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71.
72.
Professor George W. Gray 《Liquid crystals》2013,40(5):751-752
Abstract Optical microscopy in mixtures of di-octylazoxybenzene (8AB) and di-nonylazoxybenzene (9AB) reveals that a smectic A-nematic-isotropic triple point occurs at 71·5±0·5°C and 38±2wt% 8AB. Although this concentration induced triple point is different from the pressure induced triple point known to exist in pure 9AB at elevated pressure, analysis of the data from both the mixing and pressure experiments reveals that the phase transition surfaces in temperature-pressure-concentration space for this system are nearly planar. 相似文献
73.
Abstract Deuterium quadrupole echo spectroscopy has been used to probe the orientational behaviour and dynamics of CDCl3 molecules in ethylcellulose/chloroform chiral nematic phases. The 2H spectra of both left-handed and right-handed mesophases, formed by ethylcellulose with degrees of substitution of 2·3 and 3·0 respectively, were examined as functions of temperature and concentration. The observed quadrupolar splittings are relatively large and the magnitudes of the order parameters of the solvent molecules show little correlation with the handedness of the chiral phases. However, the 2H line shapes of these two types of chiral phase exhibit rather different temperature dependences. Spectral simulations show that the observed line shapes and their temperature variations are mainly determined by diffusion of CDCl3 molecules along the pitch axis. The effects of centrifugation on the 2H spectra are also described. 相似文献
74.
Liam J. R. McGeachie Cameron L. Carpenter-Warren David B. Cordes Michael Bühl Steven J. Gray Guoxiong Hua Alexandra M. Z. Slawin J. Derek Woollins 《无机化学与普通化学杂志》2020,646(22):1795-1798
An improved route to d-block and main group NSO complexes is presented including the synthesis of the first antimony(V) complexes, (Ar3Sb(NSO)2), and copper examples [CuBipy(PPh3)NSO]. The structures of eight complexes are reported. The observed variation in M–N–S bond angles is due to the combination of orbital overlap (ligand-to-metal bonding) and the degree of ionicity of the bonding. 相似文献
75.
76.
The angular correlation parameters G L involved in the dielectric and Kerr constants are written as averages over the angular pair correlation function. A perturbation theory for these parameters is developed, based on the expansion of Gubbins and Gray for the angular pair correlation function. Numerical calculations are presented showing the influence of polar and quadrupolar forces on these parameters. 相似文献
77.
The electronic spectrum of the nitridoosmate(VIII) ion, OsO3N-, has been measured at liquid helium temperatures for thin films of the n-tetrabutyl-ammonium salt and for oriented, doped LiClO4. 3H2O single crystals. Four structured band systems, all individually composed of superimposed A 1 ← A 1 and E←A 1 transitions, are observed at energies comparable to those of the two lowest 1 T 2←1 A 1 transitions of OsO4. Prominent vibronic structure assigned to ν(Os-N) is observed for all of the bands. The bands are assigned to transitions to completely spin-orbit mixed states. The highest filled orbitals of OsO3N- are oxygen-localized and π non-bonding. The nitrido ligand appears to ‘dominate’ the π-bonding in the ion. 相似文献
78.
The conditions required for the accurate measurement of the sulfur content of cellulose nanocrystals (CNCs) by conductometric titration are discussed. CNCs from sulfuric acid hydrolysis are electrostatically stabilized in aqueous suspension due to the introduction of charged sulfate ester groups onto the surface of the crystallites during reaction. The sulfur content thus largely reflects the surface charge of the crystals, and is crucial to the characterization and understanding of material properties. Conductometric titration is commonly used to quantify the sulfur content of CNCs, however, the exhaustive removal of free acid by dialysis and the necessity, type, quantity and duration of ion-exchange resin treatments are not always consistent. Here we explore the standard conditions of dialysis, ion-exchange, and the reproducibility of titration results. Extensive dialysis is found to be effective in the removal of free acid, but similar results are also achieved in shorter times and with less water using membrane ultrafiltration. It is also shown that the conditions of ion-exchange most commonly employed in the literature can lead to inaccurate sulfur contents. Finally, good agreement is obtained between the sulfur contents of different CNC batches prepared using the same hydrolysis conditions, and from titration and elemental analysis when thoroughly purified, well-dispersed samples, and appropriate resin conditions are used. 相似文献
79.
Andreev VA Banks TI Case TA Chitwood DB Clayton SM Crowe KM Deutsch J Egger J Freedman SJ Ganzha VA Gorringe T Gray FE Hertzog DW Hildebrandt M Kammel P Kiburg B Knaack S Kravtsov PA Krivshich AG Lauss B Lynch KL Maev EM Maev OE Mulhauser F Ozben CS Petitjean C Petrov GE Prieels R Schapkin GN Semenchuk GG Soroka MA Tishchenko V Vasilyev AA Vorobyov AA Vznuzdaev ME Winter P;MuCap Collaboration 《Physical review letters》2007,99(3):032002
The rate of nuclear muon capture by the proton has been measured using a new technique based on a time projection chamber operating in ultraclean, deuterium-depleted hydrogen gas, which is key to avoiding uncertainties from muonic molecule formation. The capture rate from the hyperfine singlet ground state of the microp atom was obtained from the difference between the micro(-) disappearance rate in hydrogen and the world average for the micro(+) decay rate, yielding Lambda(S)=725.0+/-17.4 s(-1), from which the induced pseudoscalar coupling of the nucleon, g(P)(q(2)=-0.88m(2)(micro))=7.3+/-1.1, is extracted. 相似文献
80.
Li Q Gray KE Zheng H Claus H Rosenkranz S Ancona SN Osborn R Mitchell JF Chen Y Lynn JW 《Physical review letters》2007,98(16):167201
Contrary to conventional wisdom, our purified La 2-2x Sr 1+2x Mn2O7 crystals exhibit CE-type orbital and charge order as the low-temperature ground state for a hole doping level h=0.5. For small deviations from h=0.5, the high-temperature CE phase is replaced at low temperatures by an A-type antiferromagnet without coexistence. Larger deviations result in a lack of CE order at any temperature. Thus, small inhomogeneities in cation or oxygen composition could explain why others commonly see this reentrance with coexistence. 相似文献