bluuebunny/crossref_metadata_2025 huggingface dataset:
The Photoelectrochemistry of Gallium Selenide
Authors: Gerischer H. , Gobrecht J. , Turner J.
Published: July 2012

GaSe‐crystals have a layer structure and a band gap of 2 eV. The electrode behaviour of p‐type specimens has been investigated by measuring current‐voltage curves in the dark and at illumination, by determining capacity‐voltage correlations and by studying the spectral dependence of the photocurrents. It has been found that the surface orientation besides surface perfection has an extraordinary influence on the results reflecting the anisotropy of the electronic properties of such a material. The differences in photocurrent yield for light incident either normal or parallel to the layer planes are in good agreement with the optical constants for these directions. The differences in reactivity at cathodic bias are discussed on the basis of the calculated electron distributions in the valence bands of this material combined with the assumption that surface states with acceptor character exist in the energy range below the conduction band edge.
Reactions of N+4 Ions with a Variety of Neutral Molecules
Authors: Mccrumb J. L. , Rakshit A. B. , Warneck P.
Published: July 2012

Rate coefficients and product distributions for reactions of N+4 with H2, Kr, CO, CO2, N2O, CH4, SO2, CF2Cl2, O2, C2H2, NH3, CS2, and NO were determined, using a drift‐chamber mass‐spectrometer. The rate coefficients are compared with data from other authors where possible and are discussed with respect to reaction efficiencies and displacement products.
Study of a Fluid/Solid Interface over a Wide Density Range Including the Critical Region.: II. Spreading Pressure and Enthalpy of Adsorption of Ethylene/Graphite
Authors: Findenegg G. H. , Specovius J.
Published: July 2012

The thermodynamic properties of a solid/fluid interface are studied over a wide range of densities of the fluid around its critical temperature. Starting from experimental surface excess isotherms of the system ethylene/graphite the spreading pressure and the integral enthalpy of adsorption is derived. In the one‐phase region of the fluid the spreading pressure increases with increasing density and with decreasing temperature; along the critical isochore it increases from the one‐phase region into the two‐phase region, with a discontinuity in slope at the critical point. The integral enthalpy of adsorption per unit area contains two terms: an adsorption term which is large at low densities and near the critical point, and a term related to the bulk density of the fluid which dominates at high densities when the surface excess concentration is small.
Ostwald Ripening of Precipitates. I. The Path Integral Solution
Authors: Chan Sai‐Kit
Published: July 2012

A path integral solution to the differential equation of Ostwald ripening is presented. It is built up from the short‐time solution obtained by treating the diffusion constant or fluctuation as a small parameter. The physical picture that emerges from the result is that the time‐evolution of the size distribution involves essentially two basic steps. The first consists of horizontal shifts by various portions of the distribution which are towards the larger sizes if the size exceeds the critical radius and towards the smaller sizes if otherwise. The second consists of vertical scaling of the various parts of the distribution which is upwards if the gradient of the growth rate as a function of size is negative and is downwards if otherwise.
The Static Dielectric Constant of Water at High Pressures and Temperatures to 500 MPa and 550°C
Authors: Heger K. , Uematsu M. , Franck E. U.
Published: July 2012

Measurements of the static dielectric constant (permittivity) of water have been made between 100 and 550°C to a maximum pressure of 500 MPa. A capacitor within a high‐pressure vessel and a transformer ratio bridge at a frequency of 100 kHz were used. The capacitor was made of two coaxial half‐cylinders, which could be rotated against each other to eliminate lead capacities. At 200°C and 100 and 500 MPa resp. values of 38.0 and 45.8 and at 500°C and at the same pressures values of 9.3 and 18.8 were found for the dielectric constant. Using the experimental data Kirkwood correlation factors were calculated and presented in dependence of temperature and density.
Die konsistente ligandenfeldtheoretische Interpretation des spektroskopischen und magnetischen Verhaltens des 5‐Elektronensystems in oktaedrischen Halogenokomplexen
Authors: Eichberger K. , Lux F.
Published: July 2012

Auf der Grundlage eines erweiterten ligandenfeldtheoretischen Ansatzes, der auch Kovalenzeffekte erfaßt, wurden f‐f‐Spektren und Magnetismus oktaedrischer [MX6]n‐‐Komplexe (M = Ln, An; X = F, Cl, Br) interpretiert. Zur Bestimmung der in diesem Ansatz auftretenden Parameter (ζ δ, θ, k, k1) wurde ein neues Auswerteverfahren entwickelt. Dadurch ließen sich erstmals sowohl die spektroskopischen wie die magnetischen Eigenschaften der genannten Verbindungen widerspruchsfrei beschreiben. Die ermittelten ζ‐Werte stimmen mit den Spin‐Bahn‐Kopplungskonstanten der entsprechenden freien Ionen überein. Es wird gezeigt, daß man durch Verwendung der Orbitalreduktionsfaktoren k und k1 eine Beeinflussung der Ligandenfeldparameter δ und θ durch Kovalenzeffekte vermeidet. Aus dem Trend der k‐ und k1‐Werte beim Übergang von Fluoro‐ zu Chloro‐ und Bromokomplexen folgt, daß eine Änderung der Kovalenz nur auf die T4‐Orbitale einwirkt.
PVT‐Daten von Acetonitril, Undecan und Dodecan bis 3 kbar und −50°C. Druckabhängigkeit der Umwandlungsvolumina, ‐enthalpien und ‐entropien
Authors: Landau R. , Würflinger A.
Published: July 2012

