5,908 research outputs found
Growth and nutritional response of Nemared peach rootstock infected with Pratylenchus vulnus and the mycorrhizal fungus Glomus mosseae
Les effets de l'interaction entre #Pratylenchus vulnus et le champignon mycorrhizien #Glomus mosseae sur les porte-greffe de pĂȘcher "Nemared" ont Ă©tĂ© Ă©tudiĂ©s en microparcelles pendant deux saisons de croissance. Le poids frais des pieds, le diamĂštre de la tige, la longueur des pieds et le poids frais des racines sont significativement plus faibles chez les pieds infestĂ©s par le nĂ©matode - qu'ils soient ou non colonisĂ©s par #G. mosseae Ă l'aide de mycorrhizes provoquent une diminution de la population finale du nĂ©matode et du nombre de nĂ©matodes par gramme de racine par rapport aux pieds infestĂ©s par #P. vulnus et non traitĂ©s Ă l'aide du champignon. La colonisation par les mycorrhizes n'est pas affectĂ©e par la prĂ©sence du nĂ©matode. Chez les pieds infestĂ©s par le nĂ©matode, le Cu est le seul Ă©lĂ©ment dĂ©ficitaire dĂ©tectĂ© par analyse foliaire, quoique des taux faibles de fer y aient Ă©tĂ© observĂ©s. Les taux les plus Ă©levĂ©s de Ma, Mg, Mn et Zn ont Ă©tĂ© dĂ©tectĂ©s chez les pieds infestĂ©s par #P. vulnus. Les pieds mycorrhizĂ©s recĂšlent les taux les plus Ă©levĂ©s de Cu et d'Al. #G. mosseae est bĂ©nĂ©fique pour la croissance des pĂȘchers "Nemared" mais ne leur confĂšre aucune protection contre #P. vulnus. (RĂ©sumĂ© d'auteur
Integrating ASCAT surface soil moisture and GEOV1 leaf area index into the SURFEX modelling platform: a land data assimilation application over France
The land monitoring service of the European Copernicus programme has
developed a set of satellite-based biogeophysical products, including
surface soil moisture (SSM) and leaf area index (LAI). This study
investigates the impact of joint assimilation of remotely sensed SSM
derived from Advanced Scatterometer (ASCAT) backscatter data and the
Copernicus Global Land GEOV1 satellite-based LAI product
into the the vegetation growth version of the Interactions
between Soil Biosphere Atmosphere (ISBA-A-gs) land surface model
within the the externalised surface model (SURFEX) modelling
platform of Météo-France. The ASCAT data were bias corrected with
respect to the model climatology by using a seasonal-based CDF
(Cumulative Distribution Function) matching technique. A multivariate
multi-scale land data assimilation system (LDAS) based on the extended
Kalman Filter (EKF) is used for monitoring the soil moisture,
terrestrial vegetation, surface carbon and energy fluxes across the
domain of France at a spatial resolution of 8 km. Each model grid
box is divided into a number of land covers, each having its own set of
prognostic variables. The filter algorithm is designed to provide
a distinct analysis for each land cover while using one observation
per grid box. The updated values are aggregated by computing
a weighted average.
