bluuebunny/crossref_metadata_2025 huggingface dataset:
Prevalence, incidence, and demographics of systemic lupus erythematosus and lupus nephritis from 2000 to 2004 among children in the US medicaid beneficiary population
Authors: Hiraki Linda T. , Feldman Candace H. , Liu Jun , Alarcón Graciela S. , Fischer Michael A. , Winkelmayer Wolfgang C. , Costenbader Karen H.
Published: July 2012

Objective

To investigate the nationwide prevalence, incidence, and sociodemographics of systemic lupus erythematosus (SLE) and lupus nephritis among children in the US Medicaid beneficiary population.

Methods

Children ages 3 years to <18 years with a diagnosis of SLE (defined as ≥3 claims with an International Classification of Diseases, Ninth Revision [ICD‐9] code of 710.0 for SLE, each >30 days apart) were identified from the US Medicaid Analytic eXtract database from 2000 to 2004. This database contains all inpatient and outpatient Medicaid claims for 47 US states and the District of Columbia. Lupus nephritis was identified from ≥2 ICD‐9 billing codes for glomerulonephritis, proteinuria, or renal failure, each recorded >30 days apart. The prevalence and incidence of SLE and lupus nephritis were calculated among Medicaid‐enrolled children overall and within sociodemographic groups.

Results

Of the 30,420,597 Medicaid‐enrolled children during these years, 2,959 were identified as having SLE. The prevalence of SLE was 9.73 (95% confidence interval [95% CI] 9.38–10.08) per 100,000 Medicaid‐enrolled children. Among the children with SLE, 84% were female, 40% were African American, 25% were Hispanic, 21% were White, and 42% resided in the South region of the US. Moreover, of the children with SLE, 1,106 (37%) had lupus nephritis, representing a prevalence of 3.64 (95% CI 3.43–3.86) per 100,000 children. The average annual incidence of SLE was 2.22 cases (95% CI 2.05–2.40) and that of lupus nephritis was 0.72 cases (95% CI 0.63–0.83) per 100,000 Medicaid enrollees per year. The prevalence and incidence rates of SLE and lupus nephritis increased with age, were higher in girls than in boys, and were higher in all non‐White racial/ethnic groups.

Conclusion

In the current study, the prevalence and incidence rates of SLE among Medicaid‐enrolled children in the US are high compared to studies in other populations. In addition, these data represent the first population‐based estimates of the prevalence and incidence of lupus nephritis in the US to date.
On Generalised Stein's Inequalites and the Inertias of Their Solutions: Application to Pencil Finite Root‐Clustering
Authors: Sari B. , Bachelier O. , Mehdi D.
Published: July 2012

This note deals with the inertia of the solutions to Generalised Stein's Inequalities (GSI) i.e. Stein's inequalities related to discrete descriptor models described through linear matrix pencils. Only strict inequalities are considered. It is shown that, under some very slight assumptions, there always exists a solution to the GSI and some properties on the inertia of this solution can be derived very easily. As an application, the finite root‐clustering of the pencil associated with a descriptor system in a union of separate discs is considered.
The Reaction of NH2‐Radicals with Electronically Excited Molecular Oxygen O2 (1Δg)
Authors: Hack W. , Kurzke H.
Published: July 2012

The reaction:

has been studied in the gas phase in an isothermal discharge flow system with He as the main carrier gas. The pressure was varied between 2.6 and 5.2 mbar and the temperature between 295 and 353 K. The O2(1Δg) was produced in a chemical reactor and its absolute concentration was measured by photoionisation. The fast reaction F + NH3 → NH2 + HF was used as the NH2‐source. The pseudo‐first order NH2‐decay and the OH and NH concentration profiles were obtained by laser induced fluorescence (LIF). This technique was found to be not sensitive enough to follow the profiles of HNO formed in this reaction. — The rate independent of temperature and pressure in the above range is:

Computer simulation together with the product measurements show that OH and HNO are the primary products of reaction (1).
A Neutron and X‐Ray Diffraction Study of the Binary Liquid Aromatic System Benzene‐Hexafluorobenzene I. The Pure Components
Authors: Bartsch E. , Bertagnolli H. , Schulz G. , Chieux P.
Published: July 2012

A series of X‐ray and neutron diffraction experiments has been performed on liquid benzene and hexafluorobenzene in order to find out whether packing effects or electrostatic interactions are the structure determining factors. The results of the experiments are reported together with the determined molecular structures in the liquid phase. The agreement with the intramolecular parameters obtained by other methods is quite good. The existing descriptions of liquid benzene via computer simulations, structure models and statistical mechanical calculations using the “RISM”‐formalism have been compared with the neutron diffraction results. It could be deduced that models assuming a preferred orientation describe the neutron experiments better than the ones with more randomly oriented molecules. The “RISM”‐theory based on a repulsive Lennard‐Jones potential and a 12 site model provides reasonable agreement.
Analysis of Thermodynamic Properties of the Hydrogen Solution in Amorphous Fe ‐ Ti Compounds
Authors: Nakamura K.
Published: July 2012

