High Conductivity Levels Research Articles

Validation of BaIn0.3Ti0.7O2.85 as SOFC Electrolyte with Nd2NiO4, LSM and LSCF as Cathodes

AbstractDue to its high ionic conductivity level, BaIn0.3Ti0.7O2.85 (BIT07) is a potential electrolyte material for SOFC. In order to validate the use of this material, its chemical, mechanical and electromechanical compatibilities with three classical cathode materials (La0.7Sr0.3MnO3 – δ (LSM), La0.58Sr0.4Co0.2Fe0.8O3 – δ (LSCF) and Nd2NiO4 + δ) have been tested. The chemical compatibility has been demonstrated by XRD experiments, which show that BIT07 does not react with the cathode materials below 1,000 °C. The mechanical compatibility has been investigated by combining measurements of the thermal expansion coefficients of the cathode materials from X‐ray thermo diffraction and SEM observations. Symmetrical cells cathode/electrolyte/cathode have been studied by electrochemical impedance spectroscopy in order to quantify the quality of the cathode/electrolyte interface and to study the long‐term stability of the cell. The main conclusion of the study is that LSCF presents the best compromise between an acceptable mechanical compatibility and very good electrical properties with BIT07.

Assessing water use and quality through youth participatory research in a rural Andean watershed

Water availability, use and quality in a rural watershed of the Colombian Andes were investigated through participatory research involving local youth. Research included the quantification of disaggregated water use at the household level; comparison of water use with availability; monitoring water quality of streams, community water intakes and household faucets; and the determination of land use – water quality interactions. Youth were involved in all aspects of the research from design to implementation, dissemination of results and remediation options. Quantification of domestic and on-farm water use, and water availability indicated that water availability was sufficient during the study period, but that only an 8% decrease in dry season supply would result in shortages. Elevated conductivity levels in the headwaters were related to “natural” bank erosion, while downstream high conductivity and coliform levels were associated with discharges from livestock stalls and poorly maintained septic tanks in the stream buffer zone. Through the involvement of youth as co-investigators, the knowledge generated by the research was appropriated at the local level. Community workshops led by local youth promoted water conservation and water quality protection practices based on research, and resulted in broader community participation in water management. The approach involving youth in research stimulated improved management of both land and water resources, and could be applied in small rural watersheds in developed or developing countries.

Nafion–clay nanocomposite membranes: Morphology and properties

A series of Nafion–clay nanocomposite membranes were synthesized and characterized. To minimize any adverse effects on ionic conductivity the clay nanoparticles were H + exchanged prior to mixing with Nafion. Well-dispersed, mechanically robust, free-standing nanocomposite membranes were prepared by casting from a water suspension at 180 °C under pressure. SAXS profiles reveal a preferential orientation of Nafion aggregates parallel to the membrane surface, or normal plane. This preferred orientation is induced by the platy nature of the clay nanoparticles, which tend to align parallel to the surface of the membrane. The nanocomposite membranes show dramatically reduced methanol permeability, while maintaining high levels of proton conductivity. The hybrid films are much stiffer and can withstand much higher temperatures compared to pure Nafion. The superior thermomechanical, electrochemical and barrier properties of the nanocomposite membranes are of significant interest for direct methanol fuel cell applications.

Ceria based mixed conductors with adjusted electronic conductivity in the bulk and/or along grain boundaries

Ceramic samples of Ce 1 − x Pr xO 2 − δ (CPO) and Ce 1 − x Gd xO 2 − δ (CGO) were obtained by different sintering schedules, including the use of cobalt as a sintering aid, added by mixing the precursor powders with cobalt nitrate solution; this allowed one to obtain different microstructural features and to change the transport properties, with emphasis on changes in grain boundary behaviour. Cobalt plays a double effect as sintering aid and also to induce important changes of grain boundary properties. Specific changes of grain boundary properties were ascribed by de-convolution of impedance spectra. Relatively high levels of mixed conductivity could be attained by adding a lanthanide species to yield ionic transport, whereas electronic conduction was promoted by the mixed valence character of PrO x, combined with the additional contribution of Co-rich grain boundaries. These effects can be used to tune preferential electronic conductivity at bulk or grain boundary level. Oxygen permeability and a modified e.m.f. method were used to obtain the overall ionic transport number under oxidising conditions and its dependence on processing conditions. Additions of PrO x induce bulk electronic conduction which assumes a greater role at lower temperatures. Further enhancement of electronic conductivity is attained by effects of Co-addition. Though Co-rich grain boundaries also yield significant levels of electronic conductivity in CGO, this contribution becomes minor at intermediate temperatures, due to differences between the activation energies for electronic and ionic conduction.

