969 resultados para explanatory variables
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Understanding the fluctuations in population abundance is a central question in fisheries. Sardine fisheries is of great importance to Portugal and is data-rich and of primary concern to fisheries managers. In Portugal, sub-stocks of Sardina pilchardus (sardine) are found in different regions: the Northwest (IXaCN), Southwest (IXaCS) and the South coast (IXaS-Algarve). Each of these sardine sub-stocks is affected differently by a unique set of climate and ocean conditions, mainly during larval development and recruitment, which will consequently affect sardine fisheries in the short term. Taking this hypothesis into consideration we examined the effects of hydrographic (river discharge), sea surface temperature, wind driven phenomena, upwelling, climatic (North Atlantic Oscillation) and fisheries variables (fishing effort) on S. pilchardus catch rates (landings per unit effort, LPUE, as a proxy for sardine biomass). A 20-year time series (1989-2009) was used, for the different subdivisions of the Portuguese coast (sardine sub-stocks). For the purpose of this analysis a multi-model approach was used, applying different time series models for data fitting (Dynamic Factor Analysis, Generalised Least Squares), forecasting (Autoregressive Integrated Moving Average), as well as Surplus Production stock assessment models. The different models were evaluated, compared and the most important variables explaining changes in LPUE were identified. The type of relationship between catch rates of sardine and environmental variables varied across regional scales due to region-specific recruitment responses. Seasonality plays an important role in sardine variability within the three study regions. In IXaCN autumn (season with minimum spawning activity, larvae and egg concentrations) SST, northerly wind and wind magnitude were negatively related with LPUE. In IXaCS none of the explanatory variables tested was clearly related with LPUE. In IXaS-Algarve (South Portugal) both spring (period when large abundances of larvae are found) northerly wind and wind magnitude were negatively related with LPUE, revealing that environmental effects match with the regional peak in spawning time. Overall, results suggest that management of small, short-lived pelagic species, such as sardine quotas/sustainable yields, should be adapted to a regional scale because of regional environmental variability.
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Small pelagic fishes are particularly abundant in areas with high environmental variability (zones of coastal upwelling and areas of tidal mixing and river discharge), and because of this, their abundance suffers large inter-annual and inter-decadal fluctuations. In Portugal, the most important species in terms of landings are European sardine, Atlantic horse mackerel and Atlantic chub mackerel. Small pelagic fish landings account for 62.8 % of the total fish biomass and represent 32.7 % of the economical value of all catches. We have investigated trends in landings of these small pelagic fishes and detected the effects of environmental factors in this fishery. In order to explain the variability of landings of small pelagic fishes, we have used official landings (1965-2012) for trawling and purse seine fisheries and applied generalized linear models, using the North Atlantic Oscillation index (NAO) (annual and winter NAO index), sea surface temperature (SST), wind data (strength and North-South and East-West wind components) and rainfall, as explanatory variables. Regression analysis was used to describe the relationship between landings and SST. The models explained between 50.16 and 51.07 % of the variability of the LPUE, with the most important factors being winter NAO index, SST and wind strength. The LPUE of European sardine and Atlantic horse mackerel was negatively correlated with SST, and LPUE of Atlantic chub mackerel was positively correlated with SST. The use of landings of three important species of small pelagic fishes allowed the detection of variations in landings associated with changes in sea water temperature and NAO index.
