1,398 research outputs found
Fire Management In Veredas (palm Swamps): New Perspectives On Traditional Farming Systems In Jalapão, Brazil
The veredas (palm swamps) of the cerrado biome are legally protected as áreas de Preservação Permanente (Permanent Preservation Areas), and the use of fire in these wetlands is prohibited. We carried out a preliminary assessment of environmental impacts of the local use of agricultural fire in veredas through a collaborative research project in Jalapão (Tocantins, Brazil). We found that "roças de esgoto" (drained peat swamp swidden fields) form the basis of the agricultural system of this region. These fields ensure production throughout the year, provide more income than "roças de toco" (rainfed swidden fields), and may function as a repository of agrobiodiversity on a regional scale. This study suggests that the use of fire in veredas associated with roças de esgoto does not lead to significant deforestation, that is, to the disappearance of the forest physiognomy, but instead helps maintain tree cover during the fallow period, possibly accelerating natural succession.19326929
Preliminary Results of Post-Disaster Archaeological Investigations at the Kasthamandap and within Hanuman Dhoka, Kathmandu Valley UNESCO World Heritage Property (Nepal)
QED Effective Action at Finite Temperature: Two-Loop Dominance
We calculate the two-loop effective action of QED for arbitrary constant
electromagnetic fields at finite temperature T in the limit of T much smaller
than the electron mass. It is shown that in this regime the two-loop
contribution always exceeds the influence of the one-loop part due to the
thermal excitation of the internal photon. As an application, we study light
propagation and photon splitting in the presence of a magnetic background field
at low temperature. We furthermore discover a thermally induced contribution to
pair production in electric fields.Comment: 34 pages, 4 figures, LaTe
First-principles Calculation of the Formation Energy in MgO-CaO Solid Solutions
The electronic structure and total energy were calculated for ordered and
disordered MgO-CaO solid solutions within the multiple scattering theory in
real space and the local density approximation. Based on the dependence of the
total energy on the unit cell volume the equilibrium lattice parameter and
formation energy were determined for different solution compositions. The
formation energy of the solid solutions is found to be positive that is in
agreement with the experimental phase diagram, which shows a miscibility gap.Comment: 11 pages, 3 figure
Conductance oscillations of a spin-orbit stripe with polarized contacts
We investigate the linear conductance of a stripe of spin-orbit interaction
in a 2D electron gas; that is, a 2D region of length along the transport
direction and infinite in the transverse one in which a spin-orbit interaction
of Rashba type is present. Polarization in the contacts is described by means
of Zeeman fields. Our model predicts two types of conductance oscillations:
Ramsauer oscillations in the minority spin transmission, when both spins can
propagate, and Fano oscillations when only one spin propagates. The latter are
due to the spin-orbit coupling with quasibound states of the non propagating
spin. In the case of polarized contacts in antiparallel configuration Fano-like
oscillations of the conductance are still made possible by the spin orbit
coupling, even though no spin component is bound by the contacts. To describe
these behaviors we propose a simplified model based on an ansatz wave function.
In general, we find that the contribution for vanishing transverse momentum
dominates and defines the conductance oscillations. Regarding the oscillations
with Rashba coupling intensity, our model confirms the spin transistor
behavior, but only for high degrees of polarization. Including a position
dependent effective mass yields additional oscillations due to the mass jumps
at the interfaces.Comment: 8.5 pages, 9 figure
Fokker-Planck equations and density of states in disordered quantum wires
We propose a general scheme to construct scaling equations for the density of
states in disordered quantum wires for all ten pure Cartan symmetry classes.
The anomalous behavior of the density of states near the Fermi level for the
three chiral and four Bogoliubov-de Gennes universality classes is analysed in
detail by means of a mapping to a scaling equation for the reflection from a
quantum wire in the presence of an imaginary potential.Comment: 10 pages, 5 figures, revised versio
Remote detection of past habitability at Mars-analogue hydrothermal alteration terrains using an ExoMars Panoramic Camera emulator
JKH is funded by a Birkbeck University of London Graduate Teaching Assistantship. CRC is funded by a Royal Society of Edinburgh Personal Research Fellowship co-funded by Marie Curie Actions. The Aberystwyth research leading to these results has been funded by the UK Space Agency, ExoMars Panoramic Camera (PanCam) Grant Nos. ST/G003114/1, ST/I002758/1, STL001454/1, and the UK Space Agency CREST2 PanCam-2020 research Grant No. ST/L00500X/1. Additional Aberystwyth funding has come from The European Community’s Seventh Framework Programme (FP7/2007-2013), Grant Agreement Nos. 21881 PRoVisG, 241523 PRoViScout, and Grant Agreement No. 312377 PRoViDE. PMG is funded by a UK Space Agency Aurora Fellowship (grants ST/J005215/1 and ST/L00254X/1).A major scientific goal of the European Space Agency’s ExoMars 2018 rover is to identify evidence of life within the martian rock record. Key to this objective is the remote detection of geological substrates that are indicative of past habitable environments, which will rely on visual (stereo wide-angle, and high resolution images) and multispectral (440–1000 nm) data produced by the Panoramic Camera (PanCam) instrument. We deployed a PanCam