Storage Capacity (storage + capacity)

Distribution by Scientific Domains

Kinds of Storage Capacity

  • water storage capacity


  • Selected Abstracts


    Mesoporous Hydrous Manganese Dioxide Nanowall Arrays with Large Lithium Ion Energy Storage Capacities

    ADVANCED FUNCTIONAL MATERIALS, Issue 7 2009
    Dawei Liu
    Abstract Novel nanowall arrays of hydrous manganese dioxide MnO2,·,0.5H2O are deposited onto cathodic substrates by the potentiostatic method from a mixed aqueous solution of manganese acetate and sodium sulfate. The deposition is induced by a change of local pH resulting from electrolysis of H2O, and hierarchical mesoporous nanowall arrays are formed as a result of simultaneous precipitation of manganese hydroxide and release of hydrogen gas bubbles from the cathode. The morphology and lithium ion intercalation properties are found to change appreciably with the concentration of the precursor electrolyte, with a significant reduction in specific surface area with an increased precursor concentration. For example, mesoporous nanowall arrays deposited from 0.1,M solution possess a surface area of ,96,m2 g,1 and exhibit a stable high intercalation capacity of 256,mA hg,1 with a film of 0.5,µm in thickness, far exceeding the theoretical limit of 150,mA hg,1 for manganese dioxide bulk film. Such mesoporous nanowall arrays offer much greater energy storage capacity (e.g., ,230,mA hg,1 for films of ,2.5,µm) than that of anodic deposited films of the same thickness (,80,mA hg,1). Such high lithium ion intercalation capacity and excellent cyclic stability of the mesoporous nanowall arrays, especially for thicker films, are ascribed to the hierarchically structured macro- and mesoporosity of the MnO2,·,0.5H2O nanowall arrays, which offer large surface to volume ratio favoring interface Faradaic reactions, short solid-state diffusion paths, and freedom to permit volume change during lithium ion intercalation and de-intercalation. [source]


    Template-Free Synthesis of SnO2 Hollow Nanostructures with High Lithium Storage Capacity,

    ADVANCED MATERIALS, Issue 17 2006
    W. Lou
    A facile one-step template-free method based on a novel inside-out Ostwald ripening mechanism is developed for inexpensive mass preparation of hollow and hollow core/shell-type SnO2 nanostructures using potassium stannate as the precursor. As-prepared SnO2 hollow nanospheres (see figure) exhibit ultrahigh lithium storage capacity and improved cycle performance as high-energy anode materials in lithium-ion secondary batteries. [source]


    Open Metal Sites within Isostructural Metal,Organic Frameworks for Differential Recognition of Acetylene and Extraordinarily High Acetylene Storage Capacity at Room Temperature,

    ANGEWANDTE CHEMIE, Issue 27 2010
    Shengchang Xiang Dr.
    Ungesättigte Metallzentren in isostrukturellen Metall-organischen Gerüsten vom Typ [M2(DHTP)] (M=Co2+, Mn2+, Mg2+ und Zn2+; DHTP=2,5-Dihydroxyterephthalat) zeigen eine abgestufte molekulare Erkennung von Acetylen. Die extrem starke Wechselwirkung von Co2+ mit Acetylen (siehe Struktur) macht [Co2(DHTP)] zum bislang besten Acetylenspeichermaterial mit einer Kapazität von 230,cm3,cm,3 bei 295,K und 1,atm. [source]


    Maximizing the Localized Relaxation: The Origin of the Outstanding Oxygen Storage Capacity of ,-Ce2Zr2O8,

    ANGEWANDTE CHEMIE, Issue 44 2009
    Hai-Feng Wang
    Ziemlich leer: Die ausgezeichnete O-Speicherkapazität von ,-Ce2Zr2O8 (siehe Bild; Ce,grau, Zr,grün, O,rot) beruht auf dessen einzigartigen Strukturmerkmalen: Nach dem Entfernen von Sauerstoffatomen läuft eine lokalisierte Strukturrelaxation ab (Leerstellen in Braun), und sowohl diese lokalisierten Strukturrelaxationen selbst als auch ihre Zahl sind maximiert. [source]


    ChemInform Abstract: High Li+ -Ion Storage Capacity and Double-Electrochromic Behavior of Sol,Gel-Derived Iron Oxide Thin Films with Sulfate Residues.

    CHEMINFORM, Issue 41 2001
    Zhongchun Wang
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


    Experimental investigation of an adsorptive thermal energy storage

    INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 2 2007
    B. Dawoud
    Abstract A zeolite-water adsorption module, which has been originally constructed for an adsorption heat pump, has been experimentally investigated as an adsorptive thermal energy storage unit. The adsorber/desorber heat exchanger contains 13.2 kg of zeolite 13X and is connected to an evaporator/condenser heat exchanger via a butterfly valve. The flow rate of the heat transfer fluid in the adsorber/desorber unit has been changed between 0.5 and 2.0 l min,1, the inlet temperature to the evaporator between 10 and 40°C. It turned out that the higher the flow rate inside the adsorber/desorber unit the faster and more effective is the discharge of heat. However, at lower flow rates higher discharge temperatures are obtained. Storage capacities of 2.7 and 3.1 kWh have been measured at the evaporator inlet temperatures of 10 and 40°C, respectively, corresponding to thermal energy storage densities of 80 and 92 kWh m,3 based on the volume of the adsorber unit. The measured maximum power density increases from 144 to 165 kWh m,3 as the flow rate in the adsorber increases from 0.5 to 2 l min,1. An internal insulation in form of a radiation shield around the adsorber heat exchanger is recommended to reduce the thermal losses of the adsorptive storage. Copyright © 2006 John Wiley & Sons, Ltd. [source]


