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Background Children with HIV will be on antiretroviral therapy (ART) longer than adults, and therefore the durability of first-line ART and timing of switch to second-line are key questions. We assess the long-term outcome of protease inhibitor and non-nucleoside reverse transcriptase inhibitor (NNRTI) first-line ART and viral load switch criteria in children. Methods In a randomised open-label factorial trial, we compared effectiveness of two nucleoside reverse transcriptase inhibitors (NRTIs) plus a protease inhibitor versus two NRTIs plus an NNRTI and of switch to second-line ART at a viral load of 1000 copies per mL versus 30,000 copies per mL in previously untreated children infected with HIV from Europe and North and South America. Random assignment was by computer-generated sequentially numbered lists stratified by age, region, and by exposure to perinatal ART. Primary outcome was change in viral load between baseline and 4 years. Analysis was by intention to treat, which we defined as all patients that started treatment. This study is registered with ISRCTN, number ISRCTN73318385. Findings Between Sept 25, 2002, and Sept 7, 2005, 266 children (median age 6.5 years; IQR 2.8-12.9) were randomly assigned treatment regimens: 66 to receive protease inhibitor and switch to second-line at 1000 copies per mL (PI-low), 65 protease inhibitor and switch at 30,000 copies per mL (PI-higher), 68 NNRTI and switch at 1000 copies per mL (NNRTI-low), and 67 NNRTI and switch at 30,000 copies per mL (NNRTI-higher). Median follow-up was 5.0 years (IQR 4.2-6.0) and 188 (71%) children were on first-line ART at trial end. At 4 years, mean reductions in viral load were -3.16 log(10) copies per mL for protease inhibitors versus -3.31 log(10) copies per mL for NNRTIs (difference -0.15 log(10) copies per mL, 95% CI -0.41 to 0.11; p=0.26), and -3.26 log(10) copies per mL for switching at the low versus -3.20 log(10) copies per mL for switching at the higher threshold (difference 0.06 log(10) copies per mL, 95% CI -0.20 to 0.32; p=0.56). Protease inhibitor resistance was uncommon and there was no increase in NRTI resistance in the PI-higher compared with the PI-low group. NNRTI resistance was selected early, and about 10% more children accumulated NRTI mutations in the NNRTI-higher than the NNRTI-low group. Nine children had new CDC stage-C events and 60 had grade 3/4 adverse events; both were balanced across randomised groups. Interpretation Good long-term outcomes were achieved with all treatments strategies. Delayed switching of protease-inhibitor-based ART might be reasonable where future drug options are limited, because the risk of selecting for NRTI and protease-inhibitor resistance is low. Funding Paediatric European Network for Treatment of AIDS (PENTA) and Pediatric AIDS Clinical Trials Group (PACTG/IMPAACT).

Using cryo-SEM with EDX fundamental structural and mechanical properties of the moss Ceratodon purpureus (Hedw.) Brid. were studied in relation to tolerance of freezing temperatures. In contrast to more complex plants, no ice accumulated within the moss during the freezing event. External ice induced desiccation with the response being a function of cell type; water-filled hydroid cells cavitated and were embolized at -4 °C while parenchyma cells of the inner cortex exhibited cytorrhysis, decreasing to ∼ 20% of their original volume at a nadir temperature of -20 °C. Chlorophyll fluorescence showed that these winter acclimated mosses displayed no evidence of damage after thawing from -20 °C while GCMS showed that sugar concentrations were not sufficient to confer this level of freezing tolerance. In addition, differential scanning calorimetry showed internal ice nucleation occurred in hydrated moss at ∼-12 °C while desiccated moss showed no evidence of freezing with lowering of nadir temperature to -20 °C. Therefore the rapid dehydration of the moss provides an elegantly simple solution to the problem of freezing; remove that which freezes.

To study the sustainability of arable agricultural systems we examined a wide range of biological, physical and chemical properties associated with changes in soil quality. We integrated these using a qualitative multi-attribute model supported by the software tool DEXi to achieve a holistic estimation of soil quality. We tested the relative changes in soil quality attributes resulting from the incorporation of cattle slurry or green-waste compost, or from including a ley phase in the production of arable crops. We measured: abundances and biodiversity of the soil biota, physical properties and nutrient concentrations; twice in 2006 and thrice in 2007. These data were used to generate a model of soil quality, which showed that the addition of organic matter or a ley phase did increase soil quality. However, to fully understand the soil system results should be derived from a number of functionally related observations as there were opposing trends in individual observations. Increases in some beneficial attributes (such as decomposition, soil nutrient status and physical condition) were associated with an increased risk of nutrient losses from leaching and gaseous emissions. Assessing soil quality with only a few indicators may not identify these trade-offs. The multi-attribute modelling approach could identify the pathways responsible for changes in soil quality and identify possible environmentally detrimental effects.

CITATION: Rebeiro, B. M., et al. 2018. Nuclear structure studies relevant to ¹³⁶Xe ββ decay. Journal of Physics: Conference Series, 1056(1):012049, doi:10.1088/1742-6596/1056/1/012049.

