6,482 research outputs found
NEAR-SURFACE EFFECTS IN MODELLING OSCILLATIONS OF ETA BOO
Following the report of solar-like oscillations in the G0 V star eta Boo
(Kjeldsen et al. 1995, AJ 109, 1313), a first attempt to model the observed
frequencies was made by Christensen-Dalsgaard et al. (1995, ApJ Letters, in
press). This attempt succeeded in reproducing the observed frequency
separations, although there remained a difference of about 10 microHz between
observed and computed frequencies. In those models, the near-surface region of
the star was treated rather crudely. Here we consider more sophisticated models
that include non-local mixing-length theory, turbulent pressure and
nonadiabatic oscillations.Comment: uuencoded and compressed Postscript (2 pages, including figure); To
appear in Proceedings of IAU Colloquium 155, "Astrophysical Applications of
Stellar Pulsation", Cape Town, South Afric
Resource Competition on Integral Polymatroids
We study competitive resource allocation problems in which players distribute
their demands integrally on a set of resources subject to player-specific
submodular capacity constraints. Each player has to pay for each unit of demand
a cost that is a nondecreasing and convex function of the total allocation of
that resource. This general model of resource allocation generalizes both
singleton congestion games with integer-splittable demands and matroid
congestion games with player-specific costs. As our main result, we show that
in such general resource allocation problems a pure Nash equilibrium is
guaranteed to exist by giving a pseudo-polynomial algorithm computing a pure
Nash equilibrium.Comment: 17 page
Immorality and Irrationality
Does immorality necessarily involve irrationality? The question is often taken to be among the deepest in moral philosophy. But apparently deep questions sometimes admit of deflationary answers. In this case we can make way for a deflationary answer by appealing to dualism about rationality, according to which there are two fundamentally distinct notions of rationality: structural rationality and substantive rationality. I have defended dualism elsewhere. Here, I’ll argue that it allows us to embrace a sensible – I will not say boring – moderate view about the relationship between immorality and irrationality: roughly, that immorality involves substantive irrationality, but not structural irrationality. I defend this moderate view, and argue that many of the arguments for less moderate views turn either on missing the distinction between substantive and structural rationality, or on misconstruing it
Redefining disease emergence to improve prioritization and macro-ecological analyses
AbstractMicrobial infections are as old as the hosts they sicken, but interest in the emergence of pathogens and the diseases they cause has been accelerating rapidly. The term ‘emerging infectious disease’ was coined in the mid-1900s to describe changes in disease dynamics in the modern era. Both the term and the phenomena it is meant to characterize have evolved and diversified over time, leading to inconsistencies and confusion. Here, we review the evolution of the term ‘emerging infectious disease’ (EID) in the literature as applied to human hosts. We examine the pathways (e.g., speciation or strain differentiation in the causative agent vs. rapid geographic expansion of an existing pathogen) by which diseases emerge. We propose a new framework for disease and pathogen emergence to improve prioritization. And we illustrate how the operational definition of an EID affects conclusions concerning the pathways by which diseases emerge and the ecological and socioeconomic drivers that elicit emergence. As EIDs appear to be increasing globally, and resources for science level off or decline, the research community is pushed to prioritize its focus on the most threatening diseases, riskiest potential pathogens, and the places they occur. The working definition of emerging infectious diseases and pathogens plays a crucial role in prioritization, but we argue that the current definitions may be impeding these efforts. We propose a new framework for classifying pathogens and diseases as “emerging” that distinguishes EIDs from emerging pathogens and novel potential pathogens. We suggest prioritization of: 1) EIDs for adaptation and mitigation, 2) emerging pathogens for preventive measures, and 3) novel potential pathogens for intensive surveillance
Cognitive Information Processing
Contains reports on three research projects.National Science Foundation (Grant GP-2495)National Institutes of Health (Grant MH-04737-05)National Aeronautics and Space Administration (Grant NsG-496)Joint Services Electronics Program by the U. S. Army Research Office, Durha
Detection of a vibration-rotation emission line of hydrogen deuteride toward Orion Peak 1: excitation coupling of HD to H_2
The 2.46um v=1-0 R(5) line of deuterated molecular hydrogen, HD, has been
detected in the Orion Peak~1 shock emission region, at a surface brightness of
(8.5 +/- 2.1) x 10^(-9) W m^(-2)sr^(-1) over a 6 arcsec^2 area. Comparison of
the column density of HD(v=1,J=6) with the column density of HD(v=0,J=6)
previously observed from ISO and the H_2 level column densities toward the same
region implies that the excitation of HD is similar to that of H_2 for these
energy levels, despite much higher spontaneous transition rates for HD. We
suggest that this rough equality is caused by the coupling of the HD levels to
those of H_2, due to strong reactive collisions, HD + H -> H_2 + D, in warm,
partially dissociated gas. The deuterium abundance implied by the combined ISO
and UKIRT measurements toward Orion Peak 1 is [D]/[H] = (5.1 +/- 1.9)x10^(-6).Comment: 15 pages, 2 figures, accepted for publication in Ap
Uso de los tra amientos termico e no termico (alta presion hidrostatica) para la inactivación de enzimas bacterianas metaloproteases presentes en la degradación de leche.
El estudio de la aplicación de la tecnología de alta presión en el tratamiento de la leche para la inactivación de las enzimas proteolíticas puede proporcionar un producto con alta calidad y salubridad diferencial, capaz de investir en un aumento del consumo y de valor agregado, con el fin de beneficiarse de la cadena de producción, con impactos económicos y sociales
Analysis of the structure and chemical properties of some commercial carbon nanostructures
For many years the scientific community has believed in a promising future for carbon nanotubes for various applications in such diverse fields as polymer reinforcement, adsorption, catalysis, electronics and medicine. Industrial production of carbon nanotubes and -fibers and the subsequent availability and decrease of price, have rendered this vision feasible. In the last years, several carbon nanomaterial products have been marketed by major chemical companies. In this work, we present an extensive characterization of a representative set of commercially available carbon nanomaterials. Special focus has been put on their quality, i.e. presence of metal or carbonaceous impurities but also homogeneity and structural integrity. The observations are of importance for subsequent use in catalysis where the presence of impurities or defects in the nanostructure can dramatically modify the activity of the catalytic material
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