2,986 research outputs found

    Measuring Propagation Speed of Coulomb Fields

    Get PDF
    The problem of gravity propagation has been subject of discussion for quite a long time: Newton, Laplace and, in relatively more modern times, Eddington pointed out that, if gravity propagated with finite velocity, planets motion around the sun would become unstable due to a torque originating from time lag of the gravitational interactions. Such an odd behavior can be found also in electromagnetism, when one computes the propagation of the electric fields generated by a set of uniformly moving charges. As a matter of fact the Li\'enard-Weichert retarded potential leads to a formula indistinguishable from the one obtained assuming that the electric field propagates with infinite velocity. Feyman explanation for this apparent paradox was based on the fact that uniform motions last indefinitely. To verify such an explanation, we performed an experiment to measure the time/space evolution of the electric field generated by an uniformely moving electron beam. The results we obtain on such a finite lifetime kinematical state seem compatible with an electric field rigidly carried by the beam itself.Comment: 23 pages, 15 figure

    Beam test of scintillation tiles with MPPC readout

    Get PDF
    This paper describes measurements made using counters composed of a small (3 by 3 by 0.5 cm3) scintillation tile coupled to a Multi-Photon Pixel Counter (MPPC) produced by Hamamatsu and exposed to an electron beam at the Beam Test Facility in Frascati. We show our first results for charge spectra and efficiency, and a very preliminary measurement of device linearity

    A new concept for streamer quenching in resistive plate chambers

    Get PDF
    In this paper we propose a new concept for streamer quenching in Resistive Plate Chambers (RPCs). In our approach, the multiplication process is quenched by the appropriate design of a mechanical structure inserted between the two resistive electrodes. We show that stable performance is achieved with binary gas mixtures based on argon and a small fraction of isobutane. Fluorocarbons, deemed responsible for the degradation of the electrode inner surface of RPC detectors, are thus fully eliminated from the gas mixture. This design {also resulted} in a simplified assembly procedure. Preliminary results obtained with a few prototypes of ``Mechanically Quenched RPCs'' and some prospects for future developments are discussed

    Biocompatibility, Inflammatory Response, and Recannalization Characteristics of Nonradioactive Resin Microspheres: Histological Findings

    Get PDF
    Intra-arterial radiotherapy with yttrium-90 microspheres (radioembolization) is a therapeutic procedure exclusively applied to the liver that allows the direct delivery of high-dose radiation to liver tumors, by means of endovascular catheters, selectively placed within the tumor vasculature. The aim of the study was to describe the distribution of spheres within the precapillaries, inflammatory response, and recannalization characteristics after embolization with nonradioactive resin microspheres in the kidney and liver. We performed a partial embolization of the liver and kidney vessels in nine white pigs. The left renal and left hepatic arteries were catheterized and filled with nonradioactive resin microspheres. Embolization was defined as the initiation of near-stasis of blood flow, rather than total occlusion of the vessels. The hepatic circulation was not isolated so that the effects of reflux of microspheres into stomach could be observed. Animals were sacrificed at 48 h, 4 weeks, and 8 weeks, and tissue samples from the kidney, liver, lung, and stomach evaluated. Microscopic evaluation revealed clusters of 10–30 microspheres (15–30 μm in diameter) in the small vessels of the kidney (the arciform arteries, vasa recti, and glomerular afferent vessels) and liver. Aggregates were associated with focal ischemia and mild vascular wall damage. Occlusion of the small vessels was associated with a mild perivascular inflammatory reaction. After filling of the left hepatic artery with microspheres, there was some evidence of arteriovenous shunting into the lungs, and one case of cholecystitis and one case of marked gastritis and ulceration at the site of arterial occlusion due to the presence of clusters of microspheres. Beyond 48 h, microspheres were progressively integrated into the vascular wall by phagocytosis and the lumen recannalized. Eight-week evaluation found that the perivascular inflammatory reaction was mild. Liver cell damage, bile duct injury, and portal space fibrosis were not observed. In conclusion, resin microspheres (15–30 μm diameter) trigger virtually no inflammatory response in target tissues (liver and kidney). Clusters rather than individual microspheres were associated with a mild to moderate perivascular inflammatory reaction. There was no evidence of either a prolonged inflammatory reaction or fibrosis in the liver parenchyma following recannalization

