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Increasing Depth (increasing + depth)
Selected AbstractsThe distribution and prevalence of sponges in relation to environmental gradients within a temperate sea lough: vertical cliff surfacesDIVERSITY AND DISTRIBUTIONS, Issue 6 2000James J. Bell Abstract. The prevalence and distribution of sponges was surveyed on vertical cliff surfaces at Lough Hyne Marine Nature Reserve, Co. Cork, Ireland. The number of sponge species was recorded at 6-metre depth intervals at four sites within Lough Hyne, and at one site on the adjacent Atlantic coastline to examine differences in abundance and zonation patterns. Sites ranged from an exposed turbulent regime to sheltered, sedimented environments. Individual species showed different distributions and prevalence between sites and with increasing depth. Greatest differences were observed between the most- and least-disturbed sites. Distinct sponge zonation patterns were evident at all sites sampled. Twenty-five species were considered dominant at all five sites with the remaining 48 species considered rare. Only four of the 25 most-dominant species occurred at the site experiencing the most turbulent flow conditions, whereas 12 species were found at the site of unidirectional fast flow. At sites of moderate to slight water movement and high sedimentation, between 18 and 24 of the most dominant species were present. Encrusting forms constituted high proportions of sponge communities at all five sites sampled (although consisting of different species). At sites of turbulent and unidirectional fast flow massive forms also dominated whereas at the least turbulent sites, where sedimentation was high, arborescent sponges were abundant. Few species showed exclusive distribution to a single depth and site, but there was some degree of correlation between species distributions and abiotic factors such as sedimentation rate and flow regimes. Sponge distributions and densities are discussed with respect to the suitability of species' morphologies to particular environments, intra-specific and inter-specific competition and physiological adaptations that enable them to survive in different habitats. [source] Soil production in heath and forest, Blue Mountains, Australia: influence of lithology and palaeoclimateEARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2005Marshall T. Wilkinson Abstract An Erratum has been published for this article in Earth Surfaces Processes and Landforms 25(13) 2005, 1683,1686. Recent determinations of soil production from in situ cosmogenic nuclides indicate that production decreases exponentially with soil depth. This contrasts with a long-held assumption that maximum soil production occurs under a soil cover of finite depth. Sites in the Blue Mountains, Australia, show a sharp decrease of soil depth where vegetation changes from forested plateau surfaces to heath-covered spurs, and bands of bare rock in the heath suggest that soil production depends on presence of a finite depth of soil. The substrate varies from hard ferruginized sandstone to soft saprolite. In situ 10Be determinations indicate that apparent rates of erosion and soil production are greater under the relatively thin heath soil than under the thicker forest soil but, in contrast to other studies, these sites do not show significant depth-dependence of apparent soil production. The pattern reflects both hardness variation in the rock substrate and the effect of Late Quaternary climatic change. Optically stimulated luminescence (OSL) dating indicates that soil ,30 cm depth is of Holocene age whereas the deeper soil is substantially older. The age-break coincides with a stone line interpreted as a former surface lag deposit. Assuming that pre-Holocene soil depths were 30 cm less than today, recalculated soil production tends to decrease with increasing depth. Soil production at this site requires soil cover but bare rock patches and vegetation comprise a shifting mosaic. In the long term, average rates of erosion and soil production decrease with increasing soil depth. Copyright © 2005 John Wiley & Sons, Ltd. [source] Temporal denitrification patterns in different horizons of two riparian soilsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2003A-C. Cosandey Summary The dynamics of biological denitrification in riparian soil is still poorly understood. We studied the spring-time pattern of denitrifying enzyme activity (DEA) and the rate of denitrification (DNT) in two hydromorphic riparian soils, one a mollic Gleysol and the other a terric Histosol. The average DEA ranged from 73 to 1232 ng N g,1 hour,1, and DNT ranged from 4 to 36 ng N g,1 hour,1. Both DEA and DNT diminished with increasing depth in both soil types. This decrease corresponded to a decrease in total and K2SO4 -extractable organic carbon and K2SO4 -extractable mineral nitrogen. The DEA and DNT differed in their dynamics. The former had no evident pattern in subsurface horizons but increased with temperature at the end of spring in surface and structural horizons. The DNT diminished as the soil dried in the mollic Gleysol when the water table fell. In