1,803 research outputs found
HESFIRE: a global fire model to explore the role of anthropogenic and weather drivers
Vegetation fires are a major driver of ecosystem
dynamics and greenhouse gas emissions. Anticipating potential
changes in fire activity and their impacts relies first
on a realistic model of fire activity (e.g., fire incidence and
interannual variability) and second on a model accounting
for fire impacts (e.g., mortality and emissions). In this paper,
we focus on our understanding of fire activity and describe
a new fire model, HESFIRE (Human–Earth System
FIRE), which integrates the influence of weather, vegetation
characteristics, and human activities on fires in a stand-alone
framework. It was developed with a particular emphasis on
allowing fires to spread over consecutive days given their major
contribution to burned areas in many ecosystems. A subset
of the model parameters was calibrated through an optimization
procedure using observation data to enhance our
knowledge of regional drivers of fire activity and improve
the performance of the model on a global scale. Modeled fire
activity showed reasonable agreement with observations of
burned area, fire seasonality, and interannual variability in
many regions, including for spatial and temporal domains not
included in the optimization procedure. Significant discrepancies
are investigated, most notably regarding fires in boreal
regions and in xeric ecosystems and also fire size distribution.
The sensitivity of fire activity to model parameters is
analyzed to explore the dominance of specific drivers across
regions and ecosystems. The characteristics of HESFIRE and
the outcome of its evaluation provide insights into the influence of anthropogenic activities and weather, and their interactions,
on fire activityinfo:eu-repo/semantics/publishedVersio
Spitzer Mapping of PAHs and H2 in Photodissociation Regions
The mid-infrared (MIR) spectra of dense photodissociation regions (PDRs) are
typically dominated by emission from polycyclic aromatic hydrocarbons (PAHs)
and the lowest pure rotational states of molecular hydrogen (H2); two species
which are probes of the physical properties of gas and dust in intense UV
radiation fields. We utilize the high angular resolution of the Infrared
Spectrograph on the Spitzer Space Telescope to construct spectral maps of the
PAH and H2 features for three of the best studied PDRs in the galaxy, NGC 7023,
NGC 2023 and IC 63. We present spatially resolved maps of the physical
properties, including the H2 ortho-to-para ratio, temperature, and G_o/n_H. We
also present evidence for PAH dehydrogenation, which may support theories of H2
formation on PAH surfaces, and a detection of preferential self-shielding of
ortho-H2. All PDRs studied exhibit average temperatures of ~500 - 800K, warm H2
column densities of ~10^20 cm^-2, G_o/n_H ~ 0.1 - 0.8, and ortho-to-para ratios
of ~ 1.8. We find that while the average of each of these properties is
consistent with previous single value measurements of these PDRs, when
available, the addition of spatial resolution yields a diversity of values with
gas temperatures as high as 1500 K, column densities spanning ~ 2 orders of
magnitude, and extreme ortho-to-para ratios of 3.Comment: 14 figure
Global fire activity patterns (1996-2006) and climatic influence: an analysis using World Fire Atlas
Vegetation fires have been acknowledged as an environmental
process of global scale, which affects the chemical
composition of the troposphere, and has profound ecological
and climatic impacts. However, considerable uncertainty
remains, especially concerning intra and inter-annual
variability of fire incidence. The main goals of our globalscale
study were to characterise spatial-temporal patterns of
fire activity, to identify broad geographical areas with similar
vegetation fire dynamics, and to analyse the relationship
between fire activity and the El Ni˜no-Southern Oscillation.
This study relies on 10 years (mid 1996–mid
2006) of screened European Space Agency World Fire Atlas
(WFA) data, obtained from Along Track Scanning Radiometer
(ATSR) and Advanced ATSR (AATSR) imagery.
Empirical Orthogonal Function analysis was used to reduce
the dimensionality of the dataset. Regions of homogeneous
fire dynamics were identified with cluster analysis, and interpreted
based on their eco-climatic characteristics. The
impact of 1997–1998 El Ni˜no is clearly dominant over the
study period, causing increased fire activity in a variety of
regions and ecosystems, with variable timing. Overall, this
study provides the first global decadal assessment of spatialtemporal
fire variability and confirms the usefulness of the
screened WFA for global fire ecoclimatology researc
Hybrid Meson Decay Phenomenology
The phenomenology of a newly developed model of hybrid meson decay is
developed. The decay mechanism is based on the heavy quark expansion of QCD and
the strong coupling flux tube picture of nonperturbative glue. A comprehensive
list of partial decay widths of a wide variety of light, , ,
and hybrid mesons is presented. Results which appear approximately
universal are highlighted along with those which distinguish different hybrid
decay models. Finally, we examine several interesting hybrid candidates in
detail.Comment: 37 pages, 2 figures, 6 tables, Revte
Identification of patients with atrial fibrillation in UK community pharmacy: an evaluation of a new service
