In this study, laboratory scale digesters were operated to simulate potential shocks to the Anaerobic Digestion (AD) process at a 350 ML/day wastewater treatment plant. The shocks included high ...(42 °C) and low (32 °C) temperature (either side of mesophilic 37 °C) and a 20% loading of fats, oil and grease (FOG; 20% w:v). These variables were explored at two sludge retention times (12 and 20 days) and two organic loading rates (2.0 and 2.5 kgTS/m3day OLR). Metagenomic and metabolomic approaches were then used to characterise the impact of operational shocks in regard to temperature and FOG addition, as determined through monitoring of biogas production, the microbial profile and their metabolism. Results showed that AD performance was not greatly affected by temperature shocks, with the biggest impact being a reduction in biogas production at 42 °C that persisted for 32 ± 1 days. The average biogas production across all digesters at the completion of the experiment was 264.1 ± 76.5 mL/day, with FOG addition observed to significantly promote biogas production (+87.8 mL/day). Metagenomic and metabolomic analyses of the digesters indicated that methanogens and methane oxidising bacteria (MOB) were low in relative abundance, and that the ratio of oxidising bacteria (methane, sulphide and sulphate) with respect to sulphate reducing bacteria (SRB) had a noticeable influence on biogas production. Furthermore, increased biogas production correlated with an increase in short chain fatty acids, a product of the addition of 20% FOG. This work demonstrates the application of metagenomics and metabolomics to characterise the microbiota and their metabolism in AD digesters, providing insight to the resilience of crucial microbial populations when exposed to operational shocks.
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•Metagenomics and metabolomics provide insight into anaerobic digester operation.•Methanogen and methane oxidising bacteria were found in relative low numbers.•Metabolomics highlighted increased biogas in digesters with increased SCFAs.•Biogas related biota were varied while biogas production was fairly constant.
Radiological source search is a challenge involving the detection, identification, and localization of weak sources within background environments that vary both spatially and temporally. In this ...paper, a method for simultaneously detecting and identifying gamma-ray sources using background models formed from spectral data is described. Non-negative matrix factorization (NMF) is used to generate low-dimensional representations of gamma-ray spectra, allowing for a compact means of capturing variation in gamma-ray backgrounds. Background models formed using NMF are used to perform anomaly detection, and additionally, models are augmented with spectral templates of gamma-ray sources to perform simultaneous detection and identification using a likelihood ratio test. The NMF-based detection and identification algorithm is benchmarked against a standard Region of Interest algorithm and shows significant performance gains. In addition, NMF-based anomaly detection shows improvements over methods based on gross counts or principal component analysis. Algorithm performance is evaluated using unshielded sources with activities between 5 and 400 <inline-formula> <tex-math notation="LaTeX">{\mu } </tex-math></inline-formula>Ci at a standoff distance of 20 m using source injection on background data collected using a 1 m 2 NaI array on the Radiological Multisensor Analysis Platform.
The Polaris-LAMP multi-modal 3-D gamma-ray imager is a radiation mapping and imaging platform which uses a commercial off-the-shelf (COTS) detector integrated with a contextual sensor localization ...and mapping platform. The integration of these systems enables a free-moving radiation imaging capability with proximity mapping, coded-aperture, and Compton imaging modalities, which can create 3-D reconstruction of photon sources from tens of keV to several MeV. Gamma-ray events are recorded using a segmented cadmium zinc telluride (CZT) detector (Polaris-H Quad by H3D Inc., Ann Arbor, MI, USA), while scene data are derived from a contextual sensor and computation package developed by Lawrence Berkeley National Laboratory which includes GPS, laser ranging, and inertial measurement sensors. An onboard computer uses these inputs to create rapidly updating pose (10 Hz) and 3-D scene estimates using a simultaneous localization and mapping (SLAM) algorithm. The precise gamma-ray event location and timing resolution of the Polaris CZT sensor enables Compton imaging above several hundred keV, while photon sources at lower images are localized using coded-aperture imaging techniques. The multi-modal imaging concept enables imaging of diverse radiation sources spanning from the 59-keV emission of 241 Am to the 1.1 and 1.3 MeV lines of 60 Co. This work focuses on the description of the operational principles of the detector system and demonstrating the 3-D imaging performance in a variety of source detection and mapping scenarios. As a proof of concept, we demonstrate mapping complex environments, including both point source and distributed-source environments using proximity, coded-aperture, and Compton imaging modalities. Furthermore, we show the successful use of the system to perform measurements in high-background environments through analysis of arrays of uranium hexafluoride cylinders at the Paducah UF6 project site.
