Showing papers on "Water flow published in 2012"

Water desalination across nanoporous graphene

Abstract: We show that nanometer-scale pores in single-layer freestanding graphene can effectively filter NaCl salt from water. Using classical molecular dynamics, we report the desalination performance of such membranes as a function of pore size, chemical functionalization, and applied pressure. Our results indicate that the membrane’s ability to prevent the salt passage depends critically on pore diameter with adequately sized pores allowing for water flow while blocking ions. Further, an investigation into the role of chemical functional groups bonded to the edges of graphene pores suggests that commonly occurring hydroxyl groups can roughly double the water flux thanks to their hydrophilic character. The increase in water flux comes at the expense of less consistent salt rejection performance, which we attribute to the ability of hydroxyl functional groups to substitute for water molecules in the hydration shell of the ions. Overall, our results indicate that the water permeability of this material is several ...

Energy consumption and constant current operation in membrane capacitive deionization

Abstract: Membrane capacitive deionization (MCDI) is a water desalination technology based on applying a cell voltage between two oppositely placed porous electrodes sandwiching a spacer channel that transports the water to be desalinated. In the salt removal step, ions are adsorbed at the carbon–water interface within the micropores inside the porous electrodes. After the electrodes reach a certain adsorption capacity, the cell voltage is reduced or even reversed, which leads to ion release from the electrodes and a concentrated salt solution in the spacer channel, which is flushed out, after which the cycle can start over again. Ion-exchange membranes are positioned in front of each porous electrode, which has the advantage of preventing the co-ions from leaving the electrode region during ion adsorption, while also allowing for ion desorption at reversed voltage. Both effects significantly increase the salt removal capacity of the system per cycle. The classical operational mode of MCDI at a constant cell voltage results in an effluent stream of desalinated water of which the salt concentration varies with time. In this paper, we propose a different operational mode for MCDI, whereby desalination is driven by a constant electrical current, which leads to a constant salt concentration in the desalinated stream over long periods of time. Furthermore, we show how the salt concentration of the desalinated stream can be accurately adjusted to a certain setpoint, by either varying the electrical current level and/or the water flow rate. Finally, we present an extensive dataset for the energy requirements of MCDI, both for operation at constant voltage and at constant current, and in both cases also for the related technology in which membranes are not included (CDI). We find consistently that in MCDI the energy consumption per mole of salt removed is lower than that in CDI. Within the range 10–200 mM ionic strength of the water to be treated, we find for MCDI a constant energy consumption of ∼22 kT per ion removed. Results in this work are an essential tool to evaluate the economic viability of MCDI for the treatment of saltwater.

Indirect evaporative cooling : Past, present and future potentials

Abstract: This paper reported a review based study into the Indirect Evaporative Cooling (IEC) technology, which was undertaken from a variety of aspects including background, history, current status, concept, standardisation, system configuration, operational mode, research and industrialisation, market prospect and barriers, as well as the future focuses on RD good distribution of the water stream across the wet surface of the exchanger plate (tube) and adequate (matching up the evaporation) control of the water flow rate are critical to achieving the expected system performance. It was noticed that the IEC devices were always in combined operation with other cooling measures and the commonly available IEC related operational modes are (1) IEC/DEC system; (2) IEC/DEC/mechanical vapour compression system; (3) IEC/desiccant system; (4) IEC/chilled water system; and (5) IEC/heat pipe system. The future potential operational modes may also cover the IEC-inclusive fan coil units, air handle units, cooling towers, solar driven desiccant cycle, and Rankine cycle based power generation system etc. Future works on the IEC technology may focus on (1) heat exchanger structure and material; (2) water flowing, distribution and treatment; (3) incorporation of the IEC components into conventional air conditioning products to enable combined operation between the IEC and other cooling devices; (4) economic, environment and social impacts; (5) standardisation and legislation; (6) public awareness and other dissemination measures; and (7) manufacturing and commercialisation. All above addressed efforts may help increase the market ratio of the IEC to around 20% in the next 20 years, which will lead to significant saving of fossil fuel consumption and cut of carbon emission related to buildings.