the terric Histosol, the water table was still too high at the end of spring to affect the DNT. The results suggest that the vertical pattern of denitrification is related to that of organic carbon content. This organic carbon content determines biological activity and the supply of carbon and nitrous oxides. In biologically active horizons temperature drives the dynamics of DEA, whereas soil moisture drives the dynamics of DNT. Our results show the importance of the dynamic soil,water relationship in controlling denitrification within the riparian zone. [source] The inherent ,safety-net' of an Acrisol: measuring and modelling retarded leaching of mineral nitrogenEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2002D. Suprayogo Summary The inherent features of Acrisols with their increasing clay content with depth are conducive to reducing nutrient losses by nutrient adsorption on the matrix soil surfaces. Ammonium (NH4+) and nitrate (NO3,) adsorption by a Plinthic Acrisol from Lampung, Indonesia was studied in column experiments. The peak of the H218O breakthrough occurred at 1 pore volume, whereas the median pore volumes for NH4+ and NO3, ranged from 6.4 to 6.9 and 1.1 to 1.6, respectively. The adsorption coefficients (Ka in cm3 g,1) measured were 1.81, 1.51, 1.64 and 1.47 for NH4+ and 0.03, 0.09, 0.10 and 0.17 for NO3,, respectively, in the 0,0.2, 0.2,0.4, 0.4,0.6 and 0.6,0.8 m soil depth layers. The NH4+ and NO3, adsorption coefficients derived from this study were put in to the Water, Nutrient and Light Capture in Agroforestry Systems (WaNuLCAS) model to evaluate their effect on leaching in the context of several cropping systems in the humid tropics. The resulting simulations indicate that the inherent ,safety-net' (retardation mechanism) of a shallow (0.8,1 m) Plinthic Acrisol can reduce the leaching of mineral N by between 5 and 33% (or up to 2.1 g m,2), mainly due to the NH4+ retardation factor, and that the effectiveness in reducing N leaching increases with increasing depth. However, the inherent ,safety-net' is useful only if deep-rooted plants can recover the N subsequently. [source] Distribution of microbial biomass and phospholipid fatty acids in Podzol profiles under coniferous forestEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2000H. Fritze Summary Microbial-derived phospholipid fatty acids (PLFAs) can be used to characterize the microbial communities in soil without the need to isolate individual fungi and bacteria. They have been used to assess microbial communities of humus layers under coniferous forest, but nothing is known of their distribution in the deeper soil. To investigate the vertical distribution we sampled nine Podzol profiles on a 100-m-long transect in a coniferous forest and analysed for their microbial biomass and PLFA pattern to a depth of 0.4 m. The transect covered a fertility gradient from Vaccinium vitis-idaea forest site type to Vaccinium myrtillus forest site type. The cores were divided into humus (O) and eluvial (E) layers and below that into 10-cm sections and designated as either illuvial (B) or parent material (C), or as a combination (BC). Two measures of microbial biomass analyses were applied: substrate-induced respiration (SIR) to determine microbial biomass C (Cmic), and the sum of the extracted microbial-derived phospholipid fatty acids (totPLFA). The soil fertility had no effect on the results. The Cmic correlated well with totPLFA (r=,0.86). The microbial biomass decreased with increasing depth. In addition the PLFA pattern changed with increased depth as assessed with principal component analysis, indicating a change in the microbial community structure. The composition of the PLFAs in the O layer differed from that in the E layer and both differed from the upper part of the B layer and from the rest of the BC layers. The deeper parts of the B layer (BC1, BC2 and BC3) were similar to one other. The O layer had more 18:2,6, a PLFA indicator of fungi, whereas the E layer contained relatively more of the PLFAs 16:1,9, 18:1,7 and cy19:0 common in gram-negative bacteria. With increased depth the relative amount of 10Me18:0, the PLFA indicator for actinomycetes, increased. We conclude that the PLFA method is a promising discriminator between the microbial community structures of the horizons in Podzols. [source] Fossilized embryos are widespread but the record is temporally and taxonomically biasedEVOLUTION AND DEVELOPMENT, Issue 2 2006Philip C. J. Donoghue SUMMARY We report new discoveries of embryos and egg capsules from the Lower Cambrian of Siberia, Middle Cambrian of Australia and Lower Ordovician of North America. Together with existing records, embryos have now been recorded from four of the seven continents. However, the new discoveries highlight secular and systematic biases in the fossil record of embryonic stages. The temporal window within which the embryos and egg capsules are found is of relatively short duration; it ends in the Early Ordovician and is roughly coincident with that of typical "Orsten"-type faunas. The reduced occurrence of such fossils has been attributed to reducing levels of phosphate in