bluuebunny/crossref_metadata_2025 huggingface dataset:
Biological lability of streamwater fluorescent dissolved organic matter
Authors: Cory Rose M. , Kaplan Louis A.
Published: July 2012

We investigated the biological lability of fluorescent dissolved organic matter (FDOM) from a temperate Piedmont stream. Plug‐flow bioreactors, colonized and maintained with natural stream water, were used to determine the concentrations of stream‐water biodegradable dissolved organic carbon (BDOC) and relative concentrations of FDOM within operationally defined biodegradability classes. Labile molecules with turnover times of hours are metabolized within the stream reach where they originated; semi‐labile molecules with turnover times of days travel out of the reach and are transported downstream before being metabolized; and a more recalcitrant class with a longer but undetermined turnover time flows through the river network without being metabolized. Between 26% and 31% of the DOC was biodegradable, with 8.6% labile and the balance semi‐labile. Humic‐like FDOM was a proxy for more recalcitrant DOM, exhibiting a ± 2% change as a function of increased bioreactor residence time. Humic‐like FDOM represents only the more recalcitrant and perhaps the more hydrophobic constituents and not the ecologically important semi‐labile humic substances within the BDOC pool. Tyrosine‐like and tryptophan‐like FDOM constituents included not only labile DOM, but also semi‐labile, and more recalcitrant moieties. For example, 13% of the tryptophan‐like FDOM was labile, 14% was semi‐labile, and 73% was more recalcitrant, while tyrosine‐like FDOM was 100% biodegraded and the majority (44–69%) was classified as labile. Collectively our results challenge some previous assessments of FDOM lability classifications and highlight the need to connect fluorescence characteristics of DOM to residence times of different carbon pools that spiral through a river network.
Upper body musculoskeletal symptoms of Latino poultry processing workers and a comparison group of Latino manual workers
Authors: Schulz Mark R. , Grzywacz Joseph G. , Chen Haiying , Mora Dana C. , Arcury Thomas A. , Marín Antonio J. , Mirabelli Maria C. , Quandt Sara A.
Published: July 2012

Background

Upper body musculoskeletal injuries are often attributed to rapid work pace and repetitive motions. These job features are common in poultry processing, an industry that relies on Latino immigrants. Few studies document the symptom burden of immigrant Latinos employed in poultry processing or other manual jobs.

Methods

Latino poultry processing workers (n = 403) and a comparison population of 339 Latino manual workers reported symptoms for six upper body sites during interviews. We tabulated symptoms and explored factors associated with symptom counts.

Results

Back symptoms and wrist/hand symptoms lasting more than 1‐day were reported by over 35% of workers. Poultry processing workers reported more symptoms than comparison workers, especially wrist and elbow symptoms. The number of sites at which workers reported symptoms was elevated for overtime workers and workers who spoke an indigenous language during childhood.

Conclusion

Workplace conditions facing poultry processing and indigenous language speaking workers deserve further exploration. Am. J. Ind. Med. 56:197–205, 2013. © 2011 Wiley Periodicals, Inc.
Employer, use of personal protective equipment, and work safety climate: Latino poultry processing workers
Authors: Arcury Thomas A. , Grzywacz Joseph G. , Anderson Andrea M. , Mora Dana C. , Carrillo Lourdes , Chen Haiying , Quandt Sara A.
Published: July 2012

Background

This analysis describes the work safety climate of Latino poultry processing workers and notes differences by worker personal characteristics and employer; describes the use of common personal protective equipment (PPE) among workers; and examines the associations of work safety climate with use of common PPE.

Methods

Data are from a cross‐sectional study of 403 Latino poultry processing workers in western North Carolina.

Results

Work safety climate differed little by personal characteristics, but it did differ consistently by employer. Provision of PPE varied; for example, 27.2% of participants were provide with eye protection at no cost, 57.0% were provided with hand protection at no cost, and 84.7% were provided with protective clothing at no cost. PPE use varied by type. Provision of PPE at no cost was associated with lower work safety climate; this result was counter‐intuitive. Consistent use of PPE was associated with higher work safety climate.

Conclusions

Work safety climate is important for improving workplace safety for immigrant workers. Research among immigrant workers should document work safety climate for different employers and industries, and delineate how work safety climate affects safety behavior and injuries. Am. J. Ind. Med. 56:180–188, 2013. © 2011 Wiley Periodicals, Inc.
Fluid Phase Equilibria of the Binary Systems N2 + Ethane and N2 + Pentane Between 88 K and 313 K and at Pressures up to 200 MPa
Authors: Wisotzki K. D. , Schneider G. M.
Published: July 2012

Binary mixtures of nitrogen with ethane and pentane, respectively, were investigated at pressures up to 200 MPa in an optical high‐pressure low‐temperature cell according to the synthetic method. The experimental p(T) isopleths show that both systems exhibit upper critical solution temperatures (UCST) at high pressures. The resulting critical curves start at the critical point of the pure alkane, respectively. With decreasing temperatures the critical p(T) curve of the system nitrogen + pentane runs to higher pressures exhibiting a positive curvature whereas the critical curve of the system nitrogen + ethane firstly goes through a slight pressure maximum and minimum successively and then runs steeply to increasing pressures showing a positive curvature, too. The critical curve of the system nitrogen + ethane ends at a critical end point on the three‐phase line lls ((176 ± 2) MPa, (105 ± 0.3) K) where two liquid phases become identical in the presence of solid ethane.
Molecular Photodissociation Dynamics Revealed by Multiphoton Ionisation Spectroscopy
Authors: Ashfold M. N. R. , Bayley J. M. , Dixon R. N. , Prince J. D.
Published: July 2012

