820 resultados para Scarcity of available alternatives
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Les organismes aquatiques sont adaptés à une grande variabilité hydrique et thermique des rivières. Malgré ceci, la régulation des eaux suscite des changements aux débits qui peuvent provoquer des impacts négatifs sur la biodiversité et les processus écologiques en rivière. Celle-ci peut aussi causer des modifications au niveau des régimes thermiques et des caractéristiques de l’habitat du poisson. Des données environnementales et biologiques décrivant l’habitat du poisson existent, mais elles sont incomplètes pour plusieurs rivières au Canada et de faible qualité, limitant les relations quantitatives débit-température-poissons à un petit nombre de rivières ou à une région étudiée. La recherche menée dans le cadre de mon doctorat concerne les impacts de la génération d'hydroélectricité sur les rivières; soit les changements aux régimes hydriques et thermiques reliés à la régulation des eaux sur la variation des communautés ichtyologiques qui habitent les rivières régulées et naturelles au Canada. Suite à une comparaison d’échantillonnage de pêche, une méthode constante pour obtenir des bons estimés de poisson (richesse, densité et biomasse des espèces) a été établie pour évaluer la structure de la communauté de poissons pour l’ensemble des rivières ciblées par l’étude. Afin de mieux comprendre ces changements environnementaux, les principales composantes décrivant ces régimes ont été identifiées et l’altération des régimes hydriques pour certaines rivières régulées a été quantifiée. Ces résultats ont servi à établir la relation significative entre le degré de changement biotique et le degré de changement hydrique pour illustrer les différences entre les régimes de régulation. Pour faire un complément aux indices biotiques déjà calculés pour l’ensemble des communautés de poissons (diversité, densité et biomasse des espèces par rivière), les différences au niveau des guildes de poissons ont été quantifiées pour expliquer les divers effets écologiques dus aux changements de régimes hydriques et thermiques provenant de la gestion des barrages. Ces derniers résultats servent à prédire pour quels traits écologiques ou groupes d’espèces de poissons les composantes hydriques et thermiques sont importantes. De plus, ces derniers résultats ont servi à mettre en valeur les variables décrivant les régimes thermiques qui ne sont pas toujours inclues dans les études hydro-écologiques. L’ensemble des résultats de cette thèse ont des retombées importantes sur la gestion des rivières en évaluant, de façon cohérente, l’impact de la régulation des rivières sur les communautés de poissons et en développant des outils de prévision pour la restauration des écosystèmes riverains.
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Background: Cholera, a severe acute watery diarrhea caused by Vibrio cholerae is endemic in Nigeria with most cases occurring in the rural areas. In South West Nigeria, some individuals resort to alternative treatments such as Ogi-tutu, Psidium guajava and Vernonia amygdalina during infections. The effectiveness of these alternatives in the prevention and treatment of V. cholerae infection requires experimental investigation. Objective: This study was designed to investigate the ameliorative effects of Ogi-tutu, Vernonia amygdalina and Psidium guajava on intestinal histopathology of experimental mice infected with V. cholerae. Methods: Preliminary investigation of in vitro vibriocidal activities of these alternatives were carried out using agar cup diffusion assay. For ameliorative effects, adult mice were inoculated with 100 μl (106 cells) of Vibrio cholerae and dosed at 0 h (immediate prevention) and 4 h (treatment of infection) and their intestines were histopathologically evaluated. Results: The histopathological changes were the same irrespective of the treated groups, but the lesions varied in extent and severity. The ameliorative effects in decreasing order were V. amygdalina > P. guajava > Ogi-tutu. Conclusion: V. amygdalina gave the best ameliorative effects in the prevention and treatment of V. cholerae infection.
