Comparison of Fused Glass Beads and Pressed Powder Pellets for the Quantitative Measurement of Al,Fe, Si and Ti in Bauxite by Laser‐Induced Breakdown Spectroscopy          下载免费PDF全文

Alexandrina A. C. Carvalho  Victoria C. Alves  Daniel M. Silvestre  Flávio O. Leme  Pedro V. Oliveira  Cassiana S. Nomura 《Geostandards and Geoanalytical Research》2017,41(4):585-592

Due to matrix interference and sample particle size effects, some of the most important and difficult issues in laser‐induced breakdown spectroscopy (LIBS) analysis are the calibration and quantitative measurement of a complex matrix. This study proposes the use of borate fusion as an alternative sample preparation procedure for the quantitative measurement of Al, Fe, Si and Ti in bauxite by LIBS. Analytical calibration curves were made using bauxite certified reference materials (CRM), and the precision and accuracy of the methods were evaluated by analysing an additional bauxite CRM, using two different approaches: pressed powder pellets and fused glass beads. The borate fusion method was the most suitable sample preparation technique, since particle size effects and matrix interference could be minimised, obtaining better linearity on the analytical calibration curves (r²), and more accurate and more precise results for bauxite analysis.  相似文献   

Poor housing and stroke mortality in population over 64 years old at the parish level,in mainland Portugal     

André Oliveira  António J. R. Cabral  Maria Fraga O. Martins  Pedro Cabral  Jorge M. Mendes  Mário Carreira 《GeoJournal》2017,82(4):665-682

Housing conditions can impact physical and mental health. In 2013, Portugal was still the fourth European Union country with the highest percentage of population without an adequately heated home in winter. Other adverse conditions are, for instance, overcrowding and living in older buildings. Some studies stress the relationship between stroke and poor living conditions in the elderly population, especially cold homes. Univariate and multivariate spatial cluster analysis were used to explore the relationship between excess stroke death risk, from 1998 to 2004, measured by the standardized mortality ratio (SMR) for several cohorts (including persons over 64 years old), and poor housing variables from the 2001 census, at the parish level in continental Portugal. A multivariate cluster of parishes, with population without any form of heating their homes as dominant condition, was detected in northwest Portugal. Mean and median SMR values across all cohorts were consistently higher within this cluster. This strengthens the hypothesis that cold homes deserve more attention in stroke prevention and mitigation amongst elderly persons, especially in northwestern continental Portugal.  相似文献   

Trace metal retention in mangrove ecosystems in Guanabara Bay,SE Brazil   总被引：1，自引：0，他引：1  

Machado W  Silva-Filho EV  Oliveira RR  Lacerda LD 《Marine pollution bulletin》2002,44(11):1277-1280

Along contrasting environmental conditions (e.g., degree of trace metal contamination and mangrove forest structural development), sediments of Laguncularia racemosa-dominated mangrove stands in Guanabara Bay (SE Brazil) presented a trend of trace metal accumulation in forms with low potential of remobilization and biotic uptake. Concurrently, a relatively low transfer of sediment-bound metals to L. racemosa leaves was observed, which may moderate the metal export from the forests via leaf litter transport and the metal availability to enter in food chains based on leaf consumption.  相似文献   

The lithium depletion boundary in NGC 2547 as a test of pre-main-sequence evolutionary models     

R. D. Jeffries  J. M. Oliveira 《Monthly notices of the Royal Astronomical Society》2005,358(1):13-29

Intermediate resolution spectroscopy from the European Southern Observatory Very Large Telescope is analysed for 63 photometrically selected low-mass  (0.08–0.30 M_⊙)  candidates of the open cluster NGC 2547. We have confirmed membership for most of these stars using radial velocities, and found that lithium remains undepleted for cluster stars with   I > 17.54 ± 0.14  and   K_s > 14.86 ± 0.12  . From these results, several pre–main-sequence evolutionary models give almost model independent ages of 34–36 Myr, with a precision of 10 per cent. These ages are only slightly larger than the ages of 25–35(±5) Myr obtained using the same models to fit isochrones to higher mass stars descending towards the zero-age main-sequence, both in empirically calibrated and theoretical colour–magnitude diagrams. This agreement between age determinations in different mass ranges is an excellent test of the current generation of low-mass pre–main-sequence stellar models and lends confidence to ages determined with either method between 30 and 120 Myr.  相似文献   

