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The link between jet-installation noise and the near-field flow features of the corresponding isolated jet is studied by means of lattice-Boltzmann numerical simulations. The computational set-up consists of a flat plate placed in proximity to a jet, replicating the interaction benchmark study carried out at NASA Glenn. Installation effects cause low-frequency noise increase with respect to the isolated case, mainly occurring in the direction normal to the plate and upstream of the jet’s exit plane. It is shown that the Helmholtz number, based on the wavelength of eddies in the mixing layer and their distance to the plate trailing edge, predicts the frequency range where installation noise occurs. Based on the isolated jet near field, scaling laws are also found for the far-field noise produced by different plate geometries. The linear hydrodynamic field of the isolated jet shows an exponential decay of pressure fluctuations in the radial direction; it is shown that the far-field spectrum follows the same trend when moving the plate in this direction. In the axial direction, spectral proper orthogonal decomposition is applied to filter out jet acoustic waves. The resultant hydrodynamic pressure fluctuations display a wavepacket behaviour, which can be fitted with a Gaussian envelope. It is found that installation noise for different plate lengths is proportional to the amplitude of the Gaussian curve at the position of the plate trailing edge. These analyses show that trends of jet-installation noise can be predicted by analysing the near field of the isolated case, reducing the need for extensive parametric investigations.
Understanding the factors that determine habitat use and abundance of exploited species is essential to develop effective conservation strategies. We studied the four forest pigeons on São Tomé Island to assess the species’ distribution and abundance patterns. We determined ecological factors likely to be associated with each species’ use of habitats and numbers, as well as the influence of hunting pressure. In total, 35 km of line transects were surveyed in the rainy season and at the start of the dry season. Pigeons differed in their use of habitats; there were also strong seasonality effects. The most abundant species was the Lemon Dove Columba simplex, the only non-hunted species. The São Tomé Green Pigeon Treron sanctithomae and Maroon Pigeon Columba thomensis were less abundant and had more restricted ranges. Both species were strongly associated with old-growth forests. In contrast, the Bronze-naped Pigeon Columba malherbii was relatively abundant and widespread; this species favours human-altered habitats such as shade forests and non-forested areas. Fruit availability measured within the different habitats was linked with the distribution and abundance of the three hunted species. Potential human predation pressure on all species was determined from hunting signs found along the surveyed transects. There was a significant negative correlation between the abundance of two of the hunted species and hunting pressure. Our results indicate the importance of adequately protecting old-growth and secondary forests as core habitats for the survival of viable populations of all pigeon species in the island. However, control of hunting is also crucial.
Extreme value statistics (EVS) is applied to the pixelized distribution of galaxy luminosities in the Sloan Digital Sky Survey (SDSS). We analyze the DR8 Main Galaxy Sample (MGS) as well as the Luminous Red Galaxy Sample (LRGS). A non-parametric comparison of the EVS of the luminosities with the Fisher-Tippett-Gumbel distribution (limit distribution for independent variables distributed by the Press-Schechter law) indicates a good agreement provided uncertainties arising both from the finite size of the samples and from the sample size distribution are accounted for. This effectively rules out the possibility of having a finite maximum cutoff luminosity.
Bipolar disorder (BD) is one of the leading causes of disability worldwide. Patients are further disadvantaged by delays in accurate diagnosis ranging between 5 and 10 years. We applied Gaussian process classifiers (GPCs) to structural magnetic resonance imaging (sMRI) data to evaluate the feasibility of using pattern recognition techniques for the diagnostic classification of patients with BD.
GPCs were applied to gray (GM) and white matter (WM) sMRI data derived from two independent samples of patients with BD (cohort 1: n = 26; cohort 2: n = 14). Within each cohort patients were matched on age, sex and IQ to an equal number of healthy controls.
The diagnostic accuracy of the GPC for GM was 73% in cohort 1 and 72% in cohort 2; the sensitivity and specificity of the GM classification were respectively 69% and 77% in cohort 1 and 64% and 99% in cohort 2. The diagnostic accuracy of the GPC for WM was 69% in cohort 1 and 78% in cohort 2; the sensitivity and specificity of the WM classification were both 69% in cohort 1 and 71% and 86% respectively in cohort 2. In both samples, GM and WM clusters discriminating between patients and controls were localized within cortical and subcortical structures implicated in BD.
Our results demonstrate the predictive value of neuroanatomical data in discriminating patients with BD from healthy individuals. The overlap between discriminative networks and regions implicated in the pathophysiology of BD supports the biological plausibility of the classifiers.
The seasonal and spatial pattern of diet composition of a population of wild rabbits Oryctolagus cuniculus L. occupying a southern Portuguese montado was estimated using the n-alkane technique. The diet was analysed in terms of components that are relevant to habitat management. The dietary categories considered were gum cistus leaves and flowers, cork oak and holm oak seedlings and acorns, cereals, olive tree regrowth and grass-forb species. The objectives were to assess the changes in diet across seasons in relation to the reproductive cycle of the rabbits, and to relate these changes to herbaceous biomass availability and to habitat structure, in terms of density of scrub cover and accessibility to arable crops. The results demonstrated that the diet was dominated by grass-forbs, and cereals when they were available. Browse was an important component of the diet and became more important in a year of low herbaceous biomass availability and in areas dominated by dense scrub. A similar phenomenon was observed in relation to consumption of acorns in winter. Seasonal and spatial variation in diet composition suggested a strategy aimed at maintaining a high quality diet. This was supported by the observed high dry matter digestibility of the diet during most of the year. The relevance of growing arable crops and providing fodder, as a means of increasing the carrying capacity of montados for rabbits and protecting the natural regeneration of trees, is discussed.
A series of tests have been performed to characterize the chemical stability of a DWPF borosilicate glass sample as part of the Waste Package Task of the NNWSI Project. This material was prepared at the Savannah River Laboratory for the purpose of testing the 165-frit matrix doped with a simulated non-radioactive waste. All tests were conducted at 90°C using deionized water and J-13 water (a tuffaceous formation groundwater). In the deionized water tests, both monoliths and crushed glass were tested at various ratios of surface area of the sample to volume of water in order to compare leach rates for different sample geometries or leaching times. Effects on the leach rates due to the presence of crushed tuff and stainless steel material were also investigated in the tests with J-13 water.
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