Magnetic resonance study on lamellar phases of ammonium perfluorooctanoate

The aggregation properties of ammonium perfluorooctanoate (NH₄-PFO) in concentrated aqueous phases have been investigated by magnetic resonance techniques and have been compared with the aggregation properties in dilute solutions. Magnetic resonance methods indicated that NH₄-PFO—water systems with surfactant concentrations below 45% (w/w) behaved as isotropic purely micellar solutions in the temperature range 285–340 K. For higher concentrations the system exhibited a rather complex structure, having both isotropic and anisotropic components. The nematic nature of the anisotropic fraction was demonstrated by ¹⁹F NMR studies. The ¹⁹F NMR and EPR of nitroxides (TempTMA⁺, 5- and 16-DXSA) inserted as paramagnetic probes into the concentrated NH₄-PFO—water systems allowed us to establish that the lamellar phase could be mechanically oriented between quartz slides. The EPR investigation also gave details concerning the dynamics of both the oriented and non-oriented structures.     

Measurements and Utilization of Consistent Gibbs Energies of Transfer of Single Ions: Towards a Unified Redox Potential Scale for All Solvents

Utilizing the “ideal” ionic liquid salt bridge to measure Gibbs energies of transfer of silver ions between the solvents water, acetonitrile, propylene carbonate and dimethylformamide results in a consistent data set with a precision of 0.6 kJ mol⁻¹ over 87 measurements in 10 half-cells. This forms the basis for a coherent experimental thermodynamic framework of ion solvation chemistry. In addition, we define the solvent independent - and the values that account for the electronating potential of any redox system similar to the value of a medium that accounts for its protonating potential. This scale is thermodynamically well-defined enabling a straightforward comparison of the redox potentials (reducities) of all media with respect to the aqueous redox potential scale, hence unifying all conventional solvents′ redox potential scales. Thus, using the Gibbs energy of transfer of the silver ion published herein, one can convert and unify all hitherto published redox potentials measured, for example, against ferrocene, to the scale.     

Generation and capture of methyl(vinyl)silanone

Methyl(vinyl)dichlorosilane reacts with DMSO in the presence of hexamethyldisiloxane to give the corresponding linear oligosiloxanes of the general formula Me₃Si(OSiMeVin) _n OSiMe₃ (n=1–6) as well as MeSi(OSiMe₃)₃ and Me₃Si(MeOSiVin) _m OSi(OSiMe₃)(Me)OSiMe₃ (m=1–2). The same reaction in the presence of chlorotrimethylsilane results in oligomers of the general formula Me₃Si(OSiMeVin) _n Cl (n=1–3). A possible scheme of their formation is discussed. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1614–1616, August, 1998.     

Diffusion of macromolecular solutions in the boundary layer

Summary This paper concerns the study of a diffusion layer of macromolecular solutions annularly injected in a cylindric pipe in turbulent flow. The study includes firstly the analysis of the longitudinal and transversal projections of the concentration gradient, secondly the study of the state of turbulence in the diffusion layer.The concentrations are determined by the measurement of the concentration salt (salt was added to the injected solution). A mathematical model of the development of concentration is proposed.The turbulent state of diffusion layer has been studied with Laser-Doppler-Anemometry. An analysis of Eulerian autocorrelation and the power spectral density has been done.

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Zusammenfassung Es werden Ergebnisse über die turbulente Diffusionsschicht von nicht-newtonschen Flüssigkeiten (PÄO) mitgeteilt, die an der Wand eines kreiszylindrischen Rohrs injiziert werden. Diese Untersuchungen betreffen die Analyse der Längs- und Querkomponenten des Konzentrationsgradienten in der Diffusionsschicht und im Turbulenzfeld.Die Konzentrationen werden mit Hilfe von Salz (NaCl) gemessen, das der injizierten Polymerlösung beigefügt worden ist. Ein mathematisches Modell für die Konzentrationsverteilung wird vorgeschlagen.Der Turbulenzzustand der Diffusionsschicht wird mit Hilfe der Laser-Doppler-Anemometrie untersucht. Die Eulersche Autokorrelation und das Intensitätsspektrum werden analysiert.