Membership, binarity and accretion among very low-mass stars and brown dwarfs of the σ Orionis cluster     

M. J. Kenyon  R. D. Jeffries  Tim Naylor  J. M. Oliveira  P. F. L. Maxted 《Monthly notices of the Royal Astronomical Society》2005,356(1):89-106

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On the Climate Impact of the Local Circulation in the Itaipu Lake Area   总被引：1，自引：0，他引：1  

Sônia M. S. Stivari  Amauri P. De Oliveira  Jacyra Soares 《Climatic change》2005,72(1-2):103-121

The impact of the Itaipu Lake on the climate and local circulation is investigated here using the meteorological information available in the area. The Itaipu Lake is an artificial water reservoir of 1460 km² (approximately 170 km by 7.5 km), formed in 1982 as part of the Itaipu Power Plant. It is situated on the Brazil-Paraguay frontier, in the central portion of Parana River Valley. The analysis of the available meteorological data (air and water temperatures, air relative humidity, precipitation and radiosonde soundings) provides observational evidences supporting the hypothesis that the Itaipu Lake presence has an important impact in the local circulation, inducing a local circulation with lake breeze characteristics showing horizontal wind divergence over the lake during daytime and convergence during nighttime. From the regional point of view, the Itaipu Lake formation has reduced the thermal amplitude of the diurnal air temperature cycle. The precipitation data, investigated here, has not indicated any systematic effect associated to the lake formation. The reason for the apparent inconsistency is that others phenomena (e.g., valley-mountain circulation and El Niño events) could be masking the impact of the lake formation on the rain deficit in the region.  相似文献   

Identification of Anthropogenic Features Through Application of Principal Component Analysis to Hydrochemical Data from the Sines Coastal Aquifer, SW Portugal     

Paula Galego Fernandes  Paula Carreira  Manuel Oliveira da Silva 《Mathematical Geology》2006,38(6):765-780

The Sines coastal sedimentary basin, a tectonic trough with a NE-SW orientation filled with Mesozoic and Cenozoic deposits, has two hydrogeological systems: the Mio-Pliocene and the Jurassic. Both systems are supplying water to the entire region with highly populated and industrialized areas. The aquifers are recharged in the outcrop areas, although the Jurassic aquifer also receives some contribution from the overlying Miocene rocks. The main groundwater flow direction in the Jurassic aquifer is E to W towards the Atlantic Ocean. In order to understand the influence of anthropogenic activities on the water quality, a statistical principal components analysis (PCA) was performed on the physical–chemical data from groundwater samples in both aquifers. Four components were obtained in the Jurassic and three in the Miocene. The principal components analyses indicate water–rock interactions as the major mechanism responsible for the groundwater solutes (mainly calcium-bicarbonate type), from the calcareous and dolomitic units. Anthropogenic contamination was identified in the influence of the water compositions, corresponding to local polluting inputs. These were magnesium, sulfate, nitrate, iron and copper for PC 3 in the Jurassic and sodium, chloride, nitrate and manganese for PC 2 in the Miocene. These account for about 13% of the system total variance in the Jurassic aquifer and near 23% in the Miocene one.  相似文献   

Characterization of a profile of residual soil from granite combining geological, geophysical and mechanical testing techniques     

A. Viana Da Fonseca  J. Carvalho  C. Ferreira  J. A. Santos  F. Almeida  E. Pereira  J. Feliciano  J. Grade  A. Oliveira 《Geotechnical and Geological Engineering》2006,24(5):1307-1348

