250 research outputs found
Dynamic behaviour of saturated poroelastic layers with embedded wall submited to seismic actions
Behaviour of poroelastic saturated materials submitted to dynamic actions is
strongly dependent of the solid skeleton permeability and the frequency of the movement.
Depending on these quantities, undrained behaviour or fully drained behaviour occurs for
total coupled interaction or for null interaction, respectively. Between these limit cases, some
relative movement occurs among solid skeleton and fluid, generating viscous damping,
which, in turn, modifies the elastic response of the system. This paper presents results of
coupled behaviour in poroelastic saturated layers with an embedded impermeable wall,
submitted to seismic actions. A Finite Element code developed at the University of Coimbra
(FEMEPDYN), with coupled formulation usâuwâp, was used for this purpose. Dynamic
responses of poroelastic layers with an embedded wall are compared with non-porous
materials for similar conditions. Damping of non-porous materials was previously calculated
by calibration of the Rayleigh coefficients in order to match the free field responses for both
materials types. Unlike for the free field analysis, results reveal some differences between
both materials responses with the presence of the wall, due to the volumetric deformations
imposed by the embedded wall. Also, those volumetric deformations have a more uniform
distribution in poroelastic layers with permeabilities that represent near total and near fully
drained behaviour
Plasmodium species mixed infections in two areas of Manhiça District, Mozambique
We compared the distribution patterns of individual Plasmodium species and mixed-species infections in two geographically close endemic areas, but showing environmental differences. Comparisons concerned circulating Plasmodium infections in both human and mosquito vector populations in the dry and wet seasons, at a micro-epidemiological level (households). Both areas revealed a very high overall prevalence of infection, all year-round and in all age groups. Plasmodium falciparum was the predominant species, being found in the vast majority of infected individuals regardless of the presence of other species. Plasmodium malariae and Plasmodium ovale occurred almost exclusively in mixed infections. Seasonal variation in P. malariae prevalence was observed in one area but not in the other. A decrease in P. malariae prevalence concurred with a marked increase of P. falciparum prevalence. However this was strongly dependent on age and when analysing infections at the individual level, a different pattern between co-infecting species was unveiled. Regarding transmission patterns, in both areas, P. falciparum gametocytes predominated in single infections regardless of age and P. malariae gametocyte carriage increased when its overall prevalence decreased
Global observational needs and resources for marine biodiversity
Otros autores: Best, B., Brandt, A., Goodwin, K., Iken, A., Marques, A., Miloslavich, P., Ostrowski, M., Turner, W., Achterberg, E., Barry, T., Bigatti, G., Henry, L.A., Ramiro-SĂĄnchez, B., DurĂĄn, P., Morato, T., Murray Roberts, J., GarcĂa-Alegre, A., Cuadrado, M., Murton, B.The diversity of life in the sea is critical to the health of ocean ecosystems that support living resources and therefore essential to the economic, nutritional, recreational, and health needs of billions of people. Yet there is evidence that the biodiversity of many marine habitats is being altered in response to a changing climate and human activity. Understanding this change, and forecasting where changes are likely to occur, requires monitoring of organism diversity, distribution, abundance, and health. It requires a minimum of measurements including productivity and ecosystem function, species composition, allelic diversity, and genetic expression. These observations need to be complemented with metrics of environmental change and socio-economic drivers. However, existing global ocean observing infrastructure and programs often do not explicitly consider observations of marine biodiversity and associated processes. Much effort has focused on physical, chemical and some biogeochemical measurements. Broad partnerships, shared approaches, and best practices are now being organized to implement an integrated observing system that serves information to resource managers and decision-makers, scientists and educators, from local to global scales. This integrated observing system of ocean life is now possible due to recent developments among satellite, airborne, and in situ sensors in conjunction with increases in information system capability and capacity, along with an improved understanding of marine processes represented in new physical, biogeochemical, and biological models
Peak effect in a superconducting DyBa2Cu3O7-y film at microwave frequencies
We report the observation of a peak in the microwave (9.55 GHz) surface
resistance in an epitaxial DyBa2Cu3O7-y superconducting film in magnetic fields
(parallel to the c axis) ranging between 0.2 to 0.9 Tesla. Such a peak is
absent in the measurements done in zero-field. The temperature and field
dependence of the peak suggests that this peak could be associated with the
peak effect phenomenon reflecting the order-disorder transformation in the
flux-line lattice. A strong dependence of this peak effect at frequencies close
to the depinning frequency of the flux line lattice is observed.Comment: 1 text, 4 figures (all postscript) to be published in Phys. Rev.