Background: Many patients with atrial fibrillation (AF) are asymptomatic and diagnosed via opportunistic screening. Community pharmacy has been advocated as a potential resource for opportunistic screening and lifestyle interventions. Objective: The objective of this evaluation is to describe the outcomes from an AF service, in terms of referrals and interventions provided to patients identified as not at risk. Method: Eligibility was assessed from pharmacy records and the completion of a short questionnaire. Once consented, patients were screened for AF and their blood pressure was measured. Results: Of 594 patients screened, nine were identified as at risk of having AF and were referred to their GP. The service also identified 109 patients with undiagnosed hypertension, 176 patients with a Body Mass Index (BMI) > 30, 131 with an Audit-C score > 5 and 59 smokers. Pharmacists provided 413 interventions in 326 patients aimed at weight reduction (239), alcohol consumption (123) and smoking cessation (51). Conclusion: This evaluation characterises the interventions provided to, not only those identified with the target condition - in this case AF - but also those without it. The true outcome of these additional interventions, along with appropriate follow-up, should be the focus of future studies.Impact of findings on patients or practice •Patients are willing to be screened for AF through community pharmacies•Screening can provide opportunities to identify other healthcare problems such a hypertension or poor lifestyle •Community pharmacists are able to provide brief advice to patients as a result of this opportunistic screenin
The far-infrared/radio correlation and radio spectral index of galaxies in the SFR-M* plane up to z 2
[Abridged] We study the evolution of the radio spectral index and
far-infrared/radio correlation (FRC) across the star-formation rate-stellar
masse (i.e. SFR-M*) plane up to z 2. We start from a M*-selected sample of
galaxies with reliable SFR and redshift estimates. We then grid the SFR-M*
plane in several redshift ranges and measure the infrared luminosity, radio
luminosity, radio spectral index, and ultimately the FRC index (i.e. qFIR) of
each SFR-M*-z bin. The infrared luminosities of our SFR-M*-z bins are estimated
using their stacked far-infrared flux densities inferred from observations
obtained with Herschel. Their radio luminosities and radio spectral indices
(i.e. alpha, where Snu nu^-alpha) are estimated using their stacked 1.4GHz and
610MHz flux densities from the VLA and GMRT, respectively. Our far-infrared and
radio observations include the most widely studied blank extragalactic fields
-GOODS-N/S, ECDFS, and COSMOS- covering a sky area of 2deg^2. Using this
methodology, we constrain the radio spectral index and FRC index of
star-forming galaxies with M*>10^10Msun and 0<z<2.3. We find that
alpha^1.4GHz_610MHz does not evolve significantly with redshift or with the
distance of a galaxy with respect to the main sequence (MS) of the SFR-M* plane
(i.e. Delta_log(SSFR)_MS=log[SSFR(galaxy)/SSFR_MS(M*,z)]). Instead,
star-forming galaxies have a radio spectral index consistent with a canonical
value of 0.8, which suggests that their radio spectra are dominated by
non-thermal optically thin synchrotron emission. We find that qFIR displays a
moderate but statistically significant redshift evolution as
qFIR(z)=(2.35+/-0.08)*(1+z)^(-0.12+/-0.04), consistent with some previous
literature. Finally, we find no significant correlation between qFIR and
Delta_log(SSFR)_MS, though a weak positive trend, as observed in one of our
redshift bins, cannot be firmly ruled out using our dataset.Comment: Accepted for publication in A&A; 18 pages, 10 figure
Panchromatic spectral energy distributions of Herschel sources
(abridged) Far-infrared Herschel photometry from the PEP and HerMES programs
is combined with ancillary datasets in the GOODS-N, GOODS-S, and COSMOS fields.
Based on this rich dataset, we reproduce the restframe UV to FIR ten-colors
distribution of galaxies using a superposition of multi-variate Gaussian modes.
The median SED of each mode is then fitted with a modified version of the
MAGPHYS code that combines stellar light, emission from dust heated by stars
and a possible warm dust contribution heated by an AGN. The defined Gaussian
grouping is also used to identify rare sources. The zoology of outliers
includes Herschel-detected ellipticals, very blue z~1 Ly-break galaxies,
quiescent spirals, and torus-dominated AGN with star formation. Out of these
groups and outliers, a new template library is assembled, consisting of 32 SEDs
describing the intrinsic scatter in the restframe UV-to-submm colors of
infrared galaxies. This library is tested against L(IR) estimates with and
without Herschel data included, and compared to eight other popular methods
often adopted in the literature. When implementing Herschel photometry, these
approaches produce L(IR) values consistent with each other within a median
absolute deviation of 10-20%, the scatter being dominated more by fine tuning
of the codes, rather than by the choice of SED templates. Finally, the library
is used to classify 24 micron detected sources in PEP GOODS fields. AGN appear
to be distributed in the stellar mass (M*) vs. star formation rate (SFR) space
along with all other galaxies, regardless of the amount of infrared luminosity
they are powering, with the tendency to lie on the high SFR side of the "main
sequence". The incidence of warmer star-forming sources grows for objects with
higher specific star formation rates (sSFR), and they tend to populate the
"off-sequence" region of the M*-SFR-z space.Comment: Accepted for publication in A&A. Some figures are presented in low
resolution. The new galaxy templates are available for download at the
address http://www.mpe.mpg.de/ir/Research/PEP/uvfir_temp
The Specific Heat of Normal, Degenerate Quark Matter: Non-Fermi Liquid Corrections
In normal degenerate quark matter, the exchange of dynamically screened
transverse gluons introduces infrared divergences in the quark self-energies
that lead to the breakdown of the Fermi liquid description. If the core of
neutron stars are composed of quark matter with a normal component, cooling by
direct quark Urca processes may be modified by non-Fermi liquid corrections. We
find that while the quasiparticle density of states is finite and non-zero at
the Fermi surface, its frequency derivative diverges and results in non-Fermi
liquid corrections to the specific heat of the normal, degenerate component of
quark matter. We study these non-perturbative non-Fermi liquid corrections to
the specific heat and the temperature dependence of the chemical potential and
show that these lead to a reduction of the specific heat.Comment: new discussion, updated references, accepted in PR
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