117,749 research outputs found
Biological control of Plutella xylostella (L.) : Selection of the best trichogramma strains from biological characteristics
No full textThe diamondback moth Prutella xylostella (L.) (Lepidoptera: Plutellidae) is present in most continents. Control of this pest costs one billion Euros per year worldwide. It is a resistant to most insecticides and even to Bacillus thuringiensis (Berliner) and biological control is a strategy to be considered.[br/]
trichogramma (Hymenoptera: trichogrammatidae) present some obvious advantages for use in biological control. These egg parasitoids can easily be reared on a facilitious host and are found naturally on P. xylostella (Tabone et al, 2000)
Travaux sur la lutte biologique à l' Institut National de la Recherche Agronomique INRA Sophia-Antipolis
No full textElisabeth Tabone est responsable de programmes de lutte biologique contre les Lépidptères ravageurs des cultures au sein de l' Unité de lutte biologique de l' INRA PACA à Sophia-Antipolis.[br/]
"Nous recherchons des auxiliaires adaptés à la lutte biologique pour préserver des espèces végétales généralement atteintes par des ravageurs et notamment lorsqu' il existe une réelle urgence, c' est à dire lorsqu' aucune solution n' apparaît en AB ou en protection Intégrée.[br/]
L' objectif est de réduire les pesticides et de protéger au mieux l' environnement. Afin d' optimiser au mieux mes recherches, je développe les projets en associant des recherches à la fois fondamentales et appliquées, selon la pertinence des besoins rencontrés tout au long des différentes étapes étudiées."
Effect of MHD Wind-driven Disk Evolution on the Observed Sizes of Protoplanetary Disks
No full textAbstract
It is still unclear whether the evolution of protoplanetary disks, a key ingredient in the theory of planet formation, is driven by viscous turbulence or magnetic disk winds. As viscously evolving disks expand outward over time, the evolution of disk sizes is a discriminant test for studying disk evolution. However, it is unclear how the observed disk size changes over time if disk evolution is driven by magnetic disk winds. Combining the thermo-chemical code DALI with the analytical wind-driven disk-evolution model presented in Tabone et al., we study the time evolution of the observed gas outer radius as measured from CO rotational emission (R
CO,90%). The evolution of R
CO,90% is driven by the evolution of the disk mass, as the physical radius stays constant over time. For a constant α
DW
, an extension of the α Shakura–Sunyaev parameter to wind-driven accretion, R
CO,90% decreases linearly with time. Its initial size is set by the disk mass and the characteristic radius R
c,0, but only R
c,0 affects the evolution of R
CO,90%, with a larger R
c,0 resulting in a steeper decrease of R
CO,90%. For a time-dependent α
DW
, R
CO,90% stays approximately constant during most of the disk lifetime until R
CO,90% rapidly shrinks as the disk dissipates. The constant α
DW
models are able to reproduce the observed gas disk sizes in the ∼1–3 Myr old Lupus and ∼5–11 Myr old Upper Sco star-forming regions. However, they likely overpredict the gas disk size of younger (⪅0.7 Myr) disks
Meta qabdu miegħi l-irwiefen
No full textĠabra ta’ poeżiji u proża li tinkludi: Xtrawlu l-ħut fil-baħar ta’ Lawrence Mizzi – Il-mewt ta’ Rużar Briffa – F’Marsalforn ta’ Ġużè Cardona – Wara l-anestesija ta’ George Zammit – Int ma tgħid xejn? ta’ Norbert M. DeGabriele – Veritas offendit ta’ A. Tabone – Filosfu ta’ D. Mintoff – Lil missieri b’qima ta’ Mario Agius – Meta qabdu miegħi l-irwiefen ta’ Anton Buttigieg.peer-reviewe
Biological control of Plutella xylostella (L.): Selection of the best trichogramma strains from biological characteristics
No full textInternational audienceThe diamondback moth Prutella xylostella (L.) (Lepidoptera: Plutellidae) is present in most continents. Control of this pest costs one billion Euros per year worldwide. It is a resistant to most insecticides and even to Bacillus thuringiensis (Berliner) and biological control is a strategy to be considered. trichogramma (Hymenoptera: trichogrammatidae) present some obvious advantages for use in biological control. These egg parasitoids can easily be reared on a facilitious host and are found naturally on P. xylostella (Tabone et al, 2000)
Biological control of Plutella xylostella (L.): Selection of the best trichogramma strains from biological characteristics
No full textInternational audienceThe diamondback moth Prutella xylostella (L.) (Lepidoptera: Plutellidae) is present in most continents. Control of this pest costs one billion Euros per year worldwide. It is a resistant to most insecticides and even to Bacillus thuringiensis (Berliner) and biological control is a strategy to be considered. trichogramma (Hymenoptera: trichogrammatidae) present some obvious advantages for use in biological control. These egg parasitoids can easily be reared on a facilitious host and are found naturally on P. xylostella (Tabone et al, 2000)
How Large Is a Disk—What Do Protoplanetary Disk Gas Sizes Really Mean?
