La presente investigación, se enfoca en los clusters ambientales y su implementación legal en nuestro país, teniendo en cuenta que un cluster es una concentración geográfica de empresas, instituciones y cadenas productivas, que cooperan para lograr un objetivo común, será necesario exponer en primer lugar el rol que presentan las empresas en materia de medio ambiente, para ello, el primer capítulo muestra el marco normativo ambiental general, así como el grado de responsabilidad que tiene el privado en relación al ambiente, enfatizando que el modelo clásico de regulación ambiental debe ceder el paso a una regulación más dinámica, mostrando modelos como la autorregulación y la importancia que presentan las ecoauditorias para las empresas en el cumplimiento de las responsabilidades con el medio ambiente. Atendiendo al particular rasgo cooperativo que se da en un cluster entre los distintos agentes económicos, abordaremos en el segundo capítulo la cooperación existente entre los niveles publico y privado en relación al medio ambiente, con ello, se explora los modelos aplicados en los sistemas federales y unitarios, demostrando que estos sistemas presentan importantes similitudes, haciendo factible la aplicación nacional de modelos regulatorios extranjeros, de esta manera, se expone formas de regulación más flexibles, que permiten acercar las políticas ambientales a la realidades particulares, plasmando en la normativa las prioridades que presentan tanto empresas privadas como sociedad civil en relación a una problemática ambiental en concreto y su posible solución, debido al particular grado de cooperación que se da estos modelos. Por último, el tercer capítulo expone el potencial medioambiental del clusters, enfatizando el rol fundamental que presenta el Estado para poder hacer posible que un cluster ambiental genere los resultados deseados, tanto a nivel de política ambiental como económica, requiriendo para ello, un grado de cooperación que se traduzca en incentivos necesarios así como una regulación dinámica que permitan traducir las particularidades de cada realidad regional, en lo productivo y lo ambiental, llegando a concluir que este modelo es viable en nuestro país.

We present the 1.4-GHz catalog of the galaxy cluster field RCS J022434-0002.5, at a redshift of z = 0.773. A total of 194 sources were found within a ∼0.28 degree2 region to a 5sigma depth of ∼75 muJy. We show that the differential source counts for the cluster field are in good agreement with other radio surveys, and therefore do not indicate a strong excess of radio sources in the cluster compared to the field. We find 13 sources have optical counterparts with photometric redshifts within 1sigma of the cluster redshift and an additional 5 within 2sigma, and we consider these objects to be candidate cluster members. We use their radio luminosities to attempt to diagnose the presence of active galactic nuclei or star formation activity. We find that the cluster candidates are statistically more likely to be powered by active galactic nuclei, rather than star formation.

Clusters of galaxies are host to powerful Active Galactic Nuclei (AGN) that greatly affect the thermal history of clusters. By keeping X-ray emitting gas from cooling, massive, run away star formation does not occur in the brightest cluster galaxy (BCG). This is achieved through radio jets displacing large quantities of metal-rich gas and carving out cavities in the intracluster medium (ICM). This metal-rich gas was originally formed within the BCG and ejected through type Ia supernovae. The current distribution of the ejecta suggests an extra source of energy has spread the material far out into the ICM. Currently, it is unclear what mechanisms are responsible. In this thesis, I present evidence, in the form of X-ray imaging and spectra, that establishes a link between AGN and the observed distribution of metal-rich gas. First, the BCG in the Abell 1664 cluster is unusually blue and is forming stars at a rate of ~23 solar masses per year. The BCG is located within 5 kpc of the X-ray peak, where the cooling time of 3.5×10^8 yr and entropy of 10.4 keV cm^2 are consistent with other star-forming BCGs in cooling flow clusters. The cooling rate in this region is roughly consistent with the star formation rate, suggesting that the hot gas is condensing onto the BCG. We use the scaling relations of Birzan et al. (2008) to show that the AGN is underpowered compared to the central X-ray cooling luminosity by roughly a factor of three. We suggest that A1664 is experiencing rapid cooling and star formation during a low-state of an AGN feedback cycle that regulates the rates of cooling and star formation. Modeling the emission as a single temperature plasma, we find that the metallicity peaks 100 kpc from the X-ray center, resulting in a central metallicity dip. However, a multi-temperature cooling flow model improves the fit to the X-ray emission and is able to recover the expected, centrally-peaked metallicity profile. Next, using deep Chandra observations of the Hydra A galaxy cluster, we examine the metallicity structure near the central galaxy and along its powerful radio source. We show that the metallicity of the ICM is enhanced by up to 0.2 dex along the radio jets and lobes compared to the metallicity of the undisturbed gas. The enhancements extend from a radius of 20 kpc from the central galaxy to a distance of ~120 kpc. We estimate the total iron mass that has been transported out of the central galaxy to be between 2E7 and 7E7 solar masses which represents 10% - 30% of the iron mass within the central galaxy. The energy required to lift this gas is roughly 1% to 5% of the total energetic output of the AGN. Evidently, Hydra A’s powerful radio source is able to redistribute metal-enriched, low entropy gas throughout the core of the galaxy cluster. The short re-enrichment timescale < 1E9 yr implies that the metals lost from the central galaxy will be quickly replenished. Finally, we present an analysis of the spatial distribution of metal-rich gas in 29 galaxy clusters using deep observations from the Chandra X-ray Observatory. The BCGs have experienced recent active galactic nucleus activity in the forms of bright radio emission, cavities, and shock fronts embedded in the hot atmospheres. The heavy elements are distributed anisotropically and are aligned with the large-scale radio and cavity axes. They are apparently being transported from the halo of the BCG into the ICM along large-scale outflows driven by the radio jets. The radial ranges of the metal-enriched outflows are found to scale with jet power as R ~ P^0.43, with a scatter of only 0.42 dex. The heavy elements are transported beyond the extent of the inner cavities in all clusters, suggesting this is a long lasting effect sustained over multiple generations of outbursts. Black holes in BCGs will likely have difficulty ejecting metal enriched gas beyond 1 Mpc unless their masses substantially exceed 1E9 solar masses. It is likely however for these black holes to output enough energy to uplift all the peaked, metal-rich gas beyond the BCG to the currently observed widespread distribution.

