bluuebunny/crossref_metadata_2025 huggingface dataset:
Theory of Cyclic Voltammetry at Microdisk Electrodes
Authors: Heinze Jürgen
Published: July 2012

The cyclic voltammetric response, which is obtained by measurements at microdisk electrodes (R ± 1 mm), may deviate strongly from theoretical predictions. The cause of such effects is due to nonlinear diffusion processes, which, in principle, are present at unshielded disk electrodes. They increase with diminishing electrode radii and slow scan rates in accordance with the value of the dimensionless parameter = (D/aR2)1/2. A quantitative description of nonlinear mass transport to microdisk electrodes can be achieved with the aid of a two‐dimensional simulation based on an implicit difference approximation. The agreement with experimental data is very close. The reversible and the quasi‐reversible charge transfer is discussed. To facilitate the interpretation of cyclic voltammograms, working‐curves and diagnostic criteria are presented.
Vapour Pressure of Ternary LiClNaClAlCl3 Melts
Authors: Knapstad Børge , Linga Hogne , Øye Harald A.
Published: July 2012

The vapour pressure and vapour composition have been determined for ternary LiClNaClAlCl3 melts, dilute in AlCl3. Three experimental methods have been employed in order to obtain unambiguous results; a) total pressure of the boiling liquid, b) vapour composition by direct condensation of the boiled‐off vapour, c) mean molecular weight from inert gas transportation. The major gas molecules are NaAlCl4, LiAlCl4, and AlCl3. NaAlCl4 is found to be the major gas species over most of the composition range even though the total pressure of the binary LiClAlCl3 system is considerable higher than that for the corresponding NaClAlCl3 system. The results are described in terms of a semiempirical thermo‐dynamic model.
Untersuchung von Trübungserscheinungen im Einphasengebiet wäßriger Lösungen nichtionogener Tenside
Authors: Platz G.
Published: July 2012

Solutions containing Triton‐X‐100 (p‐octylphenoxydecaethyleneglycol), potassiumchloride and water were investigated by dynamic light scattering and temperature jump measurements. It could be shown that the strong turbidity effects in the one phase region near the cloud point depend on increasing concentration fluctuations and not on statistical distributions of isolated large micellar aggregates. In the limit of small q‐values the same expression is valid as well for the intensity correlation function as for the T‐jump relaxation of the scattered light: 1/r = 2Dq2 · (qζ << 1). D is the mutual diffusion coefficient, q is the length of the scattering vector: q = sin (v/2). ζ is the correlation length. The change Δα of the turbidity α with time is given by the following expression which is valid for q ζ <<1:

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From dynamic light scattering measurements on solutions of micellar aggregates diffusion coefficients of the micelles are obtained. If the increasing scattering intensity depends on increasing molecular weights T‐jump experiments will yield the two relaxation times for micelle formation and redistribution. With this investigation method it is therefore possible to distinguish between changes of the fluctuation term or structure factor S(q) and changes of molecular weights of scattering aggregates.
The Mercury‐Photosensitized Decomposition of Hexamethyldisilane
Authors: Davidson I. M. T. , Potzinger P. , Reimann B.
Published: July 2012

The kinetics and mechanism of the mercury‐photosensitized decomposition of hexamethyldisilane have been studied. It has been confirmed that the initially‐formed radical, Me3SiSi(Me2)CH2, undergoes a unimolecular rearrangement; Arrhenius parameters have been measured for this rearrangement and for subsequent reactions of the rearranged radical:

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The significance of these Arrhenius parameters in silicon chemistry is discussed by means of thermochemical calculations.
Solvation of Beryllium Ions in Water‐Hexamethylphosphoric Triamide Mixtures
Authors: Füldner H.‐H. , Strehlow H.
Published: July 2012

The relative amounts of the differently solvated species Be(HMPT)i(H2O)2+4‐i have been determined as a function of solvent composition using 31P‐NMR measurements. The formation of a Bc(NO3)+ inner‐sphere complex was established at higher mole fractions of HMPT. The consecutive stability constants of the Be‐HMPT complexes were obtained and compared with those calculated more indirectly using Bjerrum's method [1].
Ionic Dissociation of Aqueous Hydrobromic Acid. Part 4. Estimate from 81Br and High Temperature 1H Nuclear Magnetic Resonance Data
Authors: Soffer N. , Marcus Y.
Published: July 2012

Nuclear quadrupole relaxation and chemical shift data for 81Br in aqueous 10 to 20 m hydrobromic acid and viscosity data were obtained at 27 °C. They are consistent with previously obtained 1H NMR data. New 1H chemical shifts obtained at 90 and 120 °C lead to degrees of dissociation that do not differ significantly from the values obtained at 6 to 60 °C.
The Formation of Carbonaceous Species from Carbonmonoxide and from Carbonmonoxide/Hydrogen on Cobalt Catalysts. Indications of Metal‐Support Interaction
Authors: Outi A. , Rautavuoma I. , Van Baan Hessel S. Der
Published: July 2012

The reaction of carbon monoxide and carbon monoxide/hydrogen mixtures with two catalysts, a pure cobalt catalyst and a cobalt on alumina catalyst has been studied, mainly in the thermobalance. It appears that the support prevents carbon diffusion into the cobalt crystallites, whereas on the pure cobalt catalysts the carbide Co3C is formed as the first product. Hydrogen efficiently prevents the formation of carbides in the pure cobalt catalysts; on the supported catalysts relatively large quantities of intermediates are deposited from carbon monoxide/hydrogen mixtures. The observed effects are explained by an interaction between alumina and cobalt that reduces the cobalt‐carbon bond strength and the hydrogen activity on the supported catalyst.
Mass Spectrometric Studies on the Vapour Phase Composition over Solid and Fused Cs3Sb
Authors: Busse Bernd , Weil Konrad G.
Published: July 2012

