973 resultados para Urban problems
Resumo:
Two trends which presently exist in relation to the concept of Paleontology are analyzed, pointing out some of the aspects which negative influence. Various reflections are made based on examples of some of the principal points of paleontological method, such as the influence of a punctual sampling, the meaning of size-frequency distribution and subjectivity in the identification of fossils. Topics which have a marked repercussion in diverse aspects of Paleontology are discussed.
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The historically-reactive approach to identifying safety problems and mitigating them involves selecting black spots or hot spots by ranking locations based on crash frequency and severity. The approach focuses mainly on the corridor level without taking the exposure rate (vehicle miles traveled) and socio-demographics information of the study area, which are very important in the transportation planning process, into consideration. A larger study analysis unit at the Transportation Analysis Zone (TAZ) level or the network planning level should be used to address the needs of development of the community in the future and incorporate safety into the long-range transportation planning process. In this study, existing planning tools (such as the PLANSAFE models presented in NCHRP Report 546) were evaluated for forecasting safety in small and medium-sized communities, particularly as related to changes in socio-demographics characteristics, traffic demand, road network, and countermeasures. The research also evaluated the applicability of the Empirical Bayes (EB) method to network-level analysis. In addition, application of the United States Road Assessment Program (usRAP) protocols at the local urban road network level was investigated. This research evaluated the applicability of these three methods for the City of Ames, Iowa. The outcome of this research is a systematic process and framework for considering road safety issues explicitly in the small and medium-sized community transportation planning process and for quantifying the safety impacts of new developments and policy programs. More specifically, quantitative safety may be incorporated into the planning process, through effective visualization and increased awareness of safety issues (usRAP), the identification of high-risk locations with potential for improvement, (usRAP maps and EB), countermeasures for high-risk locations (EB before and after study and PLANSAFE), and socio-economic and demographic induced changes at the planning-level (PLANSAFE).
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In urban communities, there are often limited amounts of right-of-way available for establishing a large setback distance from the curb for fixed objects. Urban communities must constantly weigh the cost of purchasing additional right-of-way for clear zones against the risk of fixed object crashes. From 2004 to 2006, this type of crash on curbed roads represented 15% of all fatal crashes and 3% of all crashes in the state of Iowa. Many states have kept the current minimum AASHTO recommendations as their minimum clear zone standards; however, other states have decided that these recommendations are insufficient and have increased the required minimum clear zone distance to better suit the judgment of local designers. This report presents research on the effects of the clear zone on urban curbed streets. The research was conducted in two phases. The first phase involved a synthesis of practice that included a literature review and a survey of practices in jurisdictions that have developmental and historical patterns similar to those of Iowa. The second phase involved investigating the benefits of a 10 ft clear zone, which included examining urban corridors in Iowa that meet or do not meet the 10 ft clear zone goal. The results of this study indicate that a consistent fixed object offset results in a reduction in the number of fixed object crashes, a 5 ft clear zone is most effective when the goal is to minimize the number of fixed object c ashes, and a 3 ft clear zone is most effective when the goal is to minimize the cost of fixed object crashes.
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This is an overview of the United States Commission on Civil Rights and the duties of the Iowa State Advisory Committee. It contains a report concerning problems of the Spanish surnamed and migrant population in Iowa.
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With a life expectancy at the age of 65 of around 20 years, damaging health risk behaviours of young-old adults have become a target for preventive actions. Such risk factors necessitate an accurate understanding of the present and past socioeconomic conditions associated with health risk behaviours. The aim of our study is to assess the impact of certain life events as well as economic and environmental factors on health risk behaviours. We included 1309 participants of the Lausanne Cohort Lc65+ aged 65-70 years and employed logistic regression analyses, with individuals nested within areas. The results illustrate the influences of socioeconomic factors from childhood to young-old age. Life experiences in adulthood and economic resources in young-old age are both associated with unfavourable health behaviours. Neighbourhood is a modest determinant as well, particularly regarding alcohol consumption. Therefore, prevention against health risk behaviours should focus on population subgroups defined on the basis of their socioeconomic and living contexts.
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Microbial processes have been used as indicators of soil quality, due to the high sensitivity to small changes in management to evaluate, e.g., the impact of applying organic residues to the soil. In an experiment in a completely randomized factorial design 6 x 13 + 4, (pot without soil and residue or absolute control) the effect of following organic wastes was evaluated: pulp mill sludge, petrochemical complex sludge, municipal sewage sludge, dairy factory sewage sludge, waste from pulp industry and control (soil without organic waste) after 2, 4, 6, 12, 14, 20, 28, 36, 44, 60, 74, 86, and 98 days of incubation on some soil microbial properties, with four replications. The soil microbial activity was highly sensitive to the carbon/nitrogen ratio of the organic wastes. The amount of mineralized carbon was proportional to the quantity of soil-applied carbon. The average carbon dioxide emanating from the soil with pulp mill sludge, corresponding to soil basal respiration, was 0.141 mg C-CO2 100 g-1 soil h-1. This value is 6.4 times higher than in the control, resulting in a significant increase in the metabolic quotient from 0.005 in the control to 0.025 mg C-CO2 g-1 Cmic h-1 in the soil with pulp mill sludge. The metabolic quotient in the other treatments did not differ from the control (p < 0.01), demonstrating that these organic wastes cause no disturbance in the microbial community.
