Universal relaxation function in nonextensive systems

We have derived the dipolar relaxation function for a cluster model whose volume distribution was obtained from the generalized maximum Tsallis nonextensive entropy principle. The power law exponents of the relaxation function are simply related to a global fractal parameter $\alpha$ and for large time to the entropy nonextensivity parameter $q$. For intermediate times the relaxation follows a stretched exponential behavior. The asymptotic power law behaviors both in the time and the frequency domains coincide with those of the Weron generalized dielectric function derived from an extension of the Levy central limit theorem. They are in full agreement with the Jonscher universality principle. Moreover our model gives a physical interpretation of the mathematical parameters of the Weron stochastic theory and opens new paths to understand the ubiquity of self-similarity and power laws in the relaxation of large classes of materials in terms of their fractal and nonextensive properties.Comment: Two figures. Submitted for publicatio

Boron content of Lake Ulubat sediment: A key to interpret the morphological history of NW Anatolia, Turkey

Freshwater Lake Ulubat (c. 1.5 m deep and c. 138 km2) receives sediment from a 10.414 km2 area in the seismically active Susurluk Drainage Basin (SDB) of NW Turkey. The B and trace element contents of the lake infill seem to be a link between the fresh landforms of the SDB and the lacustrine sediment. Deposition in Lake Ulubat has been 1.60 cm.a-1 for the last 50 a according to radionucleides; however the sedimentation rate over the last millennium was 0.37 cm.a-1 based on 14C dating. The B content of the lacustrine infill displays a slight increase at 0.50 m and a drastic increase at 4 m depth occurring c. 31 a and c. 1070 a ago respectively. Probably the topmost change corresponds to the start of open mining in the SDB and the second one to the natural trenching of borate ore-deposits. These dates also show indirectly a 1.4 cm.a-1 erosion rate during the last millennium as the borate beds were trenched up to 15 m. By extrapolation, it is possible to establish that the formation of some of the present morphological features of the southern Marmara region, especially river incision, began in the late Pleistocene, and developed especially over the last 75 ka

Revolving rivers in sandpiles: from continuous to intermittent flows

In a previous paper [Phys. Rev. Lett. 91, 014501 (2003)], the mechanism of "revolving rivers" for sandpile formation is reported: as a steady stream of dry sand is poured onto a horizontal surface, a pile forms which has a river of sand on one side owing from the apex of the pile to the edge of the base. For small piles the river is steady, or continuous. For larger piles, it becomes intermittent. In this paper we establish experimentally the "dynamical phase diagram" of the continuous and intermittent regimes, and give further details of the piles topography, improving the previous kinematic model to describe it and shedding further light on the mechanisms of river formation. Based on experiments in Hele-Shaw cells, we also propose that a simple dimensionality reduction argument can explain the transition between the continuous and intermittent dynamics.Comment: 8 pages, 11 figures, submitted to Phys Rev

Electromagnetic and Gravitational Invariants

The curvature invariants have been subject of recent interest in the context of the experimental detection of the gravitomagnetic field, namely due to the debate concerning the notions of "extrinsic" and "intrinsic" gravitomagnetism. In this work we explore the physical meaning of the curvature invariants, dissecting their relationship with the gravitomagnetic effects

Non-collinear coupling between magnetic adatoms in carbon nanotubes

The long range character of the exchange coupling between localized magnetic moments indirectly mediated by the conduction electrons of metallic hosts often plays a significant role in determining the magnetic order of low-dimensional structures. In addition to this indirect coupling, here we show that the direct exchange interaction that arises when the moments are not too far apart may induce a non-collinear magnetic order that cannot be characterized by a Heisenberg-like interaction between the magnetic moments. We argue that this effect can be manipulated to control the magnetization alignment of magnetic dimers adsorbed to the walls of carbon nanotubes.Comment: 13 pages, 5 figures, submitted to PR

Electromagnetic and Gravitational Invariants

The curvature invariants have been subject of recent interest in the context of the experimental detection of the gravitomagnetic field, namely due to the debate concerning the notions of "extrinsic" and "intrinsic" gravitomagnetism. In this work we explore the physical meaning of the curvature invariants, dissecting their relationship with the gravitomagnetic effects

Electromagnetic and Gravitational Invariants

The curvature invariants have been subject of recent interest in the context of the experimental detection of the gravitomagnetic field, namely due to the debate concerning the notions of "extrinsic" and "intrinsic" gravitomagnetism. In this work we explore the physical meaning of the curvature invariants, dissecting their relationship with the gravitomagnetic effects

Sustentabilidade e inovação tecnológica em sistemas produtivos familiares integrados com palma de óleo no Estado do Pará.

Objetivou-se analisar os aspectos organizacionais, econômicos, ambientais e tecnológicos em sistemas produtivos familiares integrados com palma de óleo no Estado do Pará. Os levantamentos de dados foram através de entrevistas semi estruturadas para o público de agricultores familiares fornecedores de cacho de fruto fresco (CFF) para agroindústrias de óleo de palma nos municípios de Moju, Tailândia, Acará e São Domingos do Capim. Nesse sentido foram identificados que os aspectos renda e uso de tecnologias produtivas são favoráveis para este segmento da agricultura familiar nesta parte da Amazônia