Nitrification represents the bottle-neck of sheep urine patch N2O emissions from extensively grazed organic soils

Extensively grazed grasslands are understudied in terms of their contribution to greenhouse gas (GHG) emissions from livestock production. Mountains, moorlands and heath occupy 18% of the UK land area, however, in situ studies providing high frequency N2O emissions from sheep urine deposited to such areas are lacking. Organic soils typical of these regions may provide substrates for denitrification-related N2O emissions, however, acidic and anoxic conditions may inhibit nitrification (and associated emissions from nitrification and denitrification). We hypothesised urine N2O-N emission factors (EFs) would be lower than the UK country-specific and IPCC default value for urine, which is based on lowland measurements. Using automated GHG sampling chambers, N2O emissions were determined from real sheep urine (930 kg N ha−1) and artificial urine (920 kg N ha−1) applied in summer, and from an artificial urine treatment (1120 kg N ha−1) and a combined NO3− and glucose treatment (106 kg N ha−1; 213 kg C ha−1) in autumn. The latter treatment provided an assessment of the soils capacity for denitrification under non-substrate limiting conditions. The artificial urine-N2O EF was 0.01 ± 0.00% of the N applied in summer and 0.00 ± 0.00% of the N applied in autumn. The N2O EF for real sheep urine applied in summer was 0.01 ± 0.02%. A higher flux was observed in only one replicate of the real urine treatment, relating to one chamber where an increase in soil solution NO3− was observed. No lag phase in N2O emission was evident following application of the NO3− and glucose treatment, which emitted0.69 ± 0.15% of the N applied. This indicates nitrification rates are the bottle-neck for N2O emissions in upland organic soils.We calculated the potential impact of using hill-grazing specific urine N2O EFs on the UK inventory of N2O emissions from sheep excreta, and found a reduction of ca. 43% in comparison to the use of a country-specific excretal EF

Researchers' experiences of the design and conduct challenges associated with parallel-group cluster-randomised trials and views on a novel open-cohort design

BACKGROUND: Two accepted designs exist for parallel-group cluster-randomised trials (CRTs). Closed-cohort designs follow the same individuals over time with a single recruitment period before randomisation, but face challenges in settings with high attrition. (Repeated) cross-sectional designs recruit at one or more timepoints before and/or after randomisation, collecting data from different individuals present in the cluster at these timepoints, but are unsuitable for assessment of individual change over time. An 'open-cohort' design allows individual follow-up with recruitment before and after cluster-randomisation, but little literature exists on acceptability to inform their use in CRTs. AIM: To document the views and experiences of expert trialists to identify: a) Design and conduct challenges with established parallel-group CRT designs,b) Perceptions of potential benefits and barriers to implementation of open-cohort CRTs,c) Methods for minimising, and investigating the impact of, bias in open-cohort CRTs. METHODS: Qualitative consultation via two expert workshops including triallists (n = 24) who had worked on CRTs over a range of settings. Workshop transcripts were analysed using Descriptive Thematic Analysis utilising inductive and deductive coding. RESULTS: Two central organising concepts were developed. Design and conduct challenges with established CRT designs confirmed that current CRT designs are unable to deal with many of the complex research and intervention circumstances found in some trial settings (e.g. care homes). Perceptions of potential benefits and barriers of open cohort designs included themes on: approaches to recruitment; data collection; analysis; minimising/investigating the impact of bias; and how open-cohort designs might address or present CRT design challenges. Open-cohort designs were felt to provide a solution for some of the challenges current CRT designs present in some settings. CONCLUSIONS: Open-cohort CRT designs hold promise for addressing the challenges associated with standard CRT designs. Research is needed to provide clarity around definition and guidance on application.</p

A 3-component extension of the Camassa-Holm hierarchy

We introduce a bi-Hamiltonian hierarchy on the loop-algebra of sl(2) endowed with a suitable Poisson pair. It gives rise to the usual CH hierarchy by means of a bi-Hamiltonian reduction, and its first nontrivial flow provides a 3-component extension of the CH equation.Comment: 15 pages; minor changes; to appear in Letters in Mathematical Physic

Meta-analysis of global livestock urine-derived nitrous oxide emissions from agricultural soils

Nitrous oxide (N2O) is an air pollutant of major environmental concern, with agriculture representing 60% of anthropogenic global N2O emissions. Much of the N2O emissions from livestock production systems result from transformation of N deposited to soil within animal excreta. There exists a substantial body of literature on urine patch N2O dynamics, we aimed to identify key controlling factors influencing N2O emissions and to aid understanding of knowledge gaps to improve GHG reporting and prioritise future research. We conducted an extensive literature review and random effect meta-analysis (using REML) of results to identify key relationships between multiple potential independent factors and global N2O emissions factors (EFs) from urine patches. Mean air temperature, soil pH and ruminant animal species (sheep or cow) were significant factors influencing the EFs reviewed. However, several factors that are known to influence N2O emissions, such as animal diet and urine composition, could not be considered due to the lack of reported data. The review highlighted a widespread tendency for inadequate metadata and uncertainty reporting in the published studies, as well as the limited geographical extent of investigations, which are more often conducted in temperate regions thus far. Therefore, here we give recommendations for factors that are likely to affect the EFs and should be included in all future studies, these include: soil pH and texture; experimental set-up; direct measurement of soil moisture and temperature during the study period; amount and composition of urine applied; animal type and diet; N2O emissions with a measure of uncertainty; data from a control with zero-N application and meteorological data