marine waters during the early Paleozoic, but may also be owing to the increasing depth of sediment mixing by infaunal metazoans. Furthermore, most records younger than the earliest Cambrian are of a single kind,large eggs and embryos of the priapulid-like scalidophoran Markuelia. We explore alternative explanations for the low taxonomic diversity of embryos recovered thus far, including sampling, size, anatomy, ecology, and environment, concluding that the preponderance of Markuelia embryos is due to its precocious development of cuticle at an embryonic stage, predisposing it to preservation through action as a substrate on which microbially mediated precipitation of authigenic calcium phosphate may occur. The fossil record of embryos may be limited to a late Neoproterozoic to early Ordovician snapshot that is subject to dramatic systematic bias. Together, these biases must be considered seriously in attempts to use the fossil record to arbitrate between hypotheses of developmental and life history evolution implicated in the origin of metazoan clades. [source] Characterisation of microbial community composition of a Siberian tundra soil by fluorescence in situ hybridisationFEMS MICROBIOLOGY ECOLOGY, Issue 1 2004Svenja Kobabe Abstract The bacterial community composition of the active layer (0,45 cm) of a permafrost-affected tundra soil was analysed by fluorescence in situ hybridisation (FISH). Arctic tundra soils contain large amounts of organic carbon, accumulated in thick soil layers and are known as a major sink of atmospheric CO2. These soils are totally frozen throughout the year and only a thin active layer is unfrozen and shows biological activity during the short summer. To improve the understanding of how the carbon fluxes in the active layer are controlled, detailed analysis of composition, functionality and interaction of soil microorganisms was done. The FISH analyses of the active layer showed large variations in absolute cell numbers and in the composition of the active microbial community between the different horizons, which is caused by the different environmental conditions (e.g., soil temperature, amount of organic matter, aeration) in this vertically structured ecosystem. Universal protein stain 5-(4,6-dichlorotriazin-2-yl)aminofluorescein (DTAF) showed an exponential decrease of total cell counts from the top to the bottom of the active layer (2.3 × 109,1.2 × 108 cells per gram dry soil). Using FISH, up to 59% of the DTAF-detected cells could be detected in the surface horizon, and up to 84% of these FISH-detected cells could be affiliated to a known phylogenetic group. The amount of FISH-detectable cells decreased with increasing depth and so did the diversity of ascertained phylogenetic groups. [source] Hosts and distribution of Collybia fusipes in France and factors related to the disease's severityFOREST PATHOLOGY, Issue 1 2002D. PIOU Using data collected by two different observation networks, it was possible to clarify the distribution of Collybia fusipes in France. It is frequently found in the western and northern parts of France, mainly on Quercus rubra and Quercus robur, and to a somewhat lesser extent on Quercus petraea. When the relative areas covered by these species are compared, it is evident that Q. rubra is much the most susceptible of the three species. The fungus has been less frequently reported in the south-eastern quarter of France, where Quercus ilex and Quercus pubescens are the dominant species. Complementary observations carried out at the National Arboretum of Les Barres indicate that a large number of oak species are susceptible to infection by this fungus, particularly those in the subgenus Erythrobalanus. These observations are discussed with reference to reports of this fungus throughout Europe. In a Q. rubra stand, fruit-body clumps were monitored and root damage was assessed on 73 final-crop trees and 40 codominant trees. The results suggest that C. fusipes does not preferentially infect weakened trees. Both the severity of root damage and the number of fruit-body clumps increased with increasing depth to signs of waterlogging. Répartition et hôtes de Collybia fusipes en France et facteurs de gravité de la maladie D'après les données collectées par deux réseaux de surveillance distincts, la répartition de Collybia fusipes en France a été précisée. Le champignon est fréquent dans les moitiés ouest et nord du pays, principalement sur Quercus rubra et Q. robur, et dans une moindre mesure sur Q. petraea. Quand on considère la surface relative occupée par ces espèces, il apparaît évident que Q. rubra est le plus sensible. Il a été moins souvent signalé dans le quart sud-est oùQ. ilex et Q. pubescens sont dominants. Des observations complémentaires réalisées à l'Arboretum National des Barres indiquent qu'un grand nombre d'espèces de chênes sont susceptibles d'être attaquées par ce champignon, particulièrement celles du sous-genre Erythrobalanus. Ces observations sont discutées et comparées avec les données disponibles en Europe. L'apparition des carpophores a été suivie dans un peuplement de Q. rubra, et les dégâts aux racines ont étéévalués sur 