Continuous, Semi-discrete, and Fully Discretized Navier-Stokes Equations

The Navier--Stokes equations are commonly used to model and to simulate flow phenomena. We introduce the basic equations and discuss the standard methods for the spatial and temporal discretization. We analyse the semi-discrete equations -- a semi-explicit nonlinear DAE -- in terms of the strangeness index and quantify the numerical difficulties in the fully discrete schemes, that are induced by the strangeness of the system. By analyzing the Kronecker index of the difference-algebraic equations, that represent commonly and successfully used time stepping schemes for the Navier--Stokes equations, we show that those time-integration schemes factually remove the strangeness. The theoretical considerations are backed and illustrated by numerical examples.Comment: 28 pages, 2 figure, code available under DOI: 10.5281/zenodo.998909, https://doi.org/10.5281/zenodo.99890

Reconstruction of the gravitational wave signal h(t)h(t) during the Virgo science runs and independent validation with a photon calibrator

The Virgo detector is a kilometer-scale interferometer for gravitational wave detection located near Pisa (Italy). About 13 months of data were accumulated during four science runs (VSR1, VSR2, VSR3 and VSR4) between May 2007 and September 2011, with increasing sensitivity. In this paper, the method used to reconstruct, in the range 10 Hz-10 kHz, the gravitational wave strain time series $h(t)$ from the detector signals is described. The standard consistency checks of the reconstruction are discussed and used to estimate the systematic uncertainties of the $h(t)$ signal as a function of frequency. Finally, an independent setup, the photon calibrator, is described and used to validate the reconstructed $h(t)$ signal and the associated uncertainties. The uncertainties of the $h(t)$ time series are estimated to be 8% in amplitude. The uncertainty of the phase of $h(t)$ is 50 mrad at 10 Hz with a frequency dependence following a delay of 8 $\mu$s at high frequency. A bias lower than $4\,\mathrm{\mu s}$ and depending on the sky direction of the GW is also present.Comment: 35 pages, 16 figures. Accepted by CQ

Gravitational Waves From Known Pulsars: Results From The Initial Detector Era

We present the results of searches for gravitational waves from a large selection of pulsars using data from the most recent science runs (S6, VSR2 and VSR4) of the initial generation of interferometric gravitational wave detectors LIGO (Laser Interferometric Gravitational-wave Observatory) and Virgo. We do not see evidence for gravitational wave emission from any of the targeted sources but produce upper limits on the emission amplitude. We highlight the results from seven young pulsars with large spin-down luminosities. We reach within a factor of five of the canonical spin-down limit for all seven of these, whilst for the Crab and Vela pulsars we further surpass their spin-down limits. We present new or updated limits for 172 other pulsars (including both young and millisecond pulsars). Now that the detectors are undergoing major upgrades, and, for completeness, we bring together all of the most up-to-date results from all pulsars searched for during the operations of the first-generation LIGO, Virgo and GEO600 detectors. This gives a total of 195 pulsars including the most recent results described in this paper.United States National Science FoundationScience and Technology Facilities Council of the United KingdomMax-Planck-SocietyState of Niedersachsen/GermanyAustralian Research CouncilInternational Science Linkages program of the Commonwealth of AustraliaCouncil of Scientific and Industrial Research of IndiaIstituto Nazionale di Fisica Nucleare of ItalySpanish Ministerio de Economia y CompetitividadConselleria d'Economia Hisenda i Innovacio of the Govern de les Illes BalearsNetherlands Organisation for Scientific ResearchPolish Ministry of Science and Higher EducationFOCUS Programme of Foundation for Polish ScienceRoyal SocietyScottish Funding CouncilScottish Universities Physics AllianceNational Aeronautics and Space AdministrationOTKA of HungaryLyon Institute of Origins (LIO)National Research Foundation of KoreaIndustry CanadaProvince of Ontario through the Ministry of Economic Development and InnovationNational Science and Engineering Research Council CanadaCarnegie TrustLeverhulme TrustDavid and Lucile Packard FoundationResearch CorporationAlfred P. Sloan FoundationAstronom

