1,016 research outputs found

    Oxygen uptake and denitrification in soil aggregates

    Get PDF
    A mathematical model of oxygen uptake by bacteria in agricultural soils is presented with the goal of predicting anaerobic regions in which denitrification occurs. In an environment with a plentiful supply of oxygen, microorganisms consume oxygen through normal respiration. When the local oxygen concentration falls below a threshold level, denitrification may take place leading to the release of nitrous oxide, a potent agent for global warming. A two-dimensional model is presented in which one or more circular soil aggregates are located at a distance below the ground-level at which the prevailing oxygen concentration is prescribed. The level of denitrification is estimated by computing the area of any anaerobic cores which may develop in the interior of the aggregates. The oxygen distribution throughout the model soil is calculated first for an aggregated soil for which the ratio of the oxygen diffusivities between an aggregate and its surround is small via an asymptotic analysis. Second, the case of a non-aggregated soil featuring one or more microbial hotspots, for which the diffusion ratio is arbitrary, is examined numerically using the boundary-element method. Calculations with multiple aggregates demonstrate a sheltering effect whereby some aggregates receive less oxygen than their neighbours. In the case of an infinite regular triangular network representing an aggregated soil, it is shown that there is an optimal inter-aggregate spacing which minimises the total anaerobic core area

    The Epidemiology and Clinical Spectrum of Melioidosis: 540 Cases from the 20 Year Darwin Prospective Study

    Get PDF
    Melioidosis is an occupationally and recreationally acquired infection important in Southeast Asia and northern Australia. Recently cases have been reported from more diverse locations globally. The responsible bacterium, Burkholderia pseudomallei, is considered a potential biothreat agent. Risk factors predisposing to melioidosis are well recognised, most notably diabetes. The Darwin prospective melioidosis study has identified 540 cases of melioidosis over 20 years and analysis of the epidemiology and clinical findings provides important new insights into this disease. Risk factors identified in addition to diabetes, hazardous alcohol use and chronic renal disease include chronic lung disease, malignancies, rheumatic heart disease, cardiac failure and age ≥50 years. Half of patients presented with pneumonia and septic shock was common (21%). The decrease in mortality from 30% in the first 5 years of the study to 9% in the last five years is attributed to earlier diagnosis and improvements in intensive care management. Of the 77 fatal cases (14%), all had known risk factors for melioidosis. This supports the most important conclusion of the study, which is that melioidosis is very unlikely to kill a healthy person, provided the infection is diagnosed early and resources are available to provide appropriate antibiotics and critical care where required

    A New Troodontid Theropod, Talos sampsoni gen. et sp. nov., from the Upper Cretaceous Western Interior Basin of North America

    Get PDF
    Troodontids are a predominantly small-bodied group of feathered theropod dinosaurs notable for their close evolutionary relationship with Avialae. Despite a diverse Asian representation with remarkable growth in recent years, the North American record of the clade remains poor, with only one controversial species--Troodon formosus--presently known from substantial skeletal remains.Here we report a gracile new troodontid theropod--Talos sampsoni gen. et sp. nov.--from the Upper Cretaceous Kaiparowits Formation, Utah, USA, representing one of the most complete troodontid skeletons described from North America to date. Histological assessment of the holotype specimen indicates that the adult body size of Talos was notably smaller than that of the contemporary genus Troodon. Phylogenetic analysis recovers Talos as a member of a derived, latest Cretaceous subclade, minimally containing Troodon, Saurornithoides, and Zanabazar. MicroCT scans reveal extreme pathological remodeling on pedal phalanx II-1 of the holotype specimen likely resulting from physical trauma and subsequent infectious processes.Talos sampsoni adds to the singularity of the Kaiparowits Formation dinosaur fauna, which is represented by at least 10 previously unrecognized species including the recently named ceratopsids Utahceratops and Kosmoceratops, the hadrosaurine Gryposaurus monumentensis, the tyrannosaurid Teratophoneus, and the oviraptorosaurian Hagryphus. The presence of a distinct troodontid taxon in the Kaiparowits Formation supports the hypothesis that late Campanian dinosaurs of the Western Interior Basin exhibited restricted geographic ranges and suggests that the taxonomic diversity of Late Cretaceous troodontids from North America is currently underestimated. An apparent traumatic injury to the foot of Talos with evidence of subsequent healing sheds new light on the paleobiology of deinonychosaurians by bolstering functional interpretations of prey grappling and/or intraspecific combat for the second pedal digit, and supporting trackway evidence indicating a minimal role in weight bearing

    National Income and Income Inequality, Family Affluence and Life Satisfaction Among 13 year Old Boys and Girls: A Multilevel Study in 35 Countries

    Get PDF
    Adolescence is a critical period where many patterns of health and health behaviour are formed. The objective of this study was to investigate cross-national variation in the relationship between family affluence and adolescent life satisfaction, and the impact of national income and income inequality on this relationship. Data from the 2006 Health Behaviour in School-aged Children: WHO collaborative Study (N = 58,352 across 35 countries) were analysed using multilevel linear and logistic regression analyses for outcome measures life satisfaction score and binary high/low life satisfaction. National income and income inequality were associated with aggregated life satisfaction score and prevalence of high life satisfaction. Within-country socioeconomic inequalities in life satisfaction existed even after adjustment for family structure. This relationship was curvilinear and varied cross-nationally. Socioeconomic inequalities were greatest in poor countries and in countries with unequal income distribution. GDP (PPP US$) and Gini did not explain between country variance in socioeconomic inequalities in life satisfaction. The existence of, and variation in, within-country socioeconomic inequalities in adolescent life satisfaction highlights the importance of identifying and addressing mediating factors during this life stage

