Hamiltonian structure for dispersive and dissipative dynamical systems

We develop a Hamiltonian theory of a time dispersive and dissipative inhomogeneous medium, as described by a linear response equation respecting causality and power dissipation. The proposed Hamiltonian couples the given system to auxiliary fields, in the universal form of a so-called canonical heat bath. After integrating out the heat bath the original dissipative evolution is exactly reproduced. Furthermore, we show that the dynamics associated to a minimal Hamiltonian are essentially unique, up to a natural class of isomorphisms. Using this formalism, we obtain closed form expressions for the energy density, energy flux, momentum density, and stress tensor involving the auxiliary fields, from which we derive an approximate, ``Brillouin-type,'' formula for the time averaged energy density and stress tensor associated to an almost mono-chromatic wave.Comment: 68 pages, 1 figure; introduction revised, typos correcte

EVIDENCE OF HIGH CONSUMPTION OF WASTE BY THE ANDEAN CONDOR (VULTUR GRYPHUS) IN AN ANTHROPIZED ENVIRONMENT OF CHILE

Abstract · Anthropogenic food subsidies and waste disposals have become a new food resource for wildlife, including the Andean Condor (Vultur gryphus), a situation that implies benefits and health risks. To increase understanding of Andean Condor feeding habits in the most anthropized area in Chile, we analyzed 280 pellets collected during 2016 from one roost in the Metropolitan Region, central Chile. We identified the main diagnostic elements microscopically and expressed them as percentage of occurrence (percentage of each item in relation to all pellets). We found 12 prey categories (including mammals, birds, and plant material) and 9 waste categories. Condors fed mainly on mammals (99%); livestock was their main feeding source (52%), followed by native (22%) and exotic wild species (19%). Birds were detected less frequently (8%). We found a high occurrence of waste (31%), of which plastic remains were the main item (27%). According to our results, landfills serve as a complementary food source for condors, probably a low-quality but easily accessible, and which exposes them to a variety of health and mortality risks. Despite the fact that Andean Condors can reach distant places in foraging flights to find food resources, a high proportion of the population is attracted to rubbish dumps and landfills. Despite the spatio-temporal limitations of our results, this is the first record that describes and quantifies a high presence of waste as a component of the Andean Condor diet. We recommend a more comprehensive study to assess their feeding habits and habitat preferences in a broader spatio-temporal context, and to determine the possible impact of the use of waste disposals on Andean Condor populations.Resumen · Evidencia de alto consumo de basura por el Cóndor Andino (Vultur gryphus) en un ambiente antropizado de Chile Los subsidios antropogénicos y sitios de disposición de basura se han convertido en una nueva fuente de alimentación para la fauna, incluido el Cóndor Andino (Vultur gryphus), lo que implica beneficios y riesgos. Con el fin de estudiar los hábitos alimenticios del cóndor andino en un área altamente antropizada, analizamos 280 egagrópilas colectadas durante 2016 en un dormidero de la Región Metropolitana, en Chile central. Identificamos microscópicamente los principales elementos diagnósticos y los expresamos como porcentaje de ocurrencia (porcentaje de cada ítem respecto del total de pellet). Encontramos 12 ítems dietarios (incluyendo mamíferos, aves y materia vegetal) y 9 ítems de basura. Los cóndores se alimentaron principalmente de mamíferos (99%); el ganado fue la principal fuente de alimento (52%), seguido por especies silvestres nativas (22%) y exóticas (19%), mientras que las aves estuvieron escasamente representadas (8%). Encontramos una alta ocurrencia de basura (31%), de la cual los restos de plástico fueron el principal ítem (27%). De acuerdo a nuestros resultados, los basurales sirven como una fuente complementaria de alimentación para los cóndores, probablemente de baja calidad, pero de fácil acceso, y que los expone a una variedad de riesgos de mortalidad y para su salud. Aunque el Cóndor Andino puede alcanzar lugares distantes en sus vuelos de forrajeo, una alta proporción de su población es atraída a vertederos y rellenos sanitarios. A pesar de las limitaciones espaciotemporales de nuestros resultados, este es el primer registro que describe y cuantifica la alta presencia de basura como componente de la dieta del Cóndor Andino. Recomendamos ampliar el estudio para evaluar sus hábitos alimentarios y preferencias de hábitat en un contexto espacial y temporal amplio y poder determinar el posible impacto del uso de basurales en poblaciones de Cóndor Andino

Exactly solvable model of quantum diffusion

We study the transport property of diffusion in a finite translationally invariant quantum subsystem described by a tight-binding Hamiltonian with a single energy band and interacting with its environment by a coupling in terms of correlation functions which are delta-correlated in space and time. For weak coupling, the time evolution of the subsystem density matrix is ruled by a quantum master equation of Lindblad type. Thanks to the invariance under spatial translations, we can apply the Bloch theorem to the subsystem density matrix and exactly diagonalize the time evolution superoperator to obtain the complete spectrum of its eigenvalues, which fully describe the relaxation to equilibrium. Above a critical coupling which is inversely proportional to the size of the subsystem, the spectrum at given wavenumber contains an isolated eigenvalue describing diffusion. The other eigenvalues rule the decay of the populations and quantum coherences with decay rates which are proportional to the intensity of the environmental noise. On the other hand, an analytical expression is obtained for the dispersion relation of diffusion. The diffusion coefficient is proportional to the square of the width of the energy band and inversely proportional to the intensity of the environmental noise because diffusion results from the perturbation of quantum tunneling by the environmental fluctuations in this model. Diffusion disappears below the critical coupling.Comment: Submitted to J. Stat. Phy

