2,092 research outputs found
Canonical Realizations of Doubly Special Relativity
Doubly Special Relativity is usually formulated in momentum space, providing
the explicit nonlinear action of the Lorentz transformations that incorporates
the deformation of boosts. Various proposals have appeared in the literature
for the associated realization in position space. While some are based on
noncommutative geometries, others respect the compatibility of the spacetime
coordinates. Among the latter, there exist several proposals that invoke in
different ways the completion of the Lorentz transformations into canonical
ones in phase space. In this paper, the relationship between all these
canonical proposals is clarified, showing that in fact they are equivalent. The
generalized uncertainty principles emerging from these canonical realizations
are also discussed in detail, studying the possibility of reaching regimes
where the behavior of suitable position and momentum variables is classical,
and explaining how one can reconstruct a canonical realization of doubly
special relativity starting just from a basic set of commutators. In addition,
the extension to general relativity is considered, investigating the kind of
gravity's rainbow that arises from this canonical realization and comparing it
with the gravity's rainbow formalism put forward by Magueijo and Smolin, which
was obtained from a commutative but noncanonical realization in position space.Comment: 18 pages, accepted for publication in International Journal of Modern
Physics
Odor-driven attractor dynamics in the antennal lobe allow for simple and rapid olfactory pattern classification
The antennal lobe plays a central role for odor processing in insects, as demonstrated by electrophysiological and imaging experiments. Here we analyze the detailed temporal evolution of glomerular activity patterns in the antennal lobe of honeybees. We represent these spatiotemporal patterns as trajectories in a multidimensional space, where each dimension accounts for the activity of one glomerulus. Our data show that the trajectories reach odor-specific steady states (attractors) that correspond to stable activity patterns at about 1 second after stimulus onset. As revealed by a detailed mathematical investigation, the trajectories are characterized by different phases: response onset, steady-state plateau, response offset, and periods of spontaneous activity. An analysis based on support-vector machines quantifies the odor specificity of the attractors and the optimal time needed for odor discrimination. The results support the hypothesis of a spatial olfactory code in the antennal lobe and suggest a perceptron-like readout mechanism that is biologically implemented in a downstream network, such as the mushroom body
Sensory memory for odors is encoded in spontaneous correlated activity between olfactory glomeruli
Sensory memory is a short-lived persistence of a sensory stimulus in the nervous system, such as iconic memory in the visual system. However, little is known about the mechanisms underlying olfactory sensory memory. We have therefore analyzed the effect of odor stimuli on the first odor-processing network in the honeybee brain, the antennal lobe, which corresponds to the vertebrate olfactory bulb. We stained output neurons with a calcium-sensitive dye and measured across-glomerular patterns of spontaneous activity before and after a stimulus. Such a single-odor presentation changed the relative timing of spontaneous activity across glomeruli in accordance with Hebb's theory of learning. Moreover, during the first few minutes after odor presentation, correlations between the spontaneous activity fluctuations suffice to reconstruct the stimulus. As spontaneous activity is ubiquitous in the brain, modifiable fluctuations could provide an ideal substrate for Hebbian reverberations and sensory memory in other neural systems
Comparison between Airborne Pollen and Aeroallergen Quantification with the ChemVol Impact Sampler. Olive pollen vs Ole e 1
Comparison between Airborne Pollen and Aeroallergen Quantification with the ChemVol Impact Sampler. Olive pollen vs Ole e 1.
Torres M.C.1, C. Antunes2, M.J. Velasco1, R. Ferro2, H. García-Mozo1, R. Ribeiro2, R.Brandao3, Galán, C1 and the HIALINE team4
1Department of Botany, Ecology and Plant Physiology, University of Córdoba
2Department of Chemistry, University of Évora, Portugal
3Department of Biology, University of Évora, Portugal
4J.T.M. Buters, Germany, M. Thibaudon, France, M. Smith, Great Britain, C. Galan, Spain, R. Brandao and C. Antunes, Portugal, G. Reese, Germany, R. Albertini, Italy, L. Grewling, Poland, A. Rantio-Lehtimäki, Finland, S. Jäger and U. Berger, Austria, I. Sauliene, Lithuania, L. Cecchi, Italy
Nowadays, pollinosis is affecting a large percentage of population in the countries with a western life style. The existence of allergenic activity in the atmosphere is not only associated to pollen grains and fungal spores, but also to submicronic and paucimicronic biological particles. The origin of these allergens can be due to the rupture of pollen transported in the atmosphere or to the presence of allergens from other parts of the plant making amorphous material with an allergen load.
Olive pollen is recognized as one of the main causes of allergic disease in the Mediterranean area. In this study we have tried to compare olive pollen count in the air and Ole e 1 as major allergen of this species, at two different localities in South of Europe: Evora (Portugal) and Córdoba (Spain). At each location both samplers were placed side-by-side.
Pollen grains have been sampled using a volumetric Hirst type spore trap. Chemvol high-volume cascade impactor equipped with stages PM>10µm, 10 µm>PM>2.5µm were used for detecting aeroallergens. Ole e 1 major allergen was determined using allergen specific ELISA´s.
