bluuebunny/crossref_metadata_2025 huggingface dataset:
The Kinetics and Mechanism of Reactions Between the Nitroprusside Ion and Secondary Amines
Authors: Casado J. , Mosquera M. , Rodr ÍGuez Prieto M. F. , Vázquez Tato J.
Published: July 2012

The kinetics of the reactions of the nitroprusside ion — pentacyanonitrosylferrate(II) — with various secondary amines have been studied in basic media. Two parallel reaction pathways are involved: (i) the reaction of the nitroprusside ion with hydroxyl ions to form Fe(CN)5NO4+2, in which NO−2 is then replaced by the amine; and (ii) the reaction of the nitroprusside ion with two molecules of amine to form the corresponding nitrosamine and the complex Fe(CN)5NHR3‐2. The corresponding rate equations have been obtained and explained by proposed reaction mechanisms. We propose a concerted mechanism for reaction (ii) in which the amine binds the nitrosyl group at the same time as the amine proton is removed by a base catalyst. The resulting nitrosamine complex subsequently undergoes substitution by the amine in a faster step.
Fluid Phase Equilibria in Quasi‐Binary Systems of Ethylene + n‐Eicosane + n‐Tetracontane
Authors: De Loos Th. W. , Foot W. , Perbal R. , Lichtenthaler R. N.
Published: July 2012

Vapour‐liquid equilibria in quasi‐binary systems of ethylene with mixtures of n‐eisosane and n‐tetracontane of fixed molar ratios of n‐eisosane to n‐tetracontane of 0.748:0.252, 0.700:0.300, 0.510:0.490 and 0.247:0.753 have been measured in the temperature range 325 to 450 K and at pressures up to 40 MPa. The results show a distinct influence of the mean molecular weight of the n‐alkane mixtures on these equilibria especially in the critical region. The phase behaviour of the quasi‐binary systems investigated is compared with the phase behaviour of binary systems of ethylene and n‐alkanes. — It is shown that except for the high‐pressure region the fluid phase equilibria of the quasi‐binary systems can be predicted reasonably well with the Peng‐Robinson equation of state using only pure component and binary data to determine the adjustable parameters.
Temperature Effect on the Positronium Formation in Organic Solutions
Authors: Alfassi Zeev B. , Ache Hans J.
Published: July 2012

Studies of the temperature dependence of the rate constants for inhibition of o‐Ps formation in organic solvents show either zero or negative activation energies. This is additional evidence for the hypothesis that the experimentally observed inhibition rate constant k is the ratio of rate constants of two competing reactions, one being the reaction of the precursor of the thermalized o‐Ps with the solute (rate constant k), followed by annihilation and the second being the thermalization of this precursor (rate constant k2).
Dielectric Relaxation of 2‐Pyrrolidinone and Some N‐Substituted, Related Compounds in the Liquid State
Authors: Dachwitz E. , Stockhausen M.
Published: July 2012

The complex permittivity of the following neat liquids has been measured in the frequency range from 20 MHz to 36 GHz at 20°C: (1) 2‐pyrrolidinone, (2) N‐methyl‐, (3) N‐vinyl‐, (4) N‐ethyl‐, (5) N‐cyclohexyl‐, (6) N‐benzyl‐2‐pyrrolidinone, (7) N‐methyl‐2‐piperidone and (8) N‐methyl‐caprolactam. The results can be described by one or two superimposed Debye‐type components. One component is due to rotational tumbling of single molecules. The additional component is ascribed to associates, possibly dimers, in the case of (1), but in the other cases, as far as occuring to a significant extent, that is with (4) to (8), to intramolecular motions.
Additivity Rule of the Partial Molal Volume. 3. Anomaly of Cycloalkane Molecules and Volume Change for the Ring Formation Reaction
Authors: Yoshimura Y. , Nakahara M.
Published: July 2012

The semimicroscopic theory of the partial molal volume which takes account of the local molecular packing efficiency through the surface energy has been applied to the cycloalkane by using a simple molecular model to evaluate the core dimensions. The anomalous deviation of the partial molal volume of the cycloalkane from the additivity rule is successfully interpreted; the anomaly arises simply from the geometrical factor that the core dimensions of the cycloalkane are larger than those of the corresponding linear alkane. The semimicroscopic approach provides a new framework for the interpretation of the volume change accompanying the chemical reaction in solution; this is demonstrated in the case of the cycloaddition reaction. The present approach justifies the separation of the overall reaction volume into the components in the additive manner.
Experimental and Theoretical Investigation of the Azide Anion (N−3) in the Gas Phase
Authors: Illenberger Eugen , Comita Paul B. , Brauman John I. , Fenzlaff Heinz‐Peter , Heni Martin , Heinrich Nikolaus , Koch Wolfram , Frenking Gernot
Published: July 2012

We report the formation of the azide anion (N−3) in the gas phase by dissociative electron attachment to benzyl azide in a beam experiment. The electron photodetachment cross section of N−3, generated analogously in an ion cyclotron resonance (ICR) spectrometer has been measured. A threshold of 2.76 ± 0.04 eV was obtained corresponding to the vertical detachment energy in N−3. Ab initio calculations on N−3 and N3 predict similar geometries for both compounds, indicating that the photodetachment threshold can be equated with the electron affinity of the azide radical.
Laser Photolysis and Pulse Radiolysis Investigations on the Triplet Energy Transfer in Aromatic Donor‐Acceptor Systems
Authors: Brede O. , Mehnert R. , Naumann W. , Teply J.
Published: July 2012