The thermodynamic properties of the hydrogen solution in amorphous Fe ‐ Ti films (Ti: 43–60%) have been studied in the pressure range from 1 to 104Pa and at temperatures from 293 to 623 K. It is shown that the observed pressure‐composition (PC) isotherms deviate positively from the Sievert's law, which is contrary to the negative deviation commonly observed in the hydrogen solution in crystalline compounds. In accordance with the positive deviation the relative partial molar enthalpies, ‐ Δ H̄, derived from the isotherms decrease with increasing the hydrogen concentration, and at very dilute concentration the value is about three times larger than that for the formation of monohydride of crystalline FeTi. These anomalously large ‐ Δ H̄ values for hydrogen dissolution in amorphous Fe‐Ti suggest that the local environment around the hydrogen atoms are quite different from that in crystalline FeTi. The relative partial molar entropy data are analyzed taking into account of the contribution from the vibrational and fromielectronic heat capacity and volume expansion terms. The results show that the number of interstitial sites available for hydrogen occupation at very dilute concentration is about five times smaller than the values observed in the V‐, Nb‐, Ta‐H systems.
Intramolecular Vibrational Energy Redistribution and Intermolecular Energy Dissipation of Polyatomic Molecules in Liquids
Authors: Kaiser W.
Published: July 2012

In small molecules the lifetime of vibrational modes critically depends upon the energy states and the anharmonic coupling of the individual molecule. Large molecules in the statistical limit exhibit very rapid intramolecular energy redistribution (≤ 1 ps). Evidence is presented for the redistribution of vibrational energy over the Vibrational manifold of the electronic ground state. A temporary internal temperature may be assigned to the excited molecules. Intermolecular energy dissipation occurs slowlier. A time constant of approximately 10 ps is observed when probed approximately 3000 cm−1 above the ground state.
Picosecond Spectroscopy and Kinetics of Metalloporphyrins
Authors: Irvine M. P. , Harrison R. J. , Strahand M. A. , Beddard G. S.
Published: July 2012

Picosecond transient Spectroscopy has been used to measure excited state lifetimes ancfrspectra of Cr, Mn, Fe, Sn and Pb meso‐tetraphenylporphyrins. Excited state spectra are typical of π,π* states, and lifetimes vary from > 20 ns in Cr(III) tetraphenylporphyrin to 8 ps in Mn(II). This contrasting behaviour in the transition metal porphyrins is interpreted as being due to charge transfer states lying above the initially excited states in Cr but below those in Mn and Fe, as recently predicted by theory. Only in Sn(IV) tetraphenylporphyrin was the singlet‐singlet absorption spectrum measurable; the excited singlet state lifetimes for the other porphyrins were < 1 ps.
Rotational State Dependence of the Predissociation Dynamics in H2O, D2O (C̃1B1 and β1A1)
Authors: Hodgson A. , Simons J. P. , Ashfold M. N. R. , Bayley J. M. , Dixon R. N.
Published: July 2012

The two photon photodissociation of H2O, D2O (C̃1B1) from individually selected J'Ka'Kc' rotational levels in the (000) vibrational level has been investigated experimentally using a line‐narrowed, tunable KrF laser. The results establish a strong dependence on the magnitude of 〈Ja'2〉1/2 ≅ Ka', both for the heterogeneous predissociation path and for the subsequent branching on the β1'A1 potential at the Renner‐Teller intersection with Ã1B1 near linearity.
Unimolecular Dissociation of Cluster Ions Following Multiphoton Ionization and Subsequent Proton Transfer Reaction
Authors: Castleman A. W. , Echt O. , Morgan S. , Di Dao P. , Stanley R. J.
Published: July 2012

Neutral clusters of ammonia comprised of up to 65 monomer units are subjected to multiphoton ionization following their production in a supersonic expansion. Resonance enhanced ionization via two‐photon absorption to the B̃(v') and C̃'(v') states in the monomer and the isotope 15NH3 is observed over a wide wavelength range, but no resonance enhancement is found for the production of the cluster ions, (NH3)n · H+ Following ionization, a proton transfer reaction ensues which leads to the production of protonated ammonia clusters. Unimolecular dissociation of the ions is studied via an electrostatic reflectron incorporated in the field‐free region of the time‐of‐flight drift tube. The rate of Unimolecular dissociation corresponding to the loss of one molecule of ammonia from cluster ions is found to increase strongly with cluster size n, while there is a decrease in rate with cluster size for the loss of two ammonia molecules.
Multiphoton Dissociation and Ionization of Molecular Bismuth
Authors: Bühler B. , Cremer C. , Janes J. , Gerber G.
Published: July 2012

The dissociation and ionization of the diatomic molecule Bi2 have been investigated in the gas phase and in a molecular beam by multiphoton processes. A result of this study is a lower threshold of E = 77000 ± 200cm−1 for the dissociative ionization of Bi2 into Bi+(3P0) and Bi(4S3/2).
Dynamics of Excitation and Reactions of Simple Molecules Induced by Laser Radiation
Authors: Giardini‐Guidoni A. , Borsella E. , Fantoni R.
Published: July 2012

The process of multiple photon excitation and dissociation of polyatomic molecules by J.R. laser radiation is reviewed. Results on molecules of different symmetry in the discrete, quasi‐continuum and continuum regions are presented and discussed.
Resonance CARS Rotational Line‐Strengths
Authors: Attal‐Trétout Brigitte , Müller‐Dethlefs Klaus
Published: July 2012

We evaluate the CARS rotational line‐strength for a CARS triple resonance with arbitrary laser polarizations and for Hund's coupling cases (a) or (b). The intermediate case (a)—(b) coupling result is given for a 2Σ+← 2Π transition corresponding to OH or NO.
Space Charge Regions in Solid Two Phase Systems and Their Conduction Contribution — II Contact Equilibrium at the Interface of Two Ionic Conductors and the Related Conductivity Effect
Authors: Maier Joachim
Published: July 2012

