1,730 research outputs found
Measuring and monitoring linear woody features in agricultural landscapes through earth observation data as an indicator of habitat availability
AbstractThe loss of natural habitats and the loss of biological diversity is a global problem affecting all ecosystems including agricultural landscapes. Indicators of biodiversity can provide standardized measures that make it easier to compare and communicate changes to an ecosystem. In agricultural landscapes the amount and variety of available habitat is directly correlated with biodiversity levels. Linear woody features (LWF), including hedgerows, windbreaks, shelterbelts as well as woody shrubs along fields, roads and watercourses, play a vital role in supporting biodiversity as well as serving a wide variety of other purposes in the ecosystem. Earth observation can be used to quantify and monitor LWF across the landscape. While individual features can be manually mapped, this research focused on the development of methods using line intersect sampling (LIS) for estimating LWF as an indicator of habitat availability in agricultural landscapes. The methods are accurate, efficient, repeatable and provide robust results. Methods were tested over 9.5Mha of agricultural landscape in the Canadian Mixedwood Plains ecozone. Approximately 97,000km of LWF were estimated across this landscape with results useable both at a regional reporting scale, as well as mapped across space for use in wildlife habitat modelling or other landscape management research. The LIS approach developed here could be employed at a variety of scales in particular for large regions and could be adapted for use as a national scale indicator of habitat availability in heavily disturbed agricultural landscape
Discovery of a Very Young Field L Dwarf, 2MASS J01415823-4633574
While following up L dwarf candidates selected photometrically from the Two
Micron All Sky Survey, we uncovered an unusual object designated 2MASS
J01415823-4633574. Its optical spectrum exhibits very strong bands of vanadium
oxide but abnormally weak absorptions by titanium oxide, potassium, and sodium.
Morphologically such spectroscopic characteristics fall intermediate between
old, field early-L dwarfs (log(g)~5) and very late M giants (log(g)~0), leading
us to favor low gravity as the explanation for the unique spectral signatures
of this L dwarf. Such a low gravity can be explained only if this L dwarf is
much lower in mass than a typical old field L dwarf of similar temperature and
is still contracting to its final radius. These conditions imply a very young
age. Further evidence of youth is found in the near-infrared spectrum,
including a triangular-shaped H-band continuum reminiscent of young brown dwarf
candidates discovered in the Orion Nebula Cluster. Using the above information
along with comparisons to brown dwarf atmospheric and interior models, our
current best estimate is that this L dwarf has an age of 1-50 Myr and a mass of
6-25 M_Jupiter. The location of 2MASS 0141-4633 on the sky coupled with a
distance estimate of ~35 pc and the above age estimate suggests that this
object may be a brown dwarf member of either the 30-Myr-old Tucana/Horologium
Association or the ~12-Myr-old beta Pic Moving Group.Comment: Accepted for publication in the 10 March 2006 issue (volume 639) of
the Astrophysical Journa
Effective Field Theory Dimensional Regularization
A Lorentz-covariant regularization scheme for effective field theories with
an arbitrary number of propagating heavy and light particles is given. This
regularization scheme leaves the low-energy analytic structure of Greens
functions intact and preserves all the symmetries of the underlying Lagrangian.
The power divergences of regularized loop integrals are controlled by the
low-energy kinematic variables. Simple diagrammatic rules are derived for the
regularization of arbitrary one-loop graphs and the generalization to higher
loops is discussed.Comment: 22 pages, 11 figures and 1 tabl
Spin structure of the nucleon at low energies
The spin structure of the nucleon is analyzed in the framework of a
Lorentz-invariant formulation of baryon chiral perturbation theory. The
structure functions of doubly virtual Compton scattering are calculated to
one-loop accuracy (fourth order in the chiral expansion). We discuss the
generalization of the Gerasimov-Drell-Hearn sum rule, the Burkhardt-Cottingham
sum rule and moments of these. We give predictions for the forward and the
longitudinal-transverse spin polarizabilities of the proton and the neutron at
zero and finite photon virtuality. A detailed comparison to results obtained in
heavy baryon chiral perturbation theory is also given.Comment: 29 pp, 14 fig
Identification and quantitation of tumour cells in cell suspensions: a comparison of cytology and flow cytometry.
