Numerical Modelling of Optical Trapping

Optical trapping is a widely used technique, with many important applications in biology and metrology. Complete modelling of trapping requires calculation of optical forces, primarily a scattering problem, and non-optical forces. The T-matrix method is used to calculate forces acting on spheroidal and cylindrical particles.Comment: 4 pages, 4 figure

Fluctuations, dissipation and the dynamical Casimir effect

Vacuum fluctuations provide a fundamental source of dissipation for systems coupled to quantum fields by radiation pressure. In the dynamical Casimir effect, accelerating neutral bodies in free space give rise to the emission of real photons while experiencing a damping force which plays the role of a radiation reaction force. Analog models where non-stationary conditions for the electromagnetic field simulate the presence of moving plates are currently under experimental investigation. A dissipative force might also appear in the case of uniform relative motion between two bodies, thus leading to a new kind of friction mechanism without mechanical contact. In this paper, we review recent advances on the dynamical Casimir and non-contact friction effects, highlighting their common physical origin.Comment: 39 pages, 4 figures. Review paper to appear in Lecture Notes in Physics, Volume on Casimir Physics, edited by Diego Dalvit, Peter Milonni, David Roberts, and Felipe da Rosa. Minor changes, a reference adde

Realistic Equations of State for the Primeval Universe

Early universe equations of state including realistic interactions between constituents are built up. Under certain reasonable assumptions, these equations are able to generate an inflationary regime prior to the nucleosynthesis period. The resulting accelerated expansion is intense enough to solve the flatness and horizon problems. In the cases of curvature parameter \kappa equal to 0 or +1, the model is able to avoid the initial singularity and offers a natural explanation for why the universe is in expansion.Comment: 32 pages, 5 figures. Citations added in this version. Accepted EPJ

Ultrarelativistic electron-hole pairing in graphene bilayer

We consider ground state of electron-hole graphene bilayer composed of two independently doped graphene layers when a condensate of spatially separated electron-hole pairs is formed. In the weak coupling regime the pairing affects only conduction band of electron-doped layer and valence band of hole-doped layer, thus the ground state is similar to ordinary BCS condensate. At strong coupling, an ultrarelativistic character of electron dynamics reveals and the bands which are remote from Fermi surfaces (valence band of electron-doped layer and conduction band of hole-doped layer) are also affected by the pairing. The analysis of instability of unpaired state shows that s-wave pairing with band-diagonal condensate structure, described by two gaps, is preferable. A relative phase of the gaps is fixed, however at weak coupling this fixation diminishes allowing gapped and soliton-like excitations. The coupled self-consistent gap equations for these two gaps are solved at zero temperature in the constant-gap approximation and in the approximation of separable potential. It is shown that, if characteristic width of the pairing region is of the order of magnitude of chemical potential, then the value of the gap in the spectrum is not much different from the BCS estimation. However, if the pairing region is wider, then the gap value can be much larger and depends exponentially on its energy width.Comment: 13 pages with 8 figures; accepted to Eur. Phys. J.

Three-dimensional reconstruction of coronary arteries and plaque morphology using CT angiography - comparison and registration with IVUS

Background: The aim of this study is to present a new methodology for three-dimensional (3D) reconstruction of coronary arteries and plaque morphology using Computed Tomography Angiography (CTA). Methods: The methodology is summarized in six stages: 1) pre-processing of the initial raw images, 2) rough estimation of the lumen and outer vessel wall borders and approximation of the vessel's centerline, 3) manual adaptation of plaque parameters, 4) accurate extraction of the luminal centerline, 5) detection of the lumen - outer vessel wall borders and calcium plaque region, and 6) finally 3D surface construction. Results: The methodology was compared to the estimations of a recently presented Intravascular Ultrasound (IVUS) plaque characterization method. The correlation coefficients for calcium volume, surface area, length and angle vessel were 0.79, 0.86, 0.95 and 0.88, respectively. Additionally, when comparing the inner and outer vessel wall volumes of the reconstructed arteries produced by IVUS and CTA the observed correlation was 0.87 and 0.83, respectively. Conclusions: The results indicated that the proposed methodology is fast and accurate and thus it is likely in the future to have applications in research and clinical arena

A GEOMORFOLOGIA NO CONTEXTO DO PLANEJAMENTO AMBIENTAL: ESTUDO DO USO E OCUPAÇÃO DA SERRA BARRA DO VENTO – SERRINHA/BA

O uso e ocupação das terras em ambiente semiárido pode intensificar o aparecimento de processos de degradação ambiental. Objetiva-se Analisar a interação das características geomorfológicas com o uso e a ocupação das terras na Serra Barra do Vento, contribuindo para o planejamento ambiental, a partir do processamento de imagens orbitais e atividade de campo. Este estudo justifica-se pela necessidade de entender a contribuição da geomorfologia no uso/ocupação em ambiente semiárido

Paralytic shellfish toxins occurrence in non-traditional invertebrate vectors from north Atlantic waters (Azores, Madeira, and Morocco)

