Micro-SR-XRF studies for archaeological gold identification—the case of Carpathian gold and Romanian museal objects

In the determination of the provenance of gold in archaeological artifacts, trace elements are more significant than the main components. Several minute fragments of natural Carpathian gold—placer and primary—and some very small (a few milligrams) fragments of archaeological items were studied using micro Synchrotron Radiation X-Ray Fluorescence (micro SR-XRF) at the BESSY Synchrotron Facility in Berlin, Germany. The goal of the study was to identify the trace elements characterizing Carpathian gold, looking especially at Sn, Sb, Pb and Te, and to determine if the gold in the archaeological items is native or refined. Applications to the authentication and provenance of nine Dacian gold bracelets, koson coins and two Bronze Age items are presented.     

Calculating hydrodynamics problems for a liquid film flowing radially on a flat horizontal surface

A mathematical hydrodynamic model of a thin liquid film flowing radially on a flat horizontal surface has been elaborated. The model consisted of continuity and momentum equations which were resolved by means of the integral method. In fact, several versions of the model were examined; they differed mainly in film velocity distribution. The predictions of the different versions were then compared with liquid film thicknesses obtained from experimental investigation. The best version was applied in further calculations.     

Harnack inequality for symmetric stable processes on fractalsL'inégalité de Harnack pour les processus symétriques stables sur les fractals

We study nonnegative harmonic functions of symmetric α-stable processes on d-sets F. We prove the Harnack inequality for such functions when α∈(0,2/d_w)∪(d_s,2). Furthermore, we investigate the decay rate of harmonic functions and the Carleson estimate near the boundary of a region in F. In the particular case of natural cells in the Sierpiński gasket we also prove the boundary Harnack principle. To cite this article: K. Bogdan et al., C. R. Acad. Sci. Paris, Ser. I 335 (2002) 59–63.     

Fast atom bombardment mass spectra of O-isopropyl oligodeoxyribonucleotide triesters

The positive and negative fast atom bombardment (FAB) mass spectra of representative dimeric O-isopropyl oligodeoxyribonucleotide triesters were recorded and examined. Features found to be shared among the FAB mass spectra of these compounds yielded important information regarding molecular weight, nucleobase composition and nucleotide sequence.     

The influence of anharmonic and magnetic interactions on lattice dynamics of α and β phases of solid oxygen

The lattice dynamics of the ordered phases of solid oxygen have been studied. The anharmonic shifts for the librational excitations have been calculated. The comparison of harmonic and anharmonic results has shown that anharmonic effects in, solid oxygen are very important. An analysis of the influence of the magnetic ordering in the antiferromagnetic α phase suggest that magnetic interactions and elastic deformation of the crystal unit cell can compensate each other and lead to the accidental degeneration of the A_s and B_s librational energies in the α phase.     

Catalysis of hydrosilylation XIII. Gas-phase hydrosilylation of acetylene by trichlorosilane on functionalised silica supported rhodium and ruthenium phosphine complexes

Gas-phase hydrosilylation of acetylene by tri-chlorosilane catalyzed in a continuous flow apparatus by rhodium and ruthenium phosphine complexes immobilized on the silica via mercapto, phosphine, amine and nitrile ligands has been studied. GLC analysis of the reaction products showed vinyltrichlorosilane to be accompanied by products of double hydrosilylation of acetylene and the redistribution of trichlorosilane followed by the hydrosilylation and hydrogenative hydrosilylation of acetylene with dichlorosilane. A scheme for this complex competitive–consecutive reaction was proposed. The yield and selectivity of vinyltrichlorosilane can be much improved under special reaction conditions, e.g. rate flow of the particular substrates, temperature, given catalyst and others. Kinetic measurements carried out in the range of 115–140°C allowed us to evaluate the activation energy, E_a, for the vinyltrichlorosilane synthesis, which varied between 20.5 and 27.6 kJ mol^?1 for the selected rhodium and ruthenium supported complexes.     

Determination of PCBs in river sediment samples—proficiency test for selected Polish laboratories

Eighteen Polish laboratories participated in a proficiency test for the determination of PCBs in river sediment. The participants used their in-house method. The aim of the exercise was to obtain information about the state of the art of PCB analysis in environmental samples. Five PCBs (IUPAC nos. 52, 118, 138, 153 and 180) were selected for the test. The relative standard deviation of the analytical results submitted varied from 45 to 65%, with an outlier rate of 7%. The averages of the results for all analytes were in good agreement with reference values.     

Synthesis and Stereochemistry of Some New 1,3-Dioxane Derivatives of 1,4-Diacetylbenzene

Summary.  The synthesis and stereochemistry of new 1,3-dioxane derivatives of 1,4-diacetylbenzene are reported. The anancomeric structure of these compounds, the axial orientation of the aryl group for both 1,3-dioxane rings, and the cis and trans isomerism of some of these compounds is discussed considering data of conformational analysis, NMR investigations, and single crystal X-ray diffractometry. Received September 12, 2001. Accepted (revised) November 5, 2001     

Rational synthesis of multicyclic bis[2]catenanes

Bis-loop tetraurea calix[4]arene 6 has been prepared by acylation of the wide-rim calix[4]arene tetraamine 1 with the activated bis(urethane) 8 under dilution conditions. Similarly the bis(Boc-protected) tetraamine 2 is converted into the mono-loop derivative 3 which after deprotection and acylation gives the bisalkenyl derivative 5. In apolar solvents this tetraurea calix[4]arene 5 forms regioselectively a single hydrogen-bonded homodimer, from which the bis[2]catenane 10a is formed in 49% by a metathesis reaction followed by hydrogenation. Bis-loop derivative 6 forms no homodimers for steric reasons, but a stoichiometric mixture with the open-chain tetraalkenyl derivative 7a contains exclusively the heterodimer. Metathesis and subsequent hydrogenation now yields 65 % of the pure bis[2]catenane 10a which could not be isolated from the complex reaction mixture obtained from the homodimer 7a.7a. The chirality of 10a (D(2) symmetry) has been verified by optical resolution using HPLC on a chiral stationary phase.     

Submicrometer cavity surface plasmon sensors

A miniaturized spherical surface plasmon sensor for measuring the binding kinetics of unlabeled molecules is introduced. The sensor has a submicrometer footprint with a sensitivity that rivals that of state-of-the-art commercial planar surface plasmon sensors, which makes it valuable for applications requiring integration of detection of molecular species in microfluidic channels. The basic principle of the sensor is exploiting the wavelength shifts of the cavity resonances of a metal-coated submicrometer sphere embedded in an opaque metal film due to molecular adsorption. The sensor has been found to be exquisitely responsive in air to water and ethanol vapor adsorption on the bare gold sensor surface. When immersed in a liquid, the sensor can detect the adsorption of less than one monolayer of dodecanethiol (approximately 1.5 nm) on the gold coating of the sphere.