Canopy soils can significantly contribute to aboveground labile biomass, especially in tropical montane forests. Whether they also contribute to the exchange of greenhouse gases is unknown. To ...examine the importance of canopy soils to tropical forest-soil greenhouse gas exchange, we quantified gas fluxes from canopy soil cores along an elevation gradient with 4 yr of nutrient addition to the forest floor. Canopy soil contributed 5–12 percent of combined (canopy + forest floor) soil CO₂ emissions but CH₄ and N₂O fluxes were low. At 2000 m, phosphorus decreased CO₂ emissions (> 40%) and nitrogen slightly increased CH₄ uptake and N₂O emissions. Our results show that canopy soils may contribute significantly to combined soil greenhouse gas fluxes in montane regions with high accumulations of canopy soil. We also show that changes in fluxes could occur with chronic nutrient deposition.
Aims Our goal was to assess how management and sward functional diversity affect nitrogen response efficiency (NRE), the ratio of plant biomass production to supply of available nitrogen (N) in ...temperate grassland. Methods A three-factorial design was employed: three sward compositions, two mowing frequencies, and two fertilization treatments. Results NRE was largely influenced by fertilization followed by mowing frequency and sward composition. NRE was larger in unfertilized than fertilized plots, in plots cut thrice than plots cut once per year, and in control swards than in monocot-or dicotenhanced swards. Fertilization decreased NRE through decreases in both N uptake efficiency (plant N uptake per supply of available N) and N use efficiency (NUE, biomass produced per plant N uptake) whereas mowing frequency and sward composition affected NRE through N uptake efficiency rather than NUE. The largest NRE in the control sward with 70 % monocots and 30 % dicots attests that these proportions of functional groups were best adapted in this grassland ecosystem. Conclusions Optimum NRE may not be a target of most farmers, but it is an appropriate tool to evaluate the consequences of grassland management practices, which farmers may employ to maximize profit, on environmental quality.
Current interferometric gravitational-wave detectors are limited by quantum noise over a wide range of their measurement bandwidth. One method to overcome the quantum limit is the injection of ...squeezed vacuum states of light into the interferometer's dark port. Here, we report on the successful application of this quantum technology to improve the shot noise limited sensitivity of the Advanced Virgo gravitational-wave detector. A sensitivity enhancement of up to 3.2±0.1 dB beyond the shot noise limit is achieved. This nonclassical improvement corresponds to a 5%-8% increase of the binary neutron star horizon. The squeezing injection was fully automated and over the first 5 months of the third joint LIGO-Virgo observation run O3 squeezing was applied for more than 99% of the science time. During this period several gravitational-wave candidates have been recorded.
Full text
Available for:
CMK, CTK, FMFMET, NUK, UL
Context.
Scientific interest in studying high-energy transient phenomena in the Universe has risen sharply over the last decade. At present, multiple ground-based survey projects have emerged to ...continuously monitor the optical (and multi-messenger) transient sky at higher image cadences and covering ever larger portions of the sky every night. These novel approaches are leading to a substantial increase in global alert rates, which need to be handled with care, especially with regard to keeping the level of false alarms as low as possible. Therefore, the standard transient detection pipelines previously designed for narrow field-of-view instruments must now integrate more sophisticated tools to deal with the growing number and diversity of alerts and false alarms.
Aims.
Deep machine learning algorithms have now proven their efficiency in recognising patterns in images. These methods are now used in astrophysics to perform different classification tasks such as identifying bogus from real transient point-like sources. We explore this method to provide a robust and flexible algorithm that could be included in any kind of transient detection pipeline.
Methods.
We built a convolutional neural network (CNN) algorithm in order to perform a ‘real or bogus’ classification task on transient candidate cutouts (subtraction residuals) provided by different kinds of optical telescopes. The training involved human-supervised labelling of the cutouts, which are split into two balanced data sets with ‘true’ and ‘false’ point-like source candidates. We tested our CNN model on the candidates produced by two different transient detection pipelines. In addition, we made use of several diagnostic tools to evaluate the classification performance of our CNN models.
Results.
We show that our CNN algorithm can be successfully trained on a large and diverse array of images on very different pixel scales. In this training process, we did not detect any strong over- or underfitting with the requirement of providing cutouts with a limited size no larger than 50 × 50 pixels. Tested on optical images from four different telescopes and utilising two different transient detection pipelines, our CNN model provides a robust ‘real or bogus’ classification performance accuracy from 93% up to 98% for well-classified candidates.
