Institution
National University of La Plata
Education•La Plata, Argentina•
About: National University of La Plata is a education organization based out in La Plata, Argentina. It is known for research contribution in the topics: Population & Stars. The organization has 12993 authors who have published 30013 publications receiving 495118 citations. The organization is also known as: UNLP & Universidad Nacional de La Plata.
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TL;DR: This work proposes novel dynamical equations for the collective motion of polarized animal groups that account for correlated turning including solely social forces and derives a new model of collective motion based on a generalized coordinates of motion akin to a Hamiltonian formulation for rotations.
Abstract: Birds in a flock move in a correlated way, resulting in large polarization of velocities. A good understanding of this collective behavior exists for linear motion of the flock. Yet observing actual birds, the center of mass of the group often turns giving rise to more complicated dynamics, still keeping strong polarization of the flock. Here we propose novel dynamical equations for the collective motion of polarized animal groups that account for correlated turning including solely social forces. We exploit rotational symmetries and conservation laws of the problem to formulate a theory in terms of generalized coordinates of motion for the velocity directions akin to a Hamiltonian formulation for rotations. We explicitly derive the correspondence between this formulation and the dynamics of the individual velocities, thus obtaining a new model of collective motion. In the appropriate overdamped limit we recover the well-known Vicsek model, which dissipates rotational information and does not allow for polarized turns. Although the new model has its most vivid success in describing turning groups, its dynamics is intrinsically different from previous ones in a wide dynamical regime, while reducing to the hydrodynamic description of Toner and Tu at very large length-scales. The derived framework is therefore general and it may describe the collective motion of any strongly polarized active matter system.
98 citations
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TL;DR: In this article, the catalytic combustion of diesel soot particles was studied on Co/MgO (12 wt% Co) and potassium-promoted Co/mgO(1.5wt% K) that were calcined at different temperatures in the 300 to 700°C range.
Abstract: The catalytic combustion of diesel soot particles was studied on Co/MgO (12 wt% Co) and potassium-promoted Co/MgO (1.5 wt% K) that were calcined at different temperatures in the 300 to 700°C range. Catalyst samples were characterized by various techniques including nitrogen adsorption (BET), temperature programmed reduction (TPR),X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), electron spin resonance (ESR),X-ray photoelectron spectroscopy (XPS) and temperature programmed oxidation (TPO). As observed by TPO experiments, the catalyst activity depends strongly on the calcination temperature: calcination at 300 and 400°C produced samples that were much more active than those calcined at higher temperatures, on which an inactive Mg Co mixed oxide is formed, as suggested by TPR, ESR and XRD results. FTIR shows carbonate species on the surface. Unpromoted samples seem to correlate their activity with the amount of reducible Co species present. Potassium not only increased the sample activity, probably due to the improvement in surface mobility, but also enhanced stability at high temperatures. Experiments with different soot to catalyst ratios showed no significant variation in combustion temperature. TheK-promoted catalyst burns off soot at a temperature lower than the one needed for calcination, thus proving to be a promising catalyst.
98 citations
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TL;DR: In this paper, robust estimation in linear models of the form: y i = x 1i β 1 + x 2i β 2 +e i (i=1,…,n), in which the x 1 i are fixed 0-1 vectors and the x 2 i are continuous random variables which may contain leverage points is studied.
98 citations
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TL;DR: Different spectroscopic methods were applied to study the effects of the interaction of vanadyl and vanadate species with BSA, considered as the most abundant plasma protein.
98 citations
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TL;DR: In this article, the authors investigated the hydrodynamical properties of jet-cloud interactions and the resulting shocks, and developed a model to compute the spectral energy distribution of the emission generated by the particles accelerated in these shocks.
Abstract: Context. Dense and cold clouds seem to populate the broad line region surrounding the central black hole in AGNs. These clouds may interact with the AGN jet base which could have observational consequences.Aims. We study the gamma-ray emission produced by these jet-cloud interactions, and explore the conditions under which this radiation would be detectable.Methods. We investigate the hydrodynamical properties of jet-cloud interactions and the resulting shocks, and develop a model to compute the spectral energy distribution of the emission generated by the particles accelerated in these shocks. We discuss our model in the context of radio-loud AGNs, with applications to two representative cases, the low-luminous Centaurus A and the powerful 3C 273.Results. Some fraction of the jet power may be channelled into gamma-ray energy, which is likely to be dominated by synchrotron self-Compton radiation, and have typical variability timescales similar to the cloud lifetime within the jet, which is longer than several hours. Many clouds can interact with the jet simultaneously leading to fluxes significantly higher than in one interaction, but then variability will be smoothed out. Conclusions. Jet-cloud interactions may produce detectable gamma-rays in non-blazar AGNs that are transient in nearby low-luminous sources such as Cen A, and steady in the case of powerful objects of FR II type.
98 citations
Authors
Showing all 13198 results
Name | H-index | Papers | Citations |
---|---|---|---|
David Cameron | 154 | 1586 | 126067 |
Subir Sarkar | 149 | 1542 | 144614 |
Mayda Velasco | 137 | 1309 | 87579 |
Diego F. Torres | 137 | 948 | 72180 |
Heidi Sandaker | 128 | 999 | 76517 |
Vincent Garonne | 128 | 921 | 76980 |
Farid Ould-Saada | 128 | 931 | 76394 |
Ole Røhne | 128 | 1038 | 75752 |
Peter Hansen | 128 | 1271 | 86210 |
Maria-Teresa Dova | 127 | 778 | 73558 |
Vladimir Sulin | 127 | 884 | 75329 |
Andrei Snesarev | 127 | 875 | 74907 |
James Catmore | 127 | 892 | 75086 |
Ruslan Mashinistov | 126 | 860 | 73897 |
Fernando Monticelli | 126 | 843 | 73385 |