    Modelling rainfall interception loss in forest restoration trials in Panama

    ECOHYDROLOGY, Issue 3 2010
    Darryl E. Carlyle-Moses
    Abstract A modified Liu analytical model of rainfall interception (Ic) by tree canopies was evaluated using rainfall, throughfall and stemflow data collected from forest restoration trials in the Republic of Panama. The model uses an introduced approach to estimating the water storage capacities of tree boles, which has a more realistic physical basis than earlier iterations of the Liu model. Study species (Acacia mangium, Gliricidia sepium, Guazuma ulmifolia, Ochroma pyramidale, and Pachira quinata) were selected on the basis of differing leaf size and crown characteristics. Significant interspecific differences in both observed and simulated cumulative interception loss were found, with A. mangium intercepting more rainfall than other species. Errors between calculated and modelled cumulative Ic ranged from + 6·3% to + 30·5%, with modelled Ic always being the larger term. During-event evaporation rates from the study trees were positively related to tree height, crown area, and basal diameter. Crown area and the storage capacity of tree boles were negatively correlated. The results of a sensitivity analysis suggested that the modified model was most sensitive to variations in during-event evaporation rate. The implications of the model's sensitivity to during-event evaporation and the importance of this mechanism of interception loss are discussed, while suggestions are provided that may lead to further improvements to the analytical model. Copyright © 2010 John Wiley & Sons, Ltd. [source]


    Storage dynamics and streamflow in a catchment with a variable contributing area

    HYDROLOGICAL PROCESSES, Issue 16 2010
    C. Spence
    Abstract Storage heterogeneity effects on runoff generation have been well documented at the hillslope or plot scale. However, diversity across catchments can increase the range of storage conditions. Upscaling the influence of small-scale storage on streamflow across the usually more heterogeneous environment of the catchment has been difficult. The objective of this study was to observe the distribution of storage in a heterogeneous catchment and evaluate its significance and potential influence on streamflow. The study was conducted in the subarctic Canadian Shield: a region with extensive bedrock outcrops, shallow predominantly organic soils, discontinuous permafrost and numerous water bodies. Even when summer runoff was generated from bedrock hillslopes with small storage capacities, intermediary locations with large storage capacities, particularly headwater lakes, prevented water from transmitting to higher order streams. The topographic bounds of the basin thus constituted the maximum potential contributing area to streamflow and rarely the actual area. Topographic basin storage had little relation to basin streamflow, but hydrologically connected storage exhibited a strong hysteretic relationship with streamflow. This relationship defines the form of catchment function such that the basin can be defined by a series of storing and contributing curves comparable with the wetting and drying curves used in relating tension and hydraulic conductivity to water content in unsaturated soils. These curves may prove useful for catchment classification and elucidating predominant hydrological processes. Copyright © 2009 John Wiley & Sons, Ltd and Her Majesty the Queen in right of Canada. [source]


    Improved Hydrogen Storage Properties of Ti-Doped Sodium Alanate Using Titanium Nanoparticles as Doping Agents,

    ADVANCED MATERIALS, Issue 12 2003
    B. Bogdanovi
    By using nanosized doping agents, the properties of Ti-catalyzed NaAlH4 storage systems are considerably improved. Hydrogenation,dehydrogenation cyclic testing shows that with nanosized TiN dopants, storage capacities of 5 wt.-% H2 could be achieved. Doping with nanosized Ti brought hydrogenation times close to those required for practical applications, combined with high capacity (4.5 wt.-% H2, see Figure). [source]


    Genuine Episodic Memory Deficits and Executive Dysfunctions in Alcoholic Subjects Early in Abstinence

    ALCOHOLISM, Issue 7 2007
    Anne Lise Pitel
    Background: Chronic alcoholism is known to impair episodic memory function, but the specific nature of this impairment is still unclear. Moreover, it has never been established whether episodic memory deficit in alcoholism is an intrinsic memory deficit or whether it has an executive origin. Thus, the objectives are to specify which episodic memory processes are impaired early in abstinence from alcohol and to determine whether they should be regarded as genuine memory deficits or rather as the indirect consequences of executive impairments. Methods: Forty recently detoxified alcoholic inpatients at alcohol entry treatment and 55 group-matched controls underwent a neuropsychological assessment of episodic memory and executive functions. The episodic memory evaluation consisted of 3 tasks complementing each other designed to measure the different episodic memory components (learning, storage, encoding and retrieval, contextual memory, and autonoetic consciousness) and 5 executive tasks testing capacities of organization, inhibition, flexibility, updating, and integration. Results: Compared with control subjects, alcoholic patients presented impaired learning abilities, encoding processes, retrieval processes, contextual memory and autonoetic consciousness. However, there was no difference between the 2 groups regarding the storage capacities assessed by the rate of forgetting. Concerning executive functions, alcoholic subjects displayed deficits in each executive task used. Nevertheless, stepwise regression analyses showed that only performances on fluency tasks were significantly predictive of some of the episodic memory disorders (learning abilities for 40%, encoding processes for 20%, temporal memory for 21%, and state of consciousness associated with memories for 26%) in the alcoholic group. Discussion: At alcohol treatment entry, alcoholic patients present genuine episodic memory deficits that cannot be regarded solely as the consequences of executive dysfunctions. These results are in accordance with neuroimaging findings showing hippocampal atrophy. Moreover, given the involvement of episodic memory and executive functions in alcohol treatment, these data could have clinical implications. [source]


