108 research outputs found
Efeito da densidade de Brachiaria ruziziensis na germinação carpogênica de escleródios em área naturalmente infestada por Sclerotinia sclerotiorum.
Entre as dificuldades para o controle do mofo branco, está a sobrevivência de escleródios do patógeno Sclerotinia sclerotiorum no solo por vários anos, que dificilmente são afetados por fungicidas ou por várias práticas culturais. Estes escleródios, porém, podem ser mortos por esgotamento após germinação ou parasitismo. Em um experimento realizado em Jataí, GO, avaliou-se a germinação de escleródios e posterior produção de apotécios, em tratamentos sem cobertura do solo, e sob cultivo de Brachiaria ruziziensis estabelecida em março de 2008, com 150, 300, 450 ou 600 pontos de valor cultural (PVC)
On the phase-space structure of galaxy clusters from cosmological simulations
Cosmological N-body simulations represent an excellent tool to study the formation and evolution of dark matter (DM) haloes and the mechanisms that have originated the universal profile at the largest mass scales in the Universe. In particular, the combination of the velocity dispersion \u3c3v with the density p can be used to define the pseudo-entropy S(r) = \u3c32 v /p 2/3, whose profile is well described by a simple power law S 1e r \u3b1. We analyse a set of cosmological hydrodynamical re-simulations of massive galaxy clusters and study the pseudo-entropy profiles as traced by different collisionless components in simulated galaxy clusters: DM, stars, and substructures. We analyse four sets of simulations, exploring different resolution and physics (N-body and full hydrodynamical simulations) to investigate convergence and the impact of baryons. We find that baryons significantly affect the inner region of pseudo-entropy profiles as traced by substructures, while DM particles profiles are characterized by an almost universal behaviour, thus suggesting that the level of pseudo-entropy could represent a potential low-scatter mass-proxy. We compare observed and simulated pseudo-entropy profiles and find good agreement in both normalization and slope. We demonstrate, however, that the method used to derive observed pseudo-entropy profiles could introduce biases and underestimate the impact of mergers. Finally, we investigate the pseudo-entropy traced by the stars focusing our interest in the dynamical distinction between intracluster light and the stars bound to the brightest cluster galaxy: The combination of these two pseudo-entropy profiles is well described by a single power law out to almost the entire cluster virial radius
Thermodynamic evolution of the galaxy cluster IDCS J1426.5+3508
We present resolved thermodynamic profiles out to 500 kpc, about ,
of the galaxy cluster IDCS J1426.5+3508 with 40 kpc resolution. Thanks
to the combination of Sunyaev-Zel'dovich and X-ray datasets, IDCS J1426.5+3508
becomes the most distant cluster with resolved thermodynamic profiles. These
are derived assuming a non-parametric pressure profile and a very flexible
model for the electron density profile. The shape of the pressure profile is
flatter than the universal pressure profile. The IDCS J1426.5+3508 temperature
profile is increasing radially out to 500 kpc. To identify the possible future
evolution of IDCS J1426.5+3508 , we compared it with its local descendants that
numerical simulations show to be dex more massive. We found no
evolution at 30 kpc, indicating a fine tuning between cooling and heating at
small radii. At kpc, our observations show that entropy and heat
must be deposited with little net gas transfer, while at 500 kpc the gas need
to be replaced by a large amount of cold, lower entropy gas, consistent with
theoretical expectation of a filamentary gas stream, which brings low entropy
gas to 500 kpc and energy at even smaller radii. At kpc the
polytropic index takes a low value, which indicates the presence of a large
amount of non-thermal pressure. Our work also introduces a new definition of
the evolutionary rate, which uses unscaled radii, unscaled thermodynamic
quantities, and different masses at different redshifts to compare ancestors
and descendants. It has the advantage of separating cluster evolution,
dependence on mass, pseudo-evolution and returns a number with unique
interpretation, unlike other definitions used in literature.Comment: MNRAS, in press. In v2 we only corrected author affiliations and
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Controle de Sclerotinia sclerotiorum com o manejo de Brachiaria ruziziensis e aplicação de Trichoderma harzianum.