A new window on Strange Quark Matter as the ground state of strongly interacting matter
If strange quark matter is the true ground state of matter, it must have
lower energy than nuclear matter. Simultaneously, two-flavour quark matter must
have higher energy than nuclear matter, for otherwise the latter would convert
to the former. We show, using an effective chiral lagrangian, that the
existence of a new lower energy ground state for two-flavour quark matter, the
pion condensate, shrinks the window for strange quark matter to be the ground
state of matter and sets new limits on the current strange quark mass
Strangeness, charm and bottom in a chiral quark-meson model
In this paper we investigate an SU(3) extension of the chiral quark-meson
model. The spectra of baryons with strangeness, charm and bottom are considered
within a "rigid oscillator" version of this model. The similarity between the
quark part of the Lagrangian in the model and the Wess-Zumino term in the
Skyrme model is noted. The binding energies of baryonic systems with baryon
number B=2 and 3 possessing strangeness or heavy flavor are estimated. The
results obtained are in good qualitative agreement with those obtained
previously in the topological soliton (Skyrme) model.Comment: 12 pages, no figures. Journal ref: submitted to Nucl.Phys.
Predictive powers of chiral perturbation theory in Compton scattering off protons
We study low-energy nucleon Compton scattering in the framework of baryon
chiral perturbation theory (BPT) with pion, nucleon, and (1232)
degrees of freedom, up to and including the next-to-next-to-leading order
(NNLO). We include the effects of order , and , with
MeV the -resonance excitation energy. These are
all "predictive" powers in the sense that no unknown low-energy constants enter
until at least one order higher (i.e, ). Estimating the theoretical
uncertainty on the basis of natural size for effects, we find that
uncertainty of such a NNLO result is comparable to the uncertainty of the
present experimental data for low-energy Compton scattering. We find an
excellent agreement with the experimental cross section data up to at least the
pion-production threshold. Nevertheless, for the proton's magnetic
polarizability we obtain a value of fm, in
significant disagreement with the current PDG value. Unlike the previous
PT studies of Compton scattering, we perform the calculations in a
manifestly Lorentz-covariant fashion, refraining from the heavy-baryon (HB)
expansion. The difference between the lowest order HBPT and BPT
results for polarizabilities is found to be appreciable. We discuss the chiral
behavior of proton polarizabilities in both HBPT and BPT with the
hope to confront it with lattice QCD calculations in a near future. In studying
some of the polarized observables, we identify the regime where their naive
low-energy expansion begins to break down, thus addressing the forthcoming
precision measurements at the HIGS facility.Comment: 24 pages, 9 figures, RevTeX4, revised version published in EPJ
Multi-Agent System (MAS) Applications in Ambient Intelligence (AmI) Environments
Proceedings of: 8th Conference on Practical Applications of Agents and Multi-Agent Systems (PAAMS`10). Salamanca (Spain), 28-30 April 2010Research in context-aware systems has been moving towards reusable and adaptable architectures for managing more advanced human-computer interfaces. Ambient. Intelligence (AmI) investigates computer-based services, which are ubiquitous and based on a variety of objects and devices. Their intelligent and intuitive interfaces act as mediators through which people can interact with the ambient environment. In this paper we present an agent-based architecture which supports the execution of agents in AmI environments. Two case studies are also presented, an airport information system and a railway information system, which uses spoken conversational agents to respond to the user's requests using the contextual information that includes the location information of the user.This work has been partially supported by CICYT TIN2008-06742-C02-02/TSI, CICYT TEC2008-06732-C02-02/TEC, SINPROB, CAM MADRINET S-0505/TIC/0255 and DPS2008-07029-C02-02Publicad
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