• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 362
  • 230
  • 38
  • 30
  • 30
  • 24
  • 21
  • 21
  • 21
  • 21
  • 21
  • 21
  • 11
  • 5
  • 4
  • Tagged with
  • 992
  • 348
  • 198
  • 187
  • 186
  • 155
  • 104
  • 85
  • 82
  • 80
  • 73
  • 68
  • 67
  • 67
  • 66
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
341

Análise interpretativa de cinco obras corais sacras do compositor Ernani Aguiar / Interpretative analysis of five sacred choral works from the composer Ernani Aguiar

Mariana Ferraz Simões Hammerer 12 November 2015 (has links)
Este trabalho busca apresentar uma análise focada na interpretação de cinco obras sacras para coro à cappella do compositor Ernani Aguiar. As obras são: Três Motetinos n° 1 (1975-1978), Três Motetinos n° 2 (1982), Três Motetinos n° 3 (1980-1986), Três Motetinos n° 4 e Três Motetinos n° 5 (1992). A metodologia de análise musical está sustentada a partir do Referencial Silva Ramos de Análise de Obras Corais, respondendo as questões pertinentes e depois transformando-as em texto corrido. Apresentamos um pequeno texto sobre sua trajetória de vida, mostrando sucintamente a atividade de Ernani Aguiar como compositor, regente e professor. Em seguida elencamos o conjunto de sua obra coral sacra para coro à cappella, apresentando informações como data de composição, texto utilizado, estreias e gravações das mesmas. Ainda, apresentamos a fundo outros detalhes sobre as composições das cinco obras estudadas. Na continuidade, apresentamos as análises de cada uma das cinco obras e discutimos pontos que ocorreram durante nosso processo de chegada a uma concepção para performance das mesmas. E é na esteira desse trabalho que abordamos as constâncias composicionais de Aguiar, seu modo de escrita e algumas de suas escolhas estéticas, concluindo assim esta dissertação. / This study aims to present an analysis focused on the interpretation of five sacred works for choir a cappella from the composer Ernani Aguiar. The works are: Três Motetinos No. 1 (1975-1978), Três Motetinos No. 2 (1982), Três Motetinos No. 3 (1980-1986), Três Motetinos No. 4 and Três Motetinos No. 5 (1992). The methodology of the musical analysis is sustained from the Silva Ramos Reference of Coral Work Analysis, answering the relevant questions and then turning them into plain text. We present a small text about his life story, succinctly showing Ernani Aguiar\'s activity as a composer, conductor and teacher. Then we list his sacred choral work\'s ensemble to the a cappella choir, presenting information, such as composition date, text used, premieres and its recordings. We also thoroughly present other details about the compositions of the five studied works. Continuing, we present the analysis of each of the five works and we discuss points which occurred during our process of arriving at a guideline for its performance. And it is in the wake of this work that we approach the compositional constancies of Aguiar, his writing mode and some of its aesthetic choices, thus concluding this dissertation.
342

Aspects of the invertebrate ecology of the Nwanedzi tributary of the Limpopo River

Mokgalong, Nehemiah Mashomanye January 1981 (has links)
Thesis (M. Sc. (Zoology)) -- University of the North, 1981 / Refer to the document
343

Patch Reefs in Biscayne National Park, FL: Sediments, Foraminiferal Distributions, and a Comparison of Three Biotic Indicators of Reef Health