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A haplotype is an m-long binary vector. The XOR-genotype of two haplotypes is the m-vector of their coordinate-wise XOR. We study the following problem: Given a set of XOR-genotypes, reconstruct their haplotypes so that the set of resulting haplotypes can be mapped onto a perfect phylogeny (PP) tree. The question is motivated by studying population evolution in human genetics, and is a variant of the perfect phylogeny haplotyping problem that has received intensive attention recently. Unlike the latter problem, in which the input is "full" genotypes, here we assume less informative input, and so may be more economical to obtain experimentally. Building on ideas of Gusfield, we show how to solve the problem in polynomial time, by a reduction to the graph realization problem. The actual haplotypes are not uniquely determined by that tree they map onto, and the tree itself may or may not be unique. We show that tree uniqueness implies uniquely determined haplotypes, up to inherent degrees of freedom, and give a sufficient condition for the uniqueness. To actually determine the haplotypes given the tree, additional information is necessary. We show that two or three full genotypes suffice to reconstruct all the haplotypes, and present a linear algorithm for identifying those genotypes.
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In Switzerland, the land management regime is characterized by a liberal attitude towards the institution of property rights, which is guaranteed by the Constitution. Under the present Swiss constitutional arrangement, authorities (municipalities) are required to take into account landowners' interests when implementing their spatial planning policy. In other words, the institution of property rights cannot be restricted easily in order to implement zoning plans and planning projects. This situation causes many problems. One of them is the gap between the way land is really used by the landowners and the way land should be used based on zoning plans. In fact, zoning plans only describe how landowners should use their property. There is no sufficient provision for handling cases where the use is not in accordance with zoning plans. In particular, landowners may not be expropriated for a non-conforming use of the land. This situation often leads to the opening of new building areas in greenfields and urban sprawl, which is in contradiction with the goals set into the Federal Law on Spatial Planning. In order to identify legal strategies of intervention to solve the problem, our paper is structured into three main parts. Firstly, we make a short description of the Swiss land management regime. Then, we focus on an innovative land management approach designed to implement zoning plans in accordance with property rights. Finally, we present a case study that shows the usefulness of the presented land management approach in practice. We develop three main results. Firstly, the land management approach brings a mechanism to involve landowners in planning projects. Coordination principle between spatial planning goals and landowners' interests is the cornerstone of all the process. Secondly, the land use is improved both in terms of space and time. Finally, the institution of property rights is not challenged, since there is no expropriation and the market stays free.
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The use of urban waste compost as nutrient source in agriculture has been a subject of investigation in Brazil and elsewhere, although the effects on soil physical and chemical properties and processes are still poorly known. The aim of this study was to evaluate the effect of application of urban waste compost and mineral fertilizer on soil aggregate stability and organic carbon and total nitrogen content of a Rhodic Hapludox under no-tillage in the northwestern region of Rio Grande do Sul, Brazil, in the 2009/2010 and 2010/2011 growing seasons. The experiment was arranged in a 2 × 6 (seasons and fertilization) factorial in a randomized complete block design with four replications. The factor time consisted of two growing seasons (sunflower in 2009/10 and maize in 2010/11) and the factor fertilization of five rates of urban waste compost (0, 25, 50, 75 and 100 m³ ha-1), and mineral fertilizer. Soil samples were collected from the 0.0-0.10 m layer to determine aggregate stability (mean weight and geometric diameter), soil organic carbon (SOC) and total nitrogen (TN). Rates of up to 75 m³ ha-1 of urban waste compost, after two years of application to no-tillage maize and sunflower, improved aggregation compared to mineral fertilization in a Rhodic Hapludox. After the second crop, the SOC and TN contents increased linearly with the levels of urban waste compost.
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Thermal fluctuations around inhomogeneous nonequilibrium steady states of one-dimensional rigid heat conductors are analyzed in the framework of generalized fluctuating hydrodynamics. The effect of an external source of noise is also considered. External fluctuations come from temperature and position fluctuations of the source. Contributions of each kind of noise to the temperature correlation function are computed and compared through the study of its asymptotic behavior.