Individual-based clustering (IBC) methods have become increasingly popular for the characterization and delineation of genetic population units for numerous species. These methods delineate populations based on the genetic assumptions of a breeding unit which may provide a better representation of the behaviour of the species. The increasing use of IBC has resulted in the development of several analytical models all of which vary in their theoretical assumptions to infer genetic population structure. In this paper, we report a comparative strategy utilizing three IBC methods to characterize the spatial genetic structure of the boreal population of woodland caribou (Rangifer tarandus caribou) in central Canada. In addition, we implement both tests for isolation-by-distance (IBD) and frequency-based assignment tests to validate the consensus genetic clusters as defined by IBC. We also compare indirect metrics of genetic diversity and gene flow using both a priori defined herds and the IBC defined populations. Although our results show some concordance between both pre-defined herds and IBC derived genetic clusters, the IBC analyses identified a cluster that was cryptic to observation-based caribou herds and found no difference between several adjacent herds. By comparing multiple IBC methods and integrating both IBD and indirect genetic diversity metrics a posteriori, our strategy provides an effective means to delineate wildlife population structure and accurately assess genetic diversity and connectivity.

Long-term monitoring programs must use informative yet cost-effective methods. Occupancy estimates that incorporate detection probabilities are used with increasing frequency to describe species status and make management recommendations. Estimating changes in the occupancy of points over time in response to management actions or environmental changes may be especially useful for management of the Palm Springs round-tailed ground squirrel (Spermophilus tereticaudus chlorus), a subspecies covered under the Coachella Valley Multiple Species Habitat Conservation Plan and Natural Community Conservation Plan. In 2002 and 2003, we estimated occupancy and detection probability of ground squirrels across lands modeled as ground squirrel habitat by the Scientific Advisory Committee for the Habitat Conservation Plan and tested a priori hypotheses about how occupancy varied among vegetation and substrate types. In the 2003 study, we asked whether these associations were affected by winter rains after the 20...

Summary 1. Growth rate is a fundamental property of organisms. In trees, growth is indeterminate and varies in space and time depending on resource availability, genetic constraints, competition and stress from biotic and abiotic environmental factors. 2. The ratio between the abundance of RNA and DNA in the tissue has been used to indicate recent growth rates in many systems, but not for trees. We assessed the applicability of using RNA : DNA ratios for assessing intraspecific and interspecific differences in growth rates in two species of mangrove trees under field conditions. We manipulated growth by fertilizing mangrove trees over a period of 4 years and measured tree growth as increments in linear extension of tagged shoots. The C, N and P contents per unit biomass were measured to test the hypothesis that faster growing organisms require more P per unit biomass (the Growth Rate Hypothesis). 3. We found that interspecific differences in the RNA : DNA ratio clearly reflected the difference in shoot elongation rates between the species. Intraspecific differences in RNA : DNA were significantly correlated with growth rates only for Avicennia marina and not for Ceriops australis. C : N and C : P ratios were lower in trees with higher growth rates and exhibited a negative correlation with RNA : DNA ratios. 4. Our results indicate that RNA : DNA ratios can reliably predict interspecific differences in growth rates between the two mangrove species and that RNA : DNA ratios can be used as an indication of variation in growth rate for Avicennia marina. The interaction between C : N : P ratios, RNA : DNA ratios and growth rates supported the Growth Rate Hypothesis on an interspecific level, but not on an intraspecific level.

Genetic profiling using fecal samples collected noninvasively in the wild can provide managers with an alternative to live-trapping. However, before embarking on a large-scale survey, feasibility of this methodology should be assessed for the focal species. Costs associated with fecal genotyping can be high because of the need for multiple amplifications to prevent and detect errors. Assessing the relative amount of target DNA before genotyping means samples can be eliminated where error rates will be high or amplification success will be low, thereby reducing costs. We collected fecal samples from an endangered population of swift fox (Vulpes velox) and employed target-DNA quantification and a screening protocol to assess sample quality before genetic profiling. Quantification was critical in identifying samples of low quality (68%

β-glucosidase is a key enzyme in the C-cycle, and its activity is strongly influenced by soil management practices and by extrinsic factors such as weather conditions. However, the variability of β-glucosidase activity (BGa) over time and how this variability is affected by tillage and organic fertilization remain poorly elucidated. We investigated how contrasting tillage practices (zero, minimum, conventional or deep) and organic amendment application (dairy cattle slurry or green compost) govern BGa. Strong correlations (r = −0.98; p < 0.001) were found between BGa and preceding cumulative rainfall for soil without crops. Under cropped soil conditions, BGa was 53% greater under zero and minimum tillage than under ploughed treatments (p < 0.05) six years after their applications. These differences could be explained by associated effects of tillage on organic matter content, electrical conductivity and water stable aggregates. The separated organic residue experiment showed that BGa was 36% greater in soil amended with slurry than in soil amended with compost (p < 0.05) five years after their applications. Finally, the response ratio of BGa was calculated in order to study the effect size of each treatment at each sampling period. This simple strategy mitigated the variation on BGa measurements between two sampling periods, and may be applied in future studies to improve the interpretation of other potential soil quality indicators that are sensitive to seasonal changes.

Interactions of leptin and leptin receptors play crucial roles during animal development and regulation of appetite and energy balance. In this study we analyzed expression pattern of a zebrafish leptin receptor gene in both developing and adult zebrafish using in situ hybridization and Q-PCR methods. Zebrafish leptin receptor message (lepr) was detected in all embryonic and larval stages examined, and in adult zebrafish. In embryonic zebrafish, lepr was mainly expressed in the notochord. As development proceeded, lepr expression in the notochord decreased, while its expression in several other tissues, including the trunk muscles and gut, became evident. In both larval and adult brains, large lepr expressing cells were detected in similar regions of the hindbrain. In adult zebrafish, lepr expression was also observed in several other brain regions including the hypothalamic lateral tuberal nucleus, the fish homolog of the arcuate nucleus. Q-PCR experiments confirmed lepr expression in the adult fish brain, and also showed lepr expression in several adult tissues including liver, muscle and gonads. Our results showed that lepr expression was both spatially and temporally regulated.

