Quaternion algebras with the same subfields

G. Prasad and A. Rapinchuk asked if two quaternion division F -algebras that have the same subfields are necessarily isomorphic. The answer is known to be "no" for some very large fields. We prove that the answer is "yes" if F is an extension of a global field K so that F /K is unirational and has zero unramified Brauer group. We also prove a similar result for Pfister forms and give an application to tractable fields

Genetic and serological heterogeneity of the supertypic HLA-B locus specificities Bw4 and Bw6

Gene cloning and sequencing of the HLA-B locus split antigens B38 (B16.1) and B39 (B16.2) allowed localization of their subtypic as well as their public specificities HLA-Bw4 or -Bw6 to the c~-helical region of the c~ 1 domain flanked by the amino acid positions 74-83. Comparison of their amino acid sequences with those of other HLA-B-locus alleles established HLA-Bw6 to be distinguished by Ser at residue 77 and Asn at residue 80. In contrast, HLA-Bw4 is characterized by at least seven different patterns of amino acid exchanges at positions 77 and 80-83. Reactivity patterns of Bw4- or Bw6-specific monoclonal antibodies reveal two alloantigenic epitopes contributing to the HLA-Bw4 or -Bw6 specificity residing next to the region of highest diversity of the cr domain

Seasonal variability of Saharan desert dust and ice nucleating particles over Europe

Dust aerosols are thought to be the main contributor to atmospheric ice nucleation. While there are case studies supporting this, a climatological sense of the importance of dust to atmospheric ice nucleating particle (INP) concentrations, and it\u27s seasonal variability over Europe is lacking. Here, we use a mesoscale model to estimate Saharan dust concentrations over Europe in winter and summer of 2007–2008. There are large differences in median dust concentrations between seasons, with the highest concentrations and highest variability in the lowest 4 km. Laboratory based ice nucleation parameterisations are applied to these dust number concentrations to calculate the potential INP resulting from immersion freezing and deposition nucleation on these dust particles. The potential INP concentrations generally increase with height due to decreasing temperatures in the lower and mid-troposphere and exhibit a maximum in the upper troposphere where INP concentrations decrease again with altitude due to decreasing dust concentrations. The potential INP profiles exhibit similarly large differences between seasons, with the highest concentrations in winter (median potential immersion INP concentrations up to 103 m−3, median potential deposition INP concentrations at 120% relative humidity with respect to ice up to 105 m−3) occurring closer to the ground for both nucleation modes. Using these results, a best-fit function is provided to estimate the potential INPs for use in limited-area models, which is representative of the normal background INP concentrations over Europe. A statistical evaluation of the results against field and laboratory measurements indicates that the INP concentrations are in close agreement with observations

Seasonal variability of Saharan desert dust and ice nucleating particles over Europe

Dust aerosols are thought to be the main contributor to atmospheric ice nucleation. While there are case studies supporting this, a climatological sense of the importance of dust to atmospheric ice nucleating particle (INP) concentrations and its seasonal variability over Europe is lacking. Here, we use a mesoscale model to estimate Saharan dust concentrations over Europe in 2008. There are large differences in median dust concentrations between seasons, with the highest concentrations and highest variability in the lower to mid-troposphere. Laboratory-based ice nucleation parameterisations are applied to these simulated dust number concentrations to calculate the potential INP resulting from immersion freezing and deposition nucleation on these dust particles. The potential INP concentrations increase exponentially with height due to decreasing temperatures in the lower and mid-troposphere. When the ice-activated fraction increases sufficiently, INP concentrations follow the dust particle concentrations. The potential INP profiles exhibit similarly large differences between seasons, with the highest concentrations in spring (median potential immersion INP concentrations nearly 105 m-3, median potential deposition INP concentrations at 120% relative humidity with respect to ice over 105 m-3), about an order of magnitude larger than those in summer. Using these results, a best-fit function is provided to estimate the potential INPs for use in limited-area models, which is representative of the normal background INP concentrations over Europe. A statistical evaluation of the results against field and laboratory measurements indicates that the INP concentrations are in close agreement with observations

