Near Infrared Surface Properties of the Two Intrinsically Brightest Minor Planets (90377) Sedna and (90482) Orcus

We present low resolution K band spectra taken at the Gemini 8 meter telescope of (90377) Sedna and (90482) Orcus (provisional designations 2003 VB12 and 2004 DW, respectively), currently the two minor planets with the greatest absolute magnitudes (i.e. the two most reflective minor planets). We place crude limits on the surface composition of these two bodies using a Hapke model for a wide variety of assumed albedos. The unusual minor planet (90377) Sedna was discovered on November 14, 2003 UT at roughly 90 AU with 1.6 times the heliocentric distance and perihelion distance of any other bound minor planet. It is the first solar system object discovered between the Kuiper Belt and the Oort Cloud, and may represent a transition population between the two. The reflectance spectrum of (90377) Sedna appears largely featureless at the current signal-to-noise ratio, suggesting a surface likely to be highly processed by cosmic rays. For large grain models (100 micron to 1 cm) we find that (90377) Sedna must have less than 70% surface fraction of water ice and less than 60% surface fraction of methane ice to 3 sigma confidence. Minor planet (90482) Orcus shows strong water ice absorption corresponding to less than 50% surface fraction for grain models 25 micron and larger. Orcus cannot have more than 30% of its surface covered by large (100 mm to 1 cm) methane grains to 3 sigma confidence.Comment: Accepted for publication in the Astrophysical Journa

Central Acceptance Testing for Camera Technologies for CTA

The Cherenkov Telescope Array (CTA) is an international initiative to build the next generation ground based very-high energy gamma-ray observatory. It will consist of telescopes of three different sizes, employing several different technologies for the cameras that detect the Cherenkov light from the observed air showers. In order to ensure the compliance of each camera technology with CTA requirements, CTA will perform central acceptance testing of each camera technology. To assist with this, the Camera Test Facilities (CTF) work package is developing a detailed test program covering the most important performance, stability, and durability requirements, including setting up the necessary equipment. Performance testing will include a wide range of tests like signal amplitude, time resolution, dead-time determination, trigger efficiency, performance testing under temperature and humidity variations and several others. These tests can be performed on fully-integrated cameras using a portable setup at the camera construction sites. In addition, two different setups for performance tests on camera sub-units are being built, which can provide early feedback for camera development. Stability and durability tests will include the long-term functionality of movable parts, water tightness of the camera housing, temperature and humidity cycling, resistance to vibrations during transport or due to possible earthquakes, UV-resistance of materials and several others. Some durability tests will need to be contracted out because they will need dedicated equipment not currently available within CTA. The planned test procedures and the current status of the test facilities will be presented.Comment: 8 pages, 3 figures. In Proceedings of the 34th International Cosmic Ray Conference (ICRC2015), The Hague, The Netherlands. All CTA contributions at arXiv:1508.0589

An improved history-match for layer spreading within the Sleipner plume including thermal propagation effects

The Sleipner CO2 storage operation has been injecting CO2 since 1996, and the growth of the plume has been intensively monitored using time-lapse seismic techniques. Detailed history-matching of the topmost CO2 layer has proven challenging. This paper summarizes results from a series of flow simulations examining two key parameters affecting CO2 mobility: permeability heterogeneity and fluid temperatures within the plume. The best match to the observed distribution of CO2 was achieved by including high permeability channels in the reservoir flow model, as observed on seismic data. Thermal models suggests that CO2 enters the top sand layer 7 °C warmer than the ambient reservoir. The resulting reduction in the density and viscosity of CO2 does not significantly improve the fit between seismic and simulation

CO2 storage monitoring: leakage detection and measurement in subsurface volumes from 3D seismic data at Sleipner

Demonstrating secure containment is a key plank of CO2 storage monitoring. Here we use the time-lapse 3D seismic surveys at the Sleipner CO2 storage site to assess their ability to provide robust and uniform three-dimensional spatial surveillance of the Storage Complex and provide a quantitative leakage detection tool. We develop a spatial-spectral methodology to determine the actual detection limits of the datasets which takes into account both the reflectivity of a thin CO2 layer and also its lateral extent. Using a tuning relationship to convert reflectivity to layer thickness, preliminary analysis indicates that, at the top of the Utsira reservoir, CO2 accumulations with pore volumes greater than about 3000 m3 should be robustly detectable for layer thicknesses greater than one metre, which will generally be the case. Making the conservative assumption of full CO2 saturation, this pore volume corresponds to a CO2 mass detection threshold of around 2100 tonnes. Within the overburden, at shallower depths, CO2 becomes progressively more reflective, less dense, and correspondingly more detectable, as it passes from the dense phase into a gaseous state. Our preliminary analysis indicates that the detection threshold falls to around 950 tonnes of CO2 at 590 m depth, and to around 315 tonnes at 490 m depth, where repeatability noise levels are particularly low. Detection capability can be equated to the maximum allowable leakage rate consistent with a storage site meeting its greenhouse gas emissions mitigation objective. A number of studies have suggested that leakage rates around 0.01% per year or less would ensure effective mitigation performance. So for a hypothetical large-scale storage project, the detection capability of the Sleipner seismics would far exceed that required to demonstrate the effective mitigation leakage limit. More generally it is likely that well-designed 3D seismic monitoring systems will have robust 3D detection capability significantly superior to what is required to prove greenhouse gas mitigation efficacy

Critical review of the impacts of grazing intensity on soil organic carbon storage and other soil quality indicators in extensively managed grasslands

