186 research outputs found

    On the application of optical forward-scattering to bacterial identification in an automated clinical analysis perspective

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    The Optical Forward Scattering (OFS) technique can be used to identify pathogens by direct observation of bacteria colonies growing on a culture plate. The identification is based on the acquisition of scattering images from isolated colonies and their subsequent comparison with reference images acquired from known bacteria. The technique has been mainly studied for the identification of pathogens in the food-safety field. This paper focuses on the possibility of extending the applicability of the technique to the field of clinical laboratory automation. This scenario requires that the paradigm of image acquisition at fixed colony-dimension, well established in the food-safety applications, should be substituted by an acquisition at fixed incubation time. As a consequence, the scatterometer must be adjustable in real-time for adapting to the actual features of the bacterial colony. The paper describes an OFS system prototype qualified by the possibility to tune both the laser beam diameter and the acquisition camera field of view. Preliminary experiments on bacteria cultures from pathogens causing infections of the urinary tract show that the proposed approach is promising for the development of an automated bacteria identification station. The new OFS approach also involves an alternative method for building a reference image database for subsequent image analysis

    Ge-Doped microstructured multicorefiber for customizable supercontinuum generation

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    Supercontinuum generation in a multicore fiber in which several uncoupled cores were doped with dissimilar concentrations of germanium was studied experimentally. Germanium doping provided control over the separation between the zero-dispersion wavelength and the 1064-nm wavelength of a Q-switched Nd:YAG pump laser. Supercontinua generated independently in each core of the same piece of fiber displayed clear and repeatable differences due to the influence of germanium doping on refractive index and four-wave mixing. The spectral evolution of the subnanosecond pump pulses injected into the different cores was accurately reproduced by numerical simulations

    β3 human papillomavirus species share several biological properties with high risk mucosal types

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    β human papillomaviruses (HPV) are subdivided into five species and are abundantly detected in the skin, in particular the β1 and β2 species. Therefore, β HPV types are considered to have a cutaneous tropism. However, several recent studies have described the presence of β HPV also in the mucosal epithelia at different anatomical sites. In particular, β3 HPV types are more prevalent in certain mucosal epithelia rather than in the cutaneous tissues. Studies in different experimental models have also highlighted that β3 HPV49 share functional similarities with the mucosal high-risk (HR) HPV16. However, with the exclusion of HPV49, very little is known about the biology of the other known β3 HPV types (75, 76 and 115). The aim of this thesis was the characterization of the biological properties of E6 and E7 of all known β3 HPV types, in relation to their interaction with key cellular pathways such as pRb, p53 and hTERT. Similar to what was previously showed for HPV49 E6/E7, HPV75 and HPV76 E6 and E7, but not HPV115 E6 and E7, efficiently cooperate in the immortalization/extension of lifespan of human foreskin keratinocytes (HFKs). In detail, HPV49, 75 and 76 E6/E7 cause the accumulation of the phosphorylated form of pRb, leading to the release of the E2F factor and unscheduled S-phase entry. As observed for HR HPV16, cell cycle deregulation mediated by β3 HPV onco-proteins leads to p16INK4a accumulation, while no p16INK4a was detected in β2 HPV38 E6/E7 HFKs. Similarly to HPV49 E6, HPV75 and 76 E6s degrade p53 via an E6AP/proteasome-mediated mechanism. Mutation in HPV76 E6 amino-acids that correspond to HPV16 E6 amino-acids involved in the formation of the E6/E6AP/p53 ternary complex results in the failed immortalization of HFKs. All the β3 HPV types, with the exception of HPV115, induce the up-regulation of hTERT expression, another important step in cellular transformation. Comparative analysis of cellular gene expression pattern of HFKs expressing E6 and E7 from HR HPV16, β3 HPV types and β2 HPV38 further highlights the functional similarities of HR HPV16 and β3 HPV49, 75, 76. The expression profiles of these four HPV HFKs show some similarities and diverge substantially from β3 HPV115 E6/E7 and β2 HPV38 E6/E7 HFKs. In conclusion, the data show that β3 HPV types share some similarities with HR HPV types and pave the way to additional studies aiming to evaluate their tissue tropism and their role in human pathologies

    Diphosphorylation of myosin light chain in smooth muscle cells in culture Possible involvement of protein kinase C

