2,737 research outputs found

    Adsorci贸n de boro del agua

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    En el siguiente trabajo se propone la t茅cnica de la adsorci贸n mediante la utilizaci贸n de pol铆meros naturales para eliminar el boro de residuos industriales, puesto que estos residuos presentan una gran problem谩tica medioambiental. El biopol铆mero con el que se trabaj贸 fue el quitosano, modificado qu铆micamente, 茅ste se us贸 para pruebas de adsorci贸n de boro en soluciones acuosas de concentraciones de 5 y 50 ppm de boro. Dichas pruebas se basaron en dos fases de experimentaci贸n. La primera fase consisti贸 en poner en contacto las soluciones con perlas de quitosano-n铆quel de fabricaci贸n propia siguiendo un determinado protocolo, dicha fase const贸 de dos etapas, es decir que se realizaron las mismas pruebas dos veces para tener un mayor n煤mero de resultados y para corregir posibles errores de an谩lisis. La segunda fase consisti贸 en poner en contacto las soluciones con perlas de alginato ya fabricadas, disponibles en el laboratorio. Culminadas ambas fases de experimentaci贸n se midi贸 la concentraci贸n de boro por espectrofotometr铆a de absorci贸n molecular y la concentraci贸n de n铆quel por espectroscopia de absorci贸n at贸mica. En ambos casos se obtuvieron resultados satisfactorios, en cuanto al boro se logr贸 remover hasta valores por debajo del l铆mite permisible para consumo humano que establece la normativa europea (1 ppm) y lo que recomienda la Organizaci贸n Mundial de la Salud (0.5 ppm), y en algunos casos se logr贸 remover totalmente dicho metaloide. En cuanto al n铆quel se logr贸 remover hasta valores por encima del l铆mite permisible para consumo humano, pero por debajo del l铆mite permisible para los vertidos provenientes de la industria. Finalmente, se le dio una posible utilidad o aplicaci贸n a este proyecto, relacion谩ndolo con la reducci贸n de boro del agua de mar, teniendo en cuenta la problem谩tica que presenta el agua desalinizada respecto a su alta concentraci贸n de boro y su aplicaci贸n como agua de riego. Tambi茅n, en esta ocasi贸n se obtuvieron resultados satisfactorios, logrando remover el boro a valores por debajo de 0.3 ppm, esta cifra se refiere a las cosechas m谩s sensibles al boro (谩rboles frutales de c铆tricos), las cuales presentan da帽o foliar a concentraciones de boro en el agua de riego mayores a 3 ppm

    Alaskan Arctic epibenthic communities: distribution patterns, links to the environment, and brittle star population dynamics

