On statistical properties of traded volume in financial markets

In this article we study the dependence degree of the traded volume of the Dow Jones 30 constituent equities by using a nonextensive generalised form of the Kullback-Leibler information measure. Our results show a slow decay of the dependence degree as a function of the lag. This feature is compatible with the existence of non-linearities in this type time series. In addition, we introduce a dynamical mechanism whose associated stationary probability density function (PDF) presents a good agreement with the empirical results.Comment: 6 pages, 4 figures, 1 table. Based on the talk presented at "News, Expectations and Trends in Statistical Physics, NEXT-SigmaPhi 3rd International Conference. 13-18 August 2005, Kolymbari CRETE" Multi-fractal analysis section remove

Continuous and discontinuous absorbing-state phase transitions on Voronoi-Delaunay random lattices

We study absorbing-state phase transitions in two-dimensional Voronoi-Delaunay (VD) random lattices with quenched coordination disorder. Quenched randomness usually changes the criticality and destroys discontinuous transitions in low-dimensional nonequilibrium systems. We performed extensive simulations of the Ziff-Gulari-Barshad (ZGB) model, and verified that the VD disorder does not change the nature of its discontinuous transition. Our results corroborate recent findings of Barghatti and Vojta [Phys. Rev. Lett. {\bf 113}, 120602 (2014)] stating the irrelevance of topological disorder in a class of random lattices that includes VD and raise the interesting possibility that disorder in nonequilibrium APT may, under certain conditions, be irrelevant for the phase coexistence. We also verify that the VD disorder is irrelevant for the critical behavior of models belonging to the directed percolation and Manna universality classes.Comment: 7 pages, 6 figure

First steps of a nucleation theory in disordered systems

We devise a field theoretical formalism for a microscopic theory of nucleation processes and phase coexistence in finite dimensional glassy systems. We study disordered $p$-spin models with large but finite range of interaction. We work in the framework of glassy effective potential theory which in mean-field is a non-convex, two minima function of the overlap. We will associate metastability and phase coexistence with the existence of space inhomogeneous solution of suitable field equations and we will study the simplest of such solutions.Comment: 31 pages, 4 figures. Content revised, typos correcte

Incidental capture of loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) sea turtles by the pelagic longline fishery off southern Brazil

Incidental capture in fishing gear is one of the main sources of injury and mortality of juvenile and adult sea turtles (NRC, 1990; Lutcavage et al., 1997; Oravetz, 1999). Six out of the seven extant species of sea turtles — the leatherback (Dermochelys coriacea), the green turtle (Chelonia mydas), the loggerhead (Caretta caretta), the hawksbill (Eretmochelys imbricata), the olive ridley (Lepidochelys olivacea), and the Kemp’s ridley (Lepidochelys kempii) — are currently classified as endangered or critically endangered by the World Conservation Union (IUCN, formerly the International Union for Conservation of Nature and Natural Resources), which makes the assessment and reduction of incidental capture and mortality of these species in fisheries priority conservation issues (IUCN/Species Survival Commission, 1995)

On the physical interpretation of effective actions using Schwinger's formula

We show explicitly that Schwinger's formula for one-loop effective actions corresponds to the summation of energies associated with the zero-point oscillations of the fields. We begin with a formal proof, and after that we confirm it using a regularization prescription.Comment: 5 p., REVTEX, IF-UFRJ-9

Fatty Acid Composition and Oxidative Stress Parameters in Plasma after Fish Oil Supplementation in Aging

Fish oil affects oxidative stress parameters and changes in phospholipids fatty acids profiles in plasma, erythrocytes and tissues. We examined the effects of fish oil supplementation in young and old male Wistar rats (3 and 22 months old) on plasma phospholipids fatty acids profiles and blood oxidative stress parameters. Twenty young and twenty aged Wistar rats were randomly divided into four groups (ten animals each): two control groups and two supplemented groups treated for 6 weeks with fish oil capsules containing 45 mg eicosapentanoic acid (EPA) and 30 mg docosahexanoic acid (DHA). Fish oil supplementation changed the percentage of long chain fatty acids (FAs): the elevated percentage of eicosatrienoic acid (ETA, 20:3), eicosapentanoic (EPA, 20:5), docosapentanoic acid (DPA, 22:5), n-3 fatty acids and decreased arachidonic acid (AA, 20:4). However, there were no age-related changes in total SH groups, the percentages of palmitic (16:0), palmitoleic (16:1), oleic (18:1 (n-9)) and linoleic acid (18:2) in plasma phospholipids and MUFA and they were neither reversed nor prevented by fish oil supplementation. Results showed that fish oil supplementation increased SOD and CAT activities in erythrocytes, and PON activity in the blood plasma of both young and aged rats. Furthermore, fish oil supplementation decreased lipid peroxidation (MDA) and nitrite levels in both young and aged rats implying better antioxidant protection and a lower level of oxidative pressure after fish oil supplementation. Our results suggest that fish oil supplementation is beneficial regarding better antioxidant protection in both young and aged rats, while applied treatment differs in plasma phospholipids FAs composition

The elastic Maier-Saupe-Zwanzig model and some properties of nematic elastomers

We introduce a simple mean-field lattice model to describe the behavior of nematic elastomers. This model combines the Maier-Saupe-Zwanzig approach to liquid crystals and an extension to lattice systems of the Warner-Terentjev theory of elasticity, with the addition of quenched random fields. We use standard techniques of statistical mechanics to obtain analytic solutions for the full range of parameters. Among other results, we show the existence of a stress-strain coexistence curve below a freezing temperature, analogous to the P-V diagram of a simple fluid, with the disorder strength playing the role of temperature. Below a critical value of disorder, the tie lines in this diagram resemble the experimental stress-strain plateau, and may be interpreted as signatures of the characteristic polydomain-monodomain transition. Also, in the monodomain case, we show that random-fields may soften the first-order transition between nematic and isotropic phases, provided the samples are formed in the nematic state.Comment: 17 pages, 7 figure