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81.
82.
(7)Li and (6)Li nuclear magnetic resonance (NMR) experiments are carried out on the perovskite Li(3x)La(1/3-x)NbO(3). The results are compared to those obtained on the titanate Li(3x)La(2/3-x)TiO3 (LLTO) in order to investigate the effect, on the lithium ion dynamics, of the total substitution of Nb(5+) for Ti(4+) in the B-site of the ABO(3) perovskites. The XRD patterns analysis reveals that this substitution leads to a change in the distribution of the La(3+) ions in the structure. La(3+) ions distribution is very important, in regard to ionic conductivity, because these immobile ions can be considered as obstacles for the long-range Li+ motion. If compared to the titanates, the compounds of the niobate solid solution have a bigger unit cell volume, a smaller number of La(3+) ions, and a higher number of vacancies. These should favor the motion of the mobile ions into the structure. This is not experimentally observed. Therefore, the interactions between the mobile species and their environment greatly influence their mobility. (7)Li and (6)Li NMR relaxation time experiments reveal that the Li relaxation mechanism is not dominated by quadrupolar interaction. (7)Li NMR spectra reveal the presence of different Li+ ion sites. Some Li+ ions reside in an isotropic environment with no distortion, some others reside in weakly distorted environments. T(1), T(1)(rho), and T(2) experiments allow us to evidence two motions of Li+. As in LLTO, T(1) probes a fast motion of the Li+ ions inside the A-cage of the perovskite structure and T(1)(rho) a slow motion of these ions from A-cage to A-cage. At variance with what has been observed in LLTO, these different Li+ ions can be differentiated through the spin-lattice relaxation times, T(1) and T(1)(rho), as well as through the transverse relaxation time, T(2). 相似文献
83.
Summary Let B
tbe a one-dimensional Brownian motion and let L
tbe its local time at zero. We answer a question of J. Pitman by showing that the canonical filtrations of B and B + cL are equal for all real constants, c. It is also shown that the filtrations of ¦B¦ and ¦B¦ + cL are equal if and only if c 1.
The first author acknowledges the support a U.B.C. Post-doctoral Fellowship; the second one that of an NSERC University Research Fellowship 相似文献
The first author acknowledges the support a U.B.C. Post-doctoral Fellowship; the second one that of an NSERC University Research Fellowship 相似文献
84.
O. Martins J.Y. Buzaré J. Emery P. Claudy J.M. LéTOFFé V. Brandel M. Genet 《Journal of Sol-Gel Science and Technology》1997,8(1-3):315-319
Different transparent phosphate xerogels were synthesized using concentrated solutions of metal chlorides and phosphoric acid
with a proper mole ratio of both components. By this method we prepared bulk samples of thorium and tin(IV) phosphate xerogels
by drying at room temperature or at 350 K. Some properties of these amorphous materials were studied by means of differential
scanning calorimetry (DSC) and electron paramagnetic resonance (EPR) techniques. Depending on mole ratio metal/phosphate,
these xerogels show, near 180 K, inflection points which we interpret asT
g
. Samples dried at 425 K lose their transparency and have noT
g
. Thus, it seems that the “glassy” state is due to water molecules remaining in the material. The same properties were confirmed
by EPR studies of the xerogels doped with Cr3+ and Fe3+ ions as probes. These results show the existence of two different phases in the xerogels: a liquid-like one, in the range
from 190 K to 350 K and a solid-like one, in the range from 4 K to 190 K. 相似文献
85.
Thomas Piper Caroline Emery Andreas Thomas Martial Saugy Mario Thevis 《Analytical and bioanalytical chemistry》2013,405(16):5455-5466
Carbon isotope ratio (CIR) analysis has been routinely and successfully applied to doping control analysis for many years to uncover the misuse of endogenous steroids such as testosterone. Over the years, several challenges and limitations of this approach became apparent, e.g., the influence of inadequate chromatographic separation on CIR values or the emergence of steroid preparations comprising identical CIRs as endogenous steroids. While the latter has been addressed recently by the implementation of hydrogen isotope ratios (HIR), an improved sample preparation for CIR avoiding co-eluting compounds is presented herein together with newly established reference values of those endogenous steroids being relevant for doping controls. From the fraction of glucuronidated steroids 5β-pregnane-3α,20α-diol, 5α-androst-16-en-3α-ol, 3α-Hydroxy-5β-androstane-11,17-dione, 3α-hydroxy-5α-androstan-17-one (ANDRO), 3α-hydroxy-5β-androstan-17-one (ETIO), 3β-hydroxy-androst-5-en-17-one (DHEA), 5α- and 5β-androstane-3α,17β-diol (5aDIOL and 5bDIOL), 17β-hydroxy-androst-4-en-3-one and 17α-hydroxy-androst-4-en-3-one were included. In addition, sulfate conjugates of ANDRO, ETIO, DHEA, 3β-hydroxy-5α-androstan-17-one plus 17α- and androst-5-ene-3β,17β-diol were considered and analyzed after acidic solvolysis. The results obtained for the reference population encompassing n?=?67 males and females confirmed earlier findings regarding factors influencing endogenous CIR. Variations in sample preparation influenced CIR measurements especially for 5aDIOL and 5bDIOL, the most valuable steroidal analytes for the detection of testosterone misuse. Earlier investigations on the HIR of the same reference population enabled the evaluation of combined measurements of CIR and HIR and its usefulness regarding both steroid metabolism studies and doping control analysis. The combination of both stable isotopes would allow for lower reference limits providing the same statistical power and certainty to distinguish between the endo- or exogenous origin of a urinary steroid. 相似文献
86.
A. Sandrucci R. Lezé G. Guglielmo Bermbach und Sidney S. Emery 《Fresenius' Journal of Analytical Chemistry》1901,40(3):170-172
Ohne Zusammenfassung 相似文献
87.
88.
89.
G. Hansen Carl Zeiss R. Ramb O. Schließmann K. Zänker F. H. Emery H. S. Booth A. de Gramont A. R. Striganow E. Brand F. Twyman E. Harvey K. A. Ssuchenko G. S. Landsberg S. L. Mandelstam S. W. Tuljankin W. F. Smirnow W. W. Zeiden S. A. Alexandrow S. M. Raisski H. B. Vincent R. A. Sawyer G. Scheibe A. Schöntag E. Lay A. Keil H. Martin und L. Wwedjenski 《Fresenius' Journal of Analytical Chemistry》1938,114(1-2):43-55
Ohne Zusammenfassung 相似文献
90.