964 resultados para Street dust


Relevância:

20.00% 20.00%

Publicador:

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Context. Debris discs are a consequence of the planet formation process and constitute the fingerprints of planetesimal systems. Their solar system counterparts are the asteroid and Edgeworth-Kuiper belts. Aims. The DUNES survey aims at detecting extra-solar analogues to the Edgeworth-Kuiper belt around solar-type stars, putting in this way the solar system into context. The survey allows us to address some questions related to the prevalence and properties of planetesimal systems. Methods. We used Herschel/PACS to observe a sample of nearby FGK stars. Data at 100 and 160 μm were obtained, complemented in some cases with observations at 70 μm, and at 250, 350 and 500 μm using SPIRE. The observing strategy was to integrate as deep as possible at 100 μm to detect the stellar photosphere. Results. Debris discs have been detected at a fractional luminosity level down to several times that of the Edgeworth-Kuiper belt. The incidence rate of discs around the DUNES stars is increased from a rate of ~12.1% ± 5% before Herschel to ~20.2% ± 2%. A significant fraction (~52%) of the discs are resolved, which represents an enormous step ahead from the previously known resolved discs. Some stars are associated with faint far-IR excesses attributed to a new class of cold discs. Although it cannot be excluded that these excesses are produced by coincidental alignment of background galaxies, statistical arguments suggest that at least some of them are true debris discs. Some discs display peculiar SEDs with spectral indexes in the 70–160 μm range steeper than the Rayleigh-Jeans one. An analysis of the debris disc parameters suggests that a decrease might exist of the mean black body radius from the F-type to the K-type stars. In addition, a weak trend is suggested for a correlation of disc sizes and an anticorrelation of disc temperatures with the stellar age.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

We present the first far-IR observations of the solar-type stars δ Pav, HR 8501, 51 Peg and ζ^2 Ret, taken within the context of the DUNES Herschel open time key programme (OTKP). This project uses the PACS and SPIRE instruments with the objective of studying infrared excesses due to exo-Kuiper belts around nearby solar-type stars. The observed 100 μm fluxes from δ Pav, HR 8501, and 51 Peg agree with the predicted photospheric fluxes, excluding debris disks brighter than L_dust/L_* ~ 5 x 10^-7 (1σ level) around those stars. A flattened, disk-like structure with a semi-major axis of ~100 AU in size is detected around ζ2 Ret. The resolved structure suggests the presence of an eccentric dust ring, which we interpret as an exo-Kuiper belt with L_dust/L_* ≈ 10^-5.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

We present the results of the analysis of satellite imagery to study light pollution in Spain. Both calibrated and non-calibrated DMSP-OLS images were used. We describe the method to scale the non-calibrated DMSP-OLS images which allows us to use differential photometry techniques in order to study the evolution of the light pollution. Population data and DMSP-OLS satellite calibrated images for the year 2006 were compared to test the reliability of official statistics in public lighting consumption. We found a relationship between the population and the energy consumption which is valid for several regions. Finally the true evolution of the electricity consumption for street lighting in Spain from 1992 to 2010 was derived; it has been doubled in the last 18 years in most of the provinces. (C) 2013 Elsevier Ltd. All rights reserved,

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This memoir chronicles the three summers I spent working in the factories at Chestnut Hill Gazebos. It focuses on three narrative strands: the day-to-day life of a factory worker, the struggles within and eventual breakdown of my relationship with my girlfriend, and how my job at Chestnut Hill helped me critique my fundamentalist Christian roots by forcing me into a deeper understanding of my faith and its relationship to the world outside the confines of my upbringing. The critical afterword uses essays by Leona Toker and other theorists as a framework for understanding how I approached several different problems when writing my memoir, such as how to present incomplete memories of events, whether or not to condense events for the sake of a more streamlined narrative, and whether or not a memoirist should use composite characters. I explain how various practitioners and critics influenced my decisions, and I also compare my approach to the practices of other memoirists.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Urban researchers and planners are often interested in understanding how economic activities are distributed in urban regions, what forces influence their special pattern and how urban structure and functions are mutually dependent. In this paper, we want to show how an algorithm for ranking the nodes in a network can be used to understand and visualize certain commercial activities of a city. The first part of the method consists of collecting real information about different types of commercial activities at each location in the urban network of the city of Murcia, Spain. Four clearly differentiated commercial activities are studied, such as restaurants and bars, shops, banks and supermarkets or department stores, but obviously we can study other. The information collected is then quantified by means of a data matrix, which is used as the basis for the implementation of a PageRank algorithm which produces a ranking of all the nodes in the network, according to their significance within it. Finally, we visualize the resulting classification using a colour scale that helps us to represent the business network.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Creación de un modelo de comunicación que fusione los mejores atributos del Street Marketing y el Street Art. Previamente, se habrán estudiado los conceptos procedentes y se habrá realizado un análisis de acciones específicas así como entrevistas a creativos del sector. Posteriormente se utilizará este modelo para crear, definir y proponer una de acción de comunicación que será promovida por una institución cultural.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Pictures of the Watoto wa Lwanga project, the efforts of the Brothers of St. Charles Lwanga not only to rehabilitate Nairobi's street children, but to prevent slum children from ending up in the streets. Features life in the slums, the situation of the street children, the efforts of the social workers to involve the children's parents, the various reception centers, the vocational school, the Boy's Town Ruai Residential School, the community of the Brothers of St. Charles Lwanga as well as interviews with former street children and with various directors and benefactors of the project.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

One leaf containing handwritten financial notes related to the closing of the Middle Street School and subsequent rent payments.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Draft of a brief letter complaining about students.