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Longitudinal Profiles (longitudinal + profile)

Distribution by Scientific Domains

Medical Sciences	25%
Life Sciences	25%

Selected Abstracts

Longitudinal profile of antibodies against SARS-coronavirus in SARS patients and their clinical significance

RESPIROLOGY, Issue 1 2006
Hongying MO
Background: Severe acute respiratory syndrome (SARS) is a newly discovered disease caused by a novel coronavirus. The present study studied the longitudinal profile of antibodies against SARS-coronavirus (SARS-CoV) in SARS patients and evaluated the clinical significance of these antibodies. Methods: Two methods, ELISA and indirect immunofluorescent assay, were used for the detection of the anti-SARS-CoV IgG and IgM in 335 serial sera from 98 SARS patients. In 18 patients, serum antibody profiles were investigated and antibody neutralization tests were performed from 7 to 720 days after the onset of symptoms. Results: The ratios of positive IgG/IgM by ELISA were 0/0, 45.4/39.4, 88.6/71.4, 96/88, 100/48.6, 100/30.9, 100/17.1, 100/0 per cent, respectively, on 1,7, 8,14, 15,21, 22,28, 29,60, 61,90, 91,180 and 181,720 days after the onset of symptoms. Antibodies were not detected within the first 7 days of illness, but IgG titre increased dramatically on day 15, reaching a peak on day 60, and remained high until day 180 from when it declined gradually until day 720. IgM was detected on day 15 and rapidly reached a peak, then declined gradually until it was undetectable on day 180. Neutralizing viral antibodies were demonstrated in the convalescence sera from SARS patients. Conclusion: The persistence of detectable IgG antibodies and neutralizing viral antibodies for up to 720 days suggest that SARS patients may be protected from recurrent SARS-CoV infection for up to 2 years. [source]

On the relationship between hydrographs and chemographs

HYDROLOGICAL PROCESSES, Issue 14 2006
Andreas Kurtenbach
Abstract The spatial representativeness of gauging stations was investigated in two low-mountainous river basins near the city of Trier, southwest Germany. Longitudinal profiles during low and high flow conditions were sampled in order to identify sources of solutes and to characterize the alteration of flood wave properties during its travel downstream. Numerous hydrographs and chemographs of natural flood events were analysed in detail. Additionally, artificial flood events were investigated to study in-channel transport processes. During dry weather conditions the gauging station was only representative for a short river segment upstream, owing to discharge and solute concentrations of sources contiguous to the measurement site. During artificial flood events the kinematic wave velocity was considerably faster than the movement of water body and solutes, refuting the idea of a simple mixing process of individual runoff components. Depending on hydrological boundary conditions, the wave at a specific gauge could be entirely composed of old in-channel water, which notably reduces the spatial representativeness of a sampling site. Natural flood events were characterized by a superimposition of local overland flow, riparian water and the kinematic wave process comprising the downstream conveyance of solutes. Summer floods in particular were marked by a chronological occurrence of distinct individual runoff components originating only from a few contributing areas adjacent to the stream and gauge. Thus, the representativeness of a gauge for processes in the whole basin depends on the distance of the nearest significant source to the station. The consequence of our study is that the assumptions of mixing models are not satisfied in river basins larger than 3 km2. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Fish assemblages as influenced by environmental factors in streams in protected areas of the Czech Republic