emulator at four hydrothermal sites in the Námafjall volcanic region of Iceland, a Mars-analogue hydrothermal alteration terrain. At these sites, sustained acidic–neutral aqueous interaction with basaltic substrates (crystalline and sedimentary) has produced phyllosilicate, ferric oxide, and sulfate-rich alteration soils, and secondary mineral deposits including gypsum veins and zeolite amygdales. PanCam emulator datasets from these sites were complemented with (i) NERC Airborne Research and Survey Facility aerial hyperspectral images of the study area; (ii) in situ reflectance spectroscopy (400–1000 nm) of PanCam spectral targets; (iii) laboratory X-ray Diffraction, and (iv) laboratory VNIR (350–2500 nm) spectroscopy of target samples to identify their bulk mineralogy and spectral properties. The mineral assemblages and palaeoenvironments characterised here are analogous to neutral–acidic alteration terrains on Mars, such as at Mawrth Vallis and Gusev Crater. Combined multispectral and High Resolution Camera datasets were found to be effective at capturing features of astrobiological importance, such as secondary gypsum and zeolite mineral veins, and phyllosilicate-rich substrates. Our field observations with the PanCam emulator also uncovered stray light problems which are most significant in the NIR wavelengths and investigations are being undertaken to ensure that the flight model PanCam cameras are not similarly affected.Publisher PDFPeer reviewe
2023 EULAR recommendations on imaging in diagnosis and management of crystal-induced arthropathies in clinical practice.
To formulate evidence-based recommendations and overarching principles on the use of imaging in the clinical management of crystal-induced arthropathies (CiAs).
An international task force of 25 rheumatologists, radiologists, methodologists, healthcare professionals and patient research partners from 11 countries was formed according to the EULAR standard operating procedures. Fourteen key questions on the role of imaging in the most common forms of CiA were generated. The CiA assessed included gout, calcium pyrophosphate deposition disease and basic calcium phosphate deposition disease. Imaging modalities included conventional radiography, ultrasound, CT and MRI. Experts applied research evidence obtained from four systematic literature reviews using MEDLINE, EMBASE and CENTRAL. Task force members provided level of agreement (LoA) anonymously by using a Numerical Rating Scale from 0 to 10.
Five overarching principles and 10 recommendations were developed encompassing the role of imaging in various aspects of patient management: making a diagnosis of CiA, monitoring inflammation and damage, predicting outcome, response to treatment, guided interventions and patient education. Overall, the LoA for the recommendations was high (8.46-9.92).
These are the first recommendations that encompass the major forms of CiA and guide the use of common imaging modalities in this disease group in clinical practice
Advances in ab-initio theory of Multiferroics. Materials and mechanisms: modelling and understanding
Within the broad class of multiferroics (compounds showing a coexistence of
magnetism and ferroelectricity), we focus on the subclass of "improper
electronic ferroelectrics", i.e. correlated materials where electronic degrees
of freedom (such as spin, charge or orbital) drive ferroelectricity. In
particular, in spin-induced ferroelectrics, there is not only a {\em
coexistence} of the two intriguing magnetic and dipolar orders; rather, there
is such an intimate link that one drives the other, suggesting a giant
magnetoelectric coupling. Via first-principles approaches based on density
functional theory, we review the microscopic mechanisms at the basis of
multiferroicity in several compounds, ranging from transition metal oxides to
organic multiferroics (MFs) to organic-inorganic hybrids (i.e. metal-organic
frameworks, MOFs)Comment: 22 pages, 9 figure
Spallation reactions. A successful interplay between modeling and applications
The spallation reactions are a type of nuclear reaction which occur in space
by interaction of the cosmic rays with interstellar bodies. The first
spallation reactions induced with an accelerator took place in 1947 at the
Berkeley cyclotron (University of California) with 200 MeV deuterons and 400
MeV alpha beams. They highlighted the multiple emission of neutrons and charged
particles and the production of a large number of residual nuclei far different
from the target nuclei. The same year R. Serber describes the reaction in two
steps: a first and fast one with high-energy particle emission leading to an
excited remnant nucleus, and a second one, much slower, the de-excitation of
the remnant. In 2010 IAEA organized a worskhop to present the results of the
most widely used spallation codes within a benchmark of spallation models. If
one of the goals was to understand the deficiencies, if any, in each code, one
remarkable outcome points out the overall high-quality level of some models and
so the great improvements achieved since Serber. Particle transport codes can
then rely on such spallation models to treat the reactions between a light
particle and an atomic nucleus with energies spanning from few tens of MeV up
to some GeV. An overview of the spallation reactions modeling is presented in
order to point out the incomparable contribution of models based on basic
physics to numerous applications where such reactions occur. Validations or
benchmarks, which are necessary steps in the improvement process, are also
addressed, as well as the potential future domains of development. Spallation
reactions modeling is a representative case of continuous studies aiming at
understanding a reaction mechanism and which end up in a powerful tool.Comment: 59 pages, 54 figures, Revie
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