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Objetivo: Determinar un modelo predictivo para uso del condón y consumo de alcohol como conductas de riesgo relacionadas el contagio de VIH/Sida en mujeres trabajadoras sexuales de la ciudad de Bogotá en el año 2015. Métodos Estudio de tipo transversal con diseño observacional, se tomaron 255 mujeres trabajadoras sexuales de la ciudad de Bogotá; La información analizada fue tomada del estudio realizado en cinco ciudades de Colombia en el año 2015, las hipótesis planteadas se soportaron en la asociación entre las condiciones sociodemográficas, de conocimiento, practicas, hábitos, apoyo social y de ocupación propia de las mujeres trabajadoras sexuales que podían explicar y predecir la adopción de conductas riesgosas para VIH/sida como son el uso del condón y el consumo de alcohol en ejercicio de su ocupación. Resultados El promedio de edad de inicio en el trabajo sexual fue 22,1±7,1 años, tres cuartas partes son solteras y residen en estrato dos y tres; el 96,5% dijo usar el condón con el último cliente y el 27,8% de ellas consumió alcohol durante su último servicio. En la conducta de riesgo uso del condón, se encontraron asociados entre otras, la edad [OR=1,10(1,03-1,17)], vivir en estrato dos [OR=7,7(1,5-39,5)], el ingreso por trabajo sexual [OR=1,0(1,0-1,0)], la disponibilidad del condón para el servicio [OR=0,03(0,008-0,16)] y contar con otro método de planificación (ligadura de trompas) [OR=4,47(1,0-18,3)]. En la conducta de riesgo consumo de alcohol, se encontró asociado ente otros: estrato socioeconómico dos [OR=5,8(1,54-22,3)], nivel de escolaridad secundaria [OR=0,12(0,16-0,96)], vivir con otros familiares [OR=3,45(1,7-7,02)], ingreso por trabajo sexual [OR=1,0(1,0-1,0)] y el sitio donde se ofrece el servicio [OR=0,07(0,04-0,15)]. Después de ajustar, se encontró que las variables que mejor explican el uso del condón fueron edad [OR=1,1(1,02-1,17)] y disponibilidad del condón [OR=0,04(0,008-0,024)], el modelo tuvo poca sensibilidad 33,3% y buena capacidad predictiva (84,6%). Las variables que mejor explicaron el consumo de alcohol durante el servicio fueron edad [OR= 0,95(0,91-0,98)], Número de clientes por semana [OR=0,9(0,90-0,98)], sitio donde ofrece el servicio [OR=7,1(3,45-14,8)], y estrato socioeconómico [OR=1,8 (0,90-3,83)], resultando un modelo con buena sensibilidad (71,8%) y buena capacidad predictiva (86,4%). Conclusiones Aspectos como la edad, el estrato socioeconómico, escolaridad, estado civil, ingreso económico por trabajo sexual, edad de inicio en el trabajo sexual, número de clientes antiguos en la última semana, disponibilidad del condón para prestar el servicio y ligadura de trompas como método diferente de planificación, se asociaron estadísticamente con el uso del condón. Sin embargo al ajustar las variables solo la edad y la disponibilidad del condón se mantuvieron como variables explicativas. Cabe anotar, que aunque el modelo mostró buena capacidad predictiva (84,6%), la precisión en sus estimaciones fue baja debido a la poca frecuencia del no uso del condón con el ultimo cliente (3,5%), y la sensibilidad del modelo apenas fue del 33,3%. Por otro lado, factores como la edad, el estrato socioeconómico, nivel educativo, ingreso económico, sitio de oferta del servicio, composición familiar, número de hijos, número de clientes atendidos en la última semana y número de clientes antiguos mostraron asociación estadística con el consumo de alcohol. Sin embargo, al ajustar las variables solo edad, estrato socioeconómico, sitio donde se ofrece el servicio y número de clientes por semana mantuvieron asociación estadística; observándose además que el estrato socioeconómico (uno y dos) y sitio donde se ofrece el servicio (establecimiento), son factores de riesgo para el consumo de alcohol en ejercicio de la ocupación y la poca edad y un número reducido de clientes por semana se comportan como factores de protección para el consumo de alcohol. El modelo predictivo que se desarrolló para la conducta de riesgo de consumo de alcohol, con una sensibilidad del 71,8% y un poder predictivo del 86,4%. .
