6,811 research outputs found

    Strange and charged particle elliptic flow in Pb+Au collisions at 158 AGeV/c

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    We present Λ\Lambda and π\pi elliptic flow measurements from Pb+Au collisions at the highest SPS energy. The data, collected by the CERES experiment which covers η=2.05,2.70\eta=2.05,2.70 with full azimuthal coverage and wide pTp_{T} sensitivity up to 3.5 GeV/c, can be used to test hydrodynamical models and show sensitivity to the EoS. The value of v2v_{2} as a function of centrality and pTp_{T} is presented. Values of v2v_{2} observed by STAR at RHIC are larger by about 1/3. Our measurements are compared to results from other SPS experiments and to hydrodynamical calculations. Huge statistics allows for a precise measurement of the differential pion elliptic flow.Comment: Proceeding for Quark Matter 2005, parallel talk, 4 pages, 7 figure

    Evolution of multi-gap superconductivity in the atomically thin limit: Strain-enhanced three-gap superconductivity in monolayer MgB2_2

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    Starting from first principles, we show the formation and evolution of superconducting gaps in MgB2_2 at its ultrathin limit. Atomically thin MgB2_2 is distinctly different from bulk MgB2_2 in that surface states become comparable in electronic density to the bulk-like σ\sigma- and π\pi-bands. Combining the ab initio electron-phonon coupling with the anisotropic Eliashberg equations, we show that monolayer MgB2_2 develops three distinct superconducting gaps, on completely separate parts of the Fermi surface due to the emergent surface contribution. These gaps hybridize nontrivially with every extra monolayer added to the film, owing to the opening of additional coupling channels. Furthermore, we reveal that the three-gap superconductivity in monolayer MgB2_2 is robust over the entire temperature range that stretches up to a considerably high critical temperature of 20 K. The latter can be boosted to >>50 K under biaxial tensile strain of \sim 4\%, which is an enhancement stronger than in any other graphene-related superconductor known to date.Comment: To appear in Phys. Re

    Inelastic collisions of relativistic electrons with atomic targets assisted by a laser field

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    We consider inelastic collisions between relativistic electrons and atomic targets assisted by a low-frequency laser field in the case when this field is still much weaker than the typical internal fields in the target. Concentrating on target transitions we show that they can be substantially affected by the presence of the laser field. This may occur either via strong modifications in the motion of the relativistic electrons caused by the electron-laser interaction or via the Compton effect when the incident electrons convert laser photon(s) into photons with frequencies equal to target transition frequencies.Comment: 4 pages, 2 figure

    Sharp oscillation criteria for fourth order sub-half-linear and super-half-linear differential equations

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    This paper is concerned with the oscillatory behavior of the fourth-order nonlinear differential equation (p(t)xα1x)+q(t)xβ1x=0,(E) \bigl(p(t)|x^{\prime\prime}|^{\alpha-1}\,x^{\prime\prime}\bigr)^{\prime\prime} +q(t)|x|^{\beta-1}x=0\,,\tag{E} where α>0\alpha>0, β>0\beta>0 are constants and p,q:[a,)(0,)p,q:[a,\infty)\to(0,\infty) are continuous functions satisfying conditions a(tp(t))1αdt<,at(p(t))1αdt<. \int_a^{\infty}\left( \frac{t}{p(t)}\right)^{\frac{1}{\alpha}}\,dt<\infty, \int_a^{\infty}\frac{t}{\left(p(t)\right)^{\frac{1}{\alpha}}}\,dt<\infty . We will establish necessary and sufficient condition for oscillation of all solutions of the sub-half-linear equation (E) (for βα\beta\alpha)

    Substrate induced proximity effect in superconducting niobium nanofilms

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    Structural and superconducting properties of high quality Niobium nanofilms with different thicknesses are investigated on silicon oxide and sapphire substrates. The role played by the different substrates and the superconducting properties of the Nb films are discussed based on the defectivity of the films and on the presence of an interfacial oxide layer between the Nb film and the substrate. The X-ray absorption spectroscopy is employed to uncover the structure of the interfacial layer. We show that this interfacial layer leads to a strong proximity effect, specially in films deposited on a SiO2_2 substrate, altering the superconducting properties of the Nb films. Our results establish that the critical temperature is determined by an interplay between quantum-size effects, due to the reduction of the Nb film thicknesses, and proximity effects

    Increased risk of HIV and other drug-related harms associated with injecting in public places: national bio-behavioural survey of people who inject drugs

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    Background: Whilst injecting drugs in public places is considered a proxy for high risk behaviour among people who inject drugs (PWID), studies quantifying its relationship with multiple drug-related harms are lacking and none have examined this in the context of an ongoing HIV outbreak (located in Glasgow, Scotland). We aimed to: 1) estimate the prevalence of public injecting in Scotland and associated risk factors; and 2) estimate the association between public injecting and HIV, current HCV, overdose, and skin and soft tissue infections (SSTI). Methods: Cross-sectional, bio-behavioural survey (including dried blood spot testing to determine HIV and HCV infection) of 1469 current PWID (injected in last 6 months) recruited by independent interviewers from 139 harm reduction services across Scotland during 2017–18. Primary outcomes were: injecting in a public place (yes/no); HIV infection; current HCV infection; self-reported overdose in the last year (yes/no) and SSTI the last year (yes/no). Multi-variable logistic regression was used to determine factors associated with public injecting and to estimate the association between public injecting and drug-related harms (HIV, current HCV, overdose and SSTI). Results: Prevalence of public injecting was 16% overall in Scotland and 47% in Glasgow city centre. Factors associated with increased odds of public injecting were: recruitment in Glasgow city centre (aOR=5.45, 95% CI 3.48–8.54, p&lt;0.001), homelessness (aOR=3.68, 95% CI 2.61–5.19, p&lt;0.001), high alcohol consumption (aOR=2.42, 95% CI 1.69–3.44, p&lt;0.001), high injection frequency (≥4 per day) (aOR=3.16, 95% CI 1.93–5.18, p&lt;0.001) and cocaine injecting (aOR=1.46, 95% CI 1.00 to 2.13, p = 0.046). Odds were lower for those receiving opiate substitution therapy (OST) (aOR=0.37, 95% CI 0.24 to 0.56, p&lt;0.001) and older age (per year increase) (aOR=0.97, 95% CI 0.95 to 0.99, p = 0.013). Public injecting was associated with an increased risk of HIV infection (aOR=2.11, 95% CI 1.13–3.92, p = 0.019), current HCV infection (aOR=1.49, 95% CI 1.01–2.19, p = 0.043), overdose (aOR=1.59, 95% CI 1.27–2.01, p&lt;0.001) and SSTI (aOR=1.42, 95% CI 1.17–1.73, p&lt;0.001). Conclusions: These findings highlight the need to address the additional harms observed among people who inject in public places and provide evidence to inform proposals in the UK and elsewhere to introduce facilities that offer safer drug consumption environments