The β-decay half lives of nuclei near the r-process path are critical information required for abundance calculations, especially those near neutron number N = 82. Specifically, the nuclei below doubly-magic 132Sn are key, and play an important role in the formation and shape of the second r-process abundance peak. The half lives in this region are challenging to measure due to the significant β-delayed neutron decay branches and the population of isomeric states with half lives comparable to the ground states. However, by measuring the time distribution of γ rays, these complications can be eliminated. This requires, however, a very effcient γ-ray spectrometer since the production of isotopes in this region is very limited. The new GRIFFIN array at TRIUMF-ISAC provides the high effciency required for these measurements. Recent improvements in the quality of the beams produced at TRIUMF, employing the IG-LIS device, are outlined, as well as the current status of the ARIEL facility. The GRIFFIN spectrometer and its use are briefly described. The experiment to measure the half lives of 128-130Cd is outlined and the results given, and some examples of the power of GRIFFIN to expand decay schemes, specifically for the decay of 128Cd to 128In, are given.

Direct reaction studies provide crucial information on nuclear structure for nuclei that are used in weak interaction and fundamental symmetry tests. Motivated by the superallowed Fermi beta-decay studies, we have investigated the structure of Cr-50 and Zn-62, the daughters of the superallowed beta(+)/EC emitters Mn-50 and Ga-62, with (p,t) reactions. For both nuclei, we reassigned the location of the first excited 0(+) state. The data for these reassignments are reviewed and limits on the possible L = 0 transfer to the previously assigned 0(2)(+) states are determined. For Cr-50, we find no evidence for the presence of a 0(+) state at 3695 keV. For Zn-62, the data allow for a possible contribution of L = 0 and L = 2, indicating a possible 0(+)/2(+) doublet of states at 2342 keV. However, this relies on an enhanced cross section at only one data point, and thus the existence of a 0(+) state at this energy is not clear. A preliminary result from a gamma-gamma angular correlation measurement following the beta(+)/EC decay of Ga-62 weakly favours the existence of a 0(+) state, but requires further study with increased statistics.

Recent performance and cost studies predict that the high PGM loadings in the electrodes of today's direct hydrogen fuel cells will prove a limiting factor in their commercial viability for automotive applications. Significant breakthroughs in electrocatalyst technology yielding materials with high activity, low cost and good durability are required. This paper reports on a collaborative effort which has focussed on the exciting core-shell oxygen reduction catalysts pioneered by Brookhaven National Laboratory. These materials promise high catalyst activity and PGM thrifting although to date, are typically fabricated by in-situ electrochemical techniques. Following the development of scalable syntheses, extensive catalyst characterisation methods have been employed to analyse and verify the success of a scaled PtML/Pd3Co/C catalyst. Although synthetic challenges remain, the scaled core-shell materials yield RDE activities of 0.72 A/mgPt, constituting an impressive 3.7x improvement in Pt activity relative to Pt/C and exceeding the 0.44 A/mgPt automotive target.

Two contrasting phases of work are described that help inform the development and requirements of a soil monitoring system: firstly, the development and application of a multi-criterion analysis of soil quality indicators grounded in the basic natural sciences; and secondly, scrutiny of the outcome of that process by a wide range of non-specialist but key stakeholders at a workshop. This process ensures that the final monitoring design meets both the scientific rigour expected from a monitoring system and as far as possible meets the aspirations of policy and regulatory stakeholders. Individual indicators of soil quality were evaluated in terms of their applicability against a number of important environmental and logistical parameters and therefore their overall fitness for purpose. These included relevance to different soil types, functions, habitats and threats to soil, the inherent variability of soil, and a range of technical aspects such as analytical complexity, precision and reproducibility of analytical results and whether a standard operating procedure (SOP) existed for the technique. A tiered approach to soil monitoring was supported by workshop delegates. This will require indicators that are suitable and effective at national, site-specific and process-level scales. In addition, the opportunities for synchronizing soil monitoring with air and water quality monitoring should be considered and the potential for integrating on-site measurements with remote methods should be researched further. It was considered by workshop attendees that soil monitoring should be rooted in pedological principles (i.e. recognizing defined soil horizons) to ensure that results can be extrapolated from individual sites and to retain flexibility.

Nitrous oxide (N2O) is a powerful greenhouse gas. The UK government is committed to reducing all greenhouse gas emissions and is required to make an inventory of the sources and emissions of these gases. Here, we extend work from a pilot study at the catchment scale reported in an earlier paper. This paper reports on the upscaling measurements of emissions to derive annual emission rates for specific combinations of soil type, land management and fertiliser practices to the national scale. Digital soil, climate and land use maps were combined within Geographic Information Systems (GIS) software. Upscaling of field emissions measurements involves adjusting measured annual N2O emissions to fit combinations of crop growth cycles, soil wetness and the amount and timing of fertiliser applications. We have also taken account of the differences in emission rates from grazed pasture land due to differences in land management between land utilised for dairy production and land utilised for beef production. Calculated annual emission rates were then spatially scaled to derive national figures through the use of a GIS modelling framework, termed NitOx. The annual emission of N2O from Scotland was determined as approximately 6 000 000 kg N yr−1 (2.8 Mt carbon dioxide (CO2) equivalents) and compares favourably with other national scale estimates such as the IPCC (1997). The combination of animal grazing, high N inputs, climatic warmth and poorly drained soils means that the south west contributes significantly to the national total N2O emissions. Localised areas of high emission can also be identified, but identification could be improved by applying this modelling approach at a larger scale. It would be beneficial to target these areas with mitigation strategies.

