Home About us Contact
|
Home About us Contact | ||
|
|
||
Water Movement (water + movement)
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] Sphagnum under pressure: towards an ecohydrological approach to examining Sphagnum productivityECOHYDROLOGY, Issue 4 2008D. K. Thompson Abstract The genus Sphagnum is the key peat-forming bryophyte in boreal ecosystems. Relying entirely on passive capillary action for water transport, soil moisture is often the limiting factor in Sphagnum production, and hence peat accumulation. While several hydrological models of peat physics and peatland water movement exist, these models do not readily interface with observations and models of peatland carbon accumulation. A conflict of approaches exists, where hydrological studies primarily utilize variables such as hydraulic head, while ecological models of Sphagnum growth adopt the coarse hydrological variables of water table (WT), volumetric water content (VWC) or gravimetric water content (WC). This review examines the potential of soil pressure head as a measurement to link the hydrological and ecological functioning of Sphagnum in peatlands. The non-vascular structure of Sphagnum mosses and the reliance on external capillary transport of water in the mosses make them an ideal candidate for this approach. The main advantage of pressure head is the ability to mechanistically link plot-scale hydrology to cellular-scale water requirements and carbon exchange. Measurement of pressure head may improve photosynthetic process representation in the next generation of peatland models. Copyright © 2008 John Wiley & Sons, Ltd. [source] AQP4 expression in striatal primary cultures is regulated by dopamine , implications for proliferation of astrocytesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2008Eva Küppers Abstract Proliferation of astrocytes plays an essential role during ontogeny and in the adult brain, where it occurs following trauma and in inflammation and neurodegenerative diseases as well as in normal, healthy mammals. The cellular mechanisms underlying glial proliferation remain poorly understood. As dopamine is known to modulate proliferation in different cell populations, we investigated the effects of dopamine on the proliferation of striatal astrocytes in vitro. We found that dopamine reduced proliferation. As proliferation involves, among other things, a change in cell volume, which normally comes with water movement across the membrane, water channels might represent a molecular target of the dopamine effect. Therefore we studied the effect of dopamine on aquaporin 4 (AQP4) expression, the main aquaporin subtype expressed in glial cells, and observed a down-regulation of the AQP4-M23 isoform. This down-regulation was the cause of the dopamine-induced decrease in proliferation as knockdown of AQP4 using siRNA techniques mimicked the effects of dopamine on proliferation. Furthermore, stimulation of glial proliferation by basic fibroblast growth factor was also abolished by knocking down AQP4. In addition, blocking of AQP4 with 10 ,m tetraethylammonium inhibited osmotically induced cell swelling and stimulation of glial cell proliferation by basic fibroblast growth factor. These results demonstrate a clear-cut involvement of AQP4 in the regulation of proliferation and implicate that modulation of AQP4 could be used therapeutically in the treatment of neurodegenerative diseases as well as in the regulation of reactive astrogliosis by preventing or reducing the glia scar formation, thus improving regeneration following ischemia or other trauma. [source] Aquaporin 4 changes in rat brain with severe hydrocephalusEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2006Xiaoyan Mao Abstract Hydrocephalus is characterized by impaired cerebrospinal fluid (CSF) flow with enlargement of the ventricular cavities of the brain and progressive damage to surrounding tissue. Bulk water movement is altered in these brains. We hypothesized that increased expression of aquaporins, which are water-permeable channel proteins, would occur in these brains to facilitate water shifts. We used quantitative (real-time) RT-PCR, Western blotting and immunohistochemistry to evaluate the brain expression of aquaporins (AQP) 1, 4, and 9 mRNA and protein in Sprague,Dawley rats rendered hydrocephalic by injection of kaolin into cistern magna. AQP4 mRNA was significantly up-regulated in parietal cerebrum and hippocampus 4 weeks and 9 months after induction of hydrocephalus (P < 0.05). Although Western blot analysis showed no significant change, there was more intense perivascular AQP4 immunoreactivity in cerebrum of hydrocephalic brains at 3,4 weeks after induction. We did not detect mRNA or protein changes in AQP1 (located in choroid plexus) or AQP9 (located in select neuron populations). Kir4.1, a potassium channel protein linked to water flux, exhibited enhanced immunoreactivity in the cerebral cortex of hydrocephalic rats; the perineuronal distribution was entirely different from that of AQP4. These results suggest that brain AQP4 up-regulation might be a compensatory response to maintain water homeostasis in hydrocephalus. [source] Impact of stone content on water movement in water-repellent sandEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2009E. Urbanek Summary Soils are commonly stony, especially in steep upland or heavily degraded sites. The hydrological effect of large stone contents has been previously investigated in wettable but not in water-repellent soils. For the latter, the focus has instead been on the impact of other soil characteristics (e.g. cracks and macropores) likely to promote water percolation. This paper investigates stone effects on water flow in water-repellent sand under laboratory conditions. Seventy-five experiments were performed on a water-repellent sand mixed with a range of quantities of different-sized wettable and water-repellent stones. The time taken for water to pass through each sand,stone mix, the percolated water volumes and numbers of dry and wet stones following each 60-minute experiment were recorded. At large stone contents (> 55% or > 65% by weight, depending on stone wettability), percolation occurred relatively quickly and in comparatively large quantities. At intermediate stone contents (45,65%) percolation response was variable and at stone contents < 45% for wettable and < 55% for water-repellent soils no water percolation occurred. We argue that with large stone contents flow pathways develop along sand,stone interfaces and a continuous preferential flow path can form provided there are sufficient stone-to-stone connections. The distribution and alignment of the stones, especially at intermediate stone contents, are important for promoting water movement. Water repellency determinations based only on the fine sediment component