bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes of vibrational modes upon melting mercury (II) halides
Authors: Voyiatzis G. A. , Papatheodorou G. N.
Published: July 2012

Raman spectra of the “molecular” polycrystalline solids HgCl2 (D), HgBr2 (C) and of the yellow form of HgI2 (C) were measured from LN2 up to premelting temperatures. Polarized Raman spectra of molten HgX2 (X = Cl, Br, I) were measured at temperatures up to 950 K. The pure rotational band contour and the vibrational rotational contour of the HgX2 vapors were also measured. Upon melting the vibrational modes of the high temperature solid appear to be preserved. The spectra of the three liquids are similar and are best correlated to the spectra of the D (HgCl2) solid and the vibrational modes of the HgX2 molecules. Reduced Raman spectra of the liquids show splitting of the stretching mode to a doublet, ν1 (A1) and ν1 (B2g), which is attributed to strong intermolecular coupling. The ν2 and ν3 internal modes of the solid are also transferred into the melt. The predominant features of the low frequency reduced spectra is a band, VR, which is assigned to the rotatory modes of the HgX2 molecules and can be correlated to both the rotational band contour of the vapor and the librational modes of the solid. With increasing temperature the spectra of the liquid show softening of the rotatory modes and a blue shift of the ν1 mode, both implying weakening of the intermolecular coupling. An overall decrease in the Raman intensity of the liquid spectra with increasing temperature is attributed to the rapid molar volume increase.
Longitudinal relaxation rates of7Li in concentrated solutions of LiNO3in 1,3‐diaminopropane in the liquid state
Authors: Hayashi Hirokazif , Nakamura Yoshio , Shimokawa Shigezo
Published: July 2012

The temperature and concentration dependencies of7Li longitudinal relaxation have been investigated for concentrated solutions of LiNO3in 1,3‐diaminopropane in the liquid state. The experimental longitudinal relaxation rates (R1) of7Li are interpreted as the sum of the quadrupolar and the dipolar contributions. The dipolar contributions are estimated from the assumed local structure of solutions and the assumption that the correlation times of the quadrupolar and dipolar interactions are identical. Then, the quadrupolar contributions are separated from the experimentalR1, values and described by the electric field gradient (EFG) at the7Li nucleus and its reorientational correlation time (τ). The temperature dependence of τ deviated from a simple Arrhenius law over the temperature range studied. The composition dependence of τ and EFG show bends at around 30mol% LiNO3. This is consistent with the previous results obtained from the electrical conductance, and suggests that solvent molecules may act as bridges between Li+ions at higher concentrations of LiNO3.
Studies on the molecular motion of [M(daco)2]2+ Ions in bis‐daco complexes of MX2 (M = Cu(II) and Ni(II) and X = ClO4 or NO3; daco = 1,5‐diazacyclooctane)
Authors: Koner Subratanath , Ohki Hiroshi , Kikuchi Hikomitsu , Ikeda Ryuichi
Published: July 2012

The temperature dependence of the second moment (M2) of 1H NMR absorption of the partially deuterated (deuterated amine protons) complexes [M (daco‐d2)2] X2 · n D2O (M = Cu(II) and Ni(II); daco = 1,5‐diazacyclooctane; X = ClO4 or NO3; n = 0 for X = NO3 and n = 2 for X = ClO4) has been measured. Among them, [Cu(daco‐d2)2](NO3)2 showed a distinct drop in M2 at the same temperature region (ca. 363 K) where the complex is reported to undergo the thermochromic phase transition. The complexes [Cu(daco‐d2)2](ClO4)2·2D2O and [Ni(daco‐d2)2](ClO4)2·2D2O showed a gradual decrease of M2 around 220 and 280 k, respectively, without any colour changes and phase transitions, whilst M2 of [Ni(daco‐d2)2](NO3)2 shows no marked decrease with increase of temperature up to 400 K. M2 of rigid and motional lattices of [Cu(daco‐d2)2](NO3)2 is theoretically calculated using the reported X‐ray crystal structure data. The molecular motions of [Cu(daco‐d2)2](NO3)2, [Cu(daco‐d2)2](ClO4)2·2D2O and [Ni(daco‐d2)2](ClO4)2·2D2O are explained in terms of dynamic disorder of metal diamine chelate rings.
The electronic conduction mechanism of NiO‐crystals
Authors: Springhorn C. , Schmalzried H.
Published: July 2012

Electrical conductivity measurements with the transition metal oxide (Ni,Fe)O have been conducted at T = 1573 K and T = 1525 K and under various oxygen potentials in order to decide which conduction mechanism prevails. Electron ‐ hole (polaron) hopping in the cation ‐ sublattice and (O2p)‐band conduction had been proposed before. The measured conduction buckle with a pronounced maximum suggests that polaron‐hopping is the prevailing conduction mechanism for (Ni1‐xFex)1‐δO.
Investigation of the CH3 + NO reaction in shock waves
Authors: Hennig G. , Wagner H. G. G.
Published: July 2012

The reaction of CH3 + NO was investigated behind incident shock waves at temperatures between 1300 K and 2080 K. The formation of H atoms and of HCN was studied by time resolved UV absorption and by IR‐emission. OH measurements of Hoffmann et al. were reevaluated with the rate constant of this work. The rate constant for the reaction of CH3 + NO can be expressed by

k = (4.0 ± 0.8)·1012 exp (−(8500 ± 500) K/T) cm3 mol−1 s−1.