Es wird eine Hochdruckapppratur zur Bestimmung vonPVT‐Daten bis zu 3000 bar von flüssigen und festen Phasen beschrieben. Der Temperaturbereich beträgt −200°C bis 40°C, eine genaue Eichung erfolgte jedoch erst bis zu −50°C. Es werden zwei Meßverfahren beschrieben (mit und ohne Übertragungsflüssigkeit). Die bei Phasenumwandlungen auftretenden Volumensprünge können mit beiden Verfahren gemessen werden,PVT‐Daten jedoch nur bei dem Meßverfahren ohne Übertragungsflüssigkeit. Aus den gemessenen Volumensprüngen werden mit Hilfe der Gleichung von Clausius‐Clapeyron die zugehörigen Enthalpie‐ bzw. Entropieänderungen berechnet und diskutiert. Acetonitril und Undecan zeigen Festkörperumwandlungen, die näherungsweise Isochoren parallel laufen. Dagegen nimmt die Volumenänderung beim Schmelzen für alle 3 Substanzen mit steigendem Druck stark ab.
Praktische Möglichkeiten der Energiekonservierung in biologischen Systemen
Authors: Fedtke Carl
Published: August 2012

Von den verschiedenen Möglichkeiten der Energiegewinnung aus Biomasse werden drei Systeme genauer beschrieben:

1. Methangewinnung aus organischen Abfällen und aus „Energiepflanzen”︁, 2. Äthanolgewinnung aus „Energiepflanzen”︁ und 3. Wasserstoffproduktion durch Biophonolyse des Wassers. Für alle drei Systeme werden die Realisierungsmöglichkeiten innerhalb der nächsten Jahrzehnte und die mögliche mengenmäßige Bedeutung diskutiert. Dem Aspekt der Energie‐Rentabilität, ausgedrückt als Verhältnis zwischen Energieertrag im Endprodukt und Energieeinsatz bei der Erzeugung, wird besondere Bedeutung beigemessen.
Methanreformierung und Methanisierung — Ein neues Verfahren des Transports von Hochtemperaturwärme
Authors: Teggers H.
Published: August 2012

Es wird die Möglichkeit des Wärmetransportes mit Hilfe eines thermochemischen Kreisprozesses — bestehend aus der endothermen Methanreformierung mit Wasserdampf zu einem Synthesegas und der exothermen Rückreaktion, der Methanisierung — in Verbindung mit dem Hochtemperatur‐Kernreaktor (HTR) vorgestellt. Es handelt sich dabei um ein Energietransportverfahren, das den Anforderungen des Gesamtenergiemarktes, vor allem in Ballungsgebieten, gerecht wird. Die Entwicklung des Verfahrens ist eng mit der Entwicklung der nuklearen Prozeßwärme verknüpft. Aufgrund der Langfristigkeit der Durchführung solcher Projekte bis hin zur großtechnischen Anlage sind Aussagen zur Wirtschaftlichkeit noch mit gewissen Unsicherheiten behaftet. Die Konkurrenzfähigkeit gegenüber Systemen zur Erzeugung von Heiz‐ und Prozeßwärme auf der Basis fossiler Energieträger ist wesentlich durch die zukünftige Preisentwicklung der fossilen Rohstoffe bestimmt.
Contribution of Membrane Potentials to Energy Conversion in Photosynthetic Membranes
Authors: Huber H.‐L. , Rumberg B. , Siggel U.
Published: August 2012

The conversion of the energy of light into the chemical energy of ATP occurs at the photosynthetic membrane with the transmembrane electrochemical gradient of protons as intermediate. The electric portion, i.e. the light‐induced change of the electric potential difference (photopotential), quickly attains a maximum of 200 mV after the onset of illumination and decreases toward the steady state for the benefit of the H+‐concentration gradient. The resulting stationary photopotential is determined by two different methods, on the one hand directly through the electrochromic absorption change of membrane pigments, on the other hand by calculating the change of the surface potential at the inner side of the membrane from the surface charge densities. The charge density in the dark state is derived from the kinetics of an electron transfer reaction in the membrane (reduction of oxidized chlorophyll‐aI) sensitive to the pH of the inner surface. Its dependence on pH is characterized by an isoelectric point of 4.8. The light‐induced change of the charges is determined from the amount of protons additionally bound to the inner membrane surface. For the calculation of surface potentials from the charge densities the conventional Gouy‐Chapman theory is modified by assuming a transverse spreading of surface charges over a layer of 20 A thickness. — The results of both the methods are similar. The stationary transmembrane photopotential is dependent on the concentration of electrolyte and exhibits a maximal value of 60–70 mV at 6 mM KCl. Under physiological conditions the contribution of the photopotential is below 20 mV and can be neglected compared to the light‐induced difference in proton concentration with respect to energetic and kinetic considerations.
Magnetische Eigenschaften von FeTi und dessen Hydriden
Authors: Stucki F. , Schlapbach L. , Seiler A.
Published: August 2012

Magnetisierungsmessungen am Wasserstoffspeicher FeTi weisen auf eine reversible Änderung der magnetischen Eigenschaften des Volumens und eine irreversible Änderung der magnetischen Eigenschaften der Oberfläche als Folge des Hydrierens hin. Verantwortlich für die irreversible Änderung sind superparamagnetische Fe‐Teilchen, die hauptsächlich in einer Oberflächenschicht ausgeschieden werden. Die Suszeptibilität des Volumens der FeTi‐Hydride ist kleiner als die des Ausgangsmaterials.
Kinetics of the Steam Reforming of Methane on Iron as a Catalyst
Authors: Münster P. , Grabke H. J.
Published: August 2012

The kinetics of the reaction CH4 + H2O → CO + 3H2 have been investigated in the temperature range of 700°C to 900°C on iron as a catalyst. In the reaction sequence

the first step, the decomposition of methane, is rate controlling. The reaction is retarded with increasing H2O/H2‐ratio, which indicates site blocking by adsorbed oxygen. The rate equation can be written