This article highlights the utility of multiphoton ionisation Spectroscopy to studies of the predissociation dynamics of Rydberg states in small polyatomic molecules. Predissociation from various of the excited states of H2O, H2S and their respective deuterated analogues is demonstrated to be a sensitive function of parent rotational level and to be critically affected by H ↔ D isotopic substitution and by accidental near resonances with more heavily predissociated “doorway” states which provide more efficient coupling into the background continuum of dissociative levels.
The Photodissociation of Propynal
Authors: Brühlmann U. , Russegger P. , Stafast H. , Robert Huber J.
Published: July 2012

The lowest reaction channel on the electronic ground state potential surface of propynal HC  CCHO → HC  CH + CO as well as its calculated energy barrier have been examined by UV photolysis and by IR multiphoton decomposition.
Photoacoustic Study of Vibrational Relaxation of NO
Authors: Koshi M. , Koseki K. , Matsui H.
Published: July 2012

The first vibrational level of NO diluted in He is excited by the mechanically chopped CO laser beam and the relaxation rate constant is determined by analysing the phase shift of the acoustic signals at a temperature range of 235 – 294 K. Additional measurements in a shock tube have been done to cover the higher temperature range of 700–1900 K. The present results agree very well with those of previous work. The transition probability of vibrational energy transfer of NO to He can be expressed by

The short‐range repulsive collision model is found to represent the present experimental results of the NOHe system.
Kinetic Studies of NH2 and HCO Reactions with Unsaturated Hydrocarbons, by Flash Photolysis and Laser Resonance Absorption
Authors: Lesclaux R. , Veyret B. , Roussel P.
Published: July 2012

The flash photolysis and laser resonance absorption technique was used for the determination of the rate constants of reactions of NH2 with acetylene in the temperature range 340–510 K, NH2 with 1,3‐butadiene from 298 to 500 K and HCO with 1,3‐butadiene from 298 to 522 K. The Arrhenius expressions for the rate constants are the following (in cm3 · molecule−1 · s−1 units):

The rate expressions for k1, and k2 are compared to previous results reported in the literature. The determination of k4 represents the first data concerning the reactivity of HCO with an unsaturated hydrocarbon. A tentative evaluation of the reactivity of HCO with olefins is also given. Product analysis shows that reaction (4) proceeds essentially via an addition process rather than a hydrogen atom transfer from HCO.
Thermodynamic Properties of Molten Sodium‐Lead Alloys: EMF Measurements and Interpretation
Authors: Saboungi Marie‐Louise , Herron Steven J. , Kumar Romesh
Published: July 2012

Chemical potentials of Na as a function of composition in liquid NaPb alloys were determined in the temperature range 380–480°C by an emf technique. A solid β‐Al2O3 electrolyte and a coulometric titration were used to vary the composition. The variations of the logarithm of the activity coefficient of Na with composition exhibit three inflection points, at XNa ˜ 0.5, 0.66, and 0.80. The inflections at 0.5 and 0.80 correspond to maxima, and the inflection at 0.66 corresponds to a minimum in the Darken excess stability function. The entropy, excess stability, and other related functions, evaluated across the entire composition range, reflect the unusual properties of liquid NaPb solutions. A possible interpretation of these features might be related to the simultaneous presence of more than one valence states of Pb.
The Effect of Ionic Strength and Pressure on the Complex Formation and Hydrolysis Equilibria in the Aquated Iron(III)‐Thiocyanate System
Authors: Martinez P. , van Eldik R.
Published: July 2012

The equilibrium constants for the complex formation of Fe(H2O)3+6 with SCN− (K1) and the hydrolysis of Fe(H2O)5SCN2+ to produce Fe(H2O)4(OH)SCN+ (K4) were studied as a function of ionic strength (0.1 to 1.5 M) at 25°C and pressures up to 120 MPa. The ionic strength dependencies at ambient pressure can be expressed as log K1 = 2.86 ‐ 3.05 √ μ (1 + 2.96 √ μ)−1 + 0.04 μ and log K4 = ‐0.93 ‐ 1.02 √ μ (1 + 1.97 √ μ)−1 + 0.06 μ, from which the distance of closest approach follows to be 0.9 and 0.6 nm, respectively. The pressure dependencies of K1 and K4 result in reaction volumes ranging from 10.0 to 7.5 and 11.9 to 11.0 cm3 mol−1, respectively, for zero to 1.5 M ionic strength. These data combined with those for the hydrolysis of Fe(H2O)3+6 reported before, enable the estimation of the equilibrium constant (K3) for the formation of Fe(H2O)4(OH)SCN+ from Fe(H2O)5OH2+ and SCN−, as a function of ionic strength and pressure. This is the first study to report such data for K3, and K4, and the results are discussed in reference to data for the overall system.
Efficient Intramolecular Fluorescence Quenching in Triphenylmethane‐Dyes Involving Excited States with Charge Separation and Twisted Conformations
Authors: Vogel Martin , Rettig Wolfgang
Published: July 2012

The high fluorescence quantum yields ϕf of most Triphenylmethane(TPM)‐dyes and carbon‐bridged TPM‐dyes in highly viscous solutions (ϕf ranging from 0.3 to 0.8) decrease with increasing temperature by a factor > 100, due to viscosity dependent nonradiative deactivation. The deactivation rates krd of bridged model dyes are significantly smaller (by a factor of up to 170) as compared to krd of the unbridged crystal violet. ‐ Application of the Twisted Intramolecular Charge Transfer (TICT)‐model to neutral and ionic TPM‐dyes yields an explanation for the different behaviour of similarly structured compounds. The influence of steric and electronic factors on various TPM‐dyes is discussed within this framework. This leads to a simple rule involving donor and acceptor properties of molecular subunits, which permits the prediction of fluorescence properties (high quantum efficiency for laser dyes or ultrafast deactivation for saturable absorbers).
Studies on the n‐GaAs Photoanode in Aqueous Electrolytes. 2. Differential Capacitance Behaviour
Authors: Vanmaekelbergh D. , Gomes W. P. , Cardon F.
Published: July 2012

