Filament bifurcations in a one-dimensional model of reacting excitable fluid flow

Recently, it has been shown that properties of excitable media stirred by two-dimensional chaotic flows can be properly studied in a one-dimensional framework \cite{excitablePRL,excitablePRE}, describing the transverse profile of the filament-like structures observed in the system. Here, we perform a bifurcation analysis of this one-dimensional approximation as a function of the {\it Damk{\"o}hler} number, the ratio between the chemical and the strain rates. Different branches of stable solutions are calculated, and a Hopf bifurcation, leading to an oscillating filament, identified.Comment: 9 pages, 4 figures; elsart.cls styl

Low-dimensional dynamical system model for observed coherent structures in ocean satellite data

The dynamics of coherent structures present in real-world environmental data is analyzed. The method developed in this Paper combines the power of the Proper Orthogonal Decomposition (POD) technique to identify these coherent structures in experimental data sets, and its optimality in providing Galerkin basis for projecting and reducing complex dynamical models. The POD basis used is the one obtained from the experimental data. We apply the procedure to analyze coherent structures in an oceanic setting, the ones arising from instabilities of the Algerian current, in the western Mediterranean Sea. Data are from satellite altimetry providing Sea Surface Height, and the model is a two-layer quasigeostrophic system. A four-dimensional dynamical system is obtained that correctly describe the observed coherent structures (moving eddies). Finally, a bifurcation analysis is performed on the reduced model.Comment: 23 pages, 7 figure

Effects of aluminum and zinc on the oxidative stress caused by 6-hydroxydopamine autoxidation: relevance for the pathogenesis of Parkinson’s disease

AbstractAluminum and zinc have been related to the pathogenesis of Parkinson’s disease (PD), the former for its neurotoxicity and the latter for its apparent antioxidant properties. 6-Hydroxydopamine (6-OHDA) is an important neurotoxin putatively involved in the pathogenesis of PD, its neurotoxicity often being related to oxidative stress. The potential effect of these metals on the oxidative stress induced by 6-OHDA autoxidation and the potential of ascorbic acid (AA), cysteine, and glutathione to modify this effect were investigated. Both metals, particularly Al3+, induced a significant reduction in ⋅OH production by 6-OHDA autoxidation. The combined action of AA and a metal caused a significant and sustained increase in ⋅OH generation, particularly with Al3+, while the effect of sulfhydryl reductants was limited to only the first few minutes of the reaction. However, both Al3+ and Zn2+ provoked a decrease in the lipid peroxidation induced by 6-OHDA autoxidation using mitochondrial preparations from rat brain, assessed by TBARS formation. In the presence of AA, only Al3+ induced a significant reduction in lipid peroxidation. After intrastriatal injections of 6-OHDA in rats, tyrosine hydroxylase immunohistochemistry revealed that Al3+ reduces 6-OHDA-induced dopaminergic lesion in the striatum, which corroborates the involvement of lipid peroxidation in 6-OHDA neurotoxicity and appears to discard the participation of this mechanism on PD by Al3+ accumulation. The previously reported antioxidant properties of Zn2+ appear to be related to the induction of Zn2+-containing proteins and not to the metal per se

Characterization of surface layers in Zn-diffused LiNbO3 waveguides by heavy ion elastic recoil detection

Copyright (2002) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Applied Physics Letters 81.11 (2002): 1981-1983 and may be found at http://apl.aip.org

Source analysis of polyspike and wave complexes in juvenile myoclonic epilepsy

AbstractWe applied dipole modeling and brain distributed source analysis to find current sources comprising spikes and slow waves of polyspike and wave complexes (PSWC) in patients with juvenile myoclonic epilepsy (JME). The dipoles were localized in frontal, parietal and temporal lobes. The frontal dipoles were clustered in the frontal medial gyrus and fronto-orbital region. A midsagittal frontal current source was observed using brain distributed source analysis in all patients. When the slow wave was analyzed, multiple sources in different cortical regions were detected using dipole modeling and brain distributed analysis. These results show pre-frontal medial current sources corresponding to spikes and many diffuse sources in cortical regions corresponding to wave components of PSWC in patients with JME

A thermophysical study of the melting process in alkyl chain metal n-alkanoates: The thallium (I) series

