369 research outputs found
New approaches to the study of Antarctic lithobiontic microorganisms and their inorganic traces, and their application in the detection of life in Martian rocks
Microbial life in the harsh conditions of Antarctica’s cold desert may be considered an analogue of potential life on early Mars. In order to explore the development and survival of this epilithic and endolithic form of microbial life, our most sophisticated, state-ofthe- art visualization technologies have to be used to their full potential. The study of any ecosystem requires a knowledge of its components and the processes that take place within it. If we are to understand the structure and function of each component of the microecosystems that inhabit lithic substrates, we need to be able to quantify and identify the microorganisms present in each lithobiontic ecological niche and to accurately characterize the mineralogical features of these hidden microhabitats. Once we have established the techniques that will allow us to observe and identify these microorganisms and mineral substrates in situ, and have confirmed the presence of water, the following questions can be addressed: How are the microorganisms organized in the fissures or cavities? Which microorganisms are present and how many are there? Additional questions that logically follow include: What are the existing water relationships in the microhabitat and what effects do the microorganisms have on the mineral composition? Mechanical and chemical changes in minerals and mineralization of microbial cells can give rise to physical and/or chemical traces (biomarkers) and to microbial fossil formation. In this report, we describe the detection of chains of magnetite within the Martian meteorite ALH84001, as an example of the potential use of SEMBSE in the search for plausible traces of life on early Mars
Construction of Chemoenzymatic Linear Cascades for the Synthesis of Chiral Compounds
Inspired by nature, synthetic chemists try to mimic the efficient metabolic networks in living organisms to build complex molecules by combining different types of catalysts in the same reaction vessel. These multistep cascade processes provide many advantages to synthetic procedures, resulting in higher productivities with lower waste generation and cost. However, combining different chemo- and biocatalysts can be challenging as reaction conditions might differ greatly. As a highly multidisciplinary field that benefits from advances in chemical catalysis, molecular biology and reaction engineering, this area of study is rapidly progressing. In this Review, we highlight recent trends and advances in the construction of multistep chemoenzymatic one-pot cascades to access chiral compounds as well as the different strategies to solve current challenges in the field
The weathering action of saxicolous lichens in maritime Antarctica
7 pages, figures and tables statistics.Xanthoria elegans (Link) Th Fr. and Lecidea
lapicida (Ach.) were studied on volcanic andesite, and
Rhizocarpon geooraphicum (L.) DC. and Bacidia stipata
Lamb on a volcanigenic sediment, using light microscopy,
infrared spectroscopy, X-ray diffraction and transmission
electron microscopy. Feldspars were present in the rocklichen
interface to a lesser extent than in the underlying
rock. R. geographicum was found to alter the minerals in
the rock on which it grew without producing any new
minerals in the rock/lichen interface, in contrast to the
observations for this species on granite in temperate
regions. Beneath of the thallus of L. lapicida there was
calcium oxalate and some micas of the illite type, which
may have been degradation products of various phyllosilicates
in the rock. B. stipata, an endemic Antarctic lichen,
had the greatest capacity to weather the rock and had
weddellite (dihydrate calcium oxalate) and calcite in the
contact area as well as many bacteria. The presence of
crystalline oxalate, imogolite, allophane, carbonates (calcite)
and amorphous material not found in the parent rock
indicates biomineralization processes attributable to the
lichens.We are pleased to acknowledge that this work
was supported by a grant number PB87 0229 from the Comisi6n
Asesora de Ciencia y Tecnologia. We are grateful to Mr. F. Pinto and
M. T. Carnota for technical assistance, and to Prof. Kappen and
William Sanders for help with the English manuscript.Peer reviewe
The Violent Youth of Bright and Massive Cluster Galaxies and their Maturation over 7 Billion Years
In this study we investigate the formation and evolution mechanisms of the
brightest cluster galaxies (BCGs) over cosmic time. At high redshift
(), we selected BCGs and most massive cluster galaxies (MMCGs) from
the Cl1604 supercluster and compared them to low-redshift ()
counterparts drawn from the MCXC meta-catalog, supplemented by SDSS imaging and
spectroscopy. We observed striking differences in the morphological, color,
spectral, and stellar mass properties of the BCGs/MMCGs in the two samples.
