Transporteigenschaften von 9 bin?ren und 2 tern?ren Mischungen von Gasen bei niederer Dichte

Ohne Zusammenfassung     

Components of superspace

We give the explicit superspace form of the newly discovered tensor calculus for the chiral multiplet [1].     

Sesquiterpenester aus Euonymus europaeus L.

Aus Euonymus europaeus L. wurden 5 Sesquiterpenester isoliert, die sich vom 8-epi-Desoxymaytol bzw. vom 7β-Hydroxy-3,4-didesoxy-8-epi-maytol ableiten.     

Acoustic streaming induced by ultrasonic flexural vibrations and associated enhancement of convective heat transfer

Acoustic streaming induced by ultrasonic flexural vibrations and the associated convection enhancement are investigated. Acoustic streaming pattern, streaming velocity, and associated heat transfer characteristics are experimentally observed. Moreover, analytical analysis based on Nyborg's formulation is performed along with computational fluid dynamics (CFD) simulation using a numerical solver CFX 4.3. Two distinctive acoustic streaming patterns in half-wavelength of the flexural vibrations are observed, which agree well with the theory. However, acoustic streaming velocities obtained from CFD simulation, based on the incompressible flow assumption, exceed the theoretically estimated velocity by a factor ranging from 10 to 100, depending upon the location along the beam. Both CFD simulation and analytical analysis reveal that the acoustic streaming velocity is proportional to the square of the vibration amplitude and the wavelength of the vibrating beam that decreases with the excitation frequency. It is observed that the streaming velocity decreases with the excitation frequency. Also, with an open-ended channel, a substantial increase in streaming velocity is observed from CFD simulations. Using acoustic streaming, a temperature drop of 40 degrees C with a vibration amplitude of 25 microm at 28.4 kHz is experimentally achieved.     

Broadband quasi-phase-matched second-harmonic generation in MgO-doped periodically poled LiNbO_3 at the communications band

A novel scheme for broadband second-harmonic generation was developed with type I quasi phase matching by use of an off-digital nonlinear optical coefficient d(31) . This was achieved by matching of the group velocities of the second harmonic and the fundamental, while the phase velocities were quasi phase matched. The desired group-velocity dispersion could be obtained with LiNbO(3) doped with 5 mol. % of MgO. Efficient second-harmonic generation with a bandwidth of 52 nm was obtained for the fundamental wavelength centered at 1566 nm in MgO-doped periodically poled LiNbO(3) , compared with a bandwidth of 1.3 nm for the conventional scheme using d(33) . Efficient frequency doubling of an ultrafast pulse is expected without group-velocity walk-off or pulse distortion.     

Turtschamide,a cytotoxic putrescine bisamide from Corydalis turtschaninovii

A putrescine bisamide with a unique cyclic structure derived from l-tyrosine, turtschamide (1), was isolated from the tubers of Corydalis turtschaninovii. The structure of 1 was established by extensive spectroscopic study, and its absolute configuration was determined by a combination of NOE experiment and application of the Marfey’s method. Turtschamide (1) exhibited cytotoxicity against the A549, SK-OV-3, SK-MEL-2, and HCT-15 cells.     

Melting process with solid-liquid density change and natural convection in a rectangular cavity

This paper presents a numerical method that simulates the melting process in the presence of solid-liquid density change and natural convection in the melt. The physical model concerned is two-dimensional melting of a phase-change material, initially at its fusion temperature, charged in a rectangular cavity with isothermally heated side walls and an adiabatic bottom wall. The presence of the density change brings no change into the basic form of governing equation, so it is considered through the reformulation of boundary conditions. Difficulties associated with the complex time-dependent melt region, whose shape is also a part of the solutions, are overcome by employing the boundary-fitted coordinate system. Comparison with other works validates the present numerical model and reveals the effects of density change qualitatively. Also, it is confirmed that the present method is preferable to others with natural convection only. Computed results for interesting cases are shown in forms of transient position of the interface, temperature distribution, flow pattern, heat transfer coefficient, and melting fraction as a function of time. Closer examination on melting patterns allows a correlation to be made between the melting fraction and a new independent variable Ste·Fo·Ra^1/4.