94 research outputs found
Osmo- and thermo-adaptation in hyperthermophilic Archaea: identification of compatible solutes accumulation profiles, and biosynthetic routes in Archaeoglobus spp.
Dissertation presented to obtain the Ph.D degree in BiochemistryHyperthermophilic organisms have optimum growth temperatures above 80°C and belong to genera that are placed near the root of the Tree of Life, in short phylogenetic branches within the domains Bacteria or Archaea. Although hyperthermophiles have been isolated from a variety of hot environments, most species originate from marine geothermal areas, hence they are slightly halophilic. The accumulation of low-molecular mass organic solutes, i. e., compatible solutes, is one of the most common strategies developed by cells to cope with fluctuations of the salinity of the medium. Interestingly, in marine hyperthermophiles, compatible solute accumulation occurs not only in response to an increase in the external salt concentration, but also in response to supraoptimal growth temperatures. Moreover, microorganisms adapted to grow optimally at elevated temperatures tend to use negatively charged solutes that are not present or rarely encountered in mesophilic organisms.(...
3D solar coronal loop reconstructions with machine learning
The magnetic field plays an essential role in the initiation and evolution of
different solar phenomena in the corona. The structure and evolution of the 3D
coronal magnetic field are still not very well known. A way to get the 3D
structure of the coronal magnetic field is by performing magnetic field
extrapolations from the photosphere to the corona. In previous work, it was
shown that by prescribing the 3D reconstructed loops' geometry, the magnetic
field extrapolation finds a solution with a better agreement between the
modeled field and the reconstructed loops. Also, it improves the quality of the
field extrapolation. Stereoscopy represents the classical method for performing
3D coronal loop reconstruction. It uses at least two view directions. When only
one vantage point of the coronal loops is available, other 3D reconstruction
methods must be applied. Within this work, we present a method for the 3D loop
reconstruction based on machine learning. Our purpose for developing this
method is to use as many observed coronal loops in space and time for the
modeling of the coronal magnetic field. Our results show that we can build
machine learning models that can retrieve 3D loops based only on their
projection information. In the end, the neural network model will be able to
use only 2D information of the coronal loops, identified, traced and extracted
from the EUV images, for the calculation of their 3D geometry.Comment: 7 Pages, 3 Figures, Accepted for publication on Astrophysical Journal
Letter
Geomorphometric characterization of pockmarks by using a GIS-based semi-automated toolbox
Pockmarks are seabed depressions developed by fluid flow processes that can be found in vast numbers in many marine and lacustrine environments. Manual mapping of these features based on geophysical data is, however, extremely time-consuming and subjective. Here, we present results from a semi-automated mapping toolbox developed to allow more efficient and objective mapping of pockmarks. This ArcGIS-based toolbox recognizes, spatially delineates, and morphometrically describes pockmarks. Since it was first developed, the toolbox has helped to map and characterize several thousands of pockmarks on the UK continental shelf, especially within the central North Sea. This paper presents the latest developments in the functionality of the toolbox and its adaptability for application to other geographic areas (Barents Sea, Norway, and Malin Deep, Ireland) with varied pockmark and seabed morphologies, and in different geological settings. The morphometric characterization of vast numbers of pockmarks allows an unprecedented statistical analysis of their morphology. The outputs from the toolbox provide an objective, quantitative baseline for combining this information with the geological and oceanographical knowledge of individual areas, which can provide further insights into the processes responsible for their development and their influence on local seabed conditions and habitat
A geomorphological interpretation of multibeam data from the nearshore area between Belfast Lough and Cushendun, Northern Ireland
This report describes a geomorphological interpretation of a multibeam echosounder dataset acquired offshore Northern Ireland, between Belfast Lough and the town of Cushendun. It is part of a Department of Enterprise, Trade and Investment (DETI) sponsored study aimed at gaining a better understanding of the distribution and thickness of subsurface salt layers expected to be present offshore Northern Ireland with the aim of assessing their potential for construction of caverns for storage of natural gas. Part of the study involved the acquisition of a high resolution 2D seismic dataset designed to image potential Upper Permian and Middle Triassic salt layers. The multibeam dataset was acquired in conjunction with the 2D seismic dataset and, despite this being a lower priority deliverable, good coverage was achieved due to the high density of seismic tracks and relatively deep water depth in this nearshore location.