HCN was found to be the main final product of the reaction of CH3 + NO in the temperature range covered. The contribution of the H forming channels is around 20–25% to the main channel.
Prediction of vapor‐liquid equilibrium data from excess enthalpy data for alkanol/alkane mixtures by the extended real associated solution model
Authors: Cabañas A. , Coto B. , Pando C. , Renuncio J. A. R.
Published: July 2012

The prediction of Vapor‐liquid Equilibrium data (VLE) from excess enthalpy data (HE) for alkanol/alkane mixtures by means of the Hanks‐Gupta‐Christensen (HGC) method is examined. The Extended Real Associated Solution model (ERAS) for the excess Gibbs energy which combines the Kretschmer‐Wiebe linear association model with Flory's equation of state for chainlike molecules is used. In this prediction, the parameters of the ERAS model are evaluated by fitting the experimental HE data to the algebraic equation for the HE of this model. Results from this study indicate that the ERAS model leads to VLE predictions which are more accurate than those previously obtained when the HGC method was used in conjunction with the Continuous Linear Association model or the Wiehe‐Bagley model.
Interfacial tension between water and non‐polar fluids up to 473 K and 2800 bar
Authors: Wiegand G. , Franck E. U.
Published: July 2012

The method of the Pendant Drop or Standing Bubble is applied to measure interfacial tensions between water and nonpolar fluids to high temperatures and pressures. The high pressure cell with two sapphire windows and the auxiliary equipment with several feed autoclaves is described. The shapes and sizes (about 2 mm) of drops and bubbles are recorded with microscope and video camera. A digital image processing procedure was developed which permits fast, objective and precise determination of the contour parameters.

The six gases helium, neon, argon, nitrogen, methane, and propane have been investigated to 473 K (with nitrogen to 573 K) and (in part) to 2800 bar. Gas densities came close to liquid density values. For comparison, water plus liquid n‐hexane, n‐decane, and toluene was investigated to 473 K and 3000 bar. For these liquid hydrocarbons, the interfacial tension γ always increases with pressure. At 373 K for water‐n‐hexane γ is 41.8 mN/m at 100 bar and 47.3 mN/m at 2600 bar, respectively. In the water‐gas systems γ decreases with pressure and passes through a flat minimum around 1000 bar. For water‐nitrogen at 373 K γ = 52.5, 46.5 and 48.3 mN/m at 200, 1400 and 2800 bar. Only with water‐helium γ increases continuously with pressure.
Solvation and association of urea in aqueous solutions and mixtures of water with 1‐propanol
Authors: Hawlicka Ewa , Grabowski Roman
Published: July 2012

Self‐diffusion coefficients of urea have been measured at 25.0 °C in aqueous solutions and in mixtures of water with 1‐propanol, as a function of the urea concentration and of the mixed solvent composition. The hydrodynamic radius of urea has been calculated. It has been found that both in aqueous solutions as well as in 1‐propanol‐water mixtures dimers of urea, if they exist, do not play any role in the diffusion processes. Diffusion is, however, a collective process and motions of urea depend on the numbers of neighbours, therefore they are very sensitive on the structure of the solvent. The results have also confirmed the previous supposition that urea does not affect the water structure, but it does fit the water structure quite well. It has been also found that the solvation of urea is determined by the structure of the mixed solvent.
Li insertion into 2H—WS2: Electronic structure and reactivity of the UHV In‐situ prepared interface
Authors: Schellenberger A. , Jaegermann W. , Pettenkofer C. , Kamaratos M. , Papageorgopoulos C. A.
Published: July 2012

The interaction of UHV cleaved 2H‐WS2 crystals with Li deposited at room temperature and at 85 K has been investigated using synchrotron soft x‐ray photoemission. Depending on the Li concentration and the temperature, chemically different interfaces are observed: at 85 K, a small Li concentration x≤0.2 leads to an intercalation phase LixWS2, which can be described in terms of the rigid band model. An intermediate phase occurs for 0.2<x≤1.3. One product of this intermediate phase is assigned to W2S3. With higher Li concentrations, a decomposition reaction sets in producing Li2S and metallic W. This decomposition reaction is favoured by heating the system to 300 K. No intermediate phase is observed in the room temperature experiment. The crystal is directly decomposed producing Li2S and metallic W. The experimental results are discussed in relation to thermodynamic, electronic and kinetic effects.
Photoconductivity in poly(biphenylmethyl silylene)
Authors: Eckhardt A. , Yars N. , Wollny T. , Schnabel W. , Nešpůrek S.
Published: July 2012

Quantum yields of charge carrier formation, ϕ; (cc), in poly(biphenylmethyl silylene), PBMSi, and poly(methylphenyl silylene), PMPSi, have been determined at 23 °C with the aid of the xerographic discharge method. At F = 1 × 108 V/m and λinc = 330–360 nm: ϕ (cc) = 0.10 (PBMSi) and ϕ (cc) = 0.03 (PMPSi). Upon the addition of 2,3,5,6‐tetrachlorobenzoquinone (chloranil) at c = 3 mol%, to the polysilylene films, the quantum yields were increased: ϕ (cc) = 0.21 (PBMSi) and ϕ (cc) = 0.13 (PMPSi). The mobility of charge carriers μ in PBMSi is about one order of magnitude lower than in PMPSi. Upon addition of 3 mol% chloranil to PBMSi μ increased slightly.
Comment on “relaxation spectroscopy of electrolyte solutions: LiClO4 in tetraethyleneglycol dimethylether”
Authors: Schütz G. , Stockhausen M. , Firman Paul , Xu Meizhen , Eyring Edward M. , Petrucci Sergio
Published: July 2012