In the space charge regions near the contact of two ionic conductors, distribution equilibria of the mobile ions — in addition to the bulk phase equilibria — have to be taken into account resulting in charged non‐stoichiometric regions with modified electric properties. The thermodynamics of the interfacial behavior are considered and the concentration profiles for the defects in two Frenkel disordered conductors, which are taken as an example, are calculated using the standard defect chemical potentials of the materials as parameters. The conduction contributions of the space charge regions in bicrystals and dispersions which may give rise to internal and external vacancy‐interstitial (v‐i‐) junctions are discussed. — The model is checked by the help of literature data on the conductivity of β‐AgI/AgBr dispersions.
Homogeneous Condensation of Nitrogen in the Expansion Wave of a Cryogenic Shock Tube
Authors: Steinwandel J.
Published: July 2012

Condensation of nitrogen carried in helium was studied in expansion waves of a cryogenic shock tube operated at 77.4 K. Condensation onset was detected by laser light scattering in conjunction with piezoelectric pressure measurements. In contrast to most of the previous studies employing supersonic nozzles or free jet expansions, the shock tube experiments showed condensation at supersaturated states close to phase equilibrium having temperatures from 66 K to 57 K and nitrogen partial pressures from 230 torr to 45 torr. The differences in condensation onset presumably caused by the different experimental conditions such as carrier gas concentrations, cooling rates and supply temperatures cannot be explained on the basis of conventional nucleation theories. It is instead possible to relate these differences qualitatively to the molecular kinetics of nitrogen microcluster formation.
The Photoreduction of Thionine and Surfactant Thionine by Iron(II) in Anionic Micelles and Microemulsions
Authors: Mackay Raymond A. , Grätzel Michael
Published: July 2012

The rate constants for the iron(II)‐thionine and surfactant thionine system have been determined in aqueous solution, sodium dodecyl sulfate (SDS) micelles, and in a mineral oil‐in‐water microemulsion stabilized by sodium cetyl sulfate (SCS) and 1‐pentanol. The triplet lifetimes are all in the range 7–9 μs. The rate constant for electron transfer quenching of triplet thionine by iron(II) is higher in the anionic media due to a higher local Fe2+ concentration. However, the back reaction between semithionine and iron(III) is not similarly enhanced in the presence of micelles or microemulsion. The dismutation of semithionine is a little slower in microemulsion than in water, but over two orders of magnitude slower in SDS micelles. The quantum yield of thionine triplet formation, determined for surfactant thionine in SCS microemulsion, approaches unity.
A Hypercycle in a Bioreactor and in a Compartment: A Self‐Maintaining System
Authors: Buchholtz F. , Schneider F. W.
Published: July 2012

We present computer calculations of a simple hypercycle (n = 2) in a bioreactor (CSTR). Strong coupling between the two subcycles leads to a coexistence of all species, whereas weak coupling produces a selection of the faster growing subcycle in analogy to Eigen and Schuster's work at constant organisation. ‐ We simulate a self‐maintaining system by placing the hypercycle into a compartment (biological cell) which is characterized by self‐instructed opening and closing. The assumption is made that one of the two encoded proteins may also act as a membrane protein which regulates the flow of monomers through the membrane. “Ageing” of the system is simulated by an exponential decline of the coupling constant which, at the same time, will trigger a transition from a stable hypercycle (n = 2) (strong coupling) to a stable subcycle (n = 1) (result of weak coupling) with an accompanying process of closure of the compartment. The final state is an equilibrium state of the selected subcycle.
Mechanisms of Pattern Formation During Development of Higher Organisms: A Hierarchical Solution of a Complex Problem
Authors: Meinhardt Hans
Published: July 2012

Molecularly feasable interactions are discussed which enable reproducible pattern formation in a developing organism. By local autocatalysis and long ranging inhibition, a graded concentration profile of a morphogenetic substance can be generated. Under its influence, a threshold‐controlled activation of feedback loops (genes) is possible which leads to a subdivision of a developing embryo into cardinal regions. By cooperative interactions, the border between these cardinal regions obtain organizing functions for the further subdivision of the embryo. A more detailed application of this model is discussed for Drosophila. The double segment pattern is assumed to consist of the repetition of four cell states (1, 2, 3 and 4). This double segment pattern leads to the induction of the segment pattern proper. Each segment is assumed to consist of three cell states (S, A and P). A segment border is formed whenever P and S cells are juxtaposed while the A‐P border is a precondition for leg and wing formation. On the basis of this model, recently found mutations which alter the segmentation of Drosophila are explicable under the assumption that a particular mutation destroys a particular cell state (gene‐based feedback loop).
Nervous Structures with Dynamical Links
Authors: Von Der Malsburg C.
Published: July 2012

Connectivity patterns (instead of mere activity distributions) are argued to be the natural objects of fast brain dynamics. They are to be understood as a basis for self‐organization. Natural assumptions on cooperation and competition lead to a conjecture regarding the type of dynamically preferred connectivity patterns. The conjecture is supported and illustrated by dynamic simulation. Applications to sensory segmentation, to invariant pattern recognition, and to resonant projection between homeomorphic structures are discussed.
Phase Transitions and Molecular Motion in Dimethylammonium Perchlorate as Revealed by DSC, Proton and Deuteron NMR
Authors: Jurga S. , Spiess H. W.
Published: July 2012