Auxin regulates aquaporin function to facilitate lateral root emergence

Abstract: Aquaporins are membrane channels that facilitate water movement across cell membranes. In plants, aquaporins contribute to water relations. Here, we establish a new link between aquaporin-dependent tissue hydraulics and auxin-regulated root development in Arabidopsis thaliana. We report that most aquaporin genes are repressed during lateral root formation and by exogenous auxin treatment. Auxin reduces root hydraulic conductivity both at the cell and whole-organ levels. The highly expressed aquaporin PIP2;1 is progressively excluded from the site of the auxin response maximum in lateral root primordia (LRP) whilst being maintained at their base and underlying vascular tissues. Modelling predicts that the positive and negative perturbations of PIP2;1 expression alter water flow into LRP, thereby slowing lateral root emergence (LRE). Consistent with this mechanism, pip2;1 mutants and PIP2;1-overexpressing lines exhibit delayed LRE. We conclude that auxin promotes LRE by regulating the spatial and temporal distribution of aquaporin-dependent root tissue water transport.

Rock and Soil Mechanics

Abstract: 1. Definition and Subject of the Discipline. Nature of the discipline and interdisciplinary connections. Discontinuity and granularity. Multicomponent structure. 2. Mechanical Models of Rocks and Soils. Description of the models. The concepts of rheology of a continuum. The model of an elastic body. Linear rheological models. Piecewise linear models. Terzaghi's hydrodynamic model. Discrete model for rocks and soils. Shear resistance of soils. 3. Properties of Rocks and Soils. Physical properties of rocks. Physical properties of soils. Rheological properties of rocks. Rheological parameters of soils. The properties of frozen soils. 4. Viscoelasticity in Soil and Rock Mechanics. Distribution of stresses in the substratum. Deformations of the substratum and slopes. The in-situ state of a rock mass. Excavations in a rock stratum. Problems associated with drilling. Discrete models of rock strata. 5. Groundwater Flow. Equations of groundwater movement. Two-dimensional groundwater flow problem. Some practical problems. Seepage in scarps and slopes. Drainage of the ground and excavations. Water flow in rock strata. 6. Outline of the Theory of Consolidation of Porous Deformable Media. Brief outline of the history of the theory of consolidation. Quasi-stationary problems. Dynamic problems of the theory of consolidation. Thermoconsolidation. 7. Plasticity and Limit States. Constitutive relations for elastic-plastic models of rocks and soils. The limit state conditions. Limit analysis. Examples of application of approximate methods. The method of characteristics. 8. Mechanics of the Clay Fraction. Data and assumption. Physical fundamentals. Clay particles and ground water. The primary structure of the clay-water fluid. Movements of a structure element. Action of isotropic pressure (consolidation). Action of the stress deviator. Rheological models of primary clay. Structural changes of clay-water fluid. The oriented clay-water fluid. Clayey soils. Creep in clayey soils. (All chapters include References). Index.

Calibration and use of the polar organic chemical integrative sampler—a critical review

Abstract: The implementation of strict environmental quality standards for polar organic priority pollutants poses a challenge for monitoring programs. The polar organic chemical integrative sampler (POCIS) may help to address the challenge of measuring low and fluctuating trace concentrations of such organic contaminants, offering significant advantages over traditional sampling. In the present review, the authors evaluate POCIS calibration methods and factors affecting sampling rates together with reported environmental applications. Over 300 compounds have been shown to accumulate in POCIS, including pesticides, pharmaceuticals, hormones, and industrial chemicals. Polar organic chemical integrative sampler extracts have been used for both chemical and biological analyses. Several different calibration methods have been described, which makes it difficult to directly compare sampling rates. In addition, despite the fact that some attempts to correlate sampling rates with the properties of target compounds such as log K(OW) have been met with varying success, an overall model that can predict uptake is lacking. Furthermore, temperature, water flow rates, salinity, pH, and fouling have all been shown to affect uptake; however, there is currently no robust method available for adjusting for these differences. Overall, POCIS has been applied to a wide range of sampling environments and scenarios and has been proven to be a useful screening tool. However, based on the existing literature, a more mechanistic approach is required to increase understanding and thus improve the quantitative nature of the measurements.

