Creation of weighted Theissen polygons using Python

Abstract: This project is an exploration into creating and manipulating Thiessen polygons. Thiessen polygons are zones created around points to show the area closer to each point than any other point in the set. Thiessen polygons are used to extend climate data from individual stations across areas. After creating the new procedure applications of the algorithm were considered. The manipulation explored in the project focused on allowing the borders of traditional Thiessen polygons to be shifted based on values among the points. These manipulated Thiessen polygons have been dubbed weighted Thiessen polygons. These weighted Thiessen polygons were created using the Python programing language and ESRI ARCMAP software. Each edge of weighted Thiessen polygons gets shifted so that points with higher values get larger zones proportional to other points. In order to demonstrate how weighted Thiessen polygons work a set of points corresponding to teams from the National Football League were weighted based on team wins and playoff success over ten year increments starting from the 1966 season that marked the first Superbowl. These results were used to estimate fan bases among teams and shifts over time

The role of social relationships in the association between adolescents' depressive symptoms and academic achievement

While research has established that depression interferes with academic achievement, less is understood about the processes by which social relationships may buffer the relationship between depression and academic outcomes. In this study we examined the role of positive relationships in the school, family and peer contexts in the association between depressive symptoms and academic achievement among 894 adolescents aged 12-17 years living in Santiago, Chile. Depressive symptoms were associated with lower levels of academic achievement; parental monitoring, school belonging, positive mother relationships, and having academically inclined peers moderated this relationship, though some interactions differed by sex and age. Implications for promoting the academic success of adolescents experiencing depressive symptoms are discussedR01 DA021181 - NIDA NIH HHS; R01 HD033487 - NICHD NIH HH

The association of recreational space with youth smoking in low-socioeconomic status neighborhoods in Santiago, Chile

OBJECTIVES: This study examines the relationship of neighborhood recreational space with youth smoking in mid- to low-income areas in the capital of Chile, Santiago. METHODS: A unique data set of adolescents (n = 779, mean age = 14, 51 % male) provided home addresses of study participants which were geocoded and mapped. Satellite maps of neighborhoods were used to identify open spaces for recreational use (e.g., soccer fields and plazas). Thiessen polygons were generated to associate study participants with the nearest available open space using ArcGIS. Regression models, with smoking as a dependent variable, were estimated in which age, sex, family socioeconomic status, peer substance usage, neighborhood crime, and accessibility of open space were covariates. RESULTS: The results show that residential proximity to recreational space was significantly and inversely associated with tobacco consumption among female, but not male, adolescents. Age and neighborhood crime were both positively associated with tobacco consumption among both male and female adolescents. CONCLUSIONS: This study suggests that recreational spaces in proximity to residences may have a positive impact on reducing adolescents' inclination to consume tobacco. The relationship of the accessibility to such spaces with smoking appears to vary by adolescents' sex.R01 HD033487 - NICHD NIH HHS; R01 DA021181 - NIDA NIH HH

Sustainable Planning of Land Use Changes in farming areas under ecological protection

Land use has been changing in the last decades because of agricultural intensification and land abandonment which implies deterioration in the optimum habitat structure and quality. Habitat degradation and loss, resulting from changes in land use remain significant drivers of biodiversity loss. These trends are widely recognised and have forced national and international agencies to identify protected sites for natural areas with high biodiversity value. Special Protection Areas (SPAs) are natural zones particularly relevant for nature conservation. Regional planning is bound to play an increasing role in nature conservation policies because much biodiversity is located in farming areas outside natural parks. Agriculture in the Mediterranean Basin has always been highly dependent on rainfed crops, cereal, vine and olive. Vine growing plays an important role not only from the economic point of view, but also environmentally as a permanent plant cover in terms of preventing erosion, managing land and water resources in a sustainable way, defending against desertification an settling population in rural areas. A Geographic Information System (GIS) was used to implement a decision tool system to analyse the feasibility of new proposals to upgrade traditional vineyards in Castilla-La Mancha, Spain. The study focuses on the sustainability of current farming practices in Special Protection Areas for Steppe Land Birds. This paper presents a model to quantify the resulting habitat fragmentation basing on infrastructure facilities, leading to mapping areas where to apply restriction measures to prevent physical destruction of the habita

