Measurement of streaming potential coupling coefficient in sandstones saturated with natural and artificial brines at high selenity

We report experimental measurements of the streaming potential coupling coefficient in sandstones saturated with NaCl-dominated artificial and natural brines up to 5.5 M (321.4 g L−1 of NaCl; electrical conductivity of 23 S m−1). We find that the magnitude of the coupling coefficient decreases with increasing brine salinity, as observed in previous experimental studies and predicted by models of the electrical double layer. However, the magnitude of the coupling coefficient remains greater than zero up to the saturated brine salinity. The magnitude of the zeta potential we interpret from our measurements also decreases with increasing brine salinity in the low-salinity domain (0.4 M). We hypothesize that the constant value of zeta potential observed at high salinity reflects the maximum packing of counterions in the diffuse part of the electrical double layer. Our hypothesis predicts that the zeta potential becomes independent of brine salinity when the diffuse layer thickness is similar to the diameter of the hydrated counterion. This prediction is confirmed by our experimental data and also by published measurements on alumina in KCl brine. At high salinity (>0.4 M), values of the streaming potential coupling coefficient and the corresponding zeta potential are the same within experimental error regardless of sample mineralogy and texture and the composition of the brine

Ultracompact Generation of Continuous-Variable Cluster States

We propose an experimental scheme that has the potential for large-scale realization of continuous-variable (CV) cluster states for universal quantum computation. We do this by mapping CV cluster-state graphs onto two-mode squeezing graphs, which can be engineered into a single optical parametric oscillator (OPO). The desired CV cluster state is produced directly from a joint squeezing operation on the vacuum using a multi-frequency pump beam. This method has potential for ultracompact experimental implementation. As an illustration, we detail an experimental proposal for creating a four-mode square CV cluster state with a single OPO.Comment: 4 pages, 1 figure; v2 improved discussion of the implications of our result; added discussion of finite squeezing effect

Back Reaction of Hawking Radiation on Black Hole Geometry

We propose a model for the geometry of a dynamical spherical shell in which the metric is asymptotically Schwarzschild, but deviates from Ricci-flatness in a finite neighbourhood of the shell. Hence, the geometry corresponds to a `hairy' black hole, with the hair originating on the shell. The metric is regular for an infalling shell, but it bifurcates, leading to two disconnected Schwarzschild-like spacetime geometries. The shell is interpreted as either collapsing matter or as Hawking radiation, depending on whether or not the shell is infalling or outgoing. In this model, the Hawking radiation results from tunnelling between the two geometries. Using this model, the back reaction correction from Hawking radiation is calculated.Comment: Latex file, 15 pages, 4 figures enclosed, uses eps

Analysis of the Least Squares Approach to Broadband Beamspace Beamforming

In this paper, we present a comprehensive comparison of different structures for broadband beamforming. We focus on both the tapped delay line (TDL) and the least squares (LS), beamspace approaches. Through simulations we confirm the superiority of the beamspace method (i.e., less complex and better frequency invariance). However, its anti-jamming ability is reduced due to non-orthogonal beams. We show how to mitigate this via a reduced rank approximation of the autocorrelation matrix

Longevity and mortality in Kennel Club registered dog breeds in the UK in 2014

Abstract Background The domestic dog is one of the most diverse mammalian species, exhibiting wide variations in morphology, behaviour and morbidity across breeds. Therefore, it is not unexpected that breeds should also exhibit variation in mortality and longevity. While shorter longevity per se may not necessarily be a welfare issue, a generally foreshortened lifespan in a breed that is accompanied by a high prevalence of a particular cause of death may reveal potentially serious welfare concerns and highlight scope to improve breed welfare. Survey data gathered directly from owners offer useful insights into canine longevity and mortality that can support the overall evidence base for welfare reforms within breeds. Results Mortality data on 5663 deceased dogs registered with the UK Kennel Club were collected from an owner-based survey. The most commonly reported causes of death were old age (13.8%), unspecified cancer (8.7%) and heart failure (4.9%); with 5.1% of deaths reported as unknown cause. Overall median age at death was 10.33 years (interquartile range: 7.17–12.83 years). Breeds varied widely in median longevity overall from the West Highland Terrier (12.71 years) to the Dobermann Pinscher (7.67 years). There was also wide variation in the prevalence of some common causes of death among breeds, and in median longevity across the causes of death. Conclusion Substantial variation in the median lifespan and the prominent causes of death exists across breeds. This study has identified some breeds with both a low median lifespan and also a high proportional mortality for one or more specific causes of death that should be considered as both potential welfare concerns as well as opportunities for improvement