Saline and Sodic Soils: Principles-Dynamics-Modeling

Abstract: 1 Diagnosis and Properties.- 1.1 Sources of Salts.- 1.1.1 Rainfall.- 1.1.2 Mineral Weathering.- 1.1.3 Fossil Salts.- 1.1.4 Man's Activities.- 1.2 Some Water Quality and Soil Solution Parameters.- 1.2.1 Common Water Quality Parameters.- 1.2.1.1 Total Salt Concentration.- 1.2.1.2 Electrical Conductivity (EC).- 1.2.1.3 Chemical Analyses.- 1.2.1.4 Sodium Adsorption Ratio (SAR).- 1.2.1.5 Langelier Index (pHc).- 1.2.1.6 Specific Ion Hazards.- 1.2.2 Physical Characterization of Soil Water.- 1.2.2.1 Soil Water Potential.- 1.2.2.2 Pressure and Head Equivalents of Soil Water Potential.- 1.2.2.3 Water (Solution) Retentivity Curve.- 1.2.2.4 Modeling of the Soil-Water-Salt Retentivity Function h(? C, R).- 1.2.3 Simplified Interactions of Irrigation Waters and Rainfall with Soils.- 1.2.3.1 Basic Concentration and Displacement Processes.- 1.2.3.2 Ion Exchange Phenomena.- 1.2.3.3 Dissolving and Precipitation of Minerals.- 1.3 Surface Phenomena of Salt-Affected Soils.- 1.3.1 Soil Minerals and Their Properties.- 1.3.1.1 Common Soil Minerals.- 1.3.1.2 Some Relevant Surface Properties of Soils.- 1.3.1.3 Water Retention and Swelling.- 1.3.1.4 Effects of Salts on Soil Hydraulic Parameters..- 1.3.1.5 Modeling of Hydraulic Conductivity K (?, R, C) Based upon Soil Water Retentivity.- 1.3.2 Ion Exchange and Exclusion.- 1.3.2.1 Mass Action Approaches.- 1.3.2.2 Diffuse Double Layer Approach.- 1.3.2.3 The Gapon Equation.- 1.3.2.4 Modeling of Na-Ca Exchange Equilibria.- 1.3.2.5 Anion Exclusion.- 1.3.2.6 Modeling of Anion Exclusion.- 1.3.2.7 Estimating the Osmotic Efficiency Coefficient Function ? (?,c).- 1.3.3 Retention of Uncharged Solutes.- 1.4 Salt Dissolution and Precipitation.- 1.4.1 Primary Minerals.- 1.4.2 Carbonate Minerals.- 1.4.3 Evaporite Minerals.- 1.5 Diagnosis of Salinity Problems.- 1.5.1 Diagnostic Parameters.- 1.5.2 Saline Conditions.- 1.5.3 Sodic Conditions.- 1.5.4 Other Salinity Problems.- 2 Transportation and Distribution of Salts.- 2.1 Water Movement Processes.- 2.1.1 Flow of Viscous Fluid.- 2.1.2 Darcy's Equation.- 2.1.3 Unsteady (Transient) Water Flow.- 2.1.4 Vapor Flow.- 2.1.5 Infiltration of Water into Soils.- 2.1.6 Redistribution of Soil Water.- 2.2 Salt Transport in Soils.- 2.2.1 Transport by Diffusion Without Solution Flow.- 2.2.2 Transport of Salt by Convection.- 2.2.3 Combined Effects of Diffusion and Convection on Salt Transport.- 2.2.4 Miscible Displacement in Soils.