809 research outputs found

    Incorporating organic matter alters soil greenhouse gas emissions and increases grain yield in a semi-arid climate

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    © 2016 The Authors Increasing soil organic matter (OM) is promoted as a strategy for improving the resilience of coarse-textured cropping soils in semi-arid climates. While increasing soil OM can benefit crop productivity, it can also enhance nitrous oxide (N2O) emissions in temperate climates. Our objective was to investigate if increasing soil OM affected soil greenhouse gas (GHG) fluxes and grain production in a semi-arid region in south-western Australia. We firstly measured N2O and methane (CH4) fluxes from a free-draining sandy soil with contrasting soil OM content for 2.5 years using automated soil chambers. The randomized block design included two OM additions (no OM, plus OM) by two nitrogen (N) fertilizer rates (0, 0N; 100 kg N ha-1 yr-1, +N) by three replicate plots. Organic matter (chaff) had been applied to the plus OM treatments every three years since 2003, with 80 t OM ha-1applied in total. Secondly, we investigated the interaction between soil OM content and N fertilizer addition on grain yield for two growing seasons. The randomized split-plot design included two OM treatments by five N fertilizer rates (0, 25, 50, 75 and 100 kg N ha-1), by three replicates. Increasing soil OM increased grain yields and soil mineral N, but also enhanced soil N2O emissions. Nitrous oxide emissions were low by international standards (<0.12% of the N fertilizer applied), with total N2O emissions after two years ranked: plus OM (+N; 427 g N2O-N ha-1) > plus OM (0N; 194 g N2O-N ha-1) > no OM (+N; 41 g N2O-N ha-1) = no OM (0N; 14 g N2O-N ha-1). Increasing soil OM also decreased CH4uptake by 30%. Management practices that increase soil OM in sandy-textured rainfed, cropping soils in semi-arid regions should be encouraged as they can improve grain yield without substantial increases in soil N2O or CH4emissions

    Differential vaginal expression of interleukin-1 system cytokines in the presence of Mycoplasma hominis and Ureaplasma urealyticum in pregnant women.

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    OBJECTIVE: The genital mycoplasmas, Ureaplasma urealyticum and Mycoplasma hominis, are commonly identified in the vagina of healthy pregnant women. However, these microorganisms are the most common isolates from the amniotic fluids of women in preterm labor. The mechanisms responsible for vaginal colonization and ascent to the uterus remain undetermined. We evaluated the association between U. urealyticum and M. hominis vaginal colonization and the presence of pro-inflammatory and anti-inflammatory interleukin-1 system components in asymptomatic pregnant women of different ethnicities. METHODS: Vaginal specimens, obtained from 224 first trimester pregnant women, were assayed for interleukin-1beta (IL-1beta) and IL-1 receptor antagonist (IL-1ra) concentrations by ELISA. U. urealyticum and M. hominis vaginal colonization were identified by polymerase chain reaction (PCR). RESULTS: Vaginal colonization with M. hominis was identified in 37 (16.5%) women, and was more prevalent in black (18.9%) and Hispanic (20.9%) than in white (4.2%) women (p = 0.01). U. urealyticum was present in 84 (37.5%) women and there was no ethnic disparity in its detection. M. hominis colonization was associated with elevated median vaginal IL-1beta concentrations in both black women (p = 0.02) and Hispanic women (p = 0.04), and was unrelated to vaginal IL-1ra concentrations. In marked contrast, U. urealyticum colonization was associated with elevations in vaginal IL-1ra levels, but not with IL-1beta concentrations, in black women (p = 0.02) and Hispanic women (p < 0.0001) and marginally in white women (p = 0.06). CONCLUSION: M. hominis colonization in healthy pregnant women is associated with localized pro-inflammatory immune activation, while U. urealyticum colonization is associated with immune suppression

    A Repeated Measures Experiment of Green Exercise to Improve Self-Esteem in UK School Children

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    Exercising in natural, green environments creates greater improvements in adult's self-esteem than exercise undertaken in urban or indoor settings. No comparable data are available for children. The aim of this study was to determine whether so called 'green exercise' affected changes in self-esteem; enjoyment and perceived exertion in children differently to urban exercise. We assessed cardiorespiratory fitness (20 m shuttle-run) and self-reported physical activity (PAQ-A) in 11 and 12 year olds (n = 75). Each pupil completed two 1.5 mile timed runs, one in an urban and another in a rural environment. Trials were completed one week apart during scheduled physical education lessons allocated using a repeated measures design. Self-esteem was measured before and after each trial, ratings of perceived exertion (RPE) and enjoyment were assessed after completing each trial. We found a significant main effect (F (1,74), = 12.2, p<0.001), for the increase in self-esteem following exercise but there was no condition by exercise interaction (F (1,74), = 0.13, p = 0.72). There were no significant differences in perceived exertion or enjoyment between conditions. There was a negative correlation (r = -0.26, p = 0.04) between habitual physical activity and RPE during the control condition, which was not evident in the green exercise condition (r = -0.07, p = 0.55). Contrary to previous studies in adults, green exercise did not produce significantly greater increases in self-esteem than the urban exercise condition. Green exercise was enjoyed more equally by children with differing levels of habitual physical activity and has the potential to engage less active children in exercise. © 2013 Reed et al

