4,519 research outputs found

    A revision of the striatella species group of the genus Rhagoletis (Diptera: Tephritidae)

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    A taxonomic revision of species of the striatella group, including descriptions ofthree new species from Mexico, Nicaragua and Costa Rica is presented. To date we recognize 6 species in this group: Rhagoletis striatella, R. jamaicensis, R. macquartii, R. triangularis n. sp., R. nicaraguensis n. sp., and R. solanophaga n. sp. Information and records about their distribution, known host plants, and morphological relationships among the species are discussed. A key to the species within the group is presented.Se presenta una revision taxonomic a de las especies del grupo striatella, la cual incluye descripciones de tres nuevas especies provenientes de Mexico, Nicaragua y Costa Rica. Ala fecha reconocemos 6 especies en este grupo: Rhagoletis striatella, R. jamaicensis, R. macquartii, R. triangularis n. sp., R. nicaraguensis n. sp., and R. solanophaga n. sp .. Se discute informacion sobre su distribucion, plantas hospederas conocidas, y las relaciones morfologicas entre sus especies. Ademas se presenta una clave para separar todas las especies del grupo

    Locating the critical end point using the linear sigma model coupled to quarks

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    We use the linear sigma model coupled to quarks to compute the effective potential beyond the mean field approximation, including the contribution of the ring diagrams at finite temperature and baryon density. We determine the model couplings and use them to study the phase diagram in the baryon chemical potential-temperature plane and to locate the Critical End Point.Comment: 8 pages, 2 figures, conference paper from ISMD 201

    A Drop of Active Matter

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    We study theoretically the hydrodynamics of a fluid drop containing oriented filaments endowed with active contractile or extensile stresses and placed on a solid surface. The active stresses alter qualitatively the wetting properties of the drop, leading to new spreading laws and novel static drop shapes. Candidate systems for testing our predictions include cytoskeletal extracts with motors and ATP, suspensions of bacteria or pulsatile cells, or fluids laden with artificial self-propelled colloids.Comment: submitted to J Fluid Mec

    DESIGN AND REGIOSELECTIVE SYNTHESIS OF TWO AND THREE-PRONGED C\u3csub\u3e60\u3c/sub\u3e FULLERENE DERIVATIVES AND THEIR APPLICATIONS IN MOLECULAR ELECTRONICS

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    Since the introduction of semiconductors in the second half of the 20th century, advancements in electronics and technology have been tremendous. In particular, the rapid development of silicon-based computer chip technology and miniaturization of electronic components has been tremendous. Since silicon-based materials have a limit in terms of size, scientists proposed that individual molecules could behave as single electronic components for high degree of miniaturization. Given that the molecules of interest must have dimensions on the nanometer scale, be able to bind to the electrode surface and have electron donor-acceptor properties, C60 fullerene has been a prime candidate for these studies. It has also been found that a covalent bond between a C60 derivative and the surface of a metal substrate enhances the electron tunneling conductance upon accepting electrons, demonstrating the importance of the design and regioselective synthesis of C60 fullerene derivatives. However, regiochemical control is very challenging given its high symmetry. The work presented here explores the synthesis, characterization and electrochemical properties of pentakis-, hexakis- and heptakis-adducts of C60 and some of its Fe-complexes under a regio-controlled protection-deprotection protocol. Derivatives were synthesized using two known reactions: cyclopropanation and 1,3-dipolar cycloaddition reactions, better known as: as the Bingel-Hirsch and Prato reactions, respectively. This approach allowed us to introduce the addends in specific positions over the sphere. For example, two pyrrolidine groups were bonded in a trans-1 relationship with respect to each other. These adducts were characterized by means of 1H, 13C, and 2D-NMR, UV-vis, MALDI-TOF MS and ESI-MS. Their electrochemical properties were analyzed by Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV) experiments

    Aspects of the pseudo Chiral Magnetic Effect in 2D Weyl-Dirac Matter

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    A connection is established between the continuum limit of the low-energy tight-binding description of graphene immersed in an in-plane magnetic field and the Chiral Magnetic Effect in Quantum Chromodynamics. A combination of mass gaps that explicitly breaks the equivalence of the Dirac cones, favoring an imbalance of pseudo-chiralities, is the essential ingredient to generate a non-dissipative electric current along the external field. Currents, number densities and condensates generated from this setup are investigated for different hierarchies of the energy scales involved.Comment: 12 pages, 8 figures. Several text improvements. Accepted for publication in European Physical Journal

    A new hydrodynamic spherical accretion exact solution and its quasi-spherical perturbations

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    We present an exact γ=5/3\gamma=5/3 spherical accretion solution which modifies the Bondi boundary condition of ρconst.\rho \to const. as rr\to \infty to ρ0\rho \to 0 as rr \to \infty. This change allows for simple power law solutions on the density and infall velocity fields, ranging from a cold empty free-fall condition where pressure tends to zero, to a hot hydrostatic equilibrium limit with no infall velocity. As in the case of the Bondi solution, a maximum accretion rate appears. As in the γ=5/3\gamma=5/3 case of the Bondi solution, no sonic radius appears, this time however, because the flow is always characterised by a constant Mach number. This number equals 1 for the case of the maximum accretion rate, diverges towards the cold empty state, and becomes subsonic towards the hydrostatic equilibrium limit. It can be shown that in the limit as { r0r \to 0}, the Bondi solution tends to the new solution presented, { extending the validity of the Bondi accretion value to} cases where the accretion density profile does not remain at a fixed constant value out to infinity. We then explore small deviations from sphericity and the presence of angular momentum through an analytic perturbative analysis. Such perturbed solutions yield a rich phenomenology through density and velocity fields in terms of Legendre polynomials, which we begin to explore for simple angular velocity boundary conditions having zeros on the plane and pole. The new solution presented provides complementary physical insight into accretion problems in general.Comment: Accepted for publication in the ApJ. 10 figures, extended comparison to observations and first numerical tests include
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