987 resultados para Detrended correspondence analysis


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Purpose. The central concepts in pressure ulcer risk are exposure to external pressure caused by inactivity and tissue tolerance to pressure, a factor closely related to blood flow. Inactivity measures are effective in predicting pressure ulcer risk. The purpose of the study is to evaluate whether a physiological measure of skin blood flow improves pressure ulcer risk prediction. Skin temperature regularity and self-similarity, as proxy measures of blood flow, and not previously described, may be undefined pressure ulcer risk factors. The specific aims were to determine whether a sample of nursing facility residents at high risk of pressure ulcers classified using the Braden Scale for Pressure Sore Risk© differ from a sample of low risk residents according to (1) exposure to external pressure as measured by resident activity, (2) tissue tolerance to external pressure as measured by skin temperature, and (3) skin temperature fluctuations and recovery in response to a commonly occurring stressor, bathing and additionally whether (4) scores on the Braden Scale mobility subscale score are related to entropy and the spectral exponent. ^ Methods. A two group observational time series design was used to describe activity and skin temperature regularity and self-similarity, calculating entropy and the spectral exponent using detrended fluctuation analysis respectively. Twenty nursing facility residents wore activity and skin temperature monitors for one week. One bathing episode was observed as a commonly occurring stressor for skin temperature.^ Results. Skin temperature multiscale entropy (MSE), F(1, 17) = 5.55, p = .031, the skin temperature spectral exponent, F(1, 17) = 6.19, p = .023, and the activity mean MSE, F(1, 18) = 4.52, p = .048 differentiated the risk groups. The change in skin temperature entropy during bathing was significant, t(16) = 2.55, p = .021, (95% CI, .04-.40). Multiscale entropy for skin temperature was lowest in those who developed pressure ulcers, F(1, 18) = 35.14, p < .001.^ Conclusions. This study supports the tissue tolerance component of the Braden and Bergstrom conceptual framework and shows differences in skin temperature multiscale entropy between pressure ulcer risk categories, pressure ulcer outcome, and during a commonly occurring stressor. ^

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This study documents the biological signatures impressed upon the sedimentary record underlying both the 5°N upwelling system of the Somali Current and the equatorial area of the Somali Basin out of the upwelling influence. The evolution of these two distinct hydrographic systems is compared for the last 160 kyr. Correspondence and cluster analyses are performed on combined radiolarian and planktonic foraminiferal quantitative data in order to study the changes of the planktonic assemblages through time and space. The Upwelling Radiolarian Index (URI) is used as a productivity proxy. The water temperature and hydrographic structure of the upper water masses appear to be the major factors controlling the distribution patterns of the fauna. The relative abundances of three groups of foraminifera, cold water form (dextral N. pachyderma), mixed layer dwellers (G. trilobus, G. ruber, G. sacculifer, G. conglobatus, and G. glutinata), and thermocline dwellers (G. menardii, G. tumida, N. dutertrei, G. crassaformis, and P. obliquiloculata), follow distinct evolutionary patterns at the two sites during the last 160 kyr. At the equatorial site (core MD 85668), downcore fluctuations in the relative abundances of the three groups are closely related to the glacial/interglacial cyclicity and provide some insights into the interpretation of hydrographic changes. The dominance of the mixed layer foraminifera at the transition intervals between isotope stages 6/5 and 2/1, combined with weak URI values, is thought to reflect the reorganization of the oceanographic circulation. These short-term events (with a duration of < 5000 year) could be related to the rapid inflow of oxygen-depleted water through the Indonesian straits as a result of sea level rise during deglaciation. Underneath the 5°N gyre (core MD 85674), the response to global climatic changes is overprinted by the regional effect of the Somalian upwelling, which has been persistent over the last 160 kyr.