73 arbres de place et 40 arbres codominants. Les résultats indiquent que C. fusipes n'infecte pas plus gravement les arbres affaiblis. Le degré d'hydromorphie influence significativement l'importance des dégâts racinaires ainsi que le nombre de carpophores produits. Cette étude confirme que C. fusipes se développe préférentiellement dans les sites où l'hydromorphie n'est pas trop sévère. Wirtspflanzen und Verbreitung von Collybia fusipes in Frankreich sowie mit der Krankheitsintensität assoziierte Umweltfaktoren Mit Hilfe der Daten von zwei unterschiedlichen Beobachtungsnetzwerken konnte die Verbreitung von Collybia fusipes in Frankreich präzisiert werden. Der Pilz ist im Westen und Norden des Landes häufig auf Quercus rubra und Quercus robur zu finden, etwas weniger häufig auf Quercus petraea. Beim Vergleich der von diesen Arten bestockten Flächen wird deutlich, dass Q. rubra die anfälligste der drei Eichenarten ist. Im südöstlichen Teil Frankreichs, wo Quercus ilex und Quercus pubescens dominieren, wurde der Pilz weniger häufig nachgewiesen. Ergänzende Beobachtungen im Arboretum National des Barres ergaben, dass zahlreiche Eichenarten gegen C. fusipes anfällig sind, insbesondere die des Subgenus Erythrobalanus. Diese Ergebnisse werden im Vergleich mit der aus Europa über diesen Pilz verfügbaren Literatur diskutiert. In einem Q. rubra, Bestand wurde das Auftreten von Fruchtkörpern und von Wurzelschäden an 73 herrschenden und 40 mitherrschenden Bäumen registriert. Die Ergebnisse zeigen, dass C. fusipes geschwächte Bäume nicht bevorzugt befällt. Sowohl die Intensität der Wurzelschäden als auch die Anzahl der Fruchtkörper erhöhte sich mit zunehmender Tiefe der Anzeichen für Staunässe im Bodenprofil. [source] Differences in seed mass between hydric and xeric plants influence seed bank dynamics in a dryland riparian ecosystemFUNCTIONAL ECOLOGY, Issue 2 2008J. C. Stromberg Summary 1Dryland riparian zones have steep spatial gradients of soil moisture and flood disturbance, and the component hydrogeomorphic surfaces support hydric to xeric plant species. These systems undergo extremes of flood and drought, a dynamic that may select for persistent soil seed banks. We asked if reliance on this strategy differed among plants in three moisture groups (hydric, mesic and xeric), and if patterns were related to diaspore traits. 2We assessed the composition of soil and litter seed banks (emergence method) and extant vegetation along a riparian hydrogradient, and measured seed persistence (using an indirect method) and diaspore mass and shape variance of the component species. 3Hydroriparian species had smaller diaspores than xeroriparian species, corresponding to differences in selective pressures on seedlings in their respective habitats, but the two groups formed persistent seed banks at approximately equal percentages. Persistent seeds were smaller than transient seeds, but within the persistent seed group there was separation between the smaller-diaspored hydrophytes and larger-diaspored xerophytes. 4Distribution patterns of extant vegetation, in concert with diaspore trait differences among moisture-affinity groups, gave rise to divergent spatial patterns of diaspores within the soil: hydroriparian diaspores were abundant not only along wet channel bars but also in deep soils under floodplain forests and shrublands, presumably owing to dispersal by flood waters. Xeroriparian diaspores were largely restricted to the litter and upper soil layers of their drier, higher, floodplain habitats. With increasing depth in the soil of floodplain forests and shrublands, viable diaspores became smaller and rounder, and plant composition shifted from xeroriparian to hydroriparian species. 5The wide distribution of hydroriparian diaspores in floodplain soils influences disturbance dynamics, increasing the probability that ephemeral wetland communities will develop wherever suitable conditions are stochastically created by floods. Persistent seed banks also allow many xeric annuals to be maintained in dryland riparian zones throughout extended drought, similar to processes that occur in desert uplands. [source] The influence of sward canopy structure on foraging decisions by grazing cattle.GRASS & FORAGE SCIENCE, Issue 2 2003Abstract Patch selection by grazing dairy cows in response to simultaneous variation in combinations of sward structural characteristics was examined in three experiments in which four mature dairy cows were offered a choice of patches (typically 0.9 m × 0.9 m) of perennial ryegrass (Lolium perenne) presented in a linear arrangement. Treatments involved combinations of variations in sward height, stubble height and/or depth of regrowth, prepared by preliminary cutting treatments. They were arranged in balanced sets of four to nine treatments, which were arranged in linear sequences of eighteen to twenty-seven patches. Within experiments, sequences were balanced across replicate sets of patches, which were grazed separately by individual cows. The number of bites removed and the residence time for each patch were highly correlated in all three experiments, and the results are reported using number