To study the relation between the rate and the free energy difference of the TT transfer from some aromatic donors (D) to various preferably aromatic acceptors (A) in benzene solution we combined laser photolysis and pulse radiolysis experiments. Transfer rate constants k1, were determined for DA pairs with differences of the (S0T1) energies ΔE = E(S0T1)D)A between −0.2 and 1.4 eV. A k1 versus ΔE plot shows reaction‐controlled values for ΔE ≤ 0.2 eV. At higher ΔE the diffusion‐controlled limit is reached. By analogy with electron and singlet energy transfer the k1 vs. ΔE relationship was interpreted as arising from the Franck‐Condon effect in the excess energy acceptance by the intramolecular modes.
Another Intermediate in the Photochemistry and Radiation Chemistry of Alkaline Aqueous Solutions
Authors: Telser Th. , Schindewolf U.
Published: July 2012

By UV flash photolytic and pulse radiolytic experiments of aqueous alkaline solutions we confirm older experiments of Walker et al. and Hart et al., showing that the decay of hydrated electrons gives rise to another intermediate X which by light absorption revives hydrated electrons again. X is formed by a reaction of 1. order with respect to hydrated electrons, the rate of its formation increases with pH, and it decays by a second order process with a rate constant not exceeding 5 · 109 M−1 sec−1, probably leading to hydrogen (e− → X; 2X → H2). X has maximum light absorption around 270nm with an extinction coefficient of about 5000 M−1 cm−1. — We will not speculate about the nature of X.
Deuteron NMR Study of Molecular Mobility in a Polymer Model Membrane
Authors: Ebelhäuser R. , Spiess H. W.
Published: July 2012

The molecular mobility of a polymer model membrane is studied by 2H NMR. The lipid analogue consists of a quaternary ammonium ion, to which a methacryloylic moiety is attached via a spacer to the hydrophilic head group. A methylene group of the spacer, the methyl‐head group and methylene groups in the 1‐, 2‐, and 7‐position of the lipid chains are selectively deuterated. Temperature dependent 2H NMR spectra are reported for both, the monomer and the polymer membrane below and above the main phase transition. The data are quantitatively analyzed in terms of a simple motional model, in which the complex molecular dynamics is approximated by a six‐site jump model describing rotations about the long axis of the molecule and conformational changes. The increasing mobility with increasing temperature is only in part due to an increase of the jump rate between different sites. It also reflects the increase in the number of conformations accessible. As a quantitative measure of the mobility at a given site, a mean jump frequency is extracted from the data. For the monomer Ω˜ and its temperature dependence in the liquid crystalline phase is almost independent of the site being studied. In the polymer, however, major differences are observed, Ω˜ for the head group and the 7‐position of the lipid chain differing by two orders of magnitude. The mobility of the spacer is even lower. This 2H NMR study thus shows that although the polymerization largely hinders the head group mobility, the chain flexibility most important for membrane applications is retained.
Ethylbenzene Pyrolysis: Benzyl CC or CH Bond Homolysis
Authors: Robaugh David A. , Tsang Wing , Fahr Askar , Stein Stephen E.
Published: July 2012

The thermal unimolecular decomposition of ethylbenzene has been studied by both the very‐low‐pressure pyrolysis and heated single‐pulse shock tube methods in an attempt to resolve a recent controversy as to whether the initial dissociation channel is benzyl C ‐ C,

or benzyl C‐H homolysis,

Observed decomposition products and mass balance studies lead to the conclusion that up tc 1288K the predominant decomposition channel is benzyl C‐C homolysis. Additional support of this conclusion is provided by a study of isopropylbenzene decomposition by these same methods. Arguments are given which strongly suggest that benzyl C‐H homolysis cannot be the major reaction channel even at temperatures as high as 1600K.
The Synchronous 1,4‐Addition of SiH2(1A1) to s‐cis‐buta‐1,3‐diene. A CI and CASSCF Study
Authors: Maier Elisabeth , Olbrich Gottfried
Published: July 2012

A minimum energy path for the synchronous 1,4‐addition reaction of SiH2(1A1) with s‐cis‐buta‐l,3‐diene to 1‐silacyclopent‐3‐ene was determined by ab initio SCF and CI calculations. To analyse the changes of electronic structure along the reaction path CASSCF calculations and a population analysis were performed. From these and the geometrical variations it is concluded that the reaction is initiated by an electrophilic step involving the HOMO of butadiene and the empty p orbital of SiH2. Closed shell repulsions play a decisive role for the orientation of the SiH2 relative to the butadiene molecule. An activation energy of 17 kJ/mol is estimated and the exothermicity for the formation of the silacyclopentene is evaluated to be 283.82 kJ/mol. It follows from the CASSCF calculations that the activation barrier of the reaction is due to an avoided crossing between the ground and first excited singlet state of the composite system.
Critical Fluctuations on Solid Surfaces
Authors: Willis Roy F.
Published: July 2012

Phase transitions and phase diagrams of two‐dimensional systems are quite distinct from three‐dimensional behaviour. Topological defects such as steps, domains and domain‐wall dislocations play a key role. This paper discusses the nature and scale of the atomic fluctuations at phase boundaries for order‐to‐disorder structural phase transformations on solid surfaces. The question of the rich variety of configurational patterns of “precursor” short‐range order is discussed with reference to reconstructed surfaces of Au(l10)(2 x 1) and W(100)( √2x √2)R45° systems. These systems belong to different two‐dimensional universality classes on account of their different symmetries and serve to illustrate critical precursor fluctuation phenomena of current interest.
2d Krypton, a Model System for a Commensurate‐Incommensurate Transition
Authors: Marx R. , Hoja R.
Published: July 2012