This paper summarizes the results of an experimental site investigation and characterization survey, on a residual (saprolitic) soil from granite, in the framework of a research project led by the Faculty of Engineering of the University of Porto (FEUP). This project aims at characterizing these unusual soils in the context of the development of an International Prediction Event (Class A) on the behaviour of different types of piles. A very extensive site characterization campaign, including a large variety of in-situ tests and field methods, has been held. These investigations comprised the application of several geophysical borehole and surface methods, namely P- and S-wave seismic refraction, reflection, cross-hole (CH), down-hole (DH), electrical resistivity imaging and ground probing radar (GPR), as well as mechanical tests, namely SPT, CPT and DMT, among others. The site is geologically formed by an upper layer of heterogeneous residual granitic soil, overlaying rather weathered granite contacting a gneissic migmatite. Direct and indirect results from some of the referred surveys were compared between them and with some of the available geological and geotechnical information, namely those obtained from seismic, electrical and GPR profiles, conducted adjacent to three boreholes in which undisturbed soil samples were collected previously to geophysical data acquisition. In addition, a comprehensive laboratory testing program was carried out using the collected undisturbed samples. A discussion of the obtained results is hereby presented, giving emphasis to the correlations encountered between the different tests, specific of saprolitic soils with weak relic structures.  相似文献   

Influence of particle and surface quality on the vitrinite reflectance of dispersed organic matter: Comparative exercise using data from the qualifying system for reflectance analysis working group of ICCP     

A.G. Borrego  C.V. Araujo  A. Balke  B. Cardott  A.C. Cook  P. David  D. Flores  M. Hmor-Vid  W. Hiltmann  W. Kalkreuth  J. Koch  C.J. Kommeren  J. Kus  B. Ligouis  M. Marques  J.G. Mendona Filho  M. Misz  L. Oliveira  W. Pickel  K. Reimer  P. Ranasinghe  I. Surez-Ruiz  A. Vieth 《International Journal of Coal Geology》2006,68(3-4):151-170

The development of a qualifying system for reflectance analysis has been the scope of a working group within the International Committee for Coal and Organic Petrology (ICCP) since 1999, when J. Koch presented a system to qualify vitrinite particles according to their size, proximity to bright components and homogeneity of the surface. After some years of work aimed at improving the classification system using photomicrographs, it was decided to run a round robin exercise on microscopy samples. The classification system tested consists of three qualifiers ranging from excellent to low quality vitrinites with an additional option for unsuitable vitrinites. This paper reports on the results obtained by 22 analysts who were asked to measure random reflectance readings on vitrinite particles assigning to each reading a qualifier. Four samples containing different organic matter types and a variety of vitrinite occurrences have been analysed. Results indicated that the reflectance of particles classified as excellent, good or poor compared to the total average reflectance did not show trends to be systematically lower or higher for the four samples analysed. The differences in reflectance between the qualifiers for any given sample were lower than the scatter of vitrinite reflectance among participants. Overall, satisfactory results were obtained in determining the reflectance of vitrinite in the four samples analysed. This was so for samples having abundant and easy to identify vitrinites (higher plant-derived organic matter) as well as for samples with scarce and difficult to identify particles (samples with dominant marine-derived organic matter). The highest discrepancies were found for the organic-rich oil shales where the selection of the vitrinite population to measure proved to be particularly difficult. Special instructions should be provided for the analysis of this sort of samples. The certainty of identification of the vitrinite associated with the vitrinite reflectance values reported has been assessed through a reliability index which takes into account the number of readings and the coefficient of variation. The same statistical approach as that followed in the ICCP vitrinite reflectance accreditation program for single seam coals has been used for data evaluation. The results indicated low to medium dispersion for 17 out of 22 participants. This, combined with data from other sets of comparative analyses over a long period, is considered an encouraging result for the establishment of an accreditation program on vitrinite reflectance measurements in dispersed organic matter.  相似文献   

A combined structural and seasonal approach to assess wildfire susceptibility and hazard in summertime     

Bergonse  Rafaello  Oliveira  Sandra  Gonçalves  Ana  Nunes  Sílvia  da Câmara  Carlos  Zêzere  José Luis 《Natural Hazards》2021,106(3):2545-2573

Natural Hazards - Wildfire susceptibility and hazard models based on drivers that change only on a multiyear timescale are considered of a structural nature. They ignore specific short-term...  相似文献