The successful production of organic vegetables relies heavily on mechanical weeding, flame weeding and stale seedbeds. These operations involve repeated passes by tractors. Mechanical weeding also involves regular tillage. This combination of repeated tillage and compaction changes soil structure. We studied these structural changes in two fields of organic carrots and one field of beans in eastern Scotland. Structure was described by measuring soil strength with a vane shear tester and a cone penetrometer, by measuring bulk density and by visual assessment. Under beans, vane shear strength below the growing root zone was highly variable and in some areas was high enough to restrict root growth ( > 50 kPa). The carrots were grown in beds containing crop rows separated by bare soil. The bare soil was regularly weeded mechanically. The structure of this weeded soil in the top 10 cm layer of a loam eventually became disrupted and compacted enough to deter root growth (vane shear strength of 70 kPa). In addition the topsoil and subsoil in the wheel-tracks between the beds became very compact with little distinguishable structure. This compaction extended to the subsoil and persisted into the next cropping season (cone resistance > 3 MPa at 35-50 cm depth). Reduced tillage by discing without ploughing was used to incorporate the straw used to protect the carrots overwinter and prepare the soil for the next crop. The resulting topsoil quality was poor leading to anaerobic growing conditions which restricted growth of the following crop and led to losses of the greenhouse gas nitrous oxide. The greatest threat to soil quality posed by mechanical weeding was subsoil compaction by tractor wheeling.

Contact-dependent communication between immune cells generates protection but also facilitates viral spread. Here we found that macrophages formed long-range actin-propelled conduits in response to negative factor (Nef), a human immunodeficiency virus type 1 (HIV-1) protein with immunosuppressive functions. Conduits attenuated immunoglobulin G2 (IgG2) and IgA class switching in systemic and intestinal lymphoid follicles by shuttling Nef from infected macrophages to B cells through a guanine-exchange factor-dependent pathway involving the amino-terminal anchor, central core and carboxy-terminal flexible loop of Nef. By showing stronger virus-specific IgG2 and IgA responses in patients with Nef-deficient virions, our data suggest that HIV-1 exploits intercellular 'highways' as a 'Trojan horse' to deliver Nef to B cells and evade humoral immunity systemically and at mucosal sites of entry.

Climate change is the biggest global health threat of the 21st century. Effects of climate change on health will affect most populations in the next decades and put the lives and wellbeing of billions of people at increased risk. During this century, earthﾒs average surface temperature rises are likely to exceed the safe threshold of 2ﾰC above preindustrial average temperature. Rises will be greater at higher latitudes, with medium-risk scenarios predicting 2ﾖ3ﾰC rises by 2090 and 4ﾖ5ﾰC rises in northern Canada, Greenland, and Siberia. In this report, we have outlined the major threatsﾗboth direct and indirectﾗto global health from climate change through changing patterns of disease, water and food insecurity, vulnerable shelter and human settlements, extreme climatic events, and population growth and migration. Although vector-borne diseases will expand their reach and death tolls, especially among elderly people, will increase because of heatwaves, the indirect effects of climate change on water, food security, and extreme climatic events are likely to have the biggest effect on global health.

The wave-function composition for the low-lying states in 29 Na was explored by measuring their electromagnetic properties using the Coulomb-excitation technique. A beam of 29 Na ions, postaccelerated to 70 MeV, bombarded a 110 Pd target with a rate of up to 600 particles per second at the recently commissioned ISAC-II facility at TRIUMF. Six segmented HPGe clover detectors of the TIGRESS γ -ray spectrometer were used to detect deexcitation γ rays in coincidence with scattered or recoiling charged particles in the segmented silicon detector, BAMBINO. The reduced transition matrix element | 〈 5 2 1 + | | E 2 | | 3 2 gs + 〉 | in 29 Na was derived to be 0.237(21) e b from the measured γ -ray yields for both projectile and target. This first-time measured value is consistent with the most recent Monte Carlo shell-model calculation, indicating a significant admixture of both sd and pf components in the wave function, and also providing evidence for the narrowing of the neutron s d – p f shell gap from ∼ 6 MeV for stable nuclei to ∼ 3 MeV for 29 Na.

Background With evidence of increased levels of obesity in younger children, the child-care setting is an important intervention target. Few environmental interventions exist, and none target both diet and physical activity. The Nutrition and Physical Activity Self-Assessment for Child Care (NAP SACC) intervention was developed to fill this research and practice gap. Design Randomized controlled. Setting/participants Health professionals (child-care health consultants) serving child-care centers in North Carolina were recruited ( n =30), randomly assigned into intervention or delayed-intervention control groups, and trained to implement the NAP SACC program. Up to three child-care centers were recruited ( n =84) from each consultant's existing caseload. Intervention Implemented in 2005, the NAP SACC intervention includes an environmental self-assessment, selection of areas for change, continuing education workshops, targeted technical assistance, and re-evaluation. Implementation occurred over a 6-month period. Main outcome measures An observational instrument, Environment and Policy Assessment and Observation (EPAO), provided objective evidence of intervention impact and was completed by trained research staff blinded to study assignment. Data were collected in 2005 and 2006. Statistical analyses were conducted in 2006. Results Intention-to-treat analysis results were nonsignificant. Exploratory analyses using only centers that completed most of the NAP SACC program suggest an intervention effect. Conclusions Factors in the intervention design, the fidelity of implementation, the selection of outcome measure, or a combination of these may have contributed to the lack of intervention effect observed. Because of this study's use of existing public health infrastructure and its potential for implementation, future studies should address strategies for improving effectiveness.