This thesis addresses two fundamental questions in astrophysics: (i) To what extent is environment a driver of galaxy evolution? And (ii) How does hierarchical structure formation affect the galaxy environment? The former is addressed by examining the environments of starburst galaxies, the latter by examining clusters undergoing major mergers with focus placed on the efficacy of ??cold fronts?? in identifying systems that have recently undergone a major merger - an essential first step to understanding their impact. For the first of these studies, the 2dFGRS was exploited to select large samples of starburst galaxies. These were used to derive measurements of the local and large-scale environments, clustering properties, and morphologies of starburst galaxies. It is found local environment is most germane in terms of a starburst triggering mechanism, with the starburst galaxies showing an excess of close (<20 kpc) neighbours with comparable luminosity/mass, while 20-30% exhibit a morphology consistent with them being involved in an ongoing tidal/merger interaction. On large scales (5-15 Mpc), the starburst galaxies were found to be much less clustered compared to the overall 2dFGRS population, and were not preferentially found in rich clusters with just over half residing in low to intermediate luminosity groups. However, in a number of cases, evidence for obvious local environmental influences was lacking, indicating starbursts can also be internally driven. For the latter study, the Chandra, archive was used to select a sample of clusters exhibiting ??cold front?? features. Selection required the presence of significant density jumps (>1.5 at the lower 90% CI) in the intracluster medium and for the gas on the denser side of the front to be cooler. From this sample, the clusters Abell 1201, Abell 2163, RXJ1720.1+2638, and Abell 3667 were targeted for comprehensive spectroscopic follow-up at optical wavelengths using the 3.9m Anglo Australian and 6.5m Multiple Mirror Telescopes. Using 321 spectroscopically confirmed members for Abell 1201, 550 for Abell 3667 and 491 for Abell 2163 it is shown that these clusters contain substructure which can be directly related to the cold fronts, whilst for 335 confirmed members in RXJ1720.1+2638 promising evidence exists for merger activity related to the cold front. Despite the range of different types of cold fronts and substructures detected, it is clear that cold fronts are robust signposts of merger activity.

The phenomena of disfluency clusters have been examined in the speech of children who stutter (CWS) and children who do not stutter (CWNS). Little is known about disfluency clusters in the adult population. The purpose of this study was to examine the characteristics of disfluency clusters in adults who stutter (AWS). The participants were ten AWS ranging in age from 18 to 60 (mean age = 35), with a stuttering severity of 9 to 30% (mean = 19%). Each participant provided a conversational speech sample of at least 300 words. Analysis focused on disfluency type, utterance length, speaking rate, and perceptual measures. Findings indicated that utterances containing disfluency clusters were significantly longer than fluent utterances and the speaking rate of fluent utterances was found to be significantly faster than that of disfluent utterances. Collectively the results appear to support a linguistic interpretation of disfluency clusters. The clinical implications of the findings are discussed.

Thesis (Ph. D.)-University of Hong Kong, 2009. / Includes bibliographical references (p. 223-258). Also available in print.

Thesis (Ph. D.)-University of Hong Kong, 2009. / Includes bibliographical references (p. 223-258). Also available online.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 89-97). Also available on the Internet.

Thesis--Wisconsin. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains viii, 164 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references (p. 95-108).