As can be derived from the reaction kinetics, in the flowing gas mixture the steady state carbon activity will be very low on and in the iron catalyst, this was confirmed by electrical conductivity measurements.
The Spherical Crystal Potential and Physical Properties of Ions in Crystals. A HF‐Calculation for the 10, 18, and 36 Electron Closed Shell Ions of X‐Ray Scattering Factors, Diamagnetic Susceptibilities, and Dipole Polarizabilities
Authors: Schmidt P. C. , Sen K. D. , Weiss Alarich
Published: August 2012

The diamagnetic susceptibilities χd, the dipole polarizabilities αD, and the atomic form factors f are calculated for 10, 18, and 36 electron closed shell ions (Na⊕, Mg2⊕, Al3⊕, N3⊖, O2⊖, F⊖, K⊕, Ca2⊕, P3⊖, S2⊖, Cl⊖, Rb⊕, Sr2⊕, Br⊖). Three effects on the physical properties are studied

the quantum mechanical method to calculate the wave functions;

the influence of the spherical crystal potential on the wave functions and

the inclusion of self consistency in deriving αD from the wave functions.

The investigation of the polarizability shows that the best choice for the crystal potential is to adjust the charged compensating sphere to the Madelung potential; thereby agreement between experimental and theoretical data is good. — Deviations of atomic form factors for crystal ions from free ion values are high; for soft ions such as N3⊖, O2⊖, and S2⊖ f is changed up to 18% (N3⊖) near sin ϑ/λ = 0.1 Å−1 compared to the quasi free ion value. From the crystal ion atomic scattering factors ffree ion is deduced by extrapolation for the unstable free ions N3⊖, O2⊖, and S2⊖.
Invariant expansion coefficients of the molecular pair correlation function of ZX4‐systems
Authors: Steinhauser O. , Bertagnolli H.
Published: July 2012

The general relationship between atom pair correlation functions gαβ(R) and the expansion coefficients gn1n211l2l12(R12) of the generalized pair correlation function g(R12, Ω1, Ω2, Ω12) is presented and tested numerically with the aid of the results of a computer simulation of liquid CCl4. For the structure factor of ZX4‐systems a symmetry adapted expansion in terms of g n1n2l1l2l12(R12) is given together with the corresponding molecular form factors. In evaluating the g‐coefficients a cartesian representation was used instead of Eulerian angles. It is shown how one can extract principal molecular configurations by a detailed g‐coefficient analysis.
An ESR study of TiO2 treated with atomic hydrogen
Authors: Serwicka E. , Schindler R. N. , Schumacher R.
Published: July 2012

Powdered TiO2 samples were reduced by hydrogen plasma treatment at room temperature. The ESR spectra reveal the formation of Ti3+ ions with similar concentrations as obtained in samples which were reduced conventionally, i.e. at elevated temperature either in vacuo or with hydrogen gas. The effect of O2 adsorption on plasma and conventionally treated TiO2 samples is compared and discussed.
Ultrahigh vacuum cryostat for spectroscopy and laser‐induced processes
Authors: Heidberg Joachim , Stein Helmut , Hoefs Eugene
Published: July 2012

An ultrahigh vacuum cryostat consisting of a stainless steel body flanged to an analyzer cell for spectroscopy and laser‐induced processes in the entire spectral region between ca. 50 and 0.2 μm at base pressures in the low 10−10 mbar range and sample temperatures between 10 and 600 K is described for the first time. ‐ Under helium bath operation, (4 ± 1) K was measured on the sample holder and (10 ± 2) K in the sample without using thermal contact materials. The metal to metal joint between helium reservoir (stainless steel) and sample holder (OFHC copper) according to the conflat flange method proved to be tight for many baking cycles. The integral leak rate of the whole ultrahigh vacuum apparatus as well as the optical transmission are reported. The windows developed do not show irradiation effects at peak intensities of 10 MW · cm−2 per CO2 laser pulse. The cryostat is equipped with a quadrupole mass spectrometer and evaporation sources for salts and metals. The analyzer cells are compatible with the sample chamber dimensions of most commercial spectrometers. ‐ Examples of applications are presented in the fields of low temperature gassolid interaction, cryospectroscopy of stable and new metastable adsorbates, selective and efficient evaporation and desorption induced by laser infrared.
Vibrational nonadiabatic model calculations on the unimolecular cis‐trans isomerization of dideuteroethylene
Authors: Russegger P.
Published: July 2012

With the aid of a model hamiltonian for the isomerization‐ and vibrational motions, we have investigated the quantum dynamics of the cis‐trans isomerization of dideuteroethylene. The importance of nonseparability of the motion along the reaction coordinate and the other degrees of freedom is demonstrated by means of the differential rate constants — Comparison with the statistical theories of unimolecular reactions is also presented.
Absolute measurements of the thermal conductivity of liquids at pressures up to 500 MPa
Authors: Menashe J. , Wakeham W. A.
Published: July 2012

An apparatus for the accurate measurement of the thermal conductivity of liquids is described. The instrument, which is of the transient hot‐wire type, operates over the pressure range 0.1 to 700 MPa and the temperature range 20–200°C. The precision of the thermal conductivity measurements is estimated to be one of ±0.2% over the entire range. — Experimental data are reported for the thermal conductivity of n‐heptane in the temperature range 35–75°C and the pressure range 50–500 MPa. The accuracy of the present results is estimated to be one of ±0.5%, which is slightly worse than their precision because the lack of suitable data for the optical properties of the liquid at high pressures only allows an approximate correction to be applied for the systematic effects of radiative heat transfer. Along an isochore the thermal conductivity of n‐heptane is found to increase with temperature although along an isobar the temperature derivative is negative. The density dependence of the thermal conductivity is almost independent of temperature.
Doppelkaskaden‐Knudsenzelle zur Dampfdruckuntersuchung an Arsenolith und Claudetit
Authors: Bradaczek H. , Denzer P. , Woköck H.‐D.
Published: July 2012