Sharp peaks in nitrous oxide (N2O) fluxes under no-tillage in wet conditions appear to be related to near surface soil and crop cover conditions. Here we explored some of the factors influencing tillage effects on short-term variations in gas flux so that we could learn about the mechanisms involved. Field investigations revealed that a cumulative emission of 13 kg N2O–N ha−1 over a 12-week period was possible under no-tillage for spring barley. We investigated how reducing crop cover and changing the structural arrangement of the water-filled pore space (WFPS) by short-term laboratory compaction influenced N2O and carbon dioxide (CO2) fluxes in upward and downward directions in core samples from tilled and untilled soil. Increasing the downward flux of N2O within a soil profile by changing soil or moisture conditions may increase the likelihood of its further reduction to N2 or dissolution. We took undisturbed cores from 3 to 8 cm depth, equilibrated them to −1 or −6 kPa matric potential, incubated them and measured N2O and CO2 fluxes from the upper and lower surfaces in a purpose-designed apparatus before and after compaction in an uniaxial tester. We also measured WFPS, air permeability, bulk density and air-filled porosity before and after compaction. Spring barley was tested in 1999 and winter barley in 2000. Fluxes of N2O were from 1.5 to 35 times higher from no-tilled than ploughed even where the soil was of similar bulk density. Reduction of the crop cover increased CO2 flux and could reduce N2O flux. The effects of structural changes induced by laboratory compaction on the fluxes of N2O and CO2 were not influenced greatly by the tillage and crop cover treatments. Fluxes from the upper surfaces of cores (corresponding to 3 cm soil depth, upwards direction) could be up to ∼100 times greater (N2O) or ∼8 times (CO2) than from the lower surfaces (8 cm depth, downwards direction). These differences between surfaces were greatest when N2O fluxes were very high in no-tilled soil (4.2 mg N2O–N m−2 h−1) as occurred when WFPS exceeded 80% or became blocked with water, an effect that was increased by our compaction treatment. In general N2O fluxes increased with WFPS. The production and emission of N2O were strongly influenced by the soil physical environment, the magnitude of the water-filled pore space and continuity of the air-filled pore space in particular, produced in no-till versus plough cultivation.

The value of molecular databases for unicellular eukaryotic identification and phylogenetic reconstruction is predicated on the availability of sequences and accuracy of taxonomic identifications that accompany those sequences. Biased representation of sequences is due in part to the differing ability to isolate and culture various groups of protists. Techniques that allow for parallel single-cell morphological and molecular identifications have been reported for a few groups of unicellular protists. We have sought to explore how those techniques can be adapted to work across a greater phylogenetic diversity of taxa. Twelve morphologically diverse and abundant members of limnetic microplankton, including ciliates, dinoflagellates, cryptophytes, stramenopiles, and synurophytes, were targeted for analysis. These cells were captured directly from environmental samples, identified, and prepared for sequence analyses using variations of single-cell extraction techniques depending on their size, mobility, and the absence or presence of the cell wall. The application of these techniques yielded a strong congruence between the morphological and molecular identifications of the targeted taxa. Challenges to the single-cell approach in some groups are discussed. The general ability to obtain DNA sequences and morphological descriptions from individual cells should open new avenues to studying either rare or difficult to culture taxa, even directly at the point of collection (e.g. remote locations or shipboard).

The ATLAS Muon Spectrometer incorporates 354 000 drift tubes assembled into 1200 Monitored Drift Tube (MDT) precision chambers, with a total gas volume of 723 m 3 . This MDT gas, Ar 93% and CO 2 7% at 3 bar, is cycled through the spectrometer at a rate of one total detector volume per day. Achieving the 80 μ m drift tube design resolution requires stringent gas quality control as a fundamental component of the MDT calibration program. We report on the design, deployment and performance of a dedicated MDT mini-chamber conceived for continuous monitoring and drift time calibration of the ATLAS MDT operating gas. This chamber enables measurement of the drift spectra from which gas properties relevant to MDT calibrations and stable operating conditions are determined. Located in the ATLAS gas facility at CERN, the mini-chamber produces hourly drift spectra which are automatically analyzed. Results are published online and disseminated to the ATLAS muon system conditions and calibration databases in real time.

Productivity and climate models often use a constant Q10 for plant respiration, assuming tight control of respiration by temperature. We studied the temperature response of leaf respiration of two cold climate species (the Australian tree Eucalyptus pauciflora and the subantarctic megaherb Pringlea antiscorbutica, both measured in a field setting) on a short timescale (minutes) during different times within a diel course, and on a longer timescale, using diel variations in ambient temperature. There were great variations in Q10 depending on measuring day, measuring time and measuring method. When Q10 was calculated from short-term (15 min) manipulations of leaf temperature, the resulting values were usually markedly smaller than when Q10 was calculated from measurements at ambient leaf temperatures spread over a day. While for E. pauciflora, Q10 estimates decreased with rising temperature (corroborating the concept of a temperature-dependent Q10), the opposite was the case for P. antiscorbutica. Clearly, factors other than temperature co-regulate both leaf respiration rates and temperature sensitivity and contribute to diel and seasonal variation of respiration.

Two hypotheses have been proposed to explain increases in plant nitrogen (N) and phosphorus (P) concentrations with latitude: (i) geochemical limitation to P availability in the tropics and (ii) temperature driven variation in growth rate, where greater growth rates (requiring greater nutrient levels) are needed to complete growth and reproduction within shorter growing seasons in temperate than tropical climates. These two hypotheses were assessed in one forest type, intertidal mangroves, using fertilized plots at sites between latitudes 36 masculine S and 27 masculine N. The N and P concentrations in mangrove leaf tissue increased with latitude, but there were no trends in N : P ratios. Growth rates of trees, adjusted for average minimum temperature showed a significant increase with latitude supporting the Growth Rate Hypothesis. However, support for the Geochemical Hypothesis was also strong; both photosynthetic P use efficiency and nutrient resorption efficiency decreased with increasing latitude, indicating that P was less limiting to metabolism at the higher latitudes. Our study supports the hypothesis that historically low P availability in the tropics has been an important selective pressure shaping the evolution of plant traits.

