1,219 research outputs found

    The frustrated Brownian motion of nonlocal solitary waves

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    We investigate the evolution of solitary waves in a nonlocal medium in the presence of disorder. By using a perturbational approach, we show that an increasing degree of nonlocality may largely hamper the Brownian motion of self-trapped wave-packets. The result is valid for any kind of nonlocality and in the presence of non-paraxial effects. Analytical predictions are compared with numerical simulations based on stochastic partial differential equationComment: 4 pages, 3 figures

    Statistics of soliton-bearing systems with additive noise

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    We present a consistent method to calculate the probability distribution of soliton parameters in systems with additive noise. Even though a weak noise is considered, we are interested in probabilities of large fluctuations (generally non-Gaussian) which are beyond perturbation theory. Our method is a further development of the instanton formalism (method of optimal fluctuation) based on a saddle-point approximation in the path integral. We first solve a fundamental problem of soliton statistics governing by noisy Nonlinear Schr\"odinger Equation (NSE). We then apply our method to optical soliton transmission systems using signal control elements (filters, amplitude and phase modulators).Comment: 4 pages. Submitted to PR

    Coexistence of coarsening and mean field relaxation in the long-range Ising chain

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    We study the kinetics after a low temperature quench of the one-dimensional Ising model with long range interactions between spins at distance r decaying as r-α. For α = 0, i.e. mean field, all spins evolve coherently quickly driving the system towards a magnetised state. In the weak long range regime with α > 1 there is a coarsening behaviour with competing domains of opposite sign without development of magnetisation. For strong long range, i.e. 0 < α < 1, we show that the system shows both features, with probability Pα(N) of having the latter one, with the different limiting behaviours limN→∞ Pα(N) = 0 (at fixed α < 1) and limα→1 Pα(N) = 1 (at fixed finite N). We discuss how this behaviour is a manifestation of an underlying dynamical scaling symmetry due to the presence of a single characteristic time τα(N) ∼ Nα

    Statistics of a noise-driven Manakov soliton

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    We investigate the statistics of a vector Manakov soliton in the presence of additive Gaussian white noise. The adiabatic perturbation theory for Manakov soliton yields a stochastic Langevin system which we analyze via the corresponding Fokker-Planck equation for the probability density function (PDF) for the soliton parameters. We obtain marginal PDFs for the soliton frequency and amplitude as well as soliton amplitude and polarization angle. We also derive formulae for the variances of all soliton parameters and analyze their dependence on the initial values of polarization angle and phase.Comment: Submitted to J.Phys.A: Mathematical and Genera

    (RE)-AUTHORING THE STUDENT: AN EXPLORATION INTO FIGURED WORLDS, IDENTITY FORMATION, GENRE, PUBLICS, AND HOW POWER RELATIONS IMPACT CHILDREN'S WRITING

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    As digital media makes its way into elementary school classrooms, urban school culture moves slowly to join in. The move to integrate new technologies into schools is both enabled and constrained by factors such as the need for students and teachers to be seen as people who are "successful" in both public and social terms. The purpose of this dissertation was to explore the complexities for elementary children learning to write in the digital age. I used a case study approach, examining the language choices of eight third and fourth grade students (4 girls and 4 boys) who attended an urban elementary school in a large southeastern city in the United States. I analyzed how the students' language choices contributed to the construction/negotiation of their writer identities and the degree to which these constructs/negotiations were enabled/constrained by what the participants imagined was/not possible from their positions as students while composing with varying technologies. I conclude that it is not only the young writers who imagine what is/not possible from their position as students, it is also those who guide, or "authorize" student writing, including teachers, administrators, and parents. This constructing/negotiating, authorizing/guiding all take place as students seek to maintain membership (textually) within their school world while endeavoring to cultivate new memberships within expanses or publics that coexist alongside their schools. The young writers highlighted in this study, working against from within the school district's accountability and efficiency agenda show that being a "successful" student writer can mean more than their merely reproducing what is expected of them

    A Case of Osteonecrosis of the Jaw in a Patient with Crohn's Disease Treated with Infliximab

