On the determination of anti-neutrino spectra from nuclear reactors

In this paper we study the effect of, well-known, higher order corrections to the allowed beta decay spectrum on the determination of anti-neutrino spectra resulting from the decays of fission fragments. In particular, we try to estimate the associated theory errors and find that induced currents like weak magnetism may ultimately limit our ability to improve the current accuracy and under certain circumstance could even largely increase the theoretical errors. We also perform a critical evaluation of the errors associated with our method to extract the anti-neutrino spectrum using synthetic beta spectra. It turns out, that a fit using only virtual beta branches with a judicious choice of the effective nuclear charge provides results with a minimal bias. We apply this method to actual data for U235, Pu239 and Pu241 and confirm, within errors, recent results, which indicate a net 3% upward shift in energy averaged anti-neutrino fluxes. However, we also find significant shape differences which can in principle be tested by high statistics anti-neutrino data samples.Comment: 20 pages, 5 figures, 9 tables, added references, version accepted for publication in Phys. Rev. C. Corrected errors in tab. 1 and eqs. 18 and 19. Results and conclusion unchange

A new analysis of 14O beta decay: branching ratios and CVC consistency

The ground-state Gamow-Teller transition in the decay of 14O is strongly hindered and the electron spectrum deviates markedly from the allowed shape. A reanalysis of the only available data on this spectrum changes the branching ratio assigned to this transition by seven standard deviations: our new result is (0.54 \pm 0.02)%. The Kurie plot data from two earlier publications are also examined and a revision to their published branching ratios is recommended. The required nuclear matrix elements are calculated with the shell model and, for the first time, consistency is obtained between the M1 matrix element deduced from the analog gamma transition in 14N and that deduced from the slope of the shape-correction function in the beta transition, a requirement of the conserved vector current hypothesis. This consistency is only obtained, however, if renormalized rather than free-nucleon operators are used in the shell-model calculations. In the mirror decay of 14C a similar situation occurs. Consistency between the 14C lifetime, the slope of the shape-correction function and the M1 matrix element from gamma decay can only be achieved with renormalized operators in the shell-model calculation.Comment: 9 pages; revtex4; one figur

The Charge of Glass and Silica Surfaces

We present a method of calculating the electric charge density of glass and silica surfaces in contact with aqueous electrolytes for two cases of practical relevance that are not amenable to standard techniques: surfaces of low specific area at low ionic strength and surfaces interacting strongly with a second anionic surface.Comment: 7 pages, including 3 figure

Commodity tax competition and industry location under the destination - and the origin - principle

We develop a model of commodity tax competition with monopolistically competitive internationally mobile firms, transport costs, and asymmetric country sizes. We investigate the impacts of non-cooperative tax setting, as well as of tax harmonization and changes in the tax principle, in both the short and the long run. The origin principle, when compared to the destination principle, is shown to exacerbate tax competition and to erode tax revenues, yet leads to a more equal spatial distribution of economic activity. This suggests that federations which care about spatial inequality, like the European Union, face a non-trivial- choice for their tax principle that goes beyond the standard considerations of tax revenue redistribution.commodity tax competitions; origin principle; destination principle; tax harmonization; industry location

Signatures of criticality arise in simple neural population models with correlations

Large-scale recordings of neuronal activity make it possible to gain insights into the collective activity of neural ensembles. It has been hypothesized that neural populations might be optimized to operate at a 'thermodynamic critical point', and that this property has implications for information processing. Support for this notion has come from a series of studies which identified statistical signatures of criticality in the ensemble activity of retinal ganglion cells. What are the underlying mechanisms that give rise to these observations? Here we show that signatures of criticality arise even in simple feed-forward models of retinal population activity. In particular, they occur whenever neural population data exhibits correlations, and is randomly sub-sampled during data analysis. These results show that signatures of criticality are not necessarily indicative of an optimized coding strategy, and challenge the utility of analysis approaches based on equilibrium thermodynamics for understanding partially observed biological systems.Comment: 36 pages, LaTeX; added journal reference on page 1, added link to code repositor

Formulation opportunities due to gelling and jamming in colloidal multiphase systems

Colloidal particles can mediate a kinetic arrest of the thermodynamically favored phase separation between immiscible fluids, and the resulting arrested multiphase structures can play a central role in addressing formulation challenges. The kinetic arrest often proceeds via jamming of particles adsorbed at a fluid interface, and sometimes via the formation of a gel network, with different implications for the system’s mechanics and transport properties. Gelling and jamming appear to occur in parallel when an aqueous solution and a small amount of oil are combined and frothed in the presence of particles with somewhat similar wettability for both liquids. The resulting structure is that of the recently discovered “capillary foams”: water-continuous four-phase systems, in which gas bubbles are coated by a particle-stabilized layer of oil and embedded in a network of oil-bridged particles. I will discuss material properties and formulation opportunities afforded by the complex multi-phase architecture of these new foams

Beach impact study, Padre Island National Seashore

Prepared for Office of Natural Science, Southwest Region, National Park Service, under contract CX70005044830 April 1976Vegetative differences between heavily and very lightly trafficked beaches show that more beach traffic correlates with quantitative decreases in variety and density of plants and with declines of grasses relative to forbs. The vegetated portions of all beaches continue to grow in volume. However, this is at the expense of the more seaward (more trafficked) parts of the beaches and has lead to overall loss of total beach volume except where vehicular traffic is prohibited. The very lightly trafficked beach is the only study site wherein the entire beach to mean sea level has grown. The effect of these trends on resistance to storm surge erosion remains to be tested.Marine Scienc

NK cells as effectors of acquired immune responses: effector CD4+ T cell-dependent activation of NK cells following vaccination.

We characterized vaccine-induced cellular responses to rabies virus in naive adult volunteers. Contrary to current paradigms, we observed potent and prolonged in vitro NK cell cytokine production and degranulation responses after restimulation of PBMCs with inactivated rabies virus in vaccinated, but not in unvaccinated, individuals. This "recall" NK cell response was absolutely dependent on Ag-specific IL-2 from CD45RO(+) CD4(+) T cells as well as IL-12 and IL-18 from accessory cells. Importantly, NK cells represented over 70% of all IFN-gamma-secreting and degranulating cells in the first 12-18 h after virus rechallenge indicating they may be required for rapid control of infection after vaccination. Activation of NK cells may be a critical function of IL-2-secreting effector memory T cells. Although IL-2-dependent postvaccination NK cell activation has been reported previously, this is the first time the magnitude of this effect and its contribution to the overall vaccine-induced response has been appreciated and the mechanisms of NK activation postvaccination have been elucidated. Our data will allow standard protocols for evaluating vaccine-induced immunity to be adapted to assess NK cell effector responses

Commodity tax competition and industry location under the destination- and the origin-principle

We develop a model of commodity tax competition with monopolistically competitive internationally mobile firms, transport costs, and asymmetric country sizes. We investigate the impacts of non-cooperative tax setting, as well as of tax harmonization and changes in the tax principle, in both the short and the long run. The origin principle, when compared to the destination principle, is shown to exacerbate tax competition and to erode tax revenues, yet leads to a more equal spatial distribution of economic activity. This suggests that federations which care about spatial inequality, like the European Union, face a non-trivial choice for their tax principle that goes beyond the standard considerations of tax revenue redistribution.commodity tax competition, origin principle, destination principle, tax harmonization, industry location