3,329 research outputs found

    Measuring Spatial Dynamics in Metropolitan Areas

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    This paper introduces a new approach to measuring neighborhood change. Instead of the traditional method of identifying “neighborhoods†a priori and then studying how resident attributes change over time, our approach looks at the neighborhood more intrinsically as a unit that has both a geographic footprint and a socioeconomic composition. Therefore, change is identified when both as- pects of a neighborhood transform from one period to the next. Our approach is based on a spatial clustering algorithm that identifies neighborhoods at two points in time for one city. We also develop indicators of spatial change at both the macro (city) level as well as local (neighborhood) scale. We illustrate these methods in an application to an extensive database of time-consistent census tracts for 359 of the largest metropolitan areas in the US for the period 1990-2000.

    Viscous fingering in liquid crystals: Anisotropy and morphological transitions

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    We show that a minimal model for viscous fingering with a nematic liquid crystal in which anisotropy is considered to enter through two different viscosities in two perpendicular directions can be mapped to a two-fold anisotropy in the surface tension. We numerically integrate the dynamics of the resulting problem with the phase-field approach to find and characterize a transition between tip-splitting and side-branching as a function of both anisotropy and dimensionless surface tension. This anisotropy dependence could explain the experimentally observed (reentrant) transition as temperature and applied pressure are varied. Our observations are also consistent with previous experimental evidence in viscous fingering within an etched cell and simulations of solidification.Comment: 12 pages, 3 figures. Submitted to PR

    Effects of Nutrition on Cognitive Function in Adults with or without Cognitive Impairment: A Systematic Review of Randomized Controlled Clinical Trials

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    New dietary approaches for the prevention of cognitive impairment are being investigated. However, evidence from dietary interventions is mainly from food and nutrient supplement interventions, with inconsistent results and high heterogeneity between trials. We conducted a comprehensive systematic search of randomized controlled trials (RCTs) published in MEDLINE-PubMed, from January 2018 to July 2021, investigating the impact of dietary counseling, as well as food-based and dietary supplement interventions on cognitive function in adults with or without cognitive impairment. Based on the search strategy, 197 eligible publications were used for data abstraction. Finally, 61 articles were included in the analysis. There was reasonable evidence that dietary patterns, as well as food and dietary supplements improved cognitive domains or measures of brain integrity. The Mediterranean diet showed promising results, whereas the role of the DASH diet was not clear. Healthy food consumption improved cognitive function, although the quality of these studies was relatively low. The role of dietary supplements was mixed, with strong evidence of the benefits of polyphenols and combinations of nutrients, but with low evidence for PUFAs, vitamin D, specific protein, amino acids, and other types of supplements. Further well-designed RCTs are needed to guide the development of dietary approaches for the prevention of cognitive impairment

    Phase-field model for Hele-Shaw flows with arbitrary viscosity contrast. II. Numerical study

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    We implement a phase-field simulation of the dynamics of two fluids with arbitrary viscosity contrast in a rectangular Hele-Shaw cell. We demonstrate the use of this technique in different situations including the linear regime, the stationary Saffman-Taylor fingers and the multifinger competition dynamics, for different viscosity contrasts. The method is quantitatively tested against analytical predictions and other numerical results. A detailed analysis of convergence to the sharp interface limit is performed for the linear dispersion results. We show that the method may be a useful alternative to more traditional methods.Comment: 13 pages in revtex, 5 PostScript figures. changes: 1 reference added, figs. 4 and 5 rearrange

    An example of enhanced tephra deposition driven by topographically-induced atmospheric turbulence

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    Spatial variations in the thickness and grain-size characteristics of tephra fall deposits imply that tephra depositional processes cannot be fully captured by models of single-particle sedimentation from the base of the eruption plume. Here, we document a secondary thickness maximum in a ∼9.75 ka tephra fall deposit from Chaitén volcano, Chile (Cha1 eruption). This secondary thickness maximum is notably coarser-grained than documented historical examples, being dominated by medium-grained ash, and an origin via particle aggregation is therefore unlikely. In the region of secondary thickening, we propose that high levels of atmospheric turbulence accelerated particles held within the mid- to lower-troposphere (0 to ∼6 km) towards the ground surface. We suggest that this enhancement in vertical atmospheric mixing was driven by the breaking of lee waves, generated by winds passing over elevated topography beneath the eruption plume. Lower atmospheric circulation patterns may exert a significant control on the dispersal and deposition of tephra from eruption plumes across all spatial scales, particularly in areas of complex topography

    Genome-wide analysis of porcine backfat and intramuscular fat fatty acid composition using high-density genotyping and expression data