The twin cascaded Knudsen cell makes possible improved comparative measurements of effusion processes on sample pairs exhibiting widely differing evaporation temperature ranges. Investigating the polymorph system Arsenolite‐Claudetite no significant differences in the evaporation behaviour of both polymorphs can be found.
Arrhenius Parameters for the System (CH3)3Si + D2 ⇄ (CH3)3SiD + D. The (CH3)3Si — D Bond Dissociation Energy
Authors: Ellul R. , Potzinger P. , Reimann B. , Camilleri P.
Published: July 2012

The Arrhenius parameters of the reaction (3)
equation image
have been determined relative to the recombination of the trimethylsilyl radicals
equation image
yielding EA (3) — 1/2EA(6) = 67 ± 6 kJ mol−1 and A(3)/A (6)1/2 = 10−7±0.5 cm3/2 s−1/2. The rate constant for the back reaction (‐3)
equation image
has been determined to be
equation image
.

Assuming a negligible activation energy for the recombination reaction (6) gives HD0((CH3)3Si — D) = 388 ± 7 kJ mol−1 in accordance with the accepted literature value. In the experimental part a pulsed Hg sensitized photolysis‐resonance absorption technique is described to obtain rate constants for hydrogen atom‐molecule reactions. For testing the apparatus the rate constants
equation image
at room temperature have been determined.
The Effect of Some Surface Treatments on the Characteristics of the Cd‐Chalcogenide/Polysulfide Schottky Barrier
Authors: Tenne R.
Published: July 2012

A potentiostatic study of Cd‐chalcogenide/polysulfide Schottky junction, was undertaken. The effect of various surface preparation techniques, in particular photoelectrochemical etching [1, 2] upon the properties of the junction was studied and analyzed in terms of thermionic emission over the Schottky barrier, surface roughness and tunneling through an insulating layer. It has been found that close to the flat band situation the time course of the current is not the same as at small forward bias and it is suggested that the potential distribution within the Helmholtz layer is changed leading to unpining of the bands. Implications to the optimalization of the performance of photoelectrochemical cells are discussed in brief.
Vibrational Relaxation in Liquids with Rather Strong Intermolecular Interactions
Authors: Scheibe D. , Döge G.
Published: July 2012

To understand more about vibrational relaxation in liquids with rather strong intermolecular interactions, the Ramanband of the C = O‐stretching vibration of methyl ethyl ketone was measured in a temperature range from 233 to 343 K, and at 293 K in various solvents changing the concentration. — An interpretation for the behaviour of such polar bands in terms of dipole‐dipole interactions was evaluated in the frequency picture. This allows to explain, at least qualitatively, the variation of band shape parameters under different conditions.
Viscosity of Acidic Lithium Chloroaluminate Melts
Authors: Tørklep K. , Øye H. A.
Published: July 2012

The viscosity of LiCl — AlCl3 melt mixtures has been determined in the range 0.50 ≦ XAlCl3 ≦ 0.80, 110°C to 300°C. The method, which utilizes closed cylindrical cups subjected to vapour pressures exceeding 11 atm, is absolute and requires no calibration against reference liquids. Results are corrected for surface effects. Applying Arrhenius temperature dependencies and the Arrhenius mixing rule, the viscosity is expressed as a function of temperature and composition with an overall standard deviation of 0.22% when the presence of AlCl4−, Al2Cl7−, Al3Cl10−, and Al2Cl6 is assumed. The results are also discussed with respect to an earlier study of the NaCl—AlCl3 system.
Interaction of CFCl3 with an Fe(100) Surface Part II: Adsorption and Decomposition at Ambient Temperatures
Authors: Dowben P. A. , Grunze M. , Jones R. G. , Illenberger E.
Published: July 2012

In the second part of our communication on CFCl3 adsorption on an Fe(100) surface we present the results obtained for room temperature adsorption and annealing the adsorbate covered surface up to 800 K. Dissociative adsorption at 300 K proceeds with a high and constant sticking coefficient which is explained by the long lifetime (>3 ± 10−5 s) of the molecule in the extrinsic precursor state. Chlorine adsorbs on the surface forming a noncoincidence overlayer raft while carbon and fluorine are absorbed in the selvedge. These absorbed atoms have a distinct influence on the surface structure and the stability of the chlorine overlayer. Absorbed fluorine stabilizes the chlorine overlayer up to 700 K, which is a significantly higher temperature than observed for the stability of chlorine overlayers formed by Cl2 or CCl4 adsorption.
Two Photon Spectroscopy of Dipole Forbidden Transitions III. Experimental Determination of Two Photon Absorption Spectra Including Polarization Control
Authors: Dick B. , Gonska H. , Hohlneicher G.
Published: July 2012

A new experimental technique is described which allows the measurement of two‐photon absorption spectra of luminescent molecules and simultaneously the evaluation of the two‐photon polarization parameter Ω over a wide spectral range. The resolution obtained is comparable to conventional UV absorption and polarization spectra. Examples are shown for different types of unsaturated hydrocarbons. The influence of S1 → Sm excitations and of variations of the profile of the exciting laser pulse are discussed. It is shown that careful control of both the quadratic nature of the two‐photon process and the beam profile is essential to avoid artificial features in wide range two‐photon spectra.
Electron Correlation in Weakly Coupled Transition Metal Compounds: Poly‐Decker Systems
Authors: Böhm Michael C.
Published: July 2012