of bites per patch as an estimator of foraging behaviour. In the first experiment, with vegetative swards, cows preferentially selected the tallest swards. When swards comprising reproductive stem were offered in Experiment 2, cows selectively grazed short-stubble swards rather than tall-stubble swards, although both offered a similar depth of regrowth. Cows did not exhibit preference for swards comprising the greatest quantity of leaf mass, indicating that the spatial distribution of plant components assumed greater importance. In the third experiment, the number of bites removed increased with increasing depth of regrowth, and was negatively correlated with sward height. The three patch-appraisal cues investigated were broadly ranked in order of importance as (i) depth of regrowth, (ii) sward maturity and (iii) sward height. There was no evidence, at least at a short temporal scale, that patch behaviour was influenced by conditions in adjacent patches, suggesting that the cows assessed grazing opportunities on a patch-by-patch basis. [source] Thermal influence of urban groundwater recharge from stormwater infiltration basinsHYDROLOGICAL PROCESSES, Issue 12 2009Arnaud Foulquier Abstract Groundwater warming below cities has become a major environmental issue; but the effect of distinct local anthropogenic sources of heat on urban groundwater temperature distributions is still poorly documented. Our study addressed the local effect of stormwater infiltration on the thermal regime of urban groundwater by examining differences in water temperature beneath stormwater infiltration basins (SIB) and reference sites fed exclusively by direct infiltration of rainwater at the land surface. Stormwater infiltration dramatically increased the thermal amplitude of groundwater at event and season scales. Temperature variation at the scale of rainfall events reached 3 °C and was controlled by the interaction between runoff amount and difference in temperature between stormwater and groundwater. The annual amplitude of groundwater temperature was on average nine times higher below SIB (range: 0·9,8·6 °C) than at reference sites (range: 0,1·2 °C) and increased with catchment area of SIB. Elevated summer temperature of infiltrating stormwater (up to 21 °C) decreased oxygen solubility and stimulated microbial respiration in the soil and vadose zone, thereby lowering dissolved oxygen (DO) concentration in groundwater. The net effect of infiltration on average groundwater temperature depended upon the seasonal distribution of rainfall: groundwater below large SIB warmed up (+0·4 °C) when rainfall occurred predominantly during warm seasons. The thermal effect of stormwater infiltration strongly attenuated with increasing depth below the groundwater table indicating advective heat transport was restricted to the uppermost layers of groundwater. Moreover, excessive groundwater temperature variation at event and season scales can be attenuated by reducing the size of catchment areas drained by SIB and by promoting source control drainage systems. Copyright © 2009 John Wiley & Sons, Ltd. [source] The zone of vegetation influence on baseflow revealed by diel patterns of streamflow and vegetation water use in a headwater basinHYDROLOGICAL PROCESSES, Issue 8 2002Barbara J. Bond Water use by vegetation can be closely linked to streamflow patterns on a variety of time scales. However, many of the details of these linkages are poorly understood. We compared diel (24 h) patterns of transpirational water use with streamflow patterns in a small headwater basin that displays a marked diel variation during summer months. The study site was in western Oregon. Our objectives were to: (1) determine the phase shift, i.e. the time lag between maximum transpiration and minimum streamflow, and the strength of the correlation at that time lag; (2) determine the amount of streamflow that is ,missing' during each diel cycle (i.e. the difference between base flow, defined by the daily maxima, and actual flow) and use it to estimate the zone, or area, of vegetation that influences daily streamflow patterns; (3) test and refine a conceptual model of how the coupling between vegetation water use and streamflow changes over the period of summer drought in this basin. We found that vegetation water use in the summer is coupled to streamflow over time scales of 4 to 8 h, and water-use-related fluctuations accounted for 1 to 6% of summer base flow. Direct evaporation from the channel was an order of magnitude less than the diel streamflow decrease. Transpiration within only 0·1 to 0·3% of the basin area accounted for the diel variation in streamflow. As the basin drained further through the summer, the coupling between vegetation and streamflow was diminished and occurred at longer time scales, and the zone of vegetation influence became smaller. This pattern is in accordance with our conceptual model, which attributes the summer decline in the strength of the vegetation,streamflow coupling to the increasing depth of plant-available water in the soil profile. Although this study is preliminary, we believe it is an important first step in