ECOLOGY OF FRESHWATER FISH, Issue 1 2006
M. Humpl
Abstract,,, Three streams of comparable size located in different landscape-protected areas were selected for studying the effect of environmental factors on fish assemblages using indirect (detrended correspondence analysis, DCA) and direct (canonical correspondence analysis, CCA) gradient analysis. DCA of species showed well a gradient of assemblage changes in the longitudinal profile. DCA of sites stressed the variability between the fish assemblages of the three streams. This pattern was then confirmed by the highly significant between-stream CCA. In the within-site CCA, environmental factors explained 50.7% variability for presence,absence data and 58.3% for the relative abundance data. The analysis revealed that number of ponds and land use are the most influential factors of the strongest environmental gradient. However, in the partial CCAs, factor substratum type explained the largest proportion of the variability affecting fish in their habitat choice. Generally, presence,absence and relative abundance data of fish gave similar results in both DCA and CCA analyses; the same environmental factors proved to be important in both data type analyses. The environmental factors explain more variability than the regional (between-stream) one. The total proportion of variability explained by the presence,absence data analysis was 71.9% and in the relative abundance analysis even 80.8%. The environmental factors measured during the field survey explain 2.1- and 3.4-times more assemblages' variability than factors measured from a hydrological map. Resumen 1. Tres ríos de tamaño comparable localizados en diferentes áreas de paisaje protegido de la República Checa fueron seleccionados para estudiar el efecto de factores ambientales sobre los ensamblajes de peces. Para ello, utilizando análisis de gradientes indirectos (DCA) y directos (CCA). 2. El DCA para las especies enfatizó la variabilidad entre los ensamblajes de peces de los tres ríos. Este patrón fue confirmado por un CCA altamente significativo. Para la variabilidad dentro de la localidad, un CCA reveló que los factores ambientales explicaron un 50.7% para datos de presencia-ausencia y un 58.3% para las abundancias relativas. 3. Los análisis revelaron que el número de pozas y el uso del suelo fueron los factores de mayor influencia en el gradiente ambiental. Sin embargo, en el CCA parcial, el tipo de sustrato explicó la mayor proporción de la variabilidad que afecta a los peces en la elección de hábitat. 4. Generalmente los datos de presencia-ausencia y abundancia relativa produjeron resultados similares tanto en los análisis DCA como en los CCA; los mismos factores ambientales probaron ser importantes en los análisis de ambos tipos de datos. Los factores ambientales explicaron mas variabilidad que los regionales (entre ríos). La proporción total de variabilidad explicada por el análisis de los datos de presencia-ausencia fue 71.9% mientras que para las abundancias relativas fue de 80.8%. Los factores ambientales medidos durante los muestreos de campo explicaron 2.1 y 3.4 veces mas variabilidad que los factores medidos sobre mapas hidrológicos. [source]

An empirical model of carbon fluxes in Russian tundra

GLOBAL CHANGE BIOLOGY, Issue 2 2001
Dmitri G. Zamolodchikov
Summary This study presents an empirical model based on a GIS approach, which was constructed to estimate the large-scale carbon fluxes over the entire Russian tundra zone. The model has four main blocks: (i) the computer map of tundra landscapes; (ii) data base of long-term weather records; (iii) the submodel of phytomass seasonal dynamics; and (iv) the submodel of carbon fluxes. The model uses exclusively original in situ diurnal CO2 flux chamber measurements (423 sample plots) conducted during six field seasons (1993,98). The research sites represent the main tundra biome landscapes (arctic, typical, south shrub and mountain tundras) in the latitudinal diapason of 65,74°N and longitudinal profile of 63°E,172°W. The greatest possible diversity of major ecosystem types within the different landscapes was investigated. The majority of the phytomass data used was obtained from the same sample plots. The submodel of carbon fluxes has two dependent [GPP, Gross Respiration (GR)] and several input variables (air temperature, PAR, aboveground phytomass components). The model demonstrates a good correspondence with other independent regional and biome estimates and carbon flux seasonal patterns. The annual GPP of Russian tundra zone for the area of 235 × 106 ha was estimated as ,485.8 ± 34.6 × 106 tC, GR as +474.2 ± 35.0 × 106 tC, and NF as ,11.6 ± 40.8 × 106 tC, which possibly corresponds to an equilibrium state of carbon balance during the climatic period studied (the first half of the 20th century). The results advocate that simple regression-based models are useful for extrapolating carbon fluxes from small to large spatial scales. [source]

Retracted and replaced: A modelling study of hyporheic exchange pattern and the sequence, size, and spacing of stream bedforms in mountain stream networks, Oregon, USA

HYDROLOGICAL PROCESSES, Issue 15 2005
Michael N. Gooseff
Abstract This article has been retracted and replaced. See Retraction and Replacement Notice DOI: 10.1002/hyp.6350 Studies of hyporheic exchange flows have identified physical features of channels that control exchange flow at the channel unit scale, namely slope breaks in the longitudinal profile of streams that generate subsurface head distributions. We recently completed a field study that suggested channel unit spacing in stream longitudinal profiles can be used to predict the spacing between zones of upwelling (flux of hyporheic water into the stream) and downwelling (flux of stream water into the hyporheic zone) in the beds of mountain streams. Here, we use two-dimensional groundwater flow and particle tracking models to simulate vertical and longitudinal hyporheic exchange along the longitudinal axis of stream flow in second-, third-, and fourth-order mountain stream reaches. Modelling allowed us to (1) represent visually the effect that the shape of the longitudinal profile has on the flow net beneath streambeds; (2) isolate channel unit sequence and spacing as individual factors controlling the depth that stream water penetrates the hyporheic zone and the length of upwelling and downwelling zones; (3) evaluate the degree to which the effects of regular patterns in bedform size and sequence are masked by irregularities in real streams. We simulated hyporheic exchange in two sets of idealized stream reaches and one set of observed stream reaches. Idealized profiles were constructed using regression equations relating channel form to basin area. The size and length of channel units (step size, pool length, etc.) increased with increasing stream order. Simulations of hyporheic exchange flows in these reaches suggested that upwelling lengths increased (from 2·7 m to 7·6 m), and downwelling lengths increased (from 2·9 m to 6·0 m) with increase in stream order from second to fourth order. Step spacing in the idealized reaches increased from 5·3 m to 13·7 m as stream size increased from second to fourth order. Simulated upwelling lengths increased from 4·3 m in second-order streams to 9·7 m in fourth-order streams with a POOL,RIFFLE,STEP channel unit sequence, and increased from 2·5 m to 6·1 m from second- to fourth-order streams with a POOL,STEP,RIFFLE channel unit sequence. Downwelling lengths also increased with stream order in these idealized channels. Our results suggest that channel unit spacing, size, and sequence are all important in determining hyporheic exchange patterns of upwelling and downwelling. Though irregularities in the size and spacing of bedforms caused flow nets to be much more complex in surveyed stream reaches than in idealized stream reaches, similar trends emerged relating the average geomorphic wavelength to the average hyporheic wavelength in both surveyed and idealized reaches. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Longitudinal profile of antibodies against SARS-coronavirus in SARS patients and their clinical significance

