2,652 research outputs found
Essential plasticity and redundancy of metabolism unveiled by synthetic lethality analysis
We unravel how functional plasticity and redundancy are essential mechanisms
underlying the ability to survive of metabolic networks. We perform an
exhaustive computational screening of synthetic lethal reaction pairs in
Escherichia coli in a minimal medium and we find that synthetic lethal pairs
divide in two different groups depending on whether the synthetic lethal
interaction works as a backup or as a parallel use mechanism, the first
corresponding to essential plasticity and the second to essential redundancy.
In E. coli, the analysis of pathways entanglement through essential redundancy
supports the view that synthetic lethality affects preferentially a single
function or pathway. In contrast, essential plasticity, the dominant class,
tends to be inter-pathway but strongly localized and unveils Cell Envelope
Biosynthesis as an essential backup for Membrane Lipid Metabolism. When
comparing E. coli and Mycoplasma pneumoniae, we find that the metabolic
networks of the two organisms exhibit a large difference in the relative
importance of plasticity and redundancy which is consistent with the conjecture
that plasticity is a sophisticated mechanism that requires a complex
organization. Finally, coessential reaction pairs are explored in different
environmental conditions to uncover the interplay between the two mechanisms.
We find that synthetic lethal interactions and their classification in
plasticity and redundancy are basically insensitive to medium composition, and
are highly conserved even when the environment is enriched with nonessential
compounds or overconstrained to decrease maximum biomass formation.Comment: 22 pages, 4 figure
Assessing the significance of knockout cascades in metabolic networks
Complex networks have been shown to be robust against random structural
perturbations, but vulnerable against targeted attacks. Robustness analysis
usually simulates the removal of individual or sets of nodes, followed by the
assessment of the inflicted damage. For complex metabolic networks, it has been
suggested that evolutionary pressure may favor robustness against reaction
removal. However, the removal of a reaction and its impact on the network may
as well be interpreted as selective regulation of pathway activities,
suggesting a tradeoff between the efficiency of regulation and vulnerability.
Here, we employ a cascading failure algorithm to simulate the removal of single
and pairs of reactions from the metabolic networks of two organisms, and
estimate the significance of the results using two different null models:
degree preserving and mass-balanced randomization. Our analysis suggests that
evolutionary pressure promotes larger cascades of non-viable reactions, and
thus favors the ability of efficient metabolic regulation at the expense of
robustness
Flame filtering and perimeter localization of wildfires using aerial thermal imagery
Airborne thermal infrared (TIR) imaging systems are being increasingly used for wild fire tactical monitoring since they show important advantages over spaceborne platforms and visible sensors while becoming much more affordable and much lighter than multispectral cameras. However, the analysis of aerial TIR images entails a number of difficulties which have thus far prevented monitoring tasks from being totally automated. One of these issues that needs to be addressed is the appearance of flame projections during the geo-correction of off-nadir images. Filtering these flames is essential in order to accurately estimate the geographical location of the fuel burning interface. Therefore, we present a methodology which allows the automatic localisation of the active fire contour free of flame projections. The actively burning area is detected in TIR georeferenced images through a combination of intensity thresholding techniques, morphological processing and active contours. Subsequently, flame projections are filtered out by the temporal frequency analysis of the appropriate contour descriptors. The proposed algorithm was tested on footages acquired during three large-scale field experimental burns. Results suggest this methodology may be suitable to automatise the acquisition of quantitative data about the fire evolution. As future work, a revision of the low-pass filter implemented for the temporal analysis (currently a median filter) was recommended. The availability of up-to-date information about the fire state would improve situational awareness during an emergency response and may be used to calibrate data-driven simulators capable of emitting short-term accurate forecasts of the subsequent fire evolution.Postprint (author's final draft
Antropologías médicas en Europa
Si bien el médico Ludwig Finke propuso en 1795 el término Anthropographie para caracterizar lo que hoy llamamos etnografía, y que en aquel momento utilizó para escribir topografías médicas que proliferaron muy especialmente en Europa del sur, las relaciones entre la medicina europea y la antropología han sido ya revisadas críticamente. Hay constancia de una enorme producción etnográfica por parte de los médicos europeos desde el siglo XVIII hasta la constitución de la antropología médica como campo de la antropología profesional en los años sesenta en Norteamérica. Asimismo, los médicos formaron parte integrante del desarrollo de la antropología como disciplina autónoma desde el siglo XVIII y están presentes en los elencos de todas las sociedades de antropología fundadas en el siglo XIX
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