    Assessing sediment inputs to small reservoirs in Upper East Region, Ghana

    LAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 4 2009
    Afua Adwubi
    Abstract Many small dams and dugouts have been constructed in the Upper East Region of Ghana to address the problem of regional water scarcity. The reservoirs were constructed primarily as water supplies for agricultural irrigation and livestock watering, aquaculture and domestic use. However, many of the reservoirs dry up during the dry season, affecting the livelihoods of their basin inhabitants. A major cause for the dried reservoirs is siltation, which reduces the reservoir's storage capacities. The goal of this study is to quantify the annual siltation rate of four study reservoirs, using a bathymetric survey and reservoir soil sampling. The sediment yield and its relation to catchment area also were assessed. The results of this study indicate that the annual siltation rates are 1272, 3518, 2764 and 6135 t year,1 for Doba, Dua, Zebilla and Kumpalgogo reservoirs, respectively. Analyses of the sediment yield and catchment areas illustrated that the sediment yields decreased with increasing catchment area. All the study reservoirs have lost their dead storage capacity, which was meant to store sediment until the end of their anticipated design lives. The decreasing storage capacity because of siltation will affect the livelihoods of the local basin inhabitants, as the reservoirs will not be able to achieve all their intended purposes. The results of this study indicate that, because siltation is not the only factor threatening the benefits gained from the reservoirs, the integrated assessment of all relevant factors is required. [source]


    A two-echelon inventory-location problem with service considerations

    NAVAL RESEARCH LOGISTICS: AN INTERNATIONAL JOURNAL, Issue 8 2009
    Ho-Yin Mak
    Abstract We study the problem of designing a two-echelon spare parts inventory system consisting of a central plant and a number of service centers each serving a set of customers with stochastic demand. Processing and storage capacities at both levels of facilities are limited. The manufacturing process is modeled as a queuing system at the plant. The goal is to optimize the base-stock levels at both echelons, the location of service centers, and the allocation of customers to centers simultaneously, subject to service constraints. A mixed integer nonlinear programming model (MINLP) is formulated to minimize the total expected cost of the system. The problem is NP-hard and a Lagrangian heuristic is proposed. We present computational results and discuss the trade-off between cost and service. © 2009 Wiley Periodicals, Inc. Naval Research Logistics 2009 [source]


    Effects of water storage in the stele on measurements of the hydraulics of young roots of corn and barley

    NEW PHYTOLOGIST, Issue 3 2009
    Ankur Joshi
    Summary ,,In standard techniques (root pressure probe or high-pressure flowmeter), the hydraulic conductivity of roots is calculated from transients of root pressure using responses following step changes in volume or pressure, which may be affected by a storage of water in the stele. ,,Storage effects were examined using both experimental data of root pressure relaxations and clamps and a physical capacity model. Young roots of corn and barley were treated as a three-compartment system, comprising a serial arrangement of xylem/probe, stele and outside medium/cortex. The hydraulic conductivities of the endodermis and of xylem vessels were derived from experimental data. The lower limit of the storage capacity of stelar tissue was caused by the compressibility of water. This was subsequently increased to account for realistic storage capacities of the stele. ,,When root water storage was varied over up to five orders of magnitude, the results of simulations showed that storage effects could not explain the experimental data, suggesting a major contribution of effects other than water storage. ,,It is concluded that initial water flows may be used to measure root hydraulic conductivity provided that the volumes of water used are much larger than the volumes stored. [source]


    Measurement of xylem sap amino acid concentrations in conjunction with whole tree transpiration estimates spring N remobilization by cherry (Prunus avium L.) trees