Adoption of cleaner production practices by dairy farmers in southern Chile

Nahuelhual, L (reprint author), Univ Austral Chile, Inst Econ Agr, Casilla 567, Valdivia, ChileRising concerns about the environmental costs of dairy production have resulted in an increasing use of farm practices that diminish negative production externalities. Yet, little empirical evidence exists regarding the factors influencing the adoption of pollution-reducing strategies by dairy farmers. In this study, we estimate a logit probability model to explain first-stage adoption of capital-intensive cleaner production (CP) practices, using a sample of 100 medium and large-size dairy farms located in southern Chile. Voluntary approaches to pollution control in agriculture are relatively recent in Chile and diffusion has been slow and uneven among farmers. Only 43% of the farmers surveyed were using some CP practices at the time of the interview. The probability of adoption was found to be positively correlated with farmer's education and age, awareness of environmental regulations, the type of milk buyer, and the use of complementary CP management practices. Conversely, farm structure variables were not significant, which suggests that the adoption of CP practices could be responding to non-economic motivations

Small-scale structures in neutrals and charged aerosol particles as observed during the ECOMA/MASS rocket campaign

We present results of in situ measurements of neutral temperature during the ECOMA/MASS rocket campaign. We present and compare results of turbulence measurements conducted simultaneously by both in situ and doppler radar techniques. We show that the derived values of the turbulence energy dissipation rates are similar on average. We also find a region with a near adiabatic lapse rate with turbulence detected at the upper and lower edge. We note that it is consistent with expectation for a Kelvin-Helmholtz instability. We also present an estimate of the Schmidt numbers, Sc, for the charged aerosols that utilizes in situ measured small-scale density fluctuations of charged aerosols and both in situ and radar turbulence measurements. The derived Schmidt numbers fall within the range between 100 and 4500. This result agrees with previous estimates based on multi-frequency observations of PMSE (Rapp et al., 2008) and also with estimates of microphysical parameters presented in the companion paper by Rapp et al. (2009)

Testing the proposed link between cosmic rays and cloud cover

A decrease in the globally averaged low level cloud cover, deduced from the ISCCP infra red data, as the cosmic ray intensity decreased during the solar cycle 22 was observed by two groups. The groups went on to hypothesise that the decrease in ionization due to cosmic rays causes the decrease in cloud cover, thereby explaining a large part of the presently observed global warming. We have examined this hypothesis to look for evidence to corroborate it. None has been found and so our conclusions are to doubt it. From the absence of corroborative evidence, we estimate that less than 23%, at the 95% confidence level, of the 11-year cycle change in the globally averaged cloud cover observed in solar cycle 22 is due to the change in the rate of ionization from the solar modulation of cosmic rays

Forbush decreases and solar events seen in the 10 - 20GeV energy range by the Karlsruhe Muon Telescope

Since 1993, a muon telescope located at Forschungszentrum Karlsruhe (Karlsruhe Muon Telescope) has been recording the flux of single muons mostly originating from primary cosmic-ray protons with dominant energies in the 10 - 20 GeV range. The data are used to investigate the influence of solar effects on the flux of cosmic-rays measured at Earth. Non-periodic events like Forbush decreases and ground level enhancements are detected in the registered muon flux. A selection of recent events will be presented and compared to data from the Jungfraujoch neutron monitor. The data of the Karlsruhe Muon Telescope help to extend the knowledge about Forbush decreases and ground level enhancements to energies beyond the neutron monitor regime.Comment: 9 pages, 7 figures, in Press AS

A variational approach to strongly damped wave equations

We discuss a Hilbert space method that allows to prove analytical well-posedness of a class of linear strongly damped wave equations. The main technical tool is a perturbation lemma for sesquilinear forms, which seems to be new. In most common linear cases we can furthermore apply a recent result due to Crouzeix--Haase, thus extending several known results and obtaining optimal analyticity angle.Comment: This is an extended version of an article appeared in \emph{Functional Analysis and Evolution Equations -- The G\"unter Lumer Volume}, edited by H. Amann et al., Birkh\"auser, Basel, 2008. In the latest submission to arXiv only some typos have been fixe