102 research outputs found

    Vanishing DC holographic conductivity from a magnetic monopole condensate

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    We show how to obtain a vanishing DC conductivity in 3-dimensional strongly coupled QFT's using a massive 2-form field in the bulk that satisfies a special kind of boundary condition. The real and imaginary parts of the AC conductivity are evaluated in this holographic setup and we show that the DC conductivity identically vanishes even for an arbitrarily small (though nonzero) value of the 2-form mass in the bulk. We identify the bulk action of the massive 2-form with an effective theory describing a phase in which magnetic monopoles have condensed in the bulk. Our results indicate that a condensate of magnetic monopoles in a 4-dimensional bulk leads to a vanishing DC holographic conductivity in 3-dimensional strongly coupled QFT's.Comment: 24 pages, 2 figures, accepted for publication in JHE

    Controversial Predictors Of Biochemical Recurrence After Radical Prostatectomy: A Study From A Latin American (brazilian) Institution.

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    To analyze controversial clinicopathologic predictors of biochemical recurrence after surgery: age, race, tumor extent on surgical specimen, tumor extent on needle biopsy, Gleason score 3 + 4 vs 4 + 3, and amount of extent of extraprostatic extension and positive surgical margins. The needle biopsies and the correspondent surgical specimens were analyzed from 400 patients. Time to recurrence was analyzed with the Kaplan-Meier curves and risk of shorter time to recurrence using Cox univariate and multivariate analysis. Except for age, race, maximum percentage of cancer per core, and number of cores with cancer, all other variables studied were significantly predictive of time to biochemical recurrence using the Kaplan-Meier curves. In univariate analysis, except for focal extraprostatic extension, age, race, focal positive surgical margins, and maximum extent and percentage of cancer per core, all other variables were significantly predictive of shorter time to recurrence. On multivariate analysis, diffuse positive surgical margins and preoperative PSA were independent predictors. Young patients and non-whites were not significantly associated with time to biochemical recurrence. The time consuming tumor extent evaluation in surgical specimens seems not to add additional information to other well established predictive findings. The higher predictive value of Gleason score 4 + 3 = 7 vs 3 + 4 = 7 discloses the importance of grade 4 as the predominant pattern. Extent and not simply presence or absent of extraprostatic extension should be informed. Most tumor extent evaluations on needle biopsies are predictive of time to biochemical recurrence, however, maximum percentage of cancer in all cores was the strongest predictor.39779-9

    Controversial predictors of biochemical recurrence after radical prostatectomy: a study from a Latin American (Brazilian) Institution

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    Purpose To analyze controversial clinicopathologic predictors of biochemical recurrence after surgery: age, race, tumor extent on surgical specimen, tumor extent on needle biopsy, Gleason score 3 + 4 vs 4 + 3, and amount of extent of extraprostatic extension and positive surgical margins. Materials and Methods The needle biopsies and the correspondent surgical specimens were analyzed from 400 patients. Time to recurrence was analyzed with the Kaplan-Meier curves and risk of shorter time to recurrence using Cox univariate and multivariate analysis. Results Except for age, race, maximum percentage of cancer per core, and number of cores with cancer, all other variables studied were significantly predictive of time to biochemical recurrence using the Kaplan-Meier curves. In univariate analysis, except for focal extraprostatic extension, age, race, focal positive surgical margins, and maximum extent and percentage of cancer per core, all other variables were significantly predictive of shorter time to recurrence. On multivariate analysis, diffuse positive surgical margins and preoperative PSA were independent predictors. Conclusions Young patients and non-whites were not significantly associated with time to biochemical recurrence. The time consuming tumor extent evaluation in surgical specimens seems not to add additional information to other well established predictive findings. The higher predictive value of Gleason score 4 + 3 = 7 vs 3 + 4 = 7 discloses the importance of grade 4 as the predominant pattern. Extent and not simply presence or absent of extraprostatic extension should be informed. Most tumor extent evaluations on needle biopsies are predictive of time to biochemical recurrence, however, maximum percentage of cancer in all cores was the strongest predictor.77979

    New insights into the distribution and conservation status of the Golden-White Tassel-Ear Marmoset Mico chrysoleucos (Primates, Callitrichidae)

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    Among the 13 Mico species recognized by the IUCN Red List of Threatened Species, six are listed as "Data Deficient". The geographic range of most of the Mico species has been estimated from only a few records. We report new localities and the geographic extension of Mico chrysoleucos. In addition, we confirmed the presence of the species in two distinct protected areas. We modeled the habitat suitability of M. chrysoleucos using the maximum entropy method and including new records obtained by the authors in the state of Amazonas, Brazil. From the total area of occurrence calculated for the species, 22.8% is covered by protected areas and indigenous lands. The annual mean deforestation rate estimated between 2000 and 2015 was 2.95%, and the total area deforested by 2015 was 3354 km2 or 8.6% of the total distribution limits of the species. The habitat lost between 2000 and 2015 was 3.2% (1131 km2 ) of the total potential distribution, while the habitat loss area legally protected was 31 km2, and the habitat loss in settlements was equal to 691 km2. Our results extend the geographic distribution of the species about 100 km farther south, with the Maracanã River being a possible geographic barrier for the species. The significantly low rate of habitat loss inside protected areas and indigenous land, when compared to unprotected areas, points out the importance of these areas to M. chrysoleucos conservation. The species is relatively wide-ranging, legally protected, and resilient to regional anthropic threats. However, the hydroelectric schemes and the improvement of the road system in southern Amazonia pose an imminent threat to the species