Large-scale survey to estimate the prevalence of disorders for 192 Kennel Club registered breeds

Abstract Background Pedigree or purebred dogs are often stated to have high prevalence of disorders which are commonly assumed to be a consequence of inbreeding and selection for exaggerated features. However, few studies empirically report and rank the prevalence of disorders across breeds although such data are of critical importance in the prioritisation of multiple health concerns, and to provide a baseline against which to explore changes over time. This paper reports an owner survey that gathered disorder information on Kennel Club registered pedigree dogs, regardless of whether these disorders received veterinary care. This study aimed to determine the prevalence of disorders among pedigree dogs overall and, where possible, determine any variation among breeds. Results This study included morbidity data on 43,005 live dogs registered with the Kennel Club. Just under two thirds of live dogs had no reported diseases/conditions. The most prevalent diseases/conditions overall were lipoma (4.3%; 95% confidence interval 4.13-4.52%), skin (cutaneous) cyst (3.1%; 2.94-3.27%) and hypersensitivity (allergic) skin disorder (2.7%; 2.52-2.82%). For the most common disorders in the most represented breeds, 90 significant differences between the within breed prevalence and the overall prevalence are reported. Conclusion The results from this study have added vital epidemiological data on disorders in UK dogs. It is anticipated that these results will contribute to the forthcoming Breed Health & Conservation Plans, a Kennel Club initiative aiming to assist in the identification and prioritisation of breeding selection objectives for health and provide advice to breeders/owners regarding steps that may be taken to minimise the risk of the disease/disorders. Future breed-specific studies are recommended to report more precise prevalence estimates within more breeds

A Monte Carlo simulation study of the impact of novel scintillation crystals on performance characteristics of PET scanners

© 2018 Associazione Italiana di Fisica Medica Objective: The purpose of this study is to validate a Monte Carlo simulation model for the clinical Siemens Biograph mCT PET scanner using the GATE simulation toolkit, and to evaluate the performance of six different scintillation materials in this model using the National Electrical Manufactures Association (NEMA) NU 2-2007 protocol. Methods: A model of the Biograph mCT PET detection system and its geometry was developed. NEMA NU 2-2007 phantoms were also modelled. The accuracy of the developed scanner model was validated through a comparison of the simulation results from GATE, SimSET and PeneloPET toolkits, and experimental data obtained using the NEMA NU 2-2007 protocols. The evaluated performance metrics included count rate performance, spatial resolution, sensitivity, and scatter fraction (SF). Thereafter, the mCT PET scanner was simulated with six different candidate high-performance scintillation materials, including LSO, LaBr3, CeBr3, LuAP, GLuGAG and LFS-3, and its performance evaluated according to the NEMA NU 2-2007 specifications. Results: The Monte Carlo simulation model demonstrates good agreement with the experimental data and results from other simulation packages. For instance, the scatter fraction calculated using GATE simulation is 34.35% while the experimentally measured value is 33.2%, 38.48% for the SimSET, and 34.8% for the PeneloPET toolkit. The best-performing scintillation materials were found to be LuAP, LSO and LFS-3, while GLuGAG offers acceptable performance if cost is the dominant concern. Conclusion: The main performance characteristics of the Biograph mCT PET scanner can be simulated accurately using GATE with a good agreement with other Monte Carlo simulation packages and experimental measurements. Newly developed scintillators show promise and offer alternative options for the design of novel generation PET scanners

Distributed Optimal Quantization and Power Allocation for Sensor Detection Via Consensus

We address the optimal transmit power allocation problem (from the sensor nodes (SNs) to the fusion center (FC)) for the decentralized detection of an unknown deterministic spatially uncorrelated signal which is being observed by a distributed wireless sensor network. We propose a novel fully distributed algorithm, in order to calculate the optimal transmit power allocation for each sensor node (SN) and the optimal number of quantization bits for the test statistic in order to match the channel capacity. The SNs send their quantized information over orthogonal uncorrelated channels to the FC which linearly combines them and makes a final decision. What makes this scheme attractive is that the SNs share with their neighbours just their individual transmit powers at the current states. As a result, the SN processing complexity is further reduced

Sparse Reconstruction of Time-Frequency Representation using the Fractional Fourier Transform

This paper describes a novel method to approximate instantaneous frequency of non-stationary signals through an application of fractional Fourier transform (FRFT). FRFT enables us to build a compact and accurate chirp dictionary for each windowed signal, thus the proposed approach offers improved computational efficiency, and good performance when compared with chirp atom method