Ru-catalyzed oxidation of substituted acetylenes to α-keto esters and α-keto amides with iodosylbenzene

Oxidation of alkynyl ethers and -amines with iodosylbenzene in presence of Ru-catalysts affords α-keto esters and α-keto amides in 44–85% yield. These conversions can also be effected with RuO₄.     

Uranium-bearing francolites present in organic-rich limestones of NW Greece: a preliminary study using synchrotron radiation and fission track techniques

Synchrotron radiation techniques (μ-XRF and μ-XANES) were applied to the study of organic-rich phosphatized limestones of NW Greece (Epirus). The results revealed uranium accumulation in areas of the material containing, among others, carbonate apatite (francolite) and organic matter. The UL ₃-edge of μ-XANES spectra showed that uranium was present in tetravalent form. U-bearing francolite crystals were separated from the rock and characterized by Raman spectroscopy and microprobe. The analysis of the crystals also indicated the presence of sodium and sulfur. The uranium presence in the crystals was also visualized, after neutron irradiation and etching, by the observation of the fission tracks.

     

Novel organometallic chalcones functionalized with a crown ether fragment as optical ion chemosensors

We previously reported the synthesis and characterization of new organometallic chalcones derived from ferrocene, cyrhetrene and cymantrene functionalized with a benzo‐15‐crown‐5 fragment. The ferrocene and cyrhetrene chalcones have been investigated as chemosensors for metal ions with optical response in acetonitrile. Several metal ions were selected considering the diameter of the cavity and the charge‐to‐radius ratio of the cation. The stoichiometry of the complexes was determined using Job's method. It was found that Na⁺ and Ca²⁺ complexes have a 1:1 stoichiometry while a 2:1 (metaloligand‐to‐cation) stoichiometry was determined for Ba²⁺ and Pb²⁺ complexes. The association constants were calculated according to the stoichiometry of the complex and the results showed that they are directly affected by the electron‐withdrawing nature of the organometallic fragment. Moreover, complexes of ferrocenyl chalcone have larger association constants than those of the cyrhetrenyl analogue. This experimental observation is consistent with the electronic properties of the ferrocenyl fragment.     

Columnar liquid crystalline benzenetrisamides with pendant 1,3,4-oxadiazole groups

Novel liquid crystal materials based on 1,3,5-benzenetrisamide derivatives with three pendant 2-phenyl-5-(mono-, di-, and/or tri-n-alkoxyphenyl)-1,3,4-oxadiazole arms (Ia–c, IIa–c) were prepared. The mesomorphic properties of these compounds were characterised and studied by differential scanning calorimetry, polarising optical microscopy and X-ray diffraction. The formation of a columnar mesophase was found to be dependent on the number of alkoxy side chains. The compounds Ib and IIb, with a total of six alkoxy chains, and compounds Ic and IIc, with nine alkoxy chains, exhibited an enantiotropic hexagonal columnar (Col_h ) phase with high isotropisation temperatures; however, compounds Ia and IIa with a total of three alkoxy chains formed a crystalline phase. Compounds IIb and c were room temperature liquid crystals.     

A validated stability-indicating LC method for simultaneous determination of quinapril and hydrochlorothiazide in pharmaceutical samples

A stability-indicating liquid chromatographic method was developed and validated for simultaneous determination of quinapril and hydrochlorothiazide in drug substances and dosage forms. Chromatographic separation of quinapril, hydrochlorothiazide and its degradation products was achieved on a RP-18 column, using acetonitrile and phosphate buffer (pH 4.6) as mobile phase in a gradient mode and detection at 216 nm. Stress testing was performed under hydrolytic, oxidative, thermal and photolytic conditions. The degradation products were well resolved from main peaks, proving the stability-indicating power of the method. The assay was linear for quinapril and hydrochlorothiazide concentrations of 40–200 µg mL^?1 and 25–125 µg mL^?1, respectively. The developed method was selective, accurate and precise for quinapril and hydrochlorothiazide determination. This method was used to quantify both drugs in combined commercial tablets. The results showed that the proposed method was found to be suitable for quantitative determination and the stability study of quinapril and hydrochlorothiazide in pharmaceutical samples.      

Linear and nonlinear 2D finite element analysis of sloshing modes and pressures in rectangular tanks subject to horizontal harmonic motions

The influence of nonlinear wave theory on the sloshing natural periods and their modal pressure distributions are investigated for rectangular tanks under the assumption of two-dimensional behavior. Natural periods and mode shapes are computed and compared for both linear wave theory (LWT) and nonlinear wave theory (NLWT) models, using the finite element package ABAQUS. Linear wave theory is implemented in an acoustic model, whereas a plane strain problem with large displacements is used in NLWT. Pressure distributions acting on the tank walls are obtained for the first three sloshing modes using both linear and nonlinear wave theory. It is found that the nonlinearity does not have significant effects on the natural sloshing periods. For the sloshing pressures on the tank walls, different distributions were found using linear and nonlinear wave theory models. However, in all cases studied, the linear wave theory conservatively estimated the magnitude of the pressure distribution, whereas larger pressures resultant heights were obtained when using the nonlinear theory. It is concluded that the nonlinearity of the surface wave does not have major effects in the pressure distribution on the walls for rectangular tanks.