Impedance measurements were made on the n‐GaAs/Fe2+ photoanode as a function of electrode potential, light intensity and Fe2+ concentration. The occurrence of a peak in the parallel‐equivalent capacitance vs. potential curve indicates that surface states participate to the interfacial impedance. Considering ordinary as well as decomposition‐induced surface states and basing upon kinetic results, numerical simulations of such peaks were made for various circumstances. The calculated results are found to be in fair agreement with the experimental data.
Comparative Studies of Photoelectrochemical Behaviours of Rutile and Anatase Electrodes Prepared by OMCVD Technique
Authors: Minoura H. , Nasu M. , Takahashi Y.
Published: July 2012

Photoelectrochemical behaviours of two kinds of polymorphic form of TiO2, rutile and anatase, prepared by the organometallic chemical vapour deposition from isopropyl titanate have been comparatively studied. Photoelectrochemical characteristics of these TiO2 electrodes depend strongly upon the crystal structure and the deposition temperature. Their bandgap energies have been determined to be 3.0 eV and 3.2 eV, respectively, by the analysis of the photocurrent action spectra. The conduction band‐edge and the valence band‐edge of the anatase electrode, which have been estimated from photocurrent‐potential curves, locate at the energy level about 0.1 eV higher and lower, respectively, than those of the rutile electrode.
Entmischungsvorgänge in Polyvinylidenfluorid‐Polyethylacrylat‐Mischungen
Authors: Endres B. , Wendorff J. H.
Published: July 2012

Das amorphe Polyethylacrylat und das teilkristalline Polyvinylidenfluorid sind in der Schmelze bei nicht zu hohen Temperaturen im gesamten Konzentrationsbereich der Mischung verträglich. Eine Temperaturerhöhung führt zu einer Entmischung in der Schmelze, d.h. es existiert eine untere kritische Entmischungstemperatur. Auch eine Abkühlung aus der Schmelze bewirkt eine Entmischung, die nun allerdings durch die partielle Kristallisation des PVDF gesteuert wird. Durch geeignete Temperaturführung ist es möglich, gezielt unterschiedliche Endstrukturen für die Mischungen zu erhalten, bedingt durch Variationen in den Entmischungs‐ und Reifungsmechanismen. Diese Endstrukturen nehmen Einfluß auf die beobachteten makroskopischen Eigenschaften. ‐ Wir untersuchten die Strukturausbildung infolge einer spinodalen Entmischung und der sich anschließenden Reifung. Die Reifung ist dabei kontrolliert durch einen viskosen Fluß, der durch die im System vorliegenden Grenzflächen gesteuert wird. Eine erneute Temperaturerhöhung nach einer Reifung führt zu einer Einstellung des neuen Gleichgewichtszustandes über Entmischungsprozesse, sowohl in der Matrix als auch in der dispersen Phase. Bei einer Temperaturabsenkung führt der Weg zum neuen Zustand bei einem gereiften System dagegen nicht über eine Entmischung, sondern über eine langreichweitige Interdiffusion der Komponenten über die Phasengrenzen hinweg. ‐Durch Variation der Temperatur konnte also eine gesteuerte Strukturausbildung in der Polymerlegierung induziert werden. Hierzu muß allerdings das Phasendiagramm des verwendeten Systems bekannt sein. ‐Wir verwendeten eine Methode, die direkt die Möglichkeiten der gesteuerten Phasenseparation benutzt. Hierzu werden Legierungen des Systems bei verschiedenen Temperaturen im instabilen Bereich zur Phasenseparation gebracht. Mittels kalorimetrischer Messungen ergab sich das Massenverhältnis der beiden Phasen. Durch eine Bilanzgleichung für die beiden Polymeren in den Phasen wird es möglich, die Binodale zu bestimmen. Die Spinodale wurde mittels Röntgenkleinwinkelmessungen bestimmt. Außerdem wurde die Spinodale aus den Daten, die sich mittels der DSC‐Messungen ergaben, theoretisch berechnet.
Struktur und Eigenschaften von Modellverbindungen für segmentierte Polyurethanelastomere
Authors: Eisenbach C. D. , Nefzger H. , Baumgartner M. , Günter Cl.
Published: July 2012

Uniform model compounds for the soft and hard segments of polyurethane (PU) elastomers and the corresponding tailor‐made elastomers with monodisperse segment length distribution were investigated in regard to the structure, morphology and structure‐properties relationships of thermoplastic PU elastomers. The main conclusions relevant to the hard domains are a) that the crystalline fractions consist of a conglomerate of the eutectic of the short segments in particular and mixed crystals of segments longer than three repeat units (successive lengths only), without evidence of chain folding, b) that polymorphism exists for the hard segment crystallites and in the interface region, and c) that a rapid transurethanification reaction occurs between hydrogen bond forming urethanes at elevated temperatures.
Dielectric Properties of Some Side Chain Liquid Crystalline Polymers
Authors: Haase W. , Pranoto H. , Bormuth F. J.
Published: July 2012

