100,637 research outputs found
Trichogrammes contre la mineuse de la tomate, à la recherche du meilleur : 64 souches testées contre Tuta absoluta dans le cadre du programme CasDar TutaPI
No full textIl y a deux mois, Phytoma évoquait la protection des cultures de tomate contre la mineuse de la tomate Tuta absoluta. Il en ressortait que, pour réussir cette protection, il fallait intégrer plusieurs moyens dont des auxiliaires parasitoïdes (Tabone et al., 2012). L’article citait le projet CASDAR « T utaPI » financé par le Ministère de l’Agriculture (2011-2013). Ce projet a pour objectif de trouver une nouvelle méthode de protection biologique efficace à des coûts raisonnables (Tabone et al., 2010b ; Tabone 2011 ; Tabone et al., 2011). Aujourd’hui, nous présentons ses premiers résultats. Ils sont prometteurs
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
Vertical CO surfaces as a probe for protoplanetary disk mass and carbon depletion
No full textContext. As the sample of mid-inclination disks with measured CO emission surfaces continues to grow, a fundamental question that has gone unanswered is how these vertical profiles are connected to their host properties.Aims. This work is aimed at relating the vertical extent of protoplanetary disks as traced by 12CO 2-1 to key stellar and physical parameters. We have benchmarked our results with ALMA observations of CO emission from nineteen disks to produce a result that is applicable to observational analyses.Methods. We produced a grid of disk models using the physical-chemical code DALI for a template T Tauri and Herbig star. Our models use an iterative solver to calculate the hydrostatic equilibrium equations and determine a physically motivated density structure. Key stellar and disk parameters, such as the stellar luminosity and temperature, total disk mass and carbon abundance are varied to determine their effect on the CO emitting surface. Each vertical profile is fitted by an exponentially tapered power law and characterized by the z/r value that represents the structure inwards of 80% of the tapering radius.Results. The CO emission surface location is primarily determined by the disk mass (Md) and the level of volatile carbon depletion. T Tauri and Herbig systems show different vertical profiles, with disks around T Tauri stars shown to be be more vertically extended. We derived a z/r-Md relationship (which has a degeneracy) for each stellar type, with the volatile carbon abundance. To reconcile the total disk mass estimates from the characteristic z/r and the values obtained from the dust continuum analysis, we find that a volatile carbon depletion of 10-100 (with respect to the interstellar medium) is needed for the majority of our sources. Our carbon depletion values are in agreement with previous literature estimates, highlighting the potential of this method to rapidly calculate key disk parameters
Constraining turbulence in protoplanetary discs using the gap contrast: an application to the DSHARP sample
No full textConstraining the strength of gas turbulence in protoplanetary discs is an
open problem that has relevant implications for the physics of gas accretion
and planet formation. In this work, we gauge the amount of turbulence in 6 of
the discs observed in the DSHARP programme by indirectly measuring the vertical
distribution of their dust component. We employ the differences in the gap
contrasts observed along the major and the minor axes due to projection
effects, and build a radiative transfer model to reproduce these features for
different values of the dust scale heights. We find that (a) the scale heights
that yield a better agreement with data are generally low ( AU at a
radial distance of AU), and in almost all cases we are only able to place
upper limits on their exact values; these conclusions imply (assuming an
average Stokes number of ) low turbulence levels of
; (b) for the 9 other systems we
considered out of the DSHARP sample, our method yields no significant
constraints on the disc vertical structure; we conclude that this is because
these discs have either a low inclination or gaps that are not deep enough.
Based on our analysis we provide an empirical criterion to assess whether a
given disc is suitable to measure the vertical scale height.Comment: Accepted for publication in MNRAS. 13 pages + appendix, 12 figure
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
Formare i futuri insegnanti a progettare la didattica integrando le tecnologie
No full textQuesto contributo presenta una proposta formativa volta a integrare operativamente le tecnologie nella formazione dei futuri insegnanti di scuola dell’infanzia e di scuola primaria. In particolare, il contributo propone uno strumento per la progettazione didattica, che operazionalizza specifici apporti teorici – PCK (Shulman, 1986), TPACK (Mishra & Koehler, 2006), LAT-Learning Activity Types (Harris & Hofer, 2009), multimodality (Cope & Kalantzis, 2000) – illustrandone e giustificandone la struttura. Tale strumento sarà utilizzato in un progetto di ricerca, verificando se consenta ai futuri insegnanti di sviluppare una procedura integrata di progettazione didattica, dinamica e adattabile ai domini di conoscenza che incontreranno nel loro percorso formativo
Foqra u Għonja
No full textĠabra ta’ poeżiji u proża li tinkludi: Il-Qassis ta’ K. Vassallo – Lil Binti ta’ Ġużè Chetcuti – Il-Milied ta’ San Franġisk ta’ P. Pawl Tabone – L-Ibleh taż-Żenqa t-Twila ta’ A. Cremona – L-Annunzjazzjoni ta’ Val. V. Barbara – Fi Twelid Sidna ta’ Val. V. Barbara – Foqra u Għonja ta’ R. M. B.N/
Development and assessment of simple PCR markers for SNP genotyping in barley
No full textSimple molecular marker assays underpin routine plant breeding and research activities in many laboratories worldwide. With the rapid growth of single nucleotide polymorphism (SNP) resources for many important crop plants, the availability of routine, low-tech marker assays for genotyping SNPs is of increased importance. In this study, we demonstrate that temperature-switch PCR (TSP) supports the rapid development of robust, allele-specific PCR markers for codominant SNP genotyping on agarose gel. A total of 87 TSP markers for assessing gene diversity in barley were developed and used to investigate the efficacy for marker development, assay reliably and genotyping accuracy. The TSP markers described provide good coverage of the barley genome, are simple to use, easy to interpret and score, and are amenable to assay automation. They provide a resource of informative SNP markers for assessing genetic relationships among individuals, populations and gene pools of cultivated barley (Hordeum vulgare L.) and its wild relative H. spontaneum K. Koch. TSP markers provide opportunities to use available SNP resources for marker-assisted breeding and plant genetic research, and to generate information that can be integrated with SNP data from different sources and studies. TSP markers are expected to provide similar advantages for any animal or plant species.Matthew J. Hayden, T. Tabone and D.E. Mathe
Handwritten biographical information on Paulina T. McClung Merritt
No full textA handwritten biography of Paulina T. McClung Merritt by an unknown author, 1892.
Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
No full textIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
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