1,328 research outputs found
Collective motion of self-propelled particles interacting without cohesion
We present a comprehensive study of Vicsek-style self-propelled particle
models in two and three space dimensions. The onset of collective motion in
such stochastic models with only local alignment interactions is studied in
detail and shown to be discontinuous (first-order like). The properties of the
ordered, collectively moving phase are investigated. In a large domain of
parameter space including the transition region, well-defined high-density and
high-order propagating solitary structures are shown to dominate the dynamics.
Far enough from the transition region, on the other hand, these objects are not
present. A statistically-homogeneous ordered phase is then observed, which is
characterized by anomalously-strong density fluctuations, superdiffusion, and
strong intermittency.Comment: Submitted to Physical Review
Permafrost - physical aspects and carbon cycling, databases and uncertainties
Permafrost is defined as ground that remains below 0°C for at least 2 consecutive years. About 24% of the northern hemisphere land area is underlain by permafrost. The thawing of permafrost has the potential to influence the climate system through the release of carbon (C) from northern high latitude terrestrial ecosystems, but there is substantial uncertainty about the sensitivity of the C cycle to thawing permafrost. Soil C can be mobilized from permafrost in response to changes in air temperature, directional changes in water balance, fire, thermokarst, and flooding. Observation networks need to be implemented to understand responses of
permafrost and C at a range of temporal and spatial scales. The understanding gained from these observation networks needs to be integrated into modeling frameworks capable of representing how the responses of permafrost C will influence the trajectory of climate in the future
Development of an antibody fragment that stabilizes GPCR/G-protein complexes.
Single-particle cryo-electron microscopy (cryo-EM) has recently enabled high-resolution structure determination of numerous biological macromolecular complexes. Despite this progress, the application of high-resolution cryo-EM to G protein coupled receptors (GPCRs) in complex with heterotrimeric G proteins remains challenging, owning to both the relative small size and the limited stability of these assemblies. Here we describe the development of antibody fragments that bind and stabilize GPCR-G protein complexes for the application of high-resolution cryo-EM. One antibody in particular, mAb16, stabilizes GPCR/G-protein complexes by recognizing an interface between Gα and GÎČÎł subunits in the heterotrimer, and confers resistance to GTPÎłS-triggered dissociation. The unique recognition mode of this antibody makes it possible to transfer its binding and stabilizing effect to other G-protein subtypes through minimal protein engineering. This antibody fragment is thus a broadly applicable tool for structural studies of GPCR/G-protein complexes
Electric control of collective atomic coherence in an Erbium doped solid
We demonstrate fast and accurate control of the evolution of collective
atomic coherences in an Erbium doped solid using external electric fields. This
is achieved by controlling the inhomogeneous broadening of Erbium ions emitting
at 1536 nm using an electric field gradient and the linear Stark effect. The
manipulation of atomic coherence is characterized with the collective
spontaneous emission (optical free induction decay) emitted by the sample after
an optical excitation, which does not require any previous preparation of the
atoms. We show that controlled dephasing and rephasing of the atoms by the
electric field result in collapses and revivals of the optical free induction
decay. Our results show that the use of external electric fields does not
introduce any substantial additional decoherence and enables the manipulation
of collective atomic coherence with a very high degree of precision on the time
scale of tens of ns. This provides an interesting resource for photonic quantum
state storage and quantum state manipulation.Comment: 10 pages, 5 figure
General framework of the non-perturbative renormalization group for non-equilibrium steady states
This paper is devoted to presenting in detail the non-perturbative
renormalization group (NPRG) formalism to investigate out-of-equilibrium
systems and critical dynamics in statistical physics. The general NPRG
framework for studying non-equilibrium steady states in stochastic models is
expounded and fundamental technicalities are stressed, mainly regarding the
role of causality and of Ito's discretization. We analyze the consequences of
Ito's prescription in the NPRG framework and eventually provide an adequate
regularization to encode them automatically. Besides, we show how to build a
supersymmetric NPRG formalism with emphasis on time-reversal symmetric
problems, whose supersymmetric structure allows for a particularly simple
implementation of NPRG in which causality issues are transparent. We illustrate
the two approaches on the example of Model A within the derivative expansion