Spectroscopic properties and radiation damage investigation of a diamond based Schottky diode for ion-beam therapy microdosimetry

In this work, a detailed analysis of the properties of a novel microdosimeter based on a synthetic single crystal diamond is reported. Focused ion microbeams were used to investigate the device spectropscopic properties as well as the induced radiation damageeffects. A diamond based Schottky diode was fabricated by chemical vapor deposition with a very thin detecting region, about 400 nm thick (approximately 1.4 μm water equivalent thickness), corresponding to the typical size in microdosimetric measurements. A 200 × 200 μm2 square metallic contact was patterned on the diamond surface by standard photolithography to define the sensitive area. Experimental measurements were carried out at the Ruder Boškovic′ Institute microbeam facility using 4 MeV carbon and 5 MeV silicon ions. Ion beam induced charge maps were employed to characterize the microdosimeter response in terms of its charge collection properties. A stable response with no evidence of polarization or memory effects was observed up to the maximum investigated ion beam flux of about 1.7 × 109 ions·cm−2·s−1. A homogeneity of the response about 6% was found over the sensitive region with a well-defined confinement of the response within the active area. Tests of the radiation damageeffect were performed by selectively irradiating small areas of the device with different ion fluences, up to about 1012 ions/cm2. An exponential decrease of the charge collection efficiency was observed with a characteristic decay constant of about 4.8 MGy and 1 MGy for C and Si ions, respectively. The experimental data were analyzed by means of GEANT4 Monte Carlo simulations. A direct correlation between the diamond damaging effect and the Non Ionizing Energy Loss (NIEL) fraction was found. In particular, an exponential decay of the charge collection efficiency with an exponential decay as a function of NIEL is observed, with a characteristic constant of about 9.3 kGy-NIEL for both carbon and silicon ions

Normal transport properties for a classical particle coupled to a non-Ohmic bath

We study the Hamiltonian motion of an ensemble of unconfined classical particles driven by an external field F through a translationally-invariant, thermal array of monochromatic Einstein oscillators. The system does not sustain a stationary state, because the oscillators cannot effectively absorb the energy of high speed particles. We nonetheless show that the system has at all positive temperatures a well-defined low-field mobility over macroscopic time scales of order exp(-c/F). The mobility is independent of F at low fields, and related to the zero-field diffusion constant D through the Einstein relation. The system therefore exhibits normal transport even though the bath obviously has a discrete frequency spectrum (it is simply monochromatic) and is therefore highly non-Ohmic. Such features are usually associated with anomalous transport properties

Effects of a nine-month physical activity intervention on morphological characteristics and motor and cognitive skills of preschool children

(1) Background: Regular physical activity (PA) plays an important role during early childhood physical and psychological development. This study investigates the effects of a 9-month PA intervention on physiological characteristics and motor and cognitive skills in preschool children. (2) Methods: Preschool children (n = 132; age 4 to 7 years) attending regular preschool programs were nonrandomly assigned to PA intervention (n = 66; 60 min sessions twice per week) or a control group (n = 66; no additional organized PA program) for 9 months. Exercise training for the intervention group included various sports games, outdoor activities, martial arts, yoga, and dance. Anthropometry, motor skills (7 tests), and cognitive skills (Raven’s Colored Progressive Matrices and Cognitive Assessment System) were assessed before and after an intervention period in both groups. Data were analyzed using repeated-measures ANOVA. (3) Results: Body weight significantly increased in both groups over time. Compared to the changes observed in the control group, the intervention group significantly increased in chest circumference (p = 0.022). In contrast, the control group demonstrated an increase in waist circumference (p = 0.001), while these measures in the intervention group remained stable. Participants in the intervention group improved running speed (p = 0.016) and standing broad jump (p = 0.000). The flexibility level was maintained in the intervention group, while a significant decrease was observed in the control group (p = 0.010). Children from the intervention group demonstrated progress in the bent-arm hang test (p = 0.001), unlike the control group subjects. Varied improvements in cognitive skills were observed for different variables in both intervention and control groups, with no robust evidence for PA-intervention-related improvements. (4) Conclusions: Preschool children’s participation in a preschool PA intervention improves their motor skills

Labour Market and Social Policy in Italy: Challenges and Changes. Bertelsmann Policy Brief #2016/02

vEight years after the outbreak of the financial crisis, Italy has still to cope with and overcome a plethora of economic and social challenges. On top of this, it faces an unfavourable demographic structure and severe disparities between its northern and southern regions. Some promising reforms have recently been enacted, specifically targeting poverty and social exclusion. However, much more remains to be done on the way towards greater economic stability and widely shared prosperity