    Alcohol Induces Sensitization to Gluten in Genetically Susceptible Individuals: A Case Control Study

    Get PDF
    Background: The mechanisms of cerebellar degeneration attributed to prolonged and excessive alcohol intake remain unclear. Additional or even alternative causes of cerebellar degeneration are often overlooked in suspected cases of alcohol-related ataxia. The objectives of this study were two fold: (1) to investigate the prevalence of gluten-related serological markers in patients with alcohol-related ataxia and; (2) to compare the pattern of brain involvement on magnetic resonance imaging between patients with alcohol and gluten ataxias. Materials & Methods: Patients diagnosed with alcohol and gluten ataxias were identified from a retrospective review of patients attending a tertiary clinic. HLA genotype and serological markers of gluten-related disorders were recorded. Cerebellar volumetry, MR spectroscopy and voxel-based morphometric analyses were performed on patients and compared with matched control data. Results: Of 904 registered patients, 104 had alcohol ataxia and 159 had gluten ataxia. 61% of the alcohol ataxia group and 70% of the gluten ataxia group had HLA DQ2/DQ8 genotype compared to 30% in healthy local blood donors. 44% of patients with alcohol ataxia had antigliadin antibodies compared to 12% in the healthy local population and 10% in patients with genetically confirmed ataxias. None of the patients with alcohol ataxia and antigliadin antibodies had celiac disease compared to 40% in patients with gluten ataxia. The pattern of structural brain abnormality in patients with alcohol ataxia who had antigliadin antibodies differed from gluten ataxia and was identical to that of alcohol ataxia. Conclusions: Alcohol related cerebellar degeneration may, in genetically susceptible individuals, induce sensitization to gluten. Such sensitization may result from a primary cerebellar insult, but a more systemic effect is also possible. The duration and amount of exposure to alcohol may not be the only factors responsible for the cerebellar insult

    Socioeconomic differences in adolescents’ smoking: a comparison between Finland and Beijing, China

    Get PDF
    Background: Various studies have demonstrated the associations between socioeconomic status (SES) and health and health behaviour among adolescents. However, few studies have compared the socioeconomic difference in adolescent smoking between countries with different stage of smoking. The purpose of this study was to examine and compare the relationship between socioeconomic status (SES) and adolescent smoking in Beijing, China and Finland through the Health Behaviour in School-aged Children (HBSC) study. Methods: The data used in this study were derived from the Chinese HBSC linked project survey 2008 in Beijing and the Finnish HBSC survey 2006. The final sample included 2005 Chinese and 1685 Finnish 15-year-old schoolchildren. The associations between Family Affluence Scale (FAS), as the SES measure, and adolescents’ smoking behaviour, including ever smoked, weekly smoking and the early onset of smoking were examined separately in two countries through binary logistic regression. Results: Compared to students from the high FAS group, Chinese boys from the low FAS group were more likely to report having ever smoked (OR = 2.12, 95 % CI = 1.49–3.01) and being early onset of smoking (OR = 2.17, 95 % CI = 1. 44–3.26). Finnish girls from the low FAS group were more likely to report being weekly smokers (OR = 1.68, 95 % CI = 1. 07–2.65). No significant difference was found for Chinese girls and Finnish boys. Conclusions: This study indicated different patterns of socioeconomic difference in smoking between Chinese and Finnish adolescents by gender and by smoking behaviour, which suggests that socioeconomic inequalities in smoking are different among adolescents in countries with different stage of smoking. Country specific policies and interventions for different target groups should be encouraged and designed for reducing the prevalence of adolescents’ smoking.peerReviewe

    CHIMPS: Physical properties of molecular clumps across the inner Galaxy

    Get PDF
    The latest generation of high-angular-resolution unbiased Galactic plane surveys in molecular-gas tracers are enabling the interiors of molecular clouds to be studied across a range of environments. The CO Heterodyne Inner MilkyWay Plane Survey (CHIMPS) simultaneously mapped a sector of the inner Galactic plane, within 27:8 . 46:2 and jbj 0: 5, in 13CO (3-2) and C18O (3-2) at an angular resolution of 15 arcsec. The combination of the CHIMPS data with 12CO (3-2) data from the CO High Resolution Survey (COHRS) has enabled us to perform a voxel-by-voxel local-thermodynamic-equilibrium (LTE) analysis, determining the excitation temperature, optical depth, and column density of 13CO at each; b; v position. Distances to discrete sources identified by FELLWALKER in the 13CO (3-2) emission maps were determined, allowing the calculation of numerous physical properties of the sources, and we present the first source catalogues in this paper.We find that, in terms of size and density, the CHIMPS sources represent an intermediate population between large-scale molecular clouds identified by CO and dense clumps seen in thermal dust continuum emission, and therefore represent the bulk transition from the diffuse to the dense phase of molecular gas.We do not find any significant systematic variations in the masses, column densities, virial parameters, mean excitation temperature, or the turbulent pressure over the range of Galactocentric distance probed, but we do find a shallow increase in the mean volume density with increasing Galactocentric distance. We find that inter-arm clumps have significantly narrower linewidths, and lower virial parameters and excitation temperatures than clumps located in spiral arms. When considering the most reliable distance-limited subsamples, the largest variations occur on the clump-to-clump scale, echoing similar recent studies that suggest that the star-forming process is largely insensitive to the Galactic-scale environment, at least within the inner disc
    • …
    corecore