in stony soils could therefore be misleading as regards determining their hydrological response: the influence of the clastic component must also be considered. [source] Scaling of water flow through porous media and soilsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2008K. Roth Summary Scaling of fluid flow in general is outlined and contrasted to the scaling of water flow in porous media. It is then applied to deduce Darcy's law, thereby demonstrating that stationarity of the flow field at the scale of the representative elementary volume (REV) is a critical prerequisite. The focus is on the implications of the requirement of stationarity, or local equilibrium, in particular on the validity of the Richards equation for the description of water movement through soils. Failure to satisfy this essential requirement may occur at the scale of the REV or, particularly in numerical simulations, at the scale of the model discretization. The latter can be alleviated by allocation of more computational resources and by working on a finer-grained representation. In contrast, the former is fundamental and leads to an irrevocable failure of the Richards equation as is observed with infiltration instabilities that lead to fingered flow. [source] Mass fractal dimension of soil macropores using computed tomography: from the box-counting to the cube-counting algorithmEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2003J.S. Perret Summary Transport phenomena in porous media depend strongly on three-dimensional pore structures. Macropore networks enable water and solute to move preferentially through the vadose zone. A complete representation of their geometry is important for understanding soil behaviour such as preferential flow. Once we know the geometrical, topological and scaling attributes of preferential flow paths, we can begin computer simulations of water movement in the soil. The box-counting method is used in three dimensions (i.e. cube-counting algorithm) to characterize the mass fractal dimension of macropore networks using X-ray computed tomography (CT) matrices. We developed an algorithm to investigate the mass fractal dimension in three dimensions and to see how it compares with the co-dimensions obtained using the box-counting technique in two dimensions. For that purpose, macropore networks in four large undisturbed soil columns (850 mm × 77 mm diameter) were quantified and visualized, in both two and three dimensions, using X-ray CT. We observed an increasing trend between the fractal dimension and macroporosity for the four columns. Moreover, similar natural logarithm functions were obtained for the four cores by a least squares fit through plots of mass fractal dimension against macroporosity. [source] Simulating larval supply to estuarine nursery areas: how important are physical processes to the supply of larvae to the Aransas Pass Inlet?FISHERIES OCEANOGRAPHY, Issue 3 2004C. A. Brown Abstract Factors controlling the movement of fish larvae from coastal spawning environments to estuarine nursery areas are important to fish recruitment. In this paper, the role of physical processes in larval transport to estuarine nursery areas in the Aransas Pass region, Texas, is examined using a circulation model coupled with a fixed-depth particle transport model. Two phases of transport are examined: transport on the shelf to the tidal inlet and transport through the inlet to estuarine nursery areas. Observed pulsing in the supply of red drum (Sciaenops ocellatus) larvae to the tidal inlet is significantly correlated with modeled particle supply. This pulsing is not correlated with a specific physical process, but results from the interaction of several factors affecting water movement, including low-frequency variations in water level and wind forcing. Simulations suggest that the primary spawning region for red drum larvae that utilize nursery habitat in the Aransas Pass region is located north of the inlet. Patterns in the trajectories of particles that successfully enter the inlet reveal that they move alongshelf in the nearshore region and then move into the inlet, rather than moving directly across the shelf to the inlet. The approach path of particles outside the inlet determines the spatial transport patterns for inlets with branched channels and multiple bays. This study demonstrates that physical processes play an important role in determining larval supply to a tidal inlet. [source] Artificial Recharge Through a Thick, Heterogeneous Unsaturated ZoneGROUND WATER, Issue 3 2008John A. Izbicki Thick, heterogeneous unsaturated zones away from large streams in desert areas have not previously been considered suitable for artificial recharge from ponds. To test the potential for recharge in these settings, 1.3 × 106 m3 of water was infiltrated through a 0.36-ha pond along Oro Grande Wash near Victorville, California, between October 2002 and January 2006. The pond overlies a regional pumping depression 117 m below land surface and is located where thickness and permeability of unsaturated deposits allowed infiltration and saturated alluvial deposits were sufficiently permeable to allow recovery of water. Because large changes in water levels caused by nearby pumping would obscure arrival of water at the water table, downward movement of water was measured using sensors in the unsaturated zone. The downward rate of water movement was initially as high as 6 m/d and decreased with depth to 0.07 m/d; the initial time to reach the water table was 3 years. After the unsaturated zone was wetted, water reached the water table in 1 year. Soluble salts and nitrate moved readily with the infiltrated water, whereas arsenic and chromium were less mobile. Numerical simulations done using the computer program TOUGH2 duplicated the downward rate of water movement, accumulation of water on perched zones, and its arrival at the water table. Assuming 10 × 106 m3 of recharge annually for 20 years, a regional ground water flow model predicted water level rises of 30 m beneath the ponds, and rises exceeding 3 m in most wells serving the nearby urban area. [source] Revisiting a Classification Scheme for U.S.