    Local hydrological conditions influence tree diversity and composition across the Amazon basin

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    Tree diversity and composition in Amazonia are known to be strongly determined by the water supplied by precipitation. Nevertheless, within the same climatic regime, water availability is modulated by local topography and soil characteristics (hereafter referred to as local hydrological conditions), varying from saturated and poorly drained to well-drained and potentially dry areas. While these conditions may be expected to influence species distribution, the impacts of local hydrological conditions on tree diversity and composition remain poorly understood at the whole Amazon basin scale. Using a dataset of 443 1-ha non-flooded forest plots distributed across the basin, we investigate how local hydrological conditions influence 1) tree alpha diversity, 2) the community-weighted wood density mean (CWM-wd) – a proxy for hydraulic resistance and 3) tree species composition. We find that the effect of local hydrological conditions on tree diversity depends on climate, being more evident in wetter forests, where diversity increases towards locations with well-drained soils. CWM-wd increased towards better drained soils in Southern and Western Amazonia. Tree species composition changed along local soil hydrological gradients in Central-Eastern, Western and Southern Amazonia, and those changes were correlated with changes in the mean wood density of plots. Our results suggest that local hydrological gradients filter species, influencing the diversity and composition of Amazonian forests. Overall, this study shows that the effect of local hydrological conditions is pervasive, extending over wide Amazonian regions, and reinforces the importance of accounting for local topography and hydrology to better understand the likely response and resilience of forests to increased frequency of extreme climate events and rising temperatures

    Geographic patterns of tree dispersal modes in Amazonia and their ecological correlates

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    Aim: To investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and hydrochory). We examined if the proportional abundance of these dispersal modes could be explained by the availability of dispersal agents (disperser-availability hypothesis) and/or the availability of resources for constructing zoochorous fruits (resource-availability hypothesis). Time period: Tree-inventory plots established between 1934 and 2019. Major taxa studied: Trees with a diameter at breast height (DBH) ≥ 9.55 cm. Location: Amazonia, here defined as the lowland rain forests of the Amazon River basin and the Guiana Shield. Methods: We assigned dispersal modes to a total of 5433 species and morphospecies within 1877 tree-inventory plots across terra-firme, seasonally flooded, and permanently flooded forests. We investigated geographic patterns in the proportional abundance of dispersal modes. We performed an abundance-weighted mean pairwise distance (MPD) test and fit generalized linear models (GLMs) to explain the geographic distribution of dispersal modes. Results: Anemochory was significantly, positively associated with mean annual wind speed, and hydrochory was significantly higher in flooded forests. Dispersal modes did not consistently show significant associations with the availability of resources for constructing zoochorous fruits. A lower dissimilarity in dispersal modes, resulting from a higher dominance of endozoochory, occurred in terra-firme forests (excluding podzols) compared to flooded forests. Main conclusions: The disperser-availability hypothesis was well supported for abiotic dispersal modes (anemochory and hydrochory). The availability of resources for constructing zoochorous fruits seems an unlikely explanation for the distribution of dispersal modes in Amazonia. The association between frugivores and the proportional abundance of zoochory requires further research, as tree recruitment not only depends on dispersal vectors but also on conditions that favour or limit seedling recruitment across forest types

    Geography and ecology shape the phylogenetic composition of Amazonian tree communities

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    AimAmazonia hosts more tree species from numerous evolutionary lineages, both young and ancient, than any other biogeographic region. Previous studies have shown that tree lineages colonized multiple edaphic environments and dispersed widely across Amazonia, leading to a hypothesis, which we test, that lineages should not be strongly associated with either geographic regions or edaphic forest types.LocationAmazonia.TaxonAngiosperms (Magnoliids; Monocots; Eudicots).MethodsData for the abundance of 5082 tree species in 1989 plots were combined with a mega-phylogeny. We applied evolutionary ordination to assess how phylogenetic composition varies across Amazonia. We used variation partitioning and Moran's eigenvector maps (MEM) to test and quantify the separate and joint contributions of spatial and environmental variables to explain the phylogenetic composition of plots. We tested the indicator value of lineages for geographic regions and edaphic forest types and mapped associations onto the phylogeny.ResultsIn the terra firme and várzea forest types, the phylogenetic composition varies by geographic region, but the igapó and white-sand forest types retain a unique evolutionary signature regardless of region. Overall, we find that soil chemistry, climate and topography explain 24% of the variation in phylogenetic composition, with 79% of that variation being spatially structured (R2 = 19% overall for combined spatial/environmental effects). The phylogenetic composition also shows substantial spatial patterns not related to the environmental variables we quantified (R2 = 28%). A greater number of lineages were significant indicators of geographic regions than forest types.Main ConclusionNumerous tree lineages, including some ancient ones (>66 Ma), show strong associations with geographic regions and edaphic forest types of Amazonia. This shows that specialization in specific edaphic environments has played a long-standing role in the evolutionary assembly of Amazonian forests. Furthermore, many lineages, even those that have dispersed across Amazonia, dominate within a specific region, likely because of phylogenetically conserved niches for environmental conditions that are prevalent within regions
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