describing better the coupling of vegetation water use to streamflow. Copyright © 2002 John Wiley & Sons, Ltd. [source] Parametric studies for heating performance of an earth to air heat exchanger coupled with a greenhouseINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 11 2005M. K. Ghosal Abstract A thermal model has been developed to investigate the potential of using the stored thermal energy of the ground for greenhouse heating with the help of an earth to air heat exchanger (EAHE) system integrated with the greenhouse located in the premises of IIT, Delhi, India. Experiments were conducted extensively during the winter period from November 2002 to March 2003, but the model developed was validated against the clear and sunny days. Parametric studies performed for EAHE coupled with the greenhouse illustrate the effects of buried pipe length, pipe diameter, mass flow rate of air, depth of ground and soil types on greenhouse air temperatures. Temperatures of greenhouse air with the experimental parameters of EAHE were found to be on an average 7,8°C more in the winter than the same greenhouse without EAHE. Greenhouse air temperatures increase in the winter with increasing pipe length, decreasing pipe diameter, decreasing mass flow rate of flowing air inside buried pipe and increasing depth of ground up to 4 m. Predicted and measured values of greenhouse air temperature, which were verified in terms of root mean square of percent deviation and correlation coefficient, exhibited fair agreement. Copyright © 2005 John Wiley & Sons, Ltd. [source] Incidence and severity of marine borer attack at different depths at Mtongwe Jetty Pontoon Mombasa, KenyaAFRICAN JOURNAL OF ECOLOGY, Issue 4 2009P. K. Sirmah Abstract The activity of marine borers was investigated at Mtongwe Jetty Pontoon, Mombasa, Kilindini harbour using untreated panels of Pinus patula (Schlecht) submerged to different depths. Twenty test panels replicated over 7 months were each strung in three ladder-like frames using nylon twine and suspended vertically, in such a way that the top most panels were 25 cm below the water surface at low and high tide. Monthly observations were made between January and July for the vertical incidence and extent of marine borer attack following the technique of Bobat (1995). Marine borers were collected from test panels, identified and counted. In addition, the percentage weight loss for panels at different depths was determined at the end of 7 months. Teredo fulleri (Clapp) was dominant on panels near water surface while Martesia striata (Linne) and Lyrodus pedicellatus (Quatrefages) were predominant at the bottom. The results showed that attack began within the first month of exposure and was severest by the seventh month. The vertical incidence and extent of attack decreased with increasing depth of panel exposure and was negatively correlated with depth. This is attributed to changes in hydrographic conditions. Résumé L'activité des foreurs marins a étéétudiée dans le Ponton de Mtongwe Jetty, Mombasa, dans le port de Kilindini, en utilisant des panneaux de Pinus patula (Schlecht) non traités, plongés à différentes profondeurs. Vingt panneaux tests identiques ont été attachés avec des cordes de nylon pour former trois cadres ressemblant à des échelles et suspendus pendant sept mois verticalement de façon à ce que les panneaux supérieurs se trouvent à 25 cm sous la surface à marée basse et haute. L'on a fait des observations mensuelles entre janvier et juillet de l'occurrence verticale et l'étendue de l'attaque des foreurs marins en utilisant la technique de Bobat (1995). Les foreurs marins ont été collectés sur les panneaux tests, identifiés et comptés. De plus, on a déterminé le pourcentage de la perte de poids des panneaux aux différentes profondeurs à la fin des sept mois. Teredo fulleri (Clapp) était dominant sur les panneaux situés près de la surface de l'eau alors que Martesia striata (Linné) et Lyrodus pedicellatus (Quatrefages) étaient prédominants en profondeur. Les résultats ont montré que l'attaque a commencé dès le premier mois et que c'est alors qu'elle fut la plus sévère. L'occurrence verticale et l'étendue de l'attaque diminuaient quand le panneau était plus profond et étaient négativement liées à la profondeur. Cela est attribué aux changements des conditions hydrographiques. [source] Contribution of dissolved organic nitrogen to N leaching from four German agricultural soilsJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 6 2002Jan Siemens Abstract Dissolved organic nitrogen (DON) substantially contributes to N leaching from forest ecosystems. However, little is known about the role of DON for N leaching from agricultural soils. Therefore, the aim of our study was to quantify the contribution of DON to total N leaching from four agricultural soils. Concentrations and fluxes of DON and mineral N were monitored at two cropped sites (Plaggic Anthrosols) and two fallow plots (Plaggic Anthrosol and Gleyic Podzol) from November 1999 till May 2001 by means of glass suction plates. The experimental sites were located near the city of Münster, NW Germany. Median DON concentrations