577 research outputs found
Systematic thermal reduction of neutronization in core-collapse supernovae
We investigate to what extent the temperature dependence of the nuclear
symmetry energy can affect the neutronization of the stellar core prior to
neutrino trapping during gravitational collapse. To this end, we implement a
one-zone simulation to follow the collapse until beta equilibrium is reached
and the lepton fraction remains constant. Since the strength of electron
capture on the neutron-rich nuclei associated to the supernova scenario is
still an open issue, we keep it as a free parameter. We find that the
temperature dependence of the symmetry energy consistently yields a small
reduction of deleptonization, which corresponds to a systematic effect on the
shock wave energetics: the gain in dissociation energy of the shock has a small
yet non-negligible value of about 0.4 foe (1 foe = 10^51 erg) and this result
is almost independent from the strength of nuclear electron capture. The
presence of such a systematic effect and its robustness under changes of the
parameters of the one-zone model are significative enough to justify further
investigations with detailed numerical simulations of supernova explosions.Comment: 15 pages, 2 tables, 3 figure
Triggering synchronized oscillations through arbitrarily weak diversity in close-to-threshold excitable media
It is shown that arbitrarily weak (frozen) heterogeneity can induce global
synchronized oscillations in excitable media close to threshold. The work is
carried out on networks of coupled van der Pol-FitzHugh-Nagumo oscillators. The
result is shown to be robust against the presence of internal dynamical noise.Comment: 4 pages (RevTeX 3 style), 5 EPS figures, submitted to Phys. Rev. E
(16 aug 2001
Modelling the particle contact influence on the Joule heating and temperature distribution during FLASH sintering
FLASH sintering is a field-assisted technique that allows the densification of ceramics in a few seconds at temperatures significantly lower than those of conventional cycles. There is still discussion among the scientific community about the mechanism behind this sintering process, that has been typically attributed to Joule heating, defect creation and movement or liquid phase assisted sintering. Computational modelling can be a powerful tool in helping to explain and predict this process. Using potassium sodium niobate (KNN) as a case study, a lead-free piezoelectric, this work explores Finite Element Modelling to evaluate the dependence of Joule heating generation and temperature distribution as a function of the cubic particle orientation
The role of particle contact in densification of FLASH sintered potassium sodium niobate
Potassium sodium niobate, K0.5Na0.5NbO3 (KNN) is a leadâfree piezoelectric with the potential to replace lead zirconate titanate (PZT) in electromechanical applications. Due to its cuboid particle morphology and volatile elements, monophasic and dense ceramics are difficult to obtain via conventional sintering. In this work, isothermal FLASH sintering produced uniformly densified KNN ceramics at 900 °C, 200 °C lower than conventional sintering. Specific surface area (SSA) analysis of preâFLASH ceramics revealed that a 30 min isothermal hold at 900 °C, before the application of electric field, increased the contact area between particles and was crucial to promote uniform densification. Finite element modelling (FEM) revealed why density is more uniform when using isothermal heating compared with a constant heating rate, commonly used in FLASH sintering. These results extend our understanding of FLASH sintering and illustrate its relevance for the development of leadâfree piezoelectrics
Emergent global oscillations in heterogeneous excitable media: The example of pancreatic beta cells
Using the standard van der Pol-FitzHugh-Nagumo excitable medium model I
demonstrate a novel generic mechanism, diversity, that provokes the emergence
of global oscillations from individually quiescent elements in heterogeneous
excitable media. This mechanism may be operating in the mammalian pancreas,
where excitable beta cells, quiescent when isolated, are found to oscillate
when coupled despite the absence of a pacemaker region.Comment: See home page http://lec.ugr.es/~julya
Final analysis from RESONATE: Up to six years of followâup on ibrutinib in patients with previously treated chronic lymphocytic leukemia or small lymphocytic lymphoma
Ibrutinib, a onceâdaily oral inhibitor of Bruton's tyrosine kinase, is approved in the United States and Europe for treatment of patients with chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL). The phase 3 RESONATE study showed improved efficacy of singleâagent ibrutinib over ofatumumab in patients with relapsed/refractory CLL/SLL, including those with highârisk features. Here we report the final analysis from RESONATE with median followâup on study of 65.3âmonths (range, 0.3â71.6) in the ibrutinib arm. Median progressionâfree survival (PFS) remained significantly longer for patients randomized to ibrutinib vs ofatumumab (44.1 vs 8.1âmonths; hazard ratio [HR]: 0.148; 95% confidence interval [CI]: 0.113â0.196; PË.001). The PFS benefit with ibrutinib vs ofatumumab was preserved in the genomic highârisk population with del(17p), TP53 mutation, del(11q), and/or unmutated IGHV status (median PFS 44.1 vs 8.0âmonths; HR: 0.110; 95% CI: 0.080â0.152), which represented 82% of patients. Overall response rate with ibrutinib was 91% (complete response/complete response with incomplete bone marrow recovery, 11%). Overall survival, censored for crossover, was better with ibrutinib than ofatumumab (HR: 0.639; 95% CI: 0.418â0.975). With up to 71âmonths (median 41âmonths) of ibrutinib therapy, the safety profile remained consistent with prior reports; cumulatively, allâgrade (gradeââ„3) hypertension and atrial fibrillation occurred in 21% (9%) and 12% (6%) of patients, respectively. Only 16% discontinued ibrutinib because of adverse events (AEs). These longâterm results confirm the robust efficacy of ibrutinib in relapsed/refractory CLL/SLL irrespective of highârisk clinical or genomic features, with no unexpected AEs. This trial is registered at www.clinicaltrials.gov (NCT01578707)
Measurement of the p-pbar -> Wgamma + X cross section at sqrt(s) = 1.96 TeV and WWgamma anomalous coupling limits
The WWgamma triple gauge boson coupling parameters are studied using p-pbar
-> l nu gamma + X (l = e,mu) events at sqrt(s) = 1.96 TeV. The data were
collected with the DO detector from an integrated luminosity of 162 pb^{-1}
delivered by the Fermilab Tevatron Collider. The cross section times branching
fraction for p-pbar -> W(gamma) + X -> l nu gamma + X with E_T^{gamma} > 8 GeV
and Delta R_{l gamma} > 0.7 is 14.8 +/- 1.6 (stat) +/- 1.0 (syst) +/- 1.0 (lum)
pb. The one-dimensional 95% confidence level limits on anomalous couplings are
-0.88 < Delta kappa_{gamma} < 0.96 and -0.20 < lambda_{gamma} < 0.20.Comment: Submitted to Phys. Rev. D Rapid Communication
Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt{s} = 1.96 TeV using Kinematic Characteristics of Lepton + Jets Events
We present a measurement of the top quark pair ttbar production cross section
in ppbar collisions at a center-of-mass energy of 1.96 TeV using 230 pb**{-1}
of data collected by the DO detector at the Fermilab Tevatron Collider. We
select events with one charged lepton (electron or muon), large missing
transverse energy, and at least four jets, and extract the ttbar content of the
sample based on the kinematic characteristics of the events. For a top quark
mass of 175 GeV, we measure sigma(ttbar) = 6.7 {+1.4-1.3} (stat) {+1.6- 1.1}
(syst) +/-0.4 (lumi) pb, in good agreement with the standard model prediction.Comment: submitted to Phys.Rev.Let
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