11,250 research outputs found
Urban growth and loss of green spaces in the metropolitan areas of São Paulo and Mexico City: effects of land-cover changes on climate and water flow regulation
Urban green spaces provide ecosystem services that directly or indirectly benefit people, however, urban growth (especially in developing countries) generates the loss of these green areas and consequently of their ecosystem services. This paper aims to present the effects of land use and land cover changes in the last 30 years on two basic urban ecosystem services, water flow regulation and local and regional climate in two of main Latin American megacities (São Paulo and Mexico City). The study focuses on urban green spaces because they reduce the urban heat island effects, improve air quality, create habitats for biodiversity conservation, provide cultural services, and contribute to flooding prevention and groundwater conservation. A spatial analysis with the aid of geographic information systems was performed to assess (i) the urbanization process of the Metropolitan Areas of both cities over time; (ii) how this process generated changes in the land cover in both metropolises, and (iii) how these changes caused environmental negative impacts on ecosystem services. The loss of green areas as a consequence of urban expansion in the Metropolitan Areas of São Paulo and Mexico City changed the spatial distribution of urban heat island and increased the surface runoff, generating floods during the rainy periods. Our results suggest the urgent need for implementation of ecosystem-based spatial planning and ecological restoration of urban green areas in both studied cities to prevent further losses in ecosystem services and to improve the quality of life of urban inhabitants
Functional characterization of 8-oxoguanine DNA glycosylase of Trypanosoma cruzi
The oxidative lesion 8-oxoguanine (8-oxoG) is removed during base excision repair by the 8-oxoguanine DNA glycosylase 1 (Ogg1). This lesion can erroneously pair with adenine, and the excision of this damaged base by Ogg1 enables the insertion of a guanine and prevents DNA mutation. In this report, we identified and characterized Ogg1 from the protozoan parasite Trypanosoma cruzi (TcOgg1), the causative agent of Chagas disease. Like most living organisms, T. cruzi is susceptible to oxidative stress, hence DNA repair is essential for its survival and improvement of infection. We verified that the TcOGG1 gene encodes an 8-oxoG DNA glycosylase by complementing an Ogg1-defective Saccharomyces cerevisiae strain. Heterologous expression of TcOGG1 reestablished the mutation frequency of the yeast mutant ogg1-/- (CD138) to wild type levels. We also demonstrate that the overexpression of TcOGG1 increases T. cruzi sensitivity to hydrogen peroxide (H2O2). Analysis of DNA lesions using quantitative PCR suggests that the increased susceptibility to H2O2 of TcOGG1-overexpressor could be a consequence of uncoupled BER in abasic sites and/or strand breaks generated after TcOgg1 removes 8-oxoG, which are not rapidly repaired by the subsequent BER enzymes. This hypothesis is supported by the observation that TcOGG1-overexpressors have reduced levels of 8-oxoG both in the nucleus and in the parasite mitochondrion. The localization of TcOgg1 was examined in parasite transfected with a TcOgg1-GFP fusion, which confirmed that this enzyme is in both organelles. Taken together, our data indicate that T. cruzi has a functional Ogg1 ortholog that participates in nuclear and mitochondrial BER. © 2012 Furtado et al
Photo-z Performance for Precision Cosmology
Current and future weak lensing surveys will rely on photometrically
estimated redshifts of very large numbers of galaxies. In this paper, we
address several different aspects of the demanding photo-z performance that
will be required for future experiments, such as the proposed ESA Euclid
mission. It is first shown that the proposed all-sky near-infrared photometry
from Euclid, in combination with anticipated ground-based photometry (e.g.