The multibeam data provides accurate measurements of the water depth in the study area and valuable information about the morphology and composition of the sea bed in the area. In the southern part of the survey area almost 100% coverage was achieved because of the close line spacing whereas in the northern part there are gaps between the multibeam data swaths. Although not specifically designed to acquire data to Admiralty Chart standard nonetheless the survey has made a valuable contribution to the knowledge of the seabed in this area which has applications in navigation, fishing, marine conservation and planning.
The multibeam dataset, comprising bathymetric and backscatter information, was interpreted using ArcMap 9.3 GIS software. This allowed the use of appropriate surface analysis tools, such as slope and shaded-relief, to enhance the geomorphological interpretation. It also allowed the integration of the multibeam with other datasets held by the British Geological Survey (BGS). The multibeam dataset reveals the complex morphology of the surveyed seabed, which has been shaped by a development marked by tectonic, igneous, glacial and marine sedimentary events.
The survey area contains parts of two renewable energy ‘resource zones’ identified in the Strategic Environmental Assessment report for the Northern Ireland Offshore Renewable Energy Strategic Action Plan. Tidal Resource Zone 2 (Rathlin Island and Torr Head) extends into the northern edge of the survey area and Tidal Resource Zone 3 (Maiden Islands) lies wholly within the survey area. Initial data interpretation presented in this report can be used to characterise the seabed but there is potential, with further ground-truthing by biological surveys, seabed sampling and shallow drilling, to produce maps of the seabed physical and biological habitats. Such maps would be invaluable as input into the planning and design of any future tidal energy infrastructure and as baseline data against which to measure the impact of this infrastructure
Semi-automated mapping and characterisation of coral reef mounds : Mingulay Reef proof of concept
This report describes a new approach to map coral reef mounds. The study area used for this mapping exercise is located approximately 13 km east of the island of Mingulay (56°50′N, 7°30′W) and is known as the Mingulay Reef Complex. The approach adopted consists on the combination of the Bathymetric Position Index tool for habitat mapping and the semi-automated mapping method developed initially to map pockmarks at seabed. During this exercise, 354 coral reefs were successfully mapped. The results of this test-of-concept supported the creation of a customised tool for semi-automated mapping of cold-water coral reefs, to derive coral mound attributes from multibeam datasets without interpreter bias
3D seismic evidence of internal structure within Tampen Slide deposits on the North Sea Fan : are chaotic deposits that chaotic?
The seismic character of slide deposits is typically described as structureless or chaotic. However, 3D seismic data from the northern flank of the North Sea Fan reveal recognizable internal, penetrative structures within the Tampen Slide deposits. The study of its seismic attributes allowed an integrated characterization of the slide deposits and has shown distinctive acoustic fabrics, both at the top and base of the slide deposit, which are interpreted to be the expression of internal deformation structures. Based on their geometry, four main seismic fabric types have been defined: anastomosing, curvilinear, rectilinear and wispy. The spatial distribution of the fabric was mainly controlled by a topographic high present on the sea-bed at the time of the gravitational collapse, which influenced the transport of material. Areas of distinct fabrics are thought to reflect different flow behaviour during the latest stages of the mass movement and could be considered kinematic indicators. The results give new insights into the transport and deformation processes of submarine mass movements and highlight the potential of detailed analysis of 3D seismic data
Total electron content PCA-NN model for middle latitudes
A regression-based model was previously developed to forecast the total
electron content (TEC) at middle latitudes. We present a more sophisticated
model using neural networks (NN) instead of linear regression. This regional
model prototype simulates and forecasts TEC variations in relation to space
weather conditions. The development of a prototype consisted of the selection
of the best set of predictors, NN architecture and the length of the input
series. Tests made using the data from December 2014 to June 2018 show that the
PCA-NN model based on a simple feed-forward NN with a very limited number (up
to 6) of space weather predictors performs better than the PCA-MRM model that
uses up to 27 space weather predictors. The prototype is developed on a TEC
series obtained from a GNSS receiver at Lisbon airport and tested on TEC series
from three other locations at middle altitudes of the Eastern North Atlantic.