in 90 cm depth were 2.3 mg l,1 and 2.0 mg l,1 at the cropped sites and 1.6 mg l,1 and 1.3 mg l,1 at the fallow sites. There was only a slight (Anthrosols) or no (Gleyic Podzol) decrease in median DON concentrations with increasing depth. Total N seepage was between 19 kg N ha,1 yr,1 and 46 kg N ha,1 yr,1 at the fallow sites and 16,159 kg N ha,1 yr,1 at the cropped sites. For the fallow plots, DON seepage contributed 10,21,% to the total N flux (4,5 kg DON ha,1 yr,1), at the cropped sites DON seepage was 6,21,% of the total N flux (6,10 kg DON ha,1 yr,1). Thus, even in highly fertilized agricultural soils, DON is a considerable N carrier in seepage that should be considered in detailed soil N budgets. Beitrag von gelöstem organisch gebundenen Stickstoff zur N-Auswaschung aus vier deutschen landwirtschaftlich genutzten Böden Während viele Studien die Bedeutung der Auswaschung von gelöstem organisch gebundenen Stickstoff (DON) für N-Verluste aus Waldökosystemem zeigen, existieren nur wenige Daten zur DON-Auswaschung aus landwirtschaftlich genutzten Böden. Das Ziel unserer Studie war es deshalb, den Beitrag von DON zur Auswaschung von N aus vier landwirtschaftlichen Böden zu quantifizieren. Von November 1999 bis Mai 2001 erfassten wir die Konzentrationen und Flüsse von DON und mineralischem Stickstoff auf zwei bewirtschafteten Flächen (Plaggenesche) und zwei Bracheflächen (Plaggenesch und Gley-Podsol) mit Hilfe von Glassaugplatten. Die Untersuchungsflächen befanden sich nahe Münster/Westfalen. Der Median der DON-Konzentrationen in 90 cm Bodentiefe betrug auf den bewirtschafteten Flächen 2.3 mg l,1 und 2.0 mg l,1, auf den Brachen 1.6 mg l,1 und 1.3 mg l,1. Wir stellten nur eine geringe Abnahme (Plaggenesche) oder keine Abnahme (Gley-Podsol) des Medians der DON-Konzentration mit der Tiefe fest. Die Gesamt-N-Auswaschung lag zwischen 19 kg N ha,1 a,1 und 46 kg N ha,1 a,1 für die Bracheflächen und zwischen 16 kg N ha,1 a,1 und 156 kg N ha,1 a,1 für die bewirtschafteten Flächen. Im Falle der Bracheflächen machte DON 10,21,% (4,5 kg DON ha,1 a,1) der Gesamt-N-Auswaschung aus. Dieser Anteil betrug 6,21,% (6,10 kg DON ha,1 a,1) für die bewirtschafteten Flächen. Auch in intensiv gedüngten landwirtschaftlichen Böden ist die Auswaschung von DON also ein wichtiger Austragspfad für N und sollte deshalb in detaillierten N-Bilanzen berücksichtigt werden. [source] Characterization of parylene-N and parylene-C photooxidationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2003K. G. Pruden Abstract Parylene-N and parylene-C are polymers of interest for microelectronic and medical coating applications. Modifications for improved surface properties could make them even more useful in such applications. Parylene-N and parylene-C films were exposed to ultraviolet light in the presence of oxygen and analyzed with Rutherford backscattering spectrometry, secondary-ion mass spectroscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy. This study shows that such exposure results in the formation of aldehyde and carboxylic acid groups near the surface of the films. At the maximum exposure dose, the concentration of oxygen in both parylene-N and parylene-C is about 13% at the film surface, and it decreases exponentially with increasing depth. Further modeling and optimization of this process would allow it to be used to tailor the surface concentration of oxygenated species in parylene for the optimization of adhesion and wettability or for the chemical binding of other moieties. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1486,1496, 2003 [source] Modeling the Effect of Oxygen on Photopolymerization KineticsMACROMOLECULAR THEORY AND SIMULATIONS, Issue 2 2006Allison K. O'Brien Abstract Summary: A comprehensive one-dimensional photopolymerization model was utilized to investigate the effect of oxygen on the free-radical photopolymerization kinetics. The spatial profiling aspect of the model provided insight into the heterogeneity of the cure kinetics due to oxygen inhibition, specifically the variance in the concentration profile of monomer and oxygen. Double bond conversion was negligible for the top ten microns of the film due to continuous oxygen diffusion, and increased with increasing depth. Similarly, the oxygen concentration decreased with increasing depth due to the competition between oxygen diffusion time and the polymerization rate. The effect of initiation rate on the extent of oxygen inhibition was investigated for various oxygen concentrations. As the initiation rate increased, the polymerization rate increased, and eventually approached that of a sample in an inert environment. Similarly, as the oxygen concentration was decreased, the polymerization rate increased. The effect of varying the initiation rate on the cure profile in the oxygen-exposed film was also studied. It was found that the unpolymerized tacky layer decreased from 50 µm to 5 µm with a 3 order of magnitude increase in initiation rate. Using the pseudo steady state approximation, the relationship between polymerization rate and initiation rate was derived for films in an oxygen environment. A direct relationship between the