Increased awareness of the role of soil structure in defining the physical fertility or quality of soil has led to the need for a simple assessment relevant to the environmental and economic sustainability of soil productivity. A test is required that is usable by farmer, consultant and researcher alike. Here an assessment of soil structure quality (Sq) is described which is based on a visual key linked to criteria chosen to be as objective as possible. The influences of operator, tillage and crop type on Sq value were tested. The test takes 5-15 min per location and enough replicates were obtained for statistical comparison of data sets. The assessments of individual operators were influenced to an extent by differences between fields, making the use of multiple operators desirable. Differences in soil management were revealed by the test and related to differences in soil physical properties (bulk density, penetration resistance and porosity) and crop growth. Indicative thresholds of soil management are suggested. The assessment should be viewed as complementary to conventional laboratory assessments of soil structure. Visual soil structure assessment can indicate to the soil scientist where to sample and what soil measurements are likely to be worthwhile.

Although plants are more susceptible to frost damage under elevated atmospheric [CO 2 ], the importance of frost damage under future, warmer climate scenarios is unknown. Accordingly, we used a model to examine the incidence and severity of frost damage to snow gum (Eucalyptus pauciflora) in a sub-alpine region of Australia for current and future conditions using the A2 IPCC elevated CO 2 and climate change scenario. An existing model for predicting frost effects on E. pauciflora seedlings was adapted to include effects of elevated [CO 2 ] on acclimation to freezing temperatures, calibrated with field data, and applied to a study region in Victoria using climate scenario data from CSIRO's Global Climate Model C-CAM for current (1975-2004) and future (2035-2064) 30 years climate sequences. Temperatures below 0 °C were predicted to occur less frequently while the coldest temperatures (i.e. those below -8 C) were almost as common in the future as in the current climate. Both elevated [CO 2 ] and climate warming affected the timing and rates of acclimation and de-acclimation of snow gum to freezing temperatures, potentially reducing the length of time that plants are fully frost tolerant and increasing the length of the growing season. Despite fewer days when temperatures fall below 0 °C in the future, with consequently fewer damaging frosts with lower average levels of impact, individual weather sequences resulting in widespread plant mortality may still occur. Furthermore, delayed acclimation due to either warming or rising [CO 2 ] combined with an early severe frost could lead to more frost damage and higher mortality than would occur in current conditions. Effects of elevated [CO 2 ] on frost damage were greater in autumn, while warming had more effect in spring. Thus, frost damage will continue to be a management issue for plantation and forest management in regions where frosts persist.

The mechanism of activity loss in Pt and PtCo alloy systems has been investigated during 0.6 - 1.0 V and 0.6 - 1.2 V vs RHE cycling regimes using an electrochemical cell that allows electrochemical metal area (ECA) loss measurement and electrolyte sampling. Dissolution of platinum and base metal into the electrolyte was quantified using ICP-MS and TEM used to look for changes in catalyst morphology with cycles. ECA loss and base metal removal were found to be potential dependent. PtCo alloys were found to be more stable to ECA loss by Ostwald-ripening and dissolution than Pt. In terms of base metal loss the PtCo alloy was unstable and cycling was found to remove similar amounts of Co by dissolution as chemical acid leaching. Loss of Co from the surface layers of the catalyst was found to remove the enhanced stability and activity benefits of this catalyst making it more platinum like.

The CO2 tolerance exhibited by PtRu/C is known to be greater than that of PtMo/C catalysts in contrast to the trend in CO tolerance. In this manuscript the origins of these differences are investigated in a cyclic voltammetric investigation of the potential dependence of the poisoning of Pt/C, PtRu/C and PtMo/C anode catalyst electrodes in a miniature PEM fuel cell when exposed to pure CO, pure CO2, or 25% CO2 in H2. The results show that the difference in the mechanisms of improved CO tolerance, compared to a Pt/C reference catalyst, of PtRu and PtMo explain the decreased CO2 tolerance of PtMo compared to PtRu; at PtRu the mechanism is intrinsic (water activation at Ru sites), whilst at PtMo the mechanism relies on the turn-over the Mo(IV/VI) redox couple.

To meet automotive targets for fuel cell operation and allow higher temperature operation an understanding of the factors affecting carbon and platinum stability is critical. The stability of both carbons and carbon supported platinum and platinum/cobalt alloy catalysts was studied during 1.2 V versus RHE potentiostatic hold tests using carbon and catalyst coated electrodes in a three-chamber wet electrolyte cell at a range of temperatures. At 80 °C the wt% of carbon corroded increases with increasing BET area. Surface oxidation was followed electrochemically using the quinone/hydroquinone redox couple. Increasing temperature, time at 1.2 V and wt% platinum on the carbon increases surface oxidation. Although increasing temperature was shown to increase the extent of carbon corrosion, catalysing the carbon did not significantly change how much carbon was corroded. Platinum stability was investigated by electrochemical metal area loss (ECA). Platinum catalysts on commercial carbons lost more ECA with increasing temperature. A platinum/cobalt alloy on a low surface area carbon was demonstrated to be more stable to both carbon corrosion and metal area loss at temperatures up to 80 °C than platinum catalysts on commercial carbons, making this material an excellent candidate for higher temperature automotive operation.