- 2.2.5 Solute Reflection During Water Flow.- 2.2.6 Solute Chromatography in Soils.- 2.2.6.1 Qualitative Description.- 2.2.6.2 Quantitative Description of Chromatographic Processes.- 2.2.6.3 Application of Chromatographic Theories to Soil Systems.- 2.2.7 Effects of Salinity on Soil Water Transmission Rates.- 2.2.7.1 Effects of Salt Concentration Gradients.- 2.2.7.2 Modified Solution Flux Equation.- 2.3 Modeling of Salt-Flow Phenomena.- 2.3.1 Mathematical and Numerical Models.- 2.3.2 Mathematical Modeling of Transport Phenomena in Soils.- 2.3.3 Numerical Methods Applied to Transient Flow Problems.- 2.3.3.1 Finite-Difference Methods.- 2.3.3.2 Finite Element Method.- 2.3.4 Salt Dynamics and Distribution in Fallow Soils.- 2.3.4.1 Noninteractive Solute.- 2.3.4.2 Solute Interacting with Soil.- 2.3.5 Modeling of Salt Dynamics and Distribution in Soils Under Crop Growing Conditions.- 2.3.5.1 Models for Water Extraction by Crop Roots.- 2.3.5.2 Computed Salt Distribution Profiles and Measured Data.- 2.3.6 Solute Dispersion and Distribution in Heterogeneous Field Soils.- 2.3.6.1 Piston Flow Profiles.- 2.3.6.2 Dispersive Profiles.- 3 Management.- 3.1 Crop Salt Tolerance.- 3.1.1 Osmotic Effects.- 3.1.2 Specific-Ion Effects.- 3.1.3 Plant Sensitivity.- 3.1.4 Crop Selection.- 3.2 Irrigation Practice.- 3.2.1 Irrigation Water Quality.- 3.2.2 Water Quality Classifications.- 3.2.3 Leaching Requirement.- 3.2.4 Drainage Water Quality.- 3.2.5 Salt Balance.- 3.3 Reclamation of Saline and Sodic Soils.- 3.3.1 Reclaiming Saline Soils by Leaching.- 3.3.2 The Use of Mulches and Other Surface Management to Enhance Salt Leaching.- 3.3.3 Gypsum Use for Reclaiming Sodic Soils.- 3.3.4 High Salt Water Leaching.- 3.3.5 Deep Mixing Sodic Soils for Reclamation.- 3.3.6 Sulfuric Acid for Reclaiming Sodic Soils.- 3.4 Solute Flow Models Applied to Irrigation Management Optimization.- 3.4.1 Reclamation of Saline Soils by Leaching.- 3.4.2 Quantity-Quality Substitutions of Water During the Irrigation Season.- 3.4.2.1 Modeling of Crop Response to Soil Salinity..- 3.4.2.2 Optimizing the Quantity-Quality Combination of the Irrigation Water.- 3.4.3 Models for the Economic Evaluation of Salinity in Irrigation Water Management.- 3.4.3.1 Least Cost Quantity-Quality Combinations Based on the Critical-Threshold Concept.- 3.4.3.2 Optimal Irrigation Management Based on the Total Potential Approach.- 3.4.3.3 Modeling of Optimal Irrigation Scheduling.- 3.5 Specialized Management Practices.- References.