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    AbstractProstaglandin (PG) F2α (30 μM) stimulated both monophosphorylation and diphosphorylation of myosin light chain (MLC) in a smooth muscle cell line (SM-3). The diphosphorylation was significantly decreased by treatment with the protein kinase C inhibitor staurosporine (30 nM, 30 min) from 20.1% of total MLC to 4.5%. The protein kinase C down-regulation treatment of SM-3 cells with phorbol dibutyrate suppressed to 8.7% the MLC diphosphorylation activity in the SM-3 cells. This down-regulation treatment had little effect on the monophosphorylation. We propose that the MLC diphosphorylation in PGF2α-stimulated SM-3 cells in culture may be regulated through mechanisms sensitive to protein kinase C

    Nonlinear polarization dynamics of Kerr beam self-cleaning in a GRIN multimode optical fiber

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    We experimentally study polarization dynamics of Kerr beam self-cleaning in a graded-index multimode optical fiber. We show that spatial beam cleaning is accompanied by nonlinear polarization rotation, and a substantial increase of the degree of linear polarization.Comment: 5 pages, 6 figure

    Efficiency of dispersive wave generation in dual concentric core microstructured fiber

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    We describe the generation of powerful dispersive waves that are observed when pumping a dual concentric core microstructured fiber by means of a sub-nanosecond laser emitting at the wavelength of~1064 nm. The presence of three zeros in the dispersion curve, their spectral separation from the pump wavelength, and the complex dynamics of solitons originated by the pump pulse break-up, all contribute to boost the amplitude of the dispersive wave on the long-wavelength side of the pump. The measured conversion efficiency towards the dispersive wave at 1548 nm is as high as 50%. Our experimental analysis of the output spectra is completed by the acquisition of the time delays of the different spectral components. Numerical simulations and an analytical perturbative analysis identify the central wavelength of the red-shifted pump solitons and the dispersion profile of the fiber as the key parameters for determining the efficiency of the dispersive wave generation process.Comment: 11 pages, 12 figure

    Chromatic confocal setup for displacement measurement using a supercontinuum light source

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    Chromatic confocal microscopy is a technique to measure distances by analyzing the spectrum of the light reflected by a sample. The key element of the confocal setup is a dispersive lens, which focuses different wavelengths at different distances from the lens. In this paper,a novel setup realized with a supercontinuum light source and a spatial filter composed by reflective elements is described.The supercontinuum source is implemented by injecting high power pulses from a microchip laser into a Ge-doped microstructured optical fiber. The usage of metallic parabolic mirrors, for the focusing and collimation required in the spatial filter, lets the dispersive lens be the only dispersive element of the confocal setup and improves the efficiency of the spatial filter itself. A silicon-based spectrometer is used for the acquisition of the spectra, which are normalized and Gaussian-fitted before extracting the displacement information. A complete calibration is performed, and the set of wavelengths from 500 nm to 900 nm can be mapped into a280 um measuring range. The obtained relativ eaccuracy of 0.36% shows an enhancement of almost one order of magnitude when compared to other supercontinuum-based confocal systems

    Broadband optical supercontinuum generation in a long cavity fibre laser

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    We describe optical supercontinuum generation in an actively mode-locked fibre ring laser using a pulsed mode-locking technique. Recirculation of a section of the continuum facilitated spectral broadening

    Ge-Doped microstructured multicorefiber for customizable supercontinuum generation

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    Supercontinuum generation in a multicore fiber in which several uncoupled cores were doped with dissimilar concentrations of germanium was studied experimentally. Germanium doping provided control over the separation between the zero-dispersion wavelength and the 1064-nm wavelength of a Q-switched Nd:YAG pump laser. Supercontinua generated independently in each core of the same piece of fiber displayed clear and repeatable differences due to the influence of germanium doping on refractive index and four-wave mixing. The spectral evolution of the subnanosecond pump pulses injected into the different cores was accurately reproduced by numerical simulations

    Using the Optical Mouse Sensor as a Two-Euro Counterfeit Coin Detector

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    In this paper, the sensor of an optical mouse is presented as a counterfeit coin detector applied to the two-Euro case. The detection process is based on the short distance image acquisition capabilities of the optical mouse sensor where partial images of the coin under analysis are compared with some partial reference coin images for matching. Results show that, using only the vision sense, the counterfeit acceptance and rejection rates are very similar to those of a trained user and better than those of an untrained user
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