Memory effect in uniformly heated granular gases

We evidence a Kovacs-like memory effect in a uniformly driven granular gas. A system of inelastic hard particles, in the low density limit, can reach a non-equilibrium steady state when properly forced. By following a certain protocol for the drive time dependence, we prepare the gas in a state where the granular temperature coincides with its long time value. The temperature subsequently does not remain constant, but exhibits a non-monotonic evolution with either a maximum or a minimum, depending on the dissipation, and on the protocol. We present a theoretical analysis of this memory effect, at Boltzmann-Fokker-Planck equation level, and show that when dissipation exceeds a threshold, the response can be coined anomalous. We find an excellent agreement between the analytical predictions and direct Monte Carlo simulations

Kovacs-like memory effect in driven granular gases

While memory effects have been reported for dense enough disordered systems such as glasses, we show here by a combination of analytical and simulation techniques that they are also intrinsic to the dynamics of dilute granular gases. By means of a certain driving protocol, we prepare the gas in a state where the granular temperature $T$ coincides with its long time limit. However, $T$ does not subsequently remain constant, but exhibits a non-monotonic evolution before reaching its non-equilibrium steady value. The corresponding so-called Kovacs hump displays a normal behavior for weak dissipation (as observed in molecular systems), but is reversed under strong dissipation, where it thus becomes anomalous.Comment: 5 pages, to appear in Physical Review Letter

Finite-time adiabatic processes: derivation and speed limit

Obtaining adiabatic processes that connect equilibrium states in a given time represents a challenge for mesoscopic systems. In this paper, we explicitly show how to build these finite-time adiabatic processes for an overdamped Brownian particle in an arbitrary potential, a system that is relevant both at the conceptual and the practical level. This is achieved by jointly engineering the time evolutions of the binding potential and the fluid temperature. Moreover, we prove that the second principle imposes a speed limit for such adiabatic transformations: there appears a minimum time to connect the initial and final states. This minimum time can be explicitly calculated for a general compression/decompression situation.Comment: Main text: 5 pages; 18 pages with appendices and references; major revision with results for a general non-linear potential and study of fluctuations added; Physical Review E in pres

Analytical solution of a one-dimensional Ising model with zero temperature dynamics

The one-dimensional Ising model with nearest neighbour interactions and the zero-temperature dynamics recently considered by Lefevre and Dean -J. Phys. A: Math. Gen. {\bf 34}, L213 (2001)- is investigated. By introducing a particle-hole description, in which the holes are associated to the domain walls of the Ising model, an analytical solution is obtained. The result for the asymptotic energy agrees with that found in the mean field approximation.Comment: 6 pages, no figures; accepted in J. Phys. A: Math. Gen. (Letter to the Editor

A negative feedback between anthropogenic ozone pollution and enhanced ocean emissions of iodine

Naturally emitted from the oceans, iodine compounds efficiently destroy atmospheric ozone and reduce its positive radiative forcing effects in the troposphere. Emissions of inorganic iodine have been experimentally shown to depend on the deposition to the oceans of tropospheric ozone, whose concentrations have significantly increased since 1850 as a result of human activities. A chemistry-climate model is used herein to quantify the current ocean emissions of inorganic iodine and assess the impact that the anthropogenic increase in tropospheric ozone has had on the natural cycle of iodine in the marine environment since pre-industrial times. Our results indicate that the human-driven enhancement of tropospheric ozone has doubled the oceanic inorganic iodine emissions following the reaction of ozone with iodide at the sea surface. The consequent build-up of atmospheric iodine, with maximum enhancements of up to 70% with respect to pre-industrial times in continental pollution outflow regions, has in turn accelerated the ozone chemical loss over the oceans with strong spatial patterns. We suggest that this ocean-atmosphere interaction represents a negative geochemical feedback loop by which current ocean emissions of iodine act as a natural buffer for ozone pollution and its radiative forcing in the global marine environment.Fil: Prados Roman, C.. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; EspañaFil: Cuevas, Carlos Alberto. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; EspañaFil: Fernandez, Rafael Pedro. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; España. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaFil: Kinnison, Douglas E.. National Center For Atmospheric Research. Amospheric Chemistry División; Estados UnidosFil: Lamarque, Jean Francoise. National Center For Atmospheric Research. Amospheric Chemistry División; Estados UnidosFil: Saiz-lopez, Alfonso. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; Españ