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    Thesis (Ph.D.) University of Alaska Fairbanks, 2016The Arctic marine shelves are characterized by areas of high and low invertebrate standing stock and communities that vary spatially in patches. Large-scale environmental characteristics, such as the distribution of water masses, the fenology of sea ice cover, and variability of water depth define changes in epibenthic community structure throughout the Arctic shelves. The longevity and relatively low mobility of epibenthic invertebrates make them especially relevant as indicators of long-term environmental patterns. In terms of standing stock and biomass, the most representative group among Arctic epibenthic taxa are brittle stars. Large areas of the Arctic shelves have dense assemblages of brittle stars; however, despite their ecological importance for Arctic shelf systems, little is known of their age, growth and turnover rates. The research developed through this dissertation examined how environmental drivers influence epibenthic invertebrate communities of the Alaska Arctic shelves and the population parameters of the dominant brittle star species. The first chapter of my dissertation focused on the northeastern Chukchi Sea and the second one focused on the Alaskan Beaufort Sea. The overarching questions addressed in chapters 1 and 2 focused on characterizing the epibenthic communities of the Alaskan Chukchi and Beaufort seas and defining environmental characteristics that influence the community structure. To answer this question, biological and environmental data were collected and analyzed in 2009 and 2010 in the Chukchi Sea, and in 2011 in the Beaufort Sea. For my third chapter, the overarching question was: what is the predictive power of the seasonality of sea ice for epibenthic community structure in the Alaskan Arctic, and how does it compare to more commonly used environmental descriptors. To test this relationship, six variables depicting the patterns of the seasonality of sea ice were computed from passive microwave sea ice concentration data. For the fourth chapter, the overarching question was, what are the population parameters of the two dominant brittle star species of the Alaskan Arctic. For this analysis, individuals of Ophiura sarsii and Ophiocten sericeum were collected in 2013 for age and organic mass determination. Findings of this research indicate that epibenthic communities have a patchy distribution with one or a few taxa dominating the community over large spatial extents. In both the Chukchi and Beaufort seas, communities were dominated by either crustaceans or echinoderms. Only in the mid-depth stations of the Beaufort Sea were both groups equally abundant. The environmental measure that best correlated to epibenthic commuity structure in both regions was longitude. Biologically relevant variables, such as sediment grain size, sediment phaeopigments, bottom water temperature and salinity, though region specific, were also important drivers of commuity structure. As predictors of epibenthic community structure, sea ice variables resulted in moderate to high correlation values. In the Beaufort Sea, sea ice variables performed better than traditionally used environmental descriptors; however, this was not the case for the Chukchi Sea. This study is the first to report on the age, growth and turnover of Arctic brittle stars. The asymptotic age was higher for O. sarsii than for O. sericeum; however, both species had significantly higher maximum ages than temperate region congeners. The individual production of O. sarsii surpassed that of O. sericeum by an order of magnitude throughout the size spectra. As a whole, this research highlights the complexity of the biological-environmental interactions that create the large spatial variability in community structure, benthic biomass and diversity throughout the Alaska Arctic. The variability in community structure throughout the Chukchi and Beaufort seas was linked qualitatively to large-scale environmental patterns. Quantitatively, these environmental forces were represented by the date of sea ice return and date of sea ice retreat in the Beaufort Sea. The predictive power of sea ice variables was reduced in the Chukchi Sea by the large inter-annual variability in wind direction and intensity that in turn affect the pattern of seasonality of sea ice. As integrators of large-scale environmental patterns, sea ice variables proved useful as additional predictors of epibenthic community structure. The dominant shelf brittle star species do not experience short-term fluctuations in population size. Top-down and bottom-up controls on these populations, such as predation and food supply, may be governing their growth strategy and total annual growth. Considering the longevity and slow growth of many Arctic epibenthic species such as brittle stars, the recovery after disturbance could require decades to restore high biomass in some areas. Environmental changes associated with climate change and resource development in the Arctic shelves have the potential to create large changes in the benthic system, such as local changes epibenthic community composition, dominant taxa, community diversity and benthic biomass hotspots. Future research focusing on the biological interactions that influence epibenthic communities, the supply and success of new recruits to the benthos and the temporal stability of epibenthic communities would help complete our understanding of the spatial and temporal variability of Arctic epibenthic communities and make solid predictions of future scenarios.General introduction -- CHAPTER 1: Epibenthic community variability in the northeastern Chukchi Sea -- CHAPTER 2: Spatial variability of epibenthic communities on the Alaska Beaufort Shelf -- CHAPTER 3: What lies beneath the ice: relating seasonal sea ice patterns with benthic shelf fauna in the Alaska Arctic -- CHAPTER 4: Growth and production of the brittle stars Ophiura sarsii and Ophiocten sericeum (Echinodermata: Ophiuroidea) in the Alaskan Arctic -- Summary and conclusion

    Associations of HIV Risk Behaviors among Older Latinas and their Adult Daughters

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    This dissertation examines the associations between adult Latina daughters鈥 HIV risk behaviors and that of their older Latina mothers鈥 HIV risk behaviors. The central hypothesis of the study is that adult Latina daughters鈥 influence their older mothers鈥 behaviors and that such behaviors interact with the level of their attachment. Older Latinas are a vulnerable population that face cultural risk factors, health care provider bias, and engage in low rates of HIV testing. The primary mode of HIV infection for Latinas is through heterosexual contact. Yet, traditional gender norms such as marianismo belief place pressure on Latina women to be submissive to their partners, disregard their infidelities, and not attempt to negotiate condom use, increasing the risk of HIV infection among Latinas via heterosexual sex with their primary partners. Efforts by the CDC to increase HIV testing have emerged as a critical part of HIV prevention. However, research has indicated that older Latinas are less likely to speak to a health care provider about safe sex practices or HIV testing than their younger counterparts. Despite health care providers having strong influences over Latinas鈥 decisions to perform health related tests, physicians are not endorsing HIV testing for their older patients. This in part, leads to a disproportionate number of late stage diagnoses among older adults. Evidence suggest that adult daughters are a source of support and assistance in health-related issues for their aging mothers and are uniquely positioned to influence their mothers鈥 health-related behaviors and decisions. Additionally, mother-daughter attachment has been found to be a protective factor to other risky health behaviors. The present study (1) Examined the association between recurrent HIV risk behaviors of adult Latina daughters and those of their older Latina mothers and (2) examined the moderating effect mother-daughter attachment have on those associations. No statistical significance was found in examining the association between adult Latina daughters and their older mothers, nor was attachment found to be a moderator on those associations. Findings show culture may be the significant factor influencing the lack of association between adult Latina daughters and their older mothers. Results add to the literature and scientific field of social work and public health. Additionally promoting studies on cultural barriers that may exist in adult Latina daughter and older mother upward communication as techniques to promote healthy behaviors among older Latinas

