Non-paraxial Talbot effect in one-dimensional gratings with period comparable to the wavelength

The Talbot effect is a diffractive phenomenon which was found since its inception in the Gaussian optics, but when the period of the object is comparable with the wavelength is considered entering its non-paraxial regime. There, it has attracted interest for its applications related to the design of objects and their restorative effects posing in damaged gratings on this scale. In this contribution a study of this phenomenon at level non-paraxial (metaxial) is presented by using scalar diffraction theory in plane waves representation for periodic transversal fields. To this end, a one-dimensional amplitude grating of period p is used which is illuminated by a monochromatic plane wave of wavelength λ where p ranges between 1,5 λ and 4,2 λ.Fil: Arrieta, E.. Universidad Popular del Cesar; ColombiaFil: Bolognini, Nestor Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; ArgentinaFil: Torres, C.O.. Universidad Popular del Cesar; Colombi

Cohomological dimension and arithmetical rank of some determinantal ideals

Let $M$ be a $(2 \times n)$ non-generic matrix of linear forms in a polynomial ring. For large classes of such matrices, we compute the cohomological dimension (cd) and the arithmetical rank (ara) of the ideal $I_2(M)$ generated by the $2$-minors of $M$. Over an algebraically closed field, any $(2 \times n)$-matrix of linear forms can be written in the Kronecker-Weierstrass normal form, as a concatenation of scroll, Jordan and nilpotent blocks. B\u{a}descu and Valla computed $\mathrm{ara}(I_2(M))$ when $M$ is a concatenation of scroll blocks. In this case we compute $\mathrm{cd}(I_2(M))$ and extend these results to concatenations of Jordan blocks. Eventually we compute $\mathrm{ara}(I_2(M))$ and $\mathrm{cd}(I_2(M))$ in an interesting mixed case, when $M$ contains both Jordan and scroll blocks. In all cases we show that $\mathrm{ara}(I_2(M))$ is less than the arithmetical rank of the determinantal ideal of a generic matrix

Study of channeling phenomena in bent crystals: the new frontiers

More or less 30 years ago, it was experimentally demonstrated how a bent crystal can become a magnet: an object 1 mm thick, a couple of mm wide and a few cm high is, in fact, capable of steering particles as a dipole of several tens of Tesla. Exploiting this feature, from September 2006 the H8RD22 collaboration is testing several bent crystals in order to develop a crystal based collimation system for LHC: in very high energy accelerators, in fact, the typical multi-stage collimation system (that must be very efficient and must tolerate very high radiation) is expected not to allow to reach the nominal luminosity, limiting it to 40% of the desired value. A bent crystal could play a key role being a clever collimator: it is able to steer particles in a given direction with a high efficiency, thus increasing the cleaning efficiency, reducing the constraints on the alignment of the secondary collimator and finally increasing luminosity. But bent crystals are not only collimation: the radiation emitted by light particles in such crystals could be a real breakthrough for several applications, from the the generation of intense gamma beams for a positron source to the collimation of electron-positron beams at the future linear collider. This study is still an open field, given the constraints on the beam and on the experimental setup. The goal of this thesis work is to give an insight of the physics of bent crystals from several poin ts of view: their behavior with heavy and light particles, the possible applications in different fields and the experimental results obtained in recent beam tests with 400 GeV/c and 180 GeV/c heavy and light particles

Tempi di in/sicurezza alimentare: un approccio giuridico

Muovendo dalla considerazione che la food security indica il livello di autosufficienza nell\u2019approvvigionamento alimentare, mentre la food safety si riferisce all\u2019idoneit\ue0 del prodotto alimentare a non arrecare danni alla salute del consumatore, il presente lavoro cerca di offrire un quadro \u2013 sintetico \u2013 delle problematiche con cui \ue8 tenuto a confrontarsi il giurista che si occupa di diritto agrario e di diritto alimentare allorquando si accosta al tema dell\u2019insicurezza alimentare, guardando, pi\uf9 nello specifico, alla realt\ue0 europea