Similar behaviour between pollen and the total allergenic load was observed during the pollen season. Nevertheless, at some occasions, during the previous and later period of the pollen season, airborne allergenic load was detected in South Spain, due to the contributions from other Oleaceae species. For this reason the use of these two different methodologies allow a better understanding of the allergenic load in the atmosphere.
This work was supported in part by the European Agency for Health and Consumers EAHC, Luxembourg, under the grant agreement 20081107
Comparison between Poaceae Airborne Pollen Counts and Phl p5 Aeroallergen Quantification in South Europe
The European project HIALINE: Comparison between Poaceae Airborne Pollen Counts and Phl p5 Aeroallergen Quantification in South Europe
C. Antunes1,2, R. Ferro2, R. Ribeiro2, Torres M.C.4, M.J. Velasco4H. García-Mozo4, Galán, C4 , R.Brandao1,3, M.Thibaudon5, R. Albertini6 Ugolotti. M.6, Usberti I.6, Dall’Aglio P.6 and the HIALINE team7
1DInstitute of Mediterranean Agricultural and Environmental Sciences –ICAAM, University of Évora, Portugal
2Department of Chemistry, University of Évora, Portugal
3Department of Biology, University of Évora, Portugal
4Department of Botany, Ecology and Plant Physiology, University of Córdoba
5Réseau National de l Surveillance Aerobiologique, Saint-Genis-l’Argentière, France
6Department of Clinical Medicine, Nephrology and Health Sciences, University of Parma, Italy
7J.T.M. Buters, Germany, M. Thibaudon, France, M. Smith, Great Britain, C. Galan, Spain, R. Brandao and C.M. Antunes, Portugal, G. Reese, Germany, R. Albertini, Italy, L. Grewling, Poland, A. Rantio-Lehtimäki, Finland, S. Jäger and U. Berger, Austria, I. Sauliene, Lithuania, L. Cecchi, Italy
Introduction: Nowadays, pollinosis is affecting a large percentage of population in countries with a western life style. The existence of allergenic activity in the atmosphere is not only associated to pollen grains and fungal spores, but also to submicronic and paucimicronic biological particles. The origin of these allergens can be due to the rupture of pollen transported in the atmosphere or to the presence of allergens from other parts of the plant making amorphous material with an allergen load. Poaceae pollen is recognized as one of the main causes of allergic disease in all Europe. In this study we have tried to compare Poaceae pollen counts in the air and Phl p 5, one of the major allergens of this family, through the use of a high-volume cascade impactor (Chemvol). This study was done in the frame of the European project HIALINE and it compares the results obtained in 2009 by 4 different partners participating in this project: in Córdoba (Spain), Évora (Portugal), Lyon (France) and Parma (Italy).
Methodology: Pollen grains were sampled using a 7-day volumetric Hirst type spore trap. Chemvol high-volume cascade impactor equipped with stages PM>10µm, 10 µm>PM>2.5µm was used for detecting aeroallergens. In each stage polyurethane filters were use as an impacting substrate. Phl p 5 allergen was determined using an allergen specific ELISA. Antibodies for analysis were delivered by Allergopharma Joachim Ganzer KG, the industrial partner in this project. At each location both samplers were placed side-by-side.
Results: Most of the allergen was collected in the PM>10µm fraction. Similar profiles between airborne pollen and the total allergenic load was observed during the pollen season. A good correlation was obtained between pollen count and allergen content of the air and a value of 2.5 pg/pollen grain of Poaceae was estimated.
Discussion: This is the first year of this project. Nevertheless, results suggest that the allergenic load in outdoor air might be mainly due to pollen bursts. It supports the hypothesis that monitoring the allergens itself in ambient air might be an improvement in allergen exposure assessment.
This work was supported in part by the European Agency for Health and Consumers EAHC, Luxembourg, under the grant agreement 2008110
The European project HIALINE: Comparison between Poaceae Airborne Pollen Counts and Phl p5 Aeroallergen Quantification in SW Europe
The European project HIALINE: Comparison between Poaceae Airborne Pollen Counts and Phl p5 Aeroallergen Quantification in SW Europe
C. Antunes1*, R. Ferro1, R. Ribeiro1, Torres M.C.3, M.J. Velasco3H. García-Mozo3, Galán, C3 , R.Brandao2, M.Thibaudon4 and the HIALINE team5
1Department of Chemistry, University of Évora, Portugal
2Department of Biology, University of Évora, Portugal
3Department of Botany, Ecology and Plant Physiology, University of Córdoba
4Réseau National de l Surveillance Aerobiologique, Saint-Genis-l’Argentière, France
5J.Buters, Germanny, M. Thibaudon, France, M. Smith, Great Britain, C. Galan, Spain, R. Brandao and C.M. Antunes, Portugal, R. Albertini, Italy, L. Grewling, Poland, A. Rantio-Lehtimäki, Finland, S. Jäger and U. Berger, Austria, I. Sauliene, Lithuania, L. Cecchi, Italy
* Presenting Author:
Antunes, C. Department of Chemistry, University of Évora, Portugal.