-Mexico Alluvial Basin-Fill AquifersGROUND WATER, Issue 5 2005Barry J. Hibbs Intermontane basins in the Trans-Pecos region of westernmost Texas and northern Chihuahua, Mexico, are target areas for disposal of interstate municipal sludge and have been identified as possible disposal sites for low-level radioactive waste. Understanding ground water movement within and between these basins is needed to assess potential contaminant fate and movement. Four associated basin aquifers are evaluated and classified; the Red Light Draw Aquifer, the Northwest Eagle Flat Aquifer, the Southeast Eagle Flat Aquifer, and the El Cuervo Aquifer. Encompassed on all but one side by mountains and local divides, the Red Light Draw Aquifer has the Rio Grande as an outlet for both surface drainage and ground water discharge. The river juxtaposed against its southern edge, the basin is classified as a topographically open, through-flowing basin. The Northwest Eagle Flat Aquifer is classified as a topographically closed and drained basin because surface drainage is to the interior of the basin and ground water discharge occurs by interbasin ground water flow. Mountains and ground water divides encompass this basin aquifer on all sides; yet, depth to ground water in the interior of the basin is commonly >500 feet. Negligible ground water discharge within the basin indicates that ground water discharges from the basin by vertical flow and underflow to a surrounding basin or basins. The most likely mode of discharge is by vertical, cross-formational flow to underlying Permian rocks that are more porous and permeable and subsequent flow along regional flowpaths beneath local ground water divides. The Southeast Eagle Flat Aquifer is classified as a topographically open and drained basin because surface drainage and ground water discharge are to the adjacent Wildhorse Flat area. Opposite the Eagle Flat and Red Light Draw aquifers is the El Cuervo Aquifer of northern Chihuahua, Mexico. The El Cuervo Aquifer has interior drainage to Laguna El Cuervo, which is a phreatic playa that also serves as a focal point of ground water discharge. Our evidence suggests that El Cuervo Aquifer may lose a smaller portion of its discharge by interbasin ground water flow to Indian Hot Springs, near the Rio Grande. Thus, El Cuervo Aquifer is a topographically closed basin that is either partially drained if a component of its ground water discharge reaches Indian Hot Springs or undrained if all its natural ground water discharge is to Laguna El Cuervo. [source] Using Temperature to Test Models of Flow Near Yucca Mountain, NevadaGROUND WATER, Issue 5 2003Scott Painter Ground water temperatures in the fractured volcanic aquifer near Yucca Mountain, Nevada, have previously been shown to have significant spatial variability with regions of elevated temperatures coinciding roughly with near-vertical north-south trending faults. Using insights gained from one-dimensional models, previous investigators have suggested upwelling along faults from an underlying aquifer as a likely explanation for this ground water temperature pattern. Using a three-dimensional coupled flow and heat-transport model, we show that the thermal high coinciding with the Paintbrush fault zone can be explained without significant upwelling from the underlying aquifer. Instead, the thermal anomaly is consistent with thermal conduction enhanced slightly by vertical ground water movement within the volcanic aquifer sequence. If more than -400 m3/day of water enters the volcanic aquifer from below along a 10 km fault zone, the calculated temperatures at the water table are significantly greater than the measured temperatures. These results illustrate the potential limitations in using one-dimensional models to interpret ground water temperature data, and underscore the value in combining temperature data with fully coupled three-dimensional simulations. [source] Altered aquaporin 9 expression and localization in human hepatocellular carcinomaHPB, Issue 1 2009Srikanth Padma Abstract Background:, In addition to the biochemical components secreted in bile, aquaporin (AQP) water channels exist in hepatocyte membranes to form conduits for water movement between the sinusoid and the bile canaliculus. The aim of the current study was to analyse AQP 9 expression and localization in human hepatocellular carcinoma (HCC) and non-tumourigenic liver (NTL) tissue from patients undergoing hepatic resection. Methods:, Archived tissue from 17 patients was sectioned and analysis performed using an antibody raised against AQP 9. Slides were blind-scored to determine AQP 9 distribution within HCC and NTL tissue. Results:, Aquaporin 9 was predominantly expressed in the membranes of hepatocytes and demonstrated zonal distribution relative to hepatic sinusoid structure in normal liver. In HCC arising in the absence of cirrhosis AQP 9 remained membrane-localized with zonal distribution in the majority of NTL. By contrast, AQP 9 expression was significantly decreased in the HCC mass vs. pair-matched NTL. In HCC in the presence of cirrhosis, NTL was characterized by extensive AQP 9 staining in the membrane in the absence of zonal distribution and AQP 9 staining in NTL was significantly greater than that observed in the tumour mass. Conclusions:, These data demonstrate that human HCC is characterized by altered AQP 9 expression and AQP 9 localization in the NTL mass is dependent on underlying liver pathology. Given the central role of AQPs in normal liver function and the potential role of AQPs during transformation and progression, these data may prove valuable in future diagnostic and/or therapeutic strategies. [source] Factors governing the formation and persistence of layers in a subalpine snowpackHYDROLOGICAL PROCESSES, Issue 7 2004David Gustafsson Abstract The layered structure of a snowpack has a great effect on several important physical processes, such as water movement, reflection of solar radiation or avalanche release. Our aim was to investigate what factors are most important with respect to the formation and persistence of distinct layers in a subalpine environment. We used a physically based numerical one-dimensional model to simulate the development of a snowpack on a subalpine meadow in central Switzerland during one winter season (1998,99). A thorough model validation was based on extensive measurement data including meteorological and snow physical parameters. The model simulated the snow water equivalent and the depth of the snowpack as well as the energy balance accurately. The observed strong layering of the snowpack, however, was not reproduced satisfactorily. In a sensitivity analysis, we tested different model options and parameter settings significant for the formation of snow layers. The neglection of effects of snow microstructure on the compaction rate, and the current description of the water redistribution inside the snowpack, which disregard capillary barrier effects, preferential flow and lateral water flow, were the major limitations for a more realistic simulation of the snowpack layering. Copyright © 2004 John Wiley & Sons, Ltd. [source] Behavior and physiology of mechanoreception: separating signal and noiseINTEGRATIVE ZOOLOGY (ELECTRONIC), Issue 1 2009John C. MONTGOMERY Abstract The mechanosensory lateral line is found in all aquatic fish and amphibians. It provides a highly sensitive and versatile hydrodynamic sense that is used in a wide range of behavior. Hydrodynamic stimuli of