Modelling Estuarine Biogeochemical Dynamics: From the Local to the Global Scale     

Pierre Regnier  Sandra Arndt  Nicolas Goossens  Chiara Volta  Goulven G. Laruelle  Ronny Lauerwald  Jens Hartmann 《Aquatic Geochemistry》2013,19(5-6):591-626

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Artificial neural networks and geostatistical models for housing valuations in urban residential areas     

M. Carmen Morillo Balsera  Sandra Martínez-Cuevas  Iñigo Molina Sánchez  César García-Aranda  M. Estibaliz Martinez Izquierdo 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(2):184-193

Property valuation studies often use classical statistics techniques. Among these techniques, the Artificial Neural Networks are the most applied, overcoming the inflexibility and the linearity of the hedonic models. Other researchers have used Geostatistics techniques, specifically the Kriging Method, for interpreting spatial-temporal variability and to predict housing unit prices. The innovation of this study is to highlight how the Kriging Method can help to better understand the urban environment, improving the results obtained by classical statistics. This study presents two different methods that share the general objective of extracting information regarding a city’s housing from datasets. The procedures applied are Ordinary Kriging (Geostatistics) and Multi-Layer Perceptron algorithm (Artificial Neural Networks). These methods were used to predict housing unit prices in the municipality of Pozuelo de Alarcon (Madrid). The implementation of both methods provides us with the urban characteristics of the study area and the most significant variables related to price. The main conclusion is that the Ordinary Kriging models and the Neural Networks models, applied to predicting housing unit prices are necessary methodologies to improve the information obtained in classical statistical techniques.

Abbreviations: ANN: Artificial Neural Networks; OK: ordinary Kriging; MLP: multi-layer perceptron  相似文献   

Macrobenthos and multi-molecular markers as indicators of environmental contamination in a South American port (Mar del Plata,Southwest Atlantic)     

Mariano J. Albano  Paulo da Cunha Lana  Claudia Bremec  Rodolfo Elías  César C. Martins  Natalia Venturini  Pablo Muniz  Silvia Rivero  Eduardo A. Vallarino  Sandra Obenat 《Marine pollution bulletin》2013

We evaluated benthic habitat quality along a presumed contamination gradient in the Mar del Plata port (Southwestern Atlantic) by coupling biological and chemical proxies in a multidisciplinary approach. Organic matter and photosynthetic pigment contents were higher in silty-clay bottoms of the inner port sites. Levels of all fecal steroids decreased from the inner sites to the port inlet. High concentrations of coprostanol in the inner sites seemed to derive from a permanent population of sea lions rather than from sewage outfalls due to coprostanol/epicoprostanol ratio (IV) values <2.5. PAHs levels were also higher in the inner sector, related to both biomass combustion and petroleum combustion associated to local marine traffic. High disturbance and low ecological status were reflected in low benthic diversity and high AMBI values in the inner sites.  相似文献   

Impact of Pleistocene–Holocene climate shifts on vegetation and fire dynamics and its implications for Prearchaic humans in the central Great Basin,USA     

Sandra Olivia Brugger  David Rhode 《第四纪科学杂志》2020,35(8):987-993

The effects of climate change during the Terminal Pleistocene–Early Holocene transition on ecosystems and early Prearchaic hunter-gatherers in the central Great Basin of North America are not well understood. We present a palynological reconstruction of regional vegetation and fire history in Grass Valley, central Nevada, from ~14 to ~7.5k cal a BP showing that Pinus-dominated woodlands were replaced by dry-adapted steppe and desert vegetation accompanied by an increase in regional fire activity at the beginning of the Holocene, in response to summer warming and a drying climate. Following a severe drought period peaking ~10.2–9.3k cal a BP, Pinus woodlands partially recovered contemporaneously with the 8.2k cal a BP climate anomaly. Local wetlands provided important resource patches for human foraging societies, and periodic declines of wetlands in response to changing local hydrological conditions may have necessitated adjustments in subsistence and settlement practices and technology.  相似文献   

Sensitivity analysis of a morphodynamic modelling system applied to a coastal lagoon inlet     

Sandra Plecha  Paulo A. Silva  Nuno Vaz  Xavier Bertin  Anabela Oliveira  André B. Fortunato  João M. Dias 《Ocean Dynamics》2010,60(2):275-284

This work investigates the recent morphological changes at the inlet of a complex coastal system (Ria de Aveiro lagoon, Portugal). This study was carried out using bathymetric data analysis and numerical simulations obtained with the 2DH morphodynamic modelling system MORSYS2D. The present simulations considered only tidal forcing, and a sensitivity analysis was performed by tuning the formula used to compute the sediment transports. A non-uniform sediment grain size distribution for the Ria de Aveiro inlet is considered in the numerical simulations, based on surveys performed in this area. The model results are analysed to assess if they resemble the observed trends of erosion and deposition, as calculated from bathymetric data. A quantitative analysis of the differences between the bathymetric changes obtained through surveys and the numerical results over a period of 3 years considering different sediment transport formulations shows that the formulations of Ackers and White (1973) and Engelund and Hansen (1967) are the ones that best describe the morphodynamic changes driven by tides in the Ria de Aveiro inlet.  相似文献   

Analysis of post-disaster damage and disruptive impacts on the operating status of small businesses after Hurricane Katrina     

Sandra Sydnor  Linda Niehm  Yoon Lee  Maria Marshall  Holly Schrank 《Natural Hazards》2017,85(3):1637-1663