Ramirez, Alexa 19 May 2008 (has links)
Coral cover remains highest on patch reefs at the northern end of the Florida reef tract. The reasons for this trend are not well understood, but may be related to the protection from extreme variations in water quality parameters provided by the near constant presence of islands at the north extent of the Florida Keys. Three indices have been developed based on Foraminifera and sediment constituents. Two of the indices, the FORAM Index and the SEDCON Index, were developed to indicate the suitability of a reef environment for continued reef accretion. The third index, the Photic Index, is an assessment of photic stress on reefs based on incidence of bleaching in a species of Foraminifera, Amphistegina gibbosa, which is known to experience loss of algal endosymbionts similar to bleaching in corals. Patch reefs were sampled in Biscayne National Park, FL to assess sediment characteristics and foraminiferal assemblages, as well as to examine trends in the three indices. Sediments associated with a majority (59%) of reefs were coarse sands; muddy sediments were restricted to a few inner patch reefs that were isolated from the influence of Caesar's Creek, which flushes water from inside Biscayne Bay onto the open shelf. Unidentifiable grains predominated in the sediment constituents, along with calcareous algae and molluskan debris. Shells from 82 genera of Foraminifera were identified in the sediments. Quinqueloculina was the most consistently common genus. Percent mud was the single most influential measured variable on the distribution of both sediment constituents and foraminiferal assemblages. Analysis of bleaching in the foraminifer Amphistegina gibbosa revealed that photo-oxidative stress was chronic at 94% of the sites. Patterns of FORAM and SEDCON Index values and their similarity to temperature, salinity, and percent mud distributions show that Caesar's Creek is affecting the benthic community in its immediate vicinity by providing flow that limits the accumulation of mud and potentially other anthropogenic stressors. Overall this study suggests that the reefs in this area are marginal for continued reef growth. A more detailed study of water quality through Caesar's Creek should be conducted to determine exactly how it is affecting the reefs in Biscayne National Park.
344

Burial Marks and Growth Records of a Massive Coral Pseudodiploria Strigosa as a Proxy for Severe Weather Events in Late Holocene

Unknown Date (has links)
Severe weather events that accompany climatic changes have been the main focus of many studies that want to highlight the large processes that surround us every day. These studies are based on years of data collection and other studies to help aid their pursuits. An area of major focus is identifying proxies and supplementary materials that help refine climate records of the geologic past. This study aims to identify reliable proxies for obtaining a record of severe weather events. The research consists of studying a coral species Pseudodiploria strigosa colonies with the goal to document, interpret, and describe the burial and re-exposure of massive coral colonies by severe storm or hurricane events, as recorded in coral growth patterns through density patterns and the analysis of CT-scanned coral specimens. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection
345

POPULATION GENETICS AND ALGAL SYMBIONT COMMUNITIES OF THE CORAL SPECIES MONTASTRAEA CAVERNOSA ON THE BELIZE BARRIER REEF

Unknown Date (has links)
Coral reefs worldwide are experiencing unprecedented and rapid declines. However, deeper, mesophotic coral ecosystems (MCEs; 30–150 m) may act as refuges for coral species, providing larvae to recolonize degraded shallow reefs. This study assessed the genetic connectivity of shallow and mesophotic Montastraea cavernosa populations on the Belize Barrier Reef and the community structure of their endosymbiotic algae (Family Symbiodiniaceae) across a fine-scale depth gradient (10, 16, 25, 35 m). Evaluation of nine polymorphic microsatellite markers demonstrated that relatively shallow (10 and 16 m) M. cavernosa populations were genetically distinct from relatively deep (25 and 35 m) populations. High throughput sequencing of ribosomal coding DNA from Symbiodiniaceae communities of M. cavernosa revealed differences in community structure across depth, with shallow-specialist and depth-generalist community profiles. This research provides important information for the management of distinct deep and adds to the body of research on the understudied MCEs of the Mesoamerican Reef. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection
346

Use of a Towed Camera System along the west Florida shelf: A Case Study of the Florida Middle Grounds Benthic Marine Communities