We studied the commensurate‐incommensurate phase transition of krypton physisorbed on graphite foam by adsorption volumetry. The transition can be described by a power law with exponent β of the misfit m versus the difference of the chemical potentials μ—μc of the incommensurate and the commensurate phase, respectively. In the investigated temperature range β is equal to 1/3 and within an uncertainty of ± Δβ = 0.014 independent of temperature.
Photoemission from Ordered Physisorbed Molecular Phases N2/Graphite, N2 and CO/Ag(111)
Authors: Schmeißer D. , Lyo I. W. , Greuter F. , Plummer E. W. , Freund H.‐J. , Seel M.
Published: July 2012

Using angle resolved ultraviolet photoelectron spectroscopy (ARUPS) the two dimensional energy dispersions of ordered physisorbed monolayers of N2 and CO/Ag(111) has been measured. For N2/graphite the ordered herringbone structure can be identified by correlating the ARUPS data to recent LEED studies. For all systems investigated we observe a k dependent splitting of the 5 σ (3 σg) level which is a consequence of the intermolecular interaction of two molecules in the unit cell. The splitting is largest in the center of the Brillouin zone of the overlayer and disappears towards its zone boundary. The observed dispersion can be understood by a simple tightbinding calculation and is in good agreement with an ab initio bandstructure calculation.
Ordering Kinetics for O on W(110)
Authors: Tringides M. , Wu P. K. , Moritz W. , Lagally M. G.
Published: July 2012

An analysis of peak‐intensity‐vs‐time data for LEED from W(110)p(2 × 1)‐O at saturation coverage is made to emphasize early times. From this analysis an exponent x ∼ 0.33 for the growth of the average size of ordered domains is extracted. Experimental evidence for a ground‐state degeneracy p = 8 in this system is presented, supporting the existence of slow domain growth that is suggested by the growth exponent. The relationship to recent theoretical results is discussed.
Reactive Transformation of Surface Structure
Authors: Ertl G.
Published: July 2012

Kinetic and energetic aspects of adsorbate‐induced first‐order phase transitions of the structure of single crystal surfaces are illustrated by the examples H/Ni(110) and CO/Pt(100). During the catalytic oxidation of CO on Pt(100) even periodic changes and spatial pattern formation of the surface structure may occur which effects are coupled to temporal oscillations of the reaction rate.
Statistical Model for the Hydrogen‐Induced Reconstruction of the Ni(110) Surface
Authors: Rys Franz S. , Müser Horst E.
Published: July 2012

A recently proposed statistical model for the two‐dimensional reconstruction transition of H/Ni(110) is investigated using a suitable fast Monte Carlo formalism. The phase diagram is presented for some range of the parameter values. Various low temperature (LT) non‐reconstructed, and homogeneous and pairing‐row reconstructed phases are found. Near the phase boundaries the approach to equilibrium is strongly slowed down due to topological constraints. Similar features are reported from experimental studies on the clean Pd(110) surface.
Reversible and Irreversible Phase Transitions in the Surface Segregation of Sn, Sb, and Al on Iron Single Crystals
Authors: Rüsenberg M. , Viefhaus H.
Published: July 2012

Low index ((100), (110), (111)) single crystal surfaces of binary alloys Fe‐X (X = Sn, Sb, Al) with different bulk concentrations were studied by AES, LEED, and XPS. The surface segregation of the alloying elements was investigated in the temperature range 400…700°C.—Irreversible order‐order or order‐disorder transitions in dependence on the surface coverage during the segregation process were detected. Reversible order‐disorder transitions in dependence on bulk concentration and temperature were observed for (110) oriented surfaces.
Phase Transitions in Chemisorbed Hydrogen Layers
Authors: Christmann K.
Published: July 2012

A brief survey is given about hydrogen‐transition metal systems which exhibit adsorbed hydrogen phases with long‐range order that can undergo order‐order and order‐disorder transitions depending upon the surface coverage θHand the temperature, respectively. A distinction has to be made between genuine lattice gas phases in which the H atoms simply occupy lattice sites with identical local symmetry without affecting the positions of the underlying metal atoms and those chemisorbed H phases which involve a distortion of the surface geometry of the substrate leading to the well‐known surface reconstruction. The systems H/Ni(111), H/Pd(111), H/Pd(100) and H/Fe(110) belong to the first category whereas H/Ni(110) and H/Pd(110) represent examples of the latter category, i.e., that involves surface reconstructed phases. As far as they have been determined the phase diagrams of the ordered H phases will be described and interpreted in terms of the mutual H‐H interactions.
Die zweiten Virialkoeffizienten von Helium‐Gasmischungen im Bereich unterhalb Zimmertemperatur
Authors: Elias E. , Hoang N. , Sommer J. , Schramm B.
Published: July 2012

Measurements of second interaction virial coefficients of mixtures He/O2, CO, NO, CH4, CF4, CO2, N2O, SF6, and NH3are presented. Temperatures range from 300 K to temperatures as low as the boiling temperature of the molecular components. New experimental data of second virial coefficients for most of the pure components are presented also and are critically compared with literature data. Recently published anisotropic intermolecular potential energy surfaces and several combining rules were tested with the new data.
Kinetic Isotope Effects for Hydrogen Abstraction from Various Saturated Hydrocarbons by Deuterium Atoms in the Gas Phase
Authors: Fujisaki Noboru , Gäumann Tino , Ruf Amanz
Published: July 2012

