9,428 research outputs found
Thomson scattering in a low-pressure neon mercury positive column
The electron density and the electron temperature in a low-pressure neon mercury positive column are determined using Thomson scattering. Special attention has been given to the stray light reduction in the Thomson scattering setup. The results are obtained in a discharge tube with a 26 mm diam, 10 mbar of neon, a mercury pressure inbetween 0.14 and 0.85 Pa, and an electric current ranging from 100 to 400 mA. The systematic error in the electron density is 15%–45%, the statistical error is 25%–35%. The total error in the electron temperature is 15%–35%. ©2001 American Institute of Physics
Two subsets of human alphoid repetitive DNA show distinct preferential localization in the pericentromeric heterochromatin of chromosomes 13, 21 and 18
Gezondheidsmanagement vanuit een systeeminnovatie perspectief. Eindrapportage van het onderzoekstraject "System Innovation for Workplace Health Promotion"
The invasive occurrence of the Mediterranean dwarfspider <i>Diplocephalus graecus</i> (O.-P. Cambridge, 1872) in Belgium (Araneae: Linyphiidae)
Nambu monopoles in lattice Electroweak theory
We considered the lattice electroweak theory at realistic values of
and and for large values of the Higgs mass. We investigated
numerically the properties of topological objects that are identified with
quantum Nambu monopoles. We have found that the action density near the Nambu
monopole worldlines exceeds the density averaged over the lattice in the
physical region of the phase diagram. Moreover, their percolation probability
is found to be an order parameter for the transition between the symmetric and
the broken phases. Therefore, these monopoles indeed appear as real physical
objects. However, we have found that their density on the lattice increases
with increasing ultraviolet cutoff. Thus we conclude, that the conventional
lattice electroweak theory is not able to predict the density of Nambu
monopoles. This means that the description of Nambu monopole physics based on
the lattice Weinberg - Salam model with finite ultraviolet cutoff is
incomplete. We expect that the correct description may be obtained only within
the lattice theory that involves the description of TeV - scale physics.Comment: LATE
Dispersal by cattle of salt-marsh and dune species into salt-marsh and dune communities
Seed dispersal via ingestion and defecation by large herbivores (endozoochory) plays a potentially important role in structuring plant communities. In the present study we tested whether cattle disperse seeds between different plant communities in a heterogeneous coastal habitat. We surveyed the seed contents of cattle dung collected from two habitat types within a grazing system, one in dunes and the other in salt-marsh. The dunes are characterized by sandy soil, and infrequent inundation by the sea, whereas the salt-marsh features clay deposited during inundations. Seeds of both salt-marsh and dune species were dispersed into salt-marsh and dune habitats. The seed content of cattle dung collected in salt-marsh and dunes was similar with respect to species composition and seed density. However, dispersal of dune species into salt-marsh and vice-versa did not result in establishment in those communities. Seed traits per se did not differ between dune species and salt-marsh species. Species abundance in the established vegetation and seed density in dung were positively correlated. Seed abundance for most species found in dung was consistent with the availability of viable seeds during the growing season. Seed mass, seed 'roundness' and seed release height were all negatively correlated with seed numbers in dung. An indirect factor, namely, forage quality of the plant, and hence attractiveness for herbivores, could explain the higher likelihood of seed dispersal of salt-marsh species than of dune species. The salt-marsh harbours species with higher forage quality than the dune species, as derived from Ellenberg nitrogen indicator values
Interplay of Peltier and Seebeck effects in nanoscale nonlocal spin valves
We have experimentally studied the role of thermoelectric effects in
nanoscale nonlocal spin valve devices. A finite element thermoelectric model is
developed to calculate the generated Seebeck voltages due to Peltier and Joule
heating in the devices. By measuring the first, second and third harmonic
voltage response non locally, the model is experimentally examined. The results
indicate that the combination of Peltier and Seebeck effects contributes
significantly to the nonlocal baseline resistance. Moreover, we found that the
second and third harmonic response signals can be attributed to Joule heating
and temperature dependencies of both Seebeck coefficient and resistivity.Comment: 4 pages, 4 figure
Dominant negative phenotype of Bacillus thuringiensis Cry1Ab, Cry11Aa and Cry4Ba mutants suggest hetero-oligomer formation among different Cry toxins.
Background - Bacillus thuringiensis Cry toxins are used worldwide in the control of different insect pests important in agriculture or in human health. The Cry proteins are pore-forming toxins that affect the midgut cell of target insects. It was shown that non-toxic Cry1Ab helix a-4 mutants had a dominant negative (DN) phenotype inhibiting the toxicity of wildtype Cry1Ab when used in equimolar or sub-stoichiometric ratios (1:1, 0.5:1, mutant:wt) indicating that oligomer formation is a key step in toxicity of Cry toxins. Methodology/Principal Findings - The DN Cry1Ab-D136N/T143D mutant that is able to block toxicity of Cry1Ab toxin, was used to analyze its capacity to block the activity against Manduca sexta larvae of other Cry1 toxins, such as Cry1Aa, Cry1Ac, Cry1Ca, Cry1Da, Cry1Ea and Cry1Fa. Cry1Ab-DN mutant inhibited toxicity of Cry1Aa, Cry1Ac and Cry1Fa. In addition, we isolated mutants in helix a-4 of Cry4Ba and Cry11Aa, and demonstrate that Cry4Ba-E159K and Cry11Aa-V142D are inactive and completely block the toxicity against Aedes aegypti of both wildtype toxins, when used at sub-stoichiometric ratios, confirming a DN phenotype. As controls we analyzed Cry1Ab-R99A or Cry11Aa-E97A mutants that are located in helix a-3 and are affected in toxin oligomerization. These mutants do not show a DN phenotype but were able to block toxicity when used in 10:1 or 100:1 ratios (mutant:wt) probably by competition of binding with toxin receptors. Conclusions/Significance - We show that DN phenotype can be observed among different Cry toxins suggesting that may interact in vivo forming hetero-oligomers. The DN phenotype cannot be observed in mutants affected in oligomerization, suggesting that this step is important to inhibit toxicity of other toxin
Sodium status and kidney involvement during COVID-19 infection
The angiotensin-converting enzyme 2 receptor (ACE2) is expressed in epithelial cells of many tissues including the kidney, and has been identified to interact with human pathogenic coronaviruses, including SARS-CoV-2. Although diffuse alveolar damage and acute respiratory failure are the main features of COVID-19 infection, two recent studies demonstrate that kidney impairment in hospitalized COVID-19 patients is common, and that kidney involvement is associated with high risk of in-hospital death. Interestingly, studies in rats have demonstrated that high dietary sodium intake results in down-regulation of the ACE2 expression in kidney tissue. We hypothesize that low sodium status makes kidney involvement during the course of COVID-19 infection more likely due to upregulation of membrane bound ACE2 in the kidneys. We propose that sodium intake and status should be monitored carefully during severe COVID-19 infections, and that low sodium intake be corrected early in its course, despite a potential conflict regarding common dietary recommendations to restrict dietary sodium intake in patients with hypertension, diabetes, and kidney disease.</p
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