The Thouless instability conditions in the poly‐decker sandwich compounds 1–8 have been investigated by means of semiempirical INDO calculations. Hartree‐Fock (HF) fluctuations of the singlet, non‐singlet (triplet) and non‐real type have been detected. The reasons for the various instability conditions are analysed. The charge density waves (CDW) of the singlet route are of helical type, the spin density wave (SDW) of the non‐singlet route corresponds to a longitudinal modulation. Singlet fluctuations in complexes with identical 3d centers are the result of intraatomic angular and interatomic left‐right correlation. The non‐singlet variation corresponds to a spin decoupling between the two 3d centers. The HF instabilities in the closed shell species 1 – 8 are compared with doublet fluctuations in open shell complexes and are extrapolated to infinite polymer chains.
Phase Transition of the Bilayer Membrane of Synthetic Dialkyl Amphiphiles as Studied by Differential Scanning Calorimetry
Authors: Okahata Yoshio , Ando Reiko , Kunitake Toyoki
Published: July 2012

The phase transition behavior of dilute aqueous solutions of the bilayer membrane of dialkyl (C12 to C18 in most cases) amphiphiles was investigated by differential scanning calorimetry (DSC). The extent of the sample dispersion affected the DSC behavior for dialkyl amphiphiles with ammonium, phosphate and sulfonate head groups. The well‐sonicated aqueous sample of the ammonium amphiphiles showed broader transition peaks at lower temperatures than the corresponding frozen sample did. The discrepancy became less pronounced when the interacting group was introduced at or near the head group. The wel DSC behavior was not observed for amphiphiles with nonionic (polyoxyethylene) and zwitterionic (phosphocholine) head groups. The phase transition temperature (0 – 80°C) was enhanced progressively with increasing alkyl chain lengths (C12 to C18), but the transition enthalpy (2–12 kcal/mol) did not obey simple relations.
The Pressure Dependence of the Excess Enthalpy of Mixtures of Isopropanol with Heptane and Isooctane up to 553 bar
Authors: Heintz A.
Published: July 2012

Excess enthalpies HE of isopropanol + n‐heptane and isopropanol + isooctane mixtures are reported measured at 298 K and various pressures up to 553 bar. The HE values are endothermic and show a remarkable decrease with pressure. The real associated solution model has been applied taking into account the volume change due to hydrogen bonding of the alcohol and was found to be insufficient for describing quantitatively the pressure dependence observed.
Characterization of the Order/Disorder Transition of Poly‐1‐Methyl Adenylic Acid in Neutral Solution by Raman Difference Spectroscopy
Authors: Klump Horst , Sturm Jean , Peticolas Warner L.
Published: July 2012

A detailed analysis of the hypo‐ and hyper‐chromic intensity changes as well as the changes in frequency and band shape in the Raman spectra of poly(m1A) upon melting has been made using a newly developed Raman difference technique. An interpretation of these changes allows us to suggest a structure for the double‐helix of this polymer in neutral solution which resembles that of poly(A) in acid pH. In the helix the backbone geometry is shown to be similar to the C 3 endo or A genus and the existence of a hydrogen bond is inferred from the asymmetric band shape of 1100 cm−1 PO−2 stretching vibration wich is not found either in self‐stacked poly(A) at neutral pH. It is expected that the application of the Raman difference technique will result in a detailed description of conformational features of these important macromolecules which cannot be drawn from the resuits of other optical methods.
Katalysatoraktivitäten α, Gleichgewichte und Kinetik in den homogenen Bulk‐H2‐Transfer‐Reaktionen als Funktion der H2‐Donatoren und Acceptoren
Authors: Graser Barbara , Strohmeier Walter , Marčec Radovan , Steigerwald Hannelore
Published: July 2012

Ketons are reduced under mild conditions to the corresponding alcohols by secondary alcohols in homogeneous bulk hydrogen transfer reactions, catalysed by Ru(CF3CO2)2CO(Pø3)2. The reactions are reversible, the equilibrium constants vary from 0.1 to 21, and under optimized conditions time to establish equilibrium varies from 5 to 90 minutes at 140°C. The rate determining step seems to be the dehydrogenation of the alcohols. The conversion can be described by the rate law of a reversible second‐order reaction.
Photoelectrochemical Cells for the Oxidation of Water and Bromide Ions by Visible Light
Authors: Neumann‐Spallart Michael , Kalyanasundaram K.
Published: July 2012

Anodic oxidation of water to molecular oxygen and of bromide ions to Br2 photosensitized by tris‐bipyridylruthenium(II), Ru(bpy)32+, has been investigated in photoelectrochemical cells. An irreversible photoredox reaction between Ru(bpy)32+ and electron acceptors (S2O2–, Tl3+, Co(NH3)5Cl2+) generates Ru(bpy)33+ which is reduced at the cathode (Pt or Carbon) with concomittant oxidation of H2O or Br− with RuO2, Pt (or Carbon) anodes respectively. Cell performances have been examined in terms of photocurrents, potentials under illumination, stability, turn‐overs, and the data explained in terms of i‐e curves of the redox couples involved in Evans‐type diagrams. Under optimal conditions, photocurrents upto 10 mA (with a 250 W lamp) have been drawn and 2 · 10−4 mdes Br2 generated in one hour photolysis. Possible extensions, scope and limitations are discussed.
Wechselwirkungskräfte in flüssigen Dünnschichten
Authors: Lyklema J.
Published: July 2012

The forces operating in thin liquid films of colloidal dimensions are reviewed. These forces are: Van der Waals (dispersion‐), electrical and steric interactions. A discussion is given on their evaluation in situations of practical interest, including dynamic conditions. The review covers both symmetrical and asymmetrical films. A few examples are given to indicate possible applications.
Interfacial Convection
Authors: Sawistowski H.
Published: July 2012