Using deuterium atoms produced in the radiolysis of heavy water vapor, the kinetic isotope effects kH/kD were determined by the isotope competitive method for the abstraction reaction D* + RH(R′D)→HD(D2) + R′(R′), where RH is an alkane and R′D is the corresponding perdeuterated alkane. The alkanes RH investigated include isobutane, 2,3,4‐trimethylpentane, neopentane, cyclopentane, cyclohexane, cycloheptane, and n‐heptane. The results were represented in terms of the Arrhenius‐type expression kH/kD = AH/ADexp((ED‐EH) (kJ mol−1)/RT), over the temperature range 363–473 K. The pre‐exponential factor ratios AH/AD vary from 0.36 for neopentane to 0.70 for 2,3,4‐trimethylpentane, the ED—EH values from 6.4 for 2,3,4‐trimethylpentane to 10.4 kJ mol−1 for neopentane. The variation in the ED—EH values was correlated with the bond strength of the C‐H bond being broken. The deuterium and hydrogen atoms, as the attacking species, are found to show essentially the same magnitude of the kinetic isotope effects in the hydrogen abstraction from a given alkane. The theoretical calculations of the isotope effects have been carried out on the basis of transition‐state theory combined with the London‐Eyring‐Polanyi‐Sato potential energy surface. Good agreement was obtained between experiment and theory, when tunnel effects were taken into consideration.
Flow Method Vapour Pressure Determination and Characterization of Tetrakis(Trifluoropentanedionato)‐Thorium(IV) and Tetrakis (Heptafluorodimethyloctanedionato)‐Thorium(IV)
Authors: Gärtner G. , Janiel P. , Rau H. , Hal H. A. M. Van , Nabben H. J. P.
Published: July 2012

Tetrakis β‐diketonates were synthesized with quadrivalent thorium and 1,1,1‐heptafluoro‐7,7‐dimethyloctane‐4,6‐dione (fod) and with 1,1,1‐trifluoropentane‐2,4‐dione (tfa). They were characterized by elemental analysis. Temperature‐dependent X‐ray diffraction data were recorded. It was found that Th(tfa)4 can be obtained as a hydrate Th(tfa)4 · H2O and also water‐free. Visual determination gives a melting point of 423 K for Th(tfa)4 · H2O and DSC gives a melting point of 407 K for water‐free Th(tfa)4. DSC also showed a phase transition in Th(fod)4 at 366 K, the second phase transition at 424 K being identical with the melting point. Vapour pressures of Th(tfa)4 and of Th(fod)4 were determined by the flow method using nitrogen as a carrier gas. The experimental data have been fitted to an equation of the form

The results are ΔRH298 = 151.2 kJ · mol−1, ΔRS298 = 310.0 J · K−1 · mol−1, ΔRcp = −259.2 J · K−1; · mol −1; for the low temperature α‐modification of Th(fod)4, ΔRH298 = 130.6 kJ · mol−1, ΔRS298 = 253.5 J · K−1 · mol−1 and ΔRcp = −259.2 J · K−1 · mol−1 for the β‐modification at temperatures above 366 K, and ΔRH298 = 154.6 kJ · mol−1, ΔRS298 = 326.1 J · K−1 · mol−1, ΔRcp = −170.8 J · K−1 · mol−1 for water‐free Th(tfa)4.
Photoelectrochemical Etching of n‐MoSe2
Authors: Tenne R. , Wold A.
Published: July 2012

The photoelectrochemical etching of n‐MoSe2 was investigated. The photocurrent of a regenerative photoelectrochemical cell comprising the above material in polyiodide solution is improved quite significantly following that treatment. Best results were obtained when the photoelectrode was photoetched under short circuit conditions and high irradiance. As was previously observed, for other layered compounds, very few etch pits are produced. This is rather surprising in view of the morphology of photoetched CdSe and the like. We discuss this point in detail and give first hints to explain this difference.
Amorphous Semiconductor‐Electrolyte Junction. A New Interpretation of the Impedance Data of Amorphous Semiconducting Films on Metals
Authors: Quarto Francesco Di , Sunseri Carmelo , Piazza Salvatore
Published: July 2012

On the basis of the theory of amorphous semiconductor Schottky barrier an equivalent electrical circuit of the amorphous oxide film/electrolyte interface is proposed.—The analytical expressions for the equivalent conductance and capacitance of the barrier are reported in the hypothesis of a constant density of states within the mobility gap.—According to this model, the semiconducting properties and the impedance behaviour at different frequencies of anodic oxide films on Niobium are interpreted by taking into account the amorphous nature of the films.—An explanation for the anomalous behaviour of the Mott‐Schottky plots usually observed with amorphous anodic oxide films is presented.—The possible extension of such a model to different metal/anodic oxide/electrolyte junctions is suggested.
Coverage Dependence of CO Electrosorption on Palladium: An in‐situ IR Study
Authors: Solomun T.
Published: July 2012

In situ IR spectra of CO adsorbed onto a smooth polycrystalline Pd electrode in 1 M HCIO4 were obtained as a function of surface coverage. CO surface coverage was obtained by direct electrochemical oxidation of the adsorbed CO. At low coverages a single, broad adsorption band was observed at a vibrational frequency attributed to CO in a three‐coordinate surface site. Three‐coordinated species are completely converted, over a relatively narrow coverage range, into an overlayer comprising CO adsorbed on a two‐coordinate site. This layer coexists with an increasing amount of linearly bonded CO as the coverage is increased up to the saturation value.
Internal Oxidation of Impurities in Palladium Investigated by X‐Ray Absorption Spectroscopy
Authors: Lengeler B.
Published: July 2012