biological interest originate from both abiotic and biotic sources, and include water currents, turbulence and the water disturbances caused by other animals, such as prey, predators and conspecifics. However, the detection of biologically important stimuli often has to occur against a background of noise generated by water movement, or movement of the fish itself. As such, separating signal and noise is "of the essence" in understanding the behavior and physiology of mechanoreception. Here we discuss general issues of signal and noise in the lateral-line system and the behavioral and physiological strategies that are used by fish to enhance signal detection in a noisy environment. In order for signal and noise to be separated, they need to differ, and we will consider those differences under the headings of: frequency and temporal pattern; intensity discrimination; spatial separation; and mechanisms for the reduction of self-generated noise. We systematically cover the issues of signal and noise in lateral-line systems, but emphasize recent work on self-generated noise, and signal and noise issues related to prey search strategies and collision avoidance. [source] Simulation of the soil wetting shape under porous pipe sub-irrigation using dimensional analysis,IRRIGATION AND DRAINAGE, Issue 4 2007Shu Qiaosheng analyse dimensionnelle; tuyau poreux; forme de mouillage du sol; irrigation soutterraine Abstract Based on the discharge characteristics test for a porous pipe used widely in greenhouse sub-irrigation in west Liaoning Province, China, Time Domain Reflectometry (TDR) was applied to monitor the process of soil water movement during sub-irrigation. A model to determine the soil wetting shape was developed using a dimensional analysis method. Statistical analysis revealed that this model has a high accuracy in simulating the wetted soil shape, demonstrating that there was no significant difference between predicted and observed soil wetted width under different depths. It showed that one simple model could also be used to simulate the shape of the wetting area under a porous pipe sub-irrigation system, which was expected to provide aids for deciding depth and intervals of pipes and designing a sub-irrigation scheme. Copyright © 2007 John Wiley & Sons, Ltd. A partir des tests de débit caractéristique d'un tuyau poreux largement utilisé en irrigation souterraine sous serre dans l'ouest de la Province de Liaoning, une Réflectométrie dans le Domaine Temporel (TDR) a été utilisée pour surveiller le processus du mouvement de l'eau dans le sol pendant l'irrigation. Un modèle pour déterminer la forme de mouillage du sol a été développé en utilisant une méthode d'analyse dimensionnelle. L'analyse statistique a révélé que ce modèle est d'une très grande précision dans la simulation de la forme mouillée du sol, car il n'y avait aucune différence significative entre la prévision et l'observation de largeur de sol mouillé à différentes profondeurs. Elle a montré qu'un modèle simple pouvait aussi être utilisé pour simuler la forme de la zone humide en irrigation souterraine à canalisations poreuses, ce qui permet une aide à la décision concernant la profondeur et les intervalles entre tuyaux lors de la conception d'un système d'irrigation souterraine. Copyright © 2007 John Wiley & Sons, Ltd. [source] Drainage and salinity assessment in the Huinong Canal Irrigation District, Ningxia, China,IRRIGATION AND DRAINAGE, Issue 2 2005Peter Hollanders irrigation; drainage; salinisation; développement durable Abstract In the Huinong Canal Irrigation District, Ningxia, China, annually almost half of the amount of irrigation water, which is supplied from the Yellow River, is drained back to the river through an open drainage system. Waterlogging and salinization occur in parts of the irrigated area and part of the water drains to the surrounding desert. While 85,90% of inflow to the area is irrigation water there are good possibilities for water saving. To analyse water movement at field level and resulting drainage needs, from autumn 1998 until spring 2001 observations were made in two experimental areas: Pingluo and Huinong. The data were used for the calibration and validation of three computer models: SWAP, MODFLOW and DUFLOW. Different scenarios of water and salt behaviour in the unsaturated and saturated zone were simulated, as well as the flow through one of the main drains. The effects of various irrigation amounts and groundwater tables on crop growth, percolation and drainage needs were analysed. The present average irrigation water application during the growing season is 630,mm. On average 15% of the supplied water (665 million m3,yr,1) remains in the area. This is mainly irrigation water that was not used by the crops and did not reach the drainage system. It was found that an irrigation level of 75% of the present practice with a groundwater table of 1.0,m below the surface during the growing season gave the best results. Under such a practice the soil salinity will fluctuate around 3,3.5,dS,m,1, resulting in a good growth of wheat and a yield reduction for maize of about 20%. When adequate amounts of irrigation water are supplied in combination with local drainage improvements, the areas with middle and low-yielding crops can be reduced, as well as the area of wasteland. Copyright © 2005 John Wiley & Sons, Ltd. Annuellement presque la moitié de la quantité d'eau d'irrigation dans le district d'irrigation du canal Huinong, Ningxia, Chine, alimenté par la Rivière Jaune, est retournée à la rivière par un système de drainage à ciel ouvert. Des cas de saturation d'eau et de salinisation surgissent dans certaines parties de la zone irriguée et une partie de l'eau suinte vers le désert environnant. Comme 85,90% de l'entrée de l'eau dans la zone est de l'eau d'irrigation il y a de bonnes possibilités pour économiser de l'eau. Pour analyser la circulation de l'eau au niveau du champ et la nécessité de drainage des observations ont été effectuées pendant la période d'automne 1998 jusqu'au printemps 2001 dans deux zones expérimentales, Pingluo et Huinong. Les données rassemblées ont servi pour le calibrage et la validation de trois modèles informatiques: SWAP, MODFLOW et DUFLOW. Ces modèles ont été employés pour simuler plusieurs scénarios de comportement de l'eau et du sel dans la zone non saturée et dans la zone saturée tout comme l'écoulement par un des tuyaux d'écoulement principaux: le cinquième tuyau d'écoulement. L'effet de l'apport de différentes quantités d'eau d'irrigation, de différents niveaux de la nappe phréatique sur la croissance des cultures, la percolation et la nécessité de drainage a été analysé. L'actuel apport d'eau d'irrigation est de 630,mm en moyenne pendant la saison de croissance. Quinze pour cent en moyenne de l'eau fournie (665 millions m3/année) reste