GROWING MEDIA FOR THE NURSERY INDUSTRY: USE OF AMENDMENTS IN TRADITIONAL BARK-BASED MEDIA

GROWING MEDIA FOR THE NURSERY INDUSTRY: USE OF AMENDMENTS IN TRADITIONAL BARK-BASED MEDIA

The incorporation of single-walled carbon nanotubes into polymerized high internal phase emulsions to create conductive foams with a low percolation threshold

New methods for the incorporation of single-walled carbon nanotubes (SWCNTs) into styrene-divinylbenzene-based high internal phase emulsions (HIPEs) are addressed with specific attention to minimizing the SWCNT loading while maintaining a high level of conductivity of the final polyHIPE–SWCNT composites. Stable HIPEs were achieved using sodium dodecyl sulfate-stabilized SWCNTs, thus eliminating the necessity of SWCNT functionalization. PolyHIPE–SWCNT composites were made with water: oil ratios (vol/vol) of 75:25 and of 84:16. The percolation threshold was determined to be 0.2 and 0.1 wt%, respectively. These threshold values are lower than that obtained for non-porous, polystyrene–SWCNT composites made by means of a latex-based route followed by melt-processing.

Responses of aquatic organisms to metal pollution in a lowland river in Flanders: A comparison of diatoms and macroinvertebrates

The role of macroinvertebrates and diatoms as indicator for metal pollution was investigated by assessing both biota along a metal gradient in the Belgian river the Dommel. Macroinvertebrates and diatoms were sampled in summer and winter and physical–chemical characteristics of the water were measured at four different sample periods and related to sediment characteristics. Although metal concentrations, except cadmium, in the water nowhere exceeded water quality standards, high metal concentrations were measured in the sediment, indicating historical contamination of the Dommel. At the sites that were situated downstream of the pollution source, high levels of conductivity and chloride were measured in the water. Redundancy Analysis (RDA) indicated pH, phosphate and zinc as the significant environmental variables explaining each respectively 7.7%, 11.6% and 22.6% of the macroinvertebrate community composition. Two clusters could be separated, with Gammarus pulex, Leptocerus interruptus, Baetis rhodani and Cloeon dipterum associated with low zinc concentrations and Tubificidae, Asellus aquaticus, Erpobdella sp. and Chironomus thummi-plumosus associated with higher zinc concentrations. Ammonium (10.6%), conductivity (16.5%), chloride (11.4%) and zinc (5.9%) turned out to be significant variables explaining the diatom community structure. Based on physical–chemical differences and species composition, three different groups could be separated. With this Tabellaria flocculosa and Fragilaria capucina var. rumpens were associated with low metal concentrations, Gomphonema parvulum and Nitzschia palea with elevated concentrations and Eolimna minima and Sellaphora seminulum with high zinc concentrations. In conclusion, the diatom community best reflected the metal gradient. With regard to water quality indices, those based on macroinvertebrates best followed the metal pollution gradient and were most strongly correlated with physical–chemical variables of water and sediment. This study indicated that to assess the effect of metal pollution in lowland rivers, the combined use of macroinvertebrates and diatoms is more appropriate than the use of both biota separately.