The internal oxidation of thirteen dilute palladium alloys which where oxidized for one hour between 1037 and 1053°C has been investigated by X‐ray absorption spectroscopy. When oxygen‐impurity complexes are formed the K or L3 absorption edges of the impurities are shifted to higher energies. The structural details of the complexes formed were studied by means of the corresponding EXAFS. Pt, Au, Pb and Bi form no impurity‐oxygen‐complexes. All other impurities investigated (Y, Zr, Nb, Mo, Gd, Yb, Lu, Hf, Th) are oxidized to the highest state of oxidation. Most of them form well‐crystallized oxides (Y2O3, Nb2O5, Gd2O3, Yb2O3, Lu2O2, HfO2, ThO2). Zr and Mo form only poorly crystallized precipitates in which only one or two shells around the impurities are visible.
The Endoperoxide of Mesodiphenylhelianthrene. Four Reaction Channels Leading from Different Upper Excited Electronic States to Cycloreversion
Authors: Schmidt R.
Published: July 2012

The photocycloreversion of the endoperoxide of mesodiphenylhelianthrene (MDHPO) regenerating the parent hydrocarbon and oxygen has been investigated at ten different irradiation wavelengths. A marked stepwise energy dependence with four almost energy independent plateaus has been observed for the quantum yield Q. A correlation between the step energies and the singlet state energies of MDHPO indicates that the extraordinary energy dependence of Q is a result of four different reaction channels which originate from different thermally equilibrated Sn (n ≥ 2) singlet states and lead to cycloreversion. The quantum yield of each reaction channel has been calculated. The correlation between these values and the corresponding internal conversion energy gaps supports this interpretation.
Thermally Oxidized Iron Electrodes for Photoelectrochemical Application
Authors: Antonucci V. , Passalacqua  , Giordano N.
Published: July 2012

Air‐oxidized and CO2‐treated laminar iron electrodes have been characterized structurally (X‐ray diffraction) and photoelectrochemically (photocurrent, polarization, cyclic voltammetry, flat‐band and static potential, band‐gap and cell characteristics) in order to elucidate the role of Fe2+ and Fe3+ at the semiconductor‐electrolyte interface in the photooxidation of H2O. Surface Fe2+ increases the band‐gap and the electron‐hole recombination rate; Fe3+ causes electroreduction of O2, which is followed by oxidation of Fe2+ (Fe3O4 → Fe2O3). This affects the catalytic activity for dissociative water adsorption as Fe2+ on non‐stoichiometric α‐Fe2O3 acts as the active site.
Modellierung in der Verfahrenstechnik am Beispiel von Kristallisatoren
Authors: Mersmann A. , Kind M.
Published: July 2012

The understanding of the physical and chemical principles which govern a process is the presupposition for the design of apparatusses and plants. A process is understood, if the balances can be formulated completely, if the equilibria are known and if kinetic effects are considered correctly.—By the example of mass crystallisation from solution it is shown how balances have to be formulated for mass, energy and population density. The last of these three balances requires to consider mixing as well as kinetics. Kinetics means growth, nucleation and for example effects due to attrition because of mechanical stress applied to the crystals.—All these aspects together lead to a designing method for crystallizers which is reliable and predictive. Unfortunately, up to now not all kinetic parameters needed for design arc available.
Distinction Between Deterministic Chaos and Amplification of Statistical Noise in an Experimental System
Authors: Freund A. , Kruel Th. , Schneider F. W.
Published: July 2012

The self‐oscillating Belousov‐Zhabotinsky reaction is investigated in a CSTR for preequilibrated reactant solutions as a function of stirring rate and flow rate by recording the Ce4+ absorption as a function of time over about 200 oscillations. The oscillations display deterministic chaos particularly at high flow rates as shown by the broad‐band Fourier spectra, the strangeness of the attractors, the fractal information dimension (DI = 1.22) whose imbedding dimension is 5, and the positive Lyapounov exponents. On the basis of our computer calculations a criterion for the distinction between deterministic chaos and amplified statistical noise is proposed. This criterion is the dependence of
the average largest Lyapounov exponent on the stirring rate in the CSTR. The average largest Lyapounov exponent is positive and constant for chaos whereas it should extrapolate to zero for amplified statistical fluctuations in the limit of high stirring rates.
Dynamic Liquid State NMR and IR Study of Tautomerism and Conformations of Tetraphenyloxalamidine, a Novel Small Intramolecular Double Hydrogen Transfer System
Authors: Otting Gottfried , Rumpel Helmut , Meschede Ludger , Scherer Gerd , Limbach Hans‐Heinrich
Published: July 2012

Using Dynamic NMR Spectroscopy we have detected a novel intramolecular double hydrogen transfer in the oxalamidine (OA) system. OA is, therefore, so far the smallest known molecular unit capable of such a transfer. Because of solubility problems, experiments were performed on tetraphenyloxalamidine (TPOA, Ia) and the isotopically labeled compound TPOA‐15N4‐d20(Ib) dissolved in CD2CI2. At low temperatures TPOA exists in a number of different conformations, of which only one conformation with two intramolecular hydrogen bonds is capable of an intramolecular hydrogen transfer which shows up in the1H‐15N signal of this conformer. At low temperatures a1H‐15N doublet (88 Hz coupling constant) is observed which changes into a triplet (44 Hz coupling constant) as the temperature is raised. The position of this signal is independent of temperature and concentration. Two further conformations were detected, of which one formed strong intermolecular hydrogen bonds and underwent fast intermolecular proton exchange. Above room temperature all NH signals coalesce into an exchange‐broadened singlet.13C experiments prove that this effect is due to a fast internal conversion of all conformers. IR experiments on TPOA in CCl4did not reveal the complicated conformational behavior of TPOA. By lineshape analysis we obtained the rate constants of the HH migration, which are given by kHH= 1010.8exp(−43 kJ mol−1/RT). An upper limit for the HD exchange rates were found for a sample deuterated to 90% in the labile proton sites:kHD= exp(−53 kJ mol−1/RT), i.e.kHH/kHD= 2.1 at 298 K. The data are compared to previous results on the azophenine rearrangement.
Partial Molal Volume of Some Alkali Halides in Water—Acetamide Mixtures
Authors: Woldan Marian
Published: July 2012