    PLANT CELL & ENVIRONMENT, Issue 12 2002
    G. GRASSI
    Abstract Prunus avium trees were grown in sand culture for one vegetative season with contrasting N supplies, in order to precondition their N storage capacities. During the spring of the second year a constant amount of 15N was supplied to all the trees, and the recovery of unlabelled N in the new biomass production was used as a direct measure of N remobilization. Destructive harvests were taken during spring to determine the pattern of N remobilization and uptake. Measurements of both xylem sap amino acid profiles and whole tree transpiration rates were taken, to determine whether specific amino acids are translocated as a consequence of N remobilization and if remobilization can be quantified by calculating the flux of these amino acids in the xylem. Whereas remobilization started immediately after bud burst, N derived from uptake by root appeared in the leaves only 3 weeks later. The tree internal N status affected both the amount of N remobilization and its dynamics. The concentration of xylem sap amino acids peaked shortly after bud burst, concurrently with the period of fastest remobilization. Few amino acids and amides (Gln, Asn and Asp) were responsible for most of N translocated through the xylem; however, their relative concentration varied over spring, demonstrating that the transport of remobilized N occurred mainly with Gln whereas transport of N taken up from roots occurred mainly with Asn. Coupling measurements of amino acid N in the xylem sap with transpiration values was well correlated with the recovery of unlabelled N in the new biomass production. These results are discussed in relation to the possibility of measuring the spring remobilization of N in field-grown trees by calculating the flux of N translocation in the xylem. [source]


    Persistence of road runoff generation in a logged catchment in Peninsular Malaysia

    EARTH SURFACE PROCESSES AND LANDFORMS, Issue 13 2007
    Alan D. Ziegler
    Abstract Measurements of saturated hydraulic conductivity (Ks) and diagnostic model simulations show that all types of logging road/trail in the 14·4 ha Bukit Tarek Experimental Catchment 3 (BTEC3) generate substantial Horton overland flow (HOF) during most storms, regardless of design and level of trafficking. Near-surface Ks(0,0·05 m) on the main logging road, skid trails and newly constructed logging terraces was less than 1, 2 and 34 mm h,1, respectively. Near-surface Ks on an abandoned skid trail in an adjacent basin was higher (62 mm h,1), owing to the development of a thin organic-rich layer on the running surface over the past 40 years. Saturated hydraulic conductivity measured at 0·25 m below the surface of all roads was not different (all <6 mm h,1) and corresponded to the Ks of the adjacent hillslope subsoil, as most roads were excavated into the regolith more than 0·5,1 m. After 40 years, only limited recovery in near-surface Ks occurred on the abandoned skid trail. This road generated HOF after the storage capacity of the upper near-surface layer was exceeded during events larger than about 20 mm. Thus, excavation into low- Ks substrate had a greater influence on the persistence of surface runoff production than did surface compaction by machinery during construction and subsequent use during logging operations. Overland flow on BTEC3 roads was also augmented by the interception of shallow subsurface flow traveling along the soil,saprolite/bedrock interface and return flow emerging from the cutbank through shallow biogenic pipes. The most feasible strategy for reducing long-term road-related impacts in BTEC3 is limiting the depth of excavation and designing a more efficient road network, including minimizing the length and connectivity of roads and skid trails. Copyright © 2007 John Wiley & Sons, Ltd. [source]


    The role of vegetation patterns in structuring runoff and sediment fluxes in drylands

    EARTH SURFACE PROCESSES AND LANDFORMS, Issue 2 2005
    Juan Puigdefįbregas
    Abstract The dynamics of vegetation-driven spatial heterogeneity (VDSH) and its function in structuring runoff and sediment fluxes have received increased attention from both geomorphological and ecological perspectives, particularly in arid regions with sparse vegetation cover. This paper reviews the recent findings in this area obtained from field evidence and numerical simulation experiments, and outlines their implications for soil erosion assessment. VDSH is often observed at two scales, individual plant clumps and stands of clumps. At the patch scale, the local outcomes of vegetated patches on soil erodibility and hydraulic soil properties are well established. They involve greater water storage capacity as well as increased organic carbon and nutrient inputs. These effects operate together with an enhanced capacity for the interception of water and windborne resources, and an increased biological activity that accelerates breakdown of plant litter and nutrient turnover rates. This suite of relationships, which often involve positive feedback mechanisms, creates vegetated patches that are increasingly different from nearby bare ground areas. By this way a mosaic builds up with bare ground and vegetated patches coupled together, respectively, as sources and sinks of water, sediments and nutrients. At the stand scale within-storm temporal variability of rainfall intensity controls reinfiltration of overland flow and its decay with slope length. At moderate rainfall intensity, this factor interacts with the spatial structure of VDSH and the mechanism of overland flow generation. Reinfiltration is greater in small-grained VDSH and topsoil saturation excess overland flow. Available information shows that VDSH structures of sources and sinks of water and sediments evolve dynamically with hillslope fluxes and tune their spatial configurations to them. Rainfall simulation experiments in large plots show that coarsening VDSH leads to significantly greater erosion rates even under heavy rainfall intensity because of the flow concentration and its velocity increase. Copyright © 2005 John Wiley & Sons, Ltd. [source]


