1,493 research outputs found
Central production via photon-photon fusion in proton-proton collisions with proton dissociation
We present a formalism which uses fluxes of equivalent photons including
transverse momenta of the intermediate photons. The formalism reminds the
familiar -factorization approach used, e.g., to study the two-photon
production of or pairs. The results of the new method are
compared with those obtained using the code LPAIR, and a good agreement is
obtained. The inclusion of the photon transverse momenta is necessary in
studies of correlation observables. We present distributions for the dimuon
invariant mass, transverse momentum of the muon pair and relative azimuthal
angle between muons separately for elastic-elastic, elastic-inelastic,
inelastic-elastic and inelastic-inelastic mechanisms. For typical experimental
cuts all mechanisms give similar contributions. The results are shown for
different sets of cuts relevant for the LHC experiments. The cross sections in
different regions of phase space depend on structure function in
different regions of and . A comment on is made.Comment: 24 pages, 36 figures, 2 table
Production of tt/mml:mover> pairs via fusion with photon transverse momenta and proton dissociation
12 pages, 11 figuresWe discuss the production of t t quark- antiquark pairs in proton- proton collisions via the fusion mechanism. We include topologies in which both protons stay intact or one or even both of them undergo dissociation. The calculations are performed within the k T - factorisation approach, including transverse momenta of intermediate photons. Photon uxes associated with inelastic ( dissociative) processes are calculated based on modern parameterisations of proton structure functions. We fi nd an integrated cross section of about 2.36 fb at p s = 13 TeV for all contributions ( without requirement of rapidity gap). The cross section for the fully elastic process is the smallest. Inelastic contributions are signi fi cantly reduced when a veto on outgoing jets is imposed. We present several di ff erential distributions in rapidity and transverse momenta of single t or t quarks/ antiquarks as well as distributions in invariant mass of both the t t and masses of dissociated systems. A few two- dimensional distributions are presented in addition.Peer reviewe
Reliable error estimation for Sobol' indices
International audienceIn the field of sensitivity analysis, Sobol’ indices are sensitivity measures widely used to assess the importance of inputs of a model to its output. The estimation of these indices is often performed trough Monte Carlo or quasi-Monte Carlo methods. A notable method is the replication procedure that estimates first-order indices at a reduced cost in terms of number of model evaluations. An inherent practical problem of this estimation is how to quantify the number of model evaluations needed to ensure that estimates satisfy a desired error tolerance. This paper addresses this challenge by proposing a reliable error bound for first-order and total effect Sobol’ indices. Starting from the integral formula of the indices, the error bound is defined in terms of the discrete Walsh coefficients of the different integrands.We propose a sequential estimation procedure of Sobol’ indices using the error bound as a stopping criterion. The sequential procedure combines Sobol’ sequences with either Saltelli’s strategy to estimate both first-order and total effect indices, or the replication procedure to estimate only first-order indices
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Antitumour activity of pembrolizumab in advanced mucosal melanoma: a post-hoc analysis of KEYNOTE-001, 002, 006.
BackgroundMucosal melanoma is an aggressive melanoma with poor prognosis. We assessed efficacy of pembrolizumab in patients with advanced mucosal melanoma in KEYNOTE-001 (NCT01295827), -002 (NCT01704287), and -006 (NCT01866319).MethodsPatients received pembrolizumab 2 mg/kg every 3 weeks (Q3W) or 10 mg/kg Q2W or Q3W. Response was assessed by independent central review per RECIST v1.1.Results1567 patients were treated and 84 (5%) had mucosal melanoma. Fifty-one of 84 were ipilimumab-naive. In patients with mucosal melanoma, the objective response rate (ORR) was 19% (95% CI 11-29%), with median duration of response (DOR) of 27.6 months (range 1.1 + to 27.6). Median progression-free survival (PFS) was 2.8 months (95% CI 2.7-2.8), with median overall survival (OS) of 11.3 months (7.7-16.6). ORR was 22% (95% CI 11-35%) and 15% (95% CI 5-32%) in ipilimumab-naive and ipilimumab-treated patients.ConclusionPembrolizumab provides durable antitumour activity in patients with advanced mucosal melanoma regardless of prior ipilimumab
Pulmonary embolism and 3-month outcomes in 4036 patients with venous thromboembolism and chronic obstructive pulmonary disease: data from the RIETE Registry
