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

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

Parameterizing cloud condensation nuclei concentrations during HOPE

An aerosol model was used to simulate the generation and transport of aerosols over Germany during the HD(CP)2 Observational Prototype Experiment (HOPE) field campaign of 2013. The aerosol number concentrations and size distributions were evaluated against observations, which shows satisfactory agreement in the magnitude and temporal variability of the main aerosol contributors to cloud condensation nuclei (CCN) concentrations. From the modelled aerosol number concentrations, number concentrations of CCN were calculated as a function of vertical velocity using a comprehensive aerosol activation scheme which takes into account the influence of aerosol chemical and physical properties on CCN formation. There is a large amount of spatial variability in aerosol concentrations; however the resulting CCN concentrations vary significantly less over the domain. Temporal variability is large in both aerosols and CCN. A parameterization of the CCN number concentrations is developed for use in models. The technique involves defining a number of best fit functions to capture the dependence of CCN on vertical velocity at different pressure levels. In this way, aerosol chemical and physical properties as well as thermodynamic conditions are taken into account in the new CCN parameterization. A comparison between the parameterization and the CCN estimates from the model data shows excellent agreement. This parameterization may be used in other regions and time periods with a similar aerosol load; furthermore, the technique demonstrated here may be employed in regions dominated by different aerosol species

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

A novel mechanism of non- feminizing estrogens in neuroprotection

Estrogens are potent and efficacious neuroprotectants both in vitro and in vivo in a variety of models of neurotoxicity. We determined the structural requirements for neuroprotection in an in vitro assay using a panel of more than 70 novel estratrienes, synthesized to reduce or eliminate estrogen receptor (ER) binding. We observed that neuroprotection could be enhanced by as much as 200-fold through modifications that positioned a large bulky group at the C2 or C4 position of the phenolic A ring of the estratriene. Further, substitutions on the B, C or D rings either reduced or did not markedly change neuroprotection. Collectively, there was a negative correlation between binding to ERs and neuroprotection with the more potent compounds showing no ER binding. In an in vivo model for neuroprotection, transient cerebral ischemia, efficacious compounds were active in protection of brain tissue from this pro-oxidant insult. We demonstrated that these non-feminizing estrogens engage in a redox cycle with glutathione, using the hexose monophosphate shunt to apply cytosolic reducing potential to cellular membranes. Together, these results demonstrate that non-feminizing estrogens are neuroprotective and protect brain from the induction of ischemic- and Alzheimer’s disease (AD)-like neuropathology in an animal model. These features of non-feminizing estrogens make them attractive compounds for assessment of efficacy in AD and stroke, as they are not expected to show the side effects of chronic estrogen therapy that are mediated by ER actions in the liver, uterus and breast

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)

Absolute lymphocyte and neutrophil counts in neonatal ischemic brain injury

Objectives: This study aimed to identify differences in absolute neutrophils, lymphocytes, and neutrophil-to-lymphocyte ratio between neonates with two forms of ischemic brain injury, hypoxic-ischemic encephalopathy, and acute ischemic stroke, compared to controls. We also aimed to determine whether this neutrophil/lymphocyte response pattern is associated with disease severity or is a consequence of the effects of total-body cooling, an approved treatment for moderate-to-severe hypoxic-ischemic encephalopathy. Methods: A retrospective chart review of 101 neonates with hypoxic-ischemic encephalopathy + total-body cooling (n = 26), hypoxic-ischemic encephalopathy (n=12), acute ischemic stroke (n=15), and transient tachypnea of the newborn (n=48) was conducted; transient tachypnea of the newborn neonates were used as the control group. Absolute neutrophil count and absolute lymphocyte count at three time-intervals (0–12, 12–36, and 36–60 h after birth) were collected, and neutrophil- to-lymphocyte ratio was calculated. Results: Hypoxic-ischemic encephalopathy+total-body cooling neonates demonstrated significant time-interval-dependent changes in absolute lymphocyte count and neutrophil-to-lymphocyte ratio levels compared to transient tachypnea of the newborn and acute ischemic stroke patients. Pooled analysis of absolute lymphocyte count for neonates with acute ischemic stroke and hypoxic-ischemic encephalopathy (not hypoxic-ischemic encephalopathy+total-body cooling) revealed that absolute lymphocyte count changes occurring at 0–12 h are likely due to disease progression, rather than total-body cooling treatment. Conclusion: These data suggest that the neutrophil/lymphocyte response is modulated following neonatal ischemic brain injury, representing a possible target for therapeutic intervention. However, initial severity of hypoxic-ischemic encephalopathy among these patients could also account for the observed changes in the immune response to injury. Thus, additional work to clarify the contributions of cooling therapy and disease severity to neutrophil/lymphocyte response following hypoxic- ischemic encephalopathy in neonates is warranted