Kundsen cell mass spectrometric measurements are reported on the composition of the vapour over solid and fused Cs3Sb. The main constituents of the vapour are species which are also present over the pure metals, Cs, Cs2, Sb, Sb2, and Sb4. Besides these a number of signals are recorded which can be attributed to intermetallic molecules and their fragments. Careful studies of the ionisation curves for the different species made it possible to evaluate the complete fragmentation scheme. It leads to the conclusion that the following intermetallic species are present in the equilibrium vapour: Cs2Sb4, CsSb2, Cs2Sb, and Cs2Sb2. From that it can be concluded that the interactions which stabilize the compounds are different from those in the condensed phases, where Cs3Sb, CsSb, and Cs3Sb7 are congruently melting compounds.
Equation of State for Gaseous H2S
Authors: Rau Hans , Mathia Wolfgang
Published: July 2012

PVT‐measurements on gaseous H2S up to 760 K and 600 bar were performed. The hot gas was in contact with silica only, so that no corrosion occurred. The results together with literature data were compared with equations of state, the parameters of which had been fitted by least‐squares‐methods. The Redlich‐Kwong‐equation is recommended for calculations, because values computed from this equation do not differ more from the measured values than those computed from equations with more than two parameters.
Proton Magnetic Resonance Study of Ligand Exchange on Tetrakis (Methylmethylphenylphosphinate) Beryllium(II) and Tetrakis (Dimethylmethylphosphonate) Beryllium(II) in Non‐Aqueous Solvents
Authors: Thaczuk M. N. , Lincoln S. F.
Published: July 2012

Ligand exchange on tetrakis(methylmethylphenylphosphinate)beryllium(II), [Be(mmpp)4]2+, and its dimethylmethylphosphonate analogue, [Be(dmmp)4]2+, has been studied in CD3NO2, CD3CN, and CD2Cl2 solvents using 1H (90 MHz) NMR methods. When the solvent is CD3CN or CD2Cl2 ligand exchange on [Be(mmpp)4]2+ exhibits a rate independence of [mmpp]free whereas when the solvent is CD3NO2 the ligand exchange rate = k2 4[Be(mmpp)2+4][mmpp]free where k2 (298.2K) = 0.22 ± 0.01 dm3 mol−1 s−1, ΔH≠ = 68.7 ± 0.9 kJ mol−1, and S≠ = −26.1 ± 2.7 J K−1 mol−1. When the solvents is CD2Cl2 ligand exchange on [Be(dmmp)4]2+ exhibits a rate independence of [dmmp]free whereas when the solvent is CD3CN the ligand exchange rate = 4(k1 + k2 [dmmp]free) [Be(dmmp)2+4] where k1 (298.2 K) = 0.93 ± 0.04 s−1, ΔH≠ = 64.3 ± 1.2 kJ mol−1, ΔS* = −29.7 ± 3.7 J K−1 mol−1, k2 (298.2 K) = 0.33 ± 0.05 dm3 mol−1 s−1, ΔH≠ = 69.4 ± 4.4 kJ mol−1, and ΔS≠ = ‐ 21.3 ± 13.1 J K−1 mol−1. These data are interpreted in terms of dissociative (D) and associative (A) ligand exchange mechanisms and the effect of the solvent on mechanism is discussed. An apparent ΔH≠/ΔS≠ isokinetic relationship is used as the basis of a comparison of the lability of beryllium(II) with other metal centres.
On the Interplay between Geometry and Mobility in Intramicellar Kinetics
Authors: Hatlee Michael D. , Kozak John J. , Grätzel Michael
Published: July 2012

The role of geometry in influencing reaction‐diffusion processes in spherical versus rod‐shaped micellar aggregates is studied. Previously‐reported data on pyrene excimer fluorescence in dodecylammonium chloride (DAC) micellar solutions is analyzed by applying a theory proposed by Adam and Delbrück to account for timing effects associated with the reduction of dimensionality in diffusion‐controlled processes. Our results show that the overall dynamics are governed by an interplay between the characterizing geometry of the host micellar aggregate and the mobility of the solubilized probe molecules in the assembly.
The Thermal Conductivity of Mixtures of Hydrogen with Nitrogen
Authors: Kestin J. , Nagasaka Y. , Wakeham W. A.
Published: July 2012

The paper reports absolute measurements of the thermal conductivity of mixtures of hydrogen and nitrogen in the pressure range 0.7 to 10 MPa at a nominal temperature of 27.5 °C. The experimental results have an estimated uncertainty of ±0.3%. The mixture thermal conductivity in the limit of zero‐density can be described with the aid of the available kinetic theory only if empirical adjustments are made to some of the collision‐integral ratios characteristic of the unlike interactions. The need for these adjustments is taken as evidence that the available kinetic theory formulae are not sufficiently accurate for gas mixtures in which the mass ratio of the molecules is large. At elevated densities the calculation scheme of Mason and his coworkers cannot provide a description of the experimental data within their uncertainty, even when empirical adjustments of a parameter characteristic of the unlike interactions are allowed.
Determination of the Rotational Correlation Time of Water by Proton NMR Relaxation in H217O and Some Related Results
Authors: Lankhorst D. , Schriever J. , Leyte J. C.
Published: July 2012

Analysis of the1H‐17O dipolar contribution to the proton longitudinal relaxation rate in17O‐enriched water yields a correlation time for re‐orientation of the O–H vector τrOH= (1.71 ± 0.07) ps in H2O at 25 °C. This result is insensitive to uncertainties in the calculated intermolecular relaxation contribution. From1H, D, and17O relaxation rates in H2O/D2O mixtures deuterium isotope effects on the correlation times were estimated. The quadrupole coupling constants of D and17O in liquid water were determined.
Distribution of Chloride and Bromide Counterions of Cetyltrimethylammonium Micelles in Water. A Fluorescence Study
Authors: Wolff Thomas , Von Bünau Günther
Published: July 2012