Radiological source search is a challenging task involving detection and identification of weak sources in a constantly changing radiological background. As of now, many radiological source detection ...algorithms have been proposed; however, their computational complexity and, hence, reliance on power intensive processing units inhibit low-power applications of radiological source search systems. In this work, we introduce the anomaly filter (AF) algorithm; a computationally light, yet effective time-series source detection algorithm based on exponential weighted moving average (EWMA) and Poisson deviance statistics. Then, we demonstrate that the proposed algorithm can be used in ensemble with other more computationally intensive source detection and identification algorithms to achieve both increased detection performance and reduced power consumption. The proposed AF algorithm and the ensemble algorithms were thoroughly benchmarked against several existing source detection and identification algorithms. The results show that the AF algorithm outperforms existing conventional source detection algorithms, and the ensemble approach improves the overall performance of existing source detection and isotope identification algorithms. Furthermore, the AF algorithm and the non-negative matrix factorization approach-based source identification (NMF-ID) algorithm were combined and implemented on a single-board microcontroller, and the power consumption was measured. This ensemble algorithm reduced the power consumption of the NMF-ID algorithm almost by a factor of 100, while improving the detection performance of the overall system.
Fire is rampant throughout subtropical South and Southeast Asian grasslands. However, very little is known about the role of fire and pyric herbivory on the functioning of highly productive ...subtropical monsoon grasslands lying within the Cwa climatic region. We assessed the temporal effect of fire on postfire regrowth quality and associated pyric‐herbivory in the subtropical monsoon grasslands of Bardia National Park, Nepal. Every year, grasslands are burned as a management intervention in the park, especially between March and May. Within a week after fire, at the end of March 2020, we established 60 m × 60 m plots within patches of burned grassland in the core area of the Park. We collected grass samples from the plots and determined physical and chemical properties of the vegetation at regular 30‐day intervals from April to July 2020, starting from 30 days after fire to assess postfire regrowth forage quality. We counted pellet groups of cervids that are abundant in the area for the same four months from 2 m × 2 m quadrats that were permanently marked with pegs along the diagonal of each 60 m × 60 m plot to estimate intensity of use by deer to the progression of postfire regrowth. We observed strong and significant reductions in crude protein (mean value 9.1 to 4.1 55% decrease) and phosphorus (mean value 0.2 to 0.11 45% decrease) in forage collected during different time intervals, that is, from 30 days to 120 days after fire. Deer utilized the burned areas extensively for a short period, that is, up to two months after fire when the burned areas contained short grasses with a higher level of crude protein and phosphorus. The level of use of postfire regrowth by chital (Axis axis) differed significantly over time since fire, with higher intensity of use at 30 days after fire. The level of use of postfire regrowth by swamp deer (Rucervus duvaucelii) did not differ significantly until 90 days after fire, however, decreased significantly after 90 days since fire. Large‐scale single event fires, thus, may not fulfil nutritional requirements of all species in the deer assemblage in these subtropical monsoon grasslands. This is likely because the nutritional requirements of herbivores differ due to differences in body size and physiological needs—maintenance, reproduction, and lactation. We recommend a spatiotemporal manipulation of fire to reinforce grazing feedback and to yield forage of high quality for the longest possible period for a sustainable high number of deer to maintain a viable tiger population within the park.
Given the widespread use of fire as a cost‐effective grassland management tool in subtropical monsoon grasslands in the Cwa climate region, it is important to realize that the positive benefit of a single event fire for the conservation of large herbivores is time specific, as the effect of fire on forage quality perhaps lasts only for short period.
