The use of differential scanning calorimetry to identify methaqualone samples: forensic applications.

The d.s.c. curves of commercial samples of methaqualone—Qu$\text{aa}$lude (U.S.A.), Qu$\text{aa}$lude (Mexico), Sopar, Mandrax and Parest — are presented. Similar d.s.c. curves were found for Qu$\text{aa}$lude (U.S.A.), Qu$\text{aa}$lude (Mexico), and Mandrax, while Sopar and Parest exhibited different types of curves. New and old formulations of the Qu$\text{aa}$lude (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.     

The negative adsorption of anions by clay suspensions

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.

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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.

     

Gd10C4Cl18 und Gd10C4Cl17, zwei Seltenerdmetall-Clusterverbindungen mit interstitiellen C2-Gruppen

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 (d_{C? 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.     

Influence of Test Specimen Geometry and Water Soaking on the In Vitro Cytotoxicity of Orthocryl®, Orthocryl® LC,Loctite® EA 9483 and Polypropylene

Depending on their composition, plastics have a cytotoxic potential that needs to be evaluated before they are used in dentistry, e.g., as orthodontic removable appliances. Relevant guidelines set out requirements that a potential new resin in the medical field must meet, with a wide scope for experimental design. In the present study, test specimens of different geometries consisting of varying polymers (Orthocryl^®, Orthocryl^® LC, Loctite^® EA 9483, Polypropylene) were soaked for different periods of time, then transferred to cell culture medium for 24 h, which was subsequently used for 24-h cultivation of A549 cells, followed by cytotoxicity assays (WST-1, Annexin V-FITC-propidium iodide (PI) flow cytometry). In this context, a reduction in the cytotoxic effect of the eluates of test specimens prepared from Orthocryl^® LC and Loctite^® EA 9483 was particularly evident in the Annexin V-FITC-PI assay when the soaking time was extended to 48 h and 168 h, respectively. Consistent with this, a reduced release of potentially toxic monomers into the cell culture medium, as measured by gas chromatography-mass spectrometry, was observed when the prior soaking time of test specimens of all geometries was extended. Remarkably, a significant increase in cytotoxic effect was observed in the WST-1 assay, which was accompanied by a higher release of monomers when the thickness of the test sample was increased from 0.5 to 1.0 mm, although an elution volume adapted to the surface area was used. However, further increasing the thickness to 3.0 mm did not lead to an increase in the observed cytotoxicity or monomer release. Test specimens made of polypropylene showed no toxicity under all test specimen sizes and soaking time conditions. Overall, it is recommended to perform toxicity studies of test specimens using different geometries and soaking times. Thereby, the influence of the different specimen thicknesses should also be considered. Finally, an extension of the test protocols proposed in ISO 10993-5:2009 should be considered, e.g., by flow cytometry or monomer analysis as well as fixed soaking times.     

6,7‐diaza‐1‐methoxy‐ 5‐methyl‐2, 8‐dioxabicyclo[3.2.1]oct‐6‐ene. An unstable bicyclic precursor of a dioxa carbonyl ylide and carbenes by ylide ring opening

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.     

Quasifree compton scattering from the deuteron and nucleon polarizabilities

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.