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    Background: Medication-related osteonecrosis of the jaw (MRONJ) is a severe adverse drug reaction, occurring in patients undergoing treatments with antiresorptive or antiangiogenic agents, such as bisphosphonates, denosumab, or bevacizumab, for different oncologic and non-oncologic diseases. The aim of this study was to report a case of MRONJ in a patient taking infliximab, an anti-TNF-alpha antibody used to treat Crohn's disease, rheumatoid arthritis, ulcerative colitis, ankylosing spondylitis, psoriatic arthritis, and plaque psoriasis. Case Report: A 49-year-old female patient affected by Crohn's disease, who had been undergoing 250 mg intravenous infliximab every six weeks for 12 years, with no history of antiresorptive or antiangiogenic agent administration, came to our attention for post-surgical MRONJ, associated with a wide cutaneous necrotic area of her anterior mandible. Following antibiotic cycles, the patient underwent surgical treatment with wide bone resection and debridement of necrotic tissues; after prolonged follow-up (16 months), the patient completely healed without signs of recurrence. Conclusions: Prevention of MRONJ by dental check-up before and during treatments with antiresorptive treatments (bisphosphonates or denosumab) is a well-established procedure. Although further studies are required to confirm the role of infliximab in MRONJ, based on the results of this study, we propose that patients who are going to be treated with infliximab should also undergo dental check-up before starting therapy, to possibly avoid MRONJ onset

    Noise-induced perturbations of dispersion-managed solitons

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    We study noise-induced perturbations of dispersion-managed solitons by developing soliton perturbation theory for the dispersion-managed nonlinear Schroedinger (DMNLS) equation, which governs the long-term behavior of optical fiber transmission systems and certain kinds of femtosecond lasers. We show that the eigenmodes and generalized eigenmodes of the linearized DMNLS equation around traveling-wave solutions can be generated from the invariances of the DMNLS equations, we quantify the perturbation-induced parameter changes of the solution in terms of the eigenmodes and the adjoint eigenmodes, and we obtain evolution equations for the solution parameters. We then apply these results to guide importance-sampled Monte-Carlo simulations and reconstruct the probability density functions of the solution parameters under the effect of noise.Comment: 12 pages, 6 figure

    Chronic viral hepatitis in a cohort of inflammatory bowel disease patients from southern Italy: A case-control study

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    We performed an epidemiologic study to assess the prevalence of chronic viral hepatitis in inflammatory bowel disease (IBD) and to detect their possible relationships. Methods: It was a single centre cohort cross-sectional study, during October 2016 and October 2017. Consecutive IBD adult patients and a control group of non-IBD subjects were recruited. All patients underwent laboratory investigations to detect chronic hepatitis B (HBV) and C (HCV) infection. Parameters of liver function, elastography and IBD features were collected. Univariate analysis was performed by Student’s t or chi-square test. Multivariate analysis was performed by binomial logistic regression and odds ratios (ORs) were calculated. We enrolled 807 IBD patients and 189 controls. Thirty-five (4.3%) had chronic viral hepatitis: 28 HCV (3.4%, versus 5.3% in controls, p = 0.24) and 7 HBV (0.9% versus 0.5% in controls, p = 0.64). More men were observed in the IBD-hepatitis group (71.2% versus 58.2%, p < 0.001). Patients with IBD and chronic viral hepatitis had a higher mean age and showed a higher frequency of diabetes, hypertension and wider waist circumference. They suffered more frequently from ulcerative colitis. Liver stiffness was greater in subjects with IBD and chronic viral hepatitis (7.0 ± 4.4 versus 5.0 ± 1.2 KPa; p < 0.001). At multivariate analysis, only old age directly correlated with viral hepatitis risk (OR = 1.05, 95%CI 1.02-1.08, p < 0.001). In conclusion, the prevalence of HBV/HCV in IBD is low in our region. Age may be the only independent factor of viral hepatitis-IBD association. Finally, this study firstly measured liver stiffness in a large scale, showing higher values in subjects with both diseases

    Optimización de la producción de biomasa usando glicerol crudo, de una cepa mutante de Yarrowia lipolytica con actividad incrementada de lipasa

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    218-225The yeast Yarrowia lipolytica accumulates oils and is able to produce extracellular lipases when growing in different carbon sources including glycerol, the principal by-product of the biodiesel industry. In this study, biomass production of a novel mutant strain of Y. lipolytica was statistically optimized by Response Surface Methodology in media containing biodiesel-derived glycerol as main carbon source. This strain exhibited distinctive morphological and fatty acid profile characteristics, and showed an increased extracellular lipase activity. An organic source of nitrogen and the addition of 1.0 g/l olive oil were necessary for significant lipase production. Plackett-Burman and Central Composite Statistical Designs were employed for screening and optimization of fermentation in shaken flasks cultures, and the maximum values obtained were 16.1 g/l for biomass and 12.2 Units/ml for lipase, respectively. Optimized batch bioprocess was thereafter scaled in aerated bioreactors and the values reached for lipase specific activity after 95 percent of the glycerol had been consumed, were three-fold higher than those obtained in shaken flasks cultures. A sustainable bioprocess to obtain biomass and extracellular lipase activity was attained by maximizing the use of the by-products of biodiesel industry
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