Phenylalkylamine alkaloids from Stapelia hirsuta L

Four alkaloids of the phenethylamine derivatives have been isolated from the n-butanol fraction of the aerial parts of Stapelia hirsuta L. The structures of the isolated alkaloids were determined as N-acetyl hordenine (a new natural compound), hordenine, candicine and hordenine-1-O-beta-D-glucoside, in addition to luteolin-7-O-beta-D-glucopyranoside.     

Crystal structure and thermal study of the new hydrated cadmium-cerium(III) chloride CeCd4Cl11·13H2O

The new double-salt CeCd₄Cl₁₁·13H₂O in the ternary system CeCl₃-CdCl₂-H₂O has been prepared from aqueous solution upon evaporation at 5°C and characterized based on elemental analysis, spectroscopic data, thermal studies and X-ray powder and single-crystal diffraction. CeCd₄Cl₁₁·13H₂O crystallizes in the monoclinic space group P2₁ with a=7.667(2), b=17.351(3), c=11.970(2)Å, β=101.61(3)° and Z=2. After refinement of the structure the reliability factor R in the final cycle is 0.064. The structure can be regarded as consisting of endless double chains of CdCl₆ and CdOCl₅ octahedra and isolated tricapped triangular prisms surrounding the cerium cations. Differential scanning calorimetry showed that the title compound exhibits five endothermic anomalies interpreted from thermogravimetry. A comparison with the structure of SrCd₂Cl₆·8H₂O is proposed.     

Action des hydrazines fluoroalkylées sur les phosphoallènes: synthèse d’hydrazones N-fluoroalkylées β-phosphonatées

Ten phosphorylated β-hydrazones of structure R₂P(O)C(NNHR_F)CHR₂′ were prepared in 54-91% yield by heating the allenes R₂P(O)CHCCR₂′ with fluorinated hydrazines H₂NNHR_F in chloroform or methanol [R=Ph, OCH₂C(Me)₂CH₂O or OCH₂C(Me)(Pr)CH₂O, R′=H or Me and R_F=CH₂CF₃ or C₆F₅]. Two cyclohexyl derivatives were prepared similarly from R₂P(O)CHCCy. The triphenyl derivatives Ph₂P(O)CH₂C(NNHCH₂CF₃)Ph and Ph₂P(O)CH₂C(NNHC₆F₅)Ph were made in 91 and 68% yield by heating the ketones Ph₂P(O)CH₂C(O)Ph with an ethanol solution of the corresponding hydrazines. The stereochemistry of the hydrazones was determined by multinuclear NMR experiments. Compounds with C(NNHR_F)Me groups exist as a mixture of Z and E isomers, with the Z form predominating (fluorinated group syn to phosphorus). Those with C(NNHR_F)CHMe₂, C(NNHR_F)Cy or C(NNHR_F)Ph groups were formed selectively, the Z isomers being the only products. The results are explained by steric hindrance, the bulkier isopropyl, cyclohexyl or phenyl group disfavouring the E configuration. , , , NMR data, coupling constants and IR data are reported.     

Multi-element determination in sandstone rock by instrumental neutron activation analysis

Summary Instrumental neutron activation analysis (INAA) was used for the qualitative and quantitative analysis of sandstone samples of Aswan area, in South Egypt. The samples were properly prepared together with standards and simultaneously irradiated by a neutron flux of 7 ^. 10¹¹ n ^. cm^-2.s^-1. in the TRIGA research reactor facilities in Mainz. The gamma-spectra from a hyperpure germanium HPGe detector were analyzed. The present study provides the basic data of elemental concentrations of a sandstone rock. The following elements have been determined: Na, K, Fe, Sc, Cr, Co, Zr, Ce, La, Nd, Sm, Eu, Yb, Lu, Hf, Ta, Th and U. Energy dispersive X-ray fluorescence (EDXRF) was used for comparison and to detect elements which can be detected only by this method.     

Crystal structure of a new double salt hydrate SrCd2Cl6⋅8H2O

SrCd₂Cl₆8H₂O crystallizes in the space group and has the unit cell dimensions a = 9.688(2) Å, b = 11.212(2) Å, c = 7.732(3) Å, = 99.85(21)°, = 89.95(22)°, = 75.81(13)°, and Z = 2. After refinement through full-matrix least-squares methods, the reliability factor R in the final cycle is 4.65%. A very persistent occurrence of twinning by pseudosymmetry was observed. The twin element is a twofold axis [001]. The title compound exhibits five endothermic peaks, which have been detected by differential scanning calorimetry and interpreted from thermogravimetry.     

Dynamical analysis and anti-oscillation-based adaptive control of the FO arch MEMS with optimality

Nonlinear Dynamics - This paper mainly investigates dynamical analysis and anti-oscillation-based adaptive control issues of the fractional-order (FO) arch microelectromechanical system (MEMS) with...     

Vortex analysis of the periodic Ginzburg–Landau model

We study the vortices of energy minimizers in the London limit for the Ginzburg–Landau model with periodic boundary conditions. For applied fields well below the second critical field we are able to describe the location and number of vortices. Many of the results presented appeared in [H. Aydi, Doctoral Dissertation, Université Paris-XII, 2004], others are new.     

An efficient method for the synthesis of spiro and fused N-heterocyclic phosphor esters. Reactions of triketoindan-2-oxime with α-phosphonyl carbanions

Treatment of triketoindan-2-oxime with α-phosphonyl carbanions in sodium ethanolate solution at reflux temperature led to a number of the corresponding substituted spiroisooxazole-, fused 1,3-oxazole, and 1,4-oxazine phosphor esters in moderate to high yields. Mechanisms for the formation of five- and six-membered rings are provided. A comparison of Wittig-Horner and Wittig reagent counterparts in reactions with the oxime is discussed. The various biological properties of selected examples of the synthesized products were studied. Correspondence: Wafaa M. Abdou, Chemical Industries Division, National Research Center, Elbohouth St., D-12622 Dokki, Cairo, Egypt.     

Investigation of the primary processes occurring at the tin/semiconducting layer/electrolyte interfaces by rapid pulse technique: Part II. Studies of the Sn/Te/electrolyte system

Tellurium layers are cathodically deposited on the surface of tin substrate from a sodium tellurite bath of pH 9.67. The electrode is anodically polarized using rapid galvanostatic rectangular pulses. Apparent specific resistance values calculated from resistance overpotentials demonstrate the semiconducting nature of the tellurium layers. The observed resistance, being too high compared to the reported values for Te crystals suggests the presence of amorphous Te in the electrodeposited phase, as well as the persistence of adsorbed hydrogen cathodically formed. Activation overpotentials are interpreted in view of the primary processes probably operating at the electrode/solution interface. These are associated with the corrosion of tellurium, or occasionally tin in its pores.