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The d.s.c. curves of commercial samples of methaqualone—Qulude (U.S.A.), Qulude (Mexico), Sopar, Mandrax and Parest — are presented. Similar d.s.c. curves were found for Qulude (U.S.A.), Qulude (Mexico), and Mandrax, while Sopar and Parest exhibited different types of curves. New and old formulations of the Qulude (U.S.A.) brand could be differentiated by differences in the tablet filler and binder. Unfortunately, d.s.c. could not be used to determine the country of origin of the drug, although it was useful to characterize it. The technique can be used to identify samples of 0.15 mg or less. 相似文献
6.
Summary A generalized expression for the negative adsorption of anions by clay suspensions has been derived using an extension of
the procedure developed bySchofield. Negative adsorption of chloride by Na-montmorillonite has been measured in NaCl solutions from 0.1 M to 0.001 M. If the
clay was purified by ultrafiltration, measured negative adsorption nearly equalled that calculated from diffuse double layer
theory over the entire range of concentration. At very low electrolyte concentrations the measured negative adsorption was
less than the calculated amount, probably as a result of the presence of positive charges. Polyanions such as those of metaphosphate
or acrylic acid increased the negative adsorption in this region to the theoretical amount. At NaCl concentration between
0.05 and 0.005 M NaCl measured negative adsorption was a maximum of 20 per cent lower than that calculated. This probably
represented the error of the approximations made in the theoretical calculations by neglecting the effect of activity corrections
in the double layer.
Zusammenfassung Ein verallgemeinerter Ausdruck für die negative Adsorption von Anionen in Tonsuspensionen wird unter Erweiterung des vonSchofield verwendeten Rechnungsverfahrens abgeleitet. Die negative Adsorption von Chlorid durch Natrium-Montmorillonite wird mit NaCl-L?sungen, 0,1 M-0,00 m, gemessen. Wenn der Ton durch Ultrafiltration gereinigt war, kam die gemessene negative Adsorption über den ganzen Konzentrationsbereich nahezu der aus der Theorie der diffusen Doppelschicht berechneten gleich. Bei sehr niedrigen Elektrolytgehalten war die gemessene negative Adsorption geringer als die berechnete, wahrscheinlich als Ergebnis der Anwesenheit von positiven Ladungen. Polyanionen wie Metaphosphat oder Acryls?ure erh?hten die negative Adsorption in diesem Bereich auf den theoretischen Wert. Für NaCl-Konzentrationen zwischen 0,05 und 0,005 m zeigte die gemessene negative Adsorption ein um 20% niedriger liegendes Maximum als das berechnete. Dies repr?sentiert wahrscheinlich den Fehler in den N?herungen, die in den theoretischen Berechnungen durch Vernachl?ssigung der Effekte der Aktivit?tskorrekturen in der Doppelschicht verursacht werden.相似文献
7.
Gd10C4Cl18 and Gd10C4Cl17, Two Lanthanoid Cluster Compounds with Interstitial C2 Units The compounds Gd10C4Cl18 ( I ) and Gd10C4Cl17 ( II ) are prepared by heating stoichiometric amounts of GdCl3, Gd, and graphite in sealed tantalum tubes at 1070 ( I ) and 1 120 K ( II ). Single crystal investigations ( I : P21/c, Z = 2, a = 918.2, b = 1 612.0, c = 1 288.6 pm, β = 119.86°; II : P1 , Z = 1, a = 849.8, b = 917.4, c = 1 146.2 pm, α = 104.56°, β = 95.98°, γ = 111.35°) revealed the occurrence of novel Gd10C4Cl18 clusters. The metal framework is formed by edge-sharing of two Gd6 octahedra. These are centred by C2 units (dC? C = 147 pm) and Cl atoms bridge all available edges of the octahedra. The structure of I corresponds to a packing of such quasi molecular clusters, in II they are linked to chains via common Cl atoms. Both structures are discussed in terms of a model of close packed spheres as well as in the concept of condensed clusters. 相似文献
8.
Wojciech Czardybon Wojciech Sokol John Warkentin Nick Henry Werstiuk 《Journal of Physical Organic Chemistry》2008,21(1):41-46
Synthesis of a bicyclic 2,2‐dioxa oxadiazoline (6,7‐diaza‐1‐methoxy‐5‐methyl‐2,8‐dioxabicyclo[3.2.1]oct‐6‐ene) is reported. Its thermolysis at 27°C is about 200 times as fast as the thermolysis of a monocyclic oxadiazoline model system. Presumably, a cyclic dioxa carbonyl ylide is formed initially and the ylide then undergoes a bond scission to afford either a dioxacarbene or a dialkylcarbene or it cyclizes to an oxirane. A small fraction of a dialkylcarbene was trapped as the product of addition to dimethyl acetylenedicarboxylate (DMAD). Computations of the barriers to the loss of N2 from the oxadiazolines and to the formation of the carbenes from the carbonyl ylide resulting from thermolysis of the bicyclic oxadiazoline are compared to corresponding barriers for a similar monocyclic oxadiazoline. The rate acceleration is accounted for in terms of geometric factors. The complex products from the decomposition of the bicyclic oxadiazoline were not studied. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
9.
Kolb NR Rauf AW Igarashi R Hornidge DL Pywell RE Warkentin BJ Korkmaz E Feldman G O'Rielly GV 《Physical review letters》2000,85(7):1388-1391
Cross sections for quasifree Compton scattering from the deuteron were measured for incident energies of E(gamma) = 236-260 MeV at the laboratory angle straight theta(gamma(')) = -135 degrees. The recoil nucleons were detected in a liquid-scintillator array situated at straight theta(N) = 20 degrees. The measured differential cross sections were used, with the calculations of Levchuk et al., to determine the polarizabilities of the bound nucleons. For the bound proton, the extracted values were consistent with the accepted value for the free proton. Combining our results for the bound neutron with those from Rose et al., we obtain 1-sigma constraints of alpha;(n) = 7.6-14.0 and beta;(n) = 1.2-7.6. 相似文献
10.
N. Warkentin M. Diehl D. Yu. Ivanov A. Schäfer 《The European Physical Journal A - Hadrons and Nuclei》2007,32(3):273-291
We investigate electroproduction of pion pairs on the nucleon in the framework of QCD factorization for hard exclusive processes.
We extend previous analyses by taking the hard-scattering coefficients at next-to-leading order in αs . The dynamics of the produced pion pair is described by two-pion distribution amplitudes, for which we perform a detailed
theoretical and phenomenological analysis. In particular, we obtain constraints on these quantities by comparing our results
with measurements of angular observables that are sensitive to the interference between two-pion production in the isoscalar
and isovector channels. 相似文献