Nonlinear evolution of initially sine-like wedge acoustic waves

In this paper the nonlinear behaviour of antisymmetric wedge acoustic waves propagating along the tip of a sharp elastic wedge is investigated theoretically. The nonlinear evolution equation is derived taking into account geometrical-acoustics approximation for wedge waves. In contrast to the case of surface acoustic waves for which the quadratic nonlinearity dominates, the lowest order of nonlinearity in this equation is cubic. For arbitrary propagation distances, the numerical solution taking into account 1O interacting wave harmonics has been carried out. The results show that an initially sine-like antisymmetric wedge wave distorts to a wave of trapezoidal form propagating with changed phase velocity

Results of vascular resections during pancreatectomy from two European centres: an analysis of survival and disease-free survival explicative factors

AbstractObjectives. The object of our study was to report on the experience with vascular resections at pancreatectomy in two European specialist hepatopancreatobiliary centres and evaluate outcome and prognostic factors. Patients and methods. From 1989 to 2002, 45 patients (21 men, 24 women) underwent pancreatectomy for a pancreatic mass: Whipple's procedure (n= 33), total pancreatectomy (n= 10) or left splenopancreatectomy (n= 2), along with a vascular resection, i.e. venous (n= 39), arterial (n= 1) or venous + arterial (n= 5). Results. Operative mortality was nil, postoperative mortality was 2.2% (n= 1); 34 patients had an uneventful postoperative course. Reoperations were performed for portal vein thromobosis (n= 1), pancreatic leak (n= 1), gastric outlet syndrome (n= 1) and gastrointestinal bleeding (n= 1). In all, 43 patients had cancer on pathology examination, with retropancreatic invasion in 72% and lymph node extension in 62.8%. Resection was R0 in 21 cases. Vessel wall invasion was present in 13 cases and 19 had perivascular invasion. Disease-free survival (DFS) at 1, 2 and 3 years was 36.0%, 15.0% and 12.0%, respectively. Median DFS length was 8.7 months (95% CI: 7.2; 10.2). Overall survival rates were 56.6%, 28.9% and 19.2%, respectively. Median survival length was 14.2 months (95% CI: 9.8; 18.6). A multivariate analysis of prognostic variables identified tumour location (other than head of pancreas), neoadjuvant chemotherapy and advanced disease stage as adverse factors for DFS. Conclusion. Survival and DFS rates of these patients are comparable to those without vascular resection. Tumour localization, tumour stage, neoadjuvant treatment and tumour recurrence are explanatory variables of survival. Tumour localization, tumour stage and neoadjuvant treatment were explanatory variables for DFS. However, the type and extent of vascular resections as well as vessel wall invasion does not affect survival and DFS

Reaching activity in parietal area V6A of macaque: eye influence on arm activity or retinocentric coding of reaching movements?

Parietal area V6A contains neurons modulated by the direction of gaze as well as neurons able to code the direction of arm movement. The present study was aimed to disentangle the gaze effect from the effect of reaching activity upon single V6A neurons. To this purpose, we used a visuomotor task in which the direction of arm movement remained constant while the animal changed the direction of gaze. Gaze direction modulated reach-related activity in about two-thirds of tested neurons. In several cases, modulations were not due to the eye-position signal per se, the apparent eye-position modulation being just an epiphenomenon. The real modulating factor was the location of reaching target with respect to the point gazed by the animal, that is, the retinotopic coordinates towards which the action of reaching occurred. Comparison of neural discharge of the same cell during execution of foveated and non-foveated reaching movements, performed towards the same or different spatial locations, confirmed that in a part of V6A neurons reaching activity is coded retinocentrically. In other neurons, reaching activity is coded spatially, depending on the direction of reaching movement regardless of where the animal was looking at. The majority of V6A reaching neurons use a system that encompasses both of these reference frames. These results are in line with the view of a progressive visuomotor transformation in the dorsal visual stream, that changes the frame of reference from the retinocentric one, typically used by the visual system, to the arm-centred one, typically used by the motor system