Relative fluorescence intensities of anthracene, fluorene, and 9,10‐dimethylanthracene in aqueous solutions of cetyltrimethylammonium bromide (CTAB) and cetyltrimethylammonium chloride (CTAC) have been measured as functions of surfactant concentrations. Fluorescence was found to be quenched by bromide but not by chloride ions. At low total concentrations (cs < 0.01 M) of CTAB/CTAC‐mixtures quenching efficiencies depend linearly on the CTAB‐mole fraction. Deviations from linearity are observed for higher cs‐values and attributed to preferential binding of bromide ions to the micelles. Additional deviations at cs > 0.3 M are connected with changes in micelle shape (rod formation).
Magnetic Circular Dichroism and Molecular Orbital Studies on the Intramolecular Charge‐Transfer Transitions in the Bridged Tropylium Cations
Authors: Tajiri Akio , Hatano Masahiro , Nakazawa Tomoo , Nakasuji Kazuhiro , Murata Ichiro
Published: July 2012

The magnetic circular dichroism (MCD) spectra of the bridged tropylium cations have been measured at room temperature. Very weak MCD bands have been observed in the longest wavelength region and assigned to the intramolecular charge‐transfer (CT) transitions arising from the electronic excitations from the highest occupied MO(HOMO) of the remote chromophore to the lowest vacant MO(LVMO) of the tropylium cation. In the shorter wavelength region, four distinct MCD bands with alternating sign have been detected, clarifying four π→π* transitions in the perturbed tropylium moiety.
Absorptions‐ und Fluoreszenzspektren sowie Dissoziationskonstanten der Grund‐ und ersten angeregten Singulettzustände von 4′‐Hydroxyflavon und 4′‐Methoxyflavon [1]
Authors: Wolfbeis Otto S. , Schipfer Rudolf
Published: July 2012

The absorption and fluorescence spectra of 4′‐hydroxyflavone and 4′‐methoxyflavone have been studied as a function of the acidity (pH or Ho) of the solution. Dissociation constants have been determined for the ground and first excited singlet state. The values are compared with those obtained from Förster‐Weller calculations.—The pKa's obtained by fluorimetry are rather similar to the ground state pKa's, which indicates a rapid deactivation of the S1‐state, before prototropic equilibration is complete.—On changing from protic to deuterated solvents partially strong effects are observed with respect to the fluorescence intensity, but also to the shape of the curves. It is evident, that proton transfer processes in the excited state significantly contribute to fluorescence quenching, thus making the fluorescence quantum yields strongly acidity dependent.
Energetics of Negative Ion Formation in Dissociative Electron Attachment to CCl4, CFCl3, CF2Cl2, and CF3Cl
Authors: Illenberger E.
Published: July 2012

Negative ion formation from CCl4, CFCl3, CF2Cl2, and CF3Cl under low energy (0–10 eV) electron impact has been studied mass spectrometrically. Electron affinities of negative ion fragments resulting from dissociative electron attachment are determined by measuring both the appearance potentials and the translational excess energies over the resonances. For the process e− + CF3Cl → Cl− + CF3 the decomposition of the negative ion intermediate CF3Cl−* shows a strong non statistical behaviour which may be explained by the short lifetime of the negative ion state with respect to autodetachment of the extra electron.
Kinetics and Equilibria of Alkali Metal Complexes with Benzo‐Substituted (2,2,2) Cryptands in Propylene Carbonate
Authors: Cox B. G. , Garcia‐Rosas J. , Schneider H.
Published: July 2012

Stability constants and formation and dissociation rate constants of alkali metal complexes with (2B,2,2) and (2B,2B,2) cryptands in propylene carbonate have been obtained. The incorporation of benzene rings in the ether bridges of the (2,2,2) molecule has the effect of reducing the stability and increasing the dissociation rates of the complexes. The results are compared with previous studies on these and other cryptands in water and methanol. The difference in the stability constants of the complexes on changing the solvent from methanol to propylene carbonate is discussed in terms of the different solvation of the species involved. For a given metal (except for Cs+), it was found that the stability constants of complexes with several cryptands in propylene carbonate can be linearly correlated with the corresponding values in methanol.
The Interaction of Protic Compounds with Thioindigo
Authors: Karstens T.
Published: July 2012

By measuring the temperature dependence of fluorescence intensities and lifetimes a principal difference in the quenching behaviour of thioindigo with aliphatic and aromatic protic compounds is observed. From absorption and IR spectra, an interaction in the groundstate between thioindigo and phenol has to be assumed. Using various substituted phenols the influence of α‐electron density on complex formation is shown.
Diatomics‐in‐Molecules: A Present‐Day Extension of the LEP Formalism
Authors: Kuntz P. J.
Published: July 2012

The relationship of the DIM method to the LEP formalism provides insight into the ways of extending the semi‐empirical description of chemical relations to systems involving complex electronic structures. It is also shown how ab initio ondiatomicmolecules can guide one in choosing an optimum DIM model for a polyatomic system.
Experimental Observations Regarding Transition States
Authors: Brooks Ph. R. , Curl R. F. , Maguire T. C.
Published: July 2012

Modern laser and molecular beam techniques make feasible experimental studies of transition states in chemical reactions. Rough estimates of the signals to be expected under different circumstances are described. Several recent studies are discussed with comments on the type of information which can be obtained.
Optical Preparation of Aligned Reagents
Authors: Zare R. N.
Published: July 2012

Expressions are derived for the degree of alignment caused when a target molecule undergoes an electric‐dipole‐allowed transition induced by the absorption of plane polarized light.
Transition State Theory and Beyond — A Constrained Phase Space Approach
Authors: Pollak E. , Levine R. D.
Published: July 2012