dans la zone, principalement de l'eau d'irrigation qui n'a pas servi aux cultures et qui n'a pas atteint le système de drainage. Un niveau d'irrigation représentant 75% des valeurs actuelles et une surface de la nappe phréatique de 1.0,m sous la surface donnent les meilleurs résultats pendant la saison de croissance. De tels apports entretiennent une salinisation du sol qui fluctuera entre environ 3 et 3.5,dS,m,1, donnant un bon résultat de la croissance du blé et une diminution du rendement pour le maïs d'environ 20%. Lorsque l'alimentation par des quantités adéquates d'eau d'irrigation sera assurée en combinaison avec des améliorations du drainage local, la zone donnant des récoltes moyennes et basses peut être réduite ainsi que les zones incultes. Copyright © 2005 John Wiley & Sons, Ltd. [source] The reproductive biology and ecology of the Port Jackson shark Heterodontus portusjacksoni in the coastal waters of eastern AustraliaJOURNAL OF FISH BIOLOGY, Issue 10 2008D. M. Powter The reproductive biology and ecology of the Port Jackson shark Heterodontus portusjacksoni was investigated at three locations on the central and southern coast of New South Wales (NSW), Australia from January 2002 to December 2005 using underwater visual census surveys and samples obtained from a commercial fishery. Adults displayed sexual dimorphism in total length (LT) at sexual maturity, with males maturing between 762 and 772 mm LT and females between 902 and 905 mm LT. The mean ovarian fecundity was estimated at 16 offspring per female but was unrelated to female LT. Male gonado-somatic (IG) and hepato-somatic (IH) indices and female IG declined from July to November as did maximum ovarian follicle diameter and the diameter of the three largest follicles. Adults were absent from inshore reefs between December and July. Hence, H. portusjacksoni has a synchronous annual breeding season in NSW, which occurs between July and November (the austral winter to spring), with a peak in oviposition from August to October. Heterodontus portusjacksoni copulatory and ovipository behaviour are reported for the first time. Copulation was observed and involved oral grasping of the female's pectoral fin by a single male, which wrapped his body around hers to insert one clasper. Ovipositing females appeared to search crevices in the reef prior to delivering a single capsule, which was washed into the crevice by water movement, with the female departing very soon after oviposition. This study represents the first rigorously quantitative analysis of H. portusjacksoni reproductive biology and ecology in NSW waters. [source] Sex- and region-specific alterations of basal amino acid and monoamine metabolism in the brain of aquaporin-4 knockout miceJOURNAL OF NEUROSCIENCE RESEARCH, Issue 4 2005Yi Fan Abstract Aquaporin-4 (AQP4), a predominant water channel of the brain, mediates transmembrane water movement at the blood,brain barrier and brain,cerebrospinal fluid interface. A broad pattern of evidence indicates that AQP4 and regulators of its expression are potential targets for treatment of brain swelling, but whether it participates in the regulation of neurotransmission has not been reported. We examined neurochemical differences between AQP4-knockout and wild-type mice with particular focus on neurotransmission. Basal tissue neurotransmitter and metabolite levels were measured by high-performance liquid chromatography. Significant sex- and region-specific differences of amino acids and monoamines were found in the brain of wild-type and AQP4-knockout mice. In cortex, striatum, and hippocampus of male AQP4-knockout mice, an increase of glutamine and decrease of aspartate were observed. Glutamate was increased only in female AQP4-knockout mice. The lack of AQP4 failed to affect the levels of ,-aminobutyric acid and taurine. In the medial prefrontal cortex of AQP4-knockout mice, the levels of serotonin and norepinephrine were increased, but no significant change in dopamine level was found. In the striatum of male AQP4-knockout mice, the levels of dopamine and serotonin were remarkably increased, which was not found in female mice. In the hypothalamus of AQP4-knockout mice, only the serotonin level was altered. These results provide the first evidence that the lack of AQP4 expression is accompanied by sex- and region-specific alterations in brain amino acid and monoamine metabolism. © 2005 Wiley-Liss, Inc. [source] RECENT ADVANCES IN FERTILIZATION ECOLOGY OF MACROALGAE,JOURNAL OF PHYCOLOGY, Issue 1 2002Bernabé SantelicesArticle first published online: 19 FEB 200 Our understanding of natural patterns of fertilization in seaweeds has increased substantially over the last 10 years due to new approaches and methods to characterize the nature and frequency of fertilization processes in situ, to recognize the conditions and mechanisms enhancing fertilization success, and to anticipate population and community consequences of the patterns of natural fertilization. Successful reproduction in many species depends on a delicate juxtaposition of abiotic and biotic conditions. Important abiotic factors are those triggering gamete release (e.g. single or interacting effects of light quality and water movement) and those affecting gamete viability or concentrations (e.g. salinity effects on polyspermy blocks; gamete dilution due to water movement). Examples of important biotic components are synchronous gamete release, efficiency of polyspermy-blocking mechanisms, population density of sexually fertile thalli, interparent distances, and male-to-female ratios. Field data indicate fertilization frequencies of 70%,100% in broadcasting-type seaweeds (e.g. fucoids) and 30%,80% in brooding-type (red) algae. Red algal values are higher than previously thought and challenge presently accepted explanations for their complex life histories. Important population and community questions raised by the recent findings relate to the magnitude of gene flow and exchange occurring in many micropopulations that seemingly breed during periods of isolation, the physiological basis and population effects of male-to-male competition and sexual selection during fertilization of brooding seaweeds, and the effects of massive gamete release, especially in holocarpic seaweeds, on benthic and planktonic communities. Comparative studies in other algal groups are now needed to test the generality of the above patterns, to provide critical pieces of information still missing in our understanding of natural fertilization processes, and to elucidate the evolutionary consequences of the different modes of reproduction (e.g. brooders vs. broadcasters). [source] CONTRIBUTIONS TO UNDERSTANDING SEAWEEDS IN COASTAL COMMUNITIESJOURNAL OF PHYCOLOGY, Issue 2001Article first published online: 24 SEP 200 Dawes, C. J. Department of Biology, University