Densities of solutions of NaCl, Nal, KCI, KBr, and Csl in mixtures of acetamide + water have been measured at 313.15 K using the magnetic float densimeter. The apparent molal volumes of the electrolytes calculated from the experimental data were extrapolated to infinite dilution by means of the Masson equation. The ionic partial molal volumes of the ions have been estimated. The dependence of the partial molal volumes, the ionic partial molal volumes, and the derived transfer functions of the investigated electrolytes (ions) from water to water‐acetamide mixtures on the solvent composition are discussed.
Recent results in laser biomedicine and some prospects of the future
Authors: Letokhov V. S.
Published: July 2012

Report will discuss the following problems:

Molecular mechanism of low‐intensity laser therapy

Mechanism and characteristics of laser ablation of biotissue

Femtosecond Laser Mass‐Spectrometry of Biomolecules on Surface and Future Applications for Laser Photoion Microscopy
Photodynamic therapy of age‐related macular degeneration and atherosclerosis
Authors: Ben‐Hur E. , Miller B. , Miller H. , Rosenthal I.
Published: July 2012

In photodynamic therapy, a photosensitizing dye restrictively localized to certain sites in the biological milieu, is activated by visible light to selectively destroy the stained structures. Although primarily investigated for necroting malignant tumors, this approach suggests also potential in treating other pathological conditions such as age‐related macular degeneration and atherosclerosis. Until recently, hematoporphyring derivative was practically the only dye investigated for photodynamic therapy. The use of phthalocyanine dyes is being explored as a superior alternative photosensitizer for treatment of these diseases.
Resonance enhanced multiphoton ionization of biological molecules
Authors: Beavis R. C. , Lindner J. , Grotemeyer J. , Schlag E. W.
Published: July 2012

Some applications of the powerful novel method of laser desorption combined with multiphoton ionization are shown. The mass spectra of several bio‐organic molecules are presented and their intrinsic features upon the multiphoton interaction are discussed. In every case, at low laser powers the molecular ion of the investigated sample is detected, while at higher laser powers structure dependent fragmentations can be observed.
Lasers and flashlamps in research on the mechanism of muscle contraction
Authors: Rapp G. , Poole K. J. V. , Maeda Y. , Ellis‐Davies G. C. R. , Kaplan J. H. , McCray J. , Goody R. S.
Published: July 2012

High intensity pulsed light sources are currently being used in two major applications in muscle research. The first of these involves rapid photolytic release of metabolites, e.g. adenosine triphosphate or calcium ions, from inert, photosensitive precursors. This allows rapid kinetic experiments in muscle fibres which would otherwise be impossible because of the long diffusion times even of small molecules into the lattice of thick and thin filaments. Examples of the use of lasers and flash lamps for this purpose will be given, with particular emphasis on dynamic structural investigations using synchrotron radiation as a high intensity X‐ray source for monitoring structural changes by low angle diffraction. The second application involves the use of solid state lasers to produce powerful light pulses in the infrared region to achieve temperature jumps in muscle fibres. This, in conjunction with the use of synchrotron radiation, allows the kinetics of interesting structural transitions in muscle fibres to be studied.
Structures of Some Derivatives of Chloral. An X‐Ray and NQR Study
Authors: Hashimoto Masao , Nakamura Yasushige , Adachi Masahiro , Hamada Kensaku , Mano Koichi
Published: July 2012

Crystal structures of the stable and a metastable phases of 2,4‐bis(trichloromethyl)‐benzo‐1,3‐dioxine‐6‐carboxylic acid (TMB‐COOH) and 2,4‐bis(trichloromethyl)‐benzo‐1,3‐dioxine‐6‐amine (TMB‐NH2) were determined at room temperature. Crystal data are as follows; TMB‐COOH (stable): monoclinic, space group C52h‐P21/n, a = (1052.6 ± 0.2) pm, b = (2582.2 ± 0.4) pm, c = 598.7 ± 0.3) pm, β = 99.86° ± 0.02°, R = 0.053; TMB‐COOH (metastable): monoclinic,space group C52h‐P21/c, a = (577.5 ± 0.5) pm, b = (2087.2 ± 1.1) pm, c = (1318.6 ± 0.7) pm, β = 91.98° ± 0.06°, R = 0.098; TMB‐NH2: orthorhombic, space group C92v‐Pna21, a = (2539.0 ± 0.2) pm, b = (1005.1 ± 0.1) pm, c = (566.7 ± 0.1) pm, R = 0.049. Disorder of hydrogen atom in the OH ··· O hydrogen bond system was found for the cyclic dimers of TMB‐COOH in both phases. Judging from the molecular structures determined, chloral hydrate and 4‐substituted phenols seem to react in a stereospecific way to give a single conformer found in these crystals. The 35Cl NQR spectra of TMB‐COOH, TMB‐NH2 and related compounds were measured in the range 77 ≦ T/K ≦ 400. The temperature dependence of the NQR spectra showed that the potential barrier hindering the reorientation of the group is considerably different for the two nonequivalent CCl3 groups in a molecule. Atom‐atom potential calculations based on the crystal data showed that the difference is of intermolecular nature. The NQR frequencies calculated from the orbital populations obtained by the CNDO/2 MO method are consistent with the observed one.
A control method based on modal transformation for biped robots to climb unknown steps
Authors: Shimmyo Shuhei , Nakazato Miki , Mikami Kei , Sato Tomoya , Sakaino Sho , Ohnishi Kouhei
Published: July 2012

