1,894 research outputs found
High SiO abundance in the HH212 protostellar jet
Previous SiO maps of the innermost regions of HH212 set strong constraints on
the structure and origin of this jet. They rule out a fast wide-angle wind, and
tentatively favor a magneto-centrifugal disk wind launched out to 0.6 AU. We
aim to assess the SiO content at the base of the HH212 jet to set an
independent constraint on the location of the jet launch zone with respect to
the dust sublimation radius. We present the first sub-arcsecond (0"44x0"96) CO
map of the HH212 jet base, obtained with the IRAM Plateau de Bure
Interferometer. Combining this with previous SiO(5-4) data, we infer the
CO(2-1) opacity and mass-flux in the high-velocity jet and arrive at a much
tighter lower limit to the SiO abundance than possible from the (optically
thick) SiO emission alone. Gas-phase SiO at high velocity contains at least 10%
of the elemental silicon if the jet is dusty, and at least 40% if the jet is
dust-free, if CO and SiO have similar excitation temperatures. Such a high SiO
content is challenging for current chemical models of both dust-free winds and
dusty interstellar shocks. Updated chemical models (equatorial dust-free winds,
highly magnetized dusty shocks) and observations of higher J CO lines are
required to elucidate the dust content and launch radius of the HH212
high-velocity jet.Comment: 4 pages, 2 figure
Unconventional aspects of electronic transport in delafossite oxides
The electronic transport properties of the delafossite oxides ABO are
usually understood in terms of two well separated entities, namely, the
triangular A and (BO) layers. Here we review several cases among
this extensive family of materials where the transport depends on the
interlayer coupling and displays unconventional properties. We review the doped
thermoelectrics based on CuRhO and CuCrO, which show a high-temperature
recovery of Fermi-liquid transport exponents, as well as the highly anisotropic
metals PdCoO, PtCoO and PdCrO where the sheer simplicity of the
Fermi surface leads to unconventional transport. We present some of the
theoretical tools that have been used to investigate these transport properties
and review what can and cannot be learned from the extensive set of electronic
structure calculations that have been performed.Comment: 35 pages, 19 figure
Intrinsic effects of substitution and intercalation on thermal transport in two-dimensional TiS single crystals
The promising thermoelectric material TiS can be easily chemically doped
and intercalated. We present here studies of single crystals that are
intercalated with excess Ti or Co, or substituted with Ta. We demonstrate the
intrinsic impact of these dopants on the thermal transport in the absence of
grain boundary scattering. We show that Ta doping has the greatest impact on
the thermal scattering rate per ion added, leading to a five-fold reduction in
the lattice thermal conductivity as compared to stoichiometric single crystals.Comment: 5 pages, 2 figure
Large anisotropic thermal conductivity of intrinsically two-dimensional metallic oxide PdCoO
The highly conductive layered metallic oxide \pdcoo{} is a near-perfect
analogue to an alkali metal in two dimensions. It is distinguished from other
two-dimensional electron systems where the Fermi surface does not reach the
Brillouin zone boundary by a high planar electron density exceeding
cm. The simple single-band quasi-2D electronic structure results in
strongly anisotropic transport properties and limits the effectiveness of
electron-phonon scattering. Measurements on single crystals in the temperature
range from 10-300K show that the thermal conductivity is much more weakly
anisotropic than the electrical resistivity, as a result of significant phonon
heat transport. The in-plane thermoelectric power is linear in temperature at
300\,K and displays a purity-dependent peak around 50K. Given the extreme
simplicity of the band-structure, it is possible to identify this peak with
phonon drag driven by normal electron-phonon scattering processes.Comment: 3 figure
Short Communication : Long-term intake of the illegal diet pill DNP reduces lifespan in a captive bird model