The peculiar thermal behavior of the thallium(I) n-alkanoates series (consisting in several transitions between polymorphic and mesomorphic phases) in comparison with other metallic n-alkanoates series is stated. The allowance of highly accurate adiabatic heat capacity data permits a study of the CH2CH2 contributions to the lattice heat capacity curve at low temperature. Moreover, in this series an anomalous gradual enhancement of the lattice heat capacity has been interpreted from vibrational spectroscopy results as a noncooperative effect due to the internal hindered rotation of the alkyl chain (formation of gauche defects, even in the solid state). The thermodynamics of the “stepwise melting process” from the totally ordered solid at low temperature to the isotropic liquid is based on a revised lattice heat-capacity curve. This was used to evaluate the energy and entropy not only of the clear first order transitions present in the series but also of the described noncooperative effect. The CH2CH2 enthalpy and entropy contribution for this series is estimated and a comparison with the published values for other series is carried out. Moreover, the texture of the mesophases is revealed by polarized light microscopy. © 1999 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69602/2/JCPSA6-111-8-3590-1.pd

DNA polymerase lambda (Pol λ), a novel eukaryotic DNA polymerase with a potential role in meiosis

A new gene (POLL) encoding a novel DNA polymerase (Pol λ) has been identified at mouse chromosome 19. Murine Pol λ, consisting of 573 amino acid residues, has a 32 % identity to Pol β, involved in nuclear DNA repair in eukaryotic cells. It is interesting that Pol λ contains all the critical residues involved in DNA binding, nucleotide binding and selection, and catalysis of DNA polymerization, that are conserved in Pol β and other DNA polymerases belonging to family X. Murine Pol λ, overproduced in Escherichia coli, displayed intrinsic DNA polymerase activity when assessed by in situ gel analysis. Pol λ also conserves the critical residues of Pol β required for its intrinsic deoxyribose phosphate lyase (dRPase) activity. The first 230 amino acid residues of Pol λ, that have no counterpart in Pol β, contain a BRCT domain, present in a variety of cell-cycle check-point control proteins responsive to DNA damage and proteins involved in DNA repair. Northern blotting, in situ hybridization analysis and immunostaining showed high levels of Pol λ specifically expressed in testis, being developmentally regulated and mainly associated to pachytene spermatocytes. These first evidences, although indirect, suggest a potential role of Pol λ in DNA repair synthesis associated with meiosis.This work has been granted by DGES (PB97-1192) and CAM (08.1/0044/98) to LB; CAM(08.1/0044.2/98) to AB; DGICYT (PB 95-0119), EC PL96-0183 and CAM (07/0022) to JM, and by an institutional grant from Fundación Ramón Areces

A "core-complex-type structure" formed by superposed ductile and brittle extension followed by folding and high-angle normal faulting. The Santi Petri dome (western Betics, Spain)

The Santi Petri dome (western Betics, southern Spain) shows a core-complex-like structure, where migmatitic gneisses and schists outcrop below low-grade slates and phyllites, all of which form the basement of the Neogene Málaga basin. The migmatites and schists suffered a coaxial-flattening event during isothermal decompression and were later exhumed by ductile ESE non-coaxial stretching. Further exhumation was achieved by W- to SW-transport brittle low-angle normal faulting. Subsequently these extensional structures were gently folded in the core of a NE/SW-oriented antiform during the Tortonian. Finally the Santi Petri domal geometry was accentuated by the interference of orthogonal high-angle faults with ENE–WSW and NNW–SSE orientation. This core-complex-like structure, formed by superposition of extensional and compressive tectonic events, does not represent a classical, purely extensional core complex, which shows that metamorphic structure and geometry are not decisive criteria to define a core-complex

Mathematical modeling of gallic acid release from chitosan films with grape seed extract and carvacrol

Controlled release of antimicrobial and antioxidant compounds from packaging films is of utmost importance for extending the shelf-life of perishable foods. This study focused on the mathematical modeling of gallic acid release into an aqueous medium from three chitosan films, formulated with grape seed extract (GSE) and carvacrol. We quantified the release by HPLC technique during 30days at three temperatures (5, 25 and 45°C). The diffusion coefficients, varying with temperature according to an Arrhenius-type relationship, and the respective activation energies for Film-1 and Film-2 were, respectively [Formula: see text] m2s-1 and [Formula: see text] m2s-1, Ea1=58kJmol-1 and Ea2=60kJmol-1 as obtained from the Fickian fit. The low concentrations of gallic acid released by Film-3 could not be detected by HPLC, therefore the respective diffusion coefficient was not estimated. This study will help with the development and optimization of active packaging (AP) films aiming at improved food preservation and shelf-life extension.Javiera F. Rubilar gratefully acknowledges her Ph.D. grant from ErasmusMundus 2008-1022/001 Frame ECW/17, EACEA(European Union), financial support of the Fondecyt-Postdoctoral #3140349 project from CONICYT, and also “Dirección de Investigación e Innovación Escuela de Ingeniería” at Pontificia Universidad Católica de Chile. Rui M. S. Cruz acknowledges grant SFRH/BPD/70036/2010 from Fundac¸ ão para a Ciência e Tecnologia, Portugalinfo:eu-repo/semantics/publishedVersio