Radio frequency and microwave frequency complex dielectric permittivity ϵ* = ϵ′ ‐ iϵ″ data for LiClO4 in tetraglyme as well as similar previously published data for LiNO3 in liquid polyethylene oxides are reviewed. The reliability of the dielectric ion coefficient ϵ″d at concentrations C ≫ 0.1 M (obtained as the difference between the total loss ϵ″ and the conductance loss ϵ″x = 1.8×1012χ/f) is questioned for frequencies f ≤ 0.1 GHz. The interpretation of the dielectric spectra of LiClO4 (and of LiNO3) in polyethers is critically analyzed.
Translational diffusion in C60 and C70 fullerene solutions
Authors: Haselmeier R. , Holz M. , Kappes M. M. , Michel R. H. , Fuchs D.
Published: July 2012

Self‐diffusion coefficients D of C60 and C70 and of the solvent molecules C6H6 and CS2 have been investigated in liquid fullerene solutions by the 13C and 1H NMR pulsed field gradient techniques. The C60/benzene measurement is in good agreement with a recent report, while data obtained for C60/CS2 and C70/CS2 are first measurements. The C70 number reflects the only diffusion measurement yet carried out on this molecule. Data were obtained with 5% 13C enriched fullerenes at 298 K. The sample preparation and the separation of 13C enriched C60 and C70 is described. The fullerene diffusion data are in excellent agreement with values predicted by the Stokes‐Einstein equation, however, under slip boundary conditions. In CS2 solution we find D(C60) = (1.85±0.18) × 10−9 m2s−1 and D(C70) = (1.56±0.16) × 10−9m2s−1 at 298 K, thus showing that fullerenes differing slightly in shape can be discriminated via their diffusivity. C70 may be regarded as an ideal ellipsoidal particle for the test of theories of diffusion. Our experimental result for C70 indicates that the long semi‐axis of the ellipsoid determines the diffusion behavior. Preliminary temperature dependent diffusion measurements of C60 in CS2 do not reveal a difference in the activation energy of solute and solvent. We could not detect that the diffusion coefficients of the solvent molecules are influenced by the presence of the fullerenes in the solutions under investigation.
Disquac application to SLE of binary mixtures containing long chain 1‐alkanols (1‐tetradecanol, 1‐hexadecanol, 1‐octadecanol, or 1‐eicosanol) and N‐alkanes (C8–C16)
Authors: González J. A. , Garc de la Fuente I. Ía , Cobos J. C. , Casanova C. , Domańska U.
Published: July 2012

Thirty‐four sets of data on solid‐liquid equilibria for the entitled mixtures are examined in terms of DISQUAC. On the basis of data for systems containing n‐octane, new first dispersive interchange coefficients are given for the hydroxyl/aliphatic contacts involved. They are constant from 1‐hexadecanol. The remainder interchange coefficients are kept the same as in our previous works. The relative standard deviations for the equilibrium temperatures are less than 0.025 for all the mixtures investigated. Results depend on the difference in size of the mixture compounds.
Prediction of surface tension of liquids
Authors: Rubio José E. F. , Baonza Valentín G. , Cáceres Mercedes , Núñez Javier
Published: July 2012

Most of useful estimation techniques for surface tension of liquids are based on empirical correlations and general methods with molecular basis are rare in the literature. In this paper we show how combining an expression derived from the hole theory of Fürth with an statistical‐mechanical based equation of state, an estimation of surface tension and its behavior with temperature is easily obtained.
Hydrogen absorption and thermodynamic properties of hydrogen in low rh content Pd‐Rh alloys
Authors: Sakamoto Y. , Haraguchi Y. , Ura M. , Chen F. L.
Published: July 2012

The hydrogen absorption characteristics of fully annealed Pd‐Rh alloys containing up to 10.0 at.% Rh have been investigated at temperatures between 273 K and 433 K and hydrogen pressures up to 1000 Torr by means of pressure‐composition isotherm measurements. For the p‐c isotherms of Pd‐7.5 at.% Rh alloy, in addition to the normal (α+β) two‐phase plateaus, “anomalous plateaus” are observed near the normal βmin phase boundaries. The formation of this anomalous plateau implies that in the fully annealed alloys some precursory phase separation exists, together with the metastable, homogeneous solid solution phase. The low pressure hydrogen solubilities decrease with an increase of Rh content and the main plateau pressures increase with the solute metal content. The hydrogen solubilities exhibit a maximum at about 7.5 at.% Rh at 1000 Torr. The derived relative partial molar thermodynamic quantities at infinite dilution, and also the plateau thermodynamic parameters are in agreement with the previously reported results. These thermodynamic quantities are not affected by the formation of the anomalous hydride phase, because the hydride does not form in the dilute phase region, and because the amount of hydrogen involved in the anomalous hydride phase is small compared to the main hydride phase.
The rotational spectrum of the benzonitrile‐argon van der Waals complex
Authors: Dahmen U. , Stahl W. , Dreizler H.
Published: July 2012