Davis, Katie S. 02 November 2018 (has links)
As technologies advance the study of ocean dynamics, new approaches to vexing problems of scale and process are becoming more widely available. Originally conceived as a tool primarily for indexing the abundance of near-bottom fishes, the Camera-based Assessment and Survey System (C-BASS) may also be an effective tool for monitoring benthic invertebrate resources vulnerable to natural and anthropogenic perturbations, and for characterizing the composition of benthic communities to inform spatial management. Using still images derived from the C-BASS video of benthic transects within the Florida Middle Grounds, I documented the abundance of benthic habitat-forming functional groups—sponges, algae, and corals—and noted taxa that were present in a SCUBA and ROV study conducted a decade earlier. Images were pre-processed using MATLAB computer programming language to correct for light attenuation and scattering in seawater at depth, and examined using ImageJ software and Coral Point Count software or rapid visual assessment methodology to assess image quality and percent cover, respectively. Exploratory data analysis (dissimilarity profile) delineated five habitat types in the northern Florida Middle Grounds, and discriminating benthic cover was identified using similarity percentage analysis: soft corals, fleshy macroalgae, low-relief algae, encrusted rubble, and sand. Hard corals and sponges represented relatively low area cover. A canonical analysis of principle components of in situ environmental measurements, chlorophyll a, turbidity, salinity, slope, and depth highlighted the association of the sand habitat type with greater depths and least amount of slope. Fleshy macroalgae were associated with greater slope, which reflected its presence in transitional areas between sand and reef. Soft coral habitat type was correlated with shallower depths, but also to lower temperature and lower salinity, highlighting the limitations of one-time environmental measurements to the condition of that time and space. A distance-based redundancy analysis of fish species abundance revealed that sponges, soft corals, and hard corals explained some of the variation of Holocentridae spp., angelfishes, and porgy, and that gray snapper appeared to associate with higher measurements of chlorophyll a. A comparison of C-BASS measurements with a coincidental stationary camera survey revealed that a slight shift in view, either from the seafloor to the water column, or from two slightly different positions in the water column, can obscure or reveal benthic cover to varying degrees, suggesting that more imaging could provide more complete representations of the benthic cover. Continued surveys of the benthic composition of the west Florida shelf could elucidate the range of environmental conditions and facilitate further investigations into the fish species associations with biotic cover in these benthic communities.
347

Endolithic algae in Barbados reef corals

Roberts, Madeleine. January 1980 (has links)
No description available.
348

Predicting the effect of climate change on the biodiversity of sessile invertebrates on a coral reef

Simon Walker Unknown Date (has links)
In the marine environment, relatively little is known about how the effects of climatic change will manifest into future patterns of biodiversity and community stability, with the exception of recent work on corals in tropical reef ecosystems. In this thesis, I examine quantitatively how patterns of coral reef biodiversity will respond to the impacts of climatic change and provide essential information (i) to address a critical knowledge gap in the understanding of coral reef biodiversity and (ii) predict how a wide range of sessile invertebrates from coral reef ecosystems will respond to a range of potential impacts of climatic change such as increased physical disturbance and rising sea level. An initial descriptive component of my thesis was required to determine the distribution and abundance of a diverse assemblages of sessile non-scleractinian invertebrates, found along gradients of increasing physical disturbance from wave action and increasing intertidal shore height. I also examined the source, intensity and frequency of disturbance along these environmental gradients. This information was used to derive testable hypotheses about the potential impacts of increasing physical disturbance and rising sea level associated with climatic change. I found that physical disturbance had a substantial influence on the types of species that are able to survive in these intertidal rubble habitats, with diversity decreasing at more exposed shores and further down the shore. Physical disturbance was more important for determining the composition of sessile assemblages than other biotic factors such as predation, which only had weak effects on these sessile assemblages. Increased frequency and intensity of waves and storms will increase rates of physical disturbances such as scraping and overturning of rubble plates, which will have a substantial negative impact on biodiversity in these tropical intertidal habitats. These effects may be more complicated that first thought when combined with the effects of rising sea level which will not only alter the extent of inundation, but may also allow wave energy to propagate further up the shore, which has the potential to modify interactions among species through changes to the supply and recruitment of larvae, predator-prey interactions, competition and survival in harsher environments. However, the magnitude of these impacts may depend on how increased physical disturbance and rising sea level affect established species, and whether they will have a substantial effect on larval mortality rates, which currently appears to be limited by physical disturbance. Declines in biodiversity as a result of climatic change over the next 100 years could have important implications for the future health and productivity of coral reef ecosystems, especially given the ecosystem services these organisms provide. A greater understanding of the processes that drive the distribution and abundance of many different types of organisms on coral reefs, and indeed in other ecosystems, will provide essential information that managers can use to better understand and maintain these important ecosystems for future generations.
349