Optimising storage conditions and processing of sheep urine for nitrogen cycle and gaseous emission measurements from urine patches

Abstract In grazing systems, urine patches deposited by livestock are hotspots of nutrient cycling and the most important source of nitrous oxide (N2O) emissions. Studies of the effects of urine deposition, including, for example, the determination of country-specific N2O emission factors, require natural urine for use in experiments and face challenges obtaining urine of the same composition, but of differing concentrations. Yet, few studies have explored the importance of storage conditions and processing of ruminant urine for use in subsequent gaseous emission experiments. We conducted three experiments with sheep urine to determine optimal storage conditions and whether partial freeze-drying could be used to concentrate the urine, while maintaining the constituent profile and the subsequent urine-derived gaseous emission response once applied to soil. We concluded that filtering of urine prior to storage, and storage at − 20 °C best maintains the nitrogen-containing constituent profile of sheep urine samples. In addition, based on the 14 urine chemical components determined in this study, partial lyophilisation of sheep urine to a concentrate represents a suitable approach to maintain the constituent profile at a higher overall concentration and does not alter sheep urine-derived soil gaseous emissions

Reactivity of Lanthanoid Mono-Cations with Ammonia : a Combined Inductively Coupled Plasma Mass Spectrometry and Computational Investigation

International audienceThe behavior of La+, Sm+, Eu+ and Gd+ with NH3(g) and ND3(g) was studied to understand gas phase chemical reactions used for separations in the reaction cell of a quadrupole inductively coupled plasma-mass spectrometer (ICP-MS). For Ln+ = La+ and Gd+, the primary reaction channel is the formation of the LnNH+ protonated nitride leading to H2 elimination. The LnNH(NH3)1-5+ ammonia complexes of the Ln protonated nitride are further generated. Sm+ and Eu+ are less reactive: the protonated nitride is not detected, and only small amounts of Ln(NH3)0-6+ are observed. Quantum chemical calculations at the DFT, MP2, CCSD(T) and CASPT2 levels of theory were employed to explore the potential energy surfaces. For the La+ and Gd+ ions of f-block elements, the reaction pathways are composed of three steps: first the formation of LnNH3+, then the isomerization to HLnNH2+, and finally the loss of H2 associated with the formation of an Lnsingle bondN triple bond in the final product LnNH+. On the other hand, the isomerization leading to triple bond formation with H2 loss did not proceed for Sm+ and Eu+ ions

The balloon-borne large-aperture submillimeter telescope for polarimetry: BLAST-Pol

The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLAST-Pol) is a suborbital mapping experiment designed to study the role played by magnetic fields in the star formation process. BLAST-Pol is the reconstructed BLAST telescope, with the addition of linear polarization capability. Using a 1.8 m Cassegrain telescope, BLAST-Pol images the sky onto a focal plane that consists of 280 bolometric detectors in three arrays, observing simultaneously at 250, 350, and 500 um. The diffraction-limited optical system provides a resolution of 30'' at 250 um. The polarimeter consists of photolithographic polarizing grids mounted in front of each bolometer/detector array. A rotating 4 K achromatic half-wave plate provides additional polarization modulation. With its unprecedented mapping speed and resolution, BLAST-Pol will produce three-color polarization maps for a large number of molecular clouds. The instrument provides a much needed bridge in spatial coverage between larger-scale, coarse resolution surveys and narrow field of view, and high resolution observations of substructure within molecular cloud cores. The first science flight will be from McMurdo Station, Antarctica in December 2010.Comment: 14 pages, 9 figures Submitted to SPIE Astronomical Telescopes and Instrumentation Conference 201

Clinically Valuable Quality Control for PET/MRI Systems:Consensus Recommendation From the HYBRID Consortium

International audienceQuality control (QC) of medical imaging devices is essential to ensure their proper function and to gain accurate and quantitative results. Therefore, several international bodies have published QC guidelines and recommendations for a wide range of imaging modalities to ensure adequate performance of the systems. Hybrid imaging systems such as positron emission tomography/computed tomography (PET/CT) or PET/magnetic resonance imaging (PET/MRI), in particular, present additional challenges caused by differences between the combined modalities. However, despite the increasing use of this hybrid imaging modality in recent years, there are no dedicated QC recommendations for PET/MRI. Therefore, this work aims at collecting information on QC procedures across a European PET/MRI network, presenting quality assurance procedures implemented by PET/MRI vendors and achieving a consensus on PET/MRI QC procedures across imaging centers. Users of PET/MRI systems at partner sites involved in the HYBRID consortium were surveyed about local frequencies of QC procedures for PET/MRI. Although all sites indicated that they perform vendor-specific daily QC procedures, significant variations across the centers were observed for other QC tests and testing frequencies. Likewise, variations in available recommendations and guidelines and the QC procedures implemented by vendors were found. Based on the available information and our clinical expertise within this consortium, we were able to propose a minimum set of PET/MRI QC recommendations including the daily QC, cross-calibration tests, and an image quality (IQ) assessment for PET and coil checks and MR image quality tests for MRI. Together with regular checks of the PET-MRI alignment, proper PET/MRI performance can be ensured