993 research outputs found

    Nonlinear localized modes in dipolar Bose-Einstein condensates in optical lattices

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    The modulational instability and discrete matter wave solitons in dipolar BEC, loaded into a deep optical lattice, are investigated analytically and numerically. The process of modulational instability of nonlinear plane matter waves in a dipolar nonlinear lattice is studied and the regions of instability are established. The existence and stability of bulk discrete solitons are analyzed analytically and confirmed by numerical simulations. In a marked contrast with the usual DNLS behavior (no dipolar interactions), we found a region where the two fundamental modes are simultaneously unstable allowing enhanced mobility across the lattice for large norm values. To study the existence and properties of surface discrete solitons, an analysis of the dimer configuration is performed. The properties of symmetric and antisymmetric modes including the stability diagrams and bifurcations are investigated in closed form. For the case of a bulk medium, properties of fundamental on-site and inter-site localized modes are analyzed. On-site and inter-site surface localized modes are studied finding that they do not exist when nonlocal interactions predominate with respect to local ones.Comment: 12 pages, 13 figure

    Zika virus epidemiology: From Uganda to world pandemic, an update

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    Zika virus (ZIKV) infection is an emergent worldwide public health problem. Historically, 84 countries have reported vector-borne ZIKV transmission, 61 of which report on-going transmission. It is a Flavivirus transmitted through arthropods belonging to the Aedes genus. Since 2015, ZIKV infections have increased dramatically; with 1.3 million people infected during 2015 in Brazil alone. This paper's objective is to highlight the conjectural epidemiological points of the virus' dissemination. The digital archives Pubmed, MEDLINE, EMBASE and Cochrane were searched for papers that assessed aspects of ZIKV transmission and epidemiology. The first isolation occurred in Uganda in 1947. Since then, important outbreaks were documented globally. Consequently, an emergent public health problem arose from a rapidly increasing incidence and its association with the development of neurological diseases such as microcephaly and Guillain-Barré syndrome. Key factors in the successful containment of outbreaks include surveillance of mosquitos in the neighbourhood, an early mosquito control treatment, an assertive information campaign, and the involvement of the local population and healthcare workers. As such, while ZIKV seems to be spreading globally in a similar manner to other arboviruses, such as Dengue and Chikungunya viruses, it can also be rapidly contained due to the pre-existing availability of necessary resources and regulatory tools as control measures. This review aims to provide a description of those characteristics of ZIKV infection that may be useful in the construction of effective outbreak control strategies. Copyright © Cambridge University Press 2018

    Dinuclear organotin building blocks and their conversion into a tetranuclear macrocycle containing Sn-O-Sn linkages

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    Six dinuclear organotin building blocks of general composition RR′R′′SnCH2Si(CH3)2−biphenyl−Si(CH3)2CH2SnR′′R′R, in which the tin atoms are separated by a p,p′-biphenylene bridge and carry different substituents [BD1 with R, R′=CH2Si(CH3)3, R′′=Ph; BD2 with R, R′=CH2Si(CH3)3, R′′=Cl; BD3, with R, R′=CH2Si(CH3)3, R′′=I; BD4 with R=CH2Si(CH3)2(C5H4FeCp), R′, R′′=Ph; BD5 with R=CH2Si(CH3)2(C5H4FeCp), R′=Ph, R”=Cl; BD6 with R=CH2Si(CH3)2(C5H4FeCp), R′=Ph, R′′=I], were synthesized and characterized by spectroscopic and spectrometric methods. Furthermore, the crystal and molecular structures of BD2 were determined by single-crystal X-ray diffraction (SCXRD) analysis, revealing the formation of molecular strands through intermolecular Cl→Sn contacts. The 1D coordination polymer [BD2]n comprises macrocyclic rings of composition [BD2]2 that motivated the generation of a related molecular macrocyclic structure by reaction of BD2 with silver (I) oxide in a 2 : 2 stoichiometry. The [2+2] macrocyclization yielded the 30-membered tetra-nuclear ring structure M1, viz., {[R2SnCH2Si(CH3)2−biphenyl−(CH3)2SiCH2SnR2](μ-O)}2, in which two BD2 dinuclear building blocks are linked through two covalent Sn−O−Sn moieties. Examination by DFT calculations at the B3LYP/def2svp and B3LYP/6-31G*(C,H,O,Si)/LanL2DZ(Sn) levels of theory gave energy minima for molecular conformers of M1 carrying the Sn−O−Sn and p,p′-biphenylene bridges in syn- or anti-orientation