Interfacial convection is a general term used for the description of surface flow produced by the appearance in the interface of gradients of surface parameters. It embraces three types of phenomena: Marangoni instabilities, Marangoni disturbances and thin‐film behaviour. Each of them is discussed in turn and criteria presented for their appearance. Finally, practical implications are described in terms of effects on mass transfer coefficients, interfacial area and hydrodynamic behaviour of mass transfer equipment.
Conformal‐Solution‐Theorie für Mischungen konvexer Moleküle
Authors: Naumann K.‐H. , Chen Y. P. , Leland T. W.
Published: July 2012

The Hard Spheres Expansion Conformal Solution Theory [1], originally developed to predict the thermodynamic properties of mixtures of spherical molecules, is generalized for the treatment of fluids that are composed of particles interacting via Kihara type potentials [2].—A perturbation expansion is generated by dividing the intermolecular pair potential into a repulsive and an attractive part. The hard‐core reference system is represented by a mixture of hard convex bodies. It's thermodynamic functions are obtained from a new accurate equation of state. The attractive contributions are evaluated from the known attractive interactions of a pure reference fluid using the principles of conformal solution theory and a new type of pseudoparameters.—A method for the determination of temperature and density dependent effective hard‐core parameters is presented.
Influence of Water on the Capacitance/Potential Distribution at the TiO2/CH3CN Junction
Authors: Heinzel A. B. , Teschner D. M. , Schumacher R.
Published: July 2012

It is reported on changes of the flat band potential Vfb at the n‐TiO2/CH3CN junction upon water addition. It is shown that these shifts are related to the increasing density of H+ ions in the CH3CN electrolyte by adding water to it. The results are discussed in terms of specific adsorption of H+ ions at the TiO2 electrode that affects the potential/capacitance distribution of the junction.
Bestimmung der Elektronendichte in Hochfrequenz‐Entladungen mehratomiger Gase
Authors: Kruppa G. , Suhr H. , Janzen G. , Staib W.
Published: July 2012

Electron densities ne have been measured in rf plasmas of He, Ar, H2, N2, O2, CO, CO2, H2O, SO2, NH3, CH4, CH3NH2, CH3NO2, CH3OH, CH3OCH3, C2H5OC2H5, CH3COCH3, CH3COOH, CH3COOCH3, and trans‐CH3CHCHCH3. Electron densities ranged from 3 · 108 cm−3 to 23.4 · 1010 cm−3. At constant rf power log ne decays linearly with distance from the end of the exciter coil. A rise in pressure increases ne of He and Ar and decreases ne for the other gases. Some gases show a linear dependence and others a quadratic or mixed dependence of ne, on the rf power. This can be correlated to differences in ionisation processes. Electron densities in plasmas of organic compounds resemble eachother very closely but differ significantly from the ne values of He, Ar, H2, and O2.
Direct Measurement of Single Ionic Drift Velocities in Electrolyte Solutions. An NMR Method
Authors: Holz Manfred , Müller Christian
Published: July 2012

The theoretical and experimental principles of a novel method for the direct and rapid measurement of single ionic drift velocities in electrolytes are presented. The method is based on an NMR flow measuring technique and the velocity information is obtained through the observation of the spin‐echo amplitude in the presence of a pulsed magnetic field gradient and a pulsed electric field. It allows the determination of ionic mobilities and transference numbers in a more “direct” way than the classical electrochemical methods. First experimental results for (C2H5)4N+‐ions in aqueous solution are shown. Advantages, disadvantages and possible applications of this new NMR method in electrochemistry are discussed. It seems that the method has special advantages for measurements of electrical transport data in solutions of mixed electrolytes. The observation ot solvent motions in conducting electrolyte solutions could also be a possible application.
Mechanistic Studies on the Solvent Exchange at Co(II)‐Ions in Mixtures of Weak and Strong Donors
Authors: Dickert F. L. , Hellmann S. W.
Published: July 2012

With 1H and 31P NMR‐spectroscopy the solvation of Co(II)‐ions in mixtures of weak donors (methanol) and strong donors (dimethylformamide, hexamethylphosphoric acid triamide) was studied. In comparison with the complexes in the respective pure solvents, the ligand exchange rates of the strong donors are diminished and those of the weak donors are increased. These measurements yield information about the mechanism of the solvent exchange at metal ions and can be understood according to a donor‐acceptor model.
The Heats of Formation of Some Arsenates
Authors: Kubaschewski Oswald , Itagaki Kimio
Published: July 2012

A recently constructed isoperibol calorimeter has been modified to measure the spontaneous reactions of Li2O, Na2O, CaO, and BaO with As2O5 after ignition. Thus, the heats of formation from the component oxides have been determined for Li3AsO4, Na3AsO4, Ca3As2O8, and Ba3As2O8.
Lasers in the Study of Elementary Processes
Authors: Smith Ian W. M.
Published: July 2012

Applications of lasers in the kinetic study of elementary process are reviewed under three headings: (i) thermal rate constants, (ii) intermolecular and intramolecular energy transfer, and (iii) state‐to‐state reaction kinetics. The limitations, as well as the potential, of laser‐based techniques are illustrated and some areas of potential development are indicated.
Excess and Interaction Second Virial Coefficients for Ten Binary Gaseous Systems Containing SF6
Authors: Martin M. L. , Trengove R. D. , Harris K. R. , Dunlop Peter J.
Published: July 2012

Excess and interaction second virial coefficients have been measured over the temperature range 290 – 320 K for binary systems of SF6 with He, Ne, Ar, Kr, Xe, N2, O2, CO2, CH4, and CF4. The excess virial coefficients are estimated to have an accuracy of 0.2 cm3 mol−1 and have been used to calculate molar excess enthalpies for each system at 300 K.
Lennard‐Jones (12,6) Parameters for the Non‐Ionic Contributions to Interionic Pairpotentials of Alkali Cations and Halide Anions from Crystal Data
Authors: Fischer Walter , Brickmann Jürgen
Published: July 2012