The microwave spectra of 14N‐ and 15N‐benzonitrile‐argon have been recorded using a pulsed molecular beam Fourier transform microwave spectrometer. In the case of 14N‐benzonitrile‐argon, the rotational constants were determined to be A = 1347.7899(12) MHz, B = 1006.02030(94) MHz, C = 719.81749(24) MHz. The quartic centrifugal distortion constants (van Eijck) are D'J = 3.9982(14) kHz, D'JK = −15.3062(79) kHz, D'K = 21.8510(92) kHz, d'J = 1.65065(83) kHz, R'6 = 0.03043(38) kHz, and the 14N‐nuclear quadrupole coupling constants are χaa = −0.4479(17) MHz, χbb‐χcc = −4.1255(17) MHz. For 15N‐benzonitrile‐argon the rotational constants were found to be A = 1335.09150(30) MHz, B = 989.86421(15) MHz, and C = 707.91548(07) MHz. The centrifugal distortion constants are of the same magnitude as for the 14N‐isotopomer. The argon atom is placed 3.545 Å above the center of the ring plane. In addition, the spectra of benzonitrile and six isotopic species have been reinvestigated; the derived constants and the resulting structure are of higher accuracy than in earlier work.
Laser photolysis of naphthoquinone diazide in cyclohexane – two‐laser chemistry
Authors: Bendig J. , Mitzner R.
Published: July 2012

The laser photochemistry of 1,2‐naphthoquinone‐diazide‐(2)‐5‐sulfonic acid phenylester in cyclohexane has been investigated. The photolysis experiments have been done using a KrF laser pulse (generation pulse) and a nitrogen laser pulse (transformation pulse) with various time delay from 40 ns up to 1 s. At a time delay between the two laser pulses in the μs‐region, the formation of indene and cyclohexyl‐indene derivatives has been observed, additional to the corresponding indenecarboxylic acid. The laserspecific formation of these compounds is the result of the electronic excitation of the intermediately formed ketene and its reaction by decarbonylation. The time delay for getting a high yield of the indene and the cyclohexyl‐indene derivatives correlates closely with the rise time and the life time of the ketene.
Characterisation of CN in the photodissociation of cyanogen azide at 193 nm
Authors: Baumgärtel S. , Gericke K.‐H. , Comes F. J.
Published: July 2012

The photodissociation dynamics of NCN3 has been investigated by observation of the CN(X2Σ) product molecule. The CN fragment is formed in vibrational states ν = 0,1,2 with a population ratio of P(ν = 0):P(ν = 1):P(ν = 2) = 0.42:0.33:0.25. The rotational state distribution is broad, a Boltzmann plot shows a nonlinear behavior. The rotational excitation carries 9% of the available energy. The CN recoil velocity distribution is also broad and indicates a significant internal excitation of the N3 product molecule. The spin is distributed statistically. The fragmentation does not proceed in the Franck‐Condon limit but strong forces act on the upper potential energy surface.
On the dependence of the photoluminescence decay on the externally applied potential at the junction n‐GaAs/1 M HCl
Authors: Krüger O. , Jung Ch.
Published: July 2012

The decay of the integral band‐to‐band photoluminescence (PL) at (100) orientated n‐doped GaAs (Te; n0 = 5×1017 … 1×1018cm3) in contact with aqueous 1 M HCl was investigated with the time‐correlated single photon counting technique. The PL‐decay was measured at various externally applied potentials, at constant and low density of injected carriers (pi≪n0), and at an excitation wavelength of λexc = 647.1 nm. The studies included electrodes modified by dipping in a solution of 5×10−3 M RuCl3 in 1 M HCl for 20 minutes. It was observed that the PL‐decay measured at low injection level shows a reproducible and characteristic dependence on the externally applied potential. Within the accuracy of our time‐correlated single photon counting equipment, the PL‐decay time remains nearly constant and short in the range of potential U = (−0.3 … −0.9) V(Ag/AgCl). For the nonmodified electrodes the PL‐decay time increases with increasing cathodic polarization in the range of potential U = (‐0.9 … −1.1) V(Ag/AgCl) up to a maximum at U ≈ −1.1 V(Ag/AgCl), which corresponds to the (Mott‐Schottky) flatband potential in the dark. At further cathodic polarization the cathodic current (due to the evolution of hydrogen) during the measurements becomes significant and it was observed that the PL‐decay time decreases. After a treatment with Ru3+, the behaviour in the range of potential on the cathodic side of U = −0.9 V(Ag/AgCl) is different. The experimental observations could be confirmed qualitatively by results of computer simulations based on the Two‐dimensional Semi‐Conductor Analysis Package (TOSCA). At potentials on the anodic side of the flatband potential (depletion range) the decay times are short as well as independent of the degree of the band bending, of the surface recombination velocity, and of the photocurrent, respectively. This observation will be interpreted qualitatively by including the diffusion of the minority carriers toward the (dark) depletion layer as a competitive process for the radiative recombination in the bulk. Near the flatband potential the decay time of PL increases within a potential range of ΔU ≈ 200 mV depending on the density of injected carriers as well as on the rates of the surface recombination and of the minority carrier transfer (photocurrent). Based on a qualitative explanation for this characteristic dependence of the PL‐decay time on the potential, the values of the surface recombination velocity and of the exchange photocurrent density are estimated to be S0<106 cm/s and jph,0<10−8 A/cm2, respectively, for nonmodified electrodes and S0≥106 cm/s and/or jph,0≥10−8 A/cm2, respectively, for electrodes treated with Ru3+ ions.
Temperature polarization in membrane distillation of water using a porous hydrophobic membrane
Authors: Dittscher U. , Woermann D. , Wiedner G.
Published: July 2012