A general technique that corrects γ -ray gated β decay-curve data for detector pulse pile-up is presented. The method includes corrections for non-zero time-resolution and energy-threshold effects in addition to a special treatment of saturating events due to cosmic rays. This technique is verified through a Monte Carlo simulation and experimental data using radioactive beams of Na 26 implanted at the center of the 8 π γ -ray spectrometer at the ISAC facility at TRIUMF in Vancouver, Canada. The β -decay half-life of Na 26 obtained from counting 1809-keV γ -ray photopeaks emitted by the daughter Mg 26 was determined to be T 1 / 2 = 1.07167 ± 0.00055 s following a 27 σ correction for detector pulse pile-up. This result is in excellent agreement with the result of a previous measurement that employed direct β counting and demonstrates the feasibility of high-precision β -decay half-life measurements through the use of high-purity germanium γ -ray detectors. The technique presented here, while motivated by superallowed-Fermi β decay studies, is general and can be used for all half-life determinations (e.g. α -, β -, X-ray, fission) in which a γ -ray photopeak is used to select the decays of a particular isotope.

The isotope separator and accelerator (ISAC) facility located at the TRIUMF laboratory in Vancouver, Canada, is one of the world’s most advanced isotope separator on-line-type radioactive ion beam facilities. An extensive γ-ray spectroscopy programme at ISAC is centred around two major research facilities: (i) the 8π γ-ray spectrometer for β-delayed γ-ray spectroscopy experiments with the low-energy beams from ISAC-I, and (ii) the next generation TRIUMF-ISAC gamma-ray escape suppressed spectrometer (TIGRESS) for in-beam experiments with the accelerated radioactive-ion beams. An overview of these facilities and recent results from the diverse programme of nuclear structure and fundamental interaction studies they support is presented.

The period after ploughing of grass–clover leys within a ley-arable rotation is when nitrogen accumulated during the ley phase is most vulnerable to loss. We investigated how ploughing date and timing of cessation of grazing before ploughing affected nitrous oxide (N2O) losses of the first cereal crop. Ploughing dates were July and October for a winter wheat pilot study and January and March for spring barley in the main experiment. Timings of cessation of grazing (main experiment only) were October, January and March. Spring barley yield, nitrogen uptake and soil mineral nitrogen were also assessed. A separate large-scale laboratory incubation was made to assess the effect of temperature and rainfall on nitrous oxide emissions and nitrate leaching under controlled conditions. Nitrous oxide emissions in the 1- to 2-month period after autumn or spring ploughing, or sowing were typically between 20 and 150 g N ha−1 day−1 and increased with temperature and rainfall. Tillage for crop establishment stimulated N2O emissions with up to 2.1 kg N ha−1 released in the month after spring tillage. Cumulative nitrous oxide emissions were greatest (∼8 kg ha−1 over 17 months) after cessation of grazing in March before March ploughing, and lowest (∼5.5 kg ha−1) after cessation of grazing in January before January ploughing. These losses were 1.2–3.9% of the N inputs. In the laboratory study, winter ploughing stimulated nitrate leaching more than nitrous oxide emissions. The optimum time of ploughing appears to be early spring when the cold restricts nitrogen mineralization initially, but sufficient nitrogen becomes available for early crop growth and satisfactory N offtake as temperature increases. Early cessation of grazing is advantageous in leaving an adequate supply of residues of good quality (narrow C:N ratio) for ploughing-in. Restricting tillage operations to cool, dry conditions, being aware of possible compaction and increasing the use of undersown grass–clover should improve the sustainability of organic farming.

The aim of this study was to quantify N2O release from temperate grassland receiving different forms of N, and to assess the importance of controlling variables in the environment. In 2002 and 2003 three organic manures (sewage sludge pellets, poultry manure and cattle slurry) and two mineral fertilisers (NH4NO3 and urea) were applied to grassland in SE Scotland. All plots except the control received N fertilisers at a rate of 300 kg available N ha−1 a−1 (available N includes NO3−, NH4+ and urea). Fluxes of N2O were measured using static chambers. Losses of N2O from plots receiving mineral fertiliser were short-lived with a peak value of 388 g N2O–N ha−1 day−1 from NH4NO3. Release of N2O from manure treatments however extended over a longer period and was greater in magnitude. Highest emissions were measured from sewage sludge treatments with a peak value of 3488 g N2O–N ha−1 day−1 and 26 times higher cumulative loss compared to the NH4NO3 treatment in 2002. A residual effect on N2O losses was observed from sewage sludge treatments in 2004 when the plots did not receive any fertiliser. There were considerable variations in fluxes between the years, which could be linked to differences in rainfall and temperature. The type of N applied affected the influence of these factors on N2O emissions. The amount of rainfall several days after the N application did not affect N2O fluxes on NH4NO3 treatments. However, in the sewage treated plots increased correlation coefficients were calculated when rainfall amounts over a longer period of time (up to 20 days) were included. A synergistic effect of rainfall and temperature on N2O fluxes could be observed on all treatments. A significant correlation between N2O fluxes and mineral soil N (NO3− and NH4+) was observed when soil water content was not limiting (r2 = 67%, p

The present study shows that the relative contributions of leaf area ratio (LAR) and net assimilation rate (NAR) to variation among species in relative growth rate (RGR) depend on growth temperature. We grew three subantarctic and three alpine Poa species at daytime temperatures of 7, 12 and 17 degrees C, and analysed interspecific and temperature-related variation in RGRs by growth analysis. Variation in NAR accounted for most of the interspecific differences in RGR at low growth temperature, whereas variation in both NAR and LAR contributed strongly to interspecific differences in RGR at high growth temperature. For most species, the increase in RGR from 7 to 12 degrees C was attributable to an increase in LAR, whereas the increase in RGR from 12 to 17 degrees C was attributable to an increase in NAR. There were no differences between native subantarctic and alpine species in the plasticity of growth responses to temperature. However, Poa annua, a species introduced to the subantarctic, showed much greater growth plasticity than other species. There was little difference among species in tolerance of high-temperature extremes.