An experimental setup to determine the anisotropic dielectric constants for liquid crystalline side chain polymers as function of the temperature and the frequency in the range between 100 Hz and 10 MHz is described. From the anisotropic dielectric data some more specific informations can be obtained comparing with the results obtained from unoriented samples. ‐ The anisotropic dielectric properties of two liquid crystalline side chain polymers containing the same polyacrylic main chain and slightly modified side chains are described in the glassy, nematic as well as in the isotropic state as function of temperature and frequency. For these compounds, three different relaxation processes are described. A process was found with the main component in ϵ∥ due to the relaxation of the mesogenic side chain around the main chain back bone. A broad relaxation process, near above the glass temperature, with the main component in ϵ⟂ is interpreted as due to diffusive motion of different dipoles. Another broad relaxation process occurs in the glassy state, containing parallel and perpendicular dipole components of the mesogenic ester group. In the isotropic state, the relaxation process is dominated by the parallel relaxation in the nematic state.
Mischbarkeit und Phasenverhalten von Polymerblends
Authors: Klotz S. , Gräter H. , Cantow H.‐J.
Published: July 2012

Measurements of polymer‐polymer interactions by gas‐chromatography facilitate the quantitative thermodynamic description of polymer blends in terms of Flory‐Huggins and Flory equation‐of‐state interaction parameters. These parameters were found to depend on concentration and molecular weights of the components. The interaction surface including the phase diagram of poly(styrene)‐poly(vinylmethylether) is obtained. Poly(styrene)‐poly(phenyleneoxide) were investigated by gas‐chromatography too. Lower critical solution behaviour is also observed for this system. The results are discussed and compared with theoretical calculations according Flory's equation‐of‐state theory. There is only qualitative correspondence between theoretical calculations and experiments. Additionally polymer‐polymer interactions in dilute solution were investigated. The so‐called light scattering under “optical θ‐condition” make it possible to state whether a polymer pair is compatible or not.
Interpretation of Counterion Spin Relaxation in Polyelectrolyte Solutions. II. Effects of Finite Polyion Length
Authors: Halle Bertil , Bratko Dušan , Piculell Lennart
Published: July 2012

The applicability of the recently proposed CDM theory of counterion spin relaxation in polyelectrolyte solutions [Halle, Wennerström & Piculell, J. Phys. Chem. 88, 2482 (1984)] is extended to low degrees of polymerization. Polyion end effects on the counterion distribution and dynamics are described in the spheroidal‐cell model of Bratko & Dolar [J. Chem. Phys. 80, 5782 (1984)]. The extended theory is applied to 23Na spin relaxation data from saltfree solutions of sodium poly (styrenesulfonate) and it is found that the available data can be explained by a model in which polyions of length 20–100nm reorient as fully extended, rigid bodies.
Solid State Chemical Model for the Solubility Behaviour of Homogeneous Solid Co‐Mn‐Carbonate Mixtures
Authors: Gamsjäger H.
Published: July 2012

A continuous series of homogeneous solid mixtures Co(1‐x)MnxCO3 was synthesized by an autoclave method. In agreement with the formalism of ideal and regular solid ionic mixtures, the excess molar volume of mixing was negligible and the cation‐anion distances obeyed Vegard's rule in the whole compositional range. Solubility measurements using the pH variation method revealed that Co(1‐x)MnxCO3 phases dissolved congruently in aqueous acidic media at 50°C. Thermodynamic analysis of the solubility data showed that a closer fit was obtained assuming regular rather than ideal mixing.
On the Order‐Disorder Phase Transition of Anilinium Halides. Crystal Structure of the High and Low Temperature Phase of Anilinium Iodide, C6H5NHI⊖ (C6D5NHI−). X‐Ray and Neutron Diffraction Studies
Authors: Fecher Gerhard , Weiss Alarich
Published: July 2012

The crystal structure of the high temperature phase I of anilinium iodide, C6H5NHI⊖, was determined by X‐ray and neutron diffraction at T = 294 K: D‐Pnaa, Z = 4, a = 1738.2(10) pm, b = 636.3(5) pm, c = 703.9(5) pm, ϱcalc = 1.886 Mgm−3. At Tc = 241 K, a ferroelastic phase transition occurs. The crystal structure of the low temperature phase II was studied on C6D5NHI⊖ by neutron diffraction at T = 140K: C52h‐P21/a, Z = 4, a = 1753.8(10) pm, b = 614.2(5) pm, c = 706.5(5) pm, β = 90.79(1)°, ϱcalc = 1.973 Mgm−3. Phase I is disordered with respect to four different positions of the −NH group, whereas phase II is ordered. The present results are compared with the crystal structures and the phase transition of anilinium bromide, C6H5NHBr⊖. The mechanism of the phase transition is discussed.
Vapour Pressure of Molten Acidic Potassium Chloride‐Aluminium Chloride‐Aluminium Chloride Monoammine Mixtures
Authors: Nakamura Kunihiko , Østvold Terje , Øye Harald A.
Published: July 2012

The acidic KCl‐AlCl3NH3AlCl3 melt has been studied by vapour pressure measurements, vapour condensation measurements and mass spectrometry. ‐ Vapour pressures were measured by the boiling point method. The total vapour pressure above AlCl3NH3(1) is given by the expression: ln(P/atm) = ‐8660 (T/K)−1 + 12.69. The partial pressure may be expressed by ln (P3/atm) ∼ ‐8589 (T/K)−1 + 12.53. ‐ Together with mass spectrometric experiments the composition of the equilibrium vapour was determined by direct condensation of the boiled‐off vapour above the KCl‐AlCl3NH3‐AlCl3 melts. The existence of the species Al2Cl6, AlCl3, AlCl3NH3 and Al2Cl6NH3 were confirmed. ‐ Thermodynamic properties of the ternary melts were described through thermodynamic model calculations based on the following equilibria.