The rate of water transport across porous membranes with a hydrophobic matrix (porosity ϵ ≈ 0.5; characteristic length of voids ξ ≈ 150 nm; thickness δ ≈ 30 μm) caused by a temperature difference between the bulk phases is studied. The voids of the membrane are filled with water vapour. The effective temperature difference (T′–T″) across the membrane is smaller than the temperature difference (T′–T″) between the bulk phases (“temperature polarization”) caused by heat conduction and by heat flow associated with the water transport. An experimental method is described and tested to determine the temperature polarization coefficient τ ( = (T′–T″)/(T′–T″) for a given experimental situation. The phenomenological transport coefficient of the membrane for water vapour has to be known from independent experiments. This method is a simple alternative to the method developed by Schofield et al. (J. Membrane Sci. 33, 299 (1987)). The dominating factor determining the temperature polarization coefficient is the value of the thickness of the two boundary layer of heat conduction at the interfaces of the membrane.
An investigation about the NH(X3Σ−) formation in the thermal decomposition of HN3
Authors: Röhrig Michael , Wagner Heinz Georg
Published: July 2012

The thermal decomposition of HN3 was investigated behind incident shock waves in the temperature range of 1400–1800 K at densities around 2.6·10−6 mol/cm3. The rate constant of HN3 decomposition was determined by the evaluation of NH(X3Σ−) concentration profiles to be k1 = (7±4)·1014 exp (‐(150±10) kJmol−1/RT) cm3/mol s. The pyrolysis of hydrazoic acid leads almost exclusively to NH in its electronic ground state and can therefore be used as a NH(X3Σ−) source in the temperature range of 1000–1800 K.
Spectra and temperatures of diffusion flames at high pressures to 1000 bar
Authors: Pohsner G. M. , Franck E. U.
Published: July 2012

Diffusion flames have been produced by injection of oxygen into homogeneous dense mixtures of methane or hydrogen with supercritical water or argon. The mixture temperatures were around 500°C, pressures were varied between 50 and 1000 bar. The fuel concentrations were 30 mole percent or lower. Flames appeared spontaneously. Apparatus and procedure are described. Diffusion flame photographs to 1000 bar are shown. Emission spectra from 275 to 600 nm were recorded with a grating spectrometer and 1024 channel diode array. Emission in the visible is not of black body character and does not permit pyrometric temperature measurement. Flame temperature determination was based on the intense rotational emission of OH‐radicals in the near UV, produced by vibrational 0–0 and 1–0 transitions of the electronic A2Σ–X2∏ transition. The 0–0 band is near 306 nm. A fit program to determine rotational temperatures is developed which includes the influence of pressure broadening. The temperatures obtained for CH4 and H2 in supercritical water increase with pressure and reach 4000 to 4500 K at 1000 bar. Rotational temperatures obtained for dense argon environment are lower: 3000–3200 K. Adiabatic temperatures and calculated values for one‐dimensional diffusion flames are given for comparison.
On the potential role of DNA in an RNA world: Pattern generation and information accumulation in replicator systems
Authors: Hogeweg P.
Published: July 2012

Apparently at some stage in early evolution DNA evolved to complement RNA for information storage. In this paper we investigate under which circumstances the amount of accessible information is enhanced by using long‐lived molecules for information storage.

We show that pattern formation is essential for the exploitation of information stored in long‐lived molecules.
The role of feedback circuits: Positive feedback circuits are a necessary condition for positive real eigenvalues of the Jacobian matrix
Authors: Thomas R.
Published: July 2012

This talk deals with the biological roles of feedback loops and their combinations. It has progressively become clear that a negative loop is a necessary (not sufficient) condition for a stable periodic behaviour and that a positive loop is a necessary (not sufficient) condition for multistationarity. Of these old conjectures (e.g. Stud. phys. theor. Chem. 28, 307 (1983)), the second has now two formal demonstrations by others (Plahte et al., Snoussi). Here, we remark that this statement can be generalised as follows. The presence of a positive loop (in the Jacobian matrix of the system) is a necessary condition for having at least one real positive root in the characteristic equation (this can be shown to directly derive from the Descartes rule) and at least one real positive root in turn is a necessary condition for multistationarity.
Enzymatic RNA synthesis in self‐reproducing vesicles: An approach to the construction of a minimal synthetic cell
Authors: Luisi Pier Luigi , Walde Peter , Oberholzer Thomas
Published: July 2012

Our approach towards “core‐and‐shell self‐reproduction” is reviewed here. With this term, we indicate a process by which the shell‐reproduction of a spherically bounded system (micelles or vesicles) proceeds simultaneously with the replication of nucleic acid which is hosted inside the micelles or vesicles. The realization of such a process is seen as a step towards the construction of a synthetic cell model. Two chemical systems are examined here, one based on the polynucleotide phosphorylase‐catalyzed synthesis of poly(A) starting from ADP; and the other based on the enzyme Qβ replicase, which is able to catalyze the synthesis of a RNA template. In both cases, production of RNA macromolecules proceeds simultaneously with self‐reproduction of the oleic acid/oleate vesicles. One still open question is the determination of the redistribution of the guest macromolecular components during the reproduction of the shell. Within these limits, it is argued that this work offers a system which goes beyond the two approaches to self‐replication presented until now in the literature, namely the template self‐reproduction of linear sequences of oligonucleotides and the autopoietic shell reproduction of micelles and vesicles.
Self‐organization in living cells
Authors: Hess B. , Mikhailov A.
Published: July 2012

Theoretical estimates of characteristic mixing and traffic times of enzymic reactions are derived. They are used to analyze the operation of molecular networks formed by enzymic reactions inside living cells. Analogies between molecular chemical networks and neural nets are discussed.
Coupling between ionic and electronic fluxes in mixed ionic/electronic conductors: Experiments on Co1‐δO
Authors: Janek J.
Published: July 2012

