766 research outputs found

    High-order harmonic generation driven by chirped laser pulses induced by linear and non linear phenomena

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    We present a theoretical study of high-order harmonic generation (HHG) driven by ultrashort optical pulses with different kind of chirps. The goal of the present work is perform a detailed study to clarify the relevant parameters in the chirped pulses to achieve a noticeable cut-off extensions in HHG. These chirped pulses are generated using both linear and nonlinear dispersive media.The description of the origin of the physical mechanisms responsible of this extension is, however, not usually reported with enough detail in the literature. The study of the behaviour of the harmonic cut-off with these kind of pulses is carried out in the classical context, by the integration of the Newton-Lorentz equation complemented with the quantum approach, based on the integration of the time dependent Schr\"odinger equation in full dimensions (TDSE-3D), we are able to understand the underlying physics.Comment: 13 pages, 8 figure

    Anisotropic lattice changes in femtosecond laser inscribed Nd3+:MgO:LiNbO3 optical waveguides

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    We report on the fabrication and microspectroscopy imaging of femtosecond laser written double-filament based Nd3+ :MgO:LiNbO3 optical waveguides. The waveguiding high refractive-index regions are identified by blueshifts of the Nd3+ ion fluorescence lines with no deterioration in the fluorescence efficiency, whereas filamentary low-index regions are identified by both a Nd3+ line redshift and a fluorescence efficiency reduction. The lattice structural micromodifications at the origin of both waveguide formation and Nd3+ fluorescence changes have been investigated by means of confocal micro-Raman experiments. We have found that the direct laser written filaments are mainly constituted by a large density of defects, together with a marked axial compression perpendicular to the filaments �along the optical c-axis�. Conversely, the high-index waveguiding regions are characterized by a pronounced anisotropic dilatation of the LiNbO3 lattice xy-planes

    Spatial Modulation of linear and quadratic susceptibilities in Lithium Niobate crystals by using femtosecond laser pulses

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    In this work we present the spatial control of the linear susceptibility (χ1) in Lithium Niobate crystals by means of infrared (800 nm) femtosecond interaction. Diffraction gratings have been performed on the surface (relief) and inside (phase) of these samples by femtosecond laser writing. Also we have performed a spatial control of the quadratic susceptibility (χ 2 ) by direct writing of a pattern of ferroelectric domains on the surface of z cut substrates by using the second harmonic femtosecond pulses (400 nm). Finally, efficient photonic devices for second harmonic generation via quasi phase matching could be obtained following the experimental procedure presented in this work

    Outer Membrane Vesicles of a Human Commensal Mediate Immune Regulation and Disease Protection

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    Commensal bacteria impact host health and immunity through various mechanisms, including the production of immunomodulatory molecules. Bacteroides fragilis produces a capsular polysaccharide (PSA), which induces regulatory T cells and mucosal tolerance. However, unlike pathogens, which employ secretion systems, the mechanisms by which commensal bacteria deliver molecules to the host remain unknown. We reveal that Bacteroides fragilis releases PSA in outer membrane vesicles (OMVs) that induce immunomodulatory effects and prevent experimental colitis. Dendritic cells (DCs) sense OMV-associated PSA through TLR2, resulting in enhanced regulatory T cells and anti-inflammatory cytokine production. OMV-induced signaling in DCs requires growth arrest and DNA-damage-inducible protein (Gadd45α). DCs treated with PSA-containing OMVs prevent experimental colitis, whereas Gadd45α^(−/−) DCs are unable to promote regulatory T cell responses or suppress proinflammatory cytokine production and host pathology. These findings demonstrate that OMV-mediated delivery of a commensal molecule prevents disease, uncovering a mechanism of interkingdom communication between the microbiota and mammals

    Solid state NMR and X-ray diffraction studies of α-d-galacturonic acid monohydrate

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    Crystalline a-d-galacturonic acid monohydrate has been studied by 13C CPMAS NMR and X-ray crystallography. The molecular dynamics were investigated by evaluating 13C spin-lattice relaxation in the rotating frame (T1?) and chemical-shift-anisotropy properties of each carbon. Only limited molecular motions can be detected in the low frequency

    OCTANE (ontario-wide cancer targeted nucleic acid evaluation): A platform for intraprovincial, national, and international clinical data-sharing

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    Cancer is a genetic disease resulting from germline or somatic genetic aberrations. Rapid progress in the field of genomics in recent years is allowing for increased characterization and understanding of the various forms of the disease. The Ontario-wide Cancer Targeted Nucleic Acid Evaluation (octane) clinical trial, open at cancer centres across Ontario, aims to increase access to genomic sequencing of tumours and to facilitate the collection of clinical data related to enrolled patients and their clinical outcomes. The study is designed to assess the clinical utility of next-generation sequencing (ngs) in cancer patient care, including enhancement of treatment options available to patients. A core aim of the study is to encourage collaboration between cancer hospitals within Ontario while also increasing international collaboration in terms of sharing the newly generated data. The single-payer provincial health care system in Ontario provides a unique opportunity to develop a province-wide registry of ngs testing and a repository of genomically characterized, clinically annotated samples. It also provides an important opportunity to use province-wide real-world data to evaluate outcomes and the cost of ngs for patients with advanced cancer. The octane study is attempting to translate knowledge to help deliver precision oncology in a Canadian environment. In this article, we discuss the background to the study and its implementation, current status, and future directions
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