The activities of Al2Cl6 calculated at a given temperature were in good agreement with experimental data (SD in the fit was ± 2.1%). The calculated total pressures agreed fairly well with experimental pressures (SD = ± 8.5%) taking also into account data which was not used for modelling.
Proton Exchange of Water in Layered Intercalation Compounds
Authors: Wein E. , Müller‐Warmuth W. , Schoöllhorn R.
Published: July 2012

Proton exchange of water has been studied in hydrated layered dichalcogenides of the type Ax(H2O)y[NbS2] by NMR techniques. Intermolecular proton exchange has been detected in all guest phases studied, where A = Li, Na, K, Rb, Cs. Exchange rates have been determined at various temperatures, and their activation energies have proved to increase more or less linearly with the enthalpy of hydration of the respective cation. The results are compared with those in solutions and possible mechanisms of proton exchange in layered intercalates are discussed.
Kinetics of the (7 × 7) ↔ (1 × 1) Transition on Si(111)
Authors: Telieps W. , Bauer E.
Published: July 2012

The (7 × 7) ↔ (1 × 1) phase transition was investigated in situ by low energy electron reflection microscopy (LEERM). Heterogeneous nucleation of the (7 × 7) domains at monoatomic steps is observed as well as homogeneous nucleation in the atomically flat terraces. The density of nuclei and the domain growth velocity increase with the supercooling ΔT of the surface. The domains start to grow at low ΔT in triangular equilibrium shape; interaction of neighbouring domains leads to a dendritic overall shape. The observations strongly support the view that the transition is of first order.
Order‐Disorder Phenomena in the System CO/Ru(001)
Authors: Pfnür H. , Heier H. J.
Published: July 2012

Metal‐mediated interactions, dominant in a moderately strong chemisorbed system like CO/Ru(001), cause changes of lateral interactions not only as a function of distance between adsorbed particles but also as a function of coverage and introduce ordering mechanisms different from those observed for noble gas adsorbates. Results of a detailed LEED study are presented, carried out by photographical and by spot profile analysis. Coverage induced structural changes up to saturation coverage as well as of the order disorder transitions as a function of temperature at fixed coverage are discussed and structural models and a phase diagram are given.
A Direct Study of the Reaction CH2(X3B1) ± C2H4 in the Temperature Range 296 K ≤ T ≤ 728 K
Authors: Böhland T. , Temps F. , Wagner H. Gg.
Published: July 2012

The reaction between CH2‐radicals in the triplet electronic ground state X˜3B1 (3CH2) and C2H4

was studied in the gas phase at temperatures between 296 K ≤ T ≤ 728 K in an isothermal discharge flow system. CH2‐radicals were generated either in the reaction O + CH2CO or by exciplex laser photolysis of CH2CO. Their concentration was monitored with a far infrared Laser Magnetic Resonance spectrometer. The experimental rate constant obtained from the pseudo first order decay of 3CH2 in the presence of a large excess of C2H4 was found to be

Correcting for the small contribution to the depletion of 3CH2 due to collisional excitation to the singlet first excited state ã1A1(1CH2) followed by consecutive reactions of 1CH2, the rate constant for the direct reaction of 3CH2 with C2H4 was obtained to be

A reaction mechanism describing both the present data as well as the results of earlier related‐studies in the CH2 + C2H4 system is proposed. The mechanism and product yields are discussed in terms of unimolecular rate theory.
Real‐Time Neutron Powder Diffraction: A Technique for the Study of Solid State Reactions
Authors: Pannetier Jean
Published: July 2012

The use of large position sensitive detectors (PSD) on high flux powder diffractometers allows a powder diffraction pattern to be recorded on a time scale of a few minutes or less so that transient phenomena such as heterogeneous chemical reactions can now be studied easily. Such measurements provide direct information on the progress of a reaction (kinetic law) but may also shed light on the transformations of structure and/or morphology which occur in the reactants during the course of a reaction. The applicability of this real‐time diffraction method for investigating isothermal and temperature stimulated structural changes is illustrated by selected experiments in the field of solid state inorganic chemistry.
Ionic Transport in Heterogeneously and Homogeneously Doped Thallium (I)‐Chloride
Authors: Maier J. , Reichert B.
Published: July 2012

The effect of alumina admixtures on the ionic conductivity of TlCl is studied. In agreement with the model of “Heterogeneous Doping” a change of the intrinsic anionic conduction (Cl ‐vacancies) into a Tl+‐conduction (Tl+‐vacancies) is induced at lower temperatures (≦ 300 K). The experimental conductivity data as a function of temperature, concentration and grain‐size can be quantitatively described with an interface defect concentration considerably lower than for AgCl and AgBr. Likewise, for pure polycrystalline TlCl space charge regions enriched in cation vacancies around grain boundaries are assumed to provide an increase of the conductivity. Similarities and differences between heterogeneous and the classical homogeneous doping are clearly reflected by experiments using PbCl2 as a dopant for both TlCl and TlCl: Al2O3
The Electrochemical Behaviour of Manganese (II)‐Hydroxide/Magnesium Hydroxide and Manganese (II)‐Hydroxide/Calcium Hydroxide
Authors: Bauer Jügen , Buss Dieter H. , Glemser Oskar
Published: July 2012

The double hydroxides Mn(OH)2Mg(OH)2 and Mn(OH)2Ca(OH)2, precipitated by computer control, were investigated as positive electrodes for secondary cells in aqueous potassium hydroxide solutions with regard to charge capacity and cycling behaviour. Mn(OH)2Mg(OH)2‐hydroxides form solid solutions, whereas Mn(OH)2Ca(OH)2‐hydroxides occur as mixtures. In the system Mn(OH)2Mg(OH)2 only samples between 30 and 60 mol% Mg are electrochemically active and discharge capacities of 164–213 mAh/g are found in the first discharge process, with an oxidation state corresponding to MnO1,8. Afterwards the capacity falls to 24 mAh/g. Surprising in the system Mn(OH)2Ca(OH)2 is the rapid air oxidation of the samples with 30–50 mol% Ca to oxidation degrees of MnO1.8. These samples are further oxidized electrochemically to ∼MnO2.0, and are electrochemically active with discharging capacities between 96 and 133 mAh/g. They have a better cycling behaviour than the Mn/Mg‐species. The striking behaviour of the two double hydroxides is a consequence of their structural relationships.
High Temperature Reactions of CH3 1. The Reaction CH3 + H2 → CH4 + H
Authors: Möller W. , Mozzhukhin E. , Wagner H. Gg.
Published: July 2012