In investigations of the isothermal transport properties of mixed conductors the dynamical coupling between ionic and electronic partial fluxes is usually neglected. Within the formalism of (linear) irreversible thermodynamics this assumption is expressed by a vanishing cross coefficient L12 in the matrix of the phenomenological transport coefficients. By analysing the phenomenological flux equations for cation vacancies and electron holes, experiments for the determination of the cross coefficient are defined. Experimental results for the coupling effect in Co1‐δO are presented, which have been obtained from three independent techniques. The results are discussed in the light of previous theoretical considerations. It is shown that a strong coupling between cation vacancies and electron holes exists in the case of Co1‐δO. To account for this coupling, an effective charge number of ions has to be introduced for use in the formulation of ionic fluxes.
Stationary state and dynamics of birefringence and nonlinear optical properties induced by electric field poling in polymeric films
Authors: Sekkat Z. , Knoll W.
Published: July 2012

We present a theoretical study concerning the effect of the electric field poling process on the molecular angular distribution of polar nonlinear‐optical molecules in a polymeric environment. This is required for investigating the contribution of the molecular order to the anisotropy and nonlinear‐optical processes (second‐harmonic generation (SHG), electro‐optic Pockels (EOPE) and Kerr (EOKE) effects). We demonstrate mathematically that the order parameters at thermodynamical equilibrium are defined exactly by the spherical modified Bessel functions (An(μE/kT) = in(μE/kT)/io(μE/kT)). They can be related to Langevin functions but with complicated relations for high orders of n. Their evolution with μE/kT confirms that the second order nonlinear‐optical processes (SHG and EOPE) are more sensitive to the strength of the poling field than are the linear (birefringence) and third‐order nonlinear‐optical effects (EOKE). We show that it is possible to measure the molecular anisotropy of nonlinear‐optical molecules by quadratic electro‐optic experiments. The transients of the poling are studied with the rotational diffusion equation, characterized by a rotational diffusion constant D. This is solved using important recurrence relations of Legendre polynomials. An almost exact analytical solution is found for the physical and practical case where μE/kT is close to 1, and the nonvanishing order parameters are almost equal to the rigourous expressions given by the spherical modified Bessel functions. It is shown that the onset of birefringence and nonlinear‐optical processes (SHG, EOPE and EOKE) involves two time constants τ1,2 = [2D(2 ± √1–(μE/kT)2/5)]−1 which depend on D and μE/kT. After the removal of the poling field, the relaxation of the linear and nonlinear‐optical properties is also discussed.
The relationship between the Raoultian and Henrian activity of a solute
Authors: Näfe H.
Published: July 2012

A relationship between the Raoultian and Henrian activity of any component in any given mixture is derived which proves to be a real alternative to the relationships known so far. The derivation reveals that the Henrian saturation activity of the respective component represents the link between the two reference systems which has to date been overlooked in the literature.
Observation of mixing‐induced twist grain boundary phases in liquid crystals
Authors: Kuczynski W. , Stegemeyer H.
Published: July 2012

Two twist grain boundary phases (TGB) have been observed in binary liquid crystalline mixtures exhibiting a nematic – smectic A – smectic C triple point. The observed TGB phases are very stable – for some concentrations the temperature ranges exceeded 20 K for each of them. Optical properties and textures have been investigated. Phase transitions between the phases under discussion have been determined by measurements of the dielectric permittivity and the optical rotation. A distinct influence of surface interactions on the stability of the twisted smectic A phase was observed.
Sublimation of pure C60fullerene and of C60adsorbed on MgO or graphite powders
Authors: Richter H. , Dereux A. , Gilles J. M. , Guillaume C. , Thiry P. A. , Lucas A. A. , Rozenberg R. , Spǒte A. , De Hoffmann E. , Girard Ch.
Published: July 2012

The sublimation of pure C60and the thermal desorption of C60fullerene deposited on MgO and graphite samples have been analyzed by mass spectrometry. The experiments have been performed in the Desorption Electron Impact mode (DEI) using a heating current between 40 and 1200 mA. The desorption from a substrate as well as the C60sublimation is a first order process with an activation energy of about 200 kJ mole−1. This value confirms the computational results obtained for van der Waals interaction. The peak broadening in the case of C60/graphite can be explained by a strong interaction between C60and the graphite substrate which is also predicted theoretically.
Spectroscopy: Past and present
Authors: Schlag E. W.
Published: July 2012

We present a review of historical methods in spectroscopy culminating in modern techniques made available by the advent of laser technology. Spectroscopy is undergoing a worldwide renaissance as a result of these methods which point to entire new fields of application. Special examples are given, such as mass spectrometry, very high resolution methods, photoelectron spectroscopy and ZEKE spectroscopy as well as modern ultrafast techniques.
From molecular processes to global mechanisms of chemical transformations
Authors: Troe J.
Published: July 2012

Many of the founders of modern gas phase reaction kinetics were members of the Deutsche Bunsengesellschaft für Physikalische Chemie (the former Deutsche Elektrochemische Gesellschaft). The evolution of this field from its beginnings around 1894 towards today, from qualitative understanding to quantitative modelling is reviewed. The connection between global mechanisms and elementary reaction steps is exemplified by sensitivity tests. Elementary reaction rates then are related to potential energy surfaces showing intermediate energy maxima, i.e. single activated complexes, or intermediate energy minima, i.e. involving several activated complexes.
Elektrochemie: Von der Thermodynamik zur atomaren Struktur
Authors: Kolb D. M.
Published: July 2012