Ten iterative steps for model development and evaluation applied to Computational Fluid Dynamics for Environmental Fluid Mechanics

Abstract: Computational Fluid Dynamics (CFD) is increasingly used to study a wide variety of complex Environmental Fluid Mechanics (EFM) processes, such as water flow and turbulent mixing of contaminants in rivers and estuaries and wind flow and air pollution dispersion in urban areas. However, the accuracy and reliability of CFD modeling and the correct use of CFD results can easily be compromised. In 2006, Jakeman et al. set out ten iterative steps of good disciplined model practice to develop purposeful, credible models from data and a priori knowledge, in consort with end-users, with every stage open to critical review and revision (Jakeman et al., 2006). This paper discusses the application of the ten-steps approach to CFD for EFM in three parts. In the first part, the existing best practice guidelines for CFD applications in this area are reviewed and positioned in the ten-steps framework. The second and third part present a retrospective analysis of two case studies in the light of the ten-steps approach: (1) contaminant dispersion due to transverse turbulent mixing in a shallow water flow and (2) coupled urban wind flow and indoor natural ventilation of the Amsterdam ArenA football stadium. It is shown that the existing best practice guidelines for CFD mainly focus on the last steps in the ten-steps framework. The reasons for this focus are outlined and the value of the additional - preceding - steps is discussed. The retrospective analysis of the case studies indicates that the ten-steps approach is very well applicable to CFD for EFM and that it provides a comprehensive framework that encompasses and extends the existing best practice guidelines.

HYDRUS: Model Use, Calibration, and Validation

Abstract: The HYDRUS numerical models are widely used for simulating water flow and solute transport in variably saturated soils and groundwater. Applications involve a broad range of steady-state or transient water flow, solute transport, and/or heat transfer problems. They include both short-term, one-dimensional laboratory column flow or transport simulations, as well as more complex, long-duration, multi-dimensional field studies. The HYDRUS models can be used for both direct problems when the initial and boundary conditions for all involved processes and corresponding model parameters are known, as well as inverse problems when some of the parameters need to be calibrated or estimated from observed data. The approach to model calibration and validation may vary widely depending upon the complexity of the application. Model calibration and inverse parameter estimation can be carried out using a relatively simple, gradient-based, local optimization approach based on the Marquardt-Levenberg method, which is directly implemented into the HYDRUS codes, or more complex global optimization methods, including genetic algorithms, which need to be run separately from HYDRUS. In this article, we provide a brief overview of the HYDRUS codes, discuss which HYDRUS parameters can be estimated using internally built optimization routines and which type of experimental data can be used for this, and review various calibration approaches that have been used in the literature in combination with the HYDRUS codes.

Coconut-Shell-Based Porous Carbons with a Tunable Micro/Mesopore Ratio for High-Performance Supercapacitors

Abstract: Granular micro/mesoporous carbon with a ratio of mesopore to total pore volume (Vmeso/Vtotal) greater than 75% was prepared using coconut shells as a precursor by a one-step thermal treatment, i.e., combined pyrolysis and steam activation process. The process variables, such as final activation temperature, time, and water flow rate were studied. The N2 adsorption isotherms of the samples were of type IV, indicating mesoporous characteristics. The mesoporosity of the resultant porous carbons prepared by this method is greater than the one of those prepared by the conventional two separate pyrolysis and activation processes. Experimental results showed that the yield of porous carbon was proportional to the final pyrolysis temperature and activation time. Additionally, with the increase of activation time and water flow rate, the mesoporosity increased considerably. When the activation time and water flow rate were kept constant, the mesoporosity also increased with a rise in the final pyrolysis temperatur...

Simplified evaporation method for determining soil hydraulic properties: a reinvestigation of linearization errors

Abstract: Accurate knowledge of the soil hydraulic properties is a prerequisite for reliable modelling of soil water dynamics. As a consequence, many methods have been developed to derive these constitutive relationships either under field or laboratory conditions. Among these methods, the simplified evaporation method conducted on soil samples in the laboratory has found widespread use and application, mainly due to its relative ease of implementation and its straightforward evaluation of the experimental data. This method, however, relies on various simplifying assumptions. A common approach to assess the validity of these assumptions and to explore potential linearization errors associated with them is the use of synthetic data. In the past, such synthetic data were generated using rather simplistic models considering liquid water flow in capillaries only. In this study, we reinvestigated the accuracy of the simplified evaporation method using a more realistic process description of evaporative drying of the soil sample, including both liquid water flow in capillaries and films, as well as isothermal water vapour diffusion. In contrast to previous results reported in the literature, our results show that the simplifying assumptions used to evaluate the experimental data may result in biased estimates of the soil hydraulic properties, particularly for coarse textured soils. The bias typically increased progressively during stage-two evaporation, which is characterized by the development of a dry surface layer in which water flow is dominated by diffusion of water vapour, resulting in strongly nonlinear pressure head and water content profiles. We investigated various strategies for correcting for this bias caused by simplifying assumptions.