This paper proposes a control method based on a modal transformation for biped robots to climb unknown steps. The method is able to control the foot position of the biped robot and the ground reaction force acting in the vertical direction when the biped robot climbs unknown steps in a double support phase. The effectiveness of the proposed method is confirmed by the results of simulations and experiments. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 181(3): 59‐69, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21265
Efficient sampling of protein conformational space using fast loop building and batch minimization on highly parallel computers
Authors: Tyka Michael D. , Jung Kenneth , Baker David
Published: July 2012

All‐atom sampling is a critical and compute‐intensive end stage to protein structural modeling. Because of the vast size and extreme ruggedness of conformational space, even close to the native structure, the high‐resolution sampling problem is almost as difficult as predicting the rough fold of a protein. Here, we present a combination of new algorithms that considerably speed up the exploration of very rugged conformational landscapes and are capable of finding heretofore hidden low‐energy states. The algorithm is based on a hierarchical workflow and can be parallelized on supercomputers with up to 128,000 compute cores with near perfect efficiency. Such scaling behavior is notable, as with Moore's law continuing only in the number of cores per chip, parallelizability is a critical property of new algorithms. Using the enhanced sampling power, we have uncovered previously invisible deficiencies in the Rosetta force field and created an extensive decoy training set for optimizing and testing force fields. © 2012 Wiley Periodicals, Inc.
A robust inner–outer hierarchically semi‐separable preconditioner
Authors: Xia J.
Published: July 2012

In this paper, an inner–outer preconditioner for symmetric positive definite matrices based on hierarchically semi‐separable (HSS) matrix representation is presented. A sequence of new HSS algorithms are developed, including some ULV‐type HSS methods and triangular HSS methods. During the construction of this preconditioner, off‐diagonal blocks are compressed in parallel, and an approximate HSS form is used as the outer HSS representation. In the meantime, the internal dense diagonal blocks are approximately factorized into HSS Cholesky factors. Such inner factorizations are guaranteed to exist for any approximation accuracy. The inner–outer preconditioner combines the advantages of both direct HSS and triangular HSS methods, and are both scalable and robust. Systematic complexity analysis and discussions of the errors are presented. Various tests on some practical numerical problems are used to demonstrate the efficiency and robustness. In particular, the effectiveness of the preconditioner in iterative solutions has been shown for some ill‐conditioned problems. This work also gives a practical way of developing inner–outer preconditioners using direct rank structured factorizations (other than iterative methods). Copyright © 2012 John Wiley & Sons, Ltd.
Effect of growth media on cell envelope composition and nitrile hydratase stability in Rhodococcus rhodochrous strain DAP 96253
Authors: Tucker Trudy-Ann , Crow Sidney A , Pierce George E
Published: July 2012

Rhodococcus is an important industrial microorganism that possesses diverse metabolic capabilities; it also has a cell envelope, composed of an outer layer of mycolic acids and glycolipids. Selected Rhodococcus species when induced are capable of transforming nitriles to the corresponding amide by the enzyme nitrile hydratase (NHase), and subsequently to the corresponding acid via an amidase. This nitrile biochemistry has generated interest in using the rhodococci as biocatalysts. It was hypothesized that altering sugars in the growth medium might impact cell envelope components and have effects on NHase. When the primary carbon source in growth media was changed from glucose to fructose, maltose, or maltodextrin, the NHase activity increased. Cells grown in the presence of maltose and maltodextrin showed the highest activities against propionitrile, 197 and 202 units/mg cdw, respectively. Stability of NHase was also affected as cells grown in the presence of maltose and maltodextrin retained more NHase activity at 55 °C (45 and 23 %, respectively) than cells grown in the presence of glucose or fructose (19 and 10 %, respectively). Supplementation of trehalose in the growth media resulted in increased NHase stability at 55 °C, as cells grown in the presence of glucose retained 40 % NHase activity as opposed to 19 % without the presence of trehalose. Changes in cell envelope components, such mycolic acids and glycolipids, were evaluated by high-performance liquid chromatography (HPLC) and thin-layer chromatography (TLC), respectively. Changing sugars and the addition of inducing components for NHase, such as cobalt and urea in growth media, resulted in changes in mycolic acid profiles. Mycolic acid content increased 5 times when cobalt and urea were added to media with glucose. Glycolipids levels were also affected by the changes in sugars and addition of inducing components. This research demonstrates that carbohydrate selection impacts NHase activity and stability. Cell envelope components such as mycolic acids are also influenced by sugars and inducers such as cobalt and urea. This is information that can be useful when implementing rhodococcal catalysts in industrial applications.
Why “More Work for Mother?” Knowledge and Household Behavior, 1870–1945
Authors: Mokyr Joel
Published: July 2012

It is widely agreed that the burden of housework in the industrialized West did not decrease as much as might be expected since 1880, and may have actually increased for long periods. The article proposes a new explanation: that increases in knowledge on the causes and transmission mechanisms of infectious diseases persuaded women that household members' health depended on the amount of housework carried out. The article traces the origin of this knowledge in the scientific developments of the nineteenth century and describes the mechanisms by which households were persuaded to allocate more time and resources to housework.
A Shocking View of Economic History
Authors: Neal Larry
Published: July 2012