Landfill Cover Soil, Soil Solution, and Vegetation Responses to Municipal Landfill Leachate Applications

Municipal solid waste landfill leachate must be removed and treated to maintain landfill cover integrity and to prevent contamination of surface and ground waters. From 2003 to 2007, we studied an onsite disposal system in Ottawa County, Michigan, where leachate was spray irrigated on the vegetated landfill cover. We established six 20-m-diameter circular experimental plots on the landfill; three were spray irrigated as part of the operational system, and three remained as untreated control plots. We quantified the effects of leachate application on soil properties, soil solution chemistry, vegetative growth, and estimated solute leaching. The leachate had high mean levels of electrical conductivity (0.6-0.7 S m(-1)), Cl (760-900 mg L(-1)), and NH(4)-N (290-390 mg L(-1)) but was low in metals and volatile organic compounds. High rates of leachate application in 2003 (32 cm) increased soil electrical conductivity and NO(3)-N leaching, so a sequential rotation of spray areas was implemented to limit total leachate application to <9.6 cm yr(-1) per spray area. Concentrations of NO(3)-N and leaching losses remained higher on irrigated plots in subsequent years but were substantially reduced by spray area rotation. Leachate irrigation increased plant biomass but did not significantly affect soil metal concentrations, and plant metal concentrations remained within normal ranges. Rotating spray areas and timing irrigation to conform to seasonal capacities for evapotranspiration reduced the localized impacts of leachate application observed in 2003. Careful monitoring of undiluted leachate applications is required to avoid adverse impacts to vegetation or soils and elevated solute leaching losses.

Ameliorating caustic properties of aluminum extraction residue to establish a vegetative cover

High pH, electrical conductivity (E.C.), and extractable Na levels in the residue remaining after aluminum was extracted from bauxite were greater than can support vigorous plant growth. These caustic properties must be ameliorated so that vegetation could be established on the surface of large disposal ponds. Fresh residue was added to 14 field lysimeters of dimensions 3 m long × 3 m wide × 1 m deep. Internal drainage was enhanced in some lysimeters and restricted in others. Gypsum applied at the rate of 7.5% of the weight of the top 15 cm of residue in selected lysimeters. These management issues were studied to determine how their influence would lower chemical properties to support vegetation. Residue samples were removed annually for 5 years after the lysimeters were established to determine changes in pH, E.C., and extractable Na and Al over time. Plant species C. dactylon (bermudagrass), Atriplex nummalari (oldman saltbush), and Atriplex canescens (fourwing saltbush) were planted either as seeds or transplants beginning the third year after lysimeter establishment. Residue pH, E.C. Na, and Al decreased annually, but more gradually in restricted drainage. Species survival in the enhanced drainage treatments was more vigorous with gypsum amendments beginning in the third year after lysimeter establishment. This coincided with a decrease in the mean pH below 9.5 and decrease in mean E.C. below 10 dS/m. Extractable Na and Al did not seem to influence survivability. Survival of seeded and transplanted C. dactylon was greater than the two Atriplex spp. each year. This study proved that the caustic properties of this residue could be lowered enough to support vegetation, but not without appropriate drainage. The addition of gypsum amendments and appropriate amounts of supplemental water would accelerate the timeframe for vegetation establishment probably at a level commensurate with the application rate of both inputs in a well-drained system.

Study of Soil Fertility and Plant Nutrition of Proteas Cultivated under Subtropical Conditions

: A study of soil physicochemical characteristics and mineral nutrition of four cultivars of Leucospermum cordifolium (‘Scarlett Ribbon,’ ‘High Gold,’ ‘Veldifre,’ ‘Sunrise’) and Leucospermum patersonii species was carried out along 2 years in commercial protea plantations, distributed throughout a subtropical region (La Palma Island, Canarian Archipelago). Soils presented a slightly acid pH range, whereas organic matter showed suitable values. Generally, available soil phosphorus (P) contents were less than 25 mg kg−1, with high available potassium (K) and calcium (Ca) levels, though the ratio of Ca of the sum of available cations was usually appropriate. Despite the high electrical conductivity (EC) levels (4.31–8.87 dS m−1) determined in some soils, no salinity symptoms were ever detected. Distribution and behavior of foliar nutrients nitrogen (N), P, K, Ca, magnesium (Mg), and sodium (Na) along time showed that nutritional needs varied in some cases among cultivars and species. L. patersonii presented the least N concentration, whereas ‘High Gold’ and ‘Veldfire’ had the greatest levels. Data denoted that P requirements were larger in younger plants, during the recovery after pruning, and while new buds developed. ‘Sunrise’ cultivar stood out for its large foliar levels of P, whereas ‘Scarlett Ribbon’ and ‘Veldfire’ had the least K contents. As a general pattern, K decreased in winter samplings. L. patersonii species and the cultivar ‘Sunrise’ exhibited the highest Ca values, and the same was true for Mg only in the species. A special need for Na appeared in all the cultivars and species studied. L. patersonii and the cultivar ‘Sunrise’ showed the greatest Na levels. A general stabilization of nutrient concentrations was observed in the fourth, fifth, and/or sixth samplings, so that November is recommended for taking samples for current foliar analysis. In this context, foliar ranges for the studied nutrients are suggested.