Este estudo teve o objetivo de verificar uma possível interação entre controle biológico e palhada, para redução da densidade de inóculo de Sclerotinia sclerotiorum.bitstream/CNPAF-2009-09/28171/1/circ_81.pd
Populações de Pratylenchus brachyurus em raízes de soja cultivada após adensamento de Brachiaria ruziziensis.
A palhada de Brachiaria ruziziensis tem sido empregada para o manejo do mofo branco (Sclerotinia sclerotiorum). Contudo, esta forrageira é hospedeira de Praylenchus brachyurus, e não há informações em campo sobre este patossistema forrageira x nematóide. Para verificar esta relação, foi conduzido um experimento em Jataí, GO, na safra 2008/2009
Euclid preparation. XXIV. Calibration of the halo mass function in Λ(ν)CDM cosmologies
Euclid’s photometric galaxy cluster survey has the potential to be a very competitive cosmological probe. The main cosmological probe with observations of clusters is their number count, within which the halo mass function (HMF) is a key theoretical quantity. We present a new calibration of the analytic HMF, at the level of accuracy and precision required for the uncertainty in this quantity to be subdominant with respect to other sources of uncertainty in recovering cosmological parameters from Euclid cluster counts. Our model is calibrated against a suite of N-body simulations using a Bayesian approach taking into account systematic errors arising from numerical effects in the simulation. First, we test the convergence of HMF predictions from different N-body codes, by using initial conditions generated with different orders of Lagrangian Perturbation theory, and adopting different simulation box sizes and mass resolution. Then, we quantify the effect of using different halo finder algorithms, and how the resulting differences propagate to the cosmological constraints. In order to trace the violation of universality in the HMF, we also analyse simulations based on initial conditions characterised by scale-free power spectra with different spectral indexes, assuming both Einstein–de Sitter and standard ΛCDM expansion histories. Based on these results, we construct a fitting function for the HMF that we demonstrate to be sub-percent accurate in reproducing results from 9 different variants of the ΛCDM model including massive neutrinos cosmologies. The calibration systematic uncertainty is largely sub-dominant with respect to the expected precision of future mass–observation relations; with the only notable exception of the effect due to the halo finder, that could lead to biased cosmological inference
Euclid preparation TBD. The effect of baryons on the Halo Mass Function
The Euclid photometric survey of galaxy clusters stands as a powerful cosmological tool, with the capacity to significantly propel our understanding of the Universe. Despite being sub-dominant to dark matter and dark energy, the baryonic component in our Universe holds substantial influence over the structure and mass of galaxy clusters. This paper presents a novel model to precisely quantify the impact of baryons on galaxy cluster virial halo masses, using the baryon fraction within a cluster as proxy for their effect. Constructed on the premise of quasi-adiabaticity, the model includes two parameters calibrated using non-radiative cosmological hydrodynamical simulations and a single large-scale simulation from the Magneticum set, which includes the physical processes driving galaxy formation. As a main result of our analysis, we demonstrate that this model delivers a remarkable one percent relative accuracy in determining the virial dark matter-only equivalent mass of galaxy clusters, starting from the corresponding total cluster mass and baryon fraction measured in hydrodynamical simulations. Furthermore, we demonstrate that this result is robust against changes in cosmological parameters and against varying the numerical implementation of the sub-resolution physical processes included in the simulations. Our work substantiates previous claims about the impact of baryons on cluster cosmology studies. In particular, we show how neglecting these effects would lead to biased cosmological constraints for a Euclid-like cluster abundance analysis. Importantly, we demonstrate that uncertainties associated with our model, arising from baryonic corrections to cluster masses, are sub-dominant when compared to the precision with which mass-observable relations will be calibrated using Euclid, as well as our current understanding of the baryon fraction within galaxy clusters
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