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This paper presents a harmonised framework of sediment quality assessment and dredging material characterisation for estuaries and port zones of North and South Atlantic. This framework, based on the weight-of-evidence approach, provides a structure and a process for conducting sediment/dredging material assessment that leads to a decision. The main structure consists of step 1 (examination of available data); step 2 (chemical characterisation and toxicity assessment); decision 1 (any chemical level higher than reference values? are sediments toxic?); step 3 (assessment of benthic community structure); step 4 (integration of the results); decision 2 (are sediments toxic or benthic community impaired?); step 5 (construction of the decision matrix) and decision 3 (is there environmental risk?). The sequence of assessments may be interrupted when the information obtained is judged to be sufficient for a correct characterisation of the risk posed by the sediments/dredging material. This framework brought novel features compared to other sediment/dredging material risk assessment frameworks: data integration through multivariate analysis allows the identification of which samples are toxic and/or related to impaired benthic communities; it also discriminates the chemicals responsible for negative biological effects; and the framework dispenses the use of a reference area. We demonstrated the successful application of this framework in different port and estuarine zones of the North (Gulf of Cadiz) and South Atlantic (Santos and Paranagua Estuarine Systems).
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This research consists in studying the influence of the various type of construction systems of roofs with their energy efficiency as well as on the cost benefit for the commercial buildings on the temperatures condition of the city of Natal/RN. The main goal of this research is to analyze the cost benefit of the construction systems of roofs available on the market, taking into consideration the energy efficiency of the commercial buildings artificially air conditioned in order to be used by the projectors and to be adequated to the temperatures condition of the city of Natal/RN. The method of valuation of the cost benefit of roof systems consists in six steps: Features and simulation of the reference building; Analyze of sensitivity; Analyzes, features and simulation of alternatives of roof construction systems; Analyze of the cost of implementation; Analyze of the benefits of the alternatives comparing to the base case; And finally the analyze of the cost benefit. The model type chosen as reference was stores with pre molded buildings and system of roof with fiber ciment and ceiling . The thermal results showed the influence of the roof system on the energy efficiency of the building. The Final results of the simulations of the alternatives comes to a conclusion that the absortance is the variable that presents the best cost benefit relation and the reduction on the thermal transmittance still has limitations because of the high cost
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Dissertação de Mestrado, Qualidade em Análises - Erasmus Mundus, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2015
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This talk addresses the scarcity of critical material on Hilary Mantel’s writing in the academy. It questions the suitability of the ‘origin’ paradigm within the criticism that is available, which closes off the excess of Mantel’s texts through attempts to ‘unite’ her corpus. The ambiguity of her writing, and its suspicions, suggest Jacques Derrida’s thought as a pertinent means to read the differences in her work differently. The proximity of Jean-Luc Nancy’s philosophy with Derrida’s thought allows the significance of ellipsis to surface as a liberating catalyst for weaving the implications of Derrida’s thinking through the writing of Mantel. This synthesis constitutes an original combination because Mantel’s writing has not been closely studied, Derrida’s notion of ellipsis has been eclipsed by philosophy, and the combination of these two ‘invisibilities’ is seminal. The talk begins with an exploration of the mythologies I discovered and interrogated during the course of my thesis. It then considers the key points in Mantel’s writing career. In particular taking her from the difficulty and invisibility of 1979 when A Place of Greater Safety, her first novel, was rejected, to winning the Booker prize twice in succession in 2009 and 2012. It thereby traces the story of her shift from invisible to infamous, in terms of her treatment by the mainstream British media as well as her phenomenal post-millennium success.
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Abstract During the last few decades, there has been an increasing international recognition of the studies related to the analysis of the family models change, the focus being the determinants of the female employment and the problems related to the work family balance (Lewis, 2001; Petit & Hook, 2005Saraceno, Crompton & Lyonette, 20062008; Pfau-Effinger, 2012). The majority of these studies have been focused on the analysis of the work-family balance problems as well as the effectiveness of the family and gender policies in order to encourage female employment (Korpi et al., 2013). In Spain, special attention has been given to the family policies implemented, the employability of women and on the role of the father in the family (Flaquer et al., 2015; Meil, 2015); however, there has been far less emphasis on the analysis of the family cultural models (González and Jurado, 2012; Crespi and Moreno, 2016). The purpose of this paper is to present some of the first results on the influence of the socio-demographic factors on the expectations and attitudes about the family models. This study offers an analytical reflection upon the foundation of the determinants of the family ambivalence in Spain from the cultural and the institutional dimension. This study shows the Spanish family models of preferences following the Pfau-Effinger (2004) classification of the famiy living arrangements. The reason for this study is twofold; on the one hand, there is confirmed the scarcity of studies that have focused their attention on this objective in Spain; on the other hand, the studies carried out in the international context have confirmed the analytical effectiveness of researching on the attitude and value changes to explain the meaning and trends of the family changes. There is also presented some preliminary results that have been obtained from the multinomial analysis related to the influence of the socio-demographic factors on the family model chosen by the individuals in Spain (father and mother working full time; mother part-time father full-time; mother not at work father full-time; mother and father part-time). 3 The database used has been the International Social Survey Programme: Family and Changing Gender Roles IV- ISSP 2012-. Spain is the only country of South Europe that has participated in the survey. For this reason it has been considered as a representative case study.
