X-ray properties and interface study of B4C/Mo and B4C/Mo2C periodic multilayers

We present a comparative study of B₄C/Mo and B₄C/Mo₂C periodic multilayer structures deposited by magnetron sputtering. The characterization was performed by grazing incidence X-ray reflectometry at two different energies and high resolution transmission electron microscopy. The experimental results indicate the existence of an interdiffusion layer at the B₄C-on-Mo interface in the B₄C/Mo system. Thus, the B₄C/Mo multilayers were modeled by an asymmetric structure with three layers in each period. The thickness of B₄C-on-Mo interfacial layer was estimated about 1.1 nm. The B₄C/Mo₂C multilayers present less interdiffusion and are well modeled by a symmetric structure without interfacial layers. This study shows that B₄C/Mo₂C structure is an interesting alternative to B₄C/Mo multilayer for X-ray optic applications.     

Synthesis, X-ray diffraction analysis and NMR studies of (Z)-2-methyl-3-triphenylstannyl-3-pentene-2-ol

The synthesis of (Z)-2-methyl-3-triphenylstannyl-3-pentene-2-ol and its characterization by an X-ray diffraction study and multinuclear NMR are reported. The tin atom exhibits a distorted tetrahedral SnC₄ geometry with the four Sn---C bond distances experimentally equivalent. The slight distortion from the ideal tetrahedral geometry is because of the presence of a weak intramolecular HO → Sn interaction of 3.012(3) Å which produces a loose four-membered ring. The title compound was characterized in solution by ¹H, ¹³C and ¹¹⁹Sn NMR, and the persistence of the weak intramolecular HO → Sn coordination in solution was revealed by ¹³C and ¹¹⁹Sn secondary isotope multiplet of partially labelled entities (SIMPLE-NMR) experiments.     

Factors that control zeolite L crystal size

Time-series hydrothermal syntheses from two organic-cation-free gels with different compositions were employed to study the factors that control the final size of zeolite L crystals. The first gel had a starting K/Al ratio of 10, whereas in the second one it was three times lower. The relatively simple chemical composition of the starting gels and the combination of complementary characterization methods allowed us to track down the different stages of transformation of the initial amorphous gels into zeolite crystals and the factors that control the nucleation and growth processes. The role of the starting mixture components in the formation of the primary amorphous particles was explored. It was found that the profoundly different reaction kinetics in the two systems are caused by the difference in diffusion rates, which in turn are controlled by the extent of the polymerization reactions at room temperature during mixing of the starting components prior to hydrothermal treatment. As a consequence, nucleation is fast and ubiquitous in the first system with higher water content and K/Al ratio, whereas it is slow and sporadic in the second system with lower water content and K/Al ratio. Ultimately, these differences in the kinetics lead to the formation of two distinctly different patterns of crystal-size distribution, with a large number of small nanocrystals in the first sample and fewer large crystals in the second sample. The new findings put zeolite crystal growth on a rational basis that would enable the control of zeolite crystal size in similar organic-template-free systems.     

Recent developments in X-UV optics and X-UV diagnostics

Metrology of XUV beams (X-ray lasers, high-harmonic generation and VUV free-electron lasers) is of crucial importance for the development of applications. We have thus developed several new optical systems enabling us to measure the optical properties of XUV beams. By use of a Michelson interferometer working as a Fourier-transform spectrometer, the line shapes of different X-ray lasers have been measured with a very high accuracy (/10^-6). Achievement of the first XUV wavefront sensor has enabled us to measure the beam quality of laser-pumped as well as discharge-pumped X-ray lasers. A capillary discharge X-ray laser has demonstrated a very good wavefront allowing us to achieve an intensity as high as 3×10¹⁴ Wcm^-2 by focusing with a f=5 cm mirror. The sensor accuracy has been measured using a calibrated spherical wave generated by diffraction. The accuracy has been estimated to be as good as /120 at 13 nm. Commercial developments are underway. At Laboratoire dOptique Appliquée, we are setting up a new beamline based on high-harmonic generation in order to start the femtosecond, coherent XUV optic . PACS 07.85.Nc;32.70.Jz;41.50.+h;42.15.Dp;42.55.Vc;52.70.La     

LCEC-determination of urinary normetanephrine, metanephrine and 3-methoxy-tyramine

Summary A specific and sensitive analysis of urinary normetanephrine (NMN), metanephrine (MN) and 3-methoxy-tyramine was performed using reversed phase high-performance liquid chromatography coupled with an electrochemical detector. Spectrophotometric methods are insensitive in the normal and low abnormal ranges. The catecholamine method employed, is based on a modification of BioRad Laboratories procedure [1] and the method of Shoup and Kissinger [2]. Utilizing a single cation-exchange resin, the catecholamines are eluted with boric acid and purified by adsorption on alumina. The metanephrines are separated from other urinary constituents by elution with ammonia from the same chromatographic column. The recovery average was 74% for normetanephrine, 65% for metanephrine and 78% for 3-methoxy-tyramine of added standards. The quantitative detection based on electrochemical reactivity provides a simple and accurate analytical technique for routine application.

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LCEC-Bestimmung von Normetanephrin, Metanephrin und 3-Methoxy-tyramin in Harn

Zusammenfassung Eine spezifische und empfindliche Bestimmung der genannten Verbindungen wurde mit Hilfe der Umkehrphasen-HPLC mit elektrochemischer Detektion durchgeführt. Spektralphotometrische Verfahren sind für normale und niedrigere Gehalte nicht geeignet. Das benutzte Catecholaminverfahren beruht auf einer Modifikation der Methode der BioRad Laboratories [1] und des Verfahrens nach Shoup u. Kissinger [2]. Mit Hilfe eines Kationenaustauschers werden die Catecholamine abgetrennt, mit Borsäurelösung eluiert und an Aluminiumoxid gereinigt. Die Metanephrine werden durch Elution mit Ammoniaklösung abgetrennt. Die durchschnittliche Wiedergewinnung betrug 74% für Normetanephrin, 65% für Metanephrin und 78% für 3-Methoxy-tyramin. Die elektrochemische Detektion ermöglicht eine einfache Anwendbarkeit bei Routineuntersuchungen.

     

Observation of spinning sidebands in the Al magic-angle spinning nuclear magnetic resonance spectra of FAU and EMT structure-type zeolites

Wide-band (1 MHz) ²⁷Al magic-angle spinning nuclear magnetic resonance (MAS NMR) spectra were recorded for zeolite Y (Si/Al 2.7) and high-silica (Si/Al 3.8) FAU, EMT and mixed FAU-EMT structure-type zeolites synthesized using 15-crown-5 and/or 18-crown-6 ethers as templating agents. Spinning sidebands (related to first-order quadrupolar effects affecting satellite transitions) are observed in the spectra of the four calcined and fully rehydrated samples, reflecting a high symmetry of the framework aluminium atom surrounded by four oxygens. It is shown that the intensity of the spinning sidebands progressively increases after calcination and rehydration of the samples, indicating that the restoration of the high local order around the ²⁷Al nuclei is rather slow. On the other hand, second-order quadrupolar interactions rapidly decrease upon rehydration of the calcined samples which is achieved within one day, as indicated by thermogravimetry. Some hypotheses are proposed to explain such a difference, and the role of water is also discussed.