On the influence of the processing conditions on the performance of electrically conductive carbon nanotube/polymer nanocomposites

We prepared multiwalled carbon nanotube/polystyrene (MWCNT/PS) nanocomposites using a latex-based process, the main step of which consists of directly mixing an aqueous suspension of exfoliated MWCNTs and a PS latex, both stabilized by an anionic surfactant. After freeze drying and compression molding homogeneous polymer films with well-dispersed carbon nanotubes were produced as evidenced by scanning electron microscopy. Conductivity measurements performed on our nanocomposite films show that they have a low percolation threshold and exhibit high levels of electrical conductivity above this threshold. We observe that both these properties are influenced by the applied processing conditions, i.e., temperature and time, and provide a plausible explanation based on the diffusive motion of the MWNTs in the polymer melt during the compression molding stage.

Attenuation characteristics of near-field electromagnetic noise through microstrip line for magnetic absorbers with different levels of conductivity

Attenuation characteristics of near-field electromagnetic noise through microstrip line attached with electromagnetic thick films with different levels of electrical conductivity for frequencies in the range of 0.1–6GHz were investigated with numerical simulation via the three dimensional finite-element high-frequency structure simulator (HFSS) code. The electromagnetic absorption of the semiconducting magnetic or nonmagnetic films highly increased up to 80% at above 1GHz, while the absorption of the nonmagnetic conductor or the insulating films was significantly diminished. The remarkable enhancement in the loss factor of the semiconducting magnetic or nonmagnetic films was attributed to the increase in loss factor of the eddy-current loss. Even though the reflection of the semiconducting magnetic films at above 58S∕m was significantly lowered by the magnetic loss effect compared to that of the semiconducting nonmagnetic films, the reflection below 1GHz was still high enough to incur electromagnetic interferences. It was confirmed from the numerical results of magnetic field that the radiation noise was highly generated with increasing conductivity at above 58S∕m because of the rereflection of the radiated noise from the surface of the magnetic films with high level of conductivity. As a result, the near-field electromagnetic noise was effectively reduced by controlling conductivity to the semiconducting level of below 5.8S∕m for the magnetic films with high permeability in the measured frequency.

IMPACTS OF ROAD DEICING SALT ON THE DEMOGRAPHY OF VERNAL POOL-BREEDING AMPHIBIANS

Deicing agents, primarily road salt, are applied to roads in 26 states in the United States and in a number of European countries, yet the scale of impacts of road salt on aquatic organisms remains largely under-studied. The issue is germane to amphibian conservation because both adult and larval amphibians are known to be particularly sensitive to changes in their osmolar environments. In this study, we combined survey, experimental, and demographic modeling approaches to evaluate the possible effects of road salt on two common vernal-pond-breeding amphibian species, the spotted salamander (Ambystoma maculatum) and the wood frog (Rana sylvatica). We found that in the Adirondack Mountain Region of New York (USA), road salt traveled up to 172 m from the highway into wetlands. Surveys showed that egg mass densities of spotted salamanders (A. maculatum) and wood frogs (R. sylvatica) were two times higher in forest pools than roadside pools, but this pattern was better explained by road proximity than by increased salinity. Experiments demonstrated that embryonic and larval survival were reduced at moderate (500 muS) and high conductivities (3000 muS) in A. maculatum and at high conductivities in R. sylvatica. Demographic models suggest that such egg and larval stage effects of salt may have important impacts on populations near roads, particularly in the case of A. maculatum, for which salt exposure may lead to local extinction. For both species, the effect of road salt was dependent upon the strength of larval density dependence and declined rapidly with distance from the roadside, with the greatest negative effects being limited to within 50 m. Based on this evidence, we argue that efforts to protect local populations of A. maculatum and R. sylvatica in roadside wetlands should, in part, be aimed at reducing application of road salt near wetlands with high conductivity levels.