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    [EN] Background: Porcine fatty acid composition is a key factor for quality and nutritive value of pork. Several QTLs for fatty acid composition have been reported in diverse fat tissues. The results obtained so far seem to point out different genetic control of fatty acid composition conditional on the fat deposits. Those studies have been conducted using simple approaches and most of them focused on one single tissue. The first objective of the present study was to identify tissue-specific and tissue-consistent QTLs for fatty acid composition in backfat and intramuscular fat, combining linkage mapping and GWAS approaches and conducted under single and multitrait models. A second aim was to identify powerful candidate genes for these tissue-consistent QTLs, using microarray gene expression data and following a targeted genetical genomics approach. Results: The single model analyses, linkage and GWAS, revealed over 30 and 20 chromosomal regions, 24 of them identified here for the first time, specifically associated to the content of diverse fatty acids in BF and IMF, respectively. The analyses with multitrait models allowed identifying for the first time with a formal statistical approach seven different regions with pleiotropic effects on particular fatty acids in both fat deposits. The most relevant were found on SSC8 for C16:0 and C16:1(n-7) fatty acids, detected by both linkage and GWAS approaches. Other detected pleiotropic regions included one on SSC1 for C16:0, two on SSC4 for C16:0 and C18:2, one on SSC11 for C20:3 and the last one on SSC17 for C16:0. Finally, a targeted eQTL scan focused on regions showing tissue consistent effects was conducted with Longissimus and fat gene expression data. Some powerful candidate genes and regions were identified such as the PBX1, RGS4, TRIB3 and a transcription regulatory element close to ELOVL6 gene to be further studied. Conclusions: Complementary genome scans have confirmed several chromosome regions previously associated to fatty acid composition in backfat and intramuscular fat, but even more, to identify new ones. Although most of the detected regions were tissue-specific, supporting the hypothesis that the major part of genes affecting fatty acid composition differs among tissues, seven chromosomal regions showed tissue-consistent effects. Additional gene expression analyses have revealed powerful target regions to carry the mutation responsible for the pleiotropic effects.This work was funded by the MICINN project AGL2011-29821-C02 (Ministerio de Economia y Competitividad). We thank to Fabian Garcia, Anna Mercade and Carmen Barragan for their assistance in DNA preparation and SNP genotyping.Muñoz, M.; Rodríguez, MC.; Alves, E.; Folch, J.; Ibañez Escriche, N.; Silió, L.; Fernández, A. (2013). Genome-wide analysis of porcine backfat and intramuscular fat fatty acid composition using high-density genotyping and expression data. BMC Genomics. 14. https://doi.org/10.1186/1471-2164-14-845S14Lichtenstein, A. H. (2003). Dietary Fat and Cardiovascular Disease Risk: Quantity or Quality? Journal of Women’s Health, 12(2), 109-114. doi:10.1089/154099903321576493Jiménez-Colmenero, F., Ventanas, J., & Toldrá, F. (2010). Nutritional composition of dry-cured ham and its role in a healthy diet. Meat Science, 84(4), 585-593. doi:10.1016/j.meatsci.2009.10.029Webb, E. C., & O’Neill, H. A. (2008). The animal fat paradox and meat quality. Meat Science, 80(1), 28-36. doi:10.1016/j.meatsci.2008.05.029Wood, J. D., Enser, M., Fisher, A. V., Nute, G. R., Sheard, P. 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PLoS ONE, 4(8), e6524. doi:10.1371/journal.pone.0006524Corominas, J., Ramayo-Caldas, Y., Puig-Oliveras, A., Pérez-Montarelo, D., Noguera, J. L., Folch, J. M., & Ballester, M. (2013). Polymorphism in the ELOVL6 Gene Is Associated with a Major QTL Effect on Fatty Acid Composition in Pigs. PLoS ONE, 8(1), e53687. doi:10.1371/journal.pone.0053687Ponsuksili, S., Jonas, E., Murani, E., Phatsara, C., Srikanchai, T., Walz, C., … Wimmers, K. (2008). Trait correlated expression combined with expression QTL analysis reveals biological pathways and candidate genes affecting water holding capacity of muscle. BMC Genomics, 9(1), 367. doi:10.1186/1471-2164-9-367Steibel, J. P., Bates, R. O., Rosa, G. J. M., Tempelman, R. J., Rilington, V. D., Ragavendran, A., … Ernst, C. W. (2011). Genome-Wide Linkage Analysis of Global Gene Expression in Loin Muscle Tissue Identifies Candidate Genes in Pigs. PLoS ONE, 6(2), e16766. doi:10.1371/journal.pone.0016766C�novas, A., Quintanilla, R., Amills, M., & Pena, R. 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    Phase-field model for Hele-Shaw flows with arbitrary viscosity contrast. I. Theoretical approach

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    We present a phase-field model for the dynamics of the interface between two inmiscible fluids with arbitrary viscosity contrast in a rectangular Hele-Shaw cell. With asymptotic matching techniques we check the model to yield the right Hele-Shaw equations in the sharp-interface limit and compute the corrections to these equations to first order in the interface thickness. We also compute the effect of such corrections on the linear dispersion relation of the planar interface. We discuss in detail the conditions on the interface thickness to control the accuracy and convergence of the phase-field model to the limiting Hele-Shaw dynamics. In particular, the convergence appears to be slower for high viscosity contrasts.Comment: 17 pages in revtex. changes: 1 reference adde

    Loosenin, a novel protein with cellulose-disrupting activity from Bjerkandera adusta

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    <p>Abstract</p> <p>Background</p> <p>Expansins and expansin-like proteins loosen cellulose microfibrils, possibly through the rupture of intramolecular hydrogen bonds. Together with the use of lignocellulolytic enzymes, these proteins are potential molecular tools to treat plant biomass to improve saccharification yields.</p> <p>Results</p> <p>Here we describe a new type of expansin-related fungal protein that we have called loosenin. Its corresponding gene, <it>loos1</it>, from the basidiomycete <it>Bjerkandera adusta</it>, was cloned and heterologously expressed in <it>Saccharomyces cerevisiae</it>. LOOS1 is distantly related to plant expansins through the shared presence of a DPBB domain, however domain II found in plant expansins is absent. LOOS1 binds tightly to cellulose and chitin, and we demonstrate that cotton fibers become susceptible to the action of a commercial cellulase following treatment with LOOS1. Natural fibers of <it>Agave tequilana </it>also become susceptible to hydrolysis by cellulases after loosenin treatment.</p> <p>Conclusions</p> <p>LOOS1 is a new type of protein with disrupting activity on cellulose. LOOS1 binds polysaccharides, and given its enhancing properties on the action of hydrolytic enzymes, LOOS1 represents a potential additive in the production of fermentable sugars from lignocellulose.</p
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