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Résumé L'objectif de la thèse est de comprendre le mode d'organisation économique spécifique aux petits centres urbains qui composent les espaces frontaliers sahéliens, en s'interrogeant sur leur concurrence ou leur complémentarité éventuelle à l'intérieur d'un régime de spatialité particulier. En s'appuyant sur l'exemple du carrefour économique de Gaya-Malanville-Kamba situé à la frontière entre le Niger, le Bénin et le Nigeria, il questionne le rôle de la ville-frontière ainsi que le jeu des acteurs marchands localement dominants, à partir de quatre grandes interrogations : Quelles sont les spécificités de l'Afrique sahélienne qui obligent à renouveler les approches géographiques de l'espace marchand? Quels sont les facteurs déterminants de l'activité économique frontalière? Les formes d'organisation de l'espace qui concourent à la structuration de l'économie sont-elles concurrentes ou coopératives? Les logiques économiques frontalières sont-elles compatibles avec l'orientation des programmes de développement adoptés par les pays sahéliens et leurs partenaires bi- ou multilatéraux? Dans une première partie, un modèle territorial de l'Afrique sahélienne permet de rendre compte de la prédominance des logiques circulatoires sur les logiques productives, une propriété essentielle de toute organisation économique confrontée à l'instabilité climatique. Dans une seconde partie, l'étude considère les facteurs déterminants de l'activité économique frontalière que sont le degré d'enclavement des territoires, la libre circulation des biens et des personnes, les relations concurrentielles ou coopératives qui lient les marchés ainsi que les liens clientélistes qui unissent patron et obligés. Une troisième partie est consacrée aux productions agricoles de tente organisées sous forme de coopératives paysannes ou d'initiatives privées. Une quatrième partie s'intéresse aux réseaux de l'import-export et du commerce de détail qui bénéficient de l'augmentation des besoins engendrée par l'urbanisation sahélienne. L'économie spatiale qui résulte de ces flux est organisée selon deux logiques distinctes : d'une part, les opportunités relatives à la production agricole conduisent certains investisseurs à intensifier l'irrigation pour satisfaire la demande des marchés urbains, d'autre part, les acteurs du capitalisme marchand, actifs dans l'import-export et la vente de détail, développent des réseaux informels et mobiles qui se jouent des différentiels nationaux. Les activités commerciales des villes-marchés connaissent alors des fluctuations liées aux entreprises productives et circulatoires de ces patrons, lesquelles concourent à l'organisation territoriale générale de l>Afrique sahélienne. Ces logiques évoluent dans un contexte fortement marqué par les politiques des institutions financières internationales, des agences bilatérales de coopération et des ONGs. Celles-ci se donnent pour ambition de transformer les économies, les systèmes politiques et les organisations sociales sahéliennes, en faisant la promotion du libéralisme, de la bonne gouvernance et de la société civile. Ces axes directeurs, qui constituent le champ de bataille contemporain du développement, forment un ensemble dans lequel la spécificité sahélienne notamment frontalière est rarement prise en compte. C'est pourquoi l'étude conclut en faveur d'un renouvellement des politiques de développement appliquées aux espaces frontaliers. Trois grands axes d'intervention peuvent alors être dégagés, lesquels permettent de réconcilier des acteurs et des logiques longtemps dissociés: ceux des espaces séparés par une limite administrative, ceux de la sphère urbaine et rurale et ceux du capitalisme marchand et de l'investissement agricole, en renforçant la coopération économique transfrontalière, en prenant en considération les interactions croissantes entre villes et campagnes et en appuyant les activités marchandes. Abstract: Urbanisation in West Africa is recent and fast. If only 10 % of the total population was living in urban areas in 1950, this proportion reached 40 % in 2000 and will be estimated to 60 % in 2025. Small and intermediate cities, located between the countryside and large metropolis, are particularly concerned with this process. They are nowadays considered as efficient vectors of local economic development because of fiscal or monetary disparities between states, which enable businessmen to develop particular skills based on local urban networks. The majority of theses networks are informal and extremely flexible, like in the Gaya - Malanville - Kamba region, located between Niger, Benin and Nigeria. Evidence show that this economic space is characterised by high potentialities (climatic and hydrological conditions, location on main economic West African axis) and few constraints (remoteness of some potentially high productive areas). In this context, this PhD deals with the economic relationships between the three market cities. Focusing on the links that unite the businessmen of the local markets - called patron; - it reveals the extreme flexibility of their strategies as well as the deeply informal nature of their activities. Through the analysis of examples taken from the commerce of agricultural products, import and export flows and detail activities, it studies the changes that have taken place in the city centres of Gaya, Malanville and Kamba. Meanwhile, this research shows how these cities represent a border economical area based on rival and complementary connections. In the first Part, it was necessary to reconsider the usual spatial analysis devoted to the question of economic centrality. As a matter of fact, the organisation of West African economic spaces is very flexible and mobile. Centrality is always precarious because of seasonal or temporary reasons. This is why the first chapters are devoted to the study of the specificity of the Sahelian territoriality. Two main elements are relevant: first the population diversity and second, the urban-rural linkages. In the second part, the study considers three main factors on which the cross-border economic networks are dependent: enclosure that prevents goods to reach the markets, administrative constraints that limit free trade between states and cities and the concurrent or complementary relationships between markets. A third part deals with the clientelist ties engaged between the patrons and their clients with the hypothesis that these relationships are based on reciprocity and inequality. A fourth part is devoted to' the study of the spatial organisation of commercial goods across the borders, as far as the agriculture commercial products, the import-export merchandises and the retail products are concerned. This leads to the conclusion that the economic activity is directly linked to urban growth. However, the study notices that there is a lack of efficient policies dealing with strengthening the business sector and improving the cross-border cooperation. This particularity allows us to favour new local development approaches, which would take into account the important potential of private economical actors. In the same time, the commercial flows should be regulated with the help of public policies, as long as they are specifically adapted to the problems that these areas have to deal with.