The information‐theoretic, maximum entropy formalism for the computation of reaction rates is reviewed, with several applications and computational examples. Attention is focused on the essential ideas and, for simplicity, the analytical development is carried out only for collinear collisions at a given total energy. Particular attention is given to the theories which are of maximal entropy subject to a constraint on the mean number of times n that a critical surface enroute from reagents to products is crossed by the system. Transition state theory is derived as the special case when the mean number of crossings is taken to be unity. The approximation n = 1 is often exact in the threshold region, but as the energy increases it rapidly deteriorates. When n > 1, it is found not to be a dominant constraint. Rather, the nonuniform distribution of trajectories in phase space is the major restriction on the reaction rate. It proves possible to treat this case analytically, and explicit results, illustrated by the H + H2 and F + H2 reactions, are provided.
ESR‐spektroskopische Untersuchungen der Reaktion von O(3P)‐Atomen mit Dichlormonoxid
Authors: Wecker D. , Johanssen R. , Schindler R. N.
Published: July 2012

The kinetics of the reaction

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was studied using a fast flow system with ESR‐detection to monitor the O‐atom concentrations. Model calculations were employed to take into account secondary reactions of the intermediates. From investigations in the temperature range 233 to 297 K the room temperature rate constant k1 = (3,1 ± 0,5) · 10−12 cm3 s−1 and an apparent activation energy of EA = (5,8 ± 1,2) kJ/mol−1 were derived.
pVT Data for Fluid Sulphur up to 1200°C and 1000 bar
Authors: Fischer R. , Schmutzler R. W. , Hensel F.
Published: July 2012

The paper presents the first experimental results of the equation of state and its derivatives such as isothermal compressibility, thermal expansion coefficient and thermal pressure coefficient for fluid sulphur which extend over the entire liquid‐vapour range, including the supercritical region up to 1200°C and 1000 bar. Sulphur has a critical point at Tc = 1040°C, pc = 203 bar and pc = 0.58 g/cm3.
Thermodynamic Investigations on Menshutkin Complexes III. Excess Function of Liquid SbCl3/Benzene Mixtures
Authors: Sondern Chr. , Perkampus H.‐H.
Published: July 2012

The excess functions of liquid SbCl3/benzene mixtures have been determined for the temperature range 333 ≦ T/K ≦ 363. For the calorimetric investigation of the heats of mixing a special mixing cell was constructed to be used with a microcalorimeter. The activity coefficients of the components in the mixture were determined by measuring the total equilibrium pressure as a function of temperature and concentration and applying Gibbs‐Duhem's law. All excess functions show negative signs and the same dependence on concentration, thus establishing complex formation between the two components in the liquid state. (HE = ‐ 3.6 kJ mol−1, SE = −7.83 JK−1 mol−1 at xbenzenemax = 0.4).
Electrochemical Determination of Local Hydrogen Concentration in a Metal
Authors: Schoonman J. , Franceschetti D. R. , Hanneken J. W.
Published: July 2012

An electrochemical method for the determination of the local hydrogen activity, and indirectly the local hydrogen concentration, in a metal sample is described. The sample is employed as part of a concentration cell, with the remainder of the cell contained in a movable probe designed so that the electrolyte contacts only a small portion of the sample surface. Two such probes are described, one using an aqueous electrolyte, the other a solid proton conductor. As examples of the method, activity measurements are reported for a palladium wire nonuniformly loaded with hydrogen, and for pressed pellets of Zr powder and crystalline and amorphous samples of intermetallic compounds loaded with hydrogen by both physical and electrochemical means.
Photophysical Processes in Cyanobiphenyl Derivatives. II. Cyanobiphenyl Derivatives as Fluorescent Probes in Micellar Environment
Authors: David C. , Szalaí E. , Baeyens‐Volant D.
Published: July 2012

Two 4‐cyano‐4′‐alkoxybiphenyl derivatives (3 COB‐8 COB) have been used as fluorescent micellar probes in four different surfactants (SDS, CTAB, NPh‐EO‐9, and NPh‐EO‐30) the concentration [S] of which varies in a broad range around the CMC. The distribution constant K for the solubilization of the probes between micelles and water and the solubility S in the surfactant are obtained from the absorption spectra after saturation of the sample either by stirring at room temperature or by ultrasonication. CMC values in agreement with those reported in the literature are determined from the curves λmax = f[S]. According to the saturation method, a different type of aggregate is formed below the CMC in the case of 8 COB. The emission spectra demonstrate that the COB derivatives are preferentially solvated in polar environment (polarity > ethanol). The assignment of the observed enhanced line width as compared to homogeneous solutions reveals the existence of several types of sites with different polarities and indicates inhomogeneous locations in the micelle with exchange times slower than about 1 nanosecond. – The results are tentatively interpreted according to the Fromherz's surfactant‐block model of the micelle.
Über die Phasenumwandlung von Monoschichten des synthetischen Phospholipids DPPA und Vergleich mit DPPC
Authors: Erbrich Uwe , Septinus Manfred , Zimmermann Herbert W.
Published: July 2012