Phone +351 266745319 ; email: [email protected]
Introduction: Nowadays, pollinosis is affecting in a large percentage of population in the developed countries. The existence of allergenic activity in the atmosphere is not only associated to pollen grains and fungal spores, but also to submicronic and paucimicronic biological particles. The origin of these allergens can be due to the rupture of pollen transported in the atmosphere or to the presence of allergens from other parts of the plant making amorphous material with allergenic load. Poaceae pollen is recognized as one of the main causes of allergic disease in all Europe. In this study we have tried to compare Poaceae pollen counts in the air and Phl p 5, one of the major allergens of this family, through the use of a high-volume cascade impactor (Chemvol). This study was done in the frame of the European project HIALINE and it compares the results obtained in 2009 by 3 different partners participating in this project: in Córdoba (Spain), Évora (Portugal) and Lyon (France).
Methodology: Pollen grains have been taken out using a 7-day volumetric Hirst type spore trap. Chemvol high-volume cascade impactor equipped with stages PM>10µm, 10 µm>PM>2.5µm were used for detecting aeroallergens. In each stage polyurethane filters were applied. Phl p5 allergen was determined using allergen specific ELISA´s. Antibodies for analysis are delivered by Allergopharma Joachim Ganzer KG, the industrial partner in this project. Both samplers were placed side-by-side.
Results: Most of the allergen was collected in the PM>10µm fraction. Similar profiles between airborne pollen and the total allergenic load was observed during the pollen season. A good correlation was obtained and a value of 2.5 pg/pollen grain of Poaceae was estimated.
Discussion: These results suggest that the allergenic load in outdoor air might be mainly due to pollen bursts. It supports the hypothesis that monitoring the allergens itself in ambient air might be an improvement in allergen exposure assessment.
This work was supported in part by the European Agency for Health and Consumers EAHC, Luxembourg, under the grant agreement 2008110
Differential activation and function of Rho GTPases during Salmonella–host cell interactions
Salmonella enterica, the cause of food poisoning and typhoid fever, has evolved sophisticated mechanisms to modulate Rho family guanosine triphosphatases (GTPases) to mediate specific cellular responses such as actin remodeling, macropinocytosis, and nuclear responses. These responses are largely the result of the activity of a set of bacterial proteins (SopE, SopE2, and SopB) that, upon delivery into host cells via a type III secretion system, activate specific Rho family GTPases either directly (SopE and SopE2) or indirectly (SopB) through the stimulation of an endogenous exchange factor. We show that different Rho family GTPases play a distinct role in Salmonella-induced cellular responses. In addition, we report that SopB stimulates cellular responses by activating SH3-containing guanine nucleotide exchange factor (SGEF), an exchange factor for RhoG, which we found plays a central role in the actin cytoskeleton remodeling stimulated by Salmonella. These results reveal a remarkable level of complexity in the manipulation of Rho family GTPases by a bacterial pathogen
Quantum time uncertainty in Schwarzschild-anti-de Sitter black holes
The combined action of gravity and quantum mechanics gives rise to a minimum
time uncertainty in the lowest order approximation of a perturbative scheme, in
which quantum effects are regarded as corrections to the classical spacetime
geometry. From the nonperturbative point of view, both gravity and quantum
mechanics are treated on equal footing in a description that already contains
all possible backreaction effects as those above in a nonlinear manner. In this
paper, the existence or not of such minimum time uncertainty is analyzed in the
context of Schwarzschild-anti-de Sitter black holes using the isolated horizon
formalism. We show that from a perturbative point of view, a nonzero time
uncertainty is generically present owing to the energy scale introduced by the
cosmological constant, while in a quantization scheme that includes
nonperturbatively the effects of that scale, an arbitrarily high time
resolution can be reached.Comment: 10 pages, version published in Physical Review
Entropy and temperature of black holes in a gravity's rainbow
The linear relation between the entropy and area of a black hole can be
derived from the Heisenberg principle, the energy-momentum dispersion relation
of special relativity, and general considerations about black holes. There
exist results in quantum gravity and related contexts suggesting the
modification of the usual dispersion relation and uncertainty principle. One of
these contexts is the gravity's rainbow formalism. We analyze the consequences
of such a modification for black hole thermodynamics from the perspective of
two distinct rainbow realizations built from doubly special relativity. One is
the proposal of Magueijo and Smolin and the other is based on a canonical
implementation of doubly special relativity put forward recently by the
authors. In these scenarios, we obtain modified expressions for the entropy and
temperature of black holes. We show that, for a family of doubly special
relativity theories satisfying certain properties, the temperature can vanish
in the limit of zero black hole mass. For the Magueijo and Smolin proposal,
this is only possible for some restricted class of models with bounded energy
and unbounded momentum. With the proposal of a canonical implementation, on the
other hand, the temperature may vanish for more general theories; in
particular, the momentum may also be bounded, with bounded or unbounded energy.
This opens new possibilities for the outcome of black hole evaporation in the
framework of a gravity's rainbow.Comment: 11 pages, 2 new references added, version accepted for publication in
Physical Review
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