Conclusions on the dependence of the forecast quality on longitude and latitude
are made.Comment: arXiv admin note: text overlap with arXiv:2201.0347
Cartografia morfo-estrutural da área da falha Marquês de Pombal : utilização de imagens de sonar lateral de alta resolução (TOBI) e de perfis sÃsmicos de reflexão para cartogarfia de áreas submarinas
O estudo mono-estrutural detalhado da área da Falha Marquês de Pombal (>3300 km2 agora apresentado, baseou-se na interpretação de: linhas sÃsmica mu1ti-canal, imagens de sonar lateral de alta resolução (TOBI) e da análise de dados batimétricos. Resultaram deste estudo: i) a quantificação parcial da deformação ao longo Falha Marquês de Pombal, ii) modelo digital de terreno da área estudada, iii) mapas de declive e outros produtos de analise espacial iv) mapas de pormenor dos movimentos de massa existentes na área v) mapa mono-estrutural da área da Falha Marquês de Pombal, à escala 1:250.000. Este trabalho mostra que a morfologia da área de estudo está intimamente associada à sua compartimentação estrutural e à s diferenças na evolução tectónica do Miocénico Médio até ao Presente. Dobras e falhas inversas afectando unidades do Quaternário assinalam actividade tectónica actual. Canais e escorregamentos submarinos são frequentes em toda a área. Na vertente associada a Falha Marquês de Pombal foi identificado um grande escorregamento complexo (com uma área total de ~110 km2). Abstract: Morpho-Structural Mapping of the Marquês de Pombal Fault Area (off SW Portugal). This thesis is a morpho-structural study of the Marques de Pombal Fault (MPF) and surrounding area (>3300 km2), based on the study and interpretation of multi channel seismic reflection profiles, high-resolution side-scan sonar image (TOBI) and bathymetry data. The outcomes of the study are: i) the partial quantification of the deformation along the MPF, ii) digital terrain models of the study area, iii) slope maps and results of other surface analysis, iv) maps detailing the mass movements of the study area, v) a morpho-structural map of the MPF at a scale of 1:250 000. The analysis of the data shows that the morphological differentiations of the study area are intimately associated with its structural compartmentalization and the tectonic evolution from the Middle Miocene to present time. Folding and reverse faulting of the Quaternary units along this structure indicate present-day tectonic activity. Gully-incised slope failures and submarine landslides are common features. One major complex submarine landslide, disrupting a total area of ~.110 km2, was identified at the Marques de Pombal thrust front
Morphological properties of slender Ca II H fibrils observed by Sunrise II
R. Gafeira et. al.©2017 The American Astronomical Society. All rights reserved. We use seeing-free high spatial resolution Ca ii H data obtained by the Sunrise observatory to determine properties of slender fibrils in the lower solar chromosphere. In this work we use intensity images taken with the SuFI instrument in the Ca ii H line during the second scientific flight of the Sunrise observatory to identify and track elongated bright structures. After identification, we analyze theses structures to extract their morphological properties. We identify 598 slender Ca ii H fibrils (SCFs) with an average width of around 180 km, length between 500 and 4000 km, average lifetime of ≈400 s, and average curvature of 0.002 arcsec−1. The maximum lifetime of the SCFs within our time series of 57 minutes is ≈2000 s. We discuss similarities and differences of the SCFs with other small-scale, chromospheric structures such as spicules of type I and II, or Ca ii K fibrils.The German contribution to Sunrise and its reflight was funded by the Max Planck Foundation, the Strategic Innovations Fund of the President of the Max Planck Society (MPG), the Deutsche Zentrum für Luft- und Raumfahrt (DLR), and private donations by supporting members of the Max Planck Society, which is gratefully acknowledged. The Spanish contribution was funded by the Ministerio de EconomÃa y Competitividad under Projects ESP2013-47349-C6 and ESP2014-56169-C6, partially using European FEDER funds. The HAO contribution was partly funded through NASA grant number NNX13AE95G. This work was partly supported by the BK21 plus program through the National Research Foundation (NRF) funded by the Ministry of Education of Korea. S.J. receives support from the Research Council of Norway.Peer reviewe
- …