576 research outputs found

    Global wellposedness for a certain class of large initial data for the 3D Navier-Stokes Equations

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    In this article, we consider a special class of initial data to the 3D Navier-Stokes equations on the torus, in which there is a certain degree of orthogonality in the components of the initial data. We showed that, under such conditions, the Navier-Stokes equations are globally wellposed. We also showed that there exists large initial data, in the sense of the critical norm B,1B^{-1}_{\infty,\infty} that satisfies the conditions that we considered.Comment: 13 pages, updated references for v

    Vascular plant changes in extreme environments: effects of multiple drivers

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    The Antarctic Peninsula is one of three regions of the planet that have experienced the highest rates of climate warming over recent decades. Based on a comprehensive large-scale resurvey, allowing comparison of new (2009) and historical data (1960s), we show that the two native Antarctic vascular plant species have exhibited significant increases in number of occupied sites and percent cover since the 1960s: Deschampsia antarctica increasing in coverage by 191 % and in number of sites by 104 %. Colobanthus quitensis increasing in coverage by 208 % and number of sites by 35 %. These changes likely occurred in response to increases of 1.2 °C in summer air temperature over the same time period. Both species exhibited changes with elevation due to the interaction of multiple drivers (climatic factors and animal disturbance), producing heterogeneity of responses across an elevation gradient. Below an elevation of 20 m fur seal activity exerted negative impacts. Between 20 and 60 m, both plant species underwent considerable increases in the number of sites and percent cover, likely influenced by both climate warming and nutrient input from seals. Above an elevation threshold of 60 m the maximum elevation of the sites occupied decreased for both species, perhaps as a consequence of physical disturbance at higher elevations due to the permafrost conditions and/or the snow cover thickness and persistence. Understanding the role of disturbance drivers for vegetation change in cold regions may become a research priority to enable improved forecasting of biological responses and feedbacks of climate warming on ecosystems in these globally influential regions

    The Beale-Kato-Majda criterion to the 3D Magneto-hydrodynamics equations

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    We study the blow-up criterion of smooth solutions to the 3D MHD equations. By means of the Littlewood-Paley decomposition, we prove a Beale-Kato-Majda type blow-up criterion of smooth solutions via the vorticity of velocity only, i. e. \sup_{j\in\Z}\int_0^T\|\Delta_j(\na\times u)\|_\infty dt, where Δj\Delta_j is a frequency localization on ξ2j|\xi|\approx 2^j.Comment: 12page

    Viscous-Inviscid Interactions in a Boundary-Layer Flow Induced by a Vortex Array

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    In this paper we investigate the asymptotic validity of boundary layer theory. For a flow induced by a periodic row of point-vortices, we compare Prandtl's solution to Navier-Stokes solutions at different ReRe numbers. We show how Prandtl's solution develops a finite time separation singularity. On the other hand Navier-Stokes solution is characterized by the presence of two kinds of viscous-inviscid interactions between the boundary layer and the outer flow. These interactions can be detected by the analysis of the enstrophy and of the pressure gradient on the wall. Moreover we apply the complex singularity tracking method to Prandtl and Navier-Stokes solutions and analyze the previous interactions from a different perspective

    Mechanical Performance of Asphalt Mortar Containing Hydrated Lime and EAFSS at Low and High Temperatures

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    In this paper, the possibility of improving the global response of asphalt materials for pavement applications through the use of hydrated lime and Electric Arc-Furnace Steel Slag (EAFSS) was investigated. For this purpose, a set of asphalt mortars was prepared by mixing two different asphalt binders with fine granite aggregate together with hydrated lime or EAFSS at three different percentages. Bending Beam Rheometer (BBR) creep tests and Dynamic Shear Rheometer (DSR) complex modulus tests were performed to evaluate the material response both at low and high temperature. Then, the rheological Huet model was fitted to the BBR creep results for estimating the impact of filler content on the model parameters. It was found that an addition of hydrated lime and EAFSS up to 10% and 5%, respectively, results in satisfactory low-temperature performance with a substantial improvement of the high-temperature behavior

    Ethnic fragmentation and degree of urbanization strongly affect the discrimination power of Y-STR haplotypes in central Sahel