The main obstacle to the practical implementation of the dielectric wakefield acceleration (DWA) concept is the development of the beam breakup instability due to transverse dipole wakefields ...generated when the beam propagates off axis in the accelerating structure. One of the methods to suppress this instability is to elliptically shape the beam and accelerate it in a planar structure. Here, we report a detailed experimental investigation of the transverse dynamics of elliptical beams in planar dielectric structure with parameters mimicking future DWA modules. Both dipole and quadrupole wakefields’ effects on beam stability and projected emittance were studied. This study has highlighted the importance of counteracting quadrupole wakefields in future DWA implementations.
Abstract
The detection, identification, and localization of illicit radiological and nuclear material continue to be key components of nuclear non-proliferation and nuclear security efforts around ...the world. Networks of radiation detectors deployed at strategic locations in urban environments have the potential to provide continuous radiological/nuclear (R/N) surveillance and provide high probabilities of intercepting threat sources. The integration of contextual information from sensors such as video, Lidar, and meteorological sensors can provide significantly enhanced situational awareness, and improved detection and localization performance through the fusion of the radiological and contextual data. In this work, we present details of our work to establish a city-scale multi-sensor network testbed for intelligent, adaptive R/N detection in urban environments, and develop new techniques that enable city-scale source detection, localization, and tracking.
A variety of chiral Ti(IV) complexes were reduced in situ with zinc in acetonitrile. The resulting chiral Ti(III) complexes were found to catalyze the pinacol coupling reaction stereoselectively. The ...best results were obtained from the Ti−SALEN complex, which was found to be an efficient catalyst at 10 mol % concentration. Various aromatic aldehydes were coupled to obtain chiral hydrobenzoin derivatives with high diastereoselectivity and enantioselectivity. A plausible mechanism is proposed that rationalizes the stereochemical outcome of the reaction.
Soil loss due to erosion has a huge impact on worldwide economy and environment. The Himalayan region is extremely vulnerable to erosion due to rugged terrain, erratic precipitation and excessive ...anthropogenic pressures. This study attempts to assess the spatial distribution of soil loss for managing soil disintegration rates in the western Himalayas using a GIS modeling approach. Factors affecting soil erosion were assessed and mapped using primary data from the field and secondary data. Map layers were developed for each identified factors and modeled using weighted overlay analysis. The rainfall-runoff erosivity, soil erodibility, topographic, cover management and support parameters varied around 361.75 MJ mm/ha/h/yr, (0.024–0.051) t ha h/ha/MJ/mm, 0–585.372, 0–1 and 0–1 respectively. The yearly soil disintegration rate varied between 0 and 6098.44 t ha/yr. The maximum area (137,165.30 ha) of the district’s total area (146,295.142 ha) was under the less vulnerable class and the minimum (259.92 ha) was under the severely vulnerable category. The findings reported 70.24% of the area was under the less vulnerable class, followed by extremely vulnerable (10.48%) > highly vulnerable (7.40%) > severely vulnerable (7.19%) > moderately vulnerable (4.69%). The maximum (810 t/ha) and minimum (15 t/ha) mean soil loss was found under severely vulnerable and less vulnerable categories. The findings will provide site specific data regarding soil loss and vulnerability for effective management of soils in the eco-sensitive region.
We describe the first demonstration of a sub-keV electron recoil energy threshold in a dual-phase liquid argon time projection chamber. This is an important step in an effort to develop a detector ...capable of identifying the ionization signal resulting from nuclear recoils with energies of order a few keV and below. We obtained this result by observing the peaks in the energy spectrum at 2.82keV and 0.27keV, following the K- and L-shell electron capture decay of 37Ar respectively. The 37Ar source preparation is described in detail, since it enables calibration that may also prove useful in dark matter direct detection experiments. An internally placed 55Fe x-ray source simultaneously provided another calibration point at 5.9keV. We discuss the ionization yield and electron recombination in liquid argon at those three calibration energies.
•We measure sub-keV electron recoils in a dual-phase argon time projection chamber.•Ar-37 is produced via neutron irradiation and used as calibration source.•Ar-37 electron captures at 2.82 and 0.27keV are measured together with Fe-55 x-rays.•Spurious single ionization electrons provided absolute calibration of charge signal.•Modified Thomas–Imel model describes low-energy electron-recoils in liquid Ar.
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