Paralytic shellfish toxins (PSTs) are potent alkaloids of microalgal and cyanobacterial origin, with worldwide distribution. Over the last 20 years, the number of poisoning incidents has declined as a result of the implementation of legislation and monitoring programs based on bivalves. In the summer of 2012 and 2013, we collected a total of 98 samples from 23 different species belonging to benthic and subtidal organisms, such as echinoderms, crustaceans, bivalves, and gastropods. The sampling locations were Madeira, São Miguel Island (Azores archipelago), and the northwestern coast of Morocco. The samples were analyzed using post-column oxidation liquid chromatography with a fluorescence detection method. Our main goal was to detect new vectors for these biotoxins. After reporting a total of 59 positive results for PSTs with 14 new vectors identified, we verified that some of the amounts exceeded the limit value established in the EU. These results suggest that routine monitoring of saxitoxin and its analogs should be extended to more potential vectors other than bivalves, including other edible organisms, for a better protection of public health. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.Department of Biology, Science Faculty, University of Porto, Rua do Campo Alegre, 4619-007 Porto, Portugal; [email protected] (A.B.); [email protected] (V.V.) Interdisciplinary Center of Marine and Environmental Research-CIMAR/CIIMAR, University of Porto, Novo Edificio do Terminal de Cruzeiros do Porto de Leixões, Avenida General Norton de Matos, 4450-208 S/N Matosinhos, Portugal; [email protected] Department of Analytical Chemistry, Science Faculty, University of Santiago de Compostela, 27002 Lugo, Spain; [email protected] (V.R.); [email protected] (A.B.) Life Sciences Faculty, Madeira University, Marine Biology Station, 9000-107 Funchal, Madeira Island, Portugal Center of Interdisciplinary Marine and Environmental Research of Madeira-CIIMAR-Madeira, Edificio Madeira Tecnopolo, Caminho da Penteada, 9020-105 Funchal, Madeira, Portugal cE3c/GBA—Centre for Ecology, Evolution and Environmental Changes/Azorean Biodiversity Group and Department of Biology, Faculty of Sciences and Technology, University of Azores, 9501-801 Ponta Delgada, São Miguel, Azores, Portugal; [email protected] Phycology Research Unit-Biotechnology, Ecosystems Ecology and Valorization Laboratory, Science Faculty, University of Chouaib Doukkali, El Jadida BP20, Morocco; [email protected] (M.H.); [email protected] (B.S.) Department of Pharmacology, Veterinary Faculty, University of Santiago de Compostela, 27002 Lugo, Spain; [email protected] Correspondence: [email protected]; Tel.: +351-2234-01800; Fax: +351-2233-80609 This authors contributed equally to this work. Funding: This research was partially funded by the Portuguese Fundation of Science and Technology (FCT) project UID/Multi/04423/2013 and by the projects ALERTOXNET (EAPA_317/2016), funded by the Interreg Atlantic program. The Spanish research leading to these results has received funding from the following European Fund for Economic and Regional Development (FEDER) cofunded-grants: Centro para el Desarrollo Tecnológico Industrial (CDTI) and Technological Funds, supported by Ministerio de Economía y Competitividad, AGL2012-40185-CO2-01, AGL2014-58210-R, and Consellería de Cultura, Educación e Ordenación Universitaria, GRC2013-016; CDTI under India&Spain Innovating Program (ISIP) Programme, Spain, IDI-20130304 APTAFOOD; the European Union’s Seventh Framework Programme managed by REA—Research Executive Agency (FP7/2007-2013) under grant agreement 312184 PHARMASEA

Chemical and electrochemical study of fabrics coated with reduced graphene oxide

Polyester fabrics coated with reduced graphene oxide (RGO) have been obtained and later characterized by means of chemical and electrochemical techniques. X-ray photoelectron spectroscopy showed a decrease of the oxygen content as well as an increase of the sp2 fraction after chemical reduction of graphene oxide (GO). The electrical conductivity was measured by electrochemical impedance spectroscopy (EIS) and showed a decrease of 5 orders of magnitude in the resistance (¿) when GO was reduced to RGO. The phase angle also changed from 90° for PES-GO (capacitative behavior) to 0° for RGO coated fabrics (resistive behavior). In general an increase in the number of RGO layers produced an increase of the conductivity of the fabrics. EIS measurements in metal/sample/electrolyte configuration showed better electrocatalytic properties and faster diffusion rate for RGO specimens. Scanning electrochemical microscopy was employed to test the electroactivity of the different fabrics obtained. The sample coated with GO was not conductive since negative feedback was obtained. When GO was reduced to RGO the sample behaved like a conducting material since positive feedback was obtained. Approach curves indicated that the redox mediator had influence on the electrochemical response. The Fe(CN)63¿/4¿ redox mediator produced a higher electrochemical response than Ru(NH3)63+/2+ one.Authors thank to the Spanish Ministerio de Ciencia e Innovacion (contract CTM2011-23583) and Universitat Politecnica de Valencia (Vicerrectorado de Investigacion PAID-06-10 contract 003-233) for the financial support. J. Molina is grateful to the Conselleria d'Educacio (Generalitat Valenciana) for the FPI fellowship. A.I. del Rio is grateful to the Spanish Ministerio de Ciencia y Tecnologia for the FPI fellowship. J.C. Galvan is gratefully acknowledged for help with EIS measurements and data analysis.Molina Puerto, J.; Fernández Sáez, J.; Del Río García, AI.; Bonastre Cano, JA.; Cases Iborra, FJ. (2013). Chemical and electrochemical study of fabrics coated with reduced graphene oxide. Applied Surface Science. 279:46-54. https://doi.org/10.1016/j.apsusc.2013.04.020S465427