Factors affecting the dynamics and regulation of coral-reef fish populations

Webster, Michael Scott 11 September 2001 (has links)
Ecologists have long questioned why fluctuating populations tend to persist rather than go extinct. Populations that persist indefinitely are regulated by mechanisms that cause demographic density dependence, which works to bound fluctuation above zero. In a series of studies, I have sought to determine the processes and mechanisms that regulate local populations of coral-reef fish. In the Exuma Keys, Bahamas, fairy basslets (Gramma loreto) live in aggregations on the undersides of coral-reef ledges. These aggregations often constitute local populations because movement between aggregations is rare. The largest individuals occupy prime feeding positions near the front of ledges and force smaller individuals remain near the back where they have lower feeding rates. Based on these initial observations, I designed two experimental studies of the demographic consequences of variation in basslet density. In the first study, I manipulated the density of newly-settled fish to explore the effects of high recruitment on population size. Populations with experimentally elevated recruitment converged in density with unmanipulated populations, primarily due to density-dependent mortality. I found no evidence that density dependence was caused by intraspecific competition; rather it appeared to be due to a short-term behavioral response by predators (aggregative and/or type 3 functional response). In a second study, I manipulated the densities of adults among populations with a standard average density of newly-settled fish. Two measures indicated that the intensity of competition increased at higher densities of adults, which likely made small fish more susceptible to predation, thereby causing density-dependent mortality. Long-term observations indicated that basslet populations were regulated at temporal scales exceeding two generations. At Lizard Island on the Great Barrier Reef, I also examined how patterns of recruitment of coral-reef fishes were modified across a range of natural recruit densities in the presence and absence of resident predators. Predators decreased recruitment and increased mortality for all species, but these effects varied considerably among species. The results of each of these studies stress the importance of both competitive and predatory mechanisms in modifying patterns of abundance established at the time of larval settlement, as well as regulating local population size. / Graduation date: 2002
350

Spatial Dynamics in the Growth and Spread of Halimeda and Dictyota in Florida reefs: A Simulation Modeling Approach

Yñiguez, Aletta Tiangco 12 December 2007 (has links)
Macroalgae are an important part of the coral reef ecosystem that has largely been overlooked. However, in the past few decades their abundances have increased and this has been attributed to combinations of coral mortality opening up space in the reef, decreased grazing and increased nutrient load in reefs. This dissertation illustrates a novel means of investigating the effect of various growth and disturbance factors on the dynamics of macroalgae at three different levels (individual, population and 3-species community). Macroalgae are modular and clonal organisms that have differing morphologies depending on the environment to which they are exposed. These traits were exploited in order to understand the factors that were acting on the dominant and common macroalgae in the Florida Reef Tract: Halimeda tuna, Halimeda opuntia and Dictyota sp. The agent-based model SPREAD (SPatially-explicit REef Algae Dynamics) was developed to incorporate the key morphogenetic characteristics of clonality and morphological plasticity. It revolves around the iteration of macroalgal module production in response to light, temperature, nutrients, and space availability, while fragmentation is the source for mortality or new individuals. These processes build the individual algae then the population. The model was parameterized through laboratory experiments, existing literature and databases and results were compared to independently collected field data from four study sites in the Florida Keys. SPREAD was run using a large range of light, temperature, nutrient and disturbance (fragmentation without survival) levels and yielded six morphological types for Halimeda tuna, and two each for Halimeda opuntia and Dictyota sp. The model morphological types that matched those measured in two inshore patch reefs (Cheeca Patch and Coral Gardens) and two offshore spur and groove reefs (Little Grecian and French Reef), were formed in conditions that were similar to the environmental (light, nutrient and disturbance) conditions in the field sites. There were also differences between species in the important factors that influenced their morphologies, wherein H. opuntia and Dictyota were more affected by disturbance than growth factors, while H. tuna morphology was affected by both. Allowing for fragmentation with survival in the model resulted in significantly higher population abundances (percent cover and density). The highest abundances were achieved under high fragment survival probabilities and a high disturbance level (but not large fragment sizes). Incorporating fragmentation with survival and simulating the variations in light, nutrients and disturbance between the inshore patch reefs and offshore spur and groove reefs in SPREAD led to comparable abundances of Halimeda in the virtual reef sites. Adding competition for space and light and epiphytism by Dictyota on the two Halimeda species suggests that it can regulate the populations of the three macroalgae. However, comparing model abundances to the field, competition may not be a strong regulating force for H. tuna in all the sites and H. opuntia in the patch reefs. H. opuntia in the offshore reefs is possibly competitively regulated. Although SPREAD was not able to capture the patterns in the population abundance of Dictyota, this points to the potential importance of other morphometrics not captured by the model, a variation in growth curves between reef habitats, or the differential contribution of sexual reproduction.

Page generated in 0.034 seconds