    Neutrophil-to-lymphocyte ratio predicts survival in European patients with hepatocellular carcinoma administered sorafenib

    Get PDF
    Neutrophil-to-lymphocyte ratio (NLR) is considered a prognostic factor in patients with hepatocellular carcinoma (HCC). Our aim is to investigate the prognostic significance of NLR in patients with HCC treated with sorafenib. Results Median follow-up time was 7 months. Patients were mostly in the intermediate (27.3%) or advanced (72.7%) BCLC stages, 38.6% had vascular invasion and 27.5% extrahepatic disease. A large proportion (38.9%) had been previously treated with TACE. Liver function was preserved: 65.8% were classed as Child A. Median overall survival was 7.7 months (95% CI: 5.8–9.6). In univariate analysis, vascular invasion (P = 0.004), ECOG-PS = 1 (P < 0.001), high bilirubin (P < 0.001), clinical ascites (P = 0.036), BCLC stage (P = 0.004), no previous TACE (P = 0.041) and NRL = 2.3 (P = 0.005) were predictors of poor survival. Skin toxicity (P = 0.039) or hypertension (P = 0.033) during treatment were related to better survival. In multivariate analysis NLR = 2.3 [HR 1.72 (95% CI: 1.03–2.71)], hyperbilirubinemia [HR 3.42 (95% CI: 1.87–6.25)] and ECOG-PS = 1 [HR 1.97 (95% CI: 1.19–3.26)] were found as independent indicators of poor overall survival. Dermatologic adverse effects were an indicator of good overall survival [HR 0.59 (95% CI: 0.38–0.92)]. Material and Methods One hundred and fifty-four consecutive HCC patients treated with sorafenib in four different Spanish hospitals between August 2005 and October 2013 were analysed. Clinical, laboratory, and tumour features were obtained. Survival was calculated from the moment sorafenib treatment was initiated. Log-rank and Cox regression were used to analyse the ability of NLR to predict survival. Conclusions NLR is an independent prognostic indicator for overall survival in HCC patients treated with sorafenib

    Test of large area glass RPCs at the DA Phi NE Test Beam Facility (BTF)

    Get PDF
    Abstract The CaPiRe program has been started to develop a new detector design, in order to produce large areas of glass Resistive Plate Chambers (RPC) detectors, overcoming the previous limitations. As a first step we produced our glass RPC detectors ( 1 m 2 ) at General Tecnica exploiting their standard procedures, materials and production techniques simply using 2 mm glass electrodes instead of the bakelite ones. A set of RPC was produced by using pre-coated (silk screen printed) electrodes, while others were produced with the standard graphite coating. All the detectors, together with four old Glass RPC acting as reference, were tested at the DA Φ NE Test Beam Facility with 500 MeV electrons in order to study the efficiency in different positions inside the detectors (i.e. near spacers and edges) and to study the detector behavior as a function of the local particle rate

    Characterization and Performance of PADME's Cherenkov-Based Small-Angle Calorimeter

    Full text link
    The PADME experiment, at the Laboratori Nazionali di Frascati (LNF), in Italy, will search for invisible decays of the hypothetical dark photon via the process e+eγAe^+e^-\rightarrow \gamma A', where the AA' escapes detection. The dark photon mass range sensitivity in a first phase will be 1 to 24 MeV. We report here on measurement and simulation studies of the performance of the Small-Angle Calorimeter, a component of PADME's detector dedicated to rejecting 2- and 3-gamma backgrounds. The crucial requirement is a timing resolution of less than 200 ps, which is satisfied by the choice of PbF2_2 crystals and the newly released Hamamatsu R13478UV photomultiplier tubes (PMTs). We find a timing resolution of 81 ps (with double-peak separation resolution of 1.8 ns) and a single-crystal energy resolution of 5.7%/E\sqrt{E} with light yield of 2.07 photo-electrons per MeV, using 100 to 400 MeV electrons at the Beam Test Facility of LNF. We also propose the investigation of a two-PMT solution coupled to a single PbF2_2 crystal for higher-energy applications, which has potentially attractive features.Comment: 12 pages, 19 figures. v2: added section on radiation damage studie
    corecore