2,395 research outputs found
TEM as an Important Tool to Study Aquatic Microorganisms and their Relationships with Ecological Processes
Microorganisms are critically important for ecological processes in aquatic environments. Bacteria and viruses are key components of the microbial loop and are central for biogeochemical cycles in aquatic ecosystems. Our group has been using transmission electron microscopy (TEM) to study aquatic microorganisms in both natural tropical ecosystems and cultures. In this review, we highlight structural aspects of freshwater bacteria, based on TEM findings that have provided insights into the functional capabilities of these cells in aquatic tropical ecosystems. First, we focus on TEM applied to the study of the ultrastructural diversity and morphological alterations of bacteria in response to environmental stress. Second, we address the relationship between viruses and bacteria in freshwater ecosystems. Third, we demonstrate by TEM that outer membrane vesicles (OMVs), structures associated with cell secretion and cell communication, are released by aquatic bacteria into natural ecosystems and cultures. Thus, TEM has proven to be a powerful technique to study aquatic microorganisms, contributing to the understanding of ecological processes, including regulation of bacterial populations, during different environmental conditions
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Aplicação de Análise e Modelagem Multidimensional para o Monitoramento de ResÃduos Sólidos Industriais
Global monopole as a generator of a bulk-brane structure in Brans-Dicke bulk gravity
We investigate a braneworld model generated by a global monopole in the
context of Brans-Dicke gravity. After solving the dynamical equations we found
a model capable to alleviate the so-called hierarchy problem. The obtained
framework is described by a hybrid compactification scheme endowed with a
seven-dimensional spacetime, in which the brane has four non-compact dimensions
and two curled extra dimensions. The relevant aspects of the resulting model
are studied and the requirements to avoid the well known seesaw-like behavior
are discussed. We show that under certain conditions it is possible to
circumvent such a pathological behavior that characterizes most of the models
that exhibit hybrid compactification. Lastly, we deepen our analysis by
considering possible extensions of this model to a setup with multiple branes
and orbifold-like extra dimension. For this, we compute the consistency
conditions to be obeyed by this more general configuration as predicted by the
braneworld sum rules formalism. This study indicates the possibility of
exclusively positive brane tensions in the model.Comment: 10 pages, 1 figure. Improved version with more discussion added to
the Introduction, section II and conclusion. A new plot was added as well as
new references. Matches version accepted in EPJ
Braneworld gravity within non-conservative gravitational theory
We investigate the braneworld gravity starting from the non-conservative
gravitational field equations in a five-dimensional bulk. The approach is based
on the Gauss-Codazzi formalism along with the study of the braneworld
consistency conditions. The effective gravitational equations on the brane are
obtained and the constraint leading to a brane energy-momentum conservation is
analyzed.Comment: 7 page
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