Differential scanning calorimetry, the temperature dependence of proton and deuteron lineshapes and spin‐lattice relaxation times are reported for (CH3)2NH2ClO4 and its selectively deuterated analogue (CH3)2ND2ClO4. Our caloric data revealed the existence of three different phase modifications in dimethylammonium perchlorate, analogous to mono‐ and trimethylammonium perchlorate. An analysis of the NMR data enabled identification of the molecular motions occurring in the respective phases and to determine their activation parameters. In the low‐temperature phase III stable below 309 K there are two inequivalent dimethylammonium cations which manifest themselves by different reorientation frequencies of methyl groups about their threefold symmetry axes C3 and by reorientation of one of the two inequivalent cations about its pseudo threefold symmetry axis C'3 lying along one of the two ND bonds. In the low‐temperature range of this phase the deuteron quadrupole coupling constant indicates NH…O hydrogen bonds between the dimethylammonium and the perchlorate ions. The intermediate phase II has not been reported so far. It is stable in the temperature range 309 – 311 K, but can easily be undercooled below 290 K. In this phase one of the two cations undergoes reorientation about its diad C2 axis, whereas the other still reorients about the C'3 axis. The analysis of the large entropy change of 25.5 J/mol · K associated with the III−II transition indicates that the ClO4 ions in phase II have considerable motional freedom, presumably due to breaking of N  H… O hydrogen bonds. In phase I the dimethylammonium cations undergo quasiisotropic reorientation about their centers of gravity and translational diffusion between different sites of the tetragonal unit cell.
Thermal Conductivity, Density, Viscosity, and Prandtl‐Numbers of Di‐ and Triethylene Glycol‐Water Mixtures
Authors: Obermeier E. , Fischer S. , Bohne D.
Published: July 2012

Thermal conductivity, density and Prandtl‐Numbers of the aqueous solutions of di‐ and triethylene glycol are reported. Thermal conductivity was measured in the temperature range from −20°C to 200°C, density in the range from −10°C to 140°C and viscosity between −10°C and 80°C. In addition to the measurements Prandtl‐Numbers were calculated using values of specific heat taken from the literature.
Mass Spectrometric Determination of Reaction Enthalpies in Some Alkali/Antimony Mixtures
Authors: Scheuring Thomas , Weil Konrad G.
Published: July 2012

Equilibrium partial pressures of intermetallic molecules, of alkali atoms, and of Sb2‐ or Sb4‐molecules are measured using Knudsen effusion mass spectrometry. Equilibrium constants are calculated for the following reactions

magnified image

Reaction enthalpies for these reactions are obtained using van't Hoff plots and/or third law evaluations. In the case of the last two reactions, this evaluation was based on a highly symmetrical tentative structure model. The bond energy of an alkali atom to the Sb4 tetrahedron comes out to be more exothermic in K4Sb4 than in K2Sb4. Similarly, a sodium atom is more strongly bound to Sb4 in Na6Sb4 than to Sb in NaSb. These findings indicate a bonding alkali‐alkali interaction in the symmetric clusters.
Surface Preparation for Solid Electrolyte Aided Studies in Heterogeneous Catalysis
Authors: Ehrhardt J. J. , Häfele E. , Lintz H.‐G. , Martins A. F.
Published: July 2012

The carbon monoxide oxidation on polycrystalline platinum has been chosen as an example of solid electrolyte aided studies in heterogeneous catalysis. The results show that the mere validity of a Nernst equation, correlating the values of oxygen activity obtained under equilibrium conditions, is not sufficient to guarantee proper surface preparation. An adequate procedure of such preparation is given.
Protonic Model Potential Calculations on OH− and H2O
Authors: Goodfriend P. L.
Published: July 2012

The protonic model potential approach is extended to OH− and H2O, a two proton system. Results are compared with more detailed calculations and with experiment.
Polarized Absorption Studies on Ba[Pt1‐xPdx(CN)4]·4H2O and Ba[Pt1‐xNix(CN)4]·4H2O Mixed Crystals
Authors: Holzapfel W. , Gliemann G.
Published: July 2012

Polarized single crystal absorption spectra of Ba[Pt1‐xMx(CN)4]·4H2O with M = Pd, Ni and 0 ≤ x ≤ 1 at T = 80 K are reported. The structure of the spectra depends on the concentration x. This effect is interpreted by the variation of the relative concentration of different cluster types.
Rotational, Internal Rotational, and Translational Motion of Liquid i‐Propanol
Authors: Frech T. , Hertz H. G.
Published: July 2012

Deuteron magnetic relaxation rates of the following isotopically substituted i‐propanols (CH3)2CHOD, (CH3)2CDOH, and (CD3)2CHOH have been measured as a function of the temperature and the frequency. Thus the present investigations were performed in the dispersion range. We have attempted to interpret these relaxation rates within the framework of the Woessner theory of internal rotation. The success was not satisfactory, the quadrupole coupling constants were smaller than expected. Proton magnetic relaxation rates of the two i‐propanols (CD3)2CDOH and (CH3)2CDOD have also been measured as a function of the temperature and the frequency. Separation of intra‐ and intermolecular contributions was performed by usual isotopic dilution technique. With the intramolecular relaxation rates again difficulties to describe internal rotation appeared. The dipole‐dipole coupling constant came out too small. The intermolecular relaxation rates could be related to intermolecular configurations fairly satisfactory, although dynamical descriptions still leaves open questions.
A Molecular Dynamics Study of Liquid Chloroform
Authors: Dietz W. , Heinzinger K.
Published: July 2012