The last decades have witnessed a remarkable change in electrochemistry: from a macroscopic, thermodynamicsoriented approach towards electrochemical problems to a microscopic, atomistic one. The latter was frequently inspired by models derived for the solid‐vacuum interface. The desire and the necessity to understand electrochemical processes on an atomic or molecular level called for new experimental and theoretical routes. Significant advances in the understanding of electrode reactions resulted from the availability of new techniques in electrochemistry, e.g., by adoption of structure‐sensitive surface‐physics techniques to electrochemical needs. Similarly important was the use of single‐crystal electrodes with well‐characterized surfaces. It was their wide‐spread use which brought to light the importance of the surface structure in electrochemical kinetics. In the following we shall demonstrate with a few selected examples how much information about the microscopic structure of electrode surfaces is nowadays available. In this respect, scanning tunneling microscopy has had a major impact. Finally, future trends in fundamental electrochemical research are discussed.
Hundred years of colloid science fascinating phenomena in surfactant solutions
Authors: Hoffmann H.
Published: July 2012

The lecture begins by reviewing some facts that were already known in colloid science of hundred years ago. The importance of colloid science for the development of human civilization and modern technology is then outlined. The main part of the lecture deals with surfactant science, a subdivision of colloid science:

Amphiphilic molecules can assemble in aqueous solution into a variety of micellar structures such as globules, rods, disks and vesicles. For a given system the micellar structures are determined by the packing parameter of the surfactant which controls the spontaneous curvature of a micellar interface. The spontaneous curvature of micelles can be varied continuously by the addition of cosurfactant to the micellar solution. With increasing mole fraction Xc of the cosurfactant, the system develops then from micelles with interfaces that are strongly curved around the micellar core over planar interfaces towards interfaces that are curved away from the micellar core. Results are presented for the ternary systems of alkyldimethylaminoxides, n‐alcohols and water. As a consequence of the change of the spontaneous curvatures with Xc the systems undergo several macroscopic phase transitions in dilute solutions. In total eleven different single and multiphase situations are observed when one passes from the dilute surfactant to the dilute cosurfactant solution. The single phase regions are the micellar L1‐phase, two different lamellar liquid crystalline Lα‐phases (Lα1 and Lαh) and the isotropic L3 or sponge phase. The microstructures of the various phases are identified by electronmicrographs which were obtained with the freeze fracture method. The macroscopic properties of the phases are discussed on the basis of their microstructures. The influence of charges by ionic surfactants on the structures and properties of the mesophase is determined. It is found that the Lαh and the L3‐phase are transformed into a phase with multilamellar vesicles. This phase has a Theological yield stress value and can be used as a particle suspending fluid. The influence of excess salt on the microstructures and the properties of the charged phases is determined.

Some of the observed phases show bright colours when illuminated with white light. Some of the phases show colour effects when viewed through crossed polarizers.
Computer simulation as a tool to analyze neutron scattering experiments: Water at supercritical temperatures
Authors: Löffler G. , Schreiber H. , Steinhauser O.
Published: July 2012

We present results of molecular dynamics simulations of water at supercritical conditions that correspond exactly to those of an experimental study performed by Postorino et al. (P. Postorino, R.H. Tromp, M.‐A. Ricci, A.K. Soper, and G.W. Neilson, Nature 366, 668 (1993)). The discrepancy between simulation and experiment raised by these authors is partly removed simply by considering corresponding thermodynamic states. The careful analysis of the contributions of neutron scattering experiments on the atomic radial distribution functions of water gives strong evidence that the neutron‐scattering experiment on non‐deuterated water plays a key role in determining the essential features of gOH(r) and gOO(r) and is a potential source of artifacts.
Infrared and raman study of ν4 and ν5 motions of light and deuterated nitromethane evidence of conformational equilibria
Authors: Cataliotti R. S. , Distefano M. R. , Mariani L. , Morresi A. , Paliani G. , Santini S. , Giorgini M. G.
Published: July 2012

Infrared and Raman spectroscopy has been used to study totally symmetric ν4 and ν5 motions of CH3NO2 and CD3NO2 isotopomers, in order to ascertain the nature of the low‐frequency features appearing in these bands. A study, under high‐resolution conditions, of the gaseous phase infrared spectra and of the temperature effects, carried out on both liquid and gaseous molecules, has allowed us to proove that these features are connected to the effects of conformational population and not to hot band transitions, as it has been previously reported.
The Nucleation of Colloidal Copper in the Presence of Poly(ethyleneimine)
Authors: Sosebee T. , Giersig M. , Holzwarth A. , Mulvaney P.
Published: July 2012

Copper colloids have been prepared by y‐radiolysis of cupric ions in the presence of poly(ethyleneimine). The reduction takes place in two, distinct steps. Copper (II) is reduced quantitatively to copper (I), and then nucleation of the colloid occurs after an induction period. The nucleation of colloidal copper is catalysed by the presence of less noble Pb(II) or T1(I) ions, which is explained by the generation of Pb and Tl nuclei in the solution, and their subsequent reoxidization by Cu(I). The formation of copper colloids is also catalysed by the presence of colloidal silver or silver ions, and radiolysis results in the formation of copper coated silver colloids. The optical shifts observed during the deposition of copper on silver cannot be explained by Mie theory. The differences are suggested to be due to weaker interband transitions in the copper monolayers than in the bulk
Viscosity Effects on the Intramolecular Fluorescence Quenching in Dipeptide Model Compounds
Authors: Sakurai Tadamitsu , Miyoshi Kenichiro , Obitsu Mitsuhiro , Inoue Hiroyasu
Published: July 2012

