1,091 research outputs found
Evidence for a Significant Decline in Queen Conch in the Bahamas, Including the Population in a Marine Protected Area
Metamorphosis of Queen Conch larvae is triggered by trophic cues found in the nursery habitats
Perspectives on Michael A. Bernstein\u27s \u3cem\u3eA Perilous Progress: Economists and Public Purpose in Twentieth-Century America\u3c/em\u3e
Models for Galactic cosmic-ray propagation
A new numerical model of particle propagation in the Galaxy has been
developed, which allows the study of cosmic-ray and gamma-ray production and
propagation in 2D or 3D, including a full reaction network. This is a further
development of the code which has been used for studies of cosmic ray
reacceleration, Galactic halo size, antiprotons and positrons in cosmic rays,
the interpretation of diffuse continuum gamma rays, and dark matter. In this
paper we illustrate recent results focussing on B/C, sub-Fe/Fe, ACE radioactive
isotope data, source abundances and antiprotons. From the radioactive nuclei we
derive a range of 3-7 kpc for the height of the cosmic-ray halo.Comment: Invited talk at the 33rd COSPAR Scientific Assembly (Warsaw 2000); 10
pages including 10 ps-figures and 2 tables, latex2e, uses cospar.sty. To
appear in Advances in Space Research 2001. More details can be found at
http://www.gamma.mpe-garching.mpg.de/~aws/aws.htm
Social and cultural origins of motivations to volunteer a comparison of university students in six countries
Although participation in volunteering and motivations to volunteer (MTV) have received substantial attention on the national level, particularly in the US, few studies have compared and explained these issues across cultural and political contexts. This study compares how two theoretical perspectives, social origins theory and signalling theory, explain variations in MTV across different countries. The study analyses responses from a sample of 5794 students from six countries representing distinct institutional contexts. The findings provide strong support for signalling theory but less so for social origins theory. The article concludes that volunteering is a personal decision and thus is influenced more at the individual level but is also impacted to some degree by macro-level societal forces
Gamma-ray and radio tests of the e+e- excess from DM annihilations
PAMELA and ATIC recently reported an excess in e+e- cosmic rays. We show that
if it is due to Dark Matter annihilations, the associated gamma-ray flux and
the synchrotron emission produced by e+e- in the galactic magnetic field
violate HESS and radio observations of the galactic center and HESS
observations of dwarf Spheroidals, unless the DM density profile is
significantly less steep than the benchmark NFW and Einasto profiles.Comment: 16 pages, 4 figures; v2: normalizations fixed in Table 2 and typos
corrected (no changes in the analysis nor the results), some references and
comments added; v3: minor additions, matches published versio
Propagation of secondary antiprotons and cosmic rays in the Galaxy
Recent measurements of the cosmic ray (CR) antiproton flux have been shown to
challenge existing CR propagation models. It was shown that the reacceleration
models designed to match secondary to primary nuclei ratios (e.g., B/C) produce
too few antiprotons. In the present paper we discuss one possibility to
overcome these difficulties. Using the measured antiproton flux AND B/C ratio
to fix the diffusion coefficient, we show that the spectra of primary nuclei as
measured in the heliosphere may contain a fresh local "unprocessed" component
at low energies perhaps associated with the Local Bubble, thus decreasing the
measured secondary to primary nuclei ratio. The independent evidence for SN
activity in the solar vicinity in the last few Myr supports this idea. The
model reproduces antiprotons, B/C ratio, and elemental abundances up to Ni
(Z<=28). Calculated isotopic distributions of Be and B are in perfect agreement
with CR data. The abundances of three "radioactive clock" isotopes in CR, 10Be,
26Al, 36Cl, are all consistent and indicate a halo size z_h~4 kpc based on the
most accurate data taken by the ACE spacecraft.Comment: 6 pages, 5 ps-figures, cospar.sty; Proc. of 34th COSPAR Scientific
Assembly (Houston, 10-19 October 2002). Submitted to Advances in Space
Research. More details can be found at
http://www.gamma.mpe-garching.mpg.de/~aws/aws.htm
The Effects of Media and their Logic on Legitimacy Sources within Local Governance Networks: A Three-Case Comparative Study
__Abstract__
Although theoretical and empirical work on the democratic legitimacy of
governance networks is growing, little attention has been paid to the impact of mediatisation
on democracies. Media have their own logic of news-making led by the media’s rules,
aims, production routines and constraints, which affect political decision-making processes.
In this article, we specifically study how media and their logic affect three
democratic legitimacy sources of political decision-making within governance networks:
voice, due deliberation and accountability. We conducted a comparative case study of
three local governance networks using a mixed method design, combining extensive
qualitative case studies, interviews and a quantitative content analysis of media reports.
In all three cases, media logic increased voice possibilities for citizen groups.
Furthermore, it broadened the deliberation process, although this did not improve the
quality of this process per se, because the media focus on drama and negativity. Finally,
media logic often pushed political authorities into a reactive communication style as they
had to fight against negative images in the media. Proactive communication about
projects, such as public relation (PR) strategies and branding, is difficult in such a
media landscape
AltitudeOmics: The Integrative Physiology of Human Acclimatization to Hypobaric Hypoxia and Its Retention upon Reascent.
An understanding of human responses to hypoxia is important for the health of millions of people worldwide who visit, live, or work in the hypoxic environment encountered at high altitudes. In spite of dozens of studies over the last 100 years, the basic mechanisms controlling acclimatization to hypoxia remain largely unknown. The AltitudeOmics project aimed to bridge this gap. Our goals were 1) to describe a phenotype for successful acclimatization and assess its retention and 2) use these findings as a foundation for companion mechanistic studies. Our approach was to characterize acclimatization by measuring changes in arterial oxygenation and hemoglobin concentration [Hb], acute mountain sickness (AMS), cognitive function, and exercise performance in 21 subjects as they acclimatized to 5260 m over 16 days. We then focused on the retention of acclimatization by having subjects reascend to 5260 m after either 7 (n = 14) or 21 (n = 7) days at 1525 m. At 16 days at 5260 m we observed: 1) increases in arterial oxygenation and [Hb] (compared to acute hypoxia: PaO2 rose 9±4 mmHg to 45±4 while PaCO2 dropped a further 6±3 mmHg to 21±3, and [Hb] rose 1.8±0.7 g/dL to 16±2 g/dL; 2) no AMS; 3) improved cognitive function; and 4) improved exercise performance by 8±8% (all changes p<0.01). Upon reascent, we observed retention of arterial oxygenation but not [Hb], protection from AMS, retention of exercise performance, less retention of cognitive function; and noted that some of these effects lasted for 21 days. Taken together, these findings reveal new information about retention of acclimatization, and can be used as a physiological foundation to explore the molecular mechanisms of acclimatization and its retention
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