approximation at order two, and check that they yield identical results.Comment: 28 pages, 1 figure, minor corrections prior to publicatio
Diversite et Abondance Relative des Oiseaux dâEau du Parc National de la Comoe, Cote dâIvoire
Les oiseaux dâeau constituent une des composantes remarquables de la faune aquatique. Cependant, elle est mal connue dans le nord du pays tout comme, au PNC qui hĂ©berge pourtant de nombreuses espĂšces dâoiseaux. Ce prĂ©sent travail a pour but dâapporter pour la premiĂšre fois des donnĂ©es aussi bien qualitatives que quantitatives sur les oiseaux dâeau du PNC en vue dâamĂ©liorer les connaissances sur cette catĂ©gorie de lâavifaune pour une meilleure gestion de ces oiseaux. Un inventaire ornithologique Ă©tĂ© menĂ© de septembre 2017 Ă aoĂ»t 2019 au parc national de la ComoĂ© sur les oiseaux dâeau dans trois diffĂ©rents types dâhabitats (les mares, le fleuve ComoĂ© et les savanes). Pour sa rĂ©alisation, la mĂ©thode des points dâĂ©coute et des marches lentes marquĂ©es dâarrĂȘts le long de la ComoĂ© et de ces principaux affluents ont Ă©tĂ© prĂ©fĂ©rĂ©es. Ă lâissu de nos inventaires 47 espĂšces dâoiseaux dâeau appartenant Ă 18 familles ont Ă©tĂ© inventoriĂ©es. Les non-passĂ©riformes avec 42 espĂšces reprĂ©sentent 89,36% de la richesse spĂ©cifique. Au niveau des familles, celle des Ardeidae reprĂ©sente 23,81% de la richesse spĂ©cifique totale avec 10 espĂšces. Au titre des abondances 2660 individus ont Ă©tĂ© observĂ©s sur lâensemble de nos sites. Le HĂ©ron garde-bĆuf Bubulcus ibis (570 individus, 21,43%) et lâOmbrette africaine Scopus umbretta (193individus, 07,26%) sont les espĂšces comptant les plus grands effectifs des oiseaux dâeau. Les espĂšces d'oiseaux d'eau ont plus frĂ©quentĂ©s le parc entre octobre et avril et les abondances les plus importantes se situent entre dĂ©cembre et mars. Seule la Cigogne Ă©piscopale Ciconia episcopus est considĂ©rĂ©e comme vulnĂ©rable selon lâUICN (2022).
Waterbirds are a remarkable component of the aquatic fauna. However, it is poorly known in the north of Ivory Coast, as well as in the Comoé National Park, which is home to many bird species. The aim of this study is to provide for the first time qualitative and quantitative data on waterbirds in the Comoé National Park in order to improve knowledge of this category of avifauna for a better management of these birds. An ornithological inventory was conducted from September 2017 to August 2019 in the Comoé National Park on waterbirds in three different types of habitats (ponds, the Comoé River and savannahs). The method of count points and slow walks with stops along the Comoé River and its main tributaries were preferred. At the end of our surveys 47 species of waterbirds belonging to 18 families were inventoried. The non-passeriformes with 42 species represent 89.36% of the species richness. In terms of families, the Ardeidae family represents 23.81% of the total species richness with 10 species. In terms of abundance, 2660 individuals were observed on all our sites. The Cattle Egret Bubulcus ibis (570 individuals, 21.43%) and the Hamerkop Scopus umbretta (193 individuals, 07.26%) are the species with the highest numbers of waterbirds. Waterbird species visited the park most between October and April, with the highest abundances between December and March. Only the Woolly-Necked stork Ciconia episcopus is considered near threatened according to the IUCN (2022)
DiversitĂ© et Abondance Relative des Oiseaux dâEau du Parc National de la ComoĂ©, CĂŽte dâIvoire
Les oiseaux dâeau constituent une des composantes remarquables de la faune aquatique. Cependant, les oiseaux dâeau du nord de la CĂŽte dâIvoire et en particulier ceux du Parc National de la ComoĂ© sont mĂ©connus. Lâobjectif de ce travail est dâamĂ©liorer les connaissances de cette avifaune pour une meilleure gestion de ces espĂšces. Ces amĂ©liorations reposent sur des donnĂ©es qualitatives et quantitatives. Un inventaire ornithologique a Ă©tĂ© menĂ© de septembre 2017 Ă aoĂ»t 2019 au Parc national de la ComoĂ© sur les oiseaux dâeau dans trois diffĂ©rents types dâhabitats (les mares, les forĂȘts galeries et les savanes). Pour sa rĂ©alisation, la mĂ©thode des points dâĂ©coute et des marches lentes marquĂ©es dâarrĂȘts le long de la ComoĂ© et de ces principaux affluents ont Ă©tĂ© appliquĂ©es. Ă lâissu de ces inventaires, 47 espĂšces dâoiseaux dâeau appartenant Ă 18 familles ont Ă©tĂ© inventoriĂ©es. Les non-PassĂ©riformes avec 42 espĂšces reprĂ©sentent 89,36% de la richesse spĂ©cifique. Au niveau des familles, celle des Ardeidae reprĂ©sente 23,81% de la richesse spĂ©cifique totale avec 10 espĂšces. Ce sont 2685 individus qui ont Ă©tĂ© observĂ©s sur lâensemble de des sites. Le HĂ©ron garde-bĆuf Bubulcus ibis (570 individus, 21,23%) et lâOmbrette africaine Scopus umbretta (193 individus, 07,19%) sont les espĂšces comptant les plus grands effectifs des oiseaux dâeau. Les espĂšces d'oiseaux d'eau ont plus frĂ©quentĂ© le parc en saison sĂšche (octobre et avril) et les abondances les plus importantes se situent entre dĂ©cembre et mars. Au titre de lâutilisation des habitats par les oiseaux dâeau, il sâobserve une prĂ©fĂ©rence de ces derniers pour les forĂȘts galeries. Seule la Cigogne Ă©piscopale Ciconia episcopus est considĂ©rĂ©e comme proche de la menace selon lâUICN (2022).