No full textIt remains unclear what mechanism is driving the evolution of protoplanetary disks. Direct detection of the main candidates, either turbulence driven by magnetorotational instabilities or magnetohydrodynamical disk winds, has proven difficult, leaving the time evolution of the disk size as one of the most promising observables able to differentiate between these two mechanisms. But to do so successfully, we need to understand what the observed gas disk size actually traces. We studied the relation between R _CO,90% , the radius that encloses 90% of the ^12 CO flux, and R _c , the radius that encodes the physical disk size, in order to provide simple prescriptions for conversions between these two sizes. For an extensive grid of thermochemical models, we calculate R _CO,90% from synthetic observations and relate properties measured at this radius, such as the gas column density, to bulk disk properties, such as R _c and the disk mass M _disk . We found an empirical correlation between the gas column density at R _CO,90% and disk mass: . Using this correlation we derive an analytical prescription of R _CO,90% that only depends on R _c and M _disk . We derive R _c for disks in Lupus, Upper Sco, Taurus, and the DSHARP sample, finding that disks in the older Upper Sco region are significantly smaller (〈 R _c 〉 = 4.8 au) than disks in the younger Lupus and Taurus regions (〈 R _c 〉 = 19.8 and 20.9 au, respectively). This temporal decrease in R _c goes against predictions of both viscous and wind-driven evolution, but could be a sign of significant external photoevaporation truncating disks in Upper Sco
Importance of source structure on complex organics emission III. Effect of disks around massive protostars
No full textComplex organic molecules are only detected toward a fraction of high-mass
protostars. The goal of this work is to investigate whether high-mass disks can
explain the lack of methanol emission from some massive protostellar systems.
We consider an envelope-only and an envelope-plus-disk model and use RADMC-3D
to calculate the methanol emission. High and low millimeter (mm) opacity dust
are considered for both models separately and the methanol abundance is
parameterized. Viscous heating is included due to the high accretion rates of
these objects in the disk. In contrast with low-mass protostars, the presence
of a disk does not significantly affect the temperature structure and methanol
emission. The shadowing effect of the disk is not as important for high-mass
objects and the disk mid-plane is hot because of viscous heating, which is
effective due to the high accretion rates. Consistent with observations of
infrared absorption lines toward high-mass protostars, we find a vertical
temperature inversion, i.e. higher temperatures in the disk mid-plane than the
disk surface, at radii < 50au for the models with L and
large mm opacity dust as long as the envelope mass is >550 M. The
large observed scatter in methanol emission from massive protostars can be
mostly explained toward lower luminosity objects with the envelope-plus-disk
models including low and high mm opacity dust. The methanol emission variation
toward sources with high luminosities cannot be explained by models with or
without a disk. However, the of these objects suggest that they could be
associated with hypercompact/ultracompact HII regions. Therefore, the low
methanol emission toward the high-luminosity sources can be explained by them
hosting an HII region where methanol is absent.Comment: 25 pages, 24 figures, Accepted for publication in A&
Didattica nel Corso di Laurea per Educatore della prima infanzia. Le opinioni degli studenti
No full textIl contributo cerca di giustificare la validità di una didattica universitaria basata su una concezione modulare degli insegnamenti a partire da un'esperienza svolta presso il corso di laurea per Educatori della prima infanzia dell'Università di Padova. L'esperienza ha coinvolto tre docenti del secondo e terzo anno di studi che hanno progettato congiuntamente i loro insegnamenti con buon apprezzamento da parte degli studenti riguardo l'unitarità di metodologie e strumenti di conduzione e valutazione dei processi formativi attivati
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