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Concentrations of major ions, silicate and nutrients (total N and P) were measured in samples of surface water from 28 lakes in ice-free areas of northern Victoria Land (East Antarctica). Sixteen lakes were sampled during austral summers 2001/02, 2003/04, 2004/05 and 2005/06 to assess temporal variation in water chemistry. Although samples showed a wide range in ion concentrations, their composition mainly reflected that of seawater. In general, as the distance from the sea increased, the input of elements from the marine environment (through aerosols and seabirds) decreased and there was an increase in nitrate and sulfate concentrations. Antarctic lakes lack outflows and during the austral summer the melting and/or ablation of ice cover, water evaporation and leaching processes in dry soils determine a progressive increase in water ion concentrations. During the five-year monitoring survey, no statistically significant variation in the water chemistry were detected, except for a slight (hardly significant) increase in TN concentrations. However, Canonical Correspondence Analysis (CCA) indicated that other factors besides distance from the sea, the presence of nesting seabirds, the sampling time and percentage of ice cover affect the composition of water in Antarctic cold desert environments.

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En este trabajo se presentan resultados de un relevamiento realizado a los estudiantes de la UNLP a partir de una encuesta por muestreo aleatorio. Se realiza en primer término un análisis descriptivo general sobre las principales características de dicha población, y en segundo lugar un análisis exploratorio que intenta sintetizar perfiles de los estudiantes según algunas dimensiones socio-demográficas, institucionales e ideológicas, mediante la técnica multivariada del análisis de correspondencias múltiples

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En este trabajo se presentan resultados de un relevamiento realizado a los estudiantes de la UNLP a partir de una encuesta por muestreo aleatorio. Se realiza en primer término un análisis descriptivo general sobre las principales características de dicha población, y en segundo lugar un análisis exploratorio que intenta sintetizar perfiles de los estudiantes según algunas dimensiones socio-demográficas, institucionales e ideológicas, mediante la técnica multivariada del análisis de correspondencias múltiples

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A diatom-based sea-ice concentration (SIC) transfer function is developed using 72 surface samples from west of Greenland and around Iceland, and through comparison with the associated modern SIC. Canonical correspondence analysis on surface sediment diatoms and monthly average of SIC reveals that April SIC is the most important environmental factor controlling the distribution of diatoms in the area, and permits the development of a diatom-based SIC transfer function. The consistency between reconstructed SIC based on diatoms from West Greenland and the instrumental and documentary data during the last ~75 years demonstrates that the diatom-based SIC reconstruction is reliable for studying the palaeoceanography off West Greenland. Relatively warm conditions with strong influence of the Irminger Current (IC) are indicated for the early part of the record (~5000-3860 cal. yr BP), corresponding in time to the latest part of the Holocene Thermal Maximum. The April SIC oscillated around the mean value between 3860 and 1510 cal. yr BP and was above mean afterwards, particularly during the time interval 1510-1120 cal. yr BP and after 650 cal. yr BP, indicating more extensive sea-ice cover in Disko Bugt. A high degree of consistency between the reconstructed April SIC and changes in the diatom species suggests that the sea-ice condition in Disko Bugt is strongly influenced by variations in the relative strength of two components of the West Greenland Current, i.e. the cold East Greenland Current and the relatively warm IC.

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En este trabajo se presentan resultados de un relevamiento realizado a los estudiantes de la UNLP a partir de una encuesta por muestreo aleatorio. Se realiza en primer término un análisis descriptivo general sobre las principales características de dicha población, y en segundo lugar un análisis exploratorio que intenta sintetizar perfiles de los estudiantes según algunas dimensiones socio-demográficas, institucionales e ideológicas, mediante la técnica multivariada del análisis de correspondencias múltiples