A First Search for coincident Gravitational Waves and High Energy Neutrinos using LIGO, Virgo and ANTARES data from 2007

We present the results of the first search for gravitational wave bursts associated with high energy neutrinos. Together, these messengers could reveal new, hidden sources that are not observed by conventional photon astronomy, particularly at high energy. Our search uses neutrinos detected by the underwater neutrino telescope ANTARES in its 5 line configuration during the period January - September 2007, which coincided with the fifth and first science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed for candidate gravitational-wave signals coincident in time and direction with the neutrino events. No significant coincident events were observed. We place limits on the density of joint high energy neutrino - gravitational wave emission events in the local universe, and compare them with densities of merger and core-collapse events.Comment: 19 pages, 8 figures, science summary page at http://www.ligo.org/science/Publication-S5LV_ANTARES/index.php. Public access area to figures, tables at https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=p120000

Swift follow-up observations of candidate gravitational-wave transient events

We present the first multi-wavelength follow-up observations of two candidate gravitational-wave (GW) transient events recorded by LIGO and Virgo in their 2009-2010 science run. The events were selected with low latency by the network of GW detectors and their candidate sky locations were observed by the Swift observatory. Image transient detection was used to analyze the collected electromagnetic data, which were found to be consistent with background. Off-line analysis of the GW data alone has also established that the selected GW events show no evidence of an astrophysical origin; one of them is consistent with background and the other one was a test, part of a "blind injection challenge". With this work we demonstrate the feasibility of rapid follow-ups of GW transients and establish the sensitivity improvement joint electromagnetic and GW observations could bring. This is a first step toward an electromagnetic follow-up program in the regime of routine detections with the advanced GW instruments expected within this decade. In that regime multi-wavelength observations will play a significant role in completing the astrophysical identification of GW sources. We present the methods and results from this first combined analysis and discuss its implications in terms of sensitivity for the present and future instruments.Comment: Submitted for publication 2012 May 25, accepted 2012 October 25, published 2012 November 21, in ApJS, 203, 28 ( http://stacks.iop.org/0067-0049/203/28 ); 14 pages, 3 figures, 6 tables; LIGO-P1100038; Science summary at http://www.ligo.org/science/Publication-S6LVSwift/index.php ; Public access area to figures, tables at https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=p110003

Seasonal variation in the relative dominance of herbivore guilds in an African savanna

African savannas are highly seasonal with a diverse array of both mammalian and invertebrate herbivores, yet herbivory studies have focused almost exclusively on mammals. We conducted a 2-yr exclosure experiment in South Africa's Kruger National Park to measure the relative impact of these two groups of herbivores on grass removal at both highly productive patches (termite mounds) and in the less productive savanna matrix. Invertebrate and mammalian herbivory was greater on termite mounds, but the relative importance of each group changed over time. Mammalian offtake was higher than invertebrates in the dry season, but can be eclipsed by invertebrates during the wet season when this group is more active. Our results demonstrate that invertebrates play a substantial role in savanna herbivory and should not be disregarded in attempts to understand the impacts of herbivory on ecosystems

Macrocheles species (Acari: Macrochelidae) associated with human corpses in Europe

The biology of macrochelid mites might offer new venues for the interpretation of the environmental conditions surrounding human death and decomposition. Three human corpses, one from Sweden and two from Spain, have been analysed for the occurrence of Macrochelidae species. Macrocheles muscaedomesticae females were associated with a corpse that was found in a popular beach area of southeast Spain. Their arrival coincides with the occurrence of one of their major carrier species, the filth fly Fannia scalaris, the activity of which peaks during mid-summer. M. glaber specimens were collected from a corpse in a shallow grave in a forest in Sweden at the end of summer, concurrent with the arrival of beetles attracted by odours from the corpse. M. perglaber adults were sampled from a corpse found indoors in the rural surroundings of Granada city, Spain. The phoretic behaviour of this species is similar to that of M. glaber, but being more specific to Scarabaeidae and Geotrupidae dung beetles, most of which favour human faeces. M. muscaedomesticae is known from urban and rural areas and poultry farms; M. glaber from outdoors, particularly the countryside; while M. perglaber from outdoor, rural, and remote, potentially mountainous locations. M. muscaedomesticae and M. perglaber are reported for the first time from the Iberian Peninsula. This is the first record of M. perglaber from human remains

