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P. Kubeš J. Kravárik D. Klír P. Barvir M. Scholz M. Paduch K. Tomaszewski I. Ivanova-Stanik B. Bieńkowska L. Karpinski L. Juha J. Krása M. J. Sadowski L. Jakubowski A. Szydłowski A. Banaszak H. Schmidt V. M. Romanova 《Plasma Physics Reports》2005,31(5):382-391
Results are presented from experimental studies of the correlation between X-ray and neutron emissions generated in the implosion of a deuteron plasma shell onto an Al wire. The experiments were carried out on the PF-1000 facility at currents of 1.5–1.8 MA. An Al wire 80 μm in diameter and 7–9 cm in length was placed at the end of the inner electrode. During the implosion of the plasma shell, Al K-shell X-rays were first emitted at the dip of the current derivative. After the X-ray pulse, a relatively stable corona with a diameter of 2–3 mm and lifetime of a few hundred nanoseconds formed around the wire. The presence of the wire did not considerably reduce the total neutron yield (at most 1011 neutrons per shot) in comparison to discharges without a wire. As a rule, the intensity of neutron emission was maximal a few tens of nanoseconds after the peak of X-ray emission. A detailed comparison of two shots with low and high neutron yields have shown that the neutron yield depends on the configuration and dynamics of the discharge. The possible influence of the self-generated axial component of the magnetic field on the development of the plasma focus and the acceleration of fast deuterons is discussed. 相似文献
58.
One of the major challenges in population biology is the identification of barriers to gene flow and/or secondary contacts
between differentiated entities. The level of genetic differentiation among eight populations of the common voleMicrotus arvalis (Pallas, 1779) around the Biebrza Wetlands, NE Poland was examined by analyzing seven microsatellite loci for 140 voles and
testing for the presence of barriers to gene flow. Overall population differentiation was moderate and significant (F
ST = 0.081,p < 0.001) and there was no correlation between geographical and genetic distances among populations. We found a relatively
high level of genetic variability within the populations studied. This could be explained by male bias in dispersal, a phenomenon
recently found inM. arvalis. Patterns of genetic structure visualized in synthetic genetic maps showed clear gradients along a southeast-northwest axis
across the study area, as well as the presence of a potential barrier to dispersal. The position of a barrier to gene flow
identified using Monmonier’s maximum difference algorithm likely corresponds to humid habitats of the Biebrza Wetlands. These
results suggest that the presence of environmental barriers to gene flow and drift may be responsible for the observed spatial
genetic structure ofM. arvalis in the Biebrza Valley. Institute of Biology, University of Białystok, OEwierkowa 20 B, 15-950 Białystok, Poland, 相似文献
59.
Effect of nickel on antioxidative enzyme activities, proline and chlorophyll contents in wheat shoots 总被引:12,自引:0,他引:12
Effect of two Ni concentrations (10 and 200 μM) on growth, Ni accumulation, chlorophyll and proline contents, relative water
content (RWC) as well as the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and glutathione S-transferase
(GST) were studied in shoots of wheat plants. Treatments caused a considerable accumulation of Ni in the shoots. However,
exposure of plants to 10 μM Ni did not lead to significant alterations in shoot growth except for a slight increase in fresh
mass. The other parameters studied were not affected by treatment of plants with 10 μM Ni. In contrast, 200 μM Ni caused inhibition
of shoot growth, a decline in RWC and chlorophyll content, accumulation of proline and occurrence of visible symptoms of Ni
toxicity. The activities of SOD and CAT decreased in response to 200 μM Ni. Conversely, several-fold enhancements of POD and
GST activities were observed following the 3rd day of 200 μM Ni treatment. 相似文献
60.
The paper contains the results of natural film experiments carried out on inland and coastal waters in the Dead Vistula catchment
area and mouth during 2000–2002, using the integrated Langmuir trough–Wilhelmy plate system. The static film parameters result
from the generalized scaling procedures applied to the surface pressure–area isotherms. They appear to reflect in a quantitative
and sensitive way the film composition (Alim, Mw, Eisoth), film solubility and the miscibility of its components (via R, ΔSc and y factors), and surface concentration (πeq, Γeq). The adsorption kinetics parameters: effective diffusion coefficient Deff/D and activation energy barrier Ea/RT are derived from dynamic surface pressure. There is a reason to suggest that certain classes of film-forming components or
‘end-members’ may dominate the static and dynamic surface properties. Variation in the surface rheological parameters of source-specific
biosurfactants is postulated to reflect organic matter dynamics in natural waters and were measured for the Dead Vistula river,
its tributaries and the adjacent coastal area. 相似文献