Search Results

You are looking at 1 - 10 of 46 items

  • Author: M. Zimmermann x
Clear All Modify Search

Using the level-crossing technique the following relations between the hyperfine structure constant A and the gj value of the (5p6s)3P1 0-term were determined for both the stable isotopes Sn117 and Sn119:

A117 = — 159,57(4) mK · gJ/1,380; A119 = — 167,01(4) mK · gJ/1,380.

From the width of the level-crossing signal a mean lifetime τ = 4,5(7) · 10-9 sec was deduced.

Rotation of single cells (mesophyll protoplasts of Avena sativa) induced by a planar, homogeneous rotating field has been observed at a frequency of 20-40 kHz (conductivity of the external mannitol solution 6x 10-5 Ω-1 cm-1). This variation in optimum frequency is largely due to an inverse dependence on cell radius. Rotation direction is opposite to that of the field, and can be reversed at will by reversing the field. The maximum speed of cell spinning was a few cycles per second (and thus always much slower than that of the field) and was proportional to the square of the amplitude of the field.

The rotation of a single cell in a rotating field is expected on the basis of the dipole-dipole theory developed by Holzapfel et al., (J. Membrane Biol. 67, 1-14 (1982)), for multi-cell rotation. Measurements of the dependence of optimum applied field frequency on medium conductivity indicate that the dipole is generated by interfacial (Maxwell-Wagner) polarization. The required frequency is a linear function of the conductivity of the external solution. This relationship is used to derive a value for the specific membrane capacitance. Further applications of this technique for cell and membrane research are discussed.

Abstract

We have studied the anisotropic optical properties of binary NbO2.5-δ (0 < δ ≤ 0.083) and ternary Nb18-εW8+εO69 (ε = 0, 1,..., 9) compounds using the polarized regular-reflection method. We observed strong anisotropic behaviour for all reduced phases. The anisotropic effect can be related to the crystallographical structure principle and to the doping of charge carriers by the reduction of oxygen (δ) or substitution of W for Nb (ε) in the binary and ternary oxides, respectively. Our results indicate that the charge carriers are confined to the structural block units. For increasing δ and ε, metal-like properties occur (δ≥ 0.1, ε > 8) in the infinite block direction only.

Official Journal of the World Association of Perinatal Medicine

Auf Grund von Untersuchungen der frühen Embryonalentwicklung nach Besamung der Eier mit arteigenen und artfremden Spermien, durch die Feststellung der Zellteilungsraten und durch Experimente, in denen sich ein Gen des individuellen Genoms bei der Sonderung des axialen, paraxialen, intermediären und lateralen Mesoderms manifestiert, wird ein allgemeines Entwicklungsschema aufgestellt.