1,310 research outputs found

    About an H-theorem for systems with non-conservative interactions

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    We exhibit some arguments in favour of an H-theorem for a generalization of the Boltzmann equation including non-conservative interactions and a linear Fokker-Planck-like thermostatting term. Such a non-linear equation describing the evolution of the single particle probability Pi(t)P_i(t) of being in state ii at time tt, is a suitable model for granular gases and is indicated here as Boltzmann-Fokker-Planck (BFP) equation. The conjectured H-functional, which appears to be non-increasing, is HC(t)=iPi(t)lnPi(t)/ΠiH_C(t)=\sum_i P_i(t) \ln P_i(t)/\Pi_i with Πi=limtPi(t)\Pi_i = \lim_{t \to \infty} P_i(t), in analogy with the H-functional of Markov processes. The extension to continuous states is straightforward. A simple proof can be given for the elastic BFP equation. A semi-analytical proof is also offered for the BFP equation for so-called inelastic Maxwell molecules. Other evidence is obtained by solving particular BFP cases through numerical integration or through "particle schemes" such as the Direct Simulation Monte Carlo.Comment: 15 pages, 4 figures, submitte

    Noise activated granular dynamics

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    We study the behavior of two particles moving in a bistable potential, colliding inelastically with each other and driven by a stochastic heat bath. The system has the tendency to clusterize, placing the particles in the same well at low drivings, and to fill all of the available space at high temperatures. We show that the hopping over the potential barrier occurs following the Arrhenius rate, where the heat bath temperature is replaced by the granular temperature. Moreover, within the clusterized ``phase'' one encounters two different scenarios: for moderate inelasticity, the jumps from one well to the other involve one particle at a time, whereas for strong inelasticity the two particles hop simultaneously.Comment: RevTex4, 4 pages, 4 eps figures, Minor revisio

    Active escape dynamics: the effect of persistence on barrier crossing

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    We study a system of non-interacting active particles, propelled by colored noises, characterized by an activity time τ\tau, and confined by a double-well potential. A straightforward application of this system is the problem of barrier crossing of active particles, which has been studied only in the limit of small activity. When τ\tau is sufficiently large, equilibrium-like approximations break down in the barrier crossing region. In the model under investigation, it emerges a sort of "negative temperature" region, and numerical simulations confirm the presence of non-convex local velocity distributions. We propose, in the limit of large τ\tau, approximate equations for the typical trajectories which successfully predict many aspects of the numerical results. The local breakdown of detailed balance and its relation with a recent definition of non-equilibrium heat exchange is also discussed.Comment: 5 figure

    Improved time-resolved measurements of inorganic ions in particulate matter by PILS-IC integrated with a sample pre-concentration system

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    A particle-into-liquid sampler coupled with ion chromatograph (PILS-IC) for the on-line measurement of inorganic ions has been modified by the insertion of two ion-exchange pre-concentration cartridges that enrich the sample during the period of the IC analysis. The limits of detection of the modified instrument were 10-15 times lower and the time coverage 24 times higher (from 2 to 48 min per hour) than those of the original PILS-IC setup. The instrumental performance in terms of recovery and break-through volume from the cartridges was satisfactory. The modified PILS-IC was operated in comparison with a diffusion denuder line and with a high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) during a short intensive measurement period organized in the framework of the European Monitoring and Evaluation Programme (EMEP), a co-operative program for monitoring and evaluation of the long-range transmission of the air pollutants in Europe. The instrument showed a quantitative response in agreement with the results of the diffusion lines, and an ability to trace fine concentration variations not so different from the performance of the much more complex HR-TOF-AMS. From the time patterns of the ion concentrations measured by the modified PILS-IC, it was possible to obtain useful information about the variations in the air quality and in the strength of the particulate matter sourc

    The invasive species rules: competitive exclusion in forest avian mixed-species flocks in a fragmented landscape