The monolayer phase transition from the liquid‐condensed to the liquid‐expanded phase of the unusual synthetic phospholipid DPPA has been studied with the Langmuir film balance and compared with literature data of DPPC. DPPA and DPPC have different head groups. DPPA has a quarternary acridine orange (AO) residue instead of the quarternary nitrogen atom of DPPC. – The equilibrium pressure π of the phase transition of DPPA increases linearly with the transition temperature Tu: dπ/dTu = 3.1 · 10−5 N cm−1 K−1. The area change ΔFu = 6.6 · 10−16 cm2 per molecule DPPA at the phase transition is within the limits of error independent of π, in contrast to DPPC and other phospholipids. The transition entropy ΔSu = 125 J K−1 mol−1 and transition enthalpy ΔHu = 38 kJ mol−1 are large in comparison to DPPC under equal experimental conditions. The difference is related to the association of the head groups of DPPA in condensed phase. It agrees qualitatively with the thermodynamic parameters of the dissociation of dimers of AO and N‐alkyl AOs.
The Influence of a Miscibility Gap on the Reaction Behaviour of the Quasiternary System HgkCd(1‐k)TelSe(1‐l)
Authors: Leute V. , Schmidtke H. M. , Stratmann W.
Published: July 2012

Assuming a regular behaviour of the quasiternary alloy HgkCd(1‐kTelSe(1‐l) we determined the mean molar free enthalpy, the coexistence curve and the spinodal curve. From the concentration profiles taken by an electron microprobe, we calculated the reaction paths for reaction couples of CdTe and HgSe for several reaction times and annealing temperatures. The occurrence of phase separation, precipitations and regions of uphill diffusion is discussed with regard to the influence of the miscibility gap on these phenomena.
63Cu‐, 35Cl‐, and 79,81Br Nuclear Quadrupole Resonance in Copper(II) Complexes with Amino Alcohols
Authors: Okuda Tsutomu , Weiss Alarich
Published: July 2012

63Cu‐, 35Cl‐, and 79,81Br nuclear quadrupole resonances were observed in α‐ and β‐bromo(2‐diethylaminoethanolato)copper(II), α(β)‐Cu2Br2(C6H14NO)2, in chloro(2‐diethylaminoethanolato)copper(II), Cu2Cl2(C6H14NO)2, and in chloro(3‐dimethylaminopropanolato)copper(II), Cu2Cl2(C5H12NO)2, at various temperatures. The results are discussed in the frame of the Townes‐Dailey treatment, assuming hybridization of d and p atomic orbitals on Cu. – In the range 160 ≦ T/K ≦ 230 the nuclear quadrupole resonances of 63Cu in α‐Cu2Br2(C6H14NO)2 and in Cu2Cl2(C5H12NO)2 disappear. Also the 35Cl resonance in Cu2Cl2(C6H14NO)2 fades out. The former disappearance is probably due to short spin‐lattice relaxation time T1 and the latter one is caused by a phase transition. A change of signal intensity with temperature was observed for Cu2Cl2(C5H12NO)2.
The Rotation‐Inversion Spectrum of Isocyanamide, H2N — NC, in the Millimeter Wave Region
Authors: Schäfer Eckhard , Winnewisser Manfred
Published: July 2012

The rotation‐inversion spectrum of isocyanamide, H2N — NC, has been investigated in the frequency range 100 to 400 GHz. Due to the near C2v symmetry of the inverting molecule two types of dipole transitions have been observed: 1) intrasystem a‐type transitions and 2) intersystem or rotation‐inversion c‐type transitions connecting the two energy manifolds of H2N — NC belonging to the inversion states O+ and O−, respectively. The inversion splitting was found to be 0.369 cm−1, indicative of a high barrier to inversion. Pure inversion transitions are not allowed. The rotation‐inversion analysis was carried out for 240 a‐type and c‐type transitions using S‐reduced Hamiltonians according to Watson for the O+ and O− inversion states separated by the inversion splitting E1nv. The analysis yielded the following spectroscopic constants:

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plus centrifugal distortion constants. The present data and their analysis provide an excellent basis for a radioastronomical search for H2N — NC.
Influence of the Finite Nuclear Size on the Electronic and Rotational Energy of Diatomic Molecules
Authors: Tiemann E. , Knöckel H. , Schlembach J.
Published: July 2012

The difference of the Coulomb potential for a pointlike and for an extended nucleus is taken as a perturbation of the molecular energy. Correction terms, which are dependent on the mean square nuclear charge radius, are introduced for the molecular energies. The observability of the resulting isotope shift in the molecular spectra is discussed in comparison to the usual mass shift. Some examples for the pure electronic and rotational energy are presented using high precision laser and microwave experiments on Pb‐ and Tl‐compounds.
Photoelektronen‐Spektroskopie an “in situ”‐dargestellten Molekülen
Authors: Bock H.
Published: July 2012

Photoelectron spectroscopy has proven valuable for the analysis and optimization of numerous gas phase reactions in flow‐systems — especially in search for heterogeneous catalysts, which can be tested within a single day using gas mixtures of varying composition over the temperature range from 300 K to 1300 K. In academic research, this real‐time measuring probe allows one to determine — with millimol quantities and within a few hours — the temperatures for different decomposition channels. Simultaneously, main products can be characterized by the comparison of their ionization fingerprints with calculated (SCF) eigenvalue sequences making use of Koopmans theorem. If need be, the yield of a certain reaction product e. g. a short‐lived intermediate can be improved by optimizing the reaction conditions aiming at maximum intensity of the corresponding bands. In this way, many short‐lived and/or reactive molecules such as thioformaldehyde, P2 or silabenzene, which are discussed as examples, have been detected or reaction channels like vinyl azide→2H‐azirineacetonitrile visualized, PE‐spectrometers are well‐suited for on‐line connection to computers; portable instruments for laboratory use are under development.
Laser Multiphoton Ionization of Molecules and Application
Authors: Stuke M.
Published: July 2012

Examples for the application of Laser Multiphoton Ionization (MPI) are given. Experimental results on the MPI of gaseous MoF6 and WF6 by an ArF excimer laser show production of Mo2+ and W2+ ions. In the case of WF6 and for an intensity of several GWcm−2, W2+ is the dominating ion.
Thermal Excitation of H2 and D2 at Clean Metal Surfaces. Noteworthy Differences between d‐ and s‐Metals
Authors: Gentsch H. , Adamitzki W. , Ave H. , Bothe F.‐W. , Fischer H. , Rogge B.
Published: July 2012