Macrocheles species (Acari: Macrochelidae) associated with human corpses in Europe

The biology of macrochelid mites might offer new venues for the interpretation of the environmental conditions surrounding human death and decomposition. Three human corpses, one from Sweden and two from Spain, have been analysed for the occurrence of Macrochelidae species. Macrocheles muscaedomesticae females were associated with a corpse that was found in a popular beach area of southeast Spain. Their arrival coincides with the occurrence of one of their major carrier species, the filth fly Fannia scalaris, the activity of which peaks during mid-summer. M. glaber specimens were collected from a corpse in a shallow grave in a forest in Sweden at the end of summer, concurrent with the arrival of beetles attracted by odours from the corpse. M. perglaber adults were sampled from a corpse found indoors in the rural surroundings of Granada city, Spain. The phoretic behaviour of this species is similar to that of M. glaber, but being more specific to Scarabaeidae and Geotrupidae dung beetles, most of which favour human faeces. M. muscaedomesticae is known from urban and rural areas and poultry farms; M. glaber from outdoors, particularly the countryside; while M. perglaber from outdoor, rural, and remote, potentially mountainous locations. M. muscaedomesticae and M. perglaber are reported for the first time from the Iberian Peninsula. This is the first record of M. perglaber from human remains

Experimental inoculation of plants and animals with Ebola virus.

Thirty-three varieties of 24 species of plants and 19 species of vertebrates and invertebrates were experimentally inoculated with Ebola Zaire virus. Fruit and insectivorous bats supported replication and circulation of high titers of virus without necessarily becoming ill; deaths occurred only among bats that had not adapted to the diet fed in the laboratory

Field study site selection, species abundance and monthly distribution of anopheline mosquitoes in the northern Kruger National Park, South Africa

BACKGROUND: Knowledge of the ecology and behaviour of a target species is a prerequisite for the successful development of any vector control strategy. Before the implementation of any strategy it is essential to have comprehensive information on the bionomics of species in the targeted area. The aims of this study were to conduct regular entomological surveillance and to determine the relative abundance of anopheline species in the northern Kruger National Park. In addition to this, the impact of weather conditions on an Anopheles arabiensis population were evaluated and a range of mosquito collection methods were assessed. METHODS: A survey of Anopheles species was made between July 2010 and December 2012. Mosquitoes were collected from five sites in the northern Kruger National Park, using carbon dioxide-baited traps, human landing and larval collections. Specimens were identified morphologically and polymerase chain reaction assays were subsequently used where appropriate. RESULTS: A total of 3,311 specimens belonging to nine different taxa was collected. Species collected were: Anopheles arabiensis (n = 1,352), Anopheles quadriannulatus (n = 870), Anopheles coustani (n = 395), Anopheles merus (n = 349), Anopheles pretoriensis (n = 35), Anopheles maculipalpis (n = 28), Anopheles rivulorum (n = 19), Anopheles squamosus (n = 3) and Anopheles rufipes (n = 2). Members of the Anopheles gambiae species complex were the most abundant and widely distributed, occurring across all collection sites. The highest number of mosquitoes was collected using CO2 baited net traps (58.2%) followed by human landing catches (24.8%). Larval collections (17%) provided an additional method to increase sample size. Mosquito sampling productivity was influenced by prevailing weather conditions and overall population densities fluctuated with seasons. CONCLUSION: Several anopheline species occur in the northern Kruger National Park and their densities fluctuate between seasons. Species abundance and relative proportions within the An. gambiae complex varied between collection methods. There is a perennial presence of an isolated population of An. arabiensis at the Malahlapanga site which declined in density during the dry winter months, making this site suitable for a small pilot study site for Sterile Insect Technique as a malaria vector control strategy.The National Research Foundation and by the International Atomic Energy Agency (Contract no SAF16780 (under the G34002) and CRPG34002).http://www.malariajournal.com/am201