Lithological and fluvial controls on the geomorphology of tropical montane stream channels in Puerto Rico

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 12 2010
Andrew S. Pike
Abstract An extensive survey and topographic analysis of five watersheds draining the Luquillo Mountains in north-eastern Puerto Rico was conducted to decouple the relative influences of lithologic and hydraulic forces in shaping the morphology of tropical montane stream channels. The Luquillo Mountains are a steep landscape composed of volcaniclastic and igneous rocks that exert a localized lithologic influence on the stream channels. However, the stream channels also experience strong hydraulic forcing due to high unit discharge in the humid rainforest environment. GIS-based topographic analysis was used to examine channel profiles, and survey data were used to analyze downstream changes in channel geometry, grain sizes, stream power, and shear stresses. Results indicate that the longitudinal profiles are generally well graded but have concavities that reflect the influence of multiple rock types and colluvial-alluvial transitions. Non-fluvial processes, such as landslides, deliver coarse boulder-sized sediment to the channels and may locally determine channel gradient and geometry. Median grain size is strongly related to drainage area and slope, and coarsens in the headwaters before fining in the downstream reaches; a pattern associated with a mid-basin transition between colluvial and fluvial processes. Downstream hydraulic geometry relationships between discharge, width and velocity (although not depth) are well developed for all watersheds. Stream power displays a mid-basin maximum in all basins, although the ratio of stream power to coarse grain size (indicative of hydraulic forcing) increases downstream. Excess dimensionless shear stress at bankfull flow wavers around the threshold for sediment mobility of the median grain size, and does not vary systematically with bankfull discharge; a common characteristic in self-forming ,threshold' alluvial channels. The results suggest that although there is apparent bedrock and lithologic control on local reach-scale channel morphology, strong fluvial forces acting over time have been sufficient to override boundary resistance and give rise to systematic basin-scale patterns. Copyright © 2010 John Wiley and Sons, Ltd. [source]

Recent channel adjustments in alluvial rivers of Tuscany, central Italy

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 6 2003
Massimo RinaldiArticle first published online: 19 JUN 200
Abstract Drastic channel adjustments have affected the main alluvial rivers of Tuscany (central Italy) during the 20th century. Bed-level adjustments were identified both by comparing available topographic longitudinal profiles of different years and through field observations. Changes in channel width were investigated by comparing available aerial photographs (1954 and 1993,98). Bed incision represents the dominant type of vertical adjustment, and is generalized along all the fluvial systems investigated. The Arno River system is the most affected by bed-level lowering (up to 9 m), whereas lower incision (generally less than 2 m) is observed along the rivers of the southern part of the region. Human disturbances appear to be the dominant factors of adjustments: the main phase of vertical change occurred during the period 1945,80, in concomitance with the phase of maximum sediment mining activity at the regional scale. The second dominant type of adjustment that involved most of the rivers in the region consists of a narrowing of the active channel. Based on measurements of channel width conducted on aerial photographs, 38% of the reaches analysed experienced a narrowing greater than 50% of the initial channel width. The largest values of channel narrowing were observed along initially braided or sinuous with alternate bars morphologies in the southern portion of the region. A regional scheme of channel adjustments is derived, based on initial channel morphology and on the amounts of incision and narrowing. Different styles of channel adjustments are described. Rivers that were originally sinuous with alternate bars to braided generally became adjusted by a moderate incision and a moderate to intense narrowing; in contrast, sinuous-meandering channels mainly adjusted vertically, with a minor amount of narrowing. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Retracted and replaced: A modelling study of hyporheic exchange pattern and the sequence, size, and spacing of stream bedforms in mountain stream networks, Oregon, USA