Ad‐ and desorption measurements of hydrogen (deuterium) on clean metal surfaces under high and ultrahigh vacuum conditions by means of the capillary flow method with pressure control only by inert gauges show a small fraction of desorbing molecules in an activated state. These molecules adsorb on glass and on carbon, respectively, or are able to reduce copper‐I‐oxid. This experiment indicates two different ways for activation of hydrogen molecules in collision with hot metal surfaces: (i) the well known dissociation of molecules dominant at TS > 1100 K and (ii) new, the excitation at hydrogen (deuterium) molecules at 800 < Ts < 1100 K with activation energies of E = 0.52 (0.37) eV. The results show a significant pressure dependence of the vibration accommodation coefficient. The s‐metals Cu and Au are total ineffective in dissociation and in activation molecules, respectively. The energy for excitation (H2, D2) is in accordance with the term difference of the harmonic oscillator.
The Dipole Fluctuations of Ellipsoidal Samples
Authors: Schröer Wolfram
Published: July 2012

Starting from the calculation of the dielectric polarization of a macroscopic ellipsoid containing a fluid of polarizable dipoles surrounded by a uniform dielectric by means of electrostatics the macroscopic expressions of the dipole fluctuations are derived as a generalization of the Fröhlich relations concerning a sphere. The result holds for polar, non‐polar, and non‐polarizable molecules and includes samples of spherical, disc and needle geometry surrounded by vacuum, a metal or a medium of the same dielectric constant. The explicit evaluation of the reaction field leads independently of the surrounding medium to the same expressions which hold for samples in vacuum. The evaluation of the dipolar long‐range terms inside the sample leads to expressions of the form of the Clausius‐Mossotti relation which are independent of the boundary conditions and depend on the molecular properties and short‐range correlations only. Considering a sample containing only one molecule the theory leads to a generalization of the Onsager model for ellipsoidal molecules which agrees for small deviations of the spherical shape with the Böttcher‐Scholte model.
Diffusion Coefficients and Thermal Diffusion Factors for Five Binary Systems of Methane with the Noble Gases
Authors: Trengove R. D. , Robjohns H. L. , Dunlop Peter J.
Published: July 2012

Using two‐bulb cells and accurate thermistor bridges, diffusion coefficients and thermal diffusion factors have been measured for binary mixtures of methane with helium, neon, argon, krypton and xenon. The data and existing cross‐term virial coefficients have been employed to generate (m, 6, 8) potential functions. Several potential functions which have been reported in the literature have been tested.
Chiral Recognition of N‐Phthaloyl, N‐Tetrachlorophthaloyl, and N‐Naphthaloyl α‐Amino Acids and Their Esters on Polysaccharide‐Derived Chiral Stationary Phases
Authors: Kim Byoung‐Hyoun , Lee Sang Uck , Moon Dong Cheul
Published: July 2012

Enantiomeric separations of N‐phthaloyl (N‐PHT), N‐tetrachlorophthaloyl (N‐TCPHT), and N‐naphthaloyl (N‐NPHT) α‐amino acids and their esters were examined on several kinds of polysaccharide‐derived chiral stationary phases (CSPs). Resolution capability of CSPs was greater Chiralcel OF than the others for N‐PHT and N‐NPHT α‐amino acids and their esters. In N‐TCPHT α‐amino acids and their esters, good enantioselectivities showed Chiralcel OG for N‐TCPHT α‐amino acids, Chiralpak AD for N‐TCPHT α‐amino acid methyl esters, and Chiralcel OD for N‐TCPHT α‐amino acid ethyl esters, respectively. From the results of liquid chromatography and computational chemistry, it is concluded that l‐form is preferred and more retained with electrostatic interaction in case of interaction between N‐PHT α‐amino acid derivatives and Chiralcel OF, N‐TCPHT α‐amino acid derivatives and Chiralcel OD, and N‐NPHT α‐amino acid derivatives and Chiracel OF. On the other hand, d‐form is preferred and more retained with van der Waals interaction in case of interaction between N‐TCPHT α‐amino acid ester derivatives and Chiralcel OG and Chiralpak AD. Chirality 24:1037–1046, 2012. © 2012 Wiley Periodicals, Inc.
Comparative performance analysis of spectral estimation algorithms and computational optimization of a multispectral imaging system for print inspection
Authors: Valero Eva M. , Hu Yu , Hernández‐Andrés Javier , Eckhard Timo , Nieves Juan L. , Romero Javier , Schnitzlein Markus , Nowack Dietmar
Published: July 2012

We have analyzed the performance of simulated multispectral systems for the spectral recovery of reflectance of printer inks from camera responses, including noise. To estimate reflectance we compared the performance of four algorithms which were not comparatively tested using the same data sets before. The criteria for selection of the algorithms were robustness against noise, amount of data needed as inputs (training set, spectral responsivities) and lacking of use of dimensionality reduction techniques. Three different sensor sets and training sets were used. We analyzed the differences in the spanning of the subspaces found for the three training sets, concluding that the ink reflectances have characteristic features. The best performance was obtained using the kernel and the radial basis function neural‐net‐based algorithms for the training set composed of printer inks reflectances, whereas for the other two training sets (composed of samples from the ColorChecker DC and Vhrel's reflectances' set) the quality of the recovered samples was more uniform among the algorithms. We also have performed an optimization to choose the best sensor set for the multispectral system with a reduced number of sensors. © 2012 Wiley Periodicals, Inc. Col Res Appl, 39, 16–27, 2014
The defect in humoral immunity in patients with Nijmegen breakage syndrome is explained by defects in peripheral B lymphocyte maturation
Authors: Piątosa Barbara , van der Burg Mirjam , Siewiera Katarzyna , Pac Małgorzata , van Dongen Jacques J. M. , Langerak Anton W. , Chrzanowska Krystyna H. , Bernatowska Ewa
Published: July 2012