PanStarrs-2 or DES) should yield the required precision in individual photo-z
of sigma(z) < 0.05(1+z) at I_AB < 24.5. Simple a priori rejection schemes based
on the photometry alone can be tuned to recognise objects with wildly
discrepant photo-z and to reduce the outlier fraction to < 0.25% with only
modest loss of otherwise usable objects. Turning to the more challenging
problem of determining the mean redshift of a set of galaxies to a
precision of 0.002(1+z) we argue that, for many different reasons, this is best
accomplished by relying on the photo-z themselves rather than on the direct
measurement of from spectroscopic redshifts of a representative subset of
the galaxies. A simple adaptive scheme based on the statistical properties of
the photo-z likelihood functions is shown to meet this stringent systematic
requirement. We also examine the effect of an imprecise correction for Galactic
extinction and the effects of contamination by fainter over-lapping objects in
photo-z determination. The overall conclusion of this work is that the
acquisition of photometrically estimated redshifts with the precision required
for Euclid, or other similar experiments, will be challenging but possible.
(abridged)Comment: 16 pages, 11 figures; submitted to MNRA
Recém-Nascidos com Cardiopatia. Diagnóstico Pré e Pós-Natal
Com o objectivo de avaliar aspectos que se prendem com o diagnóstico das cardiopatias no perÃodo pré e neo-natal, os autores
apresentam um estudo prospectivo de Janeiro a Junho de 1994, durante o qual foram avaliados 165 recém-nascidos, 138 no ambulatório
(Grupo I) e 27 no internamento (Grupo II).
No Grupo I foram vigiadas 91% das gravidezes, 33% tendo risco para cardiopatia, um quarto destas realizou ecocardiograma fetal. No Grupo II foram vigiadas 74% das gravidezes, havendo em 50% risco para cardiopatia, tendo 30% destas feito ecocardiograma fetal. As principais causas de envio dos recém-nascidos foram: sopro cardÃaco (77% Grupo 1; 15% Grupo II), cianose (4% Grupo I;15% Grupo II) e a associação das duas (2% Grupo I; 22% Grupo II). A idade de suspeita / diagnóstico foi, em média 6/8 dias no Grupo I e 4/4 dias no Grupo II. No Grupo I, 89 recém-nascidos não tinham doença cardÃaca, 34 tinham comunicação interventricular, 3 defeito do septo aurÃculo-ventricular e 2 tetralogia de Fallot; 10 eram portadores de trissomia 21. No Grupo II, 25 recém-nascidos tinham cardiopatia sendo as mais frequentes a transposição das grandes artérias e os obstáculos esquerdos (24% cada). Onze fizeram cateterismo cardÃaco e 12 cirurgia, tendo 1 falecido.
Conclui-se que, apesar da maioria dos recém-nascidos avaliados ter nascido sem diagnóstico pré-natal, o diagnóstico das cardiopatias graves fez-se na primeira semana de vida a seguir ao parto, nomeadamente o da transposição das grandes artérias, permitindo a tempo o tratamento cirúrgico mais adequado.
No entanto, embora não fosse demonstrado neste estudo, continua a ser uma realidade o transporte por longas distâncias de recém-
-nascidos com cardiopatia crÃtica, surgindo por isso alguns em condições não ideais, e outros fora do perÃodo adequado para certos
tipos de tratamento. Por outro lado, a maioria dos enviados à consulta têm sopros transitórios, não se encontrando já, em cerca de metade, qualquer alteração na avaliação cardiovascular pelo especialista
Limits on decaying dark energy density models from the CMB temperature-redshift relation
The nature of the dark energy is still a mystery and several models have been
proposed to explain it. Here we consider a phenomenological model for dark
energy decay into photons and particles as proposed by Lima (J. Lima, Phys.
