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21.
A Weibel R Bouchet S L P Savin A V Chadwick P E Lippens M Womes P Knauth 《Chemphyschem》2006,7(11):2377-2383
Tin-doped anatase TiO(2) nanopowders and nanoceramics with particle sizes between 12 and 30 nm are investigated by X-ray absorption fine-structure (EXAFS) and M?ssbauer spectroscopies. Furthermore, ab initio calculations based on the density functional theory are performed to analyze changes in the electronic structure due to Sn doping. The three approaches consistently show that Sn is dissolved on substitutional bulk sites with a slight increase of the bond lengths of the inner coordination shells. The Debye-Waller factors show that the nanocrystallites are highly ordered. There is no indication of defect states or bandgap changes with Sn doping. 相似文献
22.
principally unimodular (PU) if every principal submatrix has determinant 0 or ±1. Let A be a symmetric (0, 1)-matrix, with a zero diagonal. A PU-orientation of A is a skew-symmetric signing of A that is PU. If A′ is a PU-orientation of A, then, by a certain decomposition of A, we can construct every PU-orientation of A from A′. This construction is based on the fact that the PU-orientations of indecomposable matrices are unique up to negation and
multiplication of certain rows and corresponding columns by −1. This generalizes the well-known result of Camion, that if
a (0, 1)-matrix can be signed to be totally unimodular then the signing is unique up to multiplying certain rows and columns
by −1. Camion's result is an easy but crucial step in proving Tutte's famous excluded minor characterization of totally unimodular
matrices.
Received: May 17, 1996 相似文献
23.
The principle of potentiometric hydrogen sensors based on protonic conductors is reviewed. The origin of the potentiometric
response in inert gas (Nernst potential) and in air (mixed potential) is discussed. It is shown that the nature of the sensing
electrode as well as the morphology influence the mixed potential response. The properties of the solid-state internal reference
electrode are also examined and discussed. A H+ reversible electrode based on quinhydrone is described. Then, an example of solid-state potentiometric hydrogen sensor is
presented. The device incorporates a protonic polymer electrolyte based on polybenzimidazole, a Pt gas diffusion electrode
or a Pt grid as sensing electrode and a reference electrode based on Ag-AgCl. The sensing characteristics in nitrogen and
dry air are reported.
Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15 – 21, 2002. 相似文献
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26.
Mohamed Benchidmi Philippe Bouchet Ren Lazaro 《Journal of heterocyclic chemistry》1979,16(8):1599-1603
Synthese and nmr study of forty-four nitroindazoles in which twentry-three were never published have been carried out. The best way to obtain the halogenomethyl derivatives(halogenation before or after methylation) is shown. Relative reactivities of the different heterocyclic ring positions toward the electrophilic agent are discussed. 相似文献
27.
Robert J. Messinger Tan Vu Huynh Renaud Bouchet Vincent Sarou-Kanian Michaël Deschamps 《Magnetic resonance in chemistry : MRC》2020,58(11):1118-1129
Magic-angle-spinning (MAS) enhances sensitivity and resolution in solid-state nuclear magnetic resonance (NMR) measurements. MAS is obtained by aerodynamic levitation and drive of a rotor, which results in large centrifugal forces that may affect the physical state of soft materials, such as polymers, and subsequent solid-state NMR measurements. Here, we investigate the effects of MAS on the solid-state NMR measurements of a polymer electrolyte for lithium-ion battery applications, poly(ethylene oxide) (PEO) doped with the lithium salt LiTFSI. We show that MAS induces local chain ordering, which manifests itself as characteristic lineshapes with doublet-like splittings in subsequent solid-state 1 H, 7 Li, and 19 F static NMR spectra characterizing the PEO chains and solvated ions. MAS results in distributions of stresses and hence local chain orientations within the rotor, yielding distributions in the local magnetic susceptibility tensor that give rise to the observed NMR anisotropy and lineshapes. The effects of MAS were investigated on solid-state 7 Li and 19 F pulsed-field-gradient (PFG) diffusion and 7Li longitudinal relaxation NMR measurements. Activation energies for ion diffusion were affected modestly by MAS. 7Li longitudinal relaxation rates, which are sensitive to lithium-ion dynamics in the nanosecond regime, were essentially unchanged by MAS. We recommend that NMR researchers studying soft polymeric materials use only the spin rates necessary to achieve the desired enhancements in sensitivity and resolution, as well as acquire static NMR spectra after MAS experiments to reveal any signs of stress-induced local ordering. 相似文献
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29.
Abelev BI Aggarwal MM Ahammed Z Anderson BD Anderson M Arkhipkin D Averichev GS Bai Y Balewski J Barannikova O Barnby LS Baudot J Bekele S Belaga VV Bellingeri-Laurikainen A Bellwied R Benedosso F Bhardwaj S Bhasin A Bhati AK Bichsel H Bielcik J Bielcikova J Bland LC Blyth SL Bonner BE Botje M Bouchet J Brandin AV Bravar A Burton TP Bystersky M Cadman RV Cai XZ Caines H Calderón de la Barca Sánchez M Castillo J Catu O Cebra D Chajecki Z Chaloupka P Chattopadhyay S Chen HF Chen JH Cheng J 《Physical review letters》2006,97(15):152301
Transverse momentum spectra of pi+/-, p, and p up to 12 GeV/c at midrapidity in centrality selected Au + Au collisions at square root sNN=200 GeV are presented. In central Au + Au collisions, both pi +/- and p(p) show significant suppression with respect to binary scaling at pT approximately >4 GeV/c. Protons and antiprotons are less suppressed than pi+/-, in the range 1.5 approximately < pT approximately < 6 GeV/c. The pi-/pi+ and p/p ratios show at most a weak pT dependence and no significant centrality dependence. The p/pi ratios in central Au + Au collisions approach the values in p + p and d + Au collisions at pT approximately >5 GeV/c. The results at high pT indicate that the partonic sources of pi+/-, p, and p have similar energy loss when traversing the nuclear medium. 相似文献
30.
Adams J Aggarwal MM Ahammed Z Amonett J Anderson BD Arkhipkin D Averichev GS Badyal SK Bai Y Balewski J Barannikova O Barnby LS Baudot J Bekele S Belaga VV Bellingeri-Laurikainen A Bellwied R Berger J Bezverkhny BI Bharadwaj S Bhasin A Bhati AK Bhatia VS Bichsel H Bielcik J Bielcikova J Billmeier A Bland LC Blyth CO Blyth SL Bonner BE Botje M Boucham A Bouchet J Brandin AV Bravar A Bystersky M Cadman RV Cai XZ Caines H Sánchez MC Catu O Cebra D Chajecki Z Chaloupka P Chattopadhyay S Chen HF 《Physical review letters》2006,97(15):152302
Measurements of the production of forward pi0 mesons from p + p and d + Au collisions at square root sNN=200 GeV are reported. The p + p yield generally agrees with next-to-leading order perturbative QCD calculations. The d + Au yield per binary collision is suppressed as eta increases, decreasing to approximately 30% of the p + p yield at eta =4.00, well below shadowing expectations. Exploratory measurements of azimuthal correlations of the forward pi0 with charged hadrons at eta approximately 0 show a recoil peak in p + p that is suppressed in d + Au at low pion energy. These observations are qualitatively consistent with a saturation picture of the low-x gluon structure of heavy nuclei. 相似文献