Fluorites: Superionics and Conduction Processes

AbstractThe superionic conducting properties of fluorite structured compounds are discussed in this paper, starting with a brief historical overview of the topic. The current state of knowledge concerning the dynamic lattice disorder associated with the high values of ionic conductivity is summarized and illustrated using three examples taken from the author’s research program. These are chosen to highlight different aspects of the structure-property relationships within fluorite-structured superionics and, in particular, demonstrate the role of the neutron diffraction technique in investigations of compounds showing high levels of ionic conductivity. The paper concludes with an overview of some current developments within this research field.

Natural and propagated algal flora isolated from El-Fayum Governorate

A total of 98 taxa (69 aquatic, 29 edaphic) of algae were isolated and identified from water and soil samples collected in El-Fayum governorate. Aquatic taxa were made up of Bacillariophytes (33 taxa), Cyanophytes (20) and Chlorophytes (16), while soil taxa consisted of Cyanophytes (16 taxa), Chlorophytes (8), Bacillariophytes (4) and one euglenoid taxon. Diversity increased under culturing and propagation with artificial nutritive media, particulary cyanophytes (by 18 taxa) and chlorophytes (by 7 taxa). Bacillariophytes dominated in Qarun Lake, perhaps because of the high silicate content; Qarun Lake had low diversity of chlorophytes and cyanophytes, perhaps because of the high levels of electrical conductivity and Na+. The greatest numbers of chlorophytes were associated with high Mg++ content. Edaphic pH values were slightly alkaline to alkaline. Soil algal flora were commonest in samples from the Wadi El-Rayan road, characterized by high silt and clay fractions. Keywords : Qarun lake; Wadi El-Rayan; Egypt. Egyptian Journal of Biology Vol. 10 2008: pp. 54-61

제주도의 지하수 관측망 자료를 이용한 지하수위 및 전기전도도 변화 해석

Water sources in volcanic Jeju Island are almost entirely dependent on groundwater because there are actually no perennial streams or rivers due to the permeable nature of surface soils derived from basaltic or trachytic rocks. Uncontrolled development of groundwater resulted in substantial water-level decline, groundwater pollution, and seawater intrusion in several places of the island. To maintain its sustainable groundwater, the provincial government has declared some parts of the island as the Special Groundwater Conservation/Management Area since 1994. Hence, all the activities for the groundwater development in the area should obtain official permit from relevant authorities. Furthermore, to acquire information on groundwater status, a network of groundwater monitoring was established to cover most of the low land and coastal areas with the installation of automatic monitoring systems since 2001. The analysis of the groundwater monitoring data indicated that the water levels had decreased at coastal area, especially in northern part of the island. Moreover, very high electrical conductivity (EC) levels and their increasing trends were observed in the eastern part, which was ascribable to seawater intrusion by intensive pumping in recent years. Water level decline and EC rise in the coastal area are expected to continue despite the present strict control on additional groundwater development.

Order–disorder transitions in poly(3,4-ethylenedioxythiophene)

The commonly held perception that high conductivity in conducting polymers is linked to a high level of π-stacking order in the material is shown here to be of lesser importance in highly conducting poly(3,4-ethylenedioxythiophene) (PEDT), which has been prepared by chemical vapour phase polymerisation. Despite the fact that there is a highly energetic phase transition about 130°C (110J/g), and that this transition corresponds to a loss of the long-range π-stacking as observed in grazing angle XRD, the conductivity remains unchanged beyond the transition and only decreases by a factor of two when heating to above 200°C. The XRD data suggest that order in two dimension remains above the phase transition measured by DSC and this order is sufficient to maintain a high level of electronic conductivity. Furthermore, as the ligand on the iron salt used in the synthesis is varied, the conductivity of the PEDT varies over two orders of magnitude. These phenomena cannot be explained by different degree of doping or crystallinity and it is proposed that the iron salt has an ordering effect during the vapour phase polymerisation.

Application of High Copper and Zinc Compost and Its Effects on Soil