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This paper explores the changing role of contemporary grandparents with many demonstrating a willingness and ability to take on parental responsibilities for their grandchildren, where they may face challenges and opportunities in difficult times. Three main forms of grand parenting are identified in the literature, those who hâve primary responsibility and are raising their grand children as their main carers perhaps in response to crisis situations, those who live in extended families and participate in care, and those who provide day care while the child's parents work. The rôle of Grandparents encompasses ail three areas in the United Kingdom. This has occurred as a resuit of the increased récognition of children living in abusive families, of the increasing frequency of divorce, single parenting, children and families living in poverty, socio-economic deprivation and the lack of available or subsidised child care in the United Kingdom when parents hâve to work to support the family. Ail of this against the backdrop the Every Child Matters change for children Agenda. When grandparents step into a troubled situation and attempt to offer stability and security for their grandchildren they may hâve to manage the combined responsibilities of family caregivers and parental figures. Grandparenthood is atenuous rôle, lacking clear agreement on behaviour norms. In the current culture of advice and parenting support, while care must be taken not to undermine parenting skills or make judgements about the ability to cope with the demands of childcare, an exploration of the impact on grandparents, and children in the context of families must be undertaken. Due to the complex web of interrelated factors the process and outcomes of care giving by grandparents is not well known in the literature. It is proposed therefore that it is timely to explore the impact of this on the health of children and their families in the current climate of change when there has been dissolution of the nuclear family and grandparents are playing increasingly significant rôles in healing and supporting their families.
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The main objective for physics based modeling of the power converter components is to design the whole converter with respect to physical and operational constraints. Therefore, all the elements and components of the energy conversion system are modeled numerically and combined together to achieve the whole system behavioral model. Previously proposed high frequency (HF) models of power converters are based on circuit models that are only related to the parasitic inner parameters of the power devices and the connections between the components. This dissertation aims to obtain appropriate physics-based models for power conversion systems, which not only can represent the steady state behavior of the components, but also can predict their high frequency characteristics. The developed physics-based model would represent the physical device with a high level of accuracy in predicting its operating condition. The proposed physics-based model enables us to accurately develop components such as; effective EMI filters, switching algorithms and circuit topologies [7]. One of the applications of the developed modeling technique is design of new sets of topologies for high-frequency, high efficiency converters for variable speed drives. The main advantage of the modeling method, presented in this dissertation, is the practical design of an inverter for high power applications with the ability to overcome the blocking voltage limitations of available power semiconductor devices. Another advantage is selection of the best matching topology with inherent reduction of switching losses which can be utilized to improve the overall efficiency. The physics-based modeling approach, in this dissertation, makes it possible to design any power electronic conversion system to meet electromagnetic standards and design constraints. This includes physical characteristics such as; decreasing the size and weight of the package, optimized interactions with the neighboring components and higher power density. In addition, the electromagnetic behaviors and signatures can be evaluated including the study of conducted and radiated EMI interactions in addition to the design of attenuation measures and enclosures.