Mastocytosis: a Rare Case of Anaphylaxis in Paediatric Age and Literature Review
The term âmastocytosisâ denotes a heterogeneous group of disorders characterised by abnormal growth and accumulation of mast cells (MC) in one
or more organ systems. Symptoms result from MC chemical mediatorâs release, pathologic infiltration of neoplastic MC in tissues or both. Multiple molecular, genetic and chromosomal defects seem to contribute
to an autonomous growth, but somatic c-kit
D816V mutation is more frequently encountered, especially in systemic disease.
We present a literature review of mastocytosis and a rare case report of an 18 month-old-girl with a bullous dermatosis, respiratory distress and anaphylaxis,
as clinical manifestations of mastocytosis.
The developments of accepted classification systems and novel useful markers allowed a re-evaluation and updating of the classification of mastocytosis.
In paediatric age cutaneous forms of disease
prevail and may regress spontaneously. SM is more frequently diagnosed in adults and is a persistent(clonal) disease of bone marrow. The clinical course in these patients is variable.Today diagnostic criteria for each disease variant are reasonably well defined. There are, however, peculiarities,
namely in paediatric age, that makes the diagnostic approach difficult. Systemic disease may pose differential diagnostic problems resulting from multiple organ systems involvement. Coversly, the âunexplainedâ appearance of those symptoms with no skin lesions should raise the suspicion of MC disease. This case is reported in order to stress the clinical
severity and difficult diagnostic approach that paediatric mastocytosis may assume
Atmospheric effects on extensive air showers observed with the Surface Detector of the Pierre Auger Observatory
Atmospheric parameters, such as pressure (P), temperature (T) and density,
affect the development of extensive air showers initiated by energetic cosmic
rays. We have studied the impact of atmospheric variations on extensive air
showers by means of the surface detector of the Pierre Auger Observatory. The
rate of events shows a ~10% seasonal modulation and ~2% diurnal one. We find
that the observed behaviour is explained by a model including the effects
associated with the variations of pressure and density. The former affects the
longitudinal development of air showers while the latter influences the Moliere
radius and hence the lateral distribution of the shower particles. The model is
validated with full simulations of extensive air showers using atmospheric
profiles measured at the site of the Pierre Auger Observatory.Comment: 24 pages, 9 figures, accepted for publication in Astroparticle
Physic
Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter
Data collected by the Pierre Auger Observatory through 31 August 2007 showed
evidence for anisotropy in the arrival directions of cosmic rays above the
Greisen-Zatsepin-Kuz'min energy threshold, \nobreak{eV}. The
anisotropy was measured by the fraction of arrival directions that are less
than from the position of an active galactic nucleus within 75 Mpc
(using the V\'eron-Cetty and V\'eron catalog). An updated
measurement of this fraction is reported here using the arrival directions of
cosmic rays recorded above the same energy threshold through 31 December 2009.
The number of arrival directions has increased from 27 to 69, allowing a more
precise measurement. The correlating fraction is , compared
with expected for isotropic cosmic rays. This is down from the early
estimate of . The enlarged set of arrival directions is
examined also in relation to other populations of nearby extragalactic objects:
galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in
hard X-rays by the Swift Burst Alert Telescope. A celestial region around the
position of the radiogalaxy Cen A has the largest excess of arrival directions
relative to isotropic expectations. The 2-point autocorrelation function is
shown for the enlarged set of arrival directions and compared to the isotropic
expectation.Comment: Accepted for publication in Astroparticle Physics on 31 August 201
The Fluorescence Detector of the Pierre Auger Observatory
The Pierre Auger Observatory is a hybrid detector for ultra-high energy
cosmic rays. It combines a surface array to measure secondary particles at
ground level together with a fluorescence detector to measure the development
of air showers in the atmosphere above the array. The fluorescence detector
comprises 24 large telescopes specialized for measuring the nitrogen
fluorescence caused by charged particles of cosmic ray air showers. In this
paper we describe the components of the fluorescence detector including its
optical system, the design of the camera, the electronics, and the systems for
relative and absolute calibration. We also discuss the operation and the
monitoring of the detector. Finally, we evaluate the detector performance and
precision of shower reconstructions.Comment: 53 pages. Submitted to Nuclear Instruments and Methods in Physics
Research Section
Anisotropy studies around the galactic centre at EeV energies with the Auger Observatory
Data from the Pierre Auger Observatory are analyzed to search for
anisotropies near the direction of the Galactic Centre at EeV energies. The
exposure of the surface array in this part of the sky is already significantly
larger than that of the fore-runner experiments. Our results do not support
previous findings of localized excesses in the AGASA and SUGAR data. We set an
upper bound on a point-like flux of cosmic rays arriving from the Galactic
Centre which excludes several scenarios predicting sources of EeV neutrons from
Sagittarius . Also the events detected simultaneously by the surface and
fluorescence detectors (the `hybrid' data set), which have better pointing
accuracy but are less numerous than those of the surface array alone, do not
show any significant localized excess from this direction.Comment: Matches published versio
- âŠ