Molecular Dynamics simulations of liquid chloroform with 200 molecules in the basic cube have been performed at 295 and 325 K. The interactions were described by a rigid five‐site model with (12/6) Lennard‐Jones spheres and partial charges at the atom positions. At room temperature four simulation runs have been carried out. Three of them differ in the method with which the Coulomb forces have been truncated at the cut off distance. For the fourth one the charges have been removed in order to study their influence on the MD results. The intermolecular structure functions have been calculated from the simulation and are found in good agreement with results from an x‐ray measurement and with four out of five structure functions from neutron diffraction studies with isotopic substitution. Strong disagreement between simulation and experiment exists, however, for the six atom‐atom radial distribution functions. The origin of this discrepancy is traced back to the difference in one of the five neutron structure functions (CH37Cl3); because of the consistency of the simulation results with each other and with the other experimental data, it can be attributed to uncertainties of the neutron scattering experiment. It is also shown that the expansion of the molecular pair correlation function in terms of spherical harmonics does not converge rapidly enough for the calculation of the first five so called g‐coefficients with a sufficient degree of reliability from five neutron diffraction measurements. The self‐diffusion coefficients have been calculated for 295 and 324 K, respectively, and found in good agreement with experimental results. Rotational diffusion coefficients, the spectral densities of hindered translations and of the librations are reported. Various reorientational correlation functions have been calculated, which reproduce satisfactorily the corresponding experimental results. The MD calculations show clearly that the description of the dielectric relaxation needs a multi‐particle correlation function, whereas the far infrared absorption is due to single‐particle motion.
Studies on the n‐GaAs Photoanode in Aqueous Electrolytes. 1. Behaviour of the Photocurrent in the Presence of a Stabilizing Agent
Authors: Vanmaekelbergh D. , Gomes W. P. , Cardon F.
Published: July 2012

The competition, at the n‐GaAs/Fe2+ photoanode, between the anodic decomposition of the semiconductor, the anodic oxidation of Fe2+ ions and surface recombination was studied as a function of the light intensity, the electrode potential, and the Fe2+ concentration by means of the rotating‐ring‐disc electrode technique. The results are interpreted on the basis of a reaction scheme, in which the competing processes are linked through the intermediates of the decomposition reaction. Numerical calculations, based upon this reaction scheme, of the relationship between the stabilization ratio and the photocurrent density, between the stabilization ratio and the electrode potential, and between the photocurrent density and the electrode potential are in good agreement with the experimental data.
Measurements of the Solubility of Carbon Dioxide, Ethylene and Methane in N‐Methylpyrrolidone and in its Aqueous Solution
Authors: Wu Z. , Zeck S. , Knapp H.
Published: July 2012

Solubilities of CO2, C2H4 and CH4 in NMP and H2O‐NMP mixtures were determined at 25°C in a low pressure apparatus at atmospheric pressure. The data are used to obtain Henry and Ostwald coefficients as a function of solute‐free solvent composition. In addition densities of the H2O‐NMP system were measured with an oscillating U‐tube instrument. Experimental results are compared with literature data.
The Hydration of Aliphatic Aldehydes and Pyruvic Acid in Mixed Solvents
Authors: Knoche Wilhelm , Arturo Lopez‐Quintela M. , Weiffen Joachim
Published: July 2012

In water/dioxane mixtures and aqueous electrolyte solutions the hydration reaction has been studied. The formation of the gem‐diol of aliphatic aldehydes is associated with the binding of 3 water molecules to the carbonyl group, whereas for pyruvic acid 6 or 7 water molecules are involved in this reaction. Rate and equilibrium constants of the reactions have been determined. The hydration equilibria may be used to measure conveniently the local water activity in the aqueous and non‐aqueous regions of micellar solutions and microemulsions. The reaction rate indicates the local proton activity in these systems.
Neuere Konzepte und Ergebnisse zur Struktur von Polymernetzwerken
Authors: Burchard Walther
Published: July 2012

Trends in the research of rubber elasticity in the last decade are shortly reviewed. Scientists are presently concerned mainly with the questions, to which extent are cycles relevant for the elastic modulus, and whether a certain affineness is still a necessary requisite for a polymeric network? After a discussion of the state of theories recent experimental results are presented. These show: (i) Cycles are formed already in the pre‐gel state, and in realistic networks many of these are not elastically effective. (ii) Small angle neutron scattering from long labled chains incorporated in the network show clearly that affineness on stretching the network is not obtained even for long chains of about 3000 monomer units in length. (iii) Deuterium NMR from stretched rubbers in the dry as well as in the swollen state disclose segmental orientation which is more pronounced for segments near a junction point. Again this behavior is not predicted by current theories.
The Polymerization of Diacetylenes on Solid Surfaces
Authors: Klauck W. , Breuer H. D.
Published: July 2012

The influence of solid surfaces on the polymerization of diacetylenes has been studied using 3,5‐octadiyn‐1,8‐diol as a model compound. The first molecular layers on polar surfaces are adsorbed by hydrogen bonds. Their relative orientation hinders the polymerization of these molecules. Subsequent layers can be polymerized by UV radiation. After the unreacted monomer has been extracted a highly stable polymer film remains on the surface.
Morphological Stability in the Course of Solid State Reactions: The System Fe3O4 ‐ Mn3O4 ‐ Cr2O3
Authors: Backhaus‐Ricouit M. , Schmalzried H.
Published: July 2012

We have investigated experimentally and theoretically the problem of morphological stability of interfaces in a nonequilibrium two‐phase ternary system while it equilibrates. The system chosen for this study was Fe3O4 ‐ Mn3O4 ‐ Cr2O3 at T = 1400 °C. Depending on the spinel reactant and the sesquioxide reactant, the initially planar interface is either unchanged, or develops nonplanar morphologies of different kind. The theoretical analysis starts with the independent flux equations and the appropriate boundary conditions and investigates whether or not small perturbations of the planar interface will grow or decay in the course of time. A critical parameter can be defined which is negative for stable and positive for unstable interfaces. This parameter is a complicated function of all the transport coefficients, the starting compositions and the chemical potentials of the components in both phases and can in principle be calculated, as long as local equilibrium prevails during the reaction.
A Neutron and X‐Ray Diffraction Study of the Binary Liquid Aromatic System Benzene‐Hexafluorobenzene II. The Mixtures
Authors: Bartsch E. , Bertagnolli H. , Chieux P.
Published: July 2012