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Concrete substructures are often subjected to environmental deterioration, such as sulfate and acid attack, which leads to severe damage and causes structure degradation or even failure. In order to improve the durability of concrete, the High Performance Concrete (HPC) has become widely used by partially replacing cement with pozzolanic materials. However, HPC degradation mechanisms in sulfate and acidic environments are not completely understood. It is therefore important to evaluate the performance of the HPC in such conditions and predict concrete service life by establishing degradation models. This study began with a review of available environmental data in the State of Florida. A total of seven bridges have been inspected. Concrete cores were taken from these bridge piles and were subjected for microstructural analysis using Scanning Electron Microscope (SEM). Ettringite is found to be the products of sulfate attack in sulfate and acidic condition. In order to quantitatively analyze concrete deterioration level, an image processing program is designed using Matlab to obtain quantitative data. Crack percentage (Acrack/Asurface) is used to evaluate concrete deterioration. Thereafter, correlation analysis was performed to find the correlation between five related variables and concrete deterioration. Environmental sulfate concentration and bridge age were found to be positively correlated, while environmental pH level was found to be negatively correlated. Besides environmental conditions, concrete property factor was also included in the equation. It was derived from laboratory testing data. Experimental tests were carried out implementing accelerated expansion test under controlled environment. Specimens of eight different mix designs were prepared. The effect of pozzolanic replacement rate was taken into consideration in the empirical equation. And the empirical equation was validated with existing bridges. Results show that the proposed equations compared well with field test results with a maximum deviation of ± 20%. Two examples showing how to use the proposed equations are provided to guide the practical implementation. In conclusion, the proposed approach of relating microcracks to deterioration is a better method than existing diffusion and sorption models since sulfate attack cause cracking in concrete. Imaging technique provided in this study can also be used to quantitatively analyze concrete samples.
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Among people living with HIV (PLWH), adherence to antiretroviral therapy (ART) can be affected by problems of neurocognitive (NC) impairment, stress, alcohol and other drug (AOD) abuse, and other barriers. The aims of this research were to: (1) examine factors associated with NC impairment, (2) explore relationships between psychosocial variables with ART adherence and viral load (VL), and (3) evaluate the efficacy of an evidence-based intervention in improving ART adherence, increasing service utilization, and decreasing VL. The first study (n=370) was cross sectional and used structural equation modeling to test whether AOD use, years living with HIV, and time from HIV diagnosis to seeking care were associated with poorer NC functioning. The second study (n=246) used similar methods to test the hypothesis that stress, barriers to adherence, NC impairment, poor social support, and AOD use were related to lower VL mediated by ART adherence. The third study (n=243) evaluated an evidence-based, eight-session program to improve ART adherence, reduce VL, and increase service utilization in a randomized controlled trial. Study participants were PLWH living in South Florida, 18 to 60 years old, with a history of alcohol abuse enrolled from January 2009 through November 2012. Secondary analysis of available data showed: (1) scores on interference with executive functioning increased by 0.32 for each day of marijuana use and 1.18 for each year living with HIV, but no association was found between alcohol use and NC functioning; (2) each barrier to adherence was associated with a 10% decrease in adherence to ART and a 0.42 unit increase in VL (log10) and the relationship between barriers and VL was partially mediated by ART adherence; (3) participants in the evidence-based program were more likely than the comparison group to report an undetectable VL (OR=2.25, p Psychosocial factors affect VL, but ART adherence is essential in achieving an undetectable VL in PLWH.
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BACKGROUND Integrons are found in hundreds of environmental bacterial species, but are mainly known as the agents responsible for the capture and spread of antibiotic-resistance determinants between Gram-negative pathogens. The SOS response is a regulatory network under control of the repressor protein LexA targeted at addressing DNA damage, thus promoting genetic variation in times of stress. We recently reported a direct link between the SOS response and the expression of integron integrases in Vibrio cholerae and a plasmid-borne class 1 mobile integron. SOS regulation enhances cassette swapping and capture in stressful conditions, while freezing the integron in steady environments. We conducted a systematic study of available integron integrase promoter sequences to analyze the extent of this relationship across the Bacteria domain. RESULTS Our results showed that LexA controls the expression of a large fraction of integron integrases by binding to Escherichia coli-like LexA binding sites. In addition, the results provide experimental validation of LexA control of the integrase gene for another Vibrio chromosomal integron and for a multiresistance plasmid harboring two integrons. There was a significant correlation between lack of LexA control and predicted inactivation of integrase genes, even though experimental evidence also indicates that LexA regulation may be lost to enhance expression of integron cassettes. CONCLUSIONS Ancestral-state reconstruction on an integron integrase phylogeny led us to conclude that the ancestral integron was already regulated by LexA. The data also indicated that SOS regulation has been actively preserved in mobile integrons and large chromosomal integrons, suggesting that unregulated integrase activity is selected against. Nonetheless, additional adaptations have probably arisen to cope with unregulated integrase activity. Identifying them may be fundamental in deciphering the uneven distribution of integrons in the Bacteria domain.