Early in-hospital exposure to statins and outcome after intracerebral haemorrhage - Results from the Virtual International Stroke Trials Archive

Introduction Recent data suggest that statin use after intracerebral haemorrhage might be beneficial. However, data on the effects of early in-hospital statin exposure are lacking. Therefore, we sought to assess whether (1) early statin exposure during the acute phase after intracerebral haemorrhage and (2) early continuation of prevalent statin use are associated with favourable functional outcome. Patients and methods Data were obtained from the Virtual International Stroke Trials Archive. Patients were categorised according to use patterns of statins during this early in-hospital phase (continuation, discontinuation or new initiation of statins). Univariate and multivariable analyses were conducted to explore the association between early statin exposure and functional outcome. Results A total of 919 patients were included in the analysis. Early in-hospital statin exposure (n = 89, 9.7%) was associated with better functional outcome (modified Rankin Scale <= 3) compared with 790 patients without statin exposure before or early after the event (66% versus 47%, adjusted OR 2.1, 95% confidence interval 1.3-3.6). Compared with patients without exposure to statins before and early after the event, early continuation of statin therapy (n = 57) was associated with favourable functional outcome (adjusted odds ratio 2.6, 95% confidence interval 1.3-5.2). The association between early continuation of statins and outcome remained robust in sensitivity analyses restricted to patients able to take oral medication within 72 h and one-week survivors. Discussion It is possible that part of the observed associations are not due to a protective effect of statins but are confounded by indication bias. Conclusion Statin exposure and continuation of prevalent statin therapy early after intracerebral haemorrhage are associated with favourable functional outcome after 90 days

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters

Measurement of D*+/- meson production in jets from pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

This paper reports a measurement of D*+/- meson production in jets from proton-proton collisions at a center-of-mass energy of sqrt(s) = 7 TeV at the CERN Large Hadron Collider. The measurement is based on a data sample recorded with the ATLAS detector with an integrated luminosity of 0.30 pb^-1 for jets with transverse momentum between 25 and 70 GeV in the pseudorapidity range |eta| < 2.5. D*+/- mesons found in jets are fully reconstructed in the decay chain: D*+ -> D0pi+, D0 -> K-pi+, and its charge conjugate. The production rate is found to be N(D*+/-)/N(jet) = 0.025 +/- 0.001(stat.) +/- 0.004(syst.) for D*+/- mesons that carry a fraction z of the jet momentum in the range 0.3 < z < 1. Monte Carlo predictions fail to describe the data at small values of z, and this is most marked at low jet transverse momentum.Comment: 10 pages plus author list (22 pages total), 5 figures, 1 table, matches published version in Physical Review

Search for scalar top quark pair production in natural gauge mediated supersymmetry models with the ATLAS detector in pp collisions at sqrt(s) = 7 TeV

The results of a search for pair production of the lighter scalar partners of top quarks in 2.05 fb-1 of pp collisions at sqrt(s) =7 TeV using the ATLAS experiment at the LHC are reported. Scalar top quarks are searched for in events with two same flavour opposite-sign leptons (electrons or muons) with invariant mass consistent with the Z boson mass, large missing transverse momentum and jets in the final state. At least one of the jets is identified as originating from a b-quark. No excess over Standard Model expectations is found. The results are interpreted in the framework of R-parity conserving, gauge mediated Supersymmetry breaking `natural' scenarios, where the neutralino is the next-to-lightest supersymmetric particle. Scalar top quark masses up to 310 GeV are excluded for the lightest neutralino mass between 115 GeV and 230 GeV at 95% confidence level, reaching an exclusion of the scalar top quark mass of 330 GeV for the lightest neutralino mass of 190 GeV. Scalar top quark masses below 240 GeV are excluded for all values of the lightest neutralino mass above the Z boson mass.Comment: 7 pages plus author list (20 pages total), 4 figures, 1 table, matches published PLB versio