Economics, like geology, is an historical science. Geology has made incredible advances by accepting it is an historical, rather than a laboratory science. Economic historians can help economics make similar advances by adopting the research strategies of modern geology. Intensely empirical and global in their range, today's geologists focus on the historical remains of shocking, usually catastrophic, events in the earth's past. Already empirical and global, economic historians have ample shocks to study whether their specialty is population, technology, or institutions. A few examples of the possibilities should stimulate us to reinvigorate our parent disciplines of economics and history.
African-American Economic Mobility in the 1940s: A Portrait from the Palmer Survey
Authors: Collins William J.
Published: July 2012

I use retrospective work histories from a unique dataset to follow workers in six cities through occupational, industrial, and geographic moves, thereby characterizing aspects of black economic mobility during the 1940s that cannot be viewed through the Census data. Relatively few migrants were drawn directly from the southern agricultural sector. Black occupational upgrades were larger than white upgrades on average but black upgrades were smaller than those of observationally similar whites.
Central Planning and Unintended Consequences: Creating the Soviet Financial System, 1930–1939
Authors: Gregory Paul R. , Tikhonov Aleksei
Published: July 2012

We use the Soviet state and party archives to study the creation of the Soviet financial system. Although its framers intended to centralize all emission and monitoring of money and credit, in practice the system was characterized by informal mechanisms involving multiple players, soft budget constraints, and massive moral hazards. Enterprises issued “illegal” commercial credits and surrogate monies, causing liquidity growth to far outpace real economic activity. When confronted with the choice of solvency versus plan fulfillment, firms always chose the latter: credit risks were passed on to solvent enterprises, the state bank, and the state budget.
Modeling the speech community: Configuration and variable types in the Mexican Spanish setting
Authors: Ana Otto Santa , Parodi Claudia
Published: July 2012

This article proposes a comprehensive model of the SPEECH COMMUNITY in sociolinguistics that reworks Labov's model, which has been criticized as being restrictive. Fieldork in non-metropolitan Mexico demonstrates the utility of our model, which can be applied across both urban and non-urban domains. It is compatible with the Milroys' central mechanism for the description of individual speech usage and group cohesion or susceptibility to change in terms of the social network. Based on linguistic variable types, this model has a hierarchy of four nested fields (speech community configurations) into which each individual is placed, according to his/her demonstrated recognition of the social evaluation associated with the variables. At the most local configuration, speakers demonstrate no knowledge of generally stigmatized variables; in the second, speakers register an awareness of stigmatized variables; in the third, an awareness of stigmatized and regional variables; and in the fourth, speakers model standard variants over regional ones. This model classifies the kinds of sociolinguistic variables that are pertinent in this social setting and also provides a structured manner for dealing with dialect contact dynamics. (Speech community, social network, Spanish, Mexico, dialect, diffusion, variables.)
Native woodlands of the Inner Hebrides
Authors: Ball M. E.
Published: July 2012

Synopsis

Woodland is native throughout the Inner Hebrides at low elevations wherever exposure and soil conditions permit. Although mostly destroyed in the distant past, sufficient remnants remain to characterise Hebridean woods and provide a basis for their study and conservation. Surveys have revealed that the types represented are those dominated by wych-elm, ash, oak, birch, hazel, alder and sallows. All but the smallest and most exposed islands have remnant woodlands but the widest variety of types and the most demanding species occur on the larger islands of Mull and Skye. The woodland flora is rich in oceanic species and poor in continental, boreal plants characteristic of the mainland pine–birch woodlands, although Scots pine probably once occurred sparsely in the primaeval woodland.

The most powerful factor influencing between-site variation in the woodland flora is geology, with wychelm, ash and hazel associated with soils on Durness limestone, Mezozoic rocks and basalts, and oak and birch characteristic of the Torridonian sandstones, acid Moine rocks, Lewisian gneiss and granites. There is little active conservation; the most pressing need is protection from grazing and fire to ensure long-term survival.
Experimental Investigations on Dynamic Characteristics of a Multilayer Piezoelectric Stack Actuator
Authors: Lin Hsien-Yang , Ma Chien-Ching
Published: July 2012

Multilayer piezoelectric stack actuators are widely used in many industrial applications and the investigation on the dynamic behavior of this element is needed. In this study, two optical interferometric techniques called amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) and laser Doppler vibrometer (LDV) are used to experimentally investigate the vibration characteristics of a single-layer piezoelectric disc and a multilayer piezoelectric stack actuator. These two techniques are full-field measurement for AF-ESPI and point-wise displacement measurement for LDV. Because the clear fringe patterns obtained by the AF-ESPI method will be shown only at resonant frequencies, both the resonant frequencies and corresponding vibration mode shapes of the piezoelectric disc and the multilayer piezoelectric stack actuator are obtained simultaneously by the AF-ESPI method. Interferometric fringe patterns for both the in-plane and out-of-plane vibration mode shapes are demonstrated. In addition to the proposed two optical techniques, numerical computations based on a commercially available finite element package are presented for comparison with the experimental results. Good agreement between the measured data by experimental methods and the numerical results predicted by FEM is found in resonant frequencies and mode shapes for the single-layer piezoelectric disc. However, some discrepancies are observed for the results obtained by AF-ESPI and impedance analysis for the multilayer piezoelectric stack actuator. A detailed discussion is made to address important issues of this problem.