The rate coefficient of the reaction CH3 + H2 → CH4 + H was determined at high temperatures behind incident shock waves by time‐resolved measurements of the absorption of the methyl radical at 216.5 nm. The resulting Arrhenius expression k3 = 1013.3±0.1 exp(−(7200 ± 400) K/T) cm3 mol−1 s−1 is in good agreement with earlier indirect measurements. Several methyl radical sources are compared.
On the Decay of the Dichloride Anion Cl−2 in Aqueous Solution
Authors: Wagner I. , Karthäuser J. , Strehlow H.
Published: July 2012

The decay kinetics of Cl−2, produced by photolysis of chloride ions, has been studied using a flash photolysis technique with conductometric detection. Flash photolysis of Cl− ions in acid solutions eventually yields H2O2, Cl2, HClO and H2. A mechanism is proposed (Fig. 6) consistent with the experimental observations.
The Modelling of Gasphase Aromatisation in the Pyrolysis of Hydrocarbons (Part II)
Authors: Stabel U. , Ederer H. J. , Ebert K. H.
Published: July 2012

The kinetics of the thermal decomposition of n‐hexane and some hydrocarbon mixtures was studied experimentally in respect to the homogeneous formation of aromatics. Some 60 reaction products were identified, among them a number of precursor substances. An attempt has been made to extend our previous reaction model for the mathematical simulation of n‐hexane gas phase pyrolysis by addition of detailed pathways for the formation of benzene and toluene.
Oscillations and Coupling Phenomena Between Different Areas of the Catalyst During the Heterogeneous Catalytic Oxidation of Ethanol
Authors: Jaeger N. I. , Ottensmeyer R. , Plath P. J.
Published: July 2012

The heterogeneously catalyzed oxidation of ethanol was found to be a new chemical system, which exhibits oscillatory behavior. Experiments were carried out using a continuous flow calorimeter and an amorphous alumina‐supported Palladium catalyst.—Temperature as well as product oscillations are presented. Detailed measurements of the temperature of the catalyst reveal coupling and decoupling phenomena between different synchronized areas of the catalyst bed. On the basis of the phase relation between product oscillations possible mechanisms are discussed.
Static and MAS 35CI NMR and Molecular Motions of ClO Ions in the Various Phases of Multimethylammonium Perchlorates
Authors: Jurga S. , Harbison G. S. , Blümich B. , Spiess H. W. , Fujara F. , Olinger A.
Published: July 2012

Static and MAS*) 35CI NMR data of CIO−4 ions in the low‐, intermediate‐ and high‐temperature phases of trimethylammonium, dimethylammonium and monomethylammonium perchlorates are reported. The observed solid‐solid phase transitions are interrelated with the motional state of the perchlorate ions. In the low‐temperature phase III of trimethylammonium perchlorate there is an anisotropic motion of the ClO−4 ions with a constant quadrupole frequency of 185 kHz and an increasing value of the asymmetry parameter when approaching phase transition III‐II. The activation energy for this motion is found to be 44.3 kj/mol. At the transition III‐II the ClO−4 ions gain orientational degrees of freedom manifested by the change of the quadrupole frequency to 159 kHz. In phase II the perchlorate ions undergo an axial motion overcoming the energy barrier of 40.7 kj/mol. In the low‐temperature phase III of dimethylammonium perchlorate there are rigid ClO−4 ions. At the phase transition III‐II the ClO−4 ions gain considerable motional freedom indicated by lowering the quadrupole frequency to 119 kHz, due to an anisotropic motion. In the high‐temperature phase I the anions undergo isotropic motion with the activation energy of 11.9 kj/mol. The low‐temperature phase III of monomethylammonium perchlorate is characterized by rigid ClO−4 ions. At the transition III‐II the ClO−4 ions gain a considerable motional freedom and undergo an axial motion in phase II. In phase I motion of the anions is isotropic. The motional behaviour of the anions along with NMR data for the cations suggests that the low‐temperature ordering of the ions in phase HI is due to hydrogen‐bonds NH … OCl, the partial breaking of which, accompanied by the phase transition III‐II, leads to an axial motion of the ions in phase II. A complete breaking of all hydrogen‐bonds in phase I allows the ions to reorient isotropically. The quadrupole coupling constant of rigid ClO−4 ions amounts to about 1 MHz.
Molecular Structure Determination Inferred from Highly Resolved 4A2g ↔ 2Eg, 2T1g Spectra and Ligand Field Calculations of Trigonally Distorted Hexaamminechromate(III)
Authors: Urushiyama Akio , Schönherr Thomas , Schmidtke Hans‐Herbert
Published: July 2012

Highly resolved vibronic spectra were measured at helium temperatures due to spin‐forbidden 4A2g ↔ 2Eg, 2T1g d—d transitions of hexaamminechromate(III) salts. Almost complete assignments of the detailed vibrational structure are presented including the band positions of all five spin‐orbit electronic origins of S6. The electronic level schemes can be rationalized by conventional ligand field calculations because for NH3‐ligands no π‐bonding is involved. From the electronic level splittings polar angles of trigonal distortions from CrN6 octahedra were determined to be Δα = 0.19° for the CdC‐salt, and 0.23° for the analogous copper compound. The phosphorescence spectra exhibit progressions mainly in the Jahn‐Teller active mode ν2(eg); from relative band intensities, bond length changes of the emitting excited state by a few mÅ are calculated.
Fe/Mn Oxide Catalysts for Fischer‐Tropsch‐Synthesis Part VII: Adsorption of Carbon Monoxide and Nitrogen at Low Temperatures
Authors: Hess D. , Papp H. , Baerns M.
Published: July 2012

