145 research outputs found
Remote sensing research for development at IDRC
Meeting: International Symposium on Remote Sensing of Environment, 20-26 Oct. 1988, Abidjan, C
Approche du CRDI dans la lutte contre la désertification en Afrique et l'apport de son programme en cartographie et télédétection
Réunion: DeuxiÚmes journées scientifiques du réseau thématique de l'UREF : télédétection, 21-24 nov. 1989, SNPhotocopi
Note préliminaire sur les effets expérimentaux de l'aflatoxine chez les bovins tropicaux. Effets de l'aflatoxine sur la vache laitiÚre et sur le jeune nourri à la mamelle
Cette premiĂšre expĂ©rimentation se situe dans le cadre d'un programme Ă long terme sur les effets de l'aflatoxine chez les bovins tropicaux. Elle a pour but de rechercher chez la vache en lactation, recevant une dose expĂ©rimentale volontairement forte de 1,5 mg d'aflatoxine par jour, les dĂ©sordres susceptibles d'ĂȘtre produits, chez la mĂšre et chez le jeune. Alors que les adultes semblent rĂ©sister Ă l'intoxication, les rĂ©percussions sont plus sensibles chez le jeune qui accuse un retard de croissance significatif. Les troubles observĂ©s chez les veaux Ă la mamelle paraissent liĂ©s Ă la prĂ©sence d'aflatoxine dans le lai
Note sur la présence d'aflatoxine dans les fanes d'arachides
Les fanes d'arachide constituent en pays arachidien et spécialement au Sénégal un aliment appété par les diverses espÚces animales. Des recherches effectuées sur ce fourrage au Laboratoire National de l'Elevage et de Recherches Vétérinaires de Dakar, ont révélé la présence d'aflatoxine de toxicité comparable à celle trouvée dans la graine et les tourteaux d'arachid
New Shortwave Infrared Albedo Measurements for Snow Specific Surface Area Retrieval
Snow grain-size characterization, its vertical and temporal evolution is a key parameter for the improvement and validation of snow and radiative transfer models (optical and microwave) as well as for remote-sensing retrieval methods. We describe two optical methods, one active and one passive shortwave infrared, for field determination of the specific surface area (SSA) of snow grains. We present a new shortwave infrared (SWIR) camera approach. This new method is compared with a SWIR laser- based system measuring snow albedo with an integrating sphere (InfraRed Integrating Sphere (IRIS)). Good accuracy (10%) and reproducibility in SSA measurements are obtained using the IRIS system on snow samples having densities greater than 200 kg m-3, validated against X-ray microtomography measurements. The SWIRcam approach shows improved sensitivity to snow SSA when compared to a near-infrared camera, giving a better contrast of the snow stratigraphy in a snow pit
Quantum Communication in Rindler Spacetime
A state that an inertial observer in Minkowski space perceives to be the
vacuum will appear to an accelerating observer to be a thermal bath of
radiation. We study the impact of this Davies-Fulling-Unruh noise on
communication, particularly quantum communication from an inertial sender to an
accelerating observer and private communication between two inertial observers
in the presence of an accelerating eavesdropper. In both cases, we establish
compact, tractable formulas for the associated communication capacities
assuming encodings that allow a single excitation in one of a fixed number of
modes per use of the communications channel. Our contributions include a
rigorous presentation of the general theory of the private quantum capacity as
well as a detailed analysis of the structure of these channels, including their
group-theoretic properties and a proof that they are conjugate degradable.
Connections between the Unruh channel and optical amplifiers are also
discussed.Comment: v3: 44 pages, accepted in Communications in Mathematical Physic
Limits on the ultra-bright Fast Radio Burst population from the CHIME Pathfinder
We present results from a new incoherent-beam Fast Radio Burst (FRB) search
on the Canadian Hydrogen Intensity Mapping Experiment (CHIME) Pathfinder. Its
large instantaneous field of view (FoV) and relative thermal insensitivity
allow us to probe the ultra-bright tail of the FRB distribution, and to test a
recent claim that this distribution's slope, , is quite small. A 256-input incoherent beamformer was
deployed on the CHIME Pathfinder for this purpose. If the FRB distribution were
described by a single power-law with , we would expect an FRB
detection every few days, making this the fastest survey on sky at present. We
collected 1268 hours of data, amounting to one of the largest exposures of any
FRB survey, with over 2.4\,\,10\,deg\,hrs. Having seen no
bursts, we have constrained the rate of extremely bright events to
\,sky\,day above \,220 Jy\,ms
for between 1.3 and 100\,ms, at 400--800\,MHz. The non-detection also
allows us to rule out with 95 confidence, after
marginalizing over uncertainties in the GBT rate at 700--900\,MHz, though we
show that for a cosmological population and a large dynamic range in flux
density, is brightness-dependent. Since FRBs now extend to large
enough distances that non-Euclidean effects are significant, there is still
expected to be a dearth of faint events and relative excess of bright events.
Nevertheless we have constrained the allowed number of ultra-intense FRBs.
While this does not have significant implications for deeper, large-FoV surveys
like full CHIME and APERTIF, it does have important consequences for other
wide-field, small dish experiments
SPT-3G: A Next-Generation Cosmic Microwave Background Polarization Experiment on the South Pole Telescope
We describe the design of a new polarization sensitive receiver, SPT-3G, for
the 10-meter South Pole Telescope (SPT). The SPT-3G receiver will deliver a
factor of ~20 improvement in mapping speed over the current receiver, SPTpol.
The sensitivity of the SPT-3G receiver will enable the advance from statistical
detection of B-mode polarization anisotropy power to high signal-to-noise
measurements of the individual modes, i.e., maps. This will lead to precise
(~0.06 eV) constraints on the sum of neutrino masses with the potential to
directly address the neutrino mass hierarchy. It will allow a separation of the
lensing and inflationary B-mode power spectra, improving constraints on the
amplitude and shape of the primordial signal, either through SPT-3G data alone
or in combination with BICEP-2/KECK, which is observing the same area of sky.
The measurement of small-scale temperature anisotropy will provide new
constraints on the epoch of reionization. Additional science from the SPT-3G
survey will be significantly enhanced by the synergy with the ongoing optical
Dark Energy Survey (DES), including: a 1% constraint on the bias of optical
tracers of large-scale structure, a measurement of the differential Doppler
signal from pairs of galaxy clusters that will test General Relativity on ~200
Mpc scales, and improved cosmological constraints from the abundance of
clusters of galaxies.Comment: 21 pages, 9 figures. To be published in Proceedings of SPIE Volume
9153. Presented at SPIE Astronomical Telescopes + Instrumentation 2014,
conference 915
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