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Outbreaks of fibropapillomatosis (FP), a neoplastic infectious disease of marine turtles, have occurred worldwide since the 1980s. Its most likely aetiological agent is a virus, but disease expression depends on external factors, typically associated with altered environments. The scarcity of robust long-term data on disease prevalence has limited interpretations on the impacts of FP on turtle populations. Here we model the dynamics of FP at 2 green turtle foraging aggregations in Puerto Rico, through 18 yr of capture-mark-recapture data (1997−2014). We observed spatiotemporal variation in FP prevalence, potentially modulated via individual site-fidelity. FP ex pression was residency dependent, and FP-free individuals developed tumours after 1.8 ± 0.8 yr (mean ± SD) in the infected area. Recovery from the disease was likely, with complete tumour regression occurring in 2.7 ± 0.7 yr (mean ± SD). FP does not currently seem to be a major threat to marine turtle populations; however, disease prevalence is yet unknown in many areas. Systematic monitoring is highly advisable as human-induced stressors can lead to deviations in host− pathogen relationships and disease virulence. Finally, data collection should be standardized for a global assessment of FP dynamics and impacts.
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Power flow calculations are one of the most important tools for power system planning and operation. The need to account for uncertainties when performing power flow studies led, among others methods, to the development of the fuzzy power flow (FPF). This kind of models is especially interesting when a scarcity of information exists, which is a common situation in liberalized power systems (where generation and commercialization of electricity are market activities). In this framework, the symmetric/constrained fuzzy power flow (SFPF/CFPF) was proposed in order to avoid some of the problems of the original FPF model. The SFPF/CFPF models are suitable to quantify the adequacy of transmission network to satisfy “reasonable demands for the transmission of electricity” as defined, for instance, in the European Directive 2009/72/EC. In this work it is illustrated how the SFPF/CFPF may be used to evaluate the impact on the adequacy of a transmission system originated by specific investments on new network elements
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Lithium Ion (Li-Ion) batteries have got attention in recent decades because of their undisputable advantages over other types of batteries. They are used in so many our devices which we need in our daily life such as cell phones, lap top computers, cameras, and so many electronic devices. They also are being used in smart grids technology, stand-alone wind and solar systems, Hybrid Electric Vehicles (HEV), and Plug in Hybrid Electric Vehicles (PHEV). Despite the rapid increase in the use of Lit-ion batteries, the existence of limited battery models also inadequate and very complex models developed by chemists is the lack of useful models a significant matter. A battery management system (BMS) aims to optimize the use of the battery, making the whole system more reliable, durable and cost effective. Perhaps the most important function of the BMS is to provide an estimate of the State of Charge (SOC). SOC is the ratio of available ampere-hour (Ah) in the battery to the total Ah of a fully charged battery. The Open Circuit Voltage (OCV) of a fully relaxed battery has an approximate one-to-one relationship with the SOC. Therefore, if this voltage is known, the SOC can be found. However, the relaxed OCV can only be measured when the battery is relaxed and the internal battery chemistry has reached equilibrium. This thesis focuses on Li-ion battery cell modelling and SOC estimation. In particular, the thesis, introduces a simple but comprehensive model for the battery and a novel on-line, accurate and fast SOC estimation algorithm for the primary purpose of use in electric and hybrid-electric vehicles, and microgrid systems. The thesis aims to (i) form a baseline characterization for dynamic modeling; (ii) provide a tool for use in state-of-charge estimation. The proposed modelling and SOC estimation schemes are validated through comprehensive simulation and experimental results.