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Deep-sea benthic foraminiferal assemblages from Ocean Drilling Program (ODP) Site 1143 located in the southern South China Sea (SCS) were investigated to evaluate the relationship between faunal composition patterns and paleoceanographic changes during the last 6 million years (late Miocene to Holocene). We used multivariate statistics (correspondence analysis) to analyze carbon-flux-related changes in assemblage composition of benthic foraminifers. Additional proxies for carbon flux and deep-water ventilation include delta13C records of epifaunal Cibicidoides wuellerstorfi and infaunal Uvigerina peregrina var. dirupta and Melonis pompilioides, benthic foraminiferal accumulation rates (BFARs), diversity indices, and relative abundances of indicator species. We observe three significant benthic faunal changes in the southern South China Sea during the last 6 million years. Strong fluctuations in BFAR and relative abundance of productivity indicator species between glacial and interglacial stages after the mid-Pleistocene revolution (MPR) at approximately 0.9 Ma, indicating stronger seasonal carbon flux fluctuations, are accompanied by the extinction of such species as Stilostomella spp. Increases in carbon flux indicator species are coupled with an overall decrease in benthic foraminifer diversity around 3.0 Ma in the late Pliocene. This may indicate increasing carbon flux in a period of productivity maximum caused by enhanced offshore upwelling from intensified winter monsoon wind strength.

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Palynological analyses were performed on 53 surface sediment samples from the North Pacific Ocean, including the Bering and Okhotsk Seas (37-64°N, 144°E-148°W), in order to document the relationships between the dinocyst distribution and sea-surface conditions (temperatures, salinities, primary productivity and sea-ice cover). Samples are characterized by concentrations ranging from 18 to 143816 cysts/cm**3 and the occurrence of 32 species. A canonical correspondence analysis (CCA) was carried out to determine the relationship between environmental variables and the distribution of dinocyst taxa. The first and second axes represent, respectively, 47% and 17.8% of the canonical variance. Axis 1 is positively correlated with all parameters except to the sea-ice and primary productivity in August, which are on the negative side. Results indicate that the composition of dinocyst assemblages is mostly controlled by temperature and that all environmental variables are correlated together. The CCA distinguishes 3 groups of dinocysts: the heterotrophic taxa, the genera Impagidinium and Spiniferites as well as the cyst of Pentapharsodinium dalei and Operculodinium centrocarpum. Five assemblage zones can be distinguished: 1) the Okhotsk Sea zone, which is associated to temperate and eutrophic conditions, seasonal upwellings and Amur River discharges. It is characterized by the dominance of O. centrocarpum, Brigantedinium spp. and Islandinium minutum; 2) the Western Subarctic Gyre zone with subpolar and mesotrophic conditions due to the Kamchatka Current and Alaska Stream inflows. Assemblages are dominated by Nematosphaeropsis labyrinthus, Pyxidinopsis reticulata and Brigantedinium spp.; 3) the Bering Sea zone, depicting a subpolar environment, influenced by seasonal upwellings and inputs from the Anadyr and Yukon Rivers. It is characterized by the dominance of I. minutum and Brigantedinium spp.; 4) the Alaska Gyre zone with temperate conditions and nutrient-enriched surface waters, which is dominated by N. labyrinthus and Brigantedinium spp. and 5) the Kuroshio Extension-North Pacific-Subarctic Current zone characterized by a subtropical and oligotrophic environment, which is dominated by O. centrocarpum, N. labyrinthus and warm taxa of the genus Impagidinium. Transfer functions were tested using the modern analog technique (MAT) on the North Pacific Ocean (= 359 sites) and the entire Northern Hemisphere databases ( = 1419 sites). Results confirm that the updated Northern Hemisphere database is suitable for further paleoenvironmental reconstructions, and the best results are obtained for temperatures with an accuracy of +/-1.7 °C.