polymerization and initiation rate was found for films in air. The polymerization model supported this derivation and found that as the oxygen concentration was decreased, the dependence on initiation rate, or alpha, decreased, reaching the accepted value of 0.5 for alpha in inert environments. Double bond conversion versus film depth and cure time. [source] Experimental sponge fishery in Egypt during recovery from sponge diseaseAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2005J. Castritsi-Catharios Abstract 1.A survey was undertaken (1995) on the Mediterranean coast of Egypt that investigated four sponge fishing grounds. These fishing banks suffered from sponge disease between 1987 and 1990, causing a mass mortality of commercial sponges in the eastern and central Mediterranean. 2.Adult commercial sponges (length >10 cm) were harvested by divers in the infralittoral zone (depth range 17,36 m). The substratum at most of the sampling stations was hard, consisting mainly of plaques, rocks and heavy stones, sometimes covered by Posidonia oceanica. 3.Two commercial sponge species were detected, Hippospongia communis and Spongia cfr zimocca; the former was more prevalent and abundant. Light penetration in the area surveyed was high. The two commercial sponge species detected seemed to be well adapted to these conditions, as indicated by the colour of their external membranes, which were almost black due to enhanced pigment formation. The absence of Spongia officinalis, in the area surveyed may also be related to light penetration, since S. officinalis is a more sciaphilous species. 4.The shape of H. communis was almost spherical, and the average dimensions (length, width, height, circumference) increased with increasing depth of the fishing grounds. At shallower depths (<30 m), adult H. communis occurred in lower densities, whereas young commercial sponges were abundant. No signs of sponge disease were found. 5.It is concluded that the recovery of the four sponge fishing grounds was in progress, and that the repopulation of commercial sponges in the infralittoral zone showed a gradient from deeper to shallower waters. It is recommended to prohibit destructive fishing methods in the deeper waters in order to protect the population and its ability to regenerate. Copyright © 2005 John Wiley & Sons, Ltd. [source] In vivo pharmacokinetics of ketoprofen after patch application in the Mexican hairless pigBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 4 2009Masafumi Horie Abstract To evaluate the pharmacokinetics of topical drugs, in vitro permeation studies are performed using sacrificed pig skin or human tissues resected at surgery; however, these methods have their limitations in in vivo pharmacokinetics. This study examined the usefulness of Mexican hairless pigs for in vivo pharmacokinetic study, especially the drug concentration in the tissues. A ketoprofen patch was applied on the back of Mexican hairless pigs for 24,h, followed by sequential collection of blood specimens from 0 to 36,h (n=3). Also, the skin, subcutaneous fat, fascia and muscle from the center of the site of application were excised at 12,h after the application (n=4). Ketoprofen was first detected in the plasma at 8,h, the concentration increasing up to 24,h; the plasma concentration began to decrease after the removal of the ketoprofen patch. Ketoprofen concentrations in the tissues decreased with increasing depth of the tissues, but the values in the deep muscles, being the lowest among the tissues examined, were still higher than those in the plasma. While the data of drug concentration in human tissue are difficult to test, the Mexican hairless pig model appears to be attractive for in vivo pharmacokinetic studies of topically applied ketoprofen. Copyright © 2009 John Wiley & Sons, Ltd. [source] A Quantitative Study of Fault Zone SealingACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2010Yang LI Abstract: A fault is not simply a plane, but a zone consisting of a series of broken planes or lower faults. The greater the scale of faults, the wider and more complex the fault zone is. Fault-sealing properties are influenced by the fault zone itself, whose fault displacement, depth, net-to-gross-ratio of mudstone, fault plane angle, and fault mechanical properties play important controlling roles. The sealing of hydrocarbon by the fault zone depends on whether the fault zone can form a continuous sealing zone and if the pore throats connecting those fault zones are small enough. The concept of fault zone-sealing potential is proposed here, and a quantitative formula is established by using a great amount of practical statistical data as well as the fuzzy comprehensive evaluation method, which is a comprehensive characterization parameter to judge whether or not fault zones could seal oil hydrocarbon. The greater the value of the fault zone-sealing potential, the better sealed the fault is. For example, with increasing depth, the sealing degree of the Xin 68 Fault in the Dongxin 1 oilfield changes greatly, reflecting the complexity of fault-sealing properties. 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