Acknowledgements The authors wish to thank A. Hranitzky for support in bird mainte-nance, numerous students for their help in data collection, and N. Metcalfe, S. Dobson as well as S. Reichert for helpful comments on a previous draft. Funding AS was funded by a Marie Sklodowska-Curie Postdoctoral Fellowship (#658085) and a TCSM fellowship at the time of analyzing the results and writing the manuscriptPeer reviewedPostprin
Seed Spillage from Grain Trailers on Road Verges during Oilseed Rape Harvest: An Experimental Survey
Context: Anthropogenic vectors enhance the natural dispersal capacity of plant seeds significantly in terms of quantity and distance. Human-mediated seed dispersal (i.e. anthropochory) greatly increases the dispersal of crop species across agroecosystems. In the case of oilseed rape (OSR), spillage of seeds from grain trailers during harvest has never been quantified. Methods: Our experimental approach involved establishing 85 seed trap-sites on the road verges of an agricultural area around the grain silo of Selommes (Loir-et-Cher, France). We recorded OSR spillage during harvest and applied a linear model to the data. Results: The amount of seed spilled was related positively to the area of the OSR fields served by the road, whereas the amount of seed spilled decreased with other variables, such as distance from the trap-site to the verge of the road and to the nearest field. The distance to the grain silo, through local and regional effects, affected seed loss. Local effects from fields adjacent to the road resulted in a cumulative spillage on one-lane roads. On two-lane roads, spillage was nearly constant whatever the distance to the silo due to a mixture of these local effects and of grain trailers that joined the road from more distant fields. From the data, we predicted the number of seeds lost from grain trailers on one road verge in the study area. We predicted a total spillage of 2.05610 6 seeds (64.76610 5) along the road length, which represented
Problématique des systÚmes miniaturisés in-vivo pour le remplacement d'une fonction dans le milieu médical orthopédique
Cet article propose une synthĂšse des systĂšmes orthopĂ©diques instrumentĂ©s afin de dĂ©gager les Ă©tudes qui pourraient conduire Ă une amĂ©lioration des prothĂšses. Pour cela, nous mettons en Ă©vidence l'intĂ©rĂȘt d'utiliser des systĂšmes in vivo auto adaptatifs pour le remplacement d'une fonction dans le domaine orthopĂ©dique. Or dans ce domaine, il n'existe pour l'instant que des systĂšmes pour l'instrumentation des prothĂšses. Nous prĂ©sentons Ă©galement la problĂ©matique de l'alimentation de ces systĂšmes et quelques idĂ©es de gĂ©nĂ©rateurs basĂ©es sur la rĂ©cupĂ©ration d'une Ă©nergie primaire produite par le corps humain
Reversible optical doping of graphene
The ultimate surface exposure provided by graphene monolayer makes it the
ideal sensor platform but also exposes its intrinsic properties to any
environmental perturbations. In this work, we demonstrate that the charge
carrier density of graphene exfoliated on a SiO/Si substrate can be finely
and reversibly tuned between electron and hole doping with visible photons.
This photo-induced doping happens under moderate laser power conditions but is
significantly affected by the substrate cleaning method. In particular, it is
found to require hydrophilic substrates and to vanish in suspended graphene.
These findings suggest that optically gated graphene devices operating with a
sub-second time scale can be envisioned but also that Raman spectroscopy is not
always as non-invasive as generally assumed
Ăvreux â Le Clos au Duc, 3bis rue de la LibĂ©ration
Identifiant de l'opĂ©ration archĂ©ologique : 27 229 005 Date de l'opĂ©ration : 2005 (EX) Le diagnostic rĂ©alisĂ© a Ă©tĂ© motivĂ© par la construction dâun logement individuel au cĆur de la nĂ©cropole antique (Fig. n°1 : Localisation des opĂ©rations de terrain). Lâemprise au sol de la construction est de 193 m2 et la parcelle concernĂ©e de 1 811 m2. La nĂ©cropole antique du « Clos au Duc » est situĂ©e Ă flanc de coteau, au sud de la ville, le long de la voie reliant Ăvreux Ă Chartres. Elle est connue dep..
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