Improved measurement of Vub with inclusive semileptonic B decays

We report a new measurement of the Cabibbo-Kobayashi-Maskawa parameter Vub made with a sample of 9.7 x 10(6) BB- events collected with the CLEO II detector. Using heavy quark theory, we combine the observed yield of leptons from semileptonic B decay in the end-point momentum interval 2.2-2.6 GeV/c with recent CLEO II data on B-->X(s)gamma to find Vub = (4.08+/-0.34+/-0.44+/-0.16+/-0.24)x10(-3), where the first two uncertainties are experimental and the last two are from theory.     

2pi ambiguity-free optical distance measurement with subnanometer precision with a novel phase-crossing low-coherence interferometer

We report a highly accurate phase-based technique for measuring arbitrarily long optical distance with subnanometer precision. The method employs a Michelson interferometer with a pair of harmonically related light sources, one cw and the other low coherence. By slightly detuning (~2 nm) the center wavelength of the low-coherence source between scans of the target sample, we can use the phase relationship between the heterodyne signals of the cw and the low-coherence light to measure the separation between reflecting interfaces with subnanometer precision. As this technique is completely free of 2pi ambiguity, an issue that plagues most phase-based techniques, it can be used to measure arbitrarily long optical distances without loss of precision. We demonstrate one application of this technique, the high-precision determination of the differential refractive index.     

Two-dimensional high-resolution NMR spectra in matched B(0) and B(1) field gradients

In a recent publication we presented a method to obtain highly resolved NMR spectra in the presence of an inhomogeneous B(0) field with the help of a matched RF gradient. If RF gradient pulses are combined with "ideal" 90 degrees pulses to form inhomogeneous z rotation pulses, the line broadening caused by the B(0) gradient can be refocused, while the full chemical shift information is maintained. This approach is of potential use for NMR spectroscopy in an inhomogeneous magnetic field produced by an "ex-situ" surface spectrometer. In this contribution, we extend this method toward two-dimensional spectroscopy with high resolution in one or both dimensions. Line narrowing in the indirect dimension can be achieved by two types of nutation echoes, thus leading to depth-sensitive NMR spectra with full chemical shift information. If the nutation echo in the indirect dimension is combined with a stroboscopic acquisition using inhomogeneous z-rotation pulses, highly resolved two-dimensional correlation spectra can be obtained in matched field gradients. Finally, we demonstrate that an INEPT coherence transfer from proton to carbon spins is possible in inhomogeneous B(0) fields. Thus, it is possible to obtain one-dimensional (13)C NMR spectra with increased sensitivity and two-dimensional HETCOR spectra in the presence of B(0) gradients of 0.4 mT/cm. These schemes may be of some value for ex-situ NMR analysis of materials and biological systems.     

NaY zeolite as host for the selective heterogeneous oxidation of silanes and olefins with hydrogen peroxide catalyzed by methyltrioxorhenium

The methyltrioxorhenium(MTO)-catalyzed oxidation of silanes to silanols and the epoxidation of various olefins by aqueous 85% H(2)O(2) proceed in high yields and excellent product selectivities (no disiloxanes, diols) in the presence of the zeolite NaY. The oxidative species is located inside the 12-A supercages. This prevents the bimolecular condensation of the silanol to disiloxane by steric means and the Lewis-acid assisted hydrolysis of the epoxide to the diol.     

On the number of solutions of an algebraic equation on the curve , and a consequence for o-minimal structures

We prove that every polynomial of degree has at most zeros on the curve . As a consequence we deduce that the existence of a uniform bound for the number of zeros of polynomials of a fixed degree on an analytic curve does not imply that this curve belongs to an o-minimal structure.

     

Extracting power from the Amazon basin

Brazil's plans for scores of hydropower dams on rivers deep into the rain forest are discussed. Two dams have been built by 1988. Tucurui, already completed, generates 4000 megawatts (MW) of electricity from a 2430-square-kilometer forebay; when complete, its power plant will have a capacity of 7300 MW. Balbina which has been a problem to develop, is due to start operating this year, six years behind schedule; it will create a largely stagnant lake the size of Tucurui's, but will have a capacity of only 250 MW. Economic, social, and environmental issues that surround further projects are examined. Brazil's hopes of easing economic strain by installing more efficient equipment, implementing better industrial processes, and promoting conservation are discussed     

Natural product chemistry. Part 160. Synthesis of 8-, 9-, 10- and 11-methylacronycines to improve the cytostatic activity of acronycine

With the help of drug design, 8-, 9-, 10- and 11-methylacronycines 24, 25, 26 and 27 have been selected and synthesised to improve the cytostatic potency of acronycine ( 31 ). The condensation of phloroglucinol with 6-methylanthranilic acid gave 7-hydroxy-1,9-dimethyldibenzo[b,j][1,7]phenanthroline-8,14(5H,13H)-dione ( 32 ) as the main product.     

Physical adsorption of gases on energetically heterogeneous solids I. GeneralizedLangmuir equation and its energy distribution

A generalizedLangmuir equation is proposed for describing the monolayer adsorption of single gases on heterogeneous solids. The special cases of this equation are:Langmuir-Freundlich, Tóth andFreundlich type adsorption isotherms. The energy distribution function corresponding to this equation produces all types of simple energy distributions, i.e., symmetrical distribution, decreasing exponential distributions and asymmetrical distributions showing widening in the directions of low and high adsorption energies.

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Gasadsorption auf energetisch heterogenen Feststoffen, 1. Mitt.: Eine generalisierteLangmuir-Gleichung und ihre Energieverteilung

Zusammenfassung Es wird eine generalisierteLangmuir-Gleichung zur Beschreibung der einlagigen Adsorption eines einzelnen Gases auf heterogenen Feststoffen beschrieben. Die speziellen Fälle dieser Gleichung sind:Langmuir-Freundlich-, Tóth- undFreundlich-Typ der Adsorptionsisotherme. Die Energieverteilung, die dieser Gleichung entspricht, gibt alle Typen einer einfachen Verteilung wieder, z. B. eine symmetrische Verteilung, eine abfallende exponentielle Verteilung und asymmetrische Verteilungen mit Erweiterung in die Richtung von niedriger oder hoher Adsorptionsenergie.

     

Determination of small amounts of lead in uranium

Small amounts of lead in the presence of large amounts of uranium can be determined by complexing the lead with nitrilotriacetic acid in aqueous solution at about pH 6 (adjusted with hexamine)and extracting the uranium into a chloroform solution of diphenylacetic acid. The aqueous phase is then acidified the lead determined polarographically.