Effect of corrosion degradation on failure mechanisms of aluminium/steel clinched joints

The effect of corrosion phenomena in critical environmental conditions on the mechanical performance of steel/aluminium hybrid joints, obtained by clinching technique, was studied by ageing in salt spray environment. The investigation was carried out on asymmetrical joints with total thickness of 2.5 mm. The joint strength at varying ageing time was determined by means of single lap shear tests.The experimental results have shown that corrosion degradation phenomena significantly affect the performance and failure mechanisms of the joints, causing premature failure of the joint at very low stress level.Moreover, it was observed that the joint geometry characterized by thicker aluminium foil, had good durability properties showing acceptable mechanical properties even at long ageing times. The fracture modes have been analysed in all the above-mentioned conditions and a failure map, at increasing ageing time, for the two joint geometries has been proposed. Keywords: Clinched joints, Durability, Corrosion, Single lap shear test, Failure ma

Assessment of ageing effect on the mechanical behaviour of steel/aluminium self-piercing riveted joint

Self-piercing riveting (SPR) is a new performing technology able to joint several kinds of metal and non-metal supports together. The combined effect of joint configuration and environmental conditions could have detrimental effect on the ageing effect on mechanical behaviour of dissimilar metal SPR joints. The joining of dissimilar materials, such as steel and aluminium, realized by self-piercing riveting (SPR) technique was studied to evaluate the ageing effects on its mechanical behaviour in critical environmental conditions. The investigation was carried out on symmetrical or unsymmetrical joints at varying total thicknesses (i.e. 2.0, 2.5 and 3.0 mm). The joint resistance was determined by single-lap shear tests. A design of experiment (DoE) has been performed by using Minitab® followed by the statistical analysis (ANOVA) of the experimental data. Long-term ageing tests in salt spray environment were performed to evaluate the durability of the mechanical joint. The experimental results evidenced that the corrosion degradation phenomena influenced significantly both the performance and failure mechanisms of the joints; also, the joint configuration is a significant factor for the corrosion effect. In the salt spray, the aluminium sheet undergoes a noticeable degradation due to galvanic Al/Fe corrosion. The set characterized by thinner aluminium sheet evidenced a gradual reduction of the mechanical strength with increasing ageing time due to the prevalence of thinning induced by aluminium corrosion. Instead, for S10-A15 samples (characterized by a thicker thickness of aluminium sheet) during the first 7 weeks, stable mechanical performances were observed. The experimental results evidenced that the corrosion degradation phenomena influence significantly both performances and failure mechanisms of SPR joints. Furthermore, the durability of the SPR joint is strongly affected by the joint configuration, and the best results were observed in the unsymmetrical joint with thicker aluminium sheet

Determination of the Jet Energy Scale at the Collider Detector at Fermilab

A precise determination of the energy scale of jets at the Collider Detector at Fermilab at the Tevatron $p\bar{p}$ collider is described. Jets are used in many analyses to estimate the energies of partons resulting from the underlying physics process. Several correction factors are developed to estimate the original parton energy from the observed jet energy in the calorimeter. The jet energy response is compared between data and Monte Carlo simulation for various physics processes, and systematic uncertainties on the jet energy scale are determined. For jets with transverse momenta above 50 GeV the jet energy scale is determined with a 3% systematic uncertainty

Endoscopic ultrasound-guided ablation of solid pancreatic lesions: A systematic review of early outcomes with pooled analysis

Contains fulltext : 252157.pdf (Publisher’s version ) (Open Access)BACKGROUND: Endoscopic ultrasound-guided radiofrequency ablation (EUS-RFA) is emerging as a complementary therapeutic approach for pancreatic solid masses. However, results of published data are difficult to interpret because of a retrospective design and small sample size. AIM: To systematically review data on EUS-RFA for solid lesions and to pool the results of the different experiences in order to provide more consistent evidence in terms of safety and efficacy. METHODS: A comprehensive systematic literature search on the main databases was performed to identify articles in which patients with pancreatic solid lesions underwent EUS-RFA. The primary outcomes were procedure-related adverse events (AEs) and mortality. Secondary outcomes were the technical success rate and the effects on primary tumor growth. Statistical analyses were performed using Stata version 14.0. RESULTS: In total, 14 studies were included, with 120 patients undergoing 153 ablations of 129 solid pancreatic lesions. The STARmed technology was used in seven studies, the Habib system in six studies, and the HybridTherm probe in one study. The pooled technical success rate was 99.0% (I (2): 25.82%). The pooled overall AE rate was 8.0% (I (2): 11.46%). Excluding mild AEs, the pooled rates of serious AEs was 1.0% (I (2): 0%). No mortality related to the procedure was reported. CONCLUSION: The present pooled analysis confirms the safety and feasibility of EUS-RFA

Precision measurements of the top quark mass from the Tevatron in the pre-LHC era

The top quark is the heaviest of the six quarks of the Standard Model. Precise knowledge of its mass is important for imposing constraints on a number of physics processes, including interactions of the as yet unobserved Higgs boson. The Higgs boson is the only missing particle of the Standard Model, central to the electroweak symmetry breaking mechanism and generation of particle masses. In this Review, experimental measurements of the top quark mass accomplished at the Tevatron, a proton-antiproton collider located at the Fermi National Accelerator Laboratory, are described. Topologies of top quark events and methods used to separate signal events from background sources are discussed. Data analysis techniques used to extract information about the top mass value are reviewed. The combination of several most precise measurements performed with the two Tevatron particle detectors, CDF and \D0, yields a value of \Mt = 173.2 \pm 0.9 GeV/$c^2$.Comment: This version contains the most up-to-date top quark mass averag