    Modelling rainfall interception loss in forest restoration trials in Panama

    ECOHYDROLOGY, Issue 3 2010
    Darryl E. Carlyle-Moses
    Abstract A modified Liu analytical model of rainfall interception (Ic) by tree canopies was evaluated using rainfall, throughfall and stemflow data collected from forest restoration trials in the Republic of Panama. The model uses an introduced approach to estimating the water storage capacities of tree boles, which has a more realistic physical basis than earlier iterations of the Liu model. Study species (Acacia mangium, Gliricidia sepium, Guazuma ulmifolia, Ochroma pyramidale, and Pachira quinata) were selected on the basis of differing leaf size and crown characteristics. Significant interspecific differences in both observed and simulated cumulative interception loss were found, with A. mangium intercepting more rainfall than other species. Errors between calculated and modelled cumulative Ic ranged from + 6·3% to + 30·5%, with modelled Ic always being the larger term. During-event evaporation rates from the study trees were positively related to tree height, crown area, and basal diameter. Crown area and the storage capacity of tree boles were negatively correlated. The results of a sensitivity analysis suggested that the modified model was most sensitive to variations in during-event evaporation rate. The implications of the model's sensitivity to during-event evaporation and the importance of this mechanism of interception loss are discussed, while suggestions are provided that may lead to further improvements to the analytical model. Copyright © 2010 John Wiley & Sons, Ltd. [source]


    Linking upstream channel instability to downstream degradation: Grenada Lake and the Skuna and Yalobusha River Basins, Mississippi

    ECOHYDROLOGY, Issue 3 2009
    Sean J. Bennett
    Abstract Unstable fluvial systems are characterized by actively migrating knickpoints, incising channel beds, failing banks, and recruitment of large woody debris and it would appear that river corridors downstream of these processes would be adversely affected or impaired because of higher fluxes of sediment and other riverine products. In north-central Mississippi, the Yalobusha River is one such system and the characteristics of two downstream locations are examined to explore this geomorphic linkage between upstream instability and downstream degradation. For the large woody debris plug along the Yalobusha River, it is found that (1) the deposit is composed mostly of sand covered with a veneer of silt and clay, (2) agrichemicals and enriched concentrations of elements are prevalent, and (3) excessive sedimentation and wood accumulation have forced river flow entirely out-of-bank. For Grenada Lake, it is found that (1) the impounded sediment is predominantly clay, (2) agrichemicals and elements observed throughout the reservoir show no spatial variation, (3) little difference exists in the amount and quality between the sediments deposited in Skuna and Yalobusha River arms, and (4) only a small fraction of the reservoir's storage capacity has been lost because of sedimentation. While excessive sedimentation and large woody debris recruitment have had a marked affect on stream corridor function in the area of the debris plug, the high sediment loads associated with the unstable portions of the Yalobusha River and their associated products have not been communicated to Grenada Lake. The fish consumption advisories within Grenada Lake and its tributaries due to bioaccumulated trace elements and agrichemicals, appear to be independent of the pervasive river channel instability occurring upstream. Copyright © 2009 John Wiley & Sons, Ltd. [source]


    Shapes of nonmonotonic activation functions in a chaotic neural network associative memory model and its evaluation

    ELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 3 2008
    Masanao Obayashi
    Abstract The purpose of this paper is to investigate the performance of the associative memory model using Aihara's chaotic neural network with different activation functions. Sigmoid function, a monotonic function, was used in Aihara's original model. However, in the static associative memory, it is reported that the storage capacity of the network is improved when a nonmonotonic function is used as the activation function. To improve the associative ability of chaotic neural network, kinds of nonmonotonic functions have been proposed to serve as activation function. This paper investigates their difference as to retrieval ability, and proposes an advanced nonmonotonic function. By computer simulation, we discuss what kind of shape is good regarding improving the associative ability of chaotic neural network. © 2008 Wiley Periodicals, Inc. Electron Comm Jpn, 91(3): 22, 27, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10070 [source]


    Nanoscale Grain Refinement and H-Sorption Properties of MgH2 Processed by High-Pressure Torsion and Other Mechanical Routes,

    ADVANCED ENGINEERING MATERIALS, Issue 8 2010
    Daniel Rodrigo Leiva
    MgH2 is a promising material for solid-state hydrogen storage due to its high gravimetric and volumetric storage capacity and its relatively low cost. Severe plastic deformation (SPD) processing techniques are being explored as an alternative to high-energy ball-milling (HEBM) in order to obtain more air resistant materials and reduce processing times. In this work, Mg, MgH2, and MgH2,Fe mixtures were severely mechanically processed by different techniques such as high-pressure torsion (HPT), extensive cold forging, and cold rolling. A very significant grain refinement was achieved when using MgH2 instead of Mg as raw material. The mean crystallite sizes observed ranged from 10 to 30,nm, depending on the processing conditions. Enhanced H-sorption properties were observed for the MgH2 -based nanocomposites processed by HPT when compared with MgH2 mixtures. Additionally, cold forging and cold rolling also proved effective in nanostructuring MgH2. These results suggest a high potential for innovative application with the use of low cost mechanical processing routes to produce Mg-based nanomaterials with attractive hydrogen storage properties. [source]


    Occurrence, prediction and hydrological effects of water repellency amongst major soil and land-use types in a humid temperate climate

    EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 5 2006
    S. H. Doerr
    Summary Knowledge of soil water repellency distribution, of factors affecting its occurrence and of its hydrological effects stems primarily from regions with a distinct dry season, whereas comparatively little is known about its occurrence in humid temperate regions such as typified by the UK. To address this research gap, we have examined: (i) water repellency persistence (determined by the water drop penetration time method, WDPT) and degree (determined by the critical surface tension method, CST) for soil samples (0,5, 10,15 and 20,25 cm depth) taken from 41 common soil and land-use types in the humid temperate climate of the UK; (ii) the supposed relationship of soil moisture, textural composition and organic matter content with sample repellency; and (iii) the bulk wetting behaviour of undisturbed surface core samples (0,5 cm depth) over a period of up to 1 week. Repellency was found in surface samples of all major soil textural types amongst most permanently vegetated sites, whereas tilled sites were virtually unaffected. Repellency levels reached those of the most severely affected areas elsewhere in the world, decreased in persistence and degree with depth and showed no consistent relationship with soil textural characteristics, organic matter or soil moisture contents, except that above a water content of c. 28% by volume, repellency was absent. Wetting rate assessments of 100 cm3 intact soil cores using continuous water contact (,20 mm pressure head) over a period of up to 7 days showed that across the whole sample range and irrespective of texture, severe to extreme repellency persistence consistently reduced the maximum water content at any given time to well below that of wettable soils. For slightly to moderately repellent soils the results were more variable and thus hydrological effects of such repellency levels are more difficult to predict. The results imply that: (i) repellency is common for many land-use types with permanent vegetation cover in humid temperate climates irrespective of soil texture; (ii) supposedly influential parameters (texture, organic matter, specific water content) are poor general predictors of water repellency, whereas land use and the moisture content below which repellency can occur seem more reliable; and (iii) infiltration and water storage capacity of very repellent soils are considerably less than for comparable wettable soils. [source]


    Ecophysiology of the filamentous Alphaproteobacterium Meganema perideroedes in activated sludge

    FEMS MICROBIOLOGY ECOLOGY, Issue 1 2005
    Caroline Kragelund
    Abstract A comprehensive study of the ecophysiology of the filamentous Meganema perideroedes affiliated to the Alphaproteobacteria, possessing a "Nostocoida limicola Type II" filamentous morphology was conducted. This morphotype often causes serious bulking problems in activated sludge wastewater treatment plants, and hardly anything is known about its physiology. The study was carried out by applying a suite of in situ methods in an industrial activated sludge treatment plant with excessive growth of this species. The experiments revealed a very versatile organism able to take up a large variety of organic substrates under aerobic conditions. It had a remarkably high storage capacity forming polyhydroxyalkanoates from most substrates tested. When nitrate was present as e-acceptor, the number of substrates to be consumed by M. perideroedes was more restricted compared to aerobic conditions. With nitrite as e-acceptor, only acetate and glucose among the substrates tested could be assimilated and used for storage and possibly growth. This indicated that M. perideroedes might be able to denitrify under certain conditions, which is unusual for filamentous bacteria in activated sludge. No substrate uptake or storage was seen under anaerobic conditions. M. perideroedes was relatively hydrophobic, compared to other filamentous bacteria and microcolonies present in the sludge, indicating the presence of a hydrophobic sheath. Several excreted surface-associated exoenzymes were detected in the sludge, but M. perideroedes never showed any activity, except once after a breakdown in the production facility. This confirmed that M. perideroedes mainly grows on soluble substrates. Based on the studies of the ecophysiology of M. perideroedes, potential control strategies are suggested. [source]


    Synthesis and Lithium Storage Properties of Co3O4 Nanosheet-Assembled Multishelled Hollow Spheres

    ADVANCED FUNCTIONAL MATERIALS, Issue 10 2010
    Xi Wang
    Abstract Single-, double-, and triple-shelled hollow spheres assembled by Co3O4 nanosheets are successfully synthesized through a novel method. The possible formation mechanism of these novel structures was investigated using powder X-ray diffraction, scanning and transmission electron microscopies, Fourier transform IR, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Both poly(vinylpyrrolidone) (PVP) soft templates and the formation of cobalt glycolate play key roles in the formation of these novel multishelled hollow structures. When tested as the anode material in lithium-ion batteries (LIBs), these multishelled microspheres exhibit excellent cycling performance, good rate capacity, and enhanced lithium storage capacity. This superior cyclic stability and capacity result from the synergetic effect of small diffusion lengths in the nanosheet building blocks and sufficient void space to buffer the volume expansion. This facile strategy may be extended to synthesize other transition metal oxide materials with hollow multishelled micro-/nanostrucutures, which may find application in sensors and catalysts due to their unique structural features. [source]


    Regulatory reform of the UK gas market: The sase of the storage auction

    FISCAL STUDIES, Issue 2 2001
    David Hawdon
    Abstract The UK gas industry has undergone major changes since it was privatised in 1986 as a fully integrated monopoly. The most significant of these has occurred not as a result of the privatisation legislation but by the intervention of the ordinary competition authorities in support of an active industry regulator. While price capping continues to be used as the primary instrument for welfare protection against the still substantial monopolistic powers of the incumbent, new competition (which has been positively encouraged) has had the greater impact on prices and choice. Recently, however, the regulator has encouraged the use of auctions for the sale of storage capacity. This paper considers the merits of auctions and makes a tentative evaluation of their effectiveness. Further use of auctions is recommended but reserve prices are considered inappropriate where monopoly power still remains. [source]