Waterbirds are a remarkable component of aquatic fauna. However, little is known about the waterbirds of northern CÎte d'Ivoire, and in particular those of the Comoé National Park. The aim of this work is to improve knowledge of this avifauna in order to improve the management of these species. These improvements are based on qualitative and quantitative data. An ornithological survey was carried out from September 2017 to August 2019 in the Comoé National Park on waterbirds in three different types of habitats (ponds, gallery forests, and savannahs). The method used was count points and slow walks with stops along the Comoé and its main tributaries. As a result of these surveys, 47 species of waterbirds belonging to 18 families were inventoried. The non-Passeriformes, with 42 species, accounted for 89.36% of the species richness. In terms of families, the Ardeidae family represented 23.81% of the total species richness, with 10 species. A total of 2,685 individuals were observed at all the sites. The Cattle Egret Bubulcus ibis (570 individuals, 21.23%) and the Hamerkop Scopus umbretta (193 individuals, 07.19%) were the species with the highest numbers of waterbirds. Waterbird species visited the park most during the dry season (October and April), with the greatest abundance between December and March. In terms of habitat use by waterbirds, there is a preference for gallery forests. Only the Woolly-Necked stork Ciconia episcopus is considered to be close to threatened according to the IUCN (2022)
Diversite et Abondance Relative des Oiseaux dâEau du Parc National de la Comoe, Cote dâIvoire
Les oiseaux dâeau constituent une des composantes remarquables de la faune aquatique. Cependant, elle est mal connue dans le nord du pays tout comme, au PNC qui hĂ©berge pourtant de nombreuses espĂšces dâoiseaux. Ce prĂ©sent travail a pour but dâapporter pour la premiĂšre fois des donnĂ©es aussi bien qualitatives que quantitatives sur les oiseaux dâeau du PNC en vue dâamĂ©liorer les connaissances sur cette catĂ©gorie de lâavifaune pour une meilleure gestion de ces oiseaux. Un inventaire ornithologique Ă©tĂ© menĂ© de septembre 2017 Ă aoĂ»t 2019 au parc national de la ComoĂ© sur les oiseaux dâeau dans trois diffĂ©rents types dâhabitats (les mares, le fleuve ComoĂ© et les savanes). Pour sa rĂ©alisation, la mĂ©thode des points dâĂ©coute et des marches lentes marquĂ©es dâarrĂȘts le long de la ComoĂ© et de ces principaux affluents ont Ă©tĂ© prĂ©fĂ©rĂ©es. Ă lâissu de nos inventaires 47 espĂšces dâoiseaux dâeau appartenant Ă 18 familles ont Ă©tĂ© inventoriĂ©es. Les non-passĂ©riformes avec 42 espĂšces reprĂ©sentent 89,36% de la richesse spĂ©cifique. Au niveau des familles, celle des Ardeidae reprĂ©sente 23,81% de la richesse spĂ©cifique totale avec 10 espĂšces. Au titre des abondances 2660 individus ont Ă©tĂ© observĂ©s sur lâensemble de nos sites. Le HĂ©ron garde-bĆuf Bubulcus ibis (570 individus, 21,43%) et lâOmbrette africaine Scopus umbretta (193individus, 07,26%) sont les espĂšces comptant les plus grands effectifs des oiseaux dâeau. Les espĂšces d'oiseaux d'eau ont plus frĂ©quentĂ©s le parc entre octobre et avril et les abondances les plus importantes se situent entre dĂ©cembre et mars. Seule la Cigogne Ă©piscopale Ciconia episcopus est considĂ©rĂ©e comme vulnĂ©rable selon lâUICN (2022).
Waterbirds are a remarkable component of the aquatic fauna. However, it is poorly known in the north of Ivory Coast, as well as in the Comoé National Park, which is home to many bird species. The aim of this study is to provide for the first time qualitative and quantitative data on waterbirds in the Comoé National Park in order to improve knowledge of this category of avifauna for a better management of these birds. An ornithological inventory was conducted from September 2017 to August 2019 in the Comoé National Park on waterbirds in three different types of habitats (ponds, the Comoé River and savannahs). The method of count points and slow walks with stops along the Comoé River and its main tributaries were preferred. At the end of our surveys 47 species of waterbirds belonging to 18 families were inventoried. The non-passeriformes with 42 species represent 89.36% of the species richness. In terms of families, the Ardeidae family represents 23.81% of the total species richness with 10 species. In terms of abundance, 2660 individuals were observed on all our sites. The Cattle Egret Bubulcus ibis (570 individuals, 21.43%) and the Hamerkop Scopus umbretta (193 individuals, 07.26%) are the species with the highest numbers of waterbirds. Waterbird species visited the park most between October and April, with the highest abundances between December and March. Only the Woolly-Necked stork Ciconia episcopus is considered near threatened according to the IUCN (2022)
- âŠ