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We analysed the main geographical trends of terrestrial mammal species richness (SR) in Argentina, assessing how broad-scale environmental variation (defined by climatic and topographic variables) and the spatial form of the country (defined by spatial filters based on spatial eigenvector mapping (SEVM)) influence the kinds and the numbers of mammal species along these geographical trends. We also evaluated if there are pure geographical trends not accounted for by the environmental or spatial factors. The environmental variables and spatial filters that simultaneously correlated with the geographical variables and SR were considered potential causes of the geographic trends. We performed partial correlations between SR and the geographical variables, maintaining the selected explanatory variables statistically constant, to determine if SR was fully explained by them or if a significant residual geographic pattern remained. All groups and subgroups presented a latitudinal gradient not attributable to the spatial form of the country. Most of these trends were not explained by climate.We used a variation partitioning procedure to quantify the pure geographic trend (PGT) that remained unaccounted for. The PGT was larger for latitudinal than for longitudinal gradients. This suggests that historical or purely geographical causes may also be relevant drivers of these geographical gradients in mammal diversity.
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Modifications in vegetation cover can have an impact on the climate through changes in biogeochemical and biogeophysical processes. In this paper, the tree canopy cover percentage of a savannah-like ecosystem (montado/dehesa) was estimated at Landsat pixel level for 2011, and the role of different canopy cover percentages on land surface albedo (LSA) and land surface temperature (LST) were analysed. A modelling procedure using a SGB machine-learning algorithm and Landsat 5-TM spectral bands and derived vegetation indices as explanatory variables, showed that the estimation of montado canopy cover was obtained with good agreement (R2 = 78.4%). Overall, montado canopy cover estimations showed that low canopy cover class (MT_1) is the most representative with 50.63% of total montado area. MODIS LSA and LST products were used to investigate the magnitude of differences in mean annual LSA and LST values between contrasting montado canopy cover percentages. As a result, it was found a significant statistical relationship between montado canopy cover percentage and mean annual surface albedo (R2 = 0.866, p < 0.001) and surface temperature (R2 = 0.942, p < 0.001). The comparisons between the four contrasting montado canopy cover classes showed marked differences in LSA (χ2 = 192.17, df = 3, p < 0.001) and LST (χ2 = 318.18, df = 3, p < 0.001). The highest montado canopy cover percentage (MT_4) generally had lower albedo than lowest canopy cover class, presenting a difference of −11.2% in mean annual albedo values. It was also showed that MT_4 and MT_3 are the cooler canopy cover classes, and MT_2 and MT_1 the warmer, where MT_1 class had a difference of 3.42 °C compared with MT_4 class. Overall, this research highlighted the role that potential changes in montado canopy cover may play in local land surface albedo and temperature variations, as an increase in these two biogeophysical parameters may potentially bring about, in the long term, local/regional climatic changes moving towards greater aridity.
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Studies have demonstrated that public policies to support private firms’ investment have the ability to promote entrepreneurship, but the sustainability of subsidized firms has not often been analysed. This paper aims to examine this dimension specifically through evaluating the mortality of subsidized firms in the long-term. The analysis focuses on a case study of the LEADER+ Programme in the Alentejo region of Portugal. With this purpose, the paper examines the activity status (active or not active) of 154 private, rural, for-profit firms in Alentejo that had received a subsidy to support investment between 2002 and 2008 under the LEADER+ Programme. The methodology is based on binary choice models in order to study the probability of these firms still being active. The explanatory variables used are the following: (1) the characteristics of entrepreneurs and managers’ strategic decisions, (2) firm profile and characteristics, (3) regional economic environment. Data assessment showed that the cumulative mortality rate of firms on 31st December 2013 is over 20 %. Interpretation of the regression model revealed that he probability of firms’ survival increases with higher investment, firm age and regional business concentration, whereas the number of applications made by firms has a negative impact on their survival. So it seems that for subsidized firms the amount of investment is as important as its frequency.
