐optical Fourier‐Transform infrared (FTIR) spectroscopy is demonstrated with reference to the characterization of segmental orientation in a poly(ether urethaneurea) elastomer. The rheo‐optical data show that the soft and hard segments of the polymer deform by different orientation mechanisms. Thus, the soft segments exhibit an almost perfect reversibility of orientation and desorientation in loading and unloading cycles, whereas the deformation of the hard segments is dominated by a significant reorganization of their morphology. Furthermore, rheo‐optical FTIR spectroscopy provided an extremely sensitive tool for detecting the onset, progress and decay of strain‐induced crystallization of the soft segments during the mechanical treatment of the elastomer.
Accurate Measurement of the Melting Line of Methanol and Ethanol at Pressures up to 270 MPa
Authors: Sun T. F. , Schouten J. A. , Trappeniers N. J. , Biswas S. N. 
Published: March 2014

AbstractThe P‐T melting curves of methanol and ethanol have been measured precisely at pressures up to 270 MPa and 200 MPa respectively, using the ultrasonic method developed previously. The accuracy of the experimental melting temperatures is about 0.1 K and of the melting pressures about 0.8 MPa for both liquids. The accuracy of the experimental results, fitted to the Simon‐Glatzel equation, is sufficient for the precise calculation of thermodynamic properties along the melting line.
Thermodynamic Study of the Al + Ga + In System: Comparison Between Experimental Measurements and Values Calculated with the HOCH‐ARPSHOFEN Model
Authors: Girard Claude , Bros Jean Pierre , Hoch Michael 
Published: March 2014

AbstractThe excess functions of formation of the Al + Ga + In liquid system have been calculated from the corresponding binary ones by using the Hoch‐Arpshofen interaction model. These results have been compared to the experimental values deduced from calorimetric and potentiometric measurements. Moreover enthalpies of formation were also compared to those calculated by using two polynomial — Kohler and Colinet — relations. The theoretical critical temperatures of the liquid miscibility gap calculated from the Gibbs free energy values confirm our previous observation: the third metal (Ga) lowers the critical solution temperature; so the critical solution surface has no ternary maximum of tempertur.
The Scaling of Nonequilibrium Fluctuations in Gaseous Thermal Explosions
Authors: Fernández Ariel , Rabitz Herschel 
Published: March 2014

AbstractClosed gaseous systems are considered in contact with a heat bath, undergoing a thermal explosion in the rarified gas regime (0.02–0.06 atm.) where the effect of turbulent fluctuations in temperature and acoustic fields on the reaction rate is negligible. This situation is chosen to elucidate the stochastic nature of the ignition processes. An ensemble of combustion experiments is treated where in some replicas, the explosion is accelerated while in others, it is retarded. The influence of spatially localized temperature inhomogeneities on the stochastic ignition process is examined. The induction period is calculated making use of the time‐dependence of the probability distribution of temperatures over the ensemble. This induction period is identified with the Kramers mean passage time corresponding to a critical fluctuation‐induced diffusion across a barrier in an unsymmetric bistable potential. The potential is determined from the competition between the heat production given by the exothermic reaction and the heat removal process. One of the potential wells corresponds to the stationary combustion regime and the other well, to the explosive regime. The critical fluctuations are confined to a virtual volume corresponding to a hot spot whose size is determined from generalized fluctuation‐dissipation theory. As an example, the experimentally measured induction periods for the explosive decomposition of ethyl azide are found to be in very good agreement with our predictions. This treatment successfully explains the discrepancies which arise for the size‐dependence of the induction period and the Frank‐Kamenetsky constant when comparing results from classical Semenov theory and experimental evidence of premature explosions.
The Formation of Isocyanates on Noble Metals and Supported Noble Metal Catalysts
Authors: Schüth F. , Wicke E. 
Published: March 2014

AbstractThe formation of support‐NCO and noble metal‐NCO groups on oxide supported noble metal catalysts and high area evaporated metal films during the NO/CO reaction was studied by FTIR spectroscopy. With SiO2 and A12O3 as supports the results reported in the literature were essentially reproduced. With TiO2 and ZrO2 absorption bands in the region between 2000 and 2100 cm−1 were detected, which had not been described before. On evaporated metals NCO‐groups could be detected in situ. They are located at 2185 cm−1 for Pd and at 2170 cm−1 for Pt. Based on kinetic measurements the spillover of NCO‐groups from the noble metal to the support is proposed as a mechanism for support‐NCO formation. For this spillover a connection between support and noble metal is necessary, which is formed during hydrogen treatment at elevated temperatures. This connecting species could be a noble metal/support intermetallic phase, as Pd3Ti resp. Pt3T
Thermal Decomposition of Cyanogen Bromide Measured in BrCN/O2/Ar Reaction System by Atomic Resonance Absorption
Authors: Gulati S. K. , Roth P. 
Published: March 2014

AbstractThe thermal decomposition of cyanogen bromide has been measured in the temperature range 1640—2260 K at pressures of about 3.8–4.5 bar using the shock tube technique. Mixtures of BrCN/O2 highly diluted in argon were heated by reflected shock waves and O atom concentrations were monitored in the post shock reaction zone by using Atomic Resonance Absorption Spectroscopy (ARAS). Because of the fast secondary reactions of the dissociation product CN, the rate coefficient for the dissociation of cyanogen bromide could be experimentally determined from the measured O atom concentrations. They are closely fit by the Arrhenius expression:

The present rate coefficient data is in good agreement with the result recommended by Baulch et al. [6]
Cation Membrane Transport: Evidence for Local Validity of Nernst‐Planck Equations
Authors: Ratkje Signe Kjelstrup , Holt Torleif , Skrede Magne Geir 
Published: March 2014

AbstractLocal transport coefficients have been experimentally determined for transport of H+, Na+, H2O and current, and for transport of K+, Sr2+, H2O and current in a cation exchange membrane. Adjacent electrolytes contained 0.03 N solution mixtures of HCl and NaCl, or 0.03 N or 0.01 N solution mixtures of KCl and SrCl2. The fluxes and forces used in the presentation are based on a choice of neutral and independent components of the system. — The concentration dependence of the membrane conductivity and the electric mobility of ions has been described by a model which relates the reduction of one cation mobility to the equivalent fraction of the other cation. The mobility ratio varies between 4 and 15 for uH+/uNa+ and 3 and 6 for uk+/uSr2+. The transference numbers for the monovalent salt system can be predicted within experimental uncertainty limits from this model. Local diffusion coefficients are derived and compared to electric mobilities. The result is that the Nernst‐Planck equation using equal electric and diffusional mobility is valid for all concentrations within ± 10% on the average for both systems. Water transport will modify the Nernst‐Planck flux equations when gradients in chemical potential of water becomes about 10−5 times the gradients in chemical potential of salts. Calculations predict a negligible contribution to the chemical potential gradient of salts from pressure variations in the membrane during interdiffusion. — In total these results make possible a continuous description of membrane transport processes.