Patients with an immunodeficiency in the course of Nijmegen breakage syndrome (NBS) that is caused by mutations in the NBN/NBS1 gene are prone to recurrent infections and malignancies, due to a defective DNA double‐strand breaks repair mechanism. Four‐color flow cytometry was used to analyze changes in B lymphocyte subsets reflecting the most important stages of peripheral B cell maturation. It was demonstrated that the humoral immune defect observed in NBS patients was caused by reduced numbers of B lymphocytes, but also by their aberrant maturation. Reduced relative and absolute counts of naïve and memory B cells were accompanied by a significant accumulation of the natural effector B lymphocytes. The elevated proportion of IgM‐only memory and reduced proportion of IgM‐negative cells within the memory B cell pool suggests that there is class‐switch recombination defect in this population of cells in NBS patients, resulting in inadequate production of immunoglobulins. Because of the reduced T‐cell counts, the T‐cell dependent antigen response is severely impaired resulting in a lower frequency of memory B‐cells. The T‐cell independent B‐cell differentiation pathway seems less affected. The reduced IgG and IgA levels in patients with NBS are caused both by ineffective class switch, at least due to poor T cell help, and low number of memory B cells. This study illustrates that the NBN gene product nibrin plays an important role at different levels in the B‐cell system. © 2012 International Society for Advancement of Cytometry
Determination of hexaconazole in field samples of an oil palm plantation
Authors: Muhamad Halimah , Zainol Maznah , Sahid Ismail , Seman Idris Abu
Published: July 2012

In oil palm plantations, the fungicide hexaconazole is used to control Ganoderma infection that threatens to destroy or compromisethe palm. The application of hexaconazole is usually through soil drenching, trunk injection, or a combination of these two methods. It is therefore important to have a method to determine the residual amount of hexaconazole in the field such as in samples of water, soil, and leaf to monitor the use and fate of the fungicide in oil palm plantations. This study on the behaviour of hexaconazole in oil palm agro‐environment was carried out at the UKM‐MPOB Research Station, Bangi Lama, Selangor. Three experimental plots in this estate with 7‐year‐old Dura x Pisifera (DxP) palms were selected for the field trial. One plot was sprayed with hexaconazole at the manufacturer's recommended dosage, one at double the recommended dosage, and the third plot was untreated control. Hexaconazole residues in the soil, leaf, and water were determined before and after fungicide treatment. Soil samples were randomly collected from three locations at different depths (0–50 cm) and soil collected fromthe same depth were bulked together. Soil, water, and palm leaf were collected at −1 (day before treatment), 0 (day of treatment), 1, 3, 7, 14, 21, 70, 90, and 120 days after treatment. Hexaconazole was detected in soil and oil palm leaf, but was not detected in water from the nearby stream. © 2012 John Wiley & Sons, Ltd.
Simulation of the effects of complex‐formation equilibria in electrophoresis: III. Simultaneous effects of chiral selector concentration and background electrolyte pH
Authors: Svobodová Jana , Beneš Martin , Dubský Pavel , Vigh Gyula , Gaš Bohuslav
Published: July 2012

This paper describes the results of the second‐level testing of the simulation program Simul 5 Complex. We compare the published experimental results with the simulated migration behavior of the enantiomers at different pH and chiral selector concentration values and use the same optimization object function, separation selectivity, as the original papers. Simul 5 Complex proved to be a suitable tool for the prediction of the effective mobilities, separation selectivities, and migration order reversals in these pH‐dependent and CD concentration dependent enantiomer separations. In addition, by performing simulations of four different separations systems (both real and model systems), Simul 5 Complex revealed the existence of unexpected and hitherto unexplained electromigration dispersion effects that were caused by the complexation process itself and could significantly impair the quality of the separations.
Interaction of inhibition and triplets of excitatory spikes modulates the NMDA‐R‐mediated synaptic plasticity in a computational model of spike timing‐dependent plasticity
Authors: Cutsuridis Vassilis
Published: July 2012

Spike timing‐dependent plasticity (STDP) experiments have shown that a synapse is strengthened when a presynaptic spike precedes a postsynaptic one and depressed vice versa. The canonical form of STDP has been shown to have an asymmetric shape with the peak long‐term potentiation at +6 ms and the peak long‐term depression at −5 ms. Experiments in hippocampal cultures with more complex stimuli such as triplets (one presynaptic spike combined with two postsynaptic spikes or one postsynaptic spike with two presynaptic spikes) have shown that pre–post–pre spike triplets result in no change in synaptic strength, whereas post–pre–post spike triplets lead to significant potentiation. The sign and magnitude of STDP have also been experimentally hypothesized to be modulated by inhibition. Recently, a computational study showed that the asymmetrical form of STDP in the CA1 pyramidal cell dendrite when two spikes interact switches to a symmetrical one in the presence of inhibition under certain conditions. In the present study, I investigate computationally how inhibition modulates STDP in the CA1 pyramidal neuron dendrite when it is driven by triplets. The model uses calcium as the postsynaptic signaling agent for STDP and is shown to be consistent with the experimental triplet observations in the absence of inhibition: simulated pre–post–pre spike triplets result in no change in synaptic strength, whereas simulated post–pre–post spike triplets lead to significant potentiation. When inhibition is bounded by the onset and offset of the triplet stimulation, then the strength of the synapse is decreased as the strength of inhibition increases. When inhibition arrives either few milliseconds before or at the onset of the last spike in the pre–post–pre triplet stimulation, then the synapse is potentiated. Variability in the frequency of inhibition (50 vs. 100 Hz) produces no change in synaptic strength. Finally, a 5% variation in model's calcium parameters (calcium thresholds) proves that the model's performance is robust. © 2012 Wiley Periodicals, Inc.
Efficacy of platelet‐rich plasma gel and hyaluronan hydrogel as carriers of electrically polarized hydroxyapatite microgranules for accelerating bone formation
Authors: Ohba Seiko , Wang Wei , Itoh Soichiro , Takagi Yuzo , Nagai Akiko , Yamashita Kimihiro
Published: July 2012