Iron/manganese oxides often used as catalysts for the Fischer‐Tropsch (FT) hydrogenation of CO have been characterized by their adsorption properties. N2 physisorption was carried out at 77 K and CO chemisorption at 194 K in a vacuum microbalance. Precipitated solids with compositions ranging from pure iron oxide to pure manganese oxide were studied after calcination and reduction. The results indicate a correlation between the fraction of metallic iron in the surface, the irreversible chemisorption of CO at 194 K and the initial activity for FT synthesis.
Thermodynamic properties of molten Na‐Te solutions
Authors: Petric Anthony , Pelton Arthur D. , Saboungi Marie‐Louise
Published: July 2012

Thermodynamic properties of liquid Na‐Te solutions were measured over the range 0–52 at.% Na at temperatures between 573 and 873 K by means of alloy concentration cells. Beta alumina was used as the solid electrolyte. The following properties were derived from the emf data: ΔG, ΔH, ΔS, the excess heat capacity CE p and the excess stability, ES. The Gibbs energy, enthalpy and entropy showed marked negative deviations. The plot of excess stability versus composition exhibits a rather flat shoulder between 10 and 20 at.% Na and a broad maximum or shoulder near 50% Na indicating maximum short‐range ordering near these compositions. Liquidus and invariant points on the phase diagram as well as the Gibbs energies of formation of the solid compounds NaTe3, NaTe and Na2Te have also been determined.
Mixtures with “w‐Shape” CEp curves. A light scattering study
Authors: Rubio Ramón G. , Cáceres Mercedes , Masegosa Rosa M. , Andreolli‐Ball Lina , Costas Miguel , Patterson Donald
Published: July 2012

The Rayleigh ratio has been obtained for the following mixtures of non‐electrolytes that show “w‐shape” CEp vs. x curves: Nitrobenzene + n‐Heptane, 1,4‐Dichlorobutane + n‐Heptane and Acetone + n‐Dodecane. From them, the concentration‐concentration correlation function Scc(0) has been calculated, as well as the excess Gibbs energy. It has been found that a clear tendency to homocoordination is present in all the mixtures studied. There is a rough correspondence between the concentration at which the maximum of the Scc(0) curves occur and those at which the negative curvature regions exist in the CEp curves. Also the larger the value of max. Scc(0) the more intense the “w‐shape” effect. Despite size differences between the components and specific interactions which complicate the connection between Scc(0) and CEp, an analysis in terms of simple mean field models supports the view that the systems which show “w‐shape” CEp curves still feel the effects of the more or less distant UCST. Hence Scc(0) is proposed as an indicator of the “w‐shape” CEp.
Laser‐tissue interactions
Authors: Srinivasan R.
Published: July 2012

The interactions of laser radiation with animal tissue have become a vast field of study. The detailed chemical behavior of the photons with the tissue, while scientifically a fascinating topic for investigation, is difficult to study experimentally. We have used synthetic polymers and small molecules in the condensed phase as models for the study of non‐linear photochemistry of all organic systems. While such extrapolations should always be used with caution, they have been helpful in suggesting new strategies for tissue ablation which may be adaptable to experiments in vivo. —In etching and ablation by pulsed ultraviolet lasers, the power density at the surface of the polymer or tissue is critical in determining the threshold for ablation and the etch depth per pulse at photon fluxes greater than the threshold. This has been explained by a mechanism in which a single chromophore is excited to high electronic levels by the successive absorption of two or more photons. Recent experiments have been directed towards the use of pairs of laser pulses with a preset time interval separating them in order to couple the multi‐photon excitation process to the excited states of the chromophores in the solid in an optimum fashion. The initial results suggest that a certain amount of “tuning” of the laser pulse to suit the ablation kinetics of the substrate is not only possible but may be useful in practical applications of UV laser: tissue interactions.
Laser in medicine
Authors: Senz R. , Müller G.
Published: July 2012

Between 1965 and 1980 basic research into the medical use of lasers led to the discovery of new applications. Today we differentiate between three classes of principle interactions. Firstly there are the photochemical effects whereby laser energy is used to trigger off photochemical reactions on biomolecules by absorption of either natural or artificial dyes, or chromophoric groups. This is one of the basic principles of nature, e.g. photosynthesis and the vision process. —A further effect is based on the fact that the absorption of light at a suitable wavelength and intensity is converted into heat which accordingly leads to a heating effect of the irradiated tissue. It is a thermal effect whereby the result is dependent on the degree of absorption and the amount of radiation absorbed. In this way photocoagulation and tissue cutting is possible. —The third effect can be summarized under the term “non‐linear effects”, as they cannot be explained by the linear absorption of photons, i.e. radiation, and therefore are classified according to the effects that they produce. It is possible by these non‐linear effects to remove material fragments from the surface by light without heating the surrounding area. —Between the above mentioned thermal effects, there are the so‐called “photoacoustic effects”. Thermal absorption and time behaviour of the light radiation leads to changes in the acoustic and thermal density which results in the destruction of material. —The laser may contribute in future to solving the following problems: Recanalisation of arterial blood vessels; Destruction or fragmentation of stones in the kidneys, bladder, efferent urinary tracts as well as in the bilary tract; photochemical reactions by choosing the applicable laser wavelength, e.g. polymerisation of biocompatible plastics “in situ”.
Time resolved fluorescence quenching‐experiments on tryptophan and tyrosine containing proteins
Authors: Kühn Klaus P. , Ludwig Horst , Brecht Andreas , Schwarzwald Ralf , Greulich Karl Otto
Published: July 2012