Nutrient deposition to tropical forests is increasing, which could affect soil fluxes of nitrous oxide (N2O), a powerful greenhouse gas. We assessed the effects of 35-56 months of moderate nitrogen ...(N) and phosphorus (P) additions on soil N2O fluxes and net soil N-cycling rates, and quantified the relative contributions of nitrification and denitrification to N2O fluxes. In 2008, a nutrient manipulation experiment was established along an elevation gradient (1000, 2000 and 3000 m) of montane forests in southern Ecuador. Treatments included control, N, P and N+P addition (with additions of 50 kg N ha−1 yr-1 and 10 kg P ha−1 yr-1). Nitrous oxide fluxes were measured using static, vented chambers and N cycling was determined using the buried bag method. Measurements showed that denitrification was the main N2O source at all elevations, but that annual N2O emissions from control plots were low, and decreased along the elevation gradient (0.57 ± 0.26 to 0.05 ± 0.04 kg N2O-N ha-1 yr-1). We attributed the low fluxes to our sites’ conservative soil N cycling as well as gaseous N losses possibly being dominated by N2. Contrary to the first 21 months of the experiment, N addition did not affect N2O fluxes during the 35-56 month period, possibly due to low soil moisture contents during this time. With P addition, N2O fluxes and mineral N concentrations decreased during Months 35-56, presumably because plant P limitations were alleviated, increasing plant N uptake. Nitrogen plus phosphorus addition showed similar trends to N addition, but less pronounced given the counteracting effects of P addition. The combined results from this study (Months 1-21 and 35-56) showed that effects of N and P addition on soil N2O fluxes were not linear with time of exposure, highlighting the importance of long-term studies.
The increasing atmospheric N2O concentration and the imbalance in its global budget have triggered the interest in quantifying N2O fluxes from various ecosystems. This study was conducted to estimate ...the annual N2O emissions from a transitional grassland-forest region in Saskatchewan, Canada. The study region was stratified according to soil texture and land use types, and we selected seven landscapes (sites) to cover the range of soil texture and land use characteristics in the region. The study sites were, in turn, stratified into distinguishable spatial sampling units (i.e., footslope and shoulder complexes), which reflected the differences in soils and soil moisture regimes within a landscape. N2O emission was measured using a sealed chamber method. Our results showed that water-filled pore space (WFPS) was the variable most correlated to N2O fluxes. With this finding, we estimated the total N2O emissions by using regression equations that relate WFPS to N2O emission, and linking these regression equations with a soil moisture model for predicting WFPS. The average annual fluxes from fertilized cropland, pasture/hay land, and forest areas were 2.00, 0.04, and 0.02 kg N2O-N ha-1 yr-1, respectively. The average annual fluxes for the medium- to fine-textured and sandy-textured areas were 1.40 and 0.04 kg N2O-N ha-1 yr-1, respectively. The weighted-average annual flux for the study region is 0.95 kg N2O-N ha-1 yr-1. The fertilized cropped areas covered only 47% of the regional area but contributed about 98% of the regional flux. We found that in the clay loam, cropped site, 2% and 3% of the applied fertilizer were emitted as N2O on the shoulders and footslopes, respectively.
GW170817 is the very first observation of gravitational waves originating from the coalescence of two compact objects in the mass range of neutron stars, accompanied by electromagnetic counterparts, ...and offers an opportunity to directly probe the internal structure of neutron stars. We perform Bayesian model selection on a wide range of theoretical predictions for the neutron star equation of state. For the binary neutron star hypothesis, we find that we cannot rule out the majority of theoretical models considered. In addition, the gravitational-wave data alone does not rule out the possibility that one or both objects were low-mass black holes. We discuss the possible outcomes in the case of a binary neutron star merger, finding that all scenarios from prompt collapse to long-lived or even stable remnants are possible. For long-lived remnants, we place an upper limit of 1.9 kHz on the rotation rate. If a black hole was formed any time after merger and the coalescing stars were slowly rotating, then the maximum baryonic mass of non-rotating neutron stars is at most , and three equations of state considered here can be ruled out. We obtain a tighter limit of for the case that the merger results in a hypermassive neutron star.
KIC 6761539 is one of many fast rotating γ Doradus – δ Scuti hybrid pulsators. A search for possible regularities in the frequency spectrum is performed and a first stellar model is presented.
A G→C polymorphism has been identified in the human cyclooxygenase‐2 (COX‐2) gene promoter at position −765 with C allele leading to a decreased promoter activity with low prostaglandin E2 (PGE2) ...production. PGE2 has strong immunomodulatory properties that could influence graft survival. We studied the association between this polymorphism and allograft failure in two independent cohorts of renal transplant recipients (RTRs) including a total of 603 patients. The functional effect of COX‐2 gene promoter polymorphism was analyzed by measuring serum levels of PGE2. Median follow‐up was 8.7 and 7.9 years for the first and second cohort, respectively. Analysis of 603 patients identified 20 CC (3.3%), 179 GC (29.7%) and 404 GG (67%) carriers. Patients with the GG genotype had significantly higher serum PGE2 concentrations than patients with the C allele. Carriers with a C allele have an independent increased risk of graft loss (hazard ratio (HR) 2.43 95% CI 1.19–4.97, p = 0.015 for cohort 1; HR 1.72 95% CI 0.99–3.77, p = 0.051 for cohort 2) compared to GG patients. COX‐2 gene promoter polymorphism at position −765 (G→C) is associated with a higher rate of graft loss in RTRs. Such findings may be used to influence immunosuppressive strategies and optimize patient management.
COX‐2 gene promoter polymorphism at position ‐765 (G to C) is associated with a higher rate of graft loss in renal transplant recipients.
PDF