Lennard‐Jones (12,6) parameters for the pair interaction potentials of the alkali cations and halide anions were calculated on the basis of different alkali halide crystal data. Averaged values ϱ¯ and ϵ¯ were obtained by fitting the Buckingham type potential functions of Sangster and Dixon [15] for each individual alkali halide crystal. It was demonstrated, that these values can be used to predict unknown interaction potentials between unlike particles using the combination rules of Lorentz‐Berthelot [24] or those of Kong [18]. In particular it was shown, that the averaged parameters ϱ¯ and ϵ¯ lead to better results than the corresponding values originating from noble gas atoms.
Photocatalytic cis→trans‐Isomerization of Thioindigoid Dyes
Authors: Klages C. P. , Kobs K. , Memming R.
Published: July 2012

The trans‐isomers of certain thioindigoid dyes in dilute solutions can be completely converted to the cis‐isomer by selective excitation of the trans‐isomer. At higher dye concentrations the conversion is limited. The corresponding photostationary state is determined by two processes in opposite directions: (i) by the usual trans→cis photoisomerization and (ii) by an inverse cis→trans isomerization initiated by excitation of the trans‐isomer. An analysis of this peculiar effect has shown that the trans‐triplet catalyses the cis→trans‐isomerization.
Far Infrared Spectra of Strongly Polar Molecules in Solid Solution. II. Hydrogen Cyanide
Authors: Knözinger Erich , Wittenbeck Rüdiger
Published: July 2012

Far infrared matrix isolation spectroscopy of hydrogen cyanide establishes the presence of monomers, linear dimers, and linear multimers in solid Ar. Information is obtained concerning the motion of monomer molecules relative to the cage as well as the intermolecular vibrational behaviour of the dimer. – The comparison with similar studies in the mid IR reveals the high potential of the application of far IR spectroscopy of matrix‐isolated samples to the investigation of association phenomena and intermolecular interactions.
Raman Spectra of Carbon Dioxide and Its Isotopic Variants in the Fermi Resonance Region: Part III. Analysis of Rovibrational Intensities for 12C16O2, 13C16O2, 12C18O2 and 12C16O18O
Authors: Finsterhölzl H.
Published: July 2012

The present work deals with the intensity analysis of rovibrationally resolved Raman spectra of natural and 13C as well as 18O isotopically enriched samples of CO2 photoelectrically recorded in the Fermi resonance region (1100–1460 cm−1). Based upon Chedin's set of rovibrational data [1] and upon the polarizability theory of Raman scattering, we have successfully fitted our calculated intensities to the measured spectra of each isotopic species. — The procedure yields values for three parameters, namely (δ2ƒ‐I0/δq2,+ ;δq2,‐) (δƒ‐I0/δq1) = ‐ 0.200 and ‐ 0.100 (± 3%) for t = 0 and t = 2, respectively, and |(δƒ‐00/& dgr;q1/δ ƒ‐20/δq1)| ≈ 1.47 ± 2%, that are derived from the spherical polarizability tensor ƒ‐Iq. A spectroscopic temperature can be evaluated within error limits of less than ± 1%.
Studies of the Energetics and Structures of Clusters of Molecules about Ions Utilizing High Pressure Mass Spectrometer and Laser Photodissociation Techniques
Authors: Castleman A. W. , Holland P. M. , Hunton D. E. , Keesee R. G. , Lindeman T. G. , Peterson K. I. , Schelling F. J. , Upschulte B. L.
Published: July 2012

The results of studies of ion cluster bonding contribute knowledge of the interaction potential between ions and molecules, as well as an understanding of the microscopic details of solvation, surface and nucleation phenomena. For a number of years we have employed a high pressure mass spectrometric technique to measure the bond energies for the successive attachment of several classes of polar molecules to a variety of anions and cations. A comparison of data for ions of both open and closed electronic structure shows a strong disposition for partial co‐valent bonding with ligands of various classes. The importance of the dipole moment and the polarizability of the ligands in governing their bonding to ions is discussed. — Laser‐induced photodissociation studies are of value in determining the structure and photostability of ion clusters as well as in probing the changing properties of negative ions as a function of the degree of clustering with ligands. Experiments were undertaken in our laboratory to elucidate the mechanisms of photodissociation of CO3− co‐clustered with water. Photodissociation cross sections and reaction channels in the energy range 1.9 to 2.2 eV are discussed.
On the Concentration Dependence of the Mean Aggregation Number of Ionic Micelles as Determined by Stopped‐Flow Experiments
Authors: Baumgardt K. , Klar G. , Strey R.
Published: July 2012

The analysis of the amplitudes in T‐jump experiments on aqueous micellar solutions yields the dependence of the critical micelle concentration and the mean aggregation number m of the micelles on temperature, whereas p‐jump experiments yield the corresponding dependence on pressure. In this paper we have, accordingly, evaluated the dependence of m on the total detergent concentration from stopped‐flow amplitudes (i.e. from concentration‐jump experiments). The experiments were performed on H2O‐NaDS and H2O‐NaDS. It turned out that the mean aggregation number of these detergents appears to increase with increasing detergent concentration, in accord with the results of other authors who have found an increase of m with increasing concentration of an added electrolyte.
Vorspiel Ohne Finale (?)
Authors: Steiner Josef
Published: August 2012

Seit mehr als einem Jahrzehnt wird auf nationaler und europäischer Ebene intensiv über die Notwendigkeit des Abbaus von bürokratischen Regelungen diskutiert. Allgemein besteht aber dennoch der Eindruck, dass vorwiegend aus Brüssel immer neue Verordnungen über die EG‐Mitgliedsländer hereinbrechen und dort – oft mit viel Mühe und Aufwand – in nationales Recht umgesetzt werden (müssen). Aus diesem Regelungsdickicht sind für den Bereich des Bauens vor allem zu nennen:

– Die Qualitätsmanagementregeln nach ISO 9000

– Die Dienstleistungsrichtlinie

– Das Antidiskriminierungsgesetz

– Das Gesetz über Wettbewerbsbeschränkung

– Die aufwendige Harmonisierung der Europäischen technischen Baubestimmungen

– Die europäische Richtlinie über die Verfahren zur Vergabe öffentlicher Bauaufträge, Lieferaufträge und Dienstleistungsaufträge (VOF)

Diese und weitere Gesetze und Verordnungen haben vor allem für Architekten und Bauingenieure den Aufwand für die Projektbeschaffung und für die Projektbearbeitung erheblich vergrößert.