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Public policies to support entrepreneurship and innovation play a vital role when firms have difficulties in accessing external finance. However, some authors have found evidence of long-term inefficiency in subsidized firms (Bernini and Pelligrini, 2011; Cerqua and Pelligrini, 2014) and ineffectiveness of public funds (Jorge and Suárez, 2011). The aim of the paper is to assess the effectiveness in the selection process of applications to public financial support for stimulating innovation. Using a binary choice model, we investigate which factors influence the probability of obtaining public support for an innovative investment. The explanatory variables are connected to firm profile, the characteristics of the project and the macroeconomic environment. The analysis is based on the case study of the Portuguese Innovation.Incentive System (PIIS) and on the applications managed by the Alentejo Regional Operational Program in the period 2007 – 2013. The results show that the selection process is more focused on the expected impact of the project than on the firm’s past performance. Factors that influence the credit risk and the decision to grant a bank loan do not seem to influence the government evaluator regarding the funding of some projects. Past activities in R&D do not significantly affect the probability of having an application approved under the PIIS, whereas an increase in the number of patents and the number of skilled jobs are both relevant factors. Nevertheless, some evidence of firms’ short-term inefficiency was found, in that receiving public financial support is linked to a smaller increase in productivity compared to non-approved firm applications. At the macroeconomic level, periods with a higher cost of capital in financial markets are linked to a greater probability of getting an application for public support approved, which could be associated with the effectiveness of public support in correcting market failings.
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Os recursos humanos são considerados o ativo mais poderoso e valioso de qualquer organização, mas o seu desempenho é, de uma forma geral, influenciado pela motivação e satisfação no trabalho. Deste modo, a presente investigação pretende analisar a motivação e a satisfação dos colaboradores numa organização do sector da formação profissional. A partir deste pressuposto, pretende-se analisar a motivação e a satisfação dos colaboradores da instituição alvo do estudo, averiguar se se verifica correlação entre as vaiáveis motivacionais (sucesso, afiliação e poder) e as variáveis de satisfação (salário, promoções, colegas de trabalho, superiores hierárquicos e realização da tarefa), analisar o relacionamento entre a variável dependente (satisfação com o salário) e variáveis independentes de natureza sociodemográfica e analisar se a motivação e a satisfação global dos colaboradores são influenciadas pelas variáveis explicativas da análise fatorial de componentes principais. A análise dos dados baseou-se em 72 inquéritos por questionário que foram já validados por autores da motivação (McClelland) e satisfação (Deshpande), aplicados à totalidade dos colaboradores da empresa, ou seja, à população em estudo. Procedeu-se à análise estatística para sustentar toda a parte empírica. Os resultados mostram que os colaboradores da empresa Competir se sentem razoavelmente motivados e satisfeitos, ainda que um pouco mais motivados do que satisfeitos. Concluiu-se que, na generalidade, os colaboradores se sentem motivados essencialmente no que diz respeito ao sucesso e afiliação, e satisfeitos principalmente com os seus colegas de trabalho e com a realização da tarefa. A satisfação com o salário é mais baixa no caso de género feminino, mas tende a aumentar com a antiguidade na empresa; Motivation and Job Satisfaction: An Application in an organization of vocational training sector Abstract: Human resources are considered the most powerful and valuable asset in any organization, but its performance is, in general, influenced by motivation and job satisfaction. The present research intends to analyse the motivation and the satisfaction of the employees in an organization of vocational training sector. Based on this assumption, we intend to analyze the motivation and satisfaction of the employees of the studied institution, to verify if there is a correlation between motivational (success, affiliation and power) and satisfaction variables (salary, promotions, Work, hierarchical superiors and task accomplishment), to analyze the relationship between the dependent variable (satisfaction with the salary) and independent variables of a sociodemographic nature and to analyze if the motivation and the overall satisfaction of the employees are influenced by the explanatory variables of the principal components factorial analysis. Data analysis was based on 72 questionnaire surveys that have already been validated by the authors of motivation (McClelland) and satisfaction (Deshpande), applied to all the company's employees, i.e., the study population. In order to support all the empirical part, were proceeded to the statistical analysis. The results shows that the employees of the company Competir feel reasonably motivated and satisfied, even if a little more motivated than satisfied. It was concluded that, in general, employees feel motivated primarily with regard to success and affiliation, and especially satisfied with their co-workers and with the complete of the task. Satisfaction with salary it’s lower in the case of female gender, but tends to increase with seniority in the company.