When small businesses are impacted by natural hazard events, hazard and sociological researchers may have access to collect data from a sample of open businesses, in hopes of distilling lessons that might help reduce vulnerability to future disasters. Lessons from demised businesses might be more useful in reducing business closure for increasing business sustainability to disasters. Using interviews from a random sample of 371 open and 126 closed businesses’ experiences with Hurricane Katrina, discrete choice methods examine the relationship between the impact of post-disaster damage, loss of lifelines, types of delays in reopening, and cascading damages on business continuity. This unique sample offers the opportunity to determine whether damage to operating businesses was different than that of demised businesses. Respondents provided pre-Katrina data up through the last interviews in 2013. Results demonstrate that damage may have a short-term effect on operating status; it was associated with immediate demise but had much less effect on longer-term recovery. Additionally, it is evident that there is one path to failure. Businesses that did reopen, but later closed, may have been impacted by a cascade of both exogenous and endogenous shocks.  相似文献   

Predation and competition effects on the size diversity of aquatic communities     

Xavier D. Quintana  Matías Arim  Anna Badosa  José María Blanco  Dani Boix  Sandra Brucet  Jordi Compte  Juan J. Egozcue  Elvira de Eyto  Ursula Gaedke  Stéphanie Gascón  Luis Gil de Solá  Kenneth Irvine  Erik Jeppesen  Torben L. Lauridsen  Rocío López-Flores  Thomas Mehner  Susana Romo  Martin Søndergaard 《Aquatic Sciences - Research Across Boundaries》2015,77(1):45-57

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Public health in the Canadian Arctic: contributions from International Polar Year research     

Sandra Owens  Philippe De Wals  Grace Egeland  Christopher Furgal  Yang Mao  Gerald Y. Minuk  Paul A. Peters  Manon Simard  éric Dewailly 《Climatic change》2012,115(1):259-281

The contributions of several IPY health projects are highlighted in the context of population health indicators for Inuit Nunangat. Food and housing are two critical social determinants of health contributing to health issues on many levels. The nutritional deficit associated with food insecurity and the transition away from traditional and towards market foods represents a dual risk with profound consequences. Knowledge of the physiological benefits associated with traditional food consumption is increasing, including for mental health and chronic disease. Ensuring the safety of traditional foods in terms of zoonotic diseases is thus highly valuable and efforts to institute adequate monitoring and address knowledge gaps are underway. Acute respiratory disease among the young remains a significant public health issue with potential long term effects. The human papilloma virus is manifesting itself among women across northern Canada with high risk types that are more similar to profiles observed in Europe than in North America with possible implications for immunization programs. Despite a high prevalence of Hepatitis B virus infections among residents of Inuit Nunangat, the outcomes appear to be relatively benign. Communication of new knowledge on the manifestation of this virus among northern populations is provided to health care providers in the North through modern technology.  相似文献   

Nitrogen-containing compounds in two CR2 meteorites: N composition, molecular distribution and precursor molecules     

Sandra Pizzarello  William Holmes 《Geochimica et cosmochimica acta》2009,73(7):2150-14090

Amino acids, amines and aldehydes were obtained from the water extracts of two CR2 carbonaceous chondrites from Antarctica and analyzed for their molecular and ¹⁵N isotopic content. These compounds were found to differ significantly from those of CM chondrites in both overall abundances and molecular distribution. The amino acids suites comprise a preponderant abundance of linear, 2-H amino acids, show rapid non-linear decrease with the compounds’ increasing chain length and include protein amino acids never identified in meteorites before, such as threonine, tyrosine and phenylalanine. The presence of tertiary amines as well as a diverse, large abundance of aldehydes and ketones also distinguishes both CR2 organic suites. The δ¹⁵N values determined for CR2 amino acids have a distribution between molecular subgroups that is opposite to the one of their δD values, with 2-H amino acids having higher δ¹⁵N and lower δD values than 2-methyl amino acids, while the opposite is true for 2-methyl amino acids. Based on theoretical data, these isotopic findings would place the formation of the two amino acid groups or their direct precursors at different ISM stages of star formation.  相似文献   

Point defects and pre-dose requirements for sensitization of the 300°C TL peak in natural quartz     

Pedro L. Guzzo  Helen J. Khoury  Milena R. Miranda  Sandra B. Barreto  Armando H. Shinohara 《Physics and Chemistry of Minerals》2009,36(2):75-85

This paper discusses the structural features required to stimulate a strong thermoluminescence (TL) glow peak near 300°C in clear natural quartz. For that reason, fresh TL data taken from several specimens prepared from five single crystals with known impurity content are shown. The TL emission was measured with a test dose of 10 mGy of γ-rays in the readout intervals 50–160 and 160–320°C. The readings were carried out prior and after the administration of a pre-dose of 175 kGy of γ-rays followed by heat-treatments at 400°C. For each single specimen, the OH content and the population of inclusions were evaluated by infrared spectroscopy and optical microscopy, respectively. The darkening induced by high γ dose was evaluated by optical spectroscopy. It was observed that the absorption at 475 nm and TL responses decrease with increase of the OH. It was shown that both smoky darkening and TL signals were better explained in terms of Li/Al and Li/OH content ratios rather than the absolute values of aluminum and alkali concentrations. The sensitization with high γ dose and heating is essential to create and stabilize a class of defects sites with Li⁺ ions dislodged from [AlO₄/Li]⁰ and Li-dependent OH centers. It is suggested that the defect sites formed with Li⁺ act as electron traps during test dose irradiation, whereas electron-hole recombination occurs essentially at [AlO₄]⁰ centers during the TL output near 300°C.  相似文献