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    Y chromosome short tandem repeats (Y-STRs) are commonly used to identify male lineages for investigative and judicial purposes and could represent the only source of male-specific genetic information from unbalanced female-male mixtures. The Yfiler Plus multiplex, which includes twenty conventional and seven rapidly-mutating Y-STRs, represents the most discriminating patrilineal system commercially available to date. Over the past five years, this multiplex has been used to analyze several Eurasian populations, with a reported discrimination capacity (DC) approaching or corresponding to the highest possible value. However, despite the inclusion of rapidly mutating Y-STRs, extensive haplotype sharing was still reported for some African populations due to a number of different factors affecting the effective population size. In the present study, we analyzed 27 Y-STRs included in the Yfiler Plus multiplex and 82 Y-SNPs in central Sahel (northern Cameroon and western Chad), an African region characterized by a strong ethnic fragmentation and linguistic diversity. We evaluated the effects of population sub-structuring on genetic diversity by stratifying a sample composed of 431 males according to their ethnicity (44 different ethnic groups) and urbanization degree (four villages and four towns). Overall, we observed a low discrimination capacity (DC = 0.90), with 71 subjects (16.5 %) sharing 27 Y-STR haplotypes. Haplotype sharing was essentially limited to subjects with the same binary haplogroup, coming from the same location and belonging to the same ethnic group. Haplotype sharing was much higher in rural areas (average DC = 0.83) than urban settlements (average DC = 0.96) with a significant correlation between DC and census size (r = 0.89; p = 0.003). Notably, we found that genetic differentiation between villages from the same country (ΦST = 0.14) largely exceeded that found among countries (ΦST = 0.02). These findings have important implications for the choice of the appropriate reference population database to evaluate the statistical relevance of forensic Y-haplotype matches

    Randomised trial comparing biweekly oxaliplatin plus oral capecitabine versus oxaliplatin plus i.v. bolus fluorouracil/leucovorin in metastatic colorectal cancer patients: results of the Southern Italy Cooperative Oncology study 0401

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    Oxaliplatin combined with either fluorouracil/leucovorin (OXAFAFU) or capecitabine (OXXEL) has a demonstrated activity in metastatic colorectal cancer patients. We aimed at comparing these two regimens in terms of response rate (RR), safety, progression-free survival (PFS), and quality of life (QoL) of patients

    Moss survival through in situ cryptobiosis after six centuries of glacier burial

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    Cryptobiosis is a reversible ametabolic state of life characterized by the ceasing of all metabolic processes, allowing survival of periods of intense adverse conditions. Here we show that 1) entire moss individuals, dated by 14C, survived through cryptobiosis during six centuries of cold-based glacier burial in Antarctica, 2) after re-exposure due to glacier retreat, instead of dying (due to high rates of respiration supporting repair processes), at least some of these mosses were able to return to a metabolically active state and remain alive. Moss survival was assessed through growth experiments and, for the first time, through vitality measurements. Future investigations on the genetic pathways involved in cryptobiosis and the subsequent recovery mechanisms will provide key information on their applicability to other systematic groups, with implications for fields as divergent as medicine, biodiversity conservation, agriculture and space exploration

    Protein kinase C theta (PKCθ) modulates the ClC-1 chloride channel activity and skeletal muscle phenotype: a biophysical and gene expression study in mouse models lacking the PKCθ

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    In skeletal muscle, the resting chloride conductance (gCl), due to the ClC-1 chloride channel, controls the sarcolemma electrical stability. Indeed, loss-of-function mutations in ClC-1 gene are responsible of myotonia congenita. The ClC-1 channel can be phosphorylated and inactivated by protein kinases C (PKC), but the relative contribution of each PKC isoforms is unknown. Here, we investigated on the role of PKCθ in the regulation of ClC-1 channel expression and activity in fast- and slow-twitch muscles of mouse models lacking PKCθ. Electrophysiological studies showed an increase of gCl in the PKCθ-null mice with respect to wild type. Muscle excitability was reduced accordingly. However, the expression of the ClC-1 channel, evaluated by qRT-PCR, was not modified in PKCθ-null muscles suggesting that PKCθ affects the ClC-1 activity. Pharmacological studies demonstrated that although PKCθ appreciably modulates gCl, other isoforms are still active and concur to this role. The modification of gCl in PKCθ-null muscles has caused adaptation of the expression of phenotype-specific genes, such as calcineurin and myocyte enhancer factor-2, supporting the role of PKCθ also in the settings of muscle phenotype. Importantly, the lack of PKCθ has prevented the aging-related reduction of gCl, suggesting that its modulation may represent a new strategy to contrast the aging process
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