Mixed stream channel morphologies: implications for fish community diversity

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2009
Christina M. Cianfrani
Abstract 1.Stream classification systems are widely used in stream management and restoration. Whereas the principal morphological types of these classification systems are increasingly recognized for their ecological connections, the roles of intermediate and mixed morphologies are still poorly understood, yet may be biologically significant. 2.Twenty-five stream reaches in north-western Vermont were classified by channel morphology to determine whether fish community diversity differed among pool-riffle, mixed (i.e. pool-riffle/cascade, pool-riffle/other) and forced pool-riffle stream morphological groups. Stream reach surveys included cross-sectional surveys, longitudinal profiles, bed substrate characterization, and fish surveys. 3.Three fish community diversity measures were calculated: (1) species richness (S); (2) Shannon,Weaver Index (H,); and (3) Simpson's Index (1/D). Multivariate analysis of covariance (MANCOVA) followed by analysis of variance (ANOVA) were used to explore potential differences in fish diversity among stream morphological groups. Fish diversity was significantly different for all three community diversity measures (P,0.05), with pool-riffle/cascade morphology consistently exhibiting the greatest fish diversity and forced pool-riffle the lowest. 4.These results suggest that fish community diversity is significantly associated with distinct channel morphologies. Generally, pool-riffle/cascade and pool-riffle/other stream morphological groups supported habitats that fostered greater species diversity than more homogeneous and uniform pool-riffle reaches. The observed patterns of diversity are likely to be the result of habitat patches created by variations in flow and other physical characteristics in reaches of mixed morphologies. 5.These results support fish sampling schemes that incorporate morphological heterogeneity, such as proportional-distance designation. Sampling strategies that focus on homogeneous reaches may underestimate diversity, and misrepresent stream condition when fish community data are used in indices of biological integrity (IBIs). Reaches of mixed stream morphologies should be recognized as areas of biological importance in stream and catchment management and in conservation efforts. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Conditional Estimation for Generalized Linear Models When Covariates Are Subject-Specific Parameters in a Mixed Model for Longitudinal Measurements

BIOMETRICS, Issue 1 2004
Erning Li
Summary. The relationship between a primary endpoint and features of longitudinal profiles of a continuous response is often of interest, and a relevant framework is that of a generalized linear model with covariates that are subject-specific random effects in a linear mixed model for the longitudinal measurements. Naive implementation by imputing subject-specific effects from individual regression fits yields biased inference, and several methods for reducing this bias have been proposed. These require a parametric (normality) assumption on the random effects, which may be unrealistic. Adapting a strategy of Stefanski and Carroll (1987, Biometrika74, 703,716), we propose estimators for the generalized linear model parameters that require no assumptions on the random effects and yield consistent inference regardless of the true distribution. The methods are illustrated via simulation and by application to a study of bone mineral density in women transitioning to menopause. [source]

Microstructural alterations of the retinal arterial blood column along the vessel axis in healthy volunteers with age

ACTA OPHTHALMOLOGICA, Issue 2009
IM LANZL
Purpose We demonstrated previously that roughness of the retinal arterial blood column measured along the vessel axis increases in anamnestically healthy volunteers with increasing age. We termed it longitudinal retinal arterial profile (LAP). Whether LAP is altered with age in medically supervised healthy persons is investigated. Methods 82 medically healthy volunteers were examined by Dynamic Vessel Analyzer (IMEDOS, Jena, Germany) using stimulation with flickering light. 3 age groups were formed: young (N=27, 30,5±4,3 years), middle age (N=28, 42,3±3,3 years) and seniors (N=27, 64,0±5,0 years). Included in the analysis were volunteers without medical vascular risk factors defined as: blood pressure < 140/90 mmHg, HDL > 35 mg/dl, LDL < 190 mg/dl and glucose levels < 110 mg/dl. Retinal arterial diameters were measured along 1 mm vessel segments to obtain LAP. Differences were analyzed using Fourier transformation. Results In all age groups LAP do not change during all stages of the arterial response. Arterial diameters in the senior group were reduced in comparison to the young group at all stages of the vessel reaction (p<0,05). There are differences in LAP between the age groups. Compared to young persons, seniors showed significantly diminished waves with a period of 417 µm at all stages of the arterial reaction, whereas young volunteers showed less pronounced waves with a period of 208 µm (p<0,05). Conclusion Our results represent the healthy aging process in retinal vasculature. Age related microstructural changes in longitudinal profiles of retinal arteries in medically healthy persons might be an indication for alterations in the vascular endothelium and smooth musculature. [source]