The protein rop, some of its mutants and the human complement component C9 were studied using steady state fluorescence spectroscopy and lifetime resolved fluorescence quenching experiments. —The rop molecule has a hairpin like structure and a tail consisting of 7 amino acids, which is not visible in the electron density map of X‐ray crystallography. The lifetime resolved quenching experiments show that at low salt concentrations the tail is attached to the main body of the molecule, while it is removed at high salt concentrations. This difference can be explained by shielding of electrostatic interactions at high salt. —A comparision of C9 and its polymer with respect to their fluorescence quantum yields and fluorescence lifetimes shows that in the poly C9 three of the four tryptophanes are quenched by intramolecular processes. Furthermore the experiments reveal a discrepancy between exposure of tryptophan determined by the emission spectrum or determined by use of the surface quenchers I− and Cs+.
An Experimental Study of the Reactions CH3CHO + Cl, C2H4O + Cl, and C2H4O + F in the Gas‐Phase
Authors: Bartels M. , Hoyermann K. , Lange U.
Published: July 2012

The reactions of chlorine and fluorine atoms with the structural isomers CH3CHO and C2H4O have been studied at low pressures and room temperature by the discharge flow technique with mass spectrometric detection. Using the reference reactions magnified image the relative rate constant for the reactions magnified image were determined: k1/k0 = 1.04 ± 0.09, k2/k0 = 0.49 ± 0.04, k3/k00 = 0.47 ± 0.05. — Reaction (1) proceeds mainly via hydrogen abstraction from the aldehyde group (> 93%) forming CH3CO. In the reactions of ethylene oxide (2), (3) the abstraction route is observed, contributions from addition channels in reaction (2) are discussed.
Gas‐Phase Dimerization of Sodium Halides and Formation of Mixed Sodium/Phenyl Iodides
Authors: Alkemade U. , Homann K. H.
Published: July 2012

The formation of dimers and oligomers of the monomeric sodium halides NaCl, NaBr and NaI were studied in a flow reactor at a pressure of 300 Pa and temperatures of 623 and 645 K. The reactions propynyl chloride/bromide + Na vapour were used to generate the gaseous NaCl and NaBr while the sodium iodide monomer was formed via the reaction Na + CH3I. The rate constants for the dimerizations of NaCl, NaBr and NaI were found to be 8.0 · 1013, 5.0 · 1013 and 5.0 · 1012 cm3 mol‐1 s‐1, respectively. Under the experimental conditions the dimerizations were near their high‐pressure limits. NaCl oligomers up to [NaCl]5 were detected while the detection of NaBr oligomers was limited by the accessible mass range to [NaBr]3. — In the system Na + Phenyliodide (PhI) mixed Na/Phenyliodides were formed but hardly any NaI. Disodium‐phenyliodide was a main product. Higher compounds such as Na3Ph2J and Na3PhI2 were also detected in lower concentrations. In addition, diphenyl was a product of a homogeneous reaction while benzene was formed both by a heterogeneous and a homogeneous reaction. The reaction mechanism is discussed on the basis of an intermediate complex Na + PhI → NaPhI.
Electrical and Dielectric Behaviour at the Critical Point of Binary Liquids: Acetonitrile + Cyclohexane
Authors: Jayalakshmi V. , Guha S. , Gopal E. S. R.
Published: July 2012

The electrical capacitance and resistance of the binary liquid mixture cyclohexane + acetonitrile are measured in the one phase and two phase regions at spot frequencies between 5 kHz and 100 kHz. This sample has a very low gravity affected (∼0.6 mK) region. In one phase region the capacitance data show a sharp, ∼0.7% increase above background within 0.5 degrees of Tc whereas the resistance has a smooth increase of ∼1.5% above background in a (T−Tc) range of 4 degrees. Two phase values of capacitance and resistance from the coexisting phases are used to determine the critical parameters Tc (critical temperature), Rc (resistance at Tc) and Cc (capacitance at Tc). A precise knowledge of these parameters reduces the uncertainty on the critical exponent 0 for C and R. The one phase capacitance data fit to an (1 ‐ α) exponent in a limited temperature range of 0.2 degrees. Resistance data strongly support an (1 ‐ α) exponent over the entire 5 degree range.
Solvent induced intramolecular electron exchange kinetics in 1,3‐isodisubstituted aromatic radical anions I. ESR‐measurements at 280 K
Authors: Grampp G. , Shohoji M. C. B. L. , Herold B. J.
Published: July 2012

The rate constants of the intramolecular solvent induced electron transfer in 1,3‐dinitrobenzene and benzene‐1,3‐dicarbaldehyde radical anions were measured in different solvents by means of ESR‐spectroscopy using the alternating linewidth effect. At 280 K, for benzene‐1,3‐dicarbaldehyde the rate constants are 0.89–1.52·109 s−1 in several alcohols, whereas for the 1,3‐dinitrobenzene radical they are 1.16–2.19–106 s−1 in alcohols and 2.8–4.2·109 s−1 in aprotic solvents. The reactions were found to be adiabatic and uniform in the sense of classical transition state theory. From the solvent dependence of the rate constants, the transferred charge was determined applying Marcus theory as being z = 0.31 for the benzene‐1,3‐dicarbaldehyde, z = 0.84 for the 1,3‐dinitrobenzene radical anion in alcohols and z = 0.51 in aprotic solvents. The ellipsoidal cavity model was employed for evaluating the outer sphere reorganization energy λ0.