Spatial and temporal trends for water-flow velocity and bed-material sediment transport in the lower Mississippi River

Abstract: Where rivers near the coastline, the receiving basin begins to influence flow, and gradually varied, nonuniform flow conditions arise. The section of the river affected by nonuniform flow is typically referred to as the backwater segment, and for large lowland rivers, this portion of the river can extend many hundreds of kilometers above the outlet. River morphology and kinematics vary in the backwater segment; however, these channel properties have not been explicitly related to properties of the flow and sediment-transport fields. This study examines the influence of spatially and temporally varying flow velocity and sediment transport on channel properties for the lower 800 km of the Mississippi River, a section of the river that includes the backwater segment. Survey transects (n = 2650) were used to constrain the cross-sectional area of water flow every ∼312 m along the Mississippi River channel for eight successive intervals of water discharge. Assuming conservation of water discharge, the local flow velocity was calculated at each transect by dividing water discharge by the local measurement of cross-sectional flow area. Calculated flow velocity was converted to total bed stress using a dimensionless friction coefficient that was determined by optimizing the match between a predicted and a measured water-surface profile. Estimates for the skin-friction component of the total bed stress were produced from the values for total shear stress using a form-drag correction. These skin-friction bed-stress values were then used to model bed-material transport. Results demonstrate that in the lower Mississippi River, cross-sectional flow area increases downstream during low- and moderate-water discharge. This generates a decrease in calculated water-flow velocity and bed-material transport. During high-water discharge, the trend is reversed: Cross-sectional flow area decreases downstream, producing an increase in calculated water-flow velocity and bed-material transport. An important contribution of this work is the identification of a downstream reversal in the trend for channel cross-sectional area due to variable water discharge. By accounting for the spatial divergences in sediment transport predicted over an average annual hydrograph, we demonstrate the tendency for channel-bed aggradation in much of the backwater reach of the Mississippi River (150–600 km above the outlet); however, a region of channel-bed erosion is calculated for the final 150 km. These results help to explain the spatial variability of channel morphology and kinematics for the lower Mississippi River, and they can be extended to other lowland river systems near the coastline.

Daisy: Model Use, Calibration, and Validation

Abstract: Daisy is a soil-plant-atmosphere system model focusing on agro-ecosystems. It simulates water, heat, carbon, and nitrogen balances as well as crop production and pesticide fate in agro-ecosystems subjected to various management strategies. The basic scale of application is the field (management unit), which may be simulated in one or two dimensions. Daisy allows several different process descriptions for water flow, evapotranspiration, crop growth, and solute transport. Furthermore, it can operate in a distributed mode (several fields) and link up with distributed hydrological models. In this case, statistical and remote sensing data are relevant. Considerations concerning the objective of a given study and available data determine the choice of process descriptions. All applications require information concerning weather (at minimum, daily values of solar radiation, air temperature, and precipitation), soil (texture, organic matter, hydraulic parameters, etc.), location of groundwater, and vegetation cover. Applications that focus on nitrogen dynamics require a description of crop rotation, tillage, use of fertilizer and manure, irrigation, sowing, harvesting, and organic matter turnover in the soil. In carbon and nitrogen balance simulations, the uncertainty associated with crop growth is particularly important because Daisy only considers water and nitrogen stress. Dry matter and nitrogen yield may require calibration. Uncertainty associated with initialization of the organic matter pools and the parameterization of organic fertilizers is considered to be of major importance. For pesticide transport calculations, descriptions of macroporosity and hydraulic conditions close to the surface are critical. Daisy has been validated in several international comparative validation studies.