    Does ALS-FUS without FUS mutation represent ALS-FET? Report of three cases

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    Altres ajuts: This study was partially funded by Fundacio Marató de TV3 (grant no. 20143810 to RSV, no. 20141610 to EG and no. 201437.10 to RRG) and Fondo Europeo de Desarrollo Regional (FEDER) (PI16/01673 to JG and PI15/01618 to RRG). We are indebted to the Neurological Tissue Bank of the Biobanc-Hospital Clinic-IDIBAPS, Barcelona, Spain, for data and sample procurement. We thank Sara Charif, Veronica Santiago, Carmen Schweiger, Leire Etxarri and Abel Muñoz for technical assistance

    Scale-free and quantitative unique continuation for infinite dimensional spectral subspaces of Schrödinger operators

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    We prove a quantitative unique continuation principle for infinite dimensional spectral subspaces of Schr\"odinger operators. Let ΛL=(L/2,L/2)d\Lambda_L = (-L/2,L/2)^d and HL=ΔL+VLH_L = -\Delta_L + V_L be a Schr\"odinger operator on L2(ΛL)L^2 (\Lambda_L) with a bounded potential VL:ΛLRdV_L : \Lambda_L \to \mathbb{R}^d and Dirichlet, Neumann, or periodic boundary conditions. Our main result is of the type ΛLϕ2CsfucWδ(L)ϕ2, \int_{\Lambda_L} \lvert \phi \rvert^2 \leq C_{\mathrm{sfuc}} \int_{W_\delta (L)} \lvert \phi \rvert^2, where ϕ\phi is an infinite complex linear combination of eigenfunctions of HLH_L with exponentially decaying coefficients, Wδ(L)W_\delta (L) is some union of equidistributed δ\delta-balls in ΛL\Lambda_L and Csfuc>0C_{\mathrm{sfuc}} > 0 an LL-independent constant. The exponential decay condition on ϕ\phi can alternatively be formulated as an exponential decay condition of the map λχ[λ,)(HL)ϕ2\lambda \mapsto \lVert \chi_{[\lambda , \infty)} (H_L) \phi \rVert^2. The novelty is that at the same time we allow the function ϕ\phi to be from an infinite dimensional spectral subspace and keep an explicit control over the constant CsfucC_{\mathrm{sfuc}} in terms of the parameters. Moreover, we show that a similar result cannot hold under a polynomial decay condition

    Search for Axionlike and Scalar Particles with the NA64 Experiment

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    We carried out a model-independent search for light scalar (s) and pseudoscalar axionlike (a) particles that couple to two photons by using the high-energy CERN SPS H4 electron beam. The new particles, if they exist, could be produced through the Primakoff effect in interactions of hard bremsstrahlung photons generated by 100 GeV electrons in the NA64 active dump with virtual photons provided by the nuclei of the dump. The a(s) would penetrate the downstream HCAL module, serving as shielding, and would be observed either through their a(s)γγa(s)\to\gamma \gamma decay in the rest of the HCAL detector or as events with large missing energy if the a(s) decays downstream of the HCAL. This method allows for the probing the a(s) parameter space, including those from generic axion models, inaccessible to previous experiments. No evidence of such processes has been found from the analysis of the data corresponding to 2.84×10112.84\times10^{11} electrons on target allowing to set new limits on the a(s)γγa(s)\gamma\gamma-coupling strength for a(s) masses below 55 MeV.Comment: This publication is dedicated to the memory of our colleague Danila Tlisov. 7 pages, 5 figures, revised version accepted for publication in Phys. Rev. Let
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