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    Evidence of checkerboard patterns of species' distribution in avian mixed-species flocks suggest that competition is one of the forces shaping the composition and structure of these associations. However, evidence of competition among flock species comes from studies performed in well-preserved regions and no study has reported the interactions between invasive and native flocking species in human-modified landscapes. Such studies are important because evidence show that avian social systems such as mixed-species flocks suffer several negative impacts of habitat fragmentation. In this study, it is shown that an invasive woodcreeper (Lepidocolaptes angustirostris) from open areas of central and western South America is: 1) expanding its range into that of a native Atlantic Forest woodcreeper (L. squamatus)2) using the same forest fragments in which the native woodcreeper occurs3) regularly joining Atlantic Forest mixed-species flocks that contain the native woodcreeper4) overlapping in foraging height with the native woodcreeper during flockingand 5) engaging in aggressive encounters and excluding the native woodcreeper from flocks. We suggest that this aggressive behavior is a consequence of the overlap in foraging height between the invasive and native species in their original habitats and that their contact has so recently been established. This study suggests that competitive interactions mediated by aggressive behaviors of invasive species may have a negative impact on the fitness of native mixed-species flock species in a fragmented landscape.Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)Graduate Program in Ecology and Evolution from Federal University of Sao Paulo (UNIFESP-Diadema)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Biota ProgramNational Science FoundationWorld Wildlife Fund (WWF)Graduate Program of Ecology, Conservation and Wildlife Management (ECMVS) from Federal University of Minas Gerais (UFMG)CNPqPrograma Natureza e Sociedade WWF/SUNY projetoUniv Fed Sao Paulo, Dept Ecol & Biol Evolut, BR-09972270 Diadema, SP, BrazilUniv Brasilia, Inst Ciencias Biol, Dept Zool, BR-70910900 Brasilia, DF, BrazilUniv Fed Vicosa, Dept Biol Anim, Museu Zool Joao Moojen de Oliveira, BR-36570000 Vicosa, MG, BrazilUniv Fed Sao Paulo, Dept Ecol & Biol Evolut, BR-09972270 Diadema, SP, BrazilBiota Program: 2010/05445-2Biota Program: 2015/18287-0Biota Program: 2011/50143-7Biota Program: 2011/23155-4Biota Program: 2013/50297-0National Science Foundation: DOB 1343578Programa Natureza e Sociedade WWF/SUNY projeto: CSR 142-00Web of Scienc

    Políticas Públicas e Desenvolvimento Regional: a relação entre os repasses públicos e o desenvolvimento brasileiro

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    Momentos de maior fragilidade social, como o atual cenário de pandemia do Covid19 evidenciam a indispensável e necessária atuação do Estado, garantindo renda mínima e defesa dos mais vulne­ráveis, apesar disso, o cenário brasileiro dos últimos quatro anos intensificou o embate entre as forças sociais, algumas apregoando o corolário do Estado mínimo e, outras, reforçando a importância das po­líticas públicas na equalização das desigualdades. Este processo social bipolar, instiga ao objetivo de monitorar as relações de efeito no repasse de políticas públicas sobre o Produto Interno Bruto – PIB e o Índice Firjan de Desenvolvimento Munici­pal – IFDM, analisados no período de 2005-2016, a partir dos dados em painel de todos os municípios brasileiros. As políticas avaliadas explicam o PIB e o IFDM no cenário macro, mas, regionalmente, o Fundo de Participação dos Municípios e o Benefício de Prestação Continuada geram maiores efeitos na equalização da renda e bem-estar entre as regiões

    Children’s and families’ determinants of health-related behaviors in an italian primary school sample: The “seven days for my health” project