Rev. D 54, 2571 (1996)). He studied the thermodynamic aspects of decaying dark
energy models in particular in the case of a continuous photon creation and/or
disruption. Following his approach, we derive a temperature redshift relation
for the CMB which depends on the effective equation of state and on
the "adiabatic index" . Comparing our relation with the data on the CMB
temperature as a function of the redshift obtained from Sunyaev-Zel'dovich
observations and at higher redshift from quasar absorption line spectra, we
find , adopting for the adiabatic index ,
in good agreement with current estimates and still compatible with
, implying that the dark energy content being constant in time.Comment: 8 pages, 1 figur
Disfunção tiróidea e amiodarona
Although most patients remain clinically euthyroid, some develop amiodarone-induced hyperthyroidism (HPEAI) or hypothyroidism (HPOAI). The authors present a retrospective analysis of ten patients with amiodarone-induced thyroid dysfunction. Six patients were female and mean amiodarone intake was 17.7 months. HPOIA was more common (six patients). From all the patients with HPEAI, two had type 2, one had type 1, and one had type 3 hyperthyroidism. Symptoms suggestive of thyroid dysfunction occurred in five patients, most of them with HPOAI. In HPEAI, the most frequent symptom was exacerbation of arrhythmia (three patients). Discontinuation of amiodarone and treatment with levothyroxine was chosen in 83.3% of the HPOAI cases, while thyonamide treatment with corticosteroids and without amiodarone was the option in 75% of the HPEAI cases. There were three deaths, all in patients with HPEAI. HPEAI is potentially fatal. The clinical picture may be vague, so the thyroid monitoring is mandatory
Stream sediment analysis for Lithium (Li) exploration in the Douro region (Portugal): A comparative study of the spatial interpolation and catchment basin approaches
Lithium (Li) was recently added to the list of critical raw materials by the European Union due to its significance for the green energy transition. Thus, the development of new toolchains to make Li exploration more economic and more effective is needed. Stream sediment analysis can play an important part in these new tool chains. In this work, two historical stream sediment datasets covering parts of the Fregeneda-Almendra pegmatite field in the Douro region (Portugal) were reprocessed considering two distinct approaches: spatial interpolation through inverse distance weighting (IDW) and the catchment basin approach using the concentration area (C-A) fractal analysis. The following objectives were delineated: (i) determine pathfinder elements for Li, considering relevant associations in the mineralization sources; (ii) compare the performance of both approaches; (iii) identify new target areas for Li. In the case of spatial interpolation, the highest Li values were associated to granites although the use of key elements allowed lithological discrimination and the delineation of target areas. In the catchment basin approach, fractal analysis proved to be effective in decreasing the number of areas of interest with high accuracy (>75%) when considering the previously mapped Li-pegmatites. One of the limitations identified was the number of anomalous basins related to the granites, despite the use of pathfinder elements allowing discriminating granite-from pegmatite-related Li anomalies. Comparing the two approaches, the spatial interpolation method is more adequate for the early stages of exploration (reconnaissance), while the catchment basin approach is more suited for prospect-scale exploration. Field validation of the results identified one pegmatite containing Li mineralization and three others with favorable signs for Li mineralization in the Douro region
Analysis of Chromobacterium sp. natural isolates from different Brazilian ecosystems
<p>Abstract</p> <p>Background</p> <p><it>Chromobacterium violaceum </it>is a free-living bacterium able to survive under diverse environmental conditions. In this study we evaluate the genetic and physiological diversity of <it>Chromobacterium </it>sp. isolates from three Brazilian ecosystems: Brazilian Savannah (Cerrado), Atlantic Rain Forest and Amazon Rain Forest. We have analyzed the diversity with molecular approaches (16S rRNA gene sequences and amplified ribosomal DNA restriction analysis) and phenotypic surveys of antibiotic resistance and biochemistry profiles.</p> <p>Results</p> <p>In general, the clusters based on physiological profiles included isolates from two or more geographical locations indicating that they are not restricted to a single ecosystem. The isolates from Brazilian Savannah presented greater physiologic diversity and their biochemical profile was the most variable of all groupings. The isolates recovered from Amazon and Atlantic Rain Forests presented the most similar biochemical characteristics to the <it>Chromobacterium violaceum </it>ATCC 12472 strain. Clusters based on biochemical profiles were congruent with clusters obtained by the 16S rRNA gene tree. According to the phylogenetic analyses, isolates from the Amazon Rain Forest and Savannah displayed a closer relationship to the <it>Chromobacterium violaceum </it>ATCC 12472. Furthermore, 16S rRNA gene tree revealed a good correlation between phylogenetic clustering and geographic origin.</p> <p>Conclusion</p> <p>The physiological analyses clearly demonstrate the high biochemical versatility found in the <it>C. violaceum </it>genome and molecular methods allowed to detect the intra and inter-population diversity of isolates from three Brazilian ecosystems.</p
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