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Most species of Late Cretaceous deep-sea benthic foraminifera are believed to be cosmopolitan and therefore to exhibit only minor biogeographical differences. In this preliminary report, six Deep Sea Drilling Project (DSDP) sites from different oceans, paleolatitudes, and paleodepths were analyzed for terminal Cretaceous abyssal-bathyal benthic foraminifera in order to investigate their assumed cosmopolitan distribution and the question of whether different faunal compositions are related to time, different paleolatitudes, and/or different paleodepths. The material studied was obtained from the low-latitude Site 465 (Pacific Ocean), and the intermediate-latitude Sites 384 (North Atlantic) and 356, 516, 525, and 527 (South Atlantic). The material analyzed represents a time slice encompassing the last 20-50 k.y. of the Cretaceous. The faunas contain numerous "Velasco-type" species, such as Gavelinella beccariiformis (White), Cibicidoides velascoensis (Cushman), Nuttallides truempyi (Nuttall), Gaudryina pyramidata Cushman, and various gyroidinoids and buliminids. The results contradict the general assumption of the cosmopolitan nature of Late Cretaceous deep-sea benthic foraminifera advocated in the literature. Only about 9% of the taxa identified were found to be truly "cosmopolitan" through their occurrence at all the sites analyzed. On the basis of correspondence analysis and relative abundance data, three assemblages and three subassemblages were recognized: (1) a bathyal-abyssal assemblage [Nuttallinella sp. A, Cibicidoides hyphalus (Fisher), Valvalabamina sp. evolute form, and Gyroidinoides spp.] at the South Atlantic Sites 356, 516, 525, and 527, divided into three subassemblages, namely (a) a middle bathyal subassemblage [Eouvigerina subsculptura McNeil and Caldwell, Truaxia aspera (Cushman), and G. pyramidata] at Sites 516 and 525, (b) a lower bathyal subassemblage [Osangularia? sp., Pyramidina rudita (Cushman and Parker), and Quadrimorphina camerata (Brotzen)] at Site 356, and (c) an abyssal subassemblage [Gyroidinoides sp. C, Hyperammina-Bathysiphon, Gyroidinoides beisseli (White), and Globorotalites sp. B] at Site 527; (2) an abyssal assemblage [Buliminella cf. plana (Cushman and Parker) and Bulimina incisa Cushman] at the North Atlantic Site 384; and (3) a middle bathyal assemblage [Vulvulina sp. A, Osangularia navarroana (Cushman), Alabamina? sp., Bulimina velascoensis (Cushman), Spiroplectammina spp. calcareous forms, and Bulimina trinitatensis Cushman and Jarvis] at the Pacific Site 465.

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Total concentrations of algal pigments, organic C, C, N, P and S were determined in surface sediments from the littoral zone of 21 lakes in ice-free areas of northern Victoria Land (Antarctica) with different climatic and environmental conditions. Concentrations of major ions and nutrients were also determined in water samples from the same lakes. The latter samples had extremely variable chemical compositions; however, all the lakes resulted oligotrophic. Pigment concentrations in surface sediments were comparable to those reported for other Antarctic lakes and lower than those in oligotrophic lakes at lower latitudes. Cyanophyta, Chlorophyta and Bacillariophyta were the main taxa identified. These taxa correspond to those reported in previous microscopy-based studies on Antarctic phytoplankton and phytobenthos. Discriminant Function Analysis and Canonical Correspondence Analysis of data indicate that the distribution of pigments in these Victoria Land lakes depends mainly on their geographical location (particularly the distance from the sea) and nutrient status.

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This study involves samples of Santonian to Eocene age (Cores 516F-125 to 516F-38) taken from the Rio Grande Rise in the South Atlantic Ocean. These samples are from DSDP Site 516 occupied during Leg 72 of the Glomar Challenger (details given in site chapter, Site 516, this volume). Only Santonian to Paleocene cores have been well sampled, and analyses of the Eocene samples are preliminary results. Results of the trace element analyses (Mg, Sr, Mn, Ni, Fe, Na, K) of the carbonate fraction and CaCO3 percentage for each sample can be found in Renard and others (1983). Whole geochemical data are treated by the statistical method of correspondence analysis. Oxygen and carbon isotopic ratios measured on samples close to the Cretaceous/Tertiary boundary are not used in this study.