Ethnic inequality

This study explores the consequences and origins of between-ethnicity economic inequality both across and within countries. First, combining satellite images of nighttime luminosity with the historical homelands of ethnolinguistic groups we construct measures of ethnic inequality for a large sample of countries and show that the latter is strongly inversely related to comparative development. Second, differences in geographic endowments across ethnic homelands explain a sizable portion of ethnic inequality contributing to its persistence over time. Third, exploiting across-district within-African countries variation using individual-level data on ethnic identification and well-being from the Afrobarometer Surveys we find that betweenethnic- group inequality is systematically linked to regional under-development. In this sample we also explore the channels linking ethnic inequality to (under) development, finding that ethnic inequality maps to political inequality, heightened perceptions of discrimination and undersupply of public goods

Understanding the Jobs-Affordable Housing Balance in the Richmond Region

The mismatch between location of jobs and housing has a significant impact on the efficiency and quality of life within metropolitan areas. A well-planned region strives to be a “community of short distances.” A wide range of housing choices located close to employment centers could shorten commuting distances and substantially reduce government outlays for transportation facilities, reduce household transportation expenses, and increase feasibility of pedestrian movement. These needs are particularly important to families earning modest wages. CURA, with support from The Community Foundation Serving Richmond and Central Virginia and the Richmond Association of Realtors, has analyzed the spatial pattern of lower-wage jobs and lower-cost housing within the Richmond Metropolitan Statistical Area (MSA). The analysis reveals how low-cost housing and modest-wage jobs in the Richmond region are not well-balanced. Few areas in which modest-wage jobs cluster have comparable levels of low-cost housing. The established suburban areas north, west, and south of Richmond’s urban center have a large number of retail and service jobs that pay modest wages, yet these areas provide few affordable-dwelling units for these wage earners. The second part of this study addressed a major obstacle to the construction of new, affordable-housing units: fears. Many new, affordable dwelling units, by financial necessity, will be built at higher densities and smaller size to reduce cost. Homeowners in nearby neighborhoods often oppose construction of these units over fear of reduced property values, higher crime, and other factors. Six higher-density, 3 lower-cost housing projects were studied for their impact on the nearby middle-income neighborhoods. Documentation of home sale prices, assessment values, and crime rates before and after construction of the more affordable dwelling units did not reveal any notable long-term impact on crime rates, property values, or property sales

Impacts of the Boom-Bust Cycle on the Effectiveness of Policies for Moderating the Consequences of Sprawl on Residential Development

urban sprawl, spatial discrete-choice model, Land Economics/Use,

From symmetry breaking to Poisson Point Process in 2D Voronoi Tessellations: the generic nature of hexagons

We bridge the properties of the regular triangular, square, and hexagonal honeycomb Voronoi tessellations of the plane to the Poisson-Voronoi case, thus analyzing in a common framework symmetry breaking processes and the approach to uniform random distributions of tessellation-generating points. We resort to ensemble simulations of tessellations generated by points whose regular positions are perturbed through a Gaussian noise, whose variance is given by the parameter α2 times the square of the inverse of the average density of points. We analyze the number of sides, the area, and the perimeter of the Voronoi cells. For all valuesα >0, hexagons constitute the most common class of cells, and 2-parameter gamma distributions provide an efficient description of the statistical properties of the analyzed geometrical characteristics. The introduction of noise destroys the triangular and square tessellations, which are structurally unstable, as their topological properties are discontinuous in α = 0. On the contrary, the honeycomb hexagonal tessellation is topologically stable and, experimentally, all Voronoi cells are hexagonal for small but finite noise withα <0.12. For all tessellations and for small values of α, we observe a linear dependence on α of the ensemble mean of the standard deviation of the area and perimeter of the cells. Already for a moderate amount of Gaussian noise (α >0.5), memory of the specific initial unperturbed state is lost, because the statistical properties of the three perturbed regular tessellations are indistinguishable. When α >2, results converge to those of Poisson-Voronoi tessellations. The geometrical properties of n-sided cells change with α until the Poisson- Voronoi limit is reached for α > 2; in this limit the Desch law for perimeters is shown to be not valid and a square root dependence on n is established. This law allows for an easy link to the Lewis law for areas and agrees with exact asymptotic results. Finally, for α >1, the ensemble mean of the cells area and perimeter restricted to the hexagonal cells agree remarkably well with the full ensemble mean; this reinforces the idea that hexagons, beyond their ubiquitous numerical prominence, can be interpreted as typical polygons in 2D Voronoi tessellations