394 research outputs found
Exorcizing the Landau Ghost in Non Commutative Quantum Field Theory
We show that the simplest non commutative renormalizable field theory, the
model on four dimensional Moyal space with harmonic potential is
asymptotically safe to all orders in perturbation theor
Innovative Approaches to Analysing Carbon Sequestration as a Mitigation Strategy in Tropical Pasture Landscapes in Two Emblematic Contexts, the Amazon and the West African Sahel
The relationship between ruminant production systems and climate change is complex. As a major contributor to greenhouse gas (GHG) emissions, the sector has been the subject of considerable controversy, with particularly severe criticism in the 2000s. However, ten years ago, the attitude towards grazing lands began to change. Their efficient use of non-renewable energy and their contribution to carbon (C) sequestration were considered as key factors in the new environmental challenge. The reality of this mitigation potential was recently called into question once again in the global agriculture and climate change debate, including that of sequestration in the soil where grazing lands occupy a major position (30-40% of the land surface representing 30% of the soil organic C of the world). Few scientific references are available on these questions in tropical regions, and the standard metrics and methods used may turn out to be unsuitable for the correct evaluation of grazed ecosystems in these regions. Significant work is therefore required to establish baselines and design strategies to ensure sustainable grazing in these regions where the global sequestration potential is high relative to the surface areas concerned.
To contribute to this debate, we focus on mitigation options offered by rangelands and grasslands and their management in two emblematic tropical contexts, humid and dry tropics, where field studies have been based on original and holistic approaches at different levels. In Amazonia, if curbing deforestation remains a priority, it needs to be accompanied by sustainable management of deforested areas. In the French Amazon (French Guiana), monitoring fields using chronosequences and flux towers has produced scientific knowledge on the significant mitigation capacities of grassland ecosystems. In the Brazilian Amazon, the spatial logic of the agro-ecological intensification of forage production has enabled a transition from individual extractive systems to farm management at communal levels. In the West African Sahelian region (Northern Senegal), an integrative study at landscape scale revealed the unexpected capacity of soil and shrubs for C sequestration that can offset the GHG emissions for which pastoralism in dry tropical zones is usually blamed
One-loop Beta Functions for the Orientable Non-commutative Gross-Neveu Model
We compute at the one-loop order the beta-functions for a renormalisable
non-commutative analog of the Gross Neveu model defined on the Moyal plane. The
calculation is performed within the so called x-space formalism. We find that
this non-commutative field theory exhibits asymptotic freedom for any number of
colors. The beta-function for the non-commutative counterpart of the Thirring
model is found to be non vanishing.Comment: 16 pages, 9 figure
Vacuum configurations for renormalizable non-commutative scalar models
In this paper we find non-trivial vacuum states for the renormalizable
non-commutative model. An associated linear sigma model is then
considered. We further investigate the corresponding spontaneous symmetry
breaking.Comment: 17 page
Renormalization of the commutative scalar theory with harmonic term to all orders
The noncommutative scalar theory with harmonic term (on the Moyal space) has
a vanishing beta function. In this paper, we prove the renormalizability of the
commutative scalar field theory with harmonic term to all orders by using
multiscale analysis in the momentum space. Then, we consider and compute its
one-loop beta function, as well as the one on the degenerate Moyal space. We
can finally compare both to the vanishing beta function of the theory with
harmonic term on the Moyal space.Comment: 16 page
Construction of chromosome segmen substitution lines in peanut (Arachis hypogaea L.) using a wild synthetic and QTL mapping for plant morphology.
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Relapsing macrophage activating syndrome in a 15-year-old girl with Still's disease: a case report
<p>Abstract</p> <p>Introduction</p> <p>Macrophage activating syndrome is a severe, potentially life-threatening condition that may accompany Still's disease. It is characterized by fever, hepatosplenomegaly, lymphadenopathy, severe cytopenia, serious liver dysfunction, coagulopathy and neurologic involvement. The principal treatment for patients with this syndrome includes etoposide 150 mg/2 M twice a week for two weeks, dexamethasone 10 mg/2 M for two weeks and cyclosporine 3 mg/kg to 5 mg/kg for a longer period. Cases of relapse of macrophage activating syndrome are relatively rare.</p> <p>Case presentation</p> <p>We describe the case of a 15-year-old Iraqi girl with Still's disease who developed macrophage activating syndrome with acute respiratory distress syndrome that required resuscitation and mechanical ventilation. Following intensive treatment, including high dose steroids and cyclosporine, the patient improved significantly. Two weeks after cyclosporine was discontinued, however, she was readmitted with an acute relapse of macrophage activating syndrome manifested by spiking fever, arthralgias, maculopapular rash and leukocytosis. This time the patient recovered following the reintroduction of treatment with cyclosporine and the addition of mycophenolate mofetil (Cellcept).</p> <p>Conclusion</p> <p>We believe that cyclosporine is a cornerstone for the treatment of Still's disease. We recommend continuing this medication for several weeks following the patient's clinical recovery in order to prevent macrophage activating syndrome relapses.</p
A translation-invariant renormalizable non-commutative scalar model
In this paper we propose a translation-invariant scalar model on the Moyal
space. We prove that this model does not suffer from the UV/IR mixing and we
establish its renormalizability to all orders in perturbation theory.Comment: 17 pages, 3 figure
Star-spot activity, orbital obliquity, transmission spectrum, physical properties, and TTVs of the HATS-2 planetary system
Our aim in this paper is to refine the orbital and physical parameters of the
HATS-2 planetary system and study transit timing variations and atmospheric
composition thanks to transit observations that span more than ten years and
that were collected using different instruments and pass-band filters. We also
investigate the orbital alignment of the system by studying the anomalies in
the transit light curves induced by starspots on the photosphere of the parent
star. We analysed new transit events from both ground-based telescopes and
NASA's TESS mission. Anomalies were detected in most of the light curves and
modelled as starspots occulted by the planet during transit events. We fitted
the clean and symmetric light curves with the JKTEBOP code and those affected
by anomalies with the PRISM+GEMC codes to simultaneously model the photometric
parameters of the transits and the position, size, and contrast of each
starspot. We found consistency between the values we found for the physical and
orbital parameters and those from the discovery paper and ATLAS9 stellar
atmospherical models. We identified different sets of consecutive
starspot-crossing events that temporally occurred in less than five days. Under
the hypothesis that we are dealing with the same starspots, occulted twice by
the planet during two consecutive transits, we estimated the rotational period
of the parent star and, in turn the projected and the true orbital obliquity of
the planet. We find that the system is well aligned. We identified the possible
presence of transit timing variations in the system, which can be caused by
tidal orbital decay, and we derived a low-resolution transmission spectrum.Comment: 23 pages, 21 figures, Accepted for publication in Astronomy &
Astrophysic
Translation-invariant models for non-commutative gauge fields
Motivated by the recent construction of a translation-invariant
renormalizable non-commutative model for a scalar field (see arXiv:0802.0791
[math-ph]), we introduce models for non-commutative U(1) gauge fields along the
same lines. More precisely, we include some extra terms into the action with
the aim of getting rid of the UV/IR mixing.Comment: 9 page
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