High-redshift BCGs/MMCGs were, in many cases, star-forming, late-type galaxies,
with blue broadband colors, properties largely absent amongst the low-redshift
BCGs/MMCGs. The stellar mass of BCGs was found to increase by an average factor
of from to . Through this and other
comparisons we conclude that a combination of major merging (mainly wet or
mixed) and \emph{in situ} star formation are the main mechanisms which build
stellar mass in BCGs/MMCGs. The stellar mass growth of the BCGs/MMCGs also
appears to grow in lockstep with both the stellar baryonic and total mass of
the cluster. Additionally, BCGs/MMCGs were found to grow in size, on average, a
factor of , while their average S\'ersic index increased by 0.45
from to , also supporting a scenario involving major
merging, though some adiabatic expansion is required. These observational
results are compared to both models and simulations to further explore the
implications on processes which shape and evolve BCGs/MMCGs over the past
7 Gyr.Comment: Accepted for publication in MNRA
Next Generation Cosmology: Constraints from the Euclid Galaxy Cluster Survey
We study the characteristics of the galaxy cluster samples expected from the
European Space Agency's Euclid satellite and forecast constraints on
cosmological parameters describing a variety of cosmological models. The method
used in this paper, based on the Fisher Matrix approach, is the same one used
to provide the constraints presented in the Euclid Red Book (Laureijs et
al.2011). We describe the analytical approach to compute the selection function
of the photometric and spectroscopic cluster surveys. Based on the photometric
selection function, we forecast the constraints on a number of cosmological
parameter sets corresponding to different extensions of the standard LambdaCDM
model. The dynamical evolution of dark energy will be constrained to Delta
w_0=0.03 and Delta w_a=0.2 with free curvature Omega_k, resulting in a
(w_0,w_a) Figure of Merit (FoM) of 291. Including the Planck CMB covariance
matrix improves the constraints to Delta w_0=0.02, Delta w_a=0.07 and a
FoM=802. The amplitude of primordial non-Gaussianity, parametrised by f_NL,
will be constrained to \Delta f_NL ~ 6.6 for the local shape scenario, from
Euclid clusters alone. Using only Euclid clusters, the growth factor parameter
\gamma, which signals deviations from GR, will be constrained to Delta
\gamma=0.02, and the neutrino density parameter to Delta Omega_\nu=0.0013 (or
Delta \sum m_\nu=0.01). We emphasise that knowledge of the observable--mass
scaling relation will be crucial to constrain cosmological parameters from a
cluster catalogue. The Euclid mission will have a clear advantage in this
respect, thanks to its imaging and spectroscopic capabilities that will enable
internal mass calibration from weak lensing and the dynamics of cluster
galaxies. This information will be further complemented by wide-area
multi-wavelength external cluster surveys that will already be available when
Euclid flies. [Abridged]Comment: submitted to MNRA
New Landmarks, Signs, and Findings in Optical Coherence Tomography
Spectral domain optical coherence tomography (SD-OCT) is a common useful noninvasive imaging instrument which is used for the diagnosis and follow-up of macular disorders. The clinical findings by OCT in these pathologies are well known. Currently, due to the development of this technology and its wide use, new OCT findings have been reported in the literature. The aim of this chapter is to describe new pathological or abnormal signs and findings in SD-OCT, including hyperreflective spots or dots, flyer saucer sign, outer retinal tubulations, dipping sign, focal choroidal excavation, outer retina-choroid complex splitting, foveal pseudocyst, brush border pattern, dome-shaped macula, pearl necklace sign, choroidal macrovessel, cystoid foveal degeneration, and disorganization of the retinal inner layers (DRIL)
The composition of endolithic communities in gypcrete is determined by the specific microhabitat architecture
The response to iron supplementation of pregnant women with the haemoglobin genotype AA or AS
The influence of haemoglobin genotype on the response to iron supplementation was studied in a randomized, double blind, placebo-controlled trial involving 497 multigravid pregnant women from a rural area of The Gambia. Women were randomly allocated to receive either oral iron (60mg elemental iron per day) or placebo. At 36 weeks of pregnancy, women who had received oral iron during pregnancy had higher mean haemoglobin, packed cell volume, plasma iron and ferritin levels than did women who received placebo. Iron supplementation of pregnant women with the AA haemoglobin genotype also resulted in increases in the packed cell volume (PCV) and haemoglobin level measured after delivery, and in the birth weight of the infant. However, in AS women PCV and haemoglobin level at delivery were lower in the supplemented group and supplementation was also associated with reduced birth weights. In malaria endemic areas, pregnant women with the haemoglobin genotype AS may not benefit from iron supplementation during pregnanc
Accessible lifelong learning at higher education:outcomes and lessons Learned at two different PilotSites in the EU4ALL Project
[EN] The EU4ALL project (IST-FP6-034778) has developed a general framework to
address the needs of accessible lifelong learning at Higher Education level consisting of several
standards-based interoperable components integrated into an open web service architecture
aimed at supporting adapted interaction to guarantee students' accessibility needs. Its flexibility
has supported the project implementation at several sites with different settings and various
learning management systems. Large-scale evaluations involving hundreds of users,
considering diverse disability types, and key staff roles have allowed obtaining valuable lessons
with respect to "how to adopt or enhance eLearning accessibility" at university. The project was
evaluated at four higher education institutions, two of the largest in Europe and two mediumsized.
In this paper, we focus on describing the implementation and main conclusions at the
largest project evaluation site (UNED), which was involved in the project from the beginning,
and thus, in the design process, and a medium-sized university that adopted the EU4ALL
approach (UPV). This implies dealing with two well-known open source learning environments
(i.e. dotLRN and Sakai), and considering a wide variety of stakeholders and requirements. Thus
the results of this evaluation serve to illustrate the coverage of both the approach and
developments.The authors would like to thank the European Commission for the financial support of the EU4ALL project (IST-2006-034478). The work at aDeNu is also supported by the Spanish Ministry of Science and Innovation (TIN2008-06862-C04-01/TSI “A2UN@”). Authors would also like to thank all the EU4ALL partners for their
collaboration.Boticario, JG.; Rodriguez-Ascaso, A.; Santos, OC.; Raffenne, E.; Montandon, L.; Roldán Martínez, D.; Buendía García, F. (2012). Accessible lifelong learning at higher education:outcomes and lessons Learned at two different PilotSites in the EU4ALL Project. Journal of Universal Computer Science. 18(1):62-85. http://hdl.handle.net/10251/37117628518
Adaptación y accesibilidad de las tecnologías para el aprendizaje
Monográfico de la RIED. Revista Iberoamericana de Educación a Distancia 13.
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