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In this study, it is demonstrated that the assimilation scheme works
effectively within the ISBA-A-gs model over a four-year period
(2008â2011). The EKF is able to extract useful information from the
data signal at the grid scale and distribute the root-zone soil
moisture and LAI increments throughout the mosaic structure of the
model. The impact of the assimilation on the vegetation phenology and
on the water and carbon fluxes varies from one season to another. The
spring drought of 2011 is an interesting case study of the
potential of the assimilation to improve drought
monitoring. A comparison between simulated and in situ soil moisture
gathered at the twelve SMOSMANIA (Soil Moisture Observing
SystemâMeteorological Automatic Network Integrated Application) stations shows improved anomaly
correlations for eight stations
Unveiling the Structure of Pre-Transitional Disks
In the past few years, several disks with inner holes that are empty of small
dust grains have been detected and are known as transitional disks. Recently,
Spitzer has identified a new class of "pre-transitional disks" with gaps; these
objects have an optically thick inner disk separated from an optically thick
outer disk by an optically thin disk gap. A near-infrared spectrum provided the
first confirmation of a gap in the pre-transitional disk of LkCa 15 by
verifying that the near-infrared excess emission in this object was due to an
optically thick inner disk. Here we investigate the difference between the
nature of the inner regions of transitional and pre-transitional disks using
the same veiling-based technique to extract the near-infrared excess emission
above the stellar photosphere. We show that the near-infrared excess emission
of the previously identified pre-transitional disks of LkCa 15 and UX Tau A in
Taurus as well as the newly identified pre-transitional disk of ROX 44 in
Ophiuchus can be fit with an inner disk wall located at the dust destruction
radius. We also model the broad-band SEDs of these objects, taking into account
the effect of shadowing by the inner disk on the outer disk, considering the
finite size of the star. The near-infrared excess continua of these three
pre-transitional disks, which can be explained by optically thick inner disks,
are significantly different from that of the transitional disks of GM Aur,
whose near-infrared excess continuum can be reproduced by emission from
sub-micron-sized optically thin dust, and DM Tau, whose near-infrared spectrum
is consistent with a disk hole that is relatively free of small dust. The
structure of pre-transitional disks may be a sign of young planets forming in
these disks and future studies of pre-transitional disks will provide
constraints to aid in theoretical modeling of planet formation.Comment: Accepted for publication in ApJ on May 10, 2010; 29 page
A simplified protocol for detecting two systemic bait markers (Rhodamine B and iophenoxic acid) in small mammals
We developed a method of quantifying levels of fluorescence in the whiskers of wild stoats (Mustela erminea) using fluorescence microscopy and Axiovision 3.0.6.1 software. The method allows for discrimination between natural fluorescence present in or on a whisker, and the fluorescence resulting from the ingestion of the systemic marker Rhodamine B (RB), although some visual judgement is still required. We also developed a new high performance liquid chromatography (HPLC) protocol for detecting the systemic marker iophenoxic acid (IPA) in the blood of laboratory rats (Rattus norvegicus) and wild stoats. With this method, the blood of an animal that has consumed IPA can be tested for the presence of the foreign IPA compound itself. This is a more reliable test than the previous method, which measured the raised level of natural blood protein-bound iodine correlated with IPA absorption. The quantity of blood required from animal subjects is very small (10 ÎŒl), so the testing is less intrusive and the method can be extended to smaller species. The extraction technique uses methanol, rather than acids and heavy metal salts, thereby simplifying the procedure. Recovery of IPA is quantitative, giving a highly reliable reading. In experiments on captive rats the IPA method proved successful. Of 12 positively marked carcasses, two that had not been frozen for the 24 h before blood samples were taken showed relatively lower IPA levels. The same IPA detection method, as well as the whisker analysis for RB, was applied successfully to a population of wild stoats to which both Rhodamine B and IPA were made available at bait stations. The presence of both bait markers was detectable in rats for at least 21 days and in stoats for at least 27 days
The Truncated Disk of CoKu Tau/4
We present a model of a dusty disk with an inner hole which accounts for the
Spitzer Space Telescope Infrared Spectrograph observations of the low-mass
pre-main sequence star CoKu Tau/4. We have modeled the mid-IR spectrum (between
8 and 25 mic) as arising from the inner wall of a disk. Our model disk has an
evacuated inner zone of radius ~ 10 AU, with a dusty inner ``wall'', of
half-height ~ 2 AU, that is illuminated at normal incidence by the central
star. The radiative equilibrium temperature decreases from the inner disk edge
outward through the optically-thick disk; this temperature gradient is
responsible for the emission of the silicate bands at 10 and 20 mic. The
observed spectrum is consistent with being produced by Fe-Mg amorphous glassy
olivine and/or pyroxene, with no evidence of a crystalline component. The
mid-infrared spectrum of CoKu Tau/4 is reminiscent of that of the much older
star TW Hya, where it has been suggested that the significant clearing of its
inner disk is due to planet formation. However, no inner disk remains in CoKu
Tau/4, consistent with the star being a weak-emission (non-accreting) T Tauri
star. The relative youth of CoKu Tau/4 (~ 1 Myr) may indicate much more rapid
planet formation than typically assumed.Comment: 32 pages, 9 figures, accepted in Ap
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