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21.
Manfred Einsiedler Douglas Lind 《Transactions of the American Mathematical Society》2004,356(5):1799-1831
We investigate algebraic -actions of entropy rank one, namely those for which each element has finite entropy. Such actions can be completely described in terms of diagonal actions on products of local fields using standard adelic machinery. This leads to numerous alternative characterizations of entropy rank one, both geometric and algebraic. We then compute the measure entropy of a class of skew products, where the fiber maps are elements from an algebraic -action of entropy rank one. This leads, via the relative variational principle, to a formula for the topological entropy of continuous skew products as the maximum of a finite number of topological pressures. We use this to settle a conjecture concerning the relational entropy of commuting toral automorphisms.
22.
B.?Granqvist A.?Helminen M.?Vehvil?inen V.???ritalo J.?Sepp?l? M.?LindénEmail author 《Colloid and polymer science》2004,282(5):495-501
A mixture of triethoxysilanefunctionalized poly(ethylene glycol), f-PEG, and tetraethoxysilane, TEOS, was used as precursors in the preparation of continuous hybrid f-PEG-siloxane sol–gel derived fibers. The fibers were spun by extrusion through a spinneret. The thus prepared fibers had a diameter of 20–50 m. 29Si-CPMAS NMR measurements confirmed that the functionalized PEG is incorporated into the siloxane network through covalent bonds. The hybrid fiber elasticity was much higher than that of fibers spun from sols with TEOS as the only source for silica. However, the f-PEG chain length plays a crucial role for the spinnability of the sol, since, as a result of bridging flocculation, macroscopic phase separation occurred readily with increasing chain length of the f-PEG. The fibers were shown to be effective substrates for the nucleation and growth of bone-like hydroxyapatite. 相似文献
23.
K. Pretzl G. Ambrosini R. Arsenescu C. Baglin H. P. Beck K. Borer A. Bussière K. Elsener Ph. Gorodetzky J. P. Guillaud P. Hess S. Kabana R. Klingenberg G. Lehmann T. Lindén K. D. Lohmann R. Mommsen U. Moser K. Pretzl J. Schacher R. Spiwoks F. Stoffel J. Tuominiemi M. Weber 《Acta Physica Hungarica A》2001,14(1-4):297-308
Besides the dedicated search for strangelets NA52 measures light (anti)particle and (anti)nuclei production over a wide range of rapidity. Compared to previous runs the statistics has been increased in the 1998 run by more than one order of magnitude for negatively charged objects at different spectrometer rigidities. Together with previous data taking at a rigidity of ?20 GeV/c we obtained $10^6 \bar p, 10^3 \bar d$ and two $\overline {^3 He} $ without centrality requirements. We measured nuclei and antinuclei (p, d, $\bar p,\bar d$ ) near midrapidity covering an impact parameter range of b ~ 2–12 fm. Our results strongly indicate that nuclei and antinuclei are mainly produced via the coalescence mechanism. However, the centrality dependence of the antibaryon to baryon ratios shows that antibaryons are diminished due to annihilation and breakup reactions in the hadron dense environment. The volume of the particle source extracted from coalescence models agrees with results from pion interferometry for an expanding source. The chemical and thermal freeze-out of nuclei and antinuclei appear to coincide with each other and with the thermal freeze-out of hadrons. 相似文献
24.
B. Lind C. -G. Elinder L. Friberg B. Nilsson M. Svartengren M. Vahter 《Fresenius' Journal of Analytical Chemistry》1987,326(7):647-655
Summary An extensive quality control programme has been developed within a global UNEP/WHO project on Assessment of Exposure to Lead and Cadmium through Biological Monitoring. This project was coordinated by the Karolinska Institute (Department of Environmental Hygiene) and the National (Swedish) Institute of Environmental Medicine. The project was carried out within the framework of UNEP's Global Environmental Monitoring System (GEMS) and was initiated in 1978 on the basis of recommendations from a UNEP/WHO meeting of a Government Expert Group on Health-Related Monitoring.On termination of the project in 1981 it was decided to extend the analytical QC assurance programme on a periodic basis in order to maintain the analytical capability of the participating laboratories. A QC programme was conducted by our Institute in a follow-up study of the above mentioned UNEP/WHO programme and for a National Swedish Board of Occupational Safety and Health project, as well as for a recently concluded project in which a decrease in bloodlead levels in residents of Stockholm for the period 1980–1984 was established.In the latter project decreased blood-lead levels of about 20% were found in samples stored frozen (–20 ° C) for 4 years. This finding stimulated a study of the long-term stability of our QC samples. Results of lead and cadmium analyses performed for each QC sample during 1980–1985 were computerized. The results showed that the QC samples appeared to be stable for 2–3 years when stored at –20 °C. The losses of cadmium were 5 –10% in 5–6 years of storage at –20 ° C and seem to be less than those of lead (7–15%). Analysis of several QC sets, prepared on different occasions, but analyzed on the same day, confirmed that losses occur. 相似文献
25.
Douglas Lind 《Proceedings of the American Mathematical Society》2005,133(5):1411-1416
We formulate Lehmer's Problem concerning the Mahler measure of polynomials for general compact abelian groups, introducing a Lehmer constant for each such group. We show that all nontrivial connected compact groups have the same Lehmer constant and conjecture the value of the Lehmer constant for finite cyclic groups. We also show that if a group has infinitely many connected components, then its Lehmer constant vanishes.
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The humidity and water tolerance of a sol-gel derived binder prepared using a cheap, multicomponent precursor has been studied.
The sol was prepared by dissolving the precursor in water under acidic conditions using either formic acid or a mixture of
formic acid and citric acid for pH adjustments. It is shown that a post-treatment temperature of 400 °C or higher is needed
in order to achieve full binder stability under excess water conditions, as thermal decomposition of metal carboxylates leads
to a pronounced decrease in water solubility of the gels. The mesoporous gel can be made hydrophobic by post-treatments with
either a silane or an organophosphonate, showing that both silica and metal oxides are exposed on the surface of the binder.
Surface functionalization is especially effective for gels heat-treated at higher temperatures where the metal carboxylates
have decomposed to the corresponding oxides or carbonates. The results are expected to be of great importance for the use
of this cheap binder in large scale industrial applications.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
29.
I. Tittonen J. Hietaniemi J. Huttunen T. Karlemo M. Karppinen T. Katila J. Lindén L. Niinistö K. Ullakko 《Hyperfine Interactions》1990,55(1-4):1405-1409
The influence of sintering temperatures and nominal starting compositions on the phase contents of polycrystalline Bi2Sr2Ca n-1Cu n O4+2n samples are reported. After every sintering the samples were characterized with X-ray diffraction and magnetic AC susceptibility measurements. For Mössbauer studies, in each case also a corresponding specimen containing57Fe was synthetized. The identification of various superconducting Bi2Sr2Ca n-1Cu n O4+2n phases on the basis of Mössbauer spectra consisting usually of three quadrupole doublets is discussed. 相似文献
30.