Gastric peroral endoscopic pyloromyotomy for refractory gastroparesis: a systematic review of early outcomes with pooled analysis

Background and Aims: Gastroparesis (GP) is a chronic debilitating condition. Prior pyloric-targeted procedures are either invasive or have questionable efficacy. Gastric peroral pyloromyotomy (G-POEM) has been proposed as a minimally invasive approach. We performed a pooled analysis to evaluate the efficacy and safety of G-POEM for GP. Methods: Electronic databases (Medline, Scopus, EMBASE) were searched up to January 2019. Studies including patients who underwent G-POEM for GP were eligible. Procedural, clinical, and safety outcomes were assessed by pooling data with a random- or fixed-effect model according to the degree of heterogeneity to obtain a proportion with a 95% confidence interval. Results: Ten studies were eligible for inclusion (292 patients), and 2 of the 10 studies were prospective. Seven studies were performed in the United States, 2 in France, and 1 in China. Endoscopic pyloromyotomy was feasible in all patients. Significant symptomatic improvement was achieved after 83.9% of procedures (mean follow-up, 7.8 ± 5.5 months). When comparing the mean values of pre- and postprocedural scintigraphic evolution, there was a significant decrease of the residual percentage at 2 and 4 hours. The overall adverse events rate was 6.8%. Conclusions: G-POEM appears to be a promising approach for GP in terms of safety and efficacy outcomes in the short term

Inclusive Search for Anomalous Production of High-pT Like-Sign Lepton Pairs in Proton-Antiproton Collisions at sqrt{s}=1.8 TeV

We report on a search for anomalous production of events with at least two charged, isolated, like-sign leptons with pT > 11 GeV/c using a 107 pb^-1 sample of 1.8 TeV ppbar collisions collected by the CDF detector. We define a signal region containing low background from Standard Model processes. To avoid bias, we fix the final cuts before examining the event yield in the signal region using control regions to test the Monte Carlo predictions. We observe no events in the signal region, consistent with an expectation of 0.63^(+0.84)_(-0.07) events. We present 95% confidence level limits on new physics processes in both a signature-based context as well as within a representative minimal supergravity (tanbeta = 3) model.Comment: 15 pages, 4 figures. Minor textual changes, cosmetic improvements to figures and updated and expanded reference

Search for Narrow Diphoton Resonances and for gamma-gamma+W/Z Signatures in p\bar p Collisions at sqrt(s)=1.8 TeV

We present results of searches for diphoton resonances produced both inclusively and also in association with a vector boson (W or Z) using 100 pb^{-1} of p\bar p collisions using the CDF detector. We set upper limits on the product of cross section times branching ratio for both p\bar p\to\gamma\gamma + X and p\bar p\to\gamma\gamma + W/Z. Comparing the inclusive production to the expectations from heavy sgoldstinos we derive limits on the supersymmetry-breaking scale sqrt{F} in the TeV range, depending on the sgoldstino mass and the choice of other parameters. Also, using a NLO prediction for the associated production of a Higgs boson with a W or Z boson, we set an upper limit on the branching ratio for H\to\gamma\gamma. Finally, we set a lower limit on the mass of a `bosophilic' Higgs boson (e.g. one which couples only to \gamma, W, and Z$ bosons with standard model couplings) of 82 GeV/c^2 at 95% confidence level.Comment: 30 pages, 11 figure

Measurement of the Helicity Fractions of W Bosons from Top Quark Decays Using Fully Reconstructed top-antitop Events with CDF II

We present a measurement of the fractions F_0 and F_+ of longitudinally polarized and right-handed W bosons in top quark decays using data collected with the CDF II detector. The data set used in the analysis corresponds to an integrated luminosity of approximately 318 pb -1. We select ttbar candidate events with one lepton, at least four jets, and missing transverse energy. Our helicity measurement uses the decay angle theta*, which is defined as the angle between the momentum of the charged lepton in the W boson rest frame and the W momentum in the top quark rest frame. The cos(theta*) distribution in the data is determined by full kinematic reconstruction of the ttbar candidates. We find F_0 = 0.85 +0.15 -0.22 (stat) +- 0.06 (syst) and F_+ = 0.05 +0.11 -0.05 (stat) +- 0.03 (syst), which is consistent with the standard model prediction. We set an upper limit on the fraction of right-handed W bosons of F_+ < 0.26 at the 95% confidence level.Comment: 11 pages, 2 figures, submitted to Phys. Rev.

Search for the Higgs boson in events with missing transverse energy and b quark jets produced in proton-antiproton collisions at s**(1/2)=1.96 TeV

We search for the standard model Higgs boson produced in association with an electroweak vector boson in events with no identified charged leptons, large imbalance in transverse momentum, and two jets where at least one contains a secondary vertex consistent with the decay of b hadrons. We use ~1 fb-1 integrated luminosity of proton-antiproton collisions at s**(1/2)=1.96 TeV recorded by the CDF II experiment at the Tevatron. We find 268 (16) single (double) b-tagged candidate events, where 248 +/- 43 (14.4 +/- 2.7) are expected from standard model background processes. We place 95% confidence level upper limits on the Higgs boson production cross section for several Higgs boson masses ranging from 110 GeV/c2 to 140 GeV/c2. For a mass of 115 GeV/c2 the observed (expected) limit is 20.4 (14.2) times the standard model prediction.Comment: 8 pages, 2 figures, submitted to Phys. Rev. Let