The finding that the increased solvent viscosity decreases the rate for intramolecular fluorescence quenching in the title compounds [N(n)D], giving a singlet‐exciplex intermediate, but increases the rate for the reverse process, regenerating the locally excited singlet‐state N(n)D, is explained in terms of the viscosity‐dependent free‐energy change for this fluorescence quenching process (ΔGet). A linear correlation between the ΔGet and the logarithm of solvent viscosity is found to provide a good criterion for a singlet‐exciplex mechanism in polar solvents.
A simplified DEMS Set Up for Electrocatalytic Studies of porous PtRu Alloys
Authors: Ianniello Remo , Schmidt Volkmar M.
Published: July 2012

A simplified experimental apparatus for Differential Electrochemical Mass Spectrometry (DEMS) was constructed having only one turbomolecular pump and a modified gas inlet system. The setup allows the determination of the activity of porous PtRu electrodes for the electro‐oxidation of small organic molecules. Various PtRu alloys with defined composition can be electrodeposited onto porous gold substrates. First results on the electrooxidation of methanol in acid solution were presented.
On the Calculation of Point Defect Equilibria
Authors: Spinolo G. , Anselmi‐Tamburini U.
Published: July 2012

A method is outlined for solving the equations describing the quasichemical equilibria of point defects, with particular reference to binary oxides. The method gives exact solutions for all defect concentrations and the oxygen activity as a function of n = [e′]. In comparison to the traditional approach, the feasibility of the method does not depend on the number of differently charged defects of the same kind. Possible extensions of the approach are briefly discussed.
The Inverted Region of Electron Transfer in Intramolecular Fluorescence Quenching of Quinolinium Betaines
Authors: Käb G. , Engel TH. , Lanig H. , Schneider F. W.
Published: July 2012

Fluorescence quenching through intramolecular electron transfer (ET) was studied in N‐(ω‐sulfonatoalkyl)‐ and N‐(ω‐carboxyalkyl)‐quinolinium betaines by stationary and time‐resolved fluorescence spectroscopy in the solvents water and acetonitrile. These substances are zwitterionic in the ground and local excited state of the quinolinium chromophore. In the sulfonato compounds fluorescence quenching through ET does not occur in water, whereas quenching is efficient in acetonitrile. A surprising opposite behaviour is observed for the carboxylato compounds: quenching is efficient in water whereas it is inefficient in acetonitrile. Semiempirical calculations were used to derive the parameters needed for the description of the quenching process by non‐adiabatic Bixon‐Efrima‐Jortner‐theory. These parameters include the solvent (λs) and the intrinsic (λv) contributions to the total reorganisation energy λ and the approximate free energy of reaction ΔG°. The vibrational motion of an aromatic C‐H bond influenced by the interaction with the negatively charged donor was taken as the major intramolecular accepting mode. ET fluorescence quenching in the present compounds and solvents may be interpreted in terms of the “normal” and the “inverted region” of Marcus theory.
A Scanning Michelson Interferometer for the Measurement of the Concentration and Temperature Derivative of the Refractive Index of Liquids
Authors: Becker A. , Köhler W. , Müller B.
Published: July 2012

A compact scanning Michelson interferometer for the measurement of both the concentration and temperature derivative of the refractive index of liquids, liquid mixtures, and solutions has been developed. Scanning of one of the mirrors allows the extraction of the phase information and makes the instrument insensitive to intensity drifts of the light source. The refractive index noise level of the empty instrument is of the order of 10−8 for a 10 mm sample cell, and for continuously varying refractive indices there is no upper limit of the linear detection range. Accuracies of the order of 0.5% can be achieved both for (n/c)p,T and (n/T)p,c.
Phase Diagram and Dynamic Properties of the Ternary System Water – Sodium Dodecylsulfate – Aerosol OT
Authors: Muzzalupo Rita , Ranieri Giuseppe A. , Terenzi Mario , Mesa Camillo La
Published: July 2012

The phase diagram of the system composed by Water, Sodium Dodecylsulfate and Aerosol OT, at 25°C, has been investigated. Some physico‐chemical properties of the system were determined by optical microscopy, electrical conductance and NMR investigation on 2H and 23Na nuclei. Information on binding and counterion dynamics, as well as on the mesophases structure, were inferred by comparing quadrupole splittings and electrical conductance findings.
On the Algebraic Evaluation of the Ternary Molar Heat of Mixing HE from Calorimetric Investigations
Authors: Tomiska Josef , Wang Hai
Published: July 2012

The experimental effort of calorimetric investigations on ternary alloy systems is very large and evaluation of the measured data is very time‐consuming. A considerable reduction both of the time spent on evaluation and of the experimental work can be expected by applying the new overall best‐fit technique developed in this work. The suggested evaluation technique is based on the ternary “Thermodynamic Adapted Power” (TAP)‐series, requires computer assistance, but it makes possible to determine ternary molar heat of mixing HE by means of a minimum of experimental investigations: If there exist accurate HE‐data of the three binary boundary systems, only a small number (about 5 to 10) of ternary HE‐values must be determined. The application of the proposed evaluation technique is illustrated with data for liquid Fe–Co–Ti, Fe–Ni–Ti, Fe–Ni–Zr, and Cu–Sn–Ni ternary alloys. The advantages of the proposed technique are discussed in detail.