Sound propagation in metallic glasses—a new look at the tunneling model

A variety of amorphous metals exhibit a characteristic behavior in their acoustic properties at low frequencies which differs from the predictions of the standard tunneling model. We point out that a lower cut-off _min for the tunnel matrix element, which is needed for consistency of the tunneling model, leads to an upper bound on relaxation times induced by the conduction electrons. We derive explicit expressions for the velocity shift and internal friction for the normalconducting and superconducting case. It is shown that a maximum relaxation time plays an essential role at audio frequencies. The corresponding change of the acoustic properties is in qualitative agreement with vibrating reed experiments.     

Optimal control of open quantum systems: cooperative effects of driving and dissipation

We investigate the optimal control of open quantum systems, in particular, the mutual influence of driving and dissipation. A stochastic approach to open-system control is developed, using a generalized version of Krotov's iterative algorithm, with no need for Markovian or rotating-wave approximations. The application to a harmonic degree of freedom reveals cooperative effects of driving and dissipation that a standard Markovian treatment cannot capture. Remarkably, control can modify the open-system dynamics to the point where the entropy change turns negative, thus achieving cooling of translational motion without any reliance on internal degrees of freedom.     

Influence of interparticle interactions on the kinetics of self-assembly and mechanical strength of nanoparticulate aggregates

Computer simulations based on Discrete Element Method have been performed in order to investigate the influence of interparticle interactions on the kinetics of self-assembly and the mechanical strength of nanoparticle aggregates.Three different systems have been considered.In the first system the interaction between particles has been simulated using the JKR (Johnson,Kendall and Roberts) contact theory,while in the second and third systems the interaction between particles has been simulated using van der Waals and electrostatic forces respectively.In order to compare the mechanical behaviour of the three systems,the magnitude of the maximum attractive force between particles has been kept the same in all cases.However,the relationship between force and separation distance differs from case to case and thus,the range of the interparticle force.The results clearly indicate that as the range of the interparticle force increases,the self-assembly process is faster and the work required to produce the mechanical failure of the assemblies increases by more than one order of magnitude.     

TIME-RESOLVED RESONANCE RAMAN STUDIES ON THE PHOTOCHEMICAL CYCLE OF BACTERIORHODOPSIN

Abstract— Kinetic resonance Raman (RR) experiments were designed to study the time-behaviour of the retinal-binding protein bacteriorhodopsin (BR) in its photochemical cycle. The unphotolyzed chro-mophore B-570 and the two intermediates L -550 and M-412 were probed by the characteristic C=C stretching vibrations of the retinal moiety. Time resolution was achieved with a spinning cell as flow system in combination with two CW lasers in a pump-probe configuration. RR spectra were probed at 475 nm at various delay times between pump and probe event. The deconvolution of the spectra into the various components B-570, L-550 and M-412 was carried out by curve fitting procedures. It was found that at pH7.4 L-550 decays — with a time-constant of 62 μs — not completely but to a residual level of 35% of its initial value. This intermediate L -amplitude finally disappears in the ms-range (4.5 ms) synchroneously with the intermediate M -412. An analogeous time-behaviour was found at pH 4.6. In the basic range also an " L " -intermediate could be identified which is coupled to the long-lived M-component. To explain the peculiar time-dependence it is proposed that during the fast decay of L a dynamic equilibrium between L and M is established. Then during the reconstitution of B -570 the two intermediates disappear synchroneously. A molecular model is presented in which the dynamic equilibrium between L and M is explained by an oscillatory motion of a proton from the Schiff base group of the chromophore to its counterion.     

JT-60U装置温度分布剖面不变性的实验研究

在一系列H模放电条件下，建立了一个旨在研究等离子体温度分布剖面不变性的数据库。介绍了数据库建立过程中要解决的关键问题和所用软件，对等离子体温度分布剖面不变性及芯部约束与边缘参数的关系进行了研究。     

Negative differential conductance induced by spin-charge separation

Spin-charge states of correlated electrons in a one-dimensional quantum dot attached to interacting leads are studied in the nonlinear transport regime. With nonsymmetric tunnel barriers, regions of negative differential conductance induced by spin-charge separation are found. They are due to a correlation-induced trapping of higher-spin states without magnetic field and are associated with a strong increase in the fluctuations of the electron spin.     

Raman-Spektroskopie von Festk?rpern mit LASER-Lichtquellen

Zusammenfassung Eine einfache photographische Anordnung zur Aufnahme der Raman-Spektren farbiger Kristallpulver durch Anregung mit einem Rubin-Laser wird beschrieben. Beispiele zeigen die Anwendungsmöglichkeiten für StrukturaufklÄrungen. Der He-Ne-Gas-Laser eignet sich für die Aufname der Raman-Spektren von Einkristallen, dies ist am Beispiel der bei niedrigen Raman-Frequenzen neben der Erregerlinie auftretenden Gitterschwingungen gezeigt. Auch die photoelektrische Registrierung der Spektren ist möglich.

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Summary A simple photographic technique for the Raman spectroscopy of coloured crystal powders, excited by a ruby LASER, is described. Examples show applications of this technique for the determination of molecular structures.For the Raman spectroscopy of mono-crystals the He-Ne-gas LASER is suitable. As an example Raman lines near the exciting line originating from lattice vibrations have been photographed. Photoelectric recording of the spectra is also possible.

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Herrn Prof. Dr., Dr. h. c. W. Klemm zum 70. Geburtstag gewidmet.

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Herrn Prof. Dr. H. A. Staab, Heidelberg und Herrn Dr. Blanck, Mülheim/Ruhr, danken wir für die überlassung von Substanzen (Abb. 2d, f; 2b).

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Wir danken Herrn Prof. Dr. H. Kaiser für Anregungen und DiskussionsbeitrÄge. Der Deutschen Forschungsgemeinschaft und dem Landesamt für Forschung, Nordrhein-Westfalen danken wir für die überlassung von Sachmitteln.     

Performance of slotted pores in particle manufacture using rotating membrane emulsification

This paper addresses the use of different slotted pores in rotating membrane emulsification technology.Pores of square and rectangular shapes were studied to understand the effect of aspect ratio (1-3.5) and their orientation on oil droplet formation.Increasing the membrane rotation speed decreased the droplet size,and the oil droplets produced were more uniform using slotted pores as compared to circular geometry.At a given rotation speed,the droplet size was mainly determined by the pore size and the fluid velocity of oil through the pore (pore fluid velocity).The ratio of droplet diameter to the equivalent diameter of the slotted pore increased with the pore fluid velocity.At a given pore fluid velocity and rotation speed,pore orientation significantly influences the droplet formation rate: horizontally disposed pores (with their longer side perpendicular to the membrane axis) generate droplets at double the rate of vertically disposed pores.This work indicates practical benefits in the use of slotted membranes over conventional methods.