of South Florida, Tampa, Florida 33620 The goal of my presentation is to review several studies that have enhanced our understanding of the effects of abiotic factors on coastal and estuarine seaweed populations. Accordingly, I will introduce a few key papers dealing with five major abiotic factors-i.e. salinity, temperature, desiccation, water motion, and illumination. Foremost, the salinity tolerance studies of Russell and Bolton (1975) have broad applicability to estuarine seaweeds, while the osmoregulatory studies of Bisson and Kirst (1979) are also significant. Biebl's (1972) review of his earlier studies on temperature tolerances in diverse seaweeds were pivotal. Johnston and Raven's (1986) studied the effects of desiccation on the fucoid brown alga Ascophyllum nodosum, while similar studies on the saccate brown seaweed Colpomenia peregrina were conducted by Oates (1985). Lewis (1968) conducted early synoptic evaluations of the effects of water movement on rocky shore communities, while Kitching and Ebling (1967) gave detailed assessments of seaweed populations within estuarine tidal rapids in Ireland. Basically estuarine tidal rapids represent areas of enhanced nutrients, oxygen and light availability, plus reduced sedimentation (Mathieson et al. (1983). The physiological effects of light have probably been evaluated more than any single abiotic factor and two areas of importance are cited here. The critical papers by Levring (1947) on submarine illumination and those of Ramus (1978) and Littler and Littler (1980) on algal form and light response. Several areas of future studies are also suggested, which may further enhance our understanding of seaweed adaptations. In summary, five major abiotic factors affecting coastal and estuarine seaweed populations will be discussed, their importance to seaweeds noted, and "key" findings for several significant papers summarized. [source] Nutrient losses from rain-fed bench terraced cultivation systems in high rainfall areas of the mid-hills of NepalLAND DEGRADATION AND DEVELOPMENT, Issue 5 2007G. P. Acharya Abstract Between the elevations of 1000 and 2000,m in the mid-hills of Nepal, over 12 million people subsist on land-holdings of less than 0·5,ha. These farmers have limited access to commercial inputs such as fertilisers and are reliant on organic manures for soil fertility maintenance. Participatory research was conducted with farmers on bari land (upper slope rain-fed crop terraces) in the hill community of Landruk (bench terraces 0,5° slope, 3000,3500,mm annual rainfall, which aimed to develop soil and water management interventions that controlled erosion without resulting in high leaching, and so were effective in minimising total nutrient losses. Interventions tested were the control of water movement through diversion of run-on and planting fodder grasses on terrace risers on bench terraces. The interventions were effective in reducing soil loss from the bari land in comparison with existing farmer practices, but no effect was observed on nutrient losses in solution form through runoff and leaching. Losses of NO3 -N in leachate ranged from 17·3 to 99·7,kg,ha,1,yr,1, but only 0·7 to 5·6,kg,ha,1,yr,1 in runoff. The overall nutrient balance suggests that the system is not sustainable. Fertility is heavily dependent on livestock inputs and if the current trends of declining livestock numbers due to labour constraints continue, further losses in productivity can be expected. However, farmers are interested in interventions that tie ecosystem services with productivity enhancement and farmers' priorities should be used as entry points for promoting interventions that are system compatible and harness niche opportunities. Copyright © 2007 John Wiley & Sons, Ltd. [source] Changes in Diapered and Nondiapered Infant Skin Over the First Month of LifePEDIATRIC DERMATOLOGY, Issue 1 2000Marty O. Visscher Ph.D. Diapered and nondiapered skin sites were contrasted to the volar forearm of adults (mothers). Thirty-one term infants were evaluated in the hospital on postnatal day 1 and at home on days 4, 7, 14, 21, and 28 for a total of six visits. Measurements included baseline skin hydration, continuous capacitive reactance, peak water sorption, rate of water desorption, skin pH, skin temperature, and environmental conditions. Changes in epidermal barrier properties over the first 4 weeks of life included an increase in surface hydration, a decrease in transepidermal water movement under occlusion, a decrease in surface water desorption rate, and a decrease in surface pH. Diapered and nondiapered regions were indistinguishable at birth but exhibited differential behavior over the first 14 days, with the diapered region showing a higher pH and increased hydration. Maternal measurements remained constant throughout the period. We conclude that healthy newborn skin undergoes progressive changes in epidermal barrier properties over the first 28 days. Adult skin testing does not replicate newborn skin during the first month of life. [source] Rapid Holocene chemical weathering on a calcitic lake shoreline in an alpine periglacial environment: Attgløyma, Sognefjell, southern NorwayPERMAFROST AND PERIGLACIAL PROCESSES, Issue 1 2006Geraint Owen Abstract A small lake (Attgløyma) at an altitude of about 1220,m in the low-alpine zone, southern Norway, has a shore platform in calcitic and quartzitic muscovite-chlorite schists. The platform has recently been exposed by a fall in lake level due to upstream dam construction and exhibits micro-landforms ranging from pits and grooves to upstanding crenulate ridges produced by differential chemical weathering under relatively constant conditions over the last ca. 10,000 years. The maximum surface lowering rate of the calcitic layers estimated from differential weathering is 35,mm,ka,1, which is about an order of magnitude greater than most previous estimates from alpine and polar periglacial environments. Average bedrock surface lowering across the whole platform reached a maximum of 15.5,±,2.2,mm,ka,1 in a vertical zone corresponding with the former lake level, declining to negligible values around 0.7,m below lake level. Differential weathering and bedrock surface lowering were also negligible immediately above lake level. Correspondence of maximum surface lowering rates with the former lake level and a shoreline notch at the back of a platform suggest that the effects of solutional weathering of the calcite have been enhanced by water movement generated by small lake-surface waves. Copyright © 2006 John Wiley & Sons, Ltd. [source] Xylem Flow and its Driving Forces in a Tropical Liana: Concomitant Flow-Sensitive NMR Imaging and Pressure Probe MeasurementsPLANT BIOLOGY, Issue 6 2000N. Wistuba Abstract: Flow-sensitive NMR imaging and pressure probe techniques were used for measuring