    Free energy and vibrational entropy difference between ordered and disordered Ni3Al

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    We have calculated free energy and vibrational entropy differences in Ni3Al between its equilibrium ordered structure and a disordered fcc solid solution. The free energy and entropy differences were calculated using the method of adiabatic switching in a molecular-dynamics formalism. The path chosen for the free-energy calculations directly connects the disordered with the ordered state. The atomic interactions are described by embedded-atom-method potentials. We find that the vibrational entropy difference increases with temperature from 0.14kB/atom at 300 K to 0.22kB/atom at 1200 K. We have calculated the density of states (DOS) of the disordered phase from the Fourier transform of the velocity-velocity autocorrelation function. The disordered DOS looks more like a broadened version of the ordered DOS. Analysis of the partial density of states shows that the Al atoms vibrations are most affected by the compositional disorder. The phonon partial spectral intensities along the 銆100銆 direction show that the vibrational spectrum of the disordered phase contains intensities at optical mode frequencies of the ordered alloy. We find that the volume difference between the ordered and disordered phases plays the most crucial role in the magnitude of the vibrational entropy difference. If the lattice constant of the two phases is set to the same value, the vibrational entropy difference decreases to zero

    Assessment of the microbiome associated with endangered orchids

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    The Orchidaceae (orchid family) is perhaps the most speciose group of flowering plants with approximately 25,000 described species and many thousands of hybrids. While certain mycorrhizal fungi are required for orchids to germinate, these mycorrhizae form just part of a microbial community that interacts with the plant. In this study, we sought a broader picture of the microbiome associated with these plants. A major motivation for our work is the concern that the gaps in our understanding of orchid microbiomes might have important consequences when decisions are made in the management of species of conservation concern. Because of the complexity of their symbiotic interactions, orchids are particularly at risk when faced with habitat loss or the potential effects of climate change. We studied two species of endangered terrestrial orchids in Missouri and, using DNA collected from soil and high throughput sequencing, evaluated the bacterial microbiome associated with these two orchid species.Includes bibliographical reference

    Estratificaci贸n de la informaci贸n ambiental y construcci贸n de bioindicadores: identificaci贸n de 谩reas prioritarias para la conservaci贸n de la biodiversidad.

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    Las regiones naturales de la provincia de C贸rdoba presentan diversos ecosistemas que est谩n afectados por un constante deterioro ambiental siendo degradadas por la deforestaci贸n, el avance de la frontera agropecuaria, los incendios rurales, la introducci贸n de plantas ex贸ticas, el sobre-pastoreo, las sequ铆as prolongadas, y el crecimiento urbano de las villas tur铆sticas. La biodiversidad permite que los ecosistemas tengan mayor resiliencia ante cambios clim谩ticos o antr贸picos, siendo de suma importancia para mantener los servicios ecosist茅micos. La experiencia adquirida por el equipo de trabajo del CREAN en el monitoreo de sitios pilotos a trav茅s del proyecto LADA/FAO mediante la metodolog铆a WOCAT, para la evaluaci贸n de la degradaci贸n de la tierra y los usos de la tierra sirve de antecedente tecnol贸gico para encarar este proyecto multidisciplinario en red. El producto a obtener es una cartograf铆a multicapa sobre los usos de la tierra (LUS), en la regi贸n de las Sierras Chicas de C贸rdoba en donde queden delimitadas las 谩reas naturales conservadas, las zonas explotadas con un uso sustentable, las 谩reas degradadas con procesos de desertificaci贸n, el estado de las cuencas proveedoras de agua a r铆os y embalses, como as铆 tambi茅n las zonas urbanas y de explotaciones agropecuarias o mineras. Sobre la base de esta evaluaci贸n de bioindicadores y estratificaci贸n de la informaci贸n ambiental se puede proveer de informaci贸n a decisores sociales y pol铆ticos para que establezcan medidas que contribuyan a realizar acciones que protejan el ambiente, promuevan el manejo sustentable de las tierras y establezcan normativas para la conservaci贸n del suelo, el agua y la biodiversidad