The structure of single vortices in type II superconductors

This paper reports the first results of a program for the investigation of the detailed electronic and magnetic structure of type II superconductors. The structure of a single flux bundle or vortex in an infinite superconducting specimen is investigated, assuming weak coupling and a spherical Fermi surface of the material. The equations governing the gap parameterΔ(r) and the vector potentialA(r) are suitably scaled and simplified using the symmetry of the system. These equations can be solved numerically only; for their solution the asymptotics ofΔ(r) andA(r) far from the center of the vortex are required. These asymptotics are derived here by properly linearising the equations; they are found to be of the typer ^?1/2 exp (?r/rin0) wherer ₀ is determined by temperature and material parameters. Implicit equations forr ₀ are derived and discussed. We find that for materials withκ-values less than 1.7 (e.g. pure niobium)r ₀ becomes complex at low temperatures; i.e. the deviation ofΔ(r) andA(r) from their values at infinity is a damped oscillation as function ofr.     

The structure and synthesis of xanthomicrol

Xanthomicrol is shown to be 5,4′-dihydroxy-6,7,8-trimethoxyflavone by a combination of physical and degradative methods. Its synthesis from pentamethoxybenzene is described.     

New spectrometric method for the determination of trace elements in petroleum by double plasma arc source in a graphite tube

Summary A method is described for the determination of trace elements (V, Mo, Ni, Co, Mn, Ag, Be, Sn, Ga, In, Cr) in petroleum, using a double plasma arc source in a graphite tube. The sample is mixed with graphite powder in the ratio 14, heated to 220° C, mixed with 6% NaCl and loaded into graphite electrodes. Petroleum of different origin was successfully analysed (standard deviation 7–11%; limit of detection 0.003 –0.1 ppm).

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Neues Verfahren zur spektrometrischen Bestimmung von Spurenelementen in Erdöl mit Hilfe eines doppelten Plasmabogens im Graphitrohr

Zusammenfassung Bei dem Verfahren wird die Probe im Verhältnis 14 mit Graphit vermischt, auf 220° C erhitzt, mit 6% NaCl versetzt und in Graphitelektroden gegeben. Erdöl verschiedenen Ursprungs wurde mit dem Verfahren analysiert (Standardabweichung 7–11%; Nachweisgrenze 0,003–0,1 ppm). Folgende Spurenelemente wurden erfaßt: V, Mo, Ni, Co, Mn, Ag, Be, Sn, Ga, In, Cr.

     

Eigenwerte gedämpfter Schwingungen bei Gültigkeit der Bequemlichkeitshypothese

Übersicht Behandelt wird die lincare Matrizendifferentialgleichung zweiter Ordnung Mü + Dü + Ce = o mit der Besonderheit D = M + C als sogenannter Bequemlichkeitshypothese. Es wird gezeigt, daß sämtliche Eigenwerte, sofern sie komplex ausfallen, auf einem Kreis in der komplexen Zahlenebene liegen, der durch die beiden Parameter und festgelegt ist. Auch für die rcellen Wurzeln wird cin einfaches Verteilungsgesetz angegeben. Die Verhältnisse lassen sich lcicht übertragen auf lineare gedämpfte Schwingungssysteme mit belicbig vielen Ercihcitsgradcn.

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Summary The matrix differential equation Mü + Dü + Ce = o of an N-degree-of-freedom linear dynamic system with viscous damping may have the special property D = M + C. For this case it is shown that the complex eigenvalues are situated on a circle in the complex -plane, determined by the parameters and . For the real roots a simple presentation in the -plane is given. An extension to continuous systems is possible.

     

High speed, high capacity ATM optical switches for futuretelecommunication transport networks

This paper describes the work carried out in the RACE Project R2039 ATMOS (asynchronous transfer mode optical switching). The project is briefly illustrated, together with its main goal: to develop and assess concepts and technology suitable for optical fast packet switching. The project's technical approach consisted in the exploitation of the space and wavelength domains for fast routing and buffering: The major achievements are then reported. Four different switch architecture concepts have been proposed, investigated and developed, all based on a high speed optical routing matrix electrically controlled at lower speed. The basic optical key components and subsystems (wavelength converters, space switches and optical buffers) are described in detail, with the outstanding results obtained and the corresponding projected performance. In particular, system demonstration of wavelength conversion at 10 and 20 Gb/s has been realized, to show the usefulness of the ATMOS technology both to implement optimized high performance optical packet-switching fabrics as well as transparent optical circuit-routing nodes. Four rack-mounted, reduced size demonstrators of basic switching matrices have been designed and implemented scalable to real system sizes. The obtained good results in terms of bit error rate and hardware integration are reported, showing that ATM switches are feasible with state of-the-art optical technology     

Spectroscopic studies of 37,39K using the 40,42Ca(p, α) reactions

The ⁴⁰Ca(p, α) ³⁷K reaction has been studied at 42.5 MeV bombarding energy with an overall energy resolution of 45 keV. Excitation in ³⁷K was observed for the 0.00 MeV, $\text{3}\text{2}{}^{\mathrm{+}}\text{; 1.37}\text{MeV}\text{,}\text{1}\text{2}{}^{\mathrm{+}}\text{; 2.28}\text{MeV}\text{; 2.75}\text{MeV}\text{,}\text{5}\text{2}{}^{\mathrm{+}}\text{; 3.25, 4.69, 5.69, 6.05, 7.00, 7.32}\text{and}\text{7.84}\text{MeV}$ states. No known negative parity states are populated in ³⁷K via the (p, α) reaction, closely resembling the features observed in the ³⁹K(p, t)³⁷K reaction. Results of this reaction and the previously investigated ⁴²Ca(p, α)³⁹K reaction are used in a combined analysis, with emphasis on a comparison of the relative strengths of states populated in these two reactions. Core excitation, which is known to be important in the Ca nuclei, plays an important part in understanding the strengths of the observed transitions. Microscopic three-nucleon form factors were calculated for all transitions of interest, and the normalizations of these form factors used in extracting the relative strengths from zero range DWBA calculations. Simple configurations for the transferred nucleons are assumed in this comparison, in an attempt to explain the main features of the (p, α) reaction.