xylem water flow and its driving forces (i.e., xylem pressure as well as cell turgor and osmotic pressure gradients) in a tropical liana, Epipremnum aureum. Selection of tall specimens allowed continuous and simultaneous measurements of all parameters at various distances from the root under diurnally changing environmental conditions. Well hydrated plants exhibited exactly linearly correlated dynamic changes in xylem tension and flow velocity. Concomitant multiple-probe insertions along the plant shoot revealed xylem and turgor pressure gradients with changing magnitudes due to environmental changes and plant orientation (upright, apex-down, or horizontal). The data suggest that in upright and - to a lesser extent - in horizontal plants the transpirational water loss by the cells towards the apex during the day is not fully compensated by water uptake through the night. Thus, longitudinal cellular osmotic pressure gradients exist. Due to the tight hydraulic coupling of the xylem and the tissue cells these gradients represent (besides the transpiration-induced tension in the xylem) an additional tension component for anti-gravitational water movement from the roots through the vessels to the apex. [source] Water relations of baobab trees (Adansonia spp.PLANT CELL & ENVIRONMENT, Issue 6 2006L.) during the rainy season: does stem water buffer daily water deficits? ABSTRACT Baobab trees are often cited in the literature as water-storing trees, yet few studies have examined this assumption. We assessed the role of stored water in buffering daily water deficits in two species of baobabs (Adansonia rubrostipa Jum. and H. Perrier and Adansonia za Baill.) in a tropical dry forest in Madagascar. We found no lag in the daily onset of sap flow between the base and the crown of the tree. Some night-time sap flow occurred, but this was more consistent with a pattern of seasonal stem water replenishment than with diurnal usage. Intrinsic capacitance of both leaf and stem tissue (0.07,0.08 and 1.1,1.43 MPa,1, respectively) was high, yet the amount of water that could be withdrawn before turgor loss was small because midday leaf and stem water potentials (WPs) were near the turgor-loss points. Stomatal conductance was high in the daytime but then declined rapidly, suggesting an embolism-avoidance strategy. Although the xylem of distal branches was relatively vulnerable to cavitation (P50: 1.1,1.7 MPa), tight stomatal control and minimum WPs near ,1.0 MPa maintained native embolism levels at 30,65%. Stem morphology and anatomy restrict water movement between storage tissues and the conductive pathway, making stored-water usage more appropriate to longer-term water deficits than as a buffer against daily water deficits. [source] Do pathways of water movement and leaf anatomical dimensions allow development of gradients in H218O between veins and the sites of evaporation within leaves?PLANT CELL & ENVIRONMENT, Issue 1 2004M. M. BARBOUR ABSTRACT The oxygen isotope enrichment of bulk leaf water (,L), is often observed to be poorly predicted by the Craig,Gordon-type models developed for evaporative enrichment from a body of water (,e). The discrepancy between ,L and ,e may be explained by gradients in enrichment within the leaf as a result of convection of unenriched water to the sites of evaporation opposing the diffusion of enrichment away from the sites; a Péclet effect. However, this effect is difficult to quantify because the velocities of water movement within the leaf are unknown. This paper attempts to model the complex anatomy of a leaf, and hence such velocities, to assess if the gradients in H218O required for a significant Péclet effect between the vein and the evaporation sites are possible within a leaf. Published dimensions of cells in wheat leaves are used to calculate the cross-sectional areas perpendicular to the flow velocities of water through assumed pathways. By combining the ratio of actual to ,slab' velocities with anatomical lengths, equivalent lengths (L) emerge. In this way, it is concluded that if water moves only through the cell walls, or from cell to cell via either aquaporins or plasmodesmata, and evaporates from mesophyll cells, or the substomatal cells, or from the peristomatal region (a total of 15 combinations of assumptions), then the 15 central estimates of the values of L are between 9 and 200 mm. Each of these central estimates is subject to uncertainty, but overall their magnitude is important and estimates of L are comparable with those made from fitting to isotopic data (8 mm for wheat). It is concluded that significant gradients in enrichment between the vein and the evaporation sites are likely. [source] The hydrological response of heavy clay grassland soils to rainfall in south-west England using ,2H,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 5 2010Steven J. Granger Stable isotopes of water have been previously used in catchment studies to separate rain-event water from pre-event groundwater. However, there are a lack of studies at the smaller scale looking at the separation of event water from pre-event water. This is particularly relevant for heavy clay soil systems through which the movement of water is uncertain but is thought to be rainwater-dominated. The data presented here were collected at a rural site in the south-west of England. The historic rainfall at the site was isotopically varied but similar to the global meteoric water line, with annual weighted means of ,37, for ,2H and ,5.7, for ,18O and with no seasonal variation. Drainage was sampled from the inter-flow (surface runoff,+,lateral through-flow) and drain-flow (55,cm deep mole drains) pathways of two 1,ha lysimeters during two rainfall events, which had ,2H values of ,68, and ,92,, respectively. The ,2H values of the lysimeter drainage water suggest that there was no contribution of event water during the first, small discharge (Q) event; however, the second larger event did show isotopic variation in ,2H values negatively related to Q indicating that rainwater was contributing to Q. A hydrograph separation indicated that only 49,58% of the inter-flow and 18,25% of the drain-flow consisted of event water. This was surprising given that these soil types are considered retentive of soil water. More work is needed on heavy clay soils to understand better the nature of water movement from these systems. Copyright © 2010 John Wiley & Sons, Ltd. [source] Alteration of articular cartilage frictional properties by transforming growth factor ,, interleukin-1,, and oncostatin MARTHRITIS & RHEUMATISM, Issue 2 2009Jason P. Gleghorn Objective To evaluate the functional effects of transforming growth factor ,1 (TGF,1), interleukin-1, (IL-1,), and oncostatin M (OSM) on the frictional properties of articular cartilage and to determine the role of cytokine-mediated