18,834 research outputs found
Metabolism And The Rise Of Fungus Cultivation By Ants
Most ant colonies are comprised of workers that cooperate to harvest resources and feed developing larvae. Around 50 million years ago (MYA), ants of the attine lineage adopted an alternative strategy, harvesting resources used as compost to produce fungal gardens. While fungus cultivation is considered a major breakthrough in ant evolution, the associated ecological consequences remain poorly understood. Here, we compare the energetics of attine colony-farms and ancestral hunter-gatherer colonies using metabolic scaling principles within a phylogenetic context. We find two major energetic transitions. First, the earliest lower-attine farmers transitioned to lower mass-specific metabolic rates while shifting significant fractions of biomass from ant tissue to fungus gardens. Second, a transition 20 MYA to specialized cultivars in the higher-attine clade was associated with increased colony metabolism (without changes in garden fungal content) and with metabolic scaling nearly identical to hypometry observed in hunter-gatherer ants, although only the hunter-gatherer slope was distinguishable from isometry. Based on these evolutionary transitions, we propose that shifting living-tissue storage from ants to fungal mutualists provided energetic storage advantages contributing to attine diversification and outline critical assumptions that, when tested, will help link metabolism, farming efficiency, and colony fitness.Integrative Biolog
Comunicação corporativa na era da televisão digital interativa.
Este artigo aborda a pesquisa que está sendo conduzida na empresa sobre o desenvolvimento de tecnologias e metodologias de produção de conteúdo para a TV digital, que visa criar um canal para divulgação científica e transferência de tecnologia cujo foco é amparado em um novo paradigma baseado no potencial das novas mídias para a democratização e a inclusão social de produtores rurais. Os estudos incluem o desenvolvimento de um ambiente interativo e a produção de conteúdos-piloto audiovisuais, envolvendo a participação da comunidade, tanto durante o processo construtivo quanto na validação das metodologias criadas, num processo interativo mediado pelas tecnologias multimídia
Caracterização morfológica e molecular de híbridos interespecíficos de Arachis resistentes a pragas.
ISO-3D Applications of 3-Dimensional Electromagnetic Induction by Sources in the Oceans: a MAST-3 Project. Final report of ISO-3D Working Group.
JWST observations of stellar occultations by solar system bodies and rings
In this paper we investigate the opportunities provided by the James Webb
Space Telescope (JWST) for significant scientific advances in the study of
solar system bodies and rings using stellar occultations. The strengths and
weaknesses of the stellar occultation technique are evaluated in light of
JWST's unique capabilities. We identify several possible JWST occultation
events by minor bodies and rings, and evaluate their potential scientific
value. These predictions depend critically on accurate a priori knowledge of
the orbit of JWST near the Sun-Earth Lagrange-point 2 (L2). We also explore the
possibility of serendipitous stellar occultations by very small minor bodies as
a by-product of other JWST observing programs. Finally, to optimize the
potential scientific return of stellar occultation observations, we identify
several characteristics of JWST's orbit and instrumentation that should be
taken into account during JWST's development.Comment: This paper is one of a series for a special issue on Solar System
observations with JWST in PASP. Accepted 2-Oct-2015. Preprint 30 pages, 5
tables, 8 figure
Nonlinear viscosity and velocity distribution function in a simple longitudinal flow
A compressible flow characterized by a velocity field is
analyzed by means of the Boltzmann equation and the Bhatnagar-Gross-Krook
kinetic model. The sign of the control parameter (the longitudinal deformation
rate ) distinguishes between an expansion () and a condensation ()
phenomenon. The temperature is a decreasing function of time in the former
case, while it is an increasing function in the latter. The non-Newtonian
behavior of the gas is described by a dimensionless nonlinear viscosity
, that depends on the dimensionless longitudinal rate . The
Chapman-Enskog expansion of in powers of is seen to be only
asymptotic (except in the case of Maxwell molecules). The velocity distribution
function is also studied. At any value of , it exhibits an algebraic
high-velocity tail that is responsible for the divergence of velocity moments.
For sufficiently negative , moments of degree four and higher may diverge,
while for positive the divergence occurs in moments of degree equal to or
larger than eight.Comment: 18 pages (Revtex), including 5 figures (eps). Analysis of the heat
flux plus other minor changes added. Revised version accepted for publication
in PR
Plasmons in layered structures including graphene
We investigate the optical properties of layered structures with graphene at
the interface for arbitrary linear polarization at finite temperature including
full retardation by working in the Weyl gauge. As a special case, we obtain the
full response and the related dielectric function of a layered structure with
two interfaces. We apply our results to discuss the longitudinal plasmon
spectrum of several single and double layer devices such as systems with finite
and zero electronic densities. We further show that a nonhomogeneous dielectric
background can shift the relative weight of the in-phase and out-of-phase mode
and discuss how the plasmonic mode of the upper layer can be tuned into an
acoustic mode with specific sound velocity.Comment: 18 pages, 6 figure
Análise exploratória dos atributos químicos em solos do cerrado sob diferentes manejo e uso.
FertBio 2014
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