945 research outputs found

    An original image slicer designed for Integral Field Spectroscopy with NIRSpec/JSWT

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    Integral Field Spectroscopy (IFS) provides a spectrum simultaneously for each spatial sample of an extended, two-dimensional field. It consists of an Integral Field Unit (IFU) which slices and re-arranges the initial field along the entrance slit of a spectrograph. This article presents an original design of IFU based on the advanced image slicer concept. To reduce optical aberrations, pupil and slit mirrors are disposed in a fan-shaped configuration that means that angles between incident and reflected beams on each elements are minimized. The fan-shaped image slicer improves image quality in terms of wavefront error by a factor 2 comparing with classical image slicer and, furthermore it guaranties a negligible level of differential aberration in the field. As an exemple, we are presenting the design LAM used for its proposal at the NIRSPEC/IFU invitation of tender.Comment: Submitted to Optical Engineerin

    Time Calibration of TileCal Modules with Cosmic Muons

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    A method to synchronize TileCal readout in time using cosmic muons has been developed. It is based on the comparison between the expected time of flight of muons crossing TileCal cells and the measured time. The method has been applied to cosmic data from September and October of 2007, when different sub-detectors of ATLAS were integrated during the Milestone Weeks. The resolution reached with this method is better than 0.7 ns when the statistical error is not the main contribution to the uncertainty

    Total Prompt Energy Release in the Neutron-Induced Fission of 235-U, 238-U, and 239-Pu

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    This study addresses, for the first time, the total prompt energy release and its components for the fission of 235-U, 238-U, and 239-Pu as a function of the kinetic energy of the neutron inducing the fission. The components are extracted from experimental measurements, where they exist, together with model-dependent calculation, interpolation, and extrapolation. While the components display clear dependencies upon the incident neutron energy, their sums display only weak, yet definite, energy dependencies. Also addressed is the total prompt energy deposition in fission for the same three systems. Results are presented in equation form. New measurements are recommended as a consequence of this study.Comment: Accepted for publication in Nuclear Physics

    Modeling a Slicer Mirror Using Zemax User-Defined Surface

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    A slicer mirror is a complex surface composed by many tilted and decentered mirrors sub-surfaces. The major difficulty to model such a complex surface is the large number of parameters used to define it. The Zemax's multi-configuration mode is usually used to specify each parameters (tilts, curvatures, decenters) for each mirror sub-surface which are then considered independently. Otherwise making use of the User-Defined Surface (UDS-DLL) Zemax capability, we are able to consider the set of sub-surfaces as a whole surface. In this paper, we present such a UDS-DLL tool comparing its performance with those of the classical multi-configuration mode. In particular, we explore the use of UDS-DLL to investigate the cross-talk due to the diffraction on the slicer array mirrors which has been a burden task when using multi-configuration mode.Comment: Submitted to the proceedings of the Durham Integral Field Spectroscopy Workshop July 4th-8th 200

    An original image slicer designed for Integral Field Spectroscopy with NIRSpec/JSWT

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    Submitted to Optical Engineering.Integral Field Spectroscopy (IFS) provides a spectrum simultaneously for each spatial sample of an extended, two-dimensional field. It consists of an Integral Field Unit (IFU) which slices and re-arranges the initial field along the entrance slit of a spectrograph. This article presents an original design of IFU based on the advanced image slicer concept. To reduce optical aberrations, pupil and slit mirrors are disposed in a fan-shaped configuration that means that angles between incident and reflected beams on each elements are minimized. The fan-shaped image slicer improves image quality in terms of wavefront error by a factor 2 comparing with classical image slicer and, furthermore it guaranties a negligible level of differential aberration in the field. As an exemple, we are presenting the design LAM used for its proposal at the NIRSPEC/IFU invitation of tender

    Peptides in Receptor-Mediated Radiotherapy: From Design to the Clinical Application in Cancers

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    Short peptides can show high affinity for specific receptors overexpressed on tumor cells. Some of these are already used in cancerology as diagnostic tools and others are in clinical trials for therapeutic applications. Therefore, peptides exhibit great potential as a diagnostic tool but also as an alternative or an additional antitumoral approach upon the covalent attachment of a therapeutic moiety such as a radionuclide or a cytotoxic drug. The chemistry offers flexibility to graft onto the targeting-peptide either fluorine or iodine directly, or metallic radionuclides through appropriate chelating agent. Since short peptides are straightforward to synthesize, there is an opportunity to further improve existing peptides or to design new ones for clinical applications. However, several considerations have to be taken into account to optimize the recognition properties of the targeting-peptide to its receptor, to improve its stability in the biological fluids and its residence in the body, or to increase its overall therapeutic effect. In this review, we highlight the different aspects which need to be considered for the development of an efficient peptide receptor-mediated radionuclide therapy in different neoplasms

