170 research outputs found

    Partial regularity for almost minimizers of quasi-convex integrals

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    We consider almost minimizers of variational integrals whose integrands are quasiconvex. Under suitable growth conditions on the integrand and on the function determining the almost minimality, we establish almost everywhere regularity for almost minimizers and obtain results on the regularity of the gradient away from the singular set. We give examples of problems from the calculus of variations whose solutions can be viewed as such almost minimizers

    Asymptotic stability, concentration, and oscillation in harmonic map heat-flow, Landau-Lifshitz, and Schroedinger maps on R^2

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    We consider the Landau-Lifshitz equations of ferromagnetism (including the harmonic map heat-flow and Schroedinger flow as special cases) for degree m equivariant maps from R^2 to S^2. If m \geq 3, we prove that near-minimal energy solutions converge to a harmonic map as t goes to infinity (asymptotic stability), extending previous work down to degree m = 3. Due to slow spatial decay of the harmonic map components, a new approach is needed for m=3, involving (among other tools) a "normal form" for the parameter dynamics, and the 2D radial double-endpoint Strichartz estimate for Schroedinger operators with sufficiently repulsive potentials (which may be of some independent interest). When m=2 this asymptotic stability may fail: in the case of heat-flow with a further symmetry restriction, we show that more exotic asymptotics are possible, including infinite-time concentration (blow-up), and even "eternal oscillation".Comment: 34 page

    Charged particle densities from Au+Au collisions at sqrt{s_{NN}}=130 GeV

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    We present charged particle densities as a function of pseudorapidity and collision centrality for the 197Au+197Au reaction at sqrt{s_{NN}}=130 GeV. An integral charged particle multiplicity of 3860+/-300 is found for the 5% most central events within the pseudorapidity range -4.7 <= eta <= 4.7. At mid-rapidity an enhancement in the particle yields per participant nucleon pair is observed for central events. Near to the beam rapidity, a scaling of the particle yields consistent with the ``limiting fragmentation'' picture is observed. Our results are compared to other recent experimental and theoretical discussions of charged particle densities in ultra-relativistic heavy-ion collisions.Comment: 14 pages, 4 figures; to be published in Phys. Lett.

    Elastic scattering of 27.5 MeV alpha particles on 27^{27}Al, 28^{28}Si, 32^{32}S, Ti and 59^{59}Co nuclei and the r0r_{0} discrete ambiguity of the optical potential

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    Angular distributions for elastic scattering of alpha particles on 27^{27}Al, 28^{28}Si, 32^{32}S, Ti and 59^{59}Co nuclei have been measured in the angular range from about 20^{\circ} to 179^{\circ} (LAB). The experimental data were fitted with the optical model in full angular range. Many sets of four-parameter potentials, describing the elastic scattering, were found with the depths of the real part ranging from 40 to 450 MeV. A new discrete ambiguity in the optical model namely in r0r_{0} was observed

    Statistical analysis of excitation functions for elastic and inelastic scattering of α\alpha-particles on Mg and Si nuclei

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    The excitation functions for inelastic α\alpha-scattering leading to the low lying excited states in 24^{24}Mg and 28^{28}Si were measured at ΘLAB\Theta_{LAB} = 170°, 175° and 179° in the LAB energy range 22.75–28.40 MeV. Statistical analysis of these excitation functions and those previously measured for elastic scattering was performed. The direct interaction contribution yD\mathit{y}_{D} to the reaction studied was obtained from probability distributions of cross sections and from correlation coefficients. Cross correlation coefficients between different reaction channels were calculated

    Are Elevated Levels of IGF-1 Caused by Coronary Arteriesoclerosis?: Molecular and Clinical Analysis

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    The importance of insulin-like growth factor-1 (IGF-1) in coronary artery disease (CAD) due to wide range of its biological effects and its therapeutic potential, has already been described. Our aim was to evaluate possible influence of IGF-1 serum level changes on coronary atherosclerosis. In case of existence of such association our further aim was to verify and explain this phenomenon by examination of promoter P1 of IGF-1gene and receptor gene for IGF-1. The study was performed in 101 consecutive patients undergo for routine coronary angiography. Quantitative and qualitative assessment of coronary atherosclerosis was performed respectively by estimation of the number of culprit lesions in coronary arteries and by Gensini score calculation. IGF-1, IGFBP3 and plasma lipoproteins were measured in all patients. In addition, we evaluated DNA from 101 patients, isolated from blood cells, which was amplified by using PCR with sophisticated primers for P1 promoter of IGF-1 gene and IGF-1 receptor gene, then analyzed utilizing SSCP technique and automatically sequenced. We observed significant increase of serum IGF-1 levels in patients with “3 vessel disease” and with high score in Gensini scale when compared to those without any narrowing lesions in coronary arteries and 0 Gensini score (in group with 3 vessel disease 215.0 ± 71.3 versuss 176.7 ± 34.2 ng/ml p = 0.04 and with high Gensini score 231.4 ± 59.3 versus 181.0 ± 37.8 ng/ml p = 0.01).We found different genotypes for five P1 promoter polymorphisms of IGF-1 gene (RS35767, RS5742612, RS228837, RS11829693, RS17879774). There were no significant associations between the observed single nucleotide polymorphism (SNP) and coronary atherosclerosis nor with levels of circulating IGF-1. We found no structural polymorphism in receptor gene for IGF-1 nor in its extracellular domain(exon 2–4) nor in internal domain (exon 16–21). The effect of increased IGF-1 serum level in our study was probably independent from structural polymorphism in promoter P1 for IGF-1 or in receptor gene for IGF-1

    The experience of providing young people attending general practice with an online risk assessment tool to assess their own sexual health risk

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    <p>Abstract</p> <p>Background</p> <p>Targeted chlamydia screening has been advocated to reduce chlamydia associated reproductive sequelae. General practitioners are well positioned to play a major role in chlamydia control. The primary aim of this pilot study was to measure the effect of offering an online sexual health assessment tool, <it>Youth Check Your Risk</it>, on chlamydia testing rates among young people attending general practices. The secondary aim was to test the acceptability of the tool among general practitioners and young people.</p> <p>Methods</p> <p>General practitioners at three practices in Melbourne, Australia, referred patients aged 16 to 24 years to <it>Youth Check Your Risk </it><url>http://www.checkyourrisk.org.au</url> for use post-consultation between March to October 2007. The proportion of young people tested for chlamydia before and during the implementation of the tool was compared. Acceptability was assessed through a structured interviewer-administered questionnaire with general practitioners, and anonymous online data provided by <it>Youth Check Your Risk </it>users.</p> <p>Results</p> <p>The intervention did not result in any significant increases in the proportion of 16 to 24 year old males (2.7% to 3.0%) or females (6.3% to 6.4%) tested for chlamydia. A small increase in the proportion of 16 to 19 year old females tested was seen (4.1% to 7.2%). Of the 2997 patients seen during the intervention phase, 871 (29.1%) were referred to <it>Youth Check Your Risk </it>and 120 used it (13.8%). Major reasons for low referral rates reported by practitioners included lack of time, discomfort with raising the issue of testing, and difficulty in remembering to refer patients.</p> <p>Conclusion</p> <p>Offering an online sexual risk assessment tool in general practice did not significantly increase the proportion of young people tested for chlamydia, with GPs identifying a number of barriers to referring young people to <it>Youth Check Your Risk</it>. Future interventions aimed at increasing chlamydia screening in general practice with the aid of an online risk assessment tool need to identify and overcome barriers to testing.</p
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