    Wettability alteration of caprock minerals by carbon dioxide

    GEOFLUIDS (ELECTRONIC), Issue 2 2007
    P. CHIQUET
    Abstract One of the critical factors that control the efficiency of CO2 geological storage process in aquifers and hydrocarbon reservoirs is the capillary-sealing potential of the caprock. This potential can be expressed in terms of the maximum reservoir overpressure that the brine-saturated caprock can sustain, i.e. of the CO2 capillary entry pressure. It is controlled by the brine/CO2 interfacial tension, the water-wettability of caprock minerals, and the pore size distribution within the caprock. By means of contact angle measurements, experimental evidence was obtained showing that the water-wettability of mica and quartz is altered in the presence of CO2 under pressures typical of geological storage conditions. The alteration is more pronounced in the case of mica. Both minerals are representative of shaly caprocks and are strongly water-wet in the presence of hydrocarbons. A careful analysis of the available literature data on breakthrough pressure measurements in caprock samples confirms the existence of a wettability alteration by dense CO2, both in shaly and in evaporitic caprocks. The consequences of this effect on the maximum CO2 storage pressure and on CO2 storage capacity in the underground reservoir are discussed. For hydrocarbon reservoirs that were initially close to capillary leakage, the maximum allowable CO2 storage pressure is only a fraction of the initial reservoir pressure. [source]


    Mesoporous Hydrous Manganese Dioxide Nanowall Arrays with Large Lithium Ion Energy Storage Capacities

    ADVANCED FUNCTIONAL MATERIALS, Issue 7 2009
    Dawei Liu
    Abstract Novel nanowall arrays of hydrous manganese dioxide MnO2,·,0.5H2O are deposited onto cathodic substrates by the potentiostatic method from a mixed aqueous solution of manganese acetate and sodium sulfate. The deposition is induced by a change of local pH resulting from electrolysis of H2O, and hierarchical mesoporous nanowall arrays are formed as a result of simultaneous precipitation of manganese hydroxide and release of hydrogen gas bubbles from the cathode. The morphology and lithium ion intercalation properties are found to change appreciably with the concentration of the precursor electrolyte, with a significant reduction in specific surface area with an increased precursor concentration. For example, mesoporous nanowall arrays deposited from 0.1,M solution possess a surface area of ,96,m2 g,1 and exhibit a stable high intercalation capacity of 256,mA hg,1 with a film of 0.5,µm in thickness, far exceeding the theoretical limit of 150,mA hg,1 for manganese dioxide bulk film. Such mesoporous nanowall arrays offer much greater energy storage capacity (e.g., ,230,mA hg,1 for films of ,2.5,µm) than that of anodic deposited films of the same thickness (,80,mA hg,1). Such high lithium ion intercalation capacity and excellent cyclic stability of the mesoporous nanowall arrays, especially for thicker films, are ascribed to the hierarchically structured macro- and mesoporosity of the MnO2,·,0.5H2O nanowall arrays, which offer large surface to volume ratio favoring interface Faradaic reactions, short solid-state diffusion paths, and freedom to permit volume change during lithium ion intercalation and de-intercalation. [source]


    Decadal change in wetland,woodland boundaries during the late 20th century reflects climatic trends

    GLOBAL CHANGE BIOLOGY, Issue 8 2010
    DAVID A. KEITH
    Abstract Wetlands are important and restricted habitats for dependent biota and play vital roles in landscape function, hydrology and carbon sequestration. They are also likely to be one of the most sensitive components of the terrestrial biosphere to global climate change. An understanding of relationships between wetland persistence and climate is imperative for predicting, mitigating and adapting to the impacts of future climate change on wetland extent and function. We investigated whether mire wetlands had contracted, expanded or remained stable during 1960,2000. We chose a study area encompassing a regional climatic gradient in southeastern Australia, specifically to avoid confounding effects of water extraction on wetland hydrology and extent. We first characterized trends in climate by examining data from local weather stations, which showed a slight increase in precipitation and marked decline in pan evaporation over the relevant period. Remote sensing of vegetation boundaries showed a marked lateral expansion of mires during 1961,1998, and a corresponding contraction of woodland. The spatial patterns in vegetation change were consistent with the regional climatic gradient and showed a weaker co-relationship to fire history. Resource exploitation, wildland fires and autogenic mire development failed to explain the observed expansion of mire vegetation in the absence of climate change. We therefore conclude that the extent of mire wetlands is likely to be sensitive to variation in climatic moisture over decadal time scales. Late 20th-century trends in climatic moisture may be related primarily to reduced irradiance and/or reduced wind speeds. In the 21st century, however, net climatic moisture in this region is projected to decline. As mires are apparently sensitive to hydrological change, we anticipate lateral contraction of mire boundaries in coming decades as projected climatic drying eventuates. This raises concerns about the future hydrological functions, carbon storage capacity and unique biodiversity of these important ecosystems. [source]


    Rainfall distribution is the main driver of runoff under future CO2 -concentration in a temperate deciduous forest