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Nomenclature c polymer concentration (wppm) - c ₀ wall value ofc - c _i value ofc at the slot - D diameter of the pipe - e slot thickness - L ₀ distance from the slot at which the wall concentration drops toe ^–1of its original value - m distance in meter from the slot - U means freestream velocity - u _i injection velocity - x distance from the slot - y normal distance from the surface - boundary layer thickness - characteristic height of the diffusion, i. e. the value ofy at whichc/c ₀ = 0.5 With 4 figures     

Excitation functions of the analyzing power in elastic proton-proton scattering from 0.45 to 2.5 GeV

Excitation functions A_N(p_lab,_c.m.) of the analyzing power in elastic proton-proton scattering have been measured in an internal target experiment at the Cooler Synchrotron COSY with an unpolarized proton beam and a polarized atomic hydrogen target. Data were taken continuously during the acceleration and deceleration for proton kinetic energies T_lab (momenta p_lab) between 0.45 and 2.5 GeV (1.0 and 3.3 GeV/c) and scattering angles 30 ^° _c.m. 90^°. The results provide excitation functions and angular distributions of high precision and internal consistency. The data can be used as calibration standard between 0.45 and 2.5 GeV. They have significant impact on phase shift solutions, in particular on the spin triplet phase shifts between 1.0 and 1.8 GeV.     

Measurement of the analyzing power in p-->d-->(p p)n with a fast forward 1S0 proton pair

A measurement of the analyzing power A(y) of the p-->d--> (p p) + n reaction was carried out at the ANKE spectrometer at COSY at beam energies of 0.5 and 0.8 GeV by detection of a fast forward proton pair of small excitation energy E(pp) < 3 MeV. The S-wave dominance in the fast diproton is experimentally demonstrated in this reaction. While at T(p) = 0.8 GeV the measured analyzing power almost vanishes, it rises to nearly unity at T(p) = 0.5 GeV for neutrons emitted at theta(c.m.)(n) = 167 degrees. The results are compared with a model taking into account one-nucleon exchange, single scattering, and Delta(1232) excitation in the intermediate state. The model describes fairly well the unpolarized cross section obtained earlier and the analyzing power at 0.8 GeV; it fails to reproduce A(y) at 0.5 GeV.     

Acetoxy(fluoro)(phenyl)silanes C6H5Si(OCOCH3) n F3−n

Russian Journal of General Chemistry -     

Multiplicities of secondary hadrons produced in vp and vp charged current interactions

In an experiment with the hydrogen bubble chamber BEBC at CERN multiplicities of hadrons produced in νp and $\text{v}\text{p}$ interactions have been investigated. Results are presented on the multiplicities of charged hadrons and neutral pions, forward and backward multiplicities of charged hadrons and correlations between forward and backward multiplicities. Comparisons are made with hadronic reactions and e⁺e^? annihilation. In the framework of the quark-parton model the data imply similar charged multiplicities for the fragments of a u- and a d-quark, and a larger multiplicities for the fragments of a uu- than for a ud-diquark. The correlation data suggest independent fragmentation of the quark and diquark for hadronic masses above ～ 7 GeV and local charge compensation within an event.     

Ultra-fine grained Nd–Fe–B by high pressure reactive milling and desorption

This paper reports on the grain refinement in dynamic hydrogenation disproportionation desorption and recombination (d-HDDR) processed Nd-rich Nd₂Fe₁₄B and stoichiometric Nd₂Fe₁₄B powders using high pressure reactive milling (HPRM) followed by a subsequent desorption and recombination. In contrast to the dynamic-HDDR processed anisotropic powder with a grain size of the Nd₂Fe₁₄B phase of 300 nm, the new approach yields a further reduction of the Nd₂Fe₁₄B₁ grain size to less than 70 nm. Nd-rich Nd₂Fe₁₄B powder produced by HPRM and subsequent desorption exhibits a coercivity μ_0iH_c=1.35 T and a remanence of 0.80 T. In the stoichiometric material, the reduction of the Nd-content leads to an increase in remanence to 0.85 T. Additionally, it is demonstrated that highly anisotropic powders can also be obtained by dynamic-HDDR processing of stoichiometric Nd₂Fe₁₄B powders.