4,524 research outputs found

    Anomalous coupling between topological defects and curvature

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    We investigate a counterintuitive geometric interaction between defects and curvature in thin layers of superfluids, superconductors and liquid crystals deposited on curved surfaces. Each defect feels a geometric potential whose functional form is determined only by the shape of the surface, but whose sign and strength depend on the transformation properties of the order parameter. For superfluids and superconductors, the strength of this interaction is proportional to the square of the charge and causes all defects to be repelled (attracted) by regions of positive (negative) Gaussian curvature. For liquid crystals in the one elastic constant approximation, charges between 0 and 4π4\pi are attracted by regions of positive curvature while all other charges are repelled.Comment: 5 pages, 4 figures, minor changes, accepted for publication in Phys. Rev. Let

    On Bisimilarity for Quasi-discrete Closure Spaces

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    Closure spaces, a generalisation of topological spaces, have shown to be a convenient theoretical framework for spatial model checking. The closure operator of closure spaces and quasi-discrete closure spaces induces a notion of neighborhood akin to that of topological spaces that build on open sets. For closure models and quasi-discrete closure models, in this paper we present three notions of bisimilarity that are logically characterised by corresponding modal logics with spatial modalities: (i) CM-bisimilarity for closure models (CMs) is shown to generalise Topo-bisimilarity for topological models. CM-bisimilarity corresponds to equivalence with respect to the infinitary modal logic IML that includes the modality N{\cal N} for ``being near''. (ii) CMC-bisimilarity, with `CMC' standing for CM-bisimilarity with converse, refines CM-bisimilarity for quasi-discrete closure spaces, carriers of quasi-discrete closure models. Quasi-discrete closure models come equipped with two closure operators, Direct C{\cal C} and Converse C{\cal C}, stemming from the binary relation underlying closure and its converse. CMC-bisimilarity, is captured by the infinitary modal logic IMLC including two modalities, Direct N{\cal N} and Converse N{\cal N}, corresponding to the two closure operators. (iii) CoPa-bisimilarity on quasi-discrete closure models, which is weaker than CMC-bisimilarity, is based on the notion of compatible paths. The logical counterpart of CoPa-bisimilarity is the infinitary modal logic ICRL with modalities Direct ζ\zeta and Converse ζ\zeta, whose semantics relies on forward and backward paths, respectively. It is shown that CoPa-bisimilarity for quasi-discrete closure models relates to divergence-blind stuttering equivalence for Kripke structures.Comment: 32 pages, 14 figure

    Full-Bloch beams and ultrafast Rabi-rotating vortices

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    Strongly-coupled quantum fields, such as multi-component atomic condensates, optical fields and polaritons, are remarkable systems where the simple dynamics of coupled oscillators can meet the intricate phenomenology of quantum fluids. When the coupling between the components is coherent, not only the particles number, but also their phase texture that maps the linear and angular momentum, can be exchanged. Here, on a system of exciton-polaritons, we have realized a so-called full-Bloch beam: a configuration in which all superpositions of the upper and the lower polariton -- all quantum states of the associated Hilbert space -- are simultaneously present at different points of the physical space, evolving in time according to Rabi-oscillatory dynamics. As a result, the light emitted by the cavity displays a peculiar dynamics of spiraling vortices endowed with oscillating linear and angular momentum and exhibiting ultrafast motion of their cores with striking accelerations to arbitrary speeds. This remarkable vortex motion is shown to result from distortions of the trajectories by a homeomorphic mapping between the Rabi rotation of the full wavefunction on the Bloch sphere and Apollonian circles in the real space where the observation is made. Such full-Bloch beams offer new prospects at a fundamental level regarding their topological properties or in the interpretation of quantum mechanics, and the Rabi-rotating vortices they yield should lead to interesting applications such as ultrafast optical tweezers.Comment: Published version, 18 pages, 8 figures, 4 ancillary movie