Single-random phase encoding architecture using a focus tunable lens

We propose a new nonlinear optical architecture based on a focus tunable lens and an iterative phase retrieval algorithm. It constitutes a compact encryption system that uses a single-random phase key to simultaneously encrypt (decrypt) amplitude and phase data. Summarily, the information encoded in a transmittance object (phase and amplitude) is randomly modulated by a diffuser when a laser beam illuminates it; once the beam reaches a focus tunable lens, different subjective speckle distributions are registered at some image plane as the focal length is tuned to different values. This set of speckle patterns constitutes a delocalized ciphertext, which is used in an iterative phase retrieval algorithm to reconstruct a complex ciphertext. The original data are decrypted propagating this ciphertext through a virtual optical system. In this system, amplitude data are straightforwardly decrypted while phase data can only be restored if the random modulation produced in the encryption process is compensated. Thus, an encryption-decryption process and authentication protocol can simultaneously be performed. We validate the feasibility of our proposal with simulated and experimental results.Fil: Mosso Solano, Edward Fabian. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Pontificia Universidad Católica de Valparaíso; ChileFil: Bolognini, Nestor Alberto. Universidad Nacional de La Plata. Facultad de Ciencias Exactas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; ArgentinaFil: Pérez, D.G.. Pontificia Universidad Católica de Valparaíso; Chil

Pharmacological properties of the phytocannabinoids \u3949-tetrahydrocannabivarin and cannabidiol.

Cannabis and its derivatives have been used for medicinal purpose for thousand of years. More recently, the main cannabis constituents, cannabinoids, have been found to act and target at cannabinoid as well as other receptors. This brought particular interest around the pharmacology of phytocannabinoids and their possible clinical applications. The research object of this study focused on two phytocannabinoids, \u3949-tetrahydrocannabivarin (\u3949-THCV) and cannabidiol (CBD), and it has been divided in three individual investigations: In the first study, we investigated the pharmacology of \u3949-THCV at cannabinoid type 1 (CB1) and type 2 (CB2) receptors. We found and confirmed that \u3949-THCV acts as antagonist at CB1 receptors in experiments of [35S]GTP\u3b3S binding assay on human CB1-CHO (Chinese hamster ovary) cell membranes. Also, in the same set of experiments, \u3949-THCV displayed a slight inverse agonism at CB1 receptors, which was confirmed in experiments of cyclic AMP assay in hCB1-CHO cells. At CB2 receptors, we found that \u3949-THCV can behave as a partial agonist when the measured response is inhibition of forskolin-induced stimulation of cyclic AMP production in hCB2-CHO cells or stimulation of [35S]GTP\u3b3S binding to membranes obtained either from hCB2-CHO cells or from mouse spleen membranes. No such effect was displayed by \u3949-THCV in untransfected CHO cells, pertussis toxin (PTX)-treated hCB2-CHO cells or CB2 -/- mouse spleen membranes. In collaboration with Dr. Barbara Costa and Dr. Dino Maione, we also showed that \u3949-THCV shares the ability of established selective CB2 receptor agonist to reduce signs of inflammation and inflammatory pain (Guindon, Hohmann 2008). These experiments were performed on in vivo models of \u3bb-carrageenan-induced oedema and thermal hyperalgesia, and formalin-induced nociception. In the second investigation we brought further evidences that \u3949-THCV is a partial agonist at CB2 receptors. In detail, we applied a protocol to hCB2-CHO cells in order to convert the selective CB2 receptor antagonist/inverse agonist, AM630, into an apparent neutral antagonist. In these experimental conditions, we found that \u3949-THCV still behaves as a CB2 receptor agonist and is antagonized by AM630 in experiments of cyclic AMP assay. Additional tests were also conducted to better understand the pharmacology of the ligand, AM630, at CB2 receptors. In the third study, we investigated the effect of CBD at serotonin type 1A (5-HT1A) autoreceptors. This research was based on previous in vivo findings showing that CBD-induced anti-emetic and anti-nausea effects were mediated by somatodendritic 5-HT1A autoreceptors located in the raphe nuclei (Rock et al. 2009, Parker et al. 2010). Experiments of [35S]GTP\u3b3S binding conducted in rat brainstem membranes revealed that CBD, in a bell-shaped manner, is able to enhance the dose-response curve of the selective 5-HT1A receptor agonist, DPAT. In addition, our results suggest that CBD does not interact directly with 5-HT1A receptors, and that CBD-mediated DPAT dose-response curve enhancement might implicate the involvement of an other receptor

The MICE electron muon ranger: a fundamental step towards a neutrino factory.

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