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Los incendios forestales constituyen problemas que ocasionan grandes daños ambientales sobre los ecosistemas, uno de los mayores impactos en el ambiente son los efectos sobre el cambio climático, situación que acentúa los problemas globales que atentan la vida sobre el planeta. Notoriamente, se reconoce que los incendios son un agente constante de cambios sobre los paisajes naturales y por tanto su estudio reviste importancia, ya que afectan de una manera notable la vegetación, la fauna, el suelo y aumentan el peligro de desertificación, lo que conlleva a los problemas socioeconómicos. Este artículo tiene por objetivo determinar el riesgo ante incendios forestales en la cuenca del Río Tempisque en Costa Rica, a partir de variables explicativas como la proximidad a carreteras, tipos de usos de la tierra, focos de incendios, insolación y altitud sobre el nivel de mar, modeladas con técnicas de Evaluación Multicriterio (ECM) en un Sistema de Información Geográfica (SIG).Dado que el concepto riesgo se refiere a una condición de probabilidad, en este artículo se recrea escenarios en donde podría tener lugar el fuego, los cuales se correlacionan con eventos que se han presentando en años anteriores. Se debe advertir que no se considera la variable viento como factor dispersor del fuego, ya que el objetivo es determinar lugares con condición favorable a incendio sin mediar los factores que contribuyen en su distribución.Palabras claves: incendio forestal, problema ambiental, riesgo, modelaje, sistemas de información geográfica y evaluación multicriterio.AbstractForest fires are problems that cause environmental damage to ecosystems. One of the biggest impacts is on the atmosphere and their effects on climatic change, a situation that exacerbates globalproblems perpetrated on planet life. Historically, fires are recognized as a constant agent of change Julio César Moraga Peralta Evaluación del riesgo ante incendios forestalesen la cuenca del río Tempisque, Costa Rica on the natural landscape. Therefore, fire studies are important because of the significant effect of fire on vegetation, fauna and soils and the increased danger of desertification, leading to socioeconomicproblems.This article has as its objective to determine the risk before forest fires on the Tempisque RiverBasin in Costa Rica from explanatory variables such as proximity to roads, types of land uses, fireoutbreaks, isolation and altitude above sea level, using Multicriteria Evaluation (NDE) modeling techniques in a Geographic Information System.As the term risk refers to a condition of probability, this article recreates scenarios where a fire could occur, which correlate with events that have occurred in previous years. It should be noted that the variable of wind is not considered as a fire-scattering factor since the objective of this study is to identify places with conditions already favorable to fires without a contributing factor in their distribution.Key words: forest fire, environmental problems, risk, geographical information system, multicriteria evaluation modeling, Tempisque River Basin, Costa Rica
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Se presenta un análisis de los posibles factores explicativos del crecimiento urbano en la Comunidad de Madrid durante el período 1990-2000, incluyendo la zonificación de la región en relación a las coronas metropolitanas en torno a la ciudad de Madrid. Se analizan las categorías estructura urbana laxa, urbanizaciones exentas y zonas industriales y comerciales establecidas en la cartografía de usos del suelo Corine Land Cover. Como factores explicativos del cambio se tomaron variables socioeconómicas, biofísicas, de planificación legal, políticas y de proximidad/accesibilidad, medidas en cada píxel del territorio. El análisis de la relación entre las variables explicativas y el crecimiento urbano se llevó a cabo a través de la regresión logística. Los resultados obtenidos del ajuste de los modelos mostró la relevancia de algunas variables en la explicación de la localización del crecimiento de las categorías urbanas analizadas.Palabras Clave: crecimiento urbano, variables explicativas, regresión logística, Corine Land Cover,MadridABSTRACTThis paper presents an analysis of the possible explanatory factors of urban growth in Madrid, Spain during the period 1990-2000, including the zoning of the region in relation to the metropolitan area around the city. Specifically, two categories were analyzed: residential discontinuous urban andresidential discontinuous sparse urban, and commercial and industrial of the Corine Land Cover. Previous analysis of Corine Land Cover land use change identified these categories as having the largest growth during the study period. Socio-economic, biophysical, legal planning, policies andproximity/accessibility variables were taken into account as explanatory factors of urban growth, at pixel level. Logistic regression was used to analyze the relationship between explanatory variables and urban growth. The results obtained from the model adjustments showed the relevance of somevariables in explaining the location of urban growth in the categories analyzed.Keyword: GIS, urban growth, explanatory factors, logistic regression, Corine Land Cover, Madrid,Spain