Background: Patients with chronic obstructive pulmonary disease (COPD) have a modified clinical presentation of venous thromboembolism (VTE) but also a worse prognosis than non-COPD patients with VTE. As it may induce therapeutic modifications, we evaluated the influence of the initial VTE presentation on the 3-month outcomes in COPD patients. Methods: COPD patients included in the on-going world-wide RIETE Registry were studied. The rate of pulmonary embolism (PE), major bleeding and death during the first 3 months in COPD patients were compared according to their initial clinical presentation (acute PE or deep vein thrombosis (DVT)). Results: Of the 4036 COPD patients included, 2452 (61%; 95% CI: 59.2-62.3) initially presented with PE. PE as the first VTE recurrence occurred in 116 patients, major bleeding in 101 patients and mortality in 443 patients (Fatal PE: first cause of death). Multivariate analysis confirmed that presenting with PE was associated with higher risk of VTE recurrence as PE (OR, 2.04; 95% CI: 1.11-3.72) and higher risk of fatal PE (OR, 7.77; 95% CI: 2.92-15.7). Conclusions: COPD patients presenting with PE have an increased risk for PE recurrences and fatal PE compared with those presenting with DVT alone. More efficient therapy is needed in this subtype of patients
Transient non-collinear magnetic state for all-optical magnetization switching
Resonant absorption of a photon by bound electrons in a solid can promote an
electron to another orbital state or transfer it to a neighboring atomic site.
Such a transition in a magnetically ordered material could affect the magnetic
order. While this process is an obvious road map for optical control of
magnetization, experimental demonstration of such a process remains
challenging. Exciting a significant fraction of magnetic ions requires a very
intense incoming light beam, as orbital resonances are often weak compared to
above-band-gap excitations. In the latter case, a sizeable reduction of the
magnetization occurs as the absorbed energy increases the spin temperature,
masking the non-thermal optical effects. Here, using ultrafast x-ray
spectroscopy, we were able to resolve changes in the magnetization state
induced by resonant absorption of infrared photons in Co-doped yttrium iron
garnet, with negligible thermal effects. We found that the optical excitation
of the Co ions affects the two distinct magnetic Fe sublattices differently,
resulting in a transient non-collinear magnetic state. The present results
indicate that the all-optical magnetization switching most likely occurs due to
the creation of a transient, non-collinear magnetic state followed by coherent
spin rotations of the Fe moments
Spatiotemporally Controlled Cardiac Conduction Block Using High-Frequency Electrical Stimulation
Background:
Methods for the electrical inhibition of cardiac excitation have long been sought to control excitability and conduction, but to date remain largely impractical. High-amplitude alternating current (AC) stimulation has been known to extend cardiac action potentials (APs), and has been recently exploited to terminate reentrant arrhythmias by producing reversible conduction blocks. Yet, low-amplitude currents at similar frequencies have been shown to entrain cardiac tissues by generation of repetitive APs, leading in some cases to ventricular fibrillation and hemodynamic collapse in vivo. Therefore, an inhibition method that does not lead to entrainment – irrespective of the stimulation amplitude (bound to fluctuate in an in vivo setting) – is highly desirable.
Methodology/Principal Findings:
We investigated the effects of broader amplitude and frequency ranges on the inhibitory effects of extracellular AC stimulation on HL-1 cardiomyocytes cultured on microelectrode arrays, using both sinusoidal and square waveforms. Our results indicate that, at sufficiently high frequencies, cardiac tissue exhibits a binary response to stimulus amplitude with either prolonged APs or no effect, thereby effectively avoiding the risks of entrainment by repetitive firing observed at lower frequencies. We further demonstrate the ability to precisely define reversible local conduction blocks in beating cultures without influencing the propagation activity in non-blocked areas. The conduction blocks were spatiotemporally controlled by electrode geometry and stimuli duration, respectively, and sustainable for long durations (300 s).
Conclusion/Significance:
Inhibition of cardiac excitation induced by high-frequency AC stimulation exhibits a binary response to amplitude above a threshold frequency, enabling the generation of reversible conduction blocks without the risks of entrainment. This inhibition method could yield novel approaches for arrhythmia modeling in vitro, as well as safer and more efficacious tools for in vivo cardiac mapping and radio-frequency ablation guidance applications
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