A series of X‐ray and neutron diffraction experiments has been performed on liquid benzene, hexafluorobenzene and their liquid mixtures in order to find out whether packing effects or electrostatic interactions are the structure determining factors. The results for the mixtures are reported together with a qualitative interpretation of the experimental data. By combined analysis of the X‐ray and neutron diffraction experiments it could be proved that a reorientation takes place from a L‐type pair geometry in the pure components to a nearly parallel alignment of the molecules in a 1:1 complex. In a second approach a new quantity ‐ a so‐called excess structure factor ‐ was defined, the analysis of which confirmed the deduced change of orientation. With a stacking distance of 3.7 Å and a separation of 7.6 Å between two consecutive hexafluorobenzene molecules the structure of the equimolar mixture in the liquid phase very closely ressembles the one obtained for the solid phase. It can be concluded that the quadrupolar interaction is the structure determining factor in the investigated liquid aromatic systems.
Excess Properties of Liquid Cyclohexane/Hydrocarbon Mixtures II. Excess Gibbs Energy Determined from Total Vapour Pressure Data
Authors: Wagner H. , Lichtenthaler R. N.
Published: July 2012

Results of the composition dependence of the molar excess Gibbs energy GE determined from total vapour pressure data of mixtures of cyclohexane with saturated and unsaturated hydrocarbons at 298.15 and 313.15 K are reported. The results of the mixtures with the saturated hydrocarbons show a systematic behaviour of GE with respect to the chain length and the degree of branching of the molecules of the substances mixed. The results of the mixtures with unsaturated components extend the systematics taking into account the number and the location of multiple bonds within the molecules.
Electrochemical and Thermodynamic Studies on Copper‐Silver‐Selenium System
Authors: Mostafa S. N. , Selim S. R.
Published: July 2012

With the help of coulometric titrations, using the solid state galvanic cell Ag/AgI/(Cu,Ag)2+δSe/C, in the temperature region between 200 and 350°C, the following parameters: Point defect concentrations, effective mass of electrons and holes, width of band gap and the partial molar thermodynamic quantities of dissolution of one mole of silver in the mixed selenide were determined as a function of the metal/selenium ratio. The change of the thermodynamic quantities with the change of the stoichiometric composition can be explained by varying contributions of electrons and electron‐holes, depending on the fact whether the electrons, which are brought into the mixed selenide by the dissolution of silver, go into the conduction band (excess of metal) or. by destruction of electron‐holes into the valence band (deficit of metal). The band gap energy in the Ag1.188Cu0.812Se is 0.12 eV.
Scaled‐Particle Theory for Adsorbed Hard‐Core Molecules
Authors: Joshi Y. P. , Tildesley D. J.
Published: July 2012

Molecular fluids such as N2 and CS2 adsorb on a graphite surface to form a variety of phases at temperatures below 200 K and sub‐monolayer coverages. To a first approximation, we can model the thermodynamic properties of the adsorbed fluid in terms of a two dimensional fluid of hard‐core molecules. However these systems are not strictly two dimensional, the molecules vibrate in the plane perpendicular to the surface and tilt at an angle to the surface. The tilt of the molecules can be included by projecting the three dimensional adsorbate onto the surface plane. For realistic fluids of linear molecules the two dimensional analogue is a mixture of hard convex molecules with a continuous distribution of bondlengths. This distribution is controlled by the distribution of tilt angles in the three dimensional precursor. In this paper we develop a scaled particle theory for this polydispersed mixture which predicts pressures and chemical potentials which are thermodynamically consistent. This hard‐core reference system can be used in perturbation theories to predict the spreading pressure and adsorption isotherms of realistic molecular fluids adsorbed on graphite.
Substrate Dependence of the 2D Gas‐Solid Phase Transition in Adsorbed Xenon Layers
Authors: Eder S. , Markert K. , Jablonski A. , Wandelt K.
Published: July 2012

Coexisting 2D gas and 2D solid phases of adsorbed xenon can be distinguished by means of UV photoelectron spectroscopy. This is used to demonstrate the influence of the xenon/metal interaction strength on the 2D gas ⟷ 2D solid Xe phase equilibrium on Cu(111), Ag(111) and Ru(001).
Calculation of Interactions Between Adsorbates on Transition Metal Surfaces
Authors: Dreyssé H. , Tománek D. , Bennemann K. H.
Published: July 2012

We present an electronic calculation of two‐ and three‐body interactions in chemisorbed layers. The interaction energies are obtained in a self‐consistent way within the tight‐binding formalism which includes electron correlations and interatomic pairwise repulsion terms. Numerical results for Re2 and Re3 on W(110) are compared with recent experimental data.
Halogen Overlayer Structures on Fe(110)
Authors: Mueller D. , Rhodin T. N. , Dowben P. A.
Published: July 2012

The overlayer structures formed with halogen adsorption on an Fe(110) surface have been investigated using LEED. The LEED patterns are described using variable, non‐coincident nets of halogen adatoms. The adlayer nets rotate and contract with increasing halogen coverage. The structural changes within the adlayer are consistent with an adatom model developed for the Cl2/Br2/I2 Fe(110) systems. The internuclear spacings and geometry of the halogen overlayers on Fe(110) are shown to be consistent with previous work on Fe(110).
Neutron Scattering Experiments with a Binary Critical Mixture for the Determination of the Critical Exponent ζ
Authors: Schwahn D. , Belkoura L. , Woermann D.
Published: July 2012

