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Ohne ZusammenfassungÜbersetzt von Dr. K. Jäckel, Marburg/L.Wir danken Herrn Prof. N. R. Dhar D.Sc. (London und Paris), F.R.I.C., F.N.I., I.E.S. (Eetd) Direktor Shila Dhar Institut für Bodenkunde und Vorstand der Chemischen Abteilung, Universität Allahabad, für sein lebhaftes Interesse und seine Ratschläge für die Arbeit. 相似文献
3.
Swarup Narain Tewari 《Mikrochimica acta》1967,55(4):704-707
Summary A paper Chromatographic technique on salt-buffered papers for separating the alkaloids of opium has been devised. The method has been used for determining the origin of opium samples by studying the pattern of theR
f
values of the alkaloids present and the effect on it produced by the presence of various adulterants.
Zusammenfassung Die chromatographische Trennung der Opiumalkaloide auf gepuffertem Papier wurde beschrieben. Das Verfahren wurde zur Herkunftsbestimmung von Opiumproben auf Grund desR f -Musters der anwesenden Alkaloide benützt. Der Einfluß verschiedener Fälschungszusätze wurde untersucht.
Résumé Mise au point d'une technique de Chromatographie sur papier pour la séparation des alcaloïdes de l'opium, oú les papiers sont imprégnés des sels tampons. Utilisation de la méthode pour déterminer l'origine des échantillons d'opium en étudiant les valeurs duR f des alcaloïdes présents et l'effet produits sur celles-ci par la présence d'adultérants divers.相似文献
4.
5.
Magnesium aluminate doped with Tb3+ (MgAl2O4:Tb3+) was prepared by combustion synthesis. Three thermoluminsence (TL) peaks at 120, 220 and 340 °C were observed. PL and TL emission spectrum shows that Tb3+ acts as the luminescent centre. Optically stimulated luminescence (OSL) was observed when stimulated by 470 nm blue light.Electron spin resonance (ESR) studies were carried out to identify the defect centres responsible for the TL and OSL processes in MgAl2O4:Tb3+. Two defect centres were identified in irradiated MgAl2O4:Tb3+ phosphor by ESR measurements which was carried out at room temperature and these were assigned to V and F+ centres. V centre (hole centre) is correlated to 120 and 220 °C TL peaks and F+ centre (electron centre), which acts as a recombination centre is correlated to 120, 220 and 340 °C. 相似文献
6.
Theac anddc electroluminescence in CaS:Cu, Sm have been investigated. The luminescence spectra show three peaks in the visible region.
The brightness-voltage dependence satisfies the relationB=B
0 exp (−b/V
1/2) with two modes of variation. The nature of this dependence indc andac at different frequencies is discussed. The electroluminescence brightness also depends on the temperature of the phosphors
and shows a peak around 80.0;C. The electroluminescence efficiency increases with applied voltage up to 2200 V and this dependence
on V is explained on the basis of a transport process of the Schottky emission type. 相似文献
7.
T.S. TripathiG.C. Tewari A.K. Rastogi C.S. YadavP.L. Paulose 《Journal of magnetism and magnetic materials》2011,323(17):2300-2304
We present a detail study of the effect of excess metal atoms on the magnetic properties of Cu1+xCr2+yTe4 at 2-400 K. With the increase in x=0-1 and y<0.3, these compounds retain metallic behavior, while ferromagnetic ordering temperature reduces from 325 to 160 K. Our low field susceptibility χac measurements reveal a second transition on cooling below the ferromagnetic ordering; the transition at around 160-180 K intensifies with the excess amount of copper and chromium atoms. The value of spontaneous magnetization at 2 K remains between 2.6 and 2.9μB across all the compositions and it reduces with temperature as M(T)∼A0T3/2+A1T5/2, as expected for the excitation of Bloch's spin waves in a model of the Heisenberg ferromagnet. Our terminal composition Cu1.9Cr2.25Te4 showed only second transition at 160 K with short range magnetic order much above the transition temperature and in the absence of the specific heat jump at this temperature. The magnetic properties are explained as a result of random magnetic anisotropy in the excess-metal compositions induced by the interstitial atomic defects in their parent spinel structure. The large stuffing of cations has been made possible in the telluride compounds because of the large size of tellurium and also by the covalent bonding that stabilizes the defect structure. 相似文献
8.
We investigate the BCS-BEC crossover in three-dimensional degenerate Fermi gases in the presence of spin-orbit coupling (SOC) and Zeeman field. We show that the superfluid order parameter destroyed by a large Zeeman field can be restored by the SOC. With increasing strengths of the Zeeman field, there is a series of topological quantum phase transitions from a nontopological superfluid state with fully gapped fermionic spectrum to a topological superfluid state with four topologically protected Fermi points (i.e., nodes in the quasiparticle excitation gap) and then to a second topological superfluid state with only two Fermi points. The quasiparticle excitations near the Fermi points realize the long-sought low-temperature analog of Weyl fermions of particle physics. We show that the topological phase transitions can be probed using the experimentally realized momentum-resolved photoemission spectroscopy. 相似文献
9.
Kinshuk Dasgupta D. Sen T. Mazumdar R. K. Lenka R. Tewari S. Mazumder J. B. Joshi S. Banerjee 《Journal of nanoparticle research》2012,14(3):728
For the first time, bamboo-shaped multiwalled carbon nanotubes, having diameter of the order of 50 nm, have been grown on carbon black in a fluidized bed in bulk amount. The activation energy for the synthesis of the product was found out to be around 33 kJ/mol in the temperature range of 700−900 °C. The carbon nanotubes were separated from the carbon black by preferential oxidation of the later, the temperature of which was determined by thermogravimetry. The transmission electron microscopy revealed different features of the nanotubes such as “Y” junction, bend, and catalyst filling inside the nanotubes. Small angle neutron scattering was performed on the nanotubes synthesized at different temperatures. The data were fitted into a suitable model in order to find out the average diameter, which decreases with increase in synthesis temperature. The Monte Carlo simulation predicts the same behavior. Based on the above observations, a possible growth mechanism has been predicted. The oscillation in carbon saturation value inside the catalyst in the fluidized bed has been indicated as the responsible factor for the bamboo-shaped structure. 相似文献
10.
Diner A Toker Y Strasser D Heber O Ben-Itzhak I Witte PD Wolf A Schwalm D Rappaport ML Bhushan KG Zajfman D 《Physical review letters》2004,93(6):063402
The cross sections for electron detachment of internally cold Cn- and Aln- clusters were measured using an electrostatic ion beam trap fitted with an internal electron target. The measured electron-impact detachment cross sections for the Cn- (n = 1-9) clusters exhibit even-odd oscillations reflecting the binding energy trend, namely, higher cross sections for weaker binding. Surprisingly, however, these cross sections increase on the average with cluster size, n, in spite of the increase in electron binding. In contrast, the Aln- (n = 2-5) clusters follow the known scaling laws for electron detachment. We suggest that the size-dependent polarizability of these clusters is responsible for the observed behavior. 相似文献