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101.
Th. Schalkhammer Ch. Lobmaier F. Pittner A. Leitner H. Brunner F. R. Aussenegg 《Mikrochimica acta》1995,121(1-4):259-268
A new optical sensor is presented, based on the analyte reaction resulting in swelling and shrinking of a thin polymer layer. Changing the concentration of ions in a new bisazide photo-cross-linked poly(vinylpyrrolidone) polymer results in a concentration-dependent volume change of the hydrated gel. The volume response of the sensor induced by different ions is fully reversible over more than 250 cycles. The response of the device depends on the type, the charge and the concentration of the ions. The sensor material is part of an optical thin film system which transforms the variations in volume of the polymer into spectral information. The steady state of the sensor response is obtained within 60 s. The response time is mainly limited by the pump rate, the back pressure and the total volume of the system but not by the swelling of the sensor polymer. A comparative study of ion effects has demonstrated a fundamental correlation of the polymer swelling properties with the Hofmeister series of chaotropic agents. Thus it is concluded that the photopolymer, which is solubilized in aqueous solutions by the interaction of its amide structure with the solvent, behaves like the backbone amide structure of proteins. 相似文献
102.
A Contribution on Ba3Pt4HgO11: The First Alkaline-Earth Oxoplatinate(II,V)/Oxomercurate Single crystals of Ba3Pt4HgO11 were prepared by oxygen high pressure technique (4 200–3 600 bar) and investigated by X-ray methods. It crystallizes with hexagonal symmetry, space group D? P6 2c, a = 6.021, c = 17.374 Å, Z = 2. Ba3Pt4HgO11 represents a new structure type, showing structural relationships to Ba2Hg3Pd7O14 and to the precious metal 6L-perovskites. The Hg2+ ions show dumb-bell like coordination, Pt2+ a square-planar surrounding and Pt5+ face shared double octahedra. 相似文献
103.
CdHgO2: An Oxomercurate related to the Crednerite Structure Single crystals of CdHgO2 were prepared by oxygen high pressure technique (600°C, 3900 bar) and investigated by X-ray technique. It crystallizes with monoclinic symmetry, space group C–C2/m; a = 5.933, b = 3.452, c = 5.875 Å, β = 91.26°; Z = 2. The Hg2+ ions show dumb-bell like coordination, Cd2+ an octahedral one. CdHgO2 shows strong relationship to the Crednerite structure. The orientation of the O? Hg? O dump-bells to the CdO6 octahedra layers is discussed with respect to related oxomercurates. 相似文献
104.
The Boussinesq approximation, where the viscosity depends polynomially on the shear rate, finds more and more frequent use in geological practice. In the paper, this modified Boussinesq approximation is investigated as a dynamical system for which the existence of a global attractor is proved. Finally, a new criterion for estimating the fractal dimension of invariant sets is formulated and its application to the problem under consideration is illustrated. 相似文献
105.
106.
A. Kratzer K. Mutzbauer S. Henneberger G. M. Kalvius O. Hartmann R. Wäppling H. -H. Klauß M. A. C. De Melo F. J. Litterst Th. Stammler 《Hyperfine Interactions》1994,87(1):1055-1061
The high pressureSR spectrometer [1] formerly located at CERN has been transferred to theE1-beamline at PSI and put back into operation with only minor modifications. The essential features of the high pressure apparatus are described below. The instrument covers a pressure range up to 0.7 GPa which can be extended to 1.4 GPa depending on the design of the high pressure cell. First measurements at PSI were successfully carried out with a single crystalline sample of Gd metal. New developments in high pressure cell design are presented. They are expected to further improve the signal/background ratio and to extend the pressure range to 1 GPa. One type of cell will allow temperatures above 380 K.This work was supported by the German Federal Minister for Research and Technology (Bundesminister für Forschung und Technologie [BMFT]) under Contract Nr. 03KA2-TUM-4 and 03SE3STU. 相似文献
107.
Morenzoni E. Birke M. Hofer A. Kottmann F. Litterst J. Matthias B. Meyberg M. Niedermayer Ch. Prokscha Th. Schatz G. Wutzke Th. 《Hyperfine Interactions》1996,97(1):395-406
During the last few decades, a variety of methods has been developed which makes use of polarized positive muons as a microscopic probe of the magnetic properties of condensed matter (muon spin rotation, relaxation, resonance,SR). Until now, available beams for SR studies have delivered 100% polarized muons with energies in the MeV range, resulting in a deep penetration of the muons into the sample material under investigation. This presently limits the applications of theSR technique to the study of the bulk characteristics of matter. To be able to control the implantation depth, a very low energy beam of polarized muons is being developed at the Paul Scherrer Institute. Very slow polarized muons (kinetic energy 10 eV, polarization 90%) are obtained from the moderation of a high energy muon beam in a thin film of an appropriate condensed gas. These muons can be used as a source for a beam of tunable energy between a few tens of eV and some tens of keV. Implantation depths in the range of few to a few hundreds of nanometers can thus be achieved by varying the energy. 相似文献
108.
P. Brüesch F. Stucki Th. Baumann P. Kluge-Weiss B. Brühl L. Niemeyer R. Strümpler B. Ziegler M. Mielke 《Applied Physics A: Materials Science & Processing》1993,57(4):329-337
In this contribution we have studied the key electrical parameters of silica aerogels and of silica-aerogel-based composites, namely the dielectric constants , the dielectric losses tan (at 1 kHz), and the breakdown fields E
b (at 50 Hz). For low-density bulk silica aerogels we find =1.25 and tan =0.0005. E
b is about 500 kV/cm in quasi-homogeneous fields, and of the order of MV/cm in strongly inhomogeneous fields. The dielectric constants of partially densified aerogels increase linearly with density; their dielectric losses are relatively large and their breakdown fields are comparativiely low. The same results are found for aerogels in the form of settled materials, i.e. aerogel granules and powders in air. Acrylate-based aerogel composites with volume fractions larger than 70% have low dielectric constants but their losses are at least 10 times higher than those of low-density aerogels. These materials sustain high local fields in the MV/cm region, while in quasihomogeneous fields, breakdown occurs at about 100 kV/cm. Based on the present results and the interplay with other physical properties (low mechanical resistance, low thermal conductivity, adsorption of water, etc.), silica aerogels and silica aerogel-acrylate-based composites are predicted to have a low potential for electrical insulation. 相似文献
109.
E. Brézin E. Korutcheva Th. Jolicoeur J. Zinn-Justin 《Journal of statistical physics》1993,70(3-4):583-598
Prompted by a recent article of Chakravarty, we reexamine theO(N) vector model with twisted boundary conditions ind dimensions in the various frameworks of the =d–2 expansion, the =4–d expansion, and the large-N expansion. These continuum models describe the physics below the critical temperatureT
c and nearT
c of a latticeO(N) spin model. We determine the effect of the twisting on finite-size scaling functions, for various geometries.On leave from G. Nadjakov Institute of Solid State Physics, 1784 Sofia, Bulgaria. 相似文献
110.