Small angle neutron scattering experiments are carried out with an isobutyric acid (COOD)/deuterium oxide mixture of critical composition. The scattering patterns are measured at small temperature differences (T ‐ Tc) ≦ 1.0 K above the critical temperature Tc. In his temperature range and for scattering vectors larger than 0.03 Å−1 the critical scattering was found to be independent of temperaure. From these data the experimental correlation scaling function gexp(x) is constructed for values of the scaling variable x in the range 4 < x < 540. The Fisher‐Langer approximation of the correlation scaling function and its asymptotic form for large values of x are fitted to gexp(x). In this way a value of the critical exponent η of η = 0.039 ± 0.009 is obtained. It is based on the analysis of the experimental correlation scaling function composed of five scattering patterns obtained at five different temperature differences (ΔT ≤ 1.0 K). The analysis of 4 individual scattering patterns (ΔT ≤ 0.08 K) gives η = 0.037 ± 0.006.
Observation of Rates of Sorption and Diffusion in Zeolite Crystals at Constant Temperature and Pressure
Authors: Prinz D. , Riekert L.
Published: July 2012

An experimental arrangement is described which permits to observe mass transfer in synthetic zeolite crystals of small size by gravimetry without interference from external mass transfer and heat transfer resistance.—Experimental results concerning the kinetics of sorption of 3‐methyl‐pentane, benzene and p‐xylene in pentasil‐zeolite are reported. These results indicate that not only diffusion but also other intracrystalline relaxation phenomena can influence the rate of sorption into zeolites.
Inelastic Neutron Scattering Studies of Water in Natural Zeolites
Authors: Fuess H. , Stuckenschmidt E. , Schweiss B. P.
Published: July 2012

Results on the motion of water molecules in six natural zeolites (natrolite, phillipsite, harmotome, heulandite, stilbite and chabazite) from incoherent inelastic neutron scattering are presented. The spectra for five zeolite samples exhibit broad maxima and few resolved peaks. Only for natrolite with water molecules tightly bound to the alumosilicate framework a spectrum with well‐resolved peaks is observed. A detailed interpretation is attempted for the Ba‐zeolite harmotome where data were recorded at various temperatures and different amount of water.—Differential scanning calorimetry gave a broad dehydration peak for chabazite (T = 443 K) and a sharp single peak for natrolite (T = 633 K), whereas three maxima (T = 433, 523 and 673 K) were observed for harmotome.
Optische Aufheller als Laserfarbstoffe
Authors: Rinke Monika , Güsten Hans
Published: July 2012

The singlet absorption, triplet absorption and the absolute fluorescence spectra together with the fluorescence quantum yields and fluorescence decay times as well as the laser performance (tuning range, conversion efficiency, photochemical stability) of nine fluorescent brightening agents have been measured in ethanol at room temperature. High fluorescence quantum yields of over 0.75 with short fluorescence decay times of well under one nanosecond have been obtained. With the exception of two fluorescent brightening agents the tuning ranges are in the violet‐blue region between 415 and 447 nm. The conversion efficiencies range from 1 to 15%. The photochemical stability of the optical brighteners in solution with energy half‐life values between 2 × 104 and 105 J/l, corresponding to average lifetimes of 75 to 200 photons per molecule, is poor in comparison to their known photochemical stability in the adsorbed state.
Experimental Evaluation of the B‐DNA → Z‐DNA Transition: Energetics of a Reversible, Thermally Induced Helix/Helix Transition of Poly dG‐m5dC in Physiological Mg2± Concentrations
Authors: Klump H.
Published: July 2012

UV spectroscopic studies show that poly dG‐m5dC above 2 mM Mg2+ undergoes a reversible, thermally induced helix/helix transition from the B‐ to the Z‐DNA conformation. The observed cooperativity of the transition suggested to monitor the enthalpy change of the interconversion by means of an adiabatic scanning microcalorimeter. The transition is endothermic, the transition temperature at half conversion is 59°C (10 mM Mg2+), the transition enthalpy is 4.77 kJ per mole base pairs, the transition entropy amounts to 14.35 J · mol−1 K−1. From the slope of the absorbance/temperature scan at 280 nm as well as from the plot of the degree of transition/temperature ΔHvH is calculated (1078 kJ/mol). The ratio of the ΔHvH and the true enthalpy obtained by calorimetry gives the number of base pairs (226) which undergo the transition simultaneously. The Gibbs enthalpy of the B→Z transition yields 0.5 kJ per mole base pairs.
The System Water—Carbon Dioxide—Sodium Chloride to 773 K and 300 MPa
Authors: Gehrig M. , Lentz H. , Franck E. U.
Published: July 2012

Experimental results are reported for fluid‐fluid phase equilibria of the ternary system H2OCO2NaCl. Measurements were extended to 773 K and pressures to 300 MPa. A “synthetic” method was used: Known quantities of the three components were filled into an autoclave at room temperature. The autoclave with a sapphire window and variable volume is described. Transition points to homogeneous one‐phase conditions could be determined from recordedp—T‐curves at constant volumes and from visual observation. From the transition pointsp—T‐curves on the three‐dimensional phase equilibrium boundary surface at constant compositions, “isopleths”, were obtained. Data for 20 isopleths with CO2‐concentrations between 0.2 and 85 mol% and with 6 weight YO of NaCl are presented together with a few additional results for higher salt concentrations. Molar volumes were measured at the phase boundary surface and within the one‐phase region. Excess molar volumes are given. In comparison with the binary H2O‐CO2system, the addition of NaCl shifts the range of partial immiscibility to higher temperatures by up to 100 K; for example from 573 to 673 K at 100 MPa for 48 mol% CO2. Results are in agreement with earlier data of Takenouchi and Kennedy. Considerations of the ternary phase diagram H2OCO2NaCl within a wide range of conditions are given.
Bestimmung der Geschwindigkeitskonstanten der Reaktion von 1CH2 mit Fluor‐ und Chlorethen
Authors: Simon F. G. , Heydtmann H.
Published: July 2012

