157 research outputs found
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
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
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
Biting behaviour of African malaria vectors : 1. Where do the main vector species bite on the human body?
BACKGROUND : Malaria control in Africa relies heavily on indoor vector management, primarily indoor residual
spraying and insecticide treated bed nets. Little is known about outdoor biting behaviour or even the dynamics of
indoor biting and infection risk of sleeping household occupants. In this paper we explore the preferred biting sites
on the human body and some of the ramifications regarding infection risk and exposure management.
METHODS : We undertook whole-night human landing catches of Anopheles arabiensis in South Africa and Anopheles
gambiae s.s. and Anopheles funestus in Uganda, for seated persons wearing short sleeve shirts, short pants, and bare
legs, ankles and feet. Catches were kept separate for different body regions and capture sessions. All An. gambiae s.
l. and An. funestus group individuals were identified to species level by PCR.
RESULTS : Three of the main vectors of malaria in Africa (An. arabiensis, An. gambiae s.s. and An. funestus) all have a
preference for feeding close to ground level, which is manifested as a strong propensity (77.3% – 100%) for biting
on lower leg, ankles and feet of people seated either indoors or outdoors, but somewhat randomly along the lower
edge of the body in contact with the surface when lying down. If the lower extremities of the legs (below mid-calf
level) of seated people are protected and therefore exclude access to this body region, vector mosquitoes do not
move higher up the body to feed at alternate body sites, instead resulting in a high (58.5% - 68.8%) reduction in
biting intensity by these three species.
CONCLUSIONS : Protecting the lower limbs of people outdoors at night can achieve a major reduction in biting
intensity by malaria vector mosquitoes. Persons sleeping at floor level bear a disproportionate risk of being bitten at
night because this is the preferred height for feeding by the primary vector species. Therefore it is critical to protect
children sleeping at floor level (bednets; repellent-impregnated blankets or sheets, etc.). Additionally, the
opportunity exists for the development of inexpensive repellent-impregnated anklets and/or sandals to discourage
vectors feeding on the lower legs under outdoor conditions at night.Bill & Melinda Gates Foundation through the Grand Challenges
Explorations initiative.http://www.parasitesandvectors.comhb201
Reconstruction of the gravitational wave signal 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 from the detector signals is
described. The standard consistency checks of the reconstruction are discussed
and used to estimate the systematic uncertainties of the signal as a
function of frequency. Finally, an independent setup, the photon calibrator, is
described and used to validate the reconstructed signal and the
associated uncertainties.
The uncertainties of the time series are estimated to be 8% in
amplitude. The uncertainty of the phase of is 50 mrad at 10 Hz with a
frequency dependence following a delay of 8 s at high frequency. A bias
lower than and depending on the sky direction of the GW is
also present.Comment: 35 pages, 16 figures. Accepted by CQ
Aedes species (Diptera: Culicidae) ecological and host feeding patterns in the north-eastern parts of South Africa, 2014–2018
Background
There is a paucity of recent data and knowledge on mosquito diversity and potential vectors of arboviruses in South Africa, with most of the available data dating back to the 1950s–1970s. Aedes and Culex species are the major vectors of some of the principal arboviruses which have emerged and re-emerged in the past few decades.
Methods
In this study we used entomological surveillance in selected areas in the north-eastern parts of South Africa from 2014 to 2018 to assess mosquito diversity, with special emphasis on the Aedes species. The impact of trap types and environmental conditions was also investigated. Identification of the blood meal sources of engorged females collected during the study period was carried out, and DNA barcodes were generated for selected species.
Results
Overall, 18.5% of the total Culicidae mosquitoes collected belonged to the genus Aedes, with 14 species recognised or suspected vectors of arboviruses. Species belonging to the Neomelaniconion subgenus were commonly collected in the Bushveld savanna at conservation areas, especially Aedes mcintoshi and Aedes circumluteolus. Aedes aegypti was present in all sites, albeit in low numbers. Temperature was a limiting factor for the Aedes population, and they were almost exclusively collected at temperatures between 18 °C and 27 °C. The cytochrome oxidase subunit I (COI) barcode fragment was amplified for 21 Aedes species, and for nine of these species it was the first sequence information uploaded on GenBank.
Conclusion
This study provides a better understanding of the diversity and relative abundance of Aedes species in the north-east of South Africa. The information provided here will contribute to future arboviral research and implementation of efficient vector control and prevention strategies
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
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
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
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
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