Chrysotile fibres were treated hydrothermally with aqueous suspensions or pastes of MgO, SiO2, Al2O3, Fe2O3, Ca(OH)2, Ca3SiO5 and β-Ca2SiO4. Partial or complete reaction often occurred, but the fibres persisted as pseudomorphs which were studied by X-ray fibre rotation photographs. Those of the products which did not contain calcium, such as Mg2SiO4, Mg3Si4O12H2 and Mg(OH)2, were usually formed with a definite crystallographic orientation relative to that of the chrysotile. A mechanism is proposed to explain this, based on the assumption that reaction occurs by migration of cations (Mg2+, Si4+, Al3+, Fe3+, H+) through a relatively unaffected oxygen framework. Products containing calcium, such as CaMgSiO4, were unoriented. This is attributed to the fact that their oxygen frameworks are more open than those of the compounds not containing calcium; because of this, their formation requires destruction and rebuilding of the crystal structure. The significance of these results for the manufacture of autoclaved asbestos cement products is briefly indicated.

Methods of optimizing the performance of an array of Compton-suppressed, segmented HPGe clover detectors have been developed which rely on the physical position sensitivity of both the HPGe crystals and the Compton-suppression shields. These relatively simple analysis procedures promise to improve the precision of experiments with the TRIUMF-ISAC Gamma-Ray Escape-Suppressed Spectrometer (TIGRESS). Suppression schemes will improve the efficiency and peak-to-total ratio of TIGRESS for high γ-ray multiplicity events by taking advantage of the 20-fold segmentation of the Compton-suppression shields, while the use of different summing schemes will improve results for a wide range of experimental conditions. The benefits of these methods are compared for many γ-ray energies and multiplicities using a GEANT4 simulation, and the optimal physical configuration of the TIGRESS array under each set of conditions is determined.

Effective management of soil structure and organic matter are essential in organic cropping to ensure good rooting conditions and to optimize the production of mineralized N and thus minimize greenhouse gas emissions. We investigated how mid-winter or early spring ploughing and three grazing duration treatments prior to ploughing influenced soil structure, soil organic matter and plant root growth under the first spring barley crop after a grass-clover ley. The experiment was carried out over two seasons. We also studied the soil under first-year oats in a long-term rotations experiment where 2 or 3 years of arable crops followed 3 or 4 years of grass. Pore size distribution and pore continuity, bulk density, particulate (light fraction) organic matter, readily oxidizable organic matter (ROM), aggregate size distribution and root length densities were measured. Macroporosity appeared to be the best indicator of soil physical fertility; it was sensitive to changes in soil structure arising from compaction and root growth. This, along with visual examination, revealed the loosening resulting from ploughing. The generally favourable macroporosity amongst small, stable aggregates reduced the likelihood of development of anaerobism. Macroporosity and aggregate size can be estimated from visual examination of the soil, a method that offers the advantage of being quick and of sampling a large volume. The content of ROM was high 6.1-6.4 g 100 g -1 whole soil. However, particulates formed only a small fraction (6-9%) of the ROM. Despite the favourable ROM and structure, the soil was susceptible to compaction damage during seedbed preparation in wet soil after ploughing which reduced grain yield in some plots. Grazing by sheep before ploughing and date of ploughing had minor effects on soil quality. Grazing for 2 months prior to ploughing increased root length density in the upper topsoil in the following arable crop, possibly because of the higher quality of the animal and grass-clover residues. Conservation of soil quality was related more to secondary tillage and sowing operations after ploughing than to duration and timing of grazing.

Off-highway vehicle (OHV) recreation impacts species and ecosystems around the world, and is particularly prevalent in the United States. Our study examines the impact of OHVs on one of several species restricted within the United States to the Algodones Dunes, California. This dune system attracts many OHV enthusiasts annually, and interest in determining the impact of OHVs on Astragalus magdalenae var. peirsonii (Peirson’s milk-vetch) has motivated multiple investigations. Several of these investigations have arrived at seemingly contradictory conclusions. Our study objectives were to quantify the degree by which A. m. var. peirsonii densities differed between high- and low-OHV use areas and determine whether OHV impact was a plausible factor for affecting plant density. Density estimate comparisons indicated 4–5 times fewer plants occupied a study area open to OHVs relative to two nearby study areas legally closed to OHVs. A manipulative mark-resight experiment compared the survival probabilities of control plants to those purposefully struck by OHVs and found that, for plants with canopy diameters of

Tests of the performance of a 32-fold segmented HPGe clover detector coupled to a 20-fold segmented Compton-suppression shield, which form a prototype element of the TRIUMF-ISAC Gamma-Ray Escape-Suppressed Spectrometer (TIGRESS), have been made. Peak-to-total ratios and relative efficiencies have been measured for a variety of γ -ray energies. These measurements were used to validate a GEANT4 simulation of the TIGRESS detectors, which was then used to create a simulation of the full 12-detector array. Predictions of the expected performance of TIGRESS are presented. These predictions indicate that TIGRESS will be capable, for single 1 MeV γ rays, of absolute detection efficiencies of 17% and 9.4%, and peak-to-total ratios of 54% and 61% for the “high-efficiency” and “optimized peak-to-total” configurations of the array, respectively.