Prelude without Final. Experience with the Regulations of Contract Awards for Independent Professional Services – VOF –

The need to reduce the bureaucratic regulations at the national and European level has been discussed thoroughly for over a decade. Even so, there is the general impression that new directives are being foisted on EU member states from Brussels where they (must then) be implemented in national legislation, frequently with considerable difficulty and expense. From amongst the jungle of regulations where the civil engineering sector is concerned, those requiring special mention are:

– The quality management regulations according to ISO 9000

– The services directive

– The antidiscrimination law

– The law on the restriction of competition

– The complicated harmonization of European technical building regulations

– The European directive concerning the procedures for the award of public works contracts, public supply contracts and public service contracts (VOF)

For architects and civil engineers in particular, these and other laws and directives have considerably increased the project procurement and project handling costs.
Bioreactor environment‐sensitive sentinel genes as novel metrics for cell culture scale‐down comparability
Authors: Kondragunta Bhargavi , Joshi Bharat H. , Han Jing , Brorson Kurt A. , Puri Raj K. , Moreira Antonio R. , Rao Govind
Published: July 2012

Scale‐down of bioreactors is currently done based on matching one or more measurable parameters such as kLa and P/V, which could result in insufficient process comparability. Currently, there is a lack of genomic translational studies in cell culture scale‐down, which could help delineate measurable cellular attributes for improved scale‐down. In this study, we scaled‐down from a typical bench‐scale 5‐L bioreactor to a novel high‐throughput 35‐mL minibioreactor based on matching oxygen transfer rate, which resulted in cell growth and product‐related discrepancies using Sp2/0 cells. Performing DNA microarrays on time‐course samples from both systems, we identified ∼200 differentially expressed transcripts, presumably because of bioreactor aeration and mixing differences with scale‐down. Evaluating these transcripts for bioreactor‐relevant cellular functions such as oxidative stress response and DNA damage response, we chose 18 sentinel genes based on their degree of difference and functionality, which we further verified by quantitative real‐time polymerase chain reaction (qRT‐PCR). Tracking the differential expression of Sod1, Apex1, and Odc1 genes, we were able to correlate sparging‐related damage and poor mixing, as possible causes for physiological changes such as prolonged culture in minibioreactors. Additionally, to verify our sentinel gene findings, we performed follow‐up improved scale‐down studies based on gene analysis and measured transcriptomic changes. As a result, qRT‐PCR‐based genomic profiles and cell growth profiles showed better convergence between the improved minibioreactor conditions and the model 5‐L bioreactor. Our results broadly show that based on the knowledge from transcriptomic changes of sentinel gene profiles, it is possible to improve bioreactor scale‐down for more comparable processes. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2012
The monro bell controversy
Authors: Pearce J.M.S.
Published: August 2012

Amongst the contributions in anatomy and surgery of the celebrated Monros was the contentious “discovery” by Monro Secundus of the interventricular foramen. Monro's account (1783) was vehemently criticized in London, especially by Charles Bell for presuming to describe something which was already well known and for inaccuracies. Monro with some justification in 1797 disputed this attack, although his anatomical description was shown by later anatomists to be mistaken. Clin. Anat. 26:793–799, 2013. © 2012 Wiley Periodicals, Inc.
Usefulness of transesophageal echocardiography during implantation of the CoreValve percutaneous aortic prosthesis: Influence of the learning curve
Authors: del Campo Laura Cejudo Díaz , Rubio Dolores Mesa , Ortiz Martin Ruiz , Ortega Mónica Delgado , Pan Manuel , Pineda Soledad Ojeda , Fernandez Elena Villanueva , Aguilera Jose Lopez , de Lezo Jose Suarez
Published: August 2012

Background and Objectives: The purpose of this study was to evaluate the usefulness of transesophageal echocardiography during the implantation of the CoreValve percutaneous aortic prosthesis and the influence of the learning curve in its indications. Methods: From April 2008 to January 2010, 53 patients were treated for symptomatic severe aortic stenosis with a CoreValve percutaneous aortic prosthesis. Transesophageal echocardiography was performed during the procedure for two reasons: if a discrepancy between the measures of the aortic annulus arose before the implantation and to provide visualization if a complication occurred during the procedure. Patients were divided in to two groups based on the learning curve (group I:the first 25 patients, group II: all of the subsequent patients). Results: Thirty‐six transesophageal echocardiographies were performed on 28 patients (53%).In 15 cases the indication was to assist us in determining the proper sized prosthesis, and in the other 21 cases it was performed due to a complication during the procedure. The numbers of intraprocedure transesophageal echocardiographies were similar in both learning‐curve groups, (64% in group I vs. 71% in group II, P = 0.56) but the proportion of the studies indicated by serious complications was significantly lower in the second period of the learning curve (67% in group I vs. 17% in group II, P < 0.05). Conclusions: In our experience, transesophageal echocardiography was very useful in more than one‐half of the patients during the implantation of the CoreValve percutaneous aortic prosthesis. After overcoming the learning curve, its indication due to serious procedure‐related complications decreased significantly. © 2012 Wiley Periodicals, Inc.