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    Childhood obesity is an established health problem, and there is a growing need for health promotion interventions focused on healthy behaviors in collaboration with parents and schools. The Mediterranean diet (MD) could help to tackle obesity, but it is essential to maintain a good level of physical activity (PA) and limit time spent in sedentary activities (ST). To explore family determinants, adherence to the MD and PA levels as potential predictors of a child’s health-related behaviors, we performed a cross-sectional analysis of 368 Italian primary school children with a mean age of 8.95 years (SD = 1.43). Data were collected from May to June 2017 using a weekly diary, an interactive tool to assess the child’s and parents’ lifestyle. The child’s degree of adherence to the MD was calculated using the KIDMED index. Adherence to the MD was high, medium and poor in 5.2%, 62.5% and 32.3% of children, respectively. Higher maternal educational level was positively associated with children’s MD and PA (p < 0.05) and negatively correlated to ST. Maternal fruit and vegetable consumption was positively related to the MD and negatively related to ST (p < 0.05). Maternal PA was positively associated with the MD (p < 0.001). Paternal PA, and fruit and vegetable consumption, were positively associated with children’s PA (p < 0.05). Our results underline the need for future studies, mainly focused on school-based and family-based interventions, to promote healthy lifestyles and nutritional habits

    Crossmodal representation of a functional robotic hand arises after extensive training in healthy participants

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    a b s t r a c t The way in which humans represent their own bodies is critical in guiding their interactions with the environment. To achieve successful body-space interactions, the body representation is strictly connected with that of the space immediately surrounding it through efficient visuo-tactile crossmodal integration. Such a body-space integrated representation is not fixed, but can be dynamically modulated by the use of external tools. Our study aims to explore the effect of using a complex tool, namely a functional prosthesis, on crossmodal visuo-tactile spatial interactions in healthy participants. By using the crossmodal visuo-tactile congruency paradigm, we found that prolonged training with a mechanical hand capable of distal hand movements and providing sensory feedback induces a pattern of interference, which is not observed after a brief training, between visual stimuli close to the prosthesis and touches on the body. These results suggest that after extensive, but not short, training the functional prosthesis acquires a visuo-tactile crossmodal representation akin to real limbs. This finding adds to previous evidence for the embodiment of functional prostheses in amputees, and shows that their use may also improve the crossmodal combination of somatosensory feedback delivered by the prosthesis with visual stimuli in the space around it, thus effectively augmenting the patients' visuomotor abilities

    A registry for Dravet syndrome: The Italian experience

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    Objectives: We describe the Residras registry, dedicated to Dravet syndrome (DS) and to other phenotypes related to SCN1A mutations, as a paradigm of registry for rare and complex epilepsies. Our primary objectives are to present the tools and framework of the integrative platform, the main characteristics emerging from the patient cohort included in the registry, with emphasis on demographic, clinical outcome, and mortality. / Methods: Standardized data of enrolled pediatric and adult patients were collected in 24 Italian expert centers and regularly updated at least on a yearly basis. Patients were prospectively enrolled, at registry starting, but historical retrospective data were also included. / Results: At present, 281 individuals with DS and a confirmed SCN1A mutation are included. Most patients have data available on epilepsy (n = 263) and their overall neurological condition (n = 255), based on at least one follow-up update. Median age at first clinical assessment was 2 years (IQR 0–9) while at last follow-up was 11 years (IQR 5–18.5). During the 7-year activity of the registry, five patients died resulting in a mortality rate of 1.84 per 1000-person-years. When analyzing clinical changes over the first 5-year follow-up, we observed a significant difference in cognitive function (P < 0.001), an increased prevalence of behavioral disorders including attention deficit (P < 0.001), a significant worsening of language (P = 0.001), and intellectual disability (P < 0.001). / Significance: The Residras registry represents a large collection of standardized national data for the DS population. The registry platform relies on a shareable and interoperable framework, which promotes multicenter high-quality data collection. In the future, such integrated platform may represent an invaluable asset for easing access to cohorts of patients that may benefit from clinical trials with emerging novel therapies, for drug safety monitoring, and for delineating natural history. Its framework makes it improvable based on growing experience with its use and easily adaptable to other rare and complex epilepsy syndromes
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