    GLOBAL CHANGE BIOLOGY, Issue 1 2010
    SEBASTIAN LEUZINGER
    Abstract Reduced stomatal conductance under elevated CO2 results in increased soil moisture, provided all other factors remain constant. Whether this results in increased runoff critically depends on the interaction of rainfall patterns, soil water storage capacity and plant responses. To test the sensitivity of runoff to these parameters under elevated CO2, we combine transpiration and soil moisture data from the Swiss Canopy Crane FACE experiment (SCC, 14 30,35 m tall deciduous broad-leaved trees under elevated CO2) with 104 years of daily precipitation data from an adjacent weather station to drive a three-layer bucket model (mean yearly precipitation 794 mm). The model adequately predicts the water budget of a temperate deciduous forest and runoff from a nearby gauging station. A simulation run over all 104 years based on measured sap flow responses resulted in only 5.5 mm (2.9%) increased ecosystem runoff under elevated CO2. Out of the 37 986 days (1 January 1901,31 December 2004), only 576 days produce higher runoff in the elevated CO2 scenario. Only 1 out of 17 years produces a CO2 -signal >20 mm a,1, which mostly depends on a few single days when runoff under elevated CO2 exceeds runoff under ambient conditions. The maximum signal for a double preindustrial CO2 -concentration under the past century daily rainfall regime is an additional runoff of 46 mm. More than half of all years produce a signal of <5 mm a,1, because trees consume the ,extra' moisture during prolonged dry weather. Increased runoff under elevated CO2 is nine times more sensitive to variations in rain pattern than to the applied reduction in transpiration under elevated CO2. Thus the key driver of increased runoff under future CO2 -concentration is the day by day rainfall pattern. We argue that increased runoff due to a first-order plant physiological CO2 -effect will be very small (<3%) in a landscape dominated by temperate deciduous forests, and will hardly increase flooding risk in forest catchments. Monthly rainfall sums are unsuitable to realistically model such CO2 effects. These findings may apply to other ecosystems with comparable soil water storage capacity. [source]


    Mechanisms and pathways of lateral flow on aspen-forested, Luvisolic soils, Western Boreal Plains, Alberta, Canada

    HYDROLOGICAL PROCESSES, Issue 21 2010
    Todd Redding
    Abstract Rainfall simulation experiments by Redding and Devito (2008, Hydrological Processes 23: 4287,4300) on two adjacent plots of contrasting antecedent soil moisture storage on an aspen-forested hillslope on the Boreal Plain showed that lateral flow generation occurred only once large soil storage capacity was saturated combined with a minimum event precipitation of 15,20 mm. This paper extends the results of Redding and Devito (2008, Hydrological Processes 23: 4287,4300) with detailed analysis of pore pressure, soil moisture and tracer data from the rainfall simulation experiments, which is used to identify lateral flow generation mechanisms and flow pathways. Lateral flow was not generated until soils were wet into the fine textured C horizon. Lateral flow occurred dominantly through the clay-rich Bt horizon by way of root channels. Lateral flow during the largest event was dominated by event water, and precipitation intensity was critical in lateral flow generation. Lateral flow was initiated as preferential flow near the soil surface into root channels, followed by development of a perched water table at depth, which also interacted with preferential flow pathways to move water laterally by the transmissivity feedback mechanism. The results indicate that lateral flow generated by rainfall on these hillslopes is uncommon because of the generally high available soil moisture storage capacity and the low probability of rainfall events of sufficient magnitude and intensity. Copyright © 2010 John Wiley & Sons, Ltd. [source]


    Potential of low cost close-range photogrammetry system in soil microtopography quantification

    HYDROLOGICAL PROCESSES, Issue 10 2009
    Mohamed A. M. Abd Elbasit
    Abstract Soil microtopography is a dynamic soil property which affects most soil-surface and water interaction processes. The importance of soil microtopography has been recognized for a long time, but only limited reports are available in the literature. In this study, the potential of using consumer-grade cameras and close-range photogrammetry procedures to quantify soil microtopography at plot-scale level (,1 m2) were assessed. Five fabricated gypsum surfaces with different degrees of roughness were used to simulate the soil surface conditions with different soil aggregates. The surfaces' digital elevation model (DEM) was generated using the photogrammetry system (PHM) involving a consumer-grade camera, and pin-microrelief meter (PM). The DEM generated using the PHM was assessed for accuracy, roughness indices (RI), depression area percentage (DA%), depression storage capacity (DSC), and micro-rills delineation in comparison with the PM. The accuracy was evaluated using the root mean square error (RMSE) in the x-, y-, and z-directions. Visual comparison between the 3D-visions of the DEM showed strong agreement between the DEM generated by the PHM and the PM, and between the PHM and the 2D images for the different gypsum surfaces. The average RMSE in the x-. y-, and z-direction were 2·08, 1·52, and 0·82 mm for the rough surface, and 4·42, 1·65, and 3·22 mm for the smooth surface. The RIs calculated from the two methods were highly correlated. The small discrepancy between the two methods was discussed. The micro-rills delineation was also similar for the two methods regarding the network density. The grid size did not effect the RI calculation, and has a strong influence on the DA%, DSC, and the delineated micro-rills orders. Results suggest that a consumer-grade camera and close-range photogrammetry have the potential to quantify the soil microtopography. Copyright © 2009 John Wiley & Sons, Ltd. [source]