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In recent years, several explanatory models have been developed which attempt to analyse the predictive worth of various factors in relation to academic achievement, as well as the direct and indirect effects that they produce. The aim of this study was to examine a structural model incorporating various cognitive and motivational variables which influence student achievement in the two basic core skills in the Spanish curriculum: Spanish Language and Mathematics. These variables included differential aptitudes, specific self-concept, goal orientations, effort and learning strategies. The sample comprised 341 Spanish students in their first year of Compulsory Secondary Education. Various tests and questionnaires were used to assess each student, and Structural Equation Modelling (SEM) was employed to study the relationships in the initial model. The proposed model obtained a satisfactory fit for the two subjects studied, and all the relationships hypothesised were significant. The variable with the most explanatory power regarding academic achievement was mathematical and verbal aptitude. Also notable was the direct influence of specific self-concept on achievement, goal-orientation and effort, as was the mediatory effect that effort and learning strategies had between academic goals and final achievement.
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Landscape is an example of a non-market good where no metrics exist to measure its quality. The paper proposes an original methodology to nevertheless estimate scope variables in those circumstances, allowing then to better test if people's willingnesstopay for such good is sensitive to the scope. The methodology is based on techniques developed in the context of multicriteria decision analysis. It is applied to assess the quality of the landscape of several Swiss alpine resorts. This assessment is then used as an explanatory variable in a hedonic price function to explain the rent of apartments and to derive an implicit price of the landscape quality.
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The objective of this work was to perform a quantitative analysis of the amino acid composition of soybean seeds as affected by climatic variables during seed filling. Amino acids were determined from seed samples taken at harvest in 31 multi-environment field trials carried out in Argentina. Total amino acids ranged from 31.69 to 49.14%, and total essential and nonessential amino acids varied from 12.83 to 19.02% and from 18.86 to 31.15%, respectively. Variance components expressed as the percentage of total variation showed that the environment was the most important source of variation for all traits, followed by the genotype x environment interaction. Significant explanatory linear regressions were detected for amino acid content regarding: average daily mean air temperature and cumulative solar radiation, during seed filling; precipitation minus potential evapotranspiration, during the whole reproductive period; and the combinations of these climatic variables. Each amino acid behaves differently according to environmental conditions, indicating compensatory effects among them.
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In soccer, dead-ball moves are those in which the ball is returned to play from a stationary position following an interruption of play. The aim of this study was to analyse the effectiveness of one such dead-ball move, namely corner kicks, and to identify the key variables that determine the success of a shot or header following a corner, thereby enabling a model of successful corner kicks to be proposed. We recorded 554 corner kicks performed during the 2010 World Cup in South Africa and carried out a univariate, bivariate and multivariate analysis of the data. The results indicated that corners were of limited effectiveness in terms of the success of subsequent shots or headers. The analysis also revealed a series of variables that were significantly related to one another, and this enabled us to propose an explanatory model. Although this model had limited explanatory power, it nonetheless helps to understand the execution of corner kicks in practical terms.
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