    SAFETY MONITORING BY MEANS OF SENSOR NETWORKS DISTRIBUTED WITHIN THE FOSSA SITE PLAN

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    Abstract. The seismic event of 6 April 2009 has inevitably left its mark on the history of the entire territory of L'Aquila (Italy), completely devastating the town and much of the province. Within such frantic and extensive reconstruction activity, the resulting construction works could not but draw attention to some issues of fundamental importance such as coordinated planning, safety, respect for the rules and above all the rebirth of the territory. This research is aimed at drawing up the site plan for Fossa, a municipality in the Province of L'Aquila and not far from the region capital of Abruzzo, Italy. The main objective is to create a monitoring standard by means of a dedicated sensors network and detailed strategies in order to coordinate, guide and support the single actions of intervention through design behaviours and highly technological tools. The Plan is configured as a tool for participatory planning, with the active involvement of planners, companies and citizens, whose common goal is the preservation of the identity of locations, the mitigation of seismic risk and the enhancement of the cultural heritage of the Municipality of Fossa. Implementation of this work is the application of technological systems for construction site monitoring: a concrete response to the growing demand for organized management of the construction process on site and safety in the workplace can be achieved through the use of systems and rational control and management procedures that include the use of innovative technologies

    CORONARY PERFUSION:IMPACT OF FLOW DYNAMICS AND GEOMETRIC DESIGN OF TWO DIFFERENT AORTIC PROSTHESES OF SIMILAR SIZE

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    BackgroundAortic valve replacement leads to improvement of coronary flow but not to complete normalization. Coronary hypoperfusion contributes to higher left ventricular mass persistence, arrhythmias, congestive heart failure and sudden death. This prospective study compares 2 similarly sized aortic prostheses (mechanical and porcine) regarding coronary flow and hemodynamic performances in patients who underwent surgery for pure aortic stenosis.MethodsSixty patients having undergone aortic valve replacement for pure aortic stenosis with Medtronic Mosaic Ultra bioprosthesis 21 mm (n = 30) or St Jude Regent mechanical valve 19 mm (n = 30) were evaluated preoperatively and 12 months postoperatively comparing the coronary flow and the hemodynamic behavior. Echocardiography and cardiac positron emission tomography were performed at rest and during exercise or adenosine maximal stimulation, respectively.ResultsThe St Jude Regent mechanical valve, compared with the Medtronic Mosaic Ultra bioprosthesis, had reduced coronary flow reserve (2.1 ± 0.3 vs 2.3 ± 0.2; P = .003), less favorable systolic/diastolic time ratio (0.87 ± 0.02 vs 0.78 ± 0.03; P < .001), and higher mean transprosthetic gradient (46 ± 11 vs 38 ± 9; P = .003) during exercise. Multivariate analysis of impaired coronary reserve related indexed effective orifice area less than 0.65 cm/m2 (risk ratio [RR], 1.9; 95% confidence intervals [CI], 1.5-2.8; P < .001), mechanical valve (RR, 2.5; 95% CI, 1.7-3.3; P < .001), and systolic/diastolic time ratio greater than 0.75 (RR, 2.6; 95% CI, 1.8-3.8; P < .001), as well as high transprosthetic gradient (RR, 1.7; 95% CI, 1.3-2.4; P < .001) ) during exercise with coronary reserve less than 2.2.ConclusionsImprovement of coronary flow and reserve was more evident for bioprostheses than for mechanical valves. The bioprostheses demonstrated superior hemodynamics during exercise, which may have some impact on exercise capability during normal daily life

    Ostial plication: a rarely reported cause of sudden death

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    We report a rare case of ostial plication as a potential cause of sudden death. Very few reports and images are available in the specialized literature regarding this anomaly. Ostial plication may be a source of sudden death or cause of death when no other significant autopsy findings are present

    Tumor Suppressors and Cell-Cycle Proteins in Lung Cancer

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    The cell cycle is the cascade of events that allows a growing cell to duplicate all its components and split into two daughter cells. Cell cycle progression is mediated by the activation of a highly conserved family of protein kinases, the cyclin-dependent kinases (CDKs). CDKs are also regulated by related proteins called cdk inhibitors grouped into two families: the INK4 inhibitors (p16, p15, p19, and p18) and the Cip/Kip inhibitors (p21, p27, and p53). Several studies report the importance of cell-cycle proteins in the pathogenesis and the prognosis of lung cancer. This paper will review the most recent data from the literature about the regulation of cell cycle. Finally, based essentially on the data generated in our laboratory, the expression, the diagnostic, and prognostic significance of cell-cycle molecules in lung cancer will be examined
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