    Conductive and convective heat transfer in fluid flows between differentially heated and rotating cylinders

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    The flow of fluid confined between a heated rotating cylinder and a cooled stationary cylinder is a canonical experiment for the study of heat transfer in engineering. The theoretical treatment of this system is greatly simplified if the cylinders are assumed to be of infinite length or periodic in the axial direction, in which cases heat transfer occurs only through conduction as in a solid. We here investigate numerically heat transfer and the onset of turbulence in such flows by using both periodic and no-slip boundary conditions in the axial direction. We obtain a simple linear criterion that determines whether the infinite-cylinder assumption can be employed. The curvature of the cylinders enters this linear relationship through the slope and additive constant. For a given length-to-gap aspect ratio there is a critical Rayleigh number beyond which the laminar flow in the finite system is convective and so the behaviour is entirely different from the periodic case. The criterion does not depend on the Prandtl number and appears quite robust with respect to the Reynolds number. In particular, it continues to work reasonably in the turbulent regime.Comment: 25 pages, 9 figure

    Spallation Residues in the Reaction 56Fe + p at 0.3, 0.5, 0.75, 1.0 and 1.5 A GeV

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    The spallation residues produced in the bombardment of 56}Fe at 1.5, 1.0, 0.75, 0.5 and 0.3 A GeV on a liquid-hydrogen target have been measured using the reverse kinematics technique and the Fragment Separator at GSI (Darmstadt). This technique has permitted the full identification in charge and mass of all isotopes produced with cross-sections larger than 10^{-2} mb down to Z=8. Their individual production cross-sections and recoil velocities at the five energies are presented. Production cross-sections are compared to previously existing data and to empirical parametric formulas, often used in cosmic-ray astrophysics. The experimental data are also extensively compared to different combinations of intra-nuclear cascade and de-excitation models. It is shown that the yields of the lightest isotopes cannot be accounted for by standard evaporation models. The GEMINI model, which includes an asymmetric fission decay mode, gives an overall good agreement with the data. These experimental data can be directly used for the estimation of composition modifications and damages in materials containing iron in spallation sources. They are also useful for improving high precision cosmic-ray measurements.Comment: Submited to Phys. Rev. C (10/2006

    'Whatever it takes' to change beliefs: Evidence from Twitter

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    Resumen de la comunicación[EN] The sovereign debt literature emphasizes the possibility of avoiding a selffulfilling default crisis if markets anticipate the central bank to act as the lender of last resort. Motivated by the events of summer 2012 in the eurozone, this paper investigates the extent to which changes in beliefs about an intervention of the European Central Bank (ECB) explain the sudden reduction of government bond yields for the so-called PIIGS countries. To proxy beliefs, we study Twitter data from July to September 2012 and extract beliefs using machine learning techniques. Our results are consistent with the theoretical prediction that a central bank, which credibly commits to an intervention, can restore the fundamental "good" equilibrium.Stiefel, M.; Vivès, R. (2018). 'Whatever it takes' to change beliefs: Evidence from Twitter. En 2nd International Conference on Advanced Reserach Methods and Analytics (CARMA 2018). Editorial Universitat Politècnica de València. 254-254. https://doi.org/10.4995/CARMA2018.2018.8328OCS25425

    Measurement of residual nucleus cross sections and recoil energies in p + Fe collisions at 300, 500, 750, 1000 and 1500 MeV

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    The production of residual nuclei in p + Fe collisions has been measured at GSI on the FRS facility by means of the reverse kinematic techniques at 300, 500, 750, 1000 and 1500 MeV/A. The cross-sections larger than 0.01 mb of all isotopes with Z larger than 8 have been obtained. Velocity distributions were also measured. Comparisons to models describing spallation reactions and some empirical formulae often used in astrophysics are presented. These data are directly used to calculate impurety production and DPAs in a thin window as foreseen in spallation sources or accelerator-driven systems
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