The technology for electrical polarization and characterization of hydroxyapatite (HA) microgranules has been developed. This study aimed to examine and compare the efficacy of composites comprising electrically polarized HA (pHA) microgranules and platelet‐rich plasma (PRP) or hyaluronan (HAN) in osteoconductivity. Composites of HA microgranules with or without electrical polarization and either PRP or HAN (PRP+pHA, PRP+HA, HAN+pHA, and HAN+HA, respectively), as well as pHA and HA microgranules were implanted randomly into holes created in the medial femoral condyle or tibial tuberosity of rabbits. As a control, PRP or HAN gel alone was implanted, or the bone holes were left empty. Each group included six animals. After 6 weeks, histological examination was performed, and osteoclastic and osteoblastic cell activities were assessed by cell counting. Although PRP alone could not induce bone formation, PRP+pHA and PRP+HA composites, especially the former, activated osteogenic cells and enhanced bone formation. This effect was not prominent in the HAN+pHA and HAN+HA composites. PRP+HA composites formed a gel in which the ceramic particles were dispersed and entrapped in the fibrin network of PRP. It is assumed that these particles provide scaffolds for osteogenic cells, and when electrically polarized, can activate the cells in co‐operation with the positive effects of the PRP, resulting in enhanced bone formation. Conversely, it is conceivable that this composite gel cannot act as an accelerator for woven bone formation, because HAN with low viscoelasticity is absorbed rapidly after implantation, the hydrated network containing HA microgranules is destroyed, and the HA microgranules effuse with HAN from the bone hole. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 100A:3167–3176, 2012.
INNOVATIVE FEATURES IN POVERTY REDUCTION PROGRAMMES: AN IMPACT EVALUATION OF CHILE SOLIDARIO ON HOUSEHOLDS AND CHILDREN
Authors: Martorano Bruno , Sanfilippo Marco
Published: July 2012

The Chile Solidario programme is an innovative conditional cash transfer (CCT) in the Latin American context, aimed at addressing specifically the multidimensional nature of poverty. This paper, using data from the Panel Caracterización Socioeconómica Nacional (CASEN) Survey for the years 2001 and 2006, presents an impact evaluation of this programme. Using matching techniques to compare participants in the programme with a control group, and a difference‐in‐differences estimator, we evaluate its impact on various socioeconomic dimensions and results at the household and child level are differentiated. At the household‐level, we find that the programme has a significant impact on lifting families out of extreme poverty and that it does not have disincentive effects on labour participation. For children, we find that it has contributed to increasing participation in school for those between the ages of 6 and 15 years, and to increased enrolment with the public health services. Copyright © 2012 John Wiley & Sons, Ltd.
Pd‐Catalysed Direct Arylation Polymerisation for Synthesis of Low‐Bandgap Conjugated Polymers and Photovoltaic Performance
Authors: Chang Shu‐Wei , Waters Huw , Kettle Jeff , Kuo Zi‐Rui , Li Chun‐Han , Yu Chin‐Yang , Horie Masaki
Published: July 2012

Low‐bandgap conjugated copolymers based on a donor–acceptor structure have been synthesised via palladium‐complex catalysed direct arylation polymerisation. Initially, we report the optimisation of the synthesis of poly(cyclopentadithiophene‐alt‐benzothiadiazole) (PCPDTBT) formed between cyclopentadithiophene and dibromobenzothiadiazole units. The polymerisation condition has been optimised, which affords high‐molecular‐weight polymers of up to Mn = 70 k using N‐methylpyrrolidone as a solvent. The polymers are used to fabricate organic photovoltaic devices and the best performing PCPDTBT device exhibits a moderate improvement over devices fabricated using the related polymer via Suzuki coupling. Similar polymerisation conditions have also been applied for other monomer units.
Complete 1H and 13C NMR spectral assignments for the glycoalkaloid dehydrocommersonine
Authors: King Russell R. , Calhoun Larry A.
Published: July 2012

The normal levels and types of glycoalkaloids found in commercial varieties of potato (Solanum tuberosum) appear to present no hazard to human health. However when wild Solanum species are used in breeding endeavors, new and untested glycoalkaloids may be introduced. Recent studies of domestic crosses with a wild Solanum oplocense accession indicated that the levels of a non‐indigenous glycoalkaloid appeared associated with reduced defoliation by the Colorado potato beetle. The non‐indigenous glycoalkaloid was isolated from foliage of the wild S. oplocense accession and unambiguously characterized by high‐resolution electrospray ionization mass spectrometry and NM analysis as the glycoalkaloid dehydrocommersonine. Copyright © 2012 John Wiley & Sons, Ltd.
Multinuclear magnetic resonance studies of 2‐aryl‐1,3,4‐thiadiazoles
Authors: Gierczyk Błażej , Cegłowski Michał , Kaźmierczak Marcin , Zalas Maciej
Published: July 2012

The 1H, 13C and 15N spectra of aryl‐substituted 1,3,4‐thiadiazoles were recorded. The results obtained were correlated with Hammett coefficients. The experimental results were compared with DFT‐calculated chemical shifts. The results obtained were compared with those for 1,3,4‐oxadiazoles and 1,3,4‐selenadiazoles. Copyright © 2012 John Wiley & Sons, Ltd.