A simple three-dimensional macroscopic root water uptake model based on the hydraulic architecture approach

Abstract: Many hydrological models including root water uptake (RWU) do not consider the dimension of root system hydraulic architecture (HA) because explicitly solving water flow in such a complex system is too time consuming. However, they might lack process understanding when basing RWU and plant water stress predictions on functions of variables such as the root length density distribution. On the basis of analytical solutions of water flow in a simple HA, we developed an “implicit” model of the root system HA for simulation of RWU distribution (sink term of Richards’ equation) and plant water stress in three-dimensional soil water flow models. The new model has three macroscopic parameters defined at the soil element scale, or at the plant scale, rather than for each segment of the root system architecture: the standard sink fraction distribution SSF, the root system equivalent conductanceKrs and the compensatory RWUconductance Kcomp. It clearly decouples the process of water stress from compensatory RWU, and its structure is appropriate for hydraulic lift simulation. As compared to a model explicitly solving water flow in a realistic maize root system HA, the implicit model showed to be accurate for predicting RWU distribution and plant collar water potential, with one single set of parameters, in dissimilar water dynamics scenarios. For these scenarios, the computing time of the implicit model was a factor 28 to 214 shorter than that of the explicit one.We also provide a new expression for the effective soil water potential sensed by plants in soils with a heterogeneous water potential distribution, which emerged from the implicit model equations. With the proposed implicit model of the root system HA, new concepts are brought which open avenues towards simple and mechanistic RWU models and water stress functions operational for field scale water dynamics simulation.

Leaf surface structures enable the endemic Namib desert grass Stipagrostis sabulicola to irrigate itself with fog water

Abstract: The Namib grass Stipagrostis sabulicola relies, to a large degree, upon fog for its water supply and is able to guide collected water towards the plant base. This directed irrigation of the plant base allows an efficient and rapid uptake of the fog water by the shallow roots. In this contribution, the mechanisms for this directed water flow are analysed. Stipagrostis sabulicola has a highly irregular surface. Advancing contact angle is 98° ± 5° and the receding angle is 56° ± 9°, with a mean of both values of approximately 77°. The surface is thus not hydrophobic, shows a substantial contact angle hysteresis and therefore, allows the development of pinned drops of a substantial size. The key factor for the water conduction is the presence of grooves within the leaf surface that run parallel to the long axis of the plant. These grooves provide a guided downslide of drops that have exceeded the maximum size for attachment. It also leads to a minimum of inefficient drop scattering around the plant. The combination of these surface traits together with the tall and upright stature of S. sabulicola contributes to a highly efficient natural fog-collecting system that enables this species to thrive in a hyperarid environment.

Rheotaxis in Larval Zebrafish Is Mediated by Lateral Line Mechanosensory Hair Cells

Abstract: The lateral line sensory system, found in fish and amphibians, is used in prey detection, predator avoidance and schooling behavior. This system includes cell clusters, called superficial neuromasts, located on the surface of head and trunk of developing larvae. Mechanosensory hair cells in the center of each neuromast respond to disturbances in the water and convey information to the brain via the lateral line ganglia. The convenient location of mechanosensory hair cells on the body surface has made the lateral line a valuable system in which to study hair cell damage and regeneration. One way to measure hair cell survival and recovery is to assay behaviors that depend on their function. We built a system in which orientation against constant water flow, positive rheotaxis, can be quantitatively assessed. We found that zebrafish larvae perform positive rheotaxis and that, similar to adult fish, larvae use both visual and lateral line input to perform this behavior. Disruption or damage of hair cells in the absence of vision leads to a marked decrease in rheotaxis that recovers upon hair cell repair or regeneration.