Acknowledgements This work contributes to the N-Circle project (grant number BB/N013484/1), and CINAg (BB/N013468/1) Virtual Joint Centres on Agricultural Nitrogen (funded by the Newton Fund via UK BBSRC/NERC), U-GRASS (grant number NE/M016900/1), the Belmont Forum/FACCE-JPI DEVIL project (grant number NE/M021327/1), Soils-R-GGREAT (grant number NE/P019455/1), ADVENT (grant number NE/M019713/1), Sêr Cymru LCEE-NRN project, Climate-Smart Grass and the Scottish Government’s Strategic Research Programme.Peer reviewedPublisher PD

Lane Compression: A Lightweight Lossless Compression Method for Machine Learning on Embedded Systems

This article presents Lane Compression, a lightweight lossless compression technique for machine learning that is based on a detailed study of the statistical properties of machine learning data. The proposed technique profiles machine learning data gathered ahead of run-time and partitions values bit-wise into different lanes with more distinctive statistical characteristics. Then the most appropriate compression technique is chosen for each lane out of a small number of low-cost compression techniques. Lane Compression’s compute and memory requirements are very low and yet it achieves a compression rate comparable to or better than Huffman coding. We evaluate and analyse Lane Compression on a wide range of machine learning networks for both inference and re-training. We also demonstrate the profiling prior to run-time and the ability to configure the hardware based on the profiling guarantee robust performance across different models and datasets. Hardware implementations are described and the scheme’s simplicity makes it suitable for compressing both on-chip and off-chip traffic. Samsung Advanced Institute of Technology (SAIT

Nutrient removal capacity of wood residues for the Agro-environmental safety of ground and surface waters

Abstract   The aim of this study was to determine the effectiveness of wood residues in the removal of nutrients (ammonium-N; NH4-N) from nutrient-rich (NH4-N) waters. The water holding capacity of the wood materials was also determined. Carried out at Rothamsted Research, North Wyke, UK, this controlled laboratory experiment tested two wood residues; in length, one being 1-2cm and the other from 150 µm (microns) to 9.5mm. Although a wide range of studies have shown the effectiveness and performance of various absorbent materials as animal beddings, such as straw (cereal straw), woodchip (sawdust, bark or wood shavings), bracken and rushes, only few have focused on the NH4-N sorption/desorption capacity. The depuration capacity of wood residues from nutrient-rich effluents such as those from cattle bedded on woodchip or straw will be controlled by processes such as sorption (adsorption-absorption) and desorption of nutrients. Studies have reported the nitrogen removal capacity of woodchip materials and biochar from woodchip as well as removal of NH4+-N from domestic and municipal wastewater, farm dirty water, landfill and industry effluents. These studies have observed that the mechanism of removal of nitrogen is by either increasing NO3--N removal form leachate by enhancing N2O losses via denitrification (biochar as carbon source for denitrifiers) or by decreasing NH4+-N in leachate through adsorption to negatively charged sites. Results showed that although the cation exchange capacity (CEC) and surface area (SA) are both fundamental properties of adsorbent materials, no correlation was found with CEC and adsorption or desorption. Nor did changes in pH appear to be sufficiently important to cause changes in CEC. For this reason, osmotic pressure appeared to be a more predominant parameter controlling processes of adsorption and desorption of NH4+-N in both wood residues. Thus, wood residues high in NH4+-N should be avoided, as they could have an opposite effect in the adsorption of nutrients from nutrient-rich effluents. The results also showed that some wood residues (G30) had great capacity to adsorb NH4+-N to levels up to nearly 90% whilst demonstrating low desorption capacity of NH4+-N (less than 1%). These are ideal relevant features for an adsorbent material for the removal of nutrients (or heavy metals) from contaminated waters such us farm o industrial effluents, or for the depuration of eutrophic watercourses. This could help reduce the concentration of farm effluents making them more manageable, subsequently contributing towards the compliance of new environmental regulations. Keywords: nutrients, nitrogen, ground and surface wate

Diagnosing ENSO and global warming tropical precipitation shifts using surface relative humidity and temperature

This is the final version of the article. Available from American Meteorological Society via the DOI in this recordLarge uncertainty remains in future projections of tropical precipitation change under global warming. A simplified method for diagnosing tropical precipitation change is tested here on present day El Niño-Southern Oscillation (ENSO) precipitation shifts. This method, based on the weak temperature gradient approximation, assumes precipitation is associated with local surface relative humidity (RH) and air temperature (SAT), relative to the tropical mean. Observed and simulated changes in RH and SAT are subsequently used to diagnose changes in precipitation. Present day ENSO precipitation shifts are successfully diagnosed using observations (r = 0:69), and an ensemble of atmosphere-only (0:51 ≤ r ≤ 0:8) and coupled (0:5 ≤ r ≤ 0:87) climate model simulations. RH (r = 0:56) is much more influential than SAT (r = 0:27) in determining ENSO precipitation shifts for observations and climate model simulations over both land and ocean. Using inter-model differences, a significant relationship is demonstrated between method performance over ocean for present day ENSO and projected global warming (r = 0:68). As a caveat, we note that mechanisms leading to ENSO-related precipitation changes are not a direct analogue for global warming-related precipitation changes. The diagnosis method presented here demonstrates plausible mechanisms which relate changes in precipitation, RH and SAT under different climate perturbations. Therefore, uncertainty in future tropical precipitation changes may be linked with uncertainty in future RH and SAT changes.AT was supported by a NERC studentship NE/M009599/1 and CASE funding from the Met Office. FHL was part supported by the UK-China Research and Innovation Partnership Fund through the Met Office Climate Science for Service Partnership (CSSP) China as part of the Newton Fund. RC was supported by the Newton Fund through the Met Office Climate Science for Service Partnership Brazil (CSSP Brazil)