    Coulomb scattering in a 2D interacting electron gas and production of EPR pairs

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    We propose a setup to generate non-local spin-EPR pairs via pair collisions in a 2D interacting electron gas, based on constructive two-particle interference in the spin singlet channel at the pi/2 scattering angle. We calculate the scattering amplitude via the Bethe-Salpeter equation in the ladder approximation and small r_s limit, and find that the Fermi sea leads to a substantial renormalization of the bare scattering process. From the scattering length we estimate the current of spin-entangled electrons and show that it is within experimental reach.Comment: 4 page

    Walks4work: Rationale and study design to investigate walking at lunchtime in the workplace setting

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    Background: Following recruitment of a private sector company, an 8week lunchtime walking intervention was implemented to examine the effect of the intervention on modifiable cardiovascular disease risk factors, and further to see if walking environment had any further effect on the cardiovascular disease risk factors. Methods. For phase 1 of the study participants were divided into three groups, two lunchtime walking intervention groups to walk around either an urban or natural environment twice a week during their lunch break over an 8week period. The third group was a waiting-list control who would be invited to join the walking groups after phase 1. In phase 2 all participants were encouraged to walk during their lunch break on self-selecting routes. Health checks were completed at baseline, end of phase 1 and end of phase 2 in order to measure the impact of the intervention on cardiovascular disease risk. The primary outcome variables of heart rate and heart rate variability were measured to assess autonomic function associated with cardiovascular disease. Secondary outcome variables (Body mass index, blood pressure, fitness, autonomic response to a stressor) related to cardiovascular disease were also measured. The efficacy of the intervention in increasing physical activity was objectively monitored throughout the 8-weeks using an accelerometer device. Discussion. The results of this study will help in developing interventions with low researcher input with high participant output that may be implemented in the workplace. If effective, this study will highlight the contribution that natural environments can make in the reduction of modifiable cardiovascular disease risk factors within the workplace. © 2012 Brown et al.; licensee BioMed Central Ltd

    Free-moving Quantitative Gamma-ray Imaging

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    The ability to map and estimate the activity of radiological source distributions in unknown three-dimensional environments has applications in the prevention and response to radiological accidents or threats as well as the enforcement and verification of international nuclear non-proliferation agreements. Such a capability requires well-characterized detector response functions, accurate time-dependent detector position and orientation data, an algorithmic understanding of the surrounding 3D environment, and appropriate image reconstruction and uncertainty quantification methods. We have previously demonstrated 3D mapping of gamma-ray emitters with free-moving detector systems on a relative intensity scale using a technique called Scene Data Fusion (SDF). Here we characterize the detector response of a multi-element gamma-ray imaging system using experimentally benchmarked Monte Carlo simulations and perform 3D mapping on an absolute intensity scale. We present experimental reconstruction results from hand-carried and airborne measurements with point-like and distributed sources in known configurations, demonstrating quantitative SDF in complex 3D environments.Comment: 19 pages, 5 figures, 4 supplementary figures, submitted to Scientific Reports - Natur

    The Murchison Widefield Array: Design Overview

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    The Murchison Widefield Array (MWA) is a dipole-based aperture array synthesis telescope designed to operate in the 80-300 MHz frequency range. It is capable of a wide range of science investigations, but is initially focused on three key science projects. These are detection and characterization of 3-dimensional brightness temperature fluctuations in the 21cm line of neutral hydrogen during the Epoch of Reionization (EoR) at redshifts from 6 to 10, solar imaging and remote sensing of the inner heliosphere via propagation effects on signals from distant background sources,and high-sensitivity exploration of the variable radio sky. The array design features 8192 dual-polarization broad-band active dipoles, arranged into 512 tiles comprising 16 dipoles each. The tiles are quasi-randomly distributed over an aperture 1.5km in diameter, with a small number of outliers extending to 3km. All tile-tile baselines are correlated in custom FPGA-based hardware, yielding a Nyquist-sampled instantaneous monochromatic uv coverage and unprecedented point spread function (PSF) quality. The correlated data are calibrated in real time using novel position-dependent self-calibration algorithms. The array is located in the Murchison region of outback Western Australia. This region is characterized by extremely low population density and a superbly radio-quiet environment,allowing full exploitation of the instrumental capabilities.Comment: 9 pages, 5 figures, 1 table. Accepted for publication in Proceedings of the IEE
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