changes in cartilage frictional properties by extracting and redepositing lubricin on the surface of cartilage explants. Methods Neonatal bovine cartilage explants were cultured in the presence or absence of 10 ng/ml of TGF,1, IL-1,, or OSM over 48 hours. Boundary lubrication tests were conducted to determine the effects of endogenously produced surface localized lubricin and of exogenous lubricin at the tissue surface and in the lubricant solution. The initial friction coefficient (,0), equilibrium friction coefficient (,eq), and Young's modulus (EY) were determined from the temporal load data. Results IL-1, and OSM decreased tissue glycosaminoglycan (GAG) content by ,20% over 48 hours and decreased EY to a similar extent (11,17%), but TGF, did not alter GAG content or EY. Alterations in proteoglycan content corresponded to changes in ,0, but endogenous lubricin decreased boundary mode ,eq. The addition of exogenous lubricin, either localized at the tissue surface or in the lubricating solution, did not modulate ,0, but it did lower ,eq in cytokine-treated cartilage. Conclusion This study provides new insight into the functional consequences of cytokine-mediated changes in friction coefficient. In combination with established pathways of cytokine-mediated lubricin metabolism, these data provide evidence of distinct biochemical origins of boundary and biphasic pressure-mediated lubrication mechanisms in cartilage, with boundary lubrication regulated by surface accumulation of lubricants and biphasic lubrication controlled by factors such as GAG content that affect water movement through the tissue. [source] Interaction between wind-induced seiches and convective cooling governs algal distribution in a canyon-shaped reservoirFRESHWATER BIOLOGY, Issue 7 2007RAFAEL MARCÉ Summary 1. Wind is considered the dominant factor controlling phytoplankton distribution in lentic environments. In canyon-shaped reservoirs, wind tends to blow along the main axis generating internal seiches and advective water movements that jointly with biological features of algae can produce a heterogeneous phytoplankton distribution. Turbulence generated by wind stress and convection will also affect the vertical distribution of algae, depending on their sinking properties. 2. We investigated the vertical and horizontal distribution of phytoplankton during the stratification period in Sau Reservoir (NE Spain). Sites along the main reservoir axis were sampled every 4 h for 3 days, and profiles of chlorophyll- a and temperature were made using a fluorescent FluoroProbe, which can discriminate among the main algal groups. Convective and wind shear velocity scales, and energy dissipation were calculated from meteorological data, and simulation experiments were performed to describe non-measured processes, like vertical advection and sinking velocity of phytoplankton. 3. Wind direction changed from day to night, producing a diel thermocline oscillation and an internal seiche. Energy dissipation was moderate during the night, and mainly attributed to convective cooling. During the day the energy dissipation was entirely attributed to wind shear, but values indicated low turbulence intensity. 4. The epilimnetic algal community was mainly composed of diatoms and chlorophytes. Chlorophytes showed a homogeneous distribution on the horizontal and vertical planes. Diatom horizontal pattern was also homogeneous, because the horizontal advective velocities generated by wind forcing were not high enough to develop phytoplankton gradients along the reservoir. 5. Diatom vertical distribution was heterogeneous in space and time. Different processes dominated in different regions of the reservoir, due to the interaction between seiching and the daily cycle of convective-mediated turbulence. As the meteorological forcing followed a clear daily pattern, we found very different diatom sedimentation dynamics between day and night. Remarkably, these dynamics were asynchronous in the extremes of the seiche, implying that under the same meteorological forcing a diatom population can show contrasting sedimentation dynamics at small spatial scales (approximately 103 m). This finding should be taken into account when interpreting paleolimnological records from different locations in a lake. 6. Vertical distribution of non-motile algae is a complex process including turbulence, vertical and horizontal advection, variations in the depth of the mixing layer and the intrinsic sinking properties of the organisms. Thus, simplistic interpretations considering only one of these factors should be regarded with caution. The results of this work also suggest that diatoms can persist in stratified water because of a synergistic effect between seiching and convective turbulence. [source] Factors influencing the spatial distribution of zooplankton and fish in Loch Ness, UKFRESHWATER BIOLOGY, Issue 4 2000D. G. George Summary 1The vertical and horizontal distribution of phytoplankton, zooplankton and fish in Loch Ness, Scotland, were monitored during one day-time and one night-time survey in July 1992. The vertical samples were collected at a site located at the northern end of the loch and the horizontal samples along a longitudinal transect. 2The vertical distribution surveys demonstrated that the phytoplankton, the zooplankton and the fish were concentrated in the top 30 m of water above the seasonal thermocline. Within this layer, Cyclops stayed much closer to the surface than Eudiaptomus but both species moved towards the surface at night. 3The most important factor influencing the horizontal distribution of the phytoplankton was the north- south gradient in productivity. The sub-catchments surrounding the north basin contain a greater proportion of arable land than those to the south and the concentrations of nitrate-nitrogen and phytoplankton chlorophyll increased systematically from south to north. 4Zooplankton distribution patterns were influenced by wind-induced water movements and the dispersion of allochthonous material from the main inflows. The highest concentrations of Cyclops were recorded in the north, where there was more phytoplankton, and the highest concentrations of Eudiaptomus in the south, where there were higher concentrations of non-algal particulates. 5There was no spatial correlation between total zooplankton and total fish abundance but the highest concentrations of small (1,5 cm) fish were recorded in the south where there was a large patch of Eudiaptomus. The number of Eudiaptomus at specific locations within this patch were, however, negatively correlated with the numbers of small fish. These results suggest that the fish were actively foraging within the patch and were depleting their zooplankton prey in the areas where they were most abundant. [source] | ||||||||||||||||||||||||||||||||||