Adaptation of grain legumes to climate change: a review

Abstract: Humanity is heading toward the major challenge of having to increase food production by about 50% by 2050 to cater for an additional three billion inhabitants, in a context of arable land shrinking and degradation, nutrient deficiencies, increased water scarcity, and uncertainty due to predicted climatic changes. Already today, water scarcity is probably the most important challenge, and the consensual prediction of a 2–4°C degree increase in temperature over the next 100 years will add new complexity to drought research and legume crop management. This will be especially true in the semi-arid tropic areas, where the evaporative demand is high and where the increased temperature may further strain plant–water relations. Hence, research on how plants manage water use, in particular, on leaf/root resistance to water flow will be increasingly important. Temperature increase will variably accelerate the onset of flowering by increasing thermal time accumulation in our varieties, depending on their relative responses to day length, ambient, and vernalizing temperature, while reducing the length of the growing period by increasing evapotranspiration. While the timeframe for these changes (>10–20 years) may be well in the realm of plant adaptation within breeding programs, there is a need for today’s breeding to understand the key mechanisms underlying crop phenology at a genotype level to better balance crop duration with available soil water and maximize light capture. This will then be used to re-fit phenology to new growing seasons under climate change conditions. The low water use efficiency, i.e., the amount of biomass or grain produced per unit of water used, under high vapor pressure deficit, although partly offset by an increased atmospheric CO2 concentration, would also require the search of germplasm capable of maintaining high water use efficiency under such conditions. Recent research has shown an interdependence of C and N nutrition in the N performance of legumes, a balance that may be altered under climate change. Ecophysiological models will be crucial in identifying genotypes adapted to these new growing conditions. An increased frequency of heat waves, which already happen today, will require the development of varieties capable of setting and filling seeds at high temperature. Finally, increases in temperature and CO2 will affect the geographical distribution of pests, diseases, and weeds, presenting new challenges to crop management and breeding programs.

Floodplain restoration enhances denitrification and reach-scale nitrogen removal in an agricultural stream.

Abstract: Streams of the agricultural Midwest, USA, export large quantities of nitrogen, which impairs downstream water quality, most notably in the Gulf of Mexico. The two-stage ditch is a novel restoration practice, in which floodplains are constructed alongside channelized ditches. During high flows, water flows across the floodplains, increasing benthic surface area and stream water residence time, as well as the potential for nitrogen removal via denitrification. To determine two-stage ditch nitrogen removal efficacy, we measured denitrification rates in the channel and on the floodplains of a two-stage ditch in north-central Indiana for one year before and two years after restoration. We found that instream rates were similar before and after the restoration, and they were influenced by surface water NO3− concentration and sediment organic matter content. Denitrification rates were lower on the constructed floodplains and were predicted by soil exchangeable NO3− concentration. Using storm flow simulations, we found that two-stage ditch restoration contributed significantly to NO3− removal during storm events, but because of the high NO3− loads at our study site, <10% of the NO3− load was removed under all storm flow scenarios. The highest percentage of NO3− removal occurred at the lowest loads; therefore, the two-stage ditch's effectiveness at reducing downstream N loading will be maximized when the practice is coupled with efforts to reduce N inputs from adjacent fields.

Performance analysis of water cooled concentrated photovoltaic (CPV) system

Abstract: The concentrated photovoltaic (CPV) system focuses solar radiation on the solar cells. CPV systems need to track the sun for keeping the reflected radiation focussed on the solar cell. A CPV module and its active water-cooling system are developed at the School of Energy and Environment, Southeast University, China and its performance has been reported here. This developed system has been used for testing the PV module’s performance for different parameters such as operating temperature, power output, and efficiency. The experimental results show that the operating temperature of the CPV module under water cooling is reduced under 60 1C and therefore the efficiency of the CPV has increased and produced the more electric power output. The effect of water flow rate has been analyzed for the CPV efficiency and output.