Estudio palinológico de la tribu Hedysareae DC. en Andalucía Occidental

Se ha estudiado a microscopía óptica y electrónica de barrido la morfología polínica de 20 especies de la tri bu Hedysareae OC., comprendidas en los géneros : Scorpiurus, Coronilla, Hippocrepis, Orni thopus, Hedysarum y Onobrychis . Todas ellas presentes en Andalucía Occ i dental . Los caracteres polinices apoYan en parte la sistemática establecida para este grupo .In this paper the pollen morphology of 20 spec i es of the tri be Hedysareae DC., present in Western Andalucia belonging to the genera : Scorpiurus , Coronilla, Hippocrepis, Ornithopus, Hedysarum and Onobrychis are studied by means of light and scanning electron rnicroscopy. Several differences of taxonomic importance supporting previous systemat ic works in this genus have been foun

Estudio palinológico de la tribu Genisteae R. BR. en Andalucía Occidental

Se ha estudiado a microscopía óptica y electr óni ca de barrido la morfología polinice de 40 especies presentes en Andalucía Occidental de la tribu Genisteae R. Br. , pertenecientes a los géne ros : Retama, Spartium, Eri nacea , Genista , Teline, Echinospartum, Chamaespartium, Ulex, Stauracanthus, Calicotome, Cytisus , Chronanthus, Adenocarpus, Argyrolobiurn y Lupinus. Los datos obtenidos parecen i ndicar que se trata de una tribu estenopalina , aunque existen algunos indi cios que pueden permitir una segregación de los génerosIn this paper the pollen morphology of 40 species of the tr-i be Genisteae R. Br . , present in Wes t ern Andalucia and belonging to t he genus : Retama, Spartium, Erinacea, Genista, Teline, Echinospartum , Chamaespartium, Ulex, Stauracanthus , Calicotome, Cytisus, Chronantus, Adenocarpus, Argyrolobium and Lupinus are studied by means of light and scanning electron microscopy. According to our observations the tri be appear t o be steno palynous al though sorne genera are separable on pollen characte

Temperature dependence of the magnetization processes in Co/Al oxide/Permalloy trilayers

The magnetization process of Co/Al oxide/Py trilayers and its evolution with the temperature have been analyzed. The particular behavior of the Co layers, including the shift of the hysteresis loops and a coercivity increase with the decrease of temperature, is related with the apparition of a CoO layer at the Co/Al-oxide interface

Diffusion-Weighted Imaging: Recent Advances and Applications

Quantitative diffusion imaging techniques enable the characterization of tissue microstructural properties of the human brain “in vivo”, and are widely used in neuroscientific and clinical contexts. In this review, we present the basic physical principles behind diffusion imaging and provide an overview of the current diffusion techniques, including standard and advanced techniques as well as their main clinical applications. Standard diffusion tensor imaging (DTI) offers sensitivity to changes in microstructure due to diseases and enables the characterization of single fiber distributions within a voxel as well as diffusion anisotropy. Nonetheless, its inability to represent complex intravoxel fiber topologies and the limited biological specificity of its metrics motivated the development of several advanced diffusion MRI techniques. For example, high-angular resolution diffusion imaging (HARDI) techniques enabled the characterization of fiber crossing areas and other complex fiber topologies in a single voxel and supported the development of higher-order signal representations aiming to decompose the diffusion MRI signal into distinct microstructure compartments. Biophysical models, often known by their acronym (e.g., CHARMED, WMTI, NODDI, DBSI, DIAMOND) contributed to capture the diffusion properties from each of such tissue compartments, enabling the computation of voxel-wise maps of axonal density and/or morphology that hold promise as clinically viable biomarkers in several neurological and neuroscientific applications; for example, to quantify tissue alterations due to disease or healthy processes. Current challenges and limitations of state-of-the-art models are discussed, including validation efforts. Finally, novel diffusion encoding approaches (e.g., b-tensor or double diffusion encoding) may increase the biological specificity of diffusion metrics towards intra-voxel diffusion heterogeneity in clinical settings, holding promise in neurological applications

Contribution to the palynological study of the species of Ononis L. (Fabaceae) from western Andalusia

The pollen grains of the species of Ononis bccurring in western Andalusia have been studied by light, scanning electrón and transmission electrón microscopy. The results show differences in the morphology of the exine and in the P/E axes ratio. Four pollen types are recognised, one comprising the majority of the Andalusian species the other three each consisting of a single species, these being O. pubescens, O. reuteri and O. speciosa.Se estudian palinológicamente las especies del género Ononis L. presentes en Andalucía occidental, mediante microscopía óptica y electrónica, de barrido y transmisión. Según nuestros resultados hay diferencias en cuanto al tipo de exina y relación de los ejes que separan claramente a O. pubescens, O. reuteri y O. speciosa del resto de las especies estudiadas