The rate constants for the addition of 1CH2 to fluoroethene and chloroethene have been determined using the known rate constant for the reaction of 1CH2 with ketene. The experiments yielded the results
1H‐NMR Relaxation Study of Water in Binary Solvent Mixtures in the Absence and Presence of Electrolytes
Authors: Merboldt Klaus‐Dietmar , Frahm Jens
Published: July 2012

NMR spin‐lattice (T1) and spin‐spin (T2) relaxation times are reported for water protons in aqueous solutions of deuterated HMPT, pyridine, and DMF in the absence and presence of electrolytes of different charge types. Measurements have been performed for a wide range of temperatures and for three different magnetic field strengths corresponding to 15, 60 and 270 MHz. Neglecting contributions from intermolecular interactions, water proton relaxation is described using a modified BPP‐theory that assumes an asymmetric distribution of correlation times. In binary solvent mixtures both shape and width of the distribution are shown to depend on the type of the solvent and its composition. The distribution parameters correlate with the strength of interaction between water and solvent molecules. In a similar way, the addition of electrolytes affects the distribution width as well as its dependence on solvent composition.
A Microscope‐Spectrometric Method for Determining Small Fe3+‐Concentrations Due to Fe3+‐Bearing Defects in Fayalite
Authors: Cemic L. , Grammenopoulou‐Bilal St. , Langer K.
Published: July 2012

A microscope‐spectrometric method with areal resolution of 3 μm Ø is developed to determine the small Fe3+‐concentrations in fayalite, caused by the formation of (2Fe*M(1,2) + V″M(1,2)) and (Fe*M(1,2)Fe′Si) majority defects as a function fO2 and T. From polarized spectra E‖X(‖b), E‖Y(‖c), E‖‖Z(‖a) in the UV, i.e. in the range of O‐Fe2+ and O‐Fe3+ charge‐transfer transitions, on oriented fayalite crystals grown at 800°C/10 kb and at various fO2, calibration curves were obtained αX,26500 = 107191 · X + 647.0 (r = 0.999), αY,26500 = 69468 · X + 505.5 (r = 0.93), and αZ,28000 = 165804 · X + 640.6 (r = 0.993). Here, αX,Y,Z,ṽ are the linear absorption coefficients and X is the site fraction, X = [FeM(1,2)3+]+[Fe3+M(1,2)Fe3+Si], calculated according to Nakamura and Schmalzried [1] for the fO2 conditions applied. The applicability of the calibration is shown by determining, by microscopespectrometry, a Fe3+ ‐concentration profile along Y(‖c) in a fayalite single crystal grown at fO′2 (ca. 1200°C/4.0·10−9 atm O2, ca. FMQ) and reheated at another oxygen fugacity fO″2(895°C/9.7 · 10−18 atm O2, ca. WI).
Debye‐Hückel‐Type Relaxation Processes in Solid Electrolytes: Complex Conductivity Arcs and Broad Quasielastic Neutron Scattering
Authors: Funke K.
Published: July 2012

Correlated forward‐backward hopping processes are a common feature in solid electrolytes. A simple Debye‐Hückel‐type model is constructed to show how “trial‐and‐error” hops are being caused by the electrostatic interaction between the mobile charge carriers. The forward‐backward hopping processes are shown to be responsible for a number of well‐known experimental findings which have so far not been understood microscopically. These include the occurrence of almost circular arcs in the complex impedance and conductivity planes, with centers displaced below the real axes, and the power‐law behavior of the frequency dependent conductivity. Both effects have often been called “universal dielectric response”. The model also yields quasielastic contributions to the energy resolved neutron scattering spectra which are much broader than the quasielastic lines due to translational jump diffusion.
Diffusion Processes and Interphase Boundary Morphology in Ternary Metal‐Ceramic Systems
Authors: Backhaus‐Ricoult M.
Published: July 2012

Diffusion processes, product formation, and interphase boundary morphology are discussed in terms of thermodynamics and linear transport theory for isothermal diffusion annealed ternary metal‐ceramic systems, which have not reached equilibrium. Some experimental results are presented for typical systems like Ni‐Al2O3, Ni‐MgO and Nb‐Al2O3 and compared with theoretical calculations. It is shown how the starting composition of the ceramic or that of the metal phase, as well as the oxygen activity can influence the chemical compositions at the interphase boundary.
Structural Collapse or Expansion of the Hydro‐Sodalite Series Na8[AlSiO4]6(OH)2·nH2O and Na6[AlSiO4]6·nH2O Upon Dehydratation
Authors: Felsche J. , Luger S.
Published: July 2012

The two end‐member series of hydro‐sodalites show different structural expansion characteristics during dehydratation at elevated temperatures (300–900 K). The anomalous expansion in cell volume which is observed for series Na6[AlSiO4]6 · nH2O upon loss of 0 < n ≤ 8 H2O is correlated to the destruction of the significant hydrogen bonding system between non‐framework and framework oxygen atoms of the corresponding sodalite structures. The contraction of the unit cell of the basic sodalites Na8[AlSiO4]6(OH)2 · nH2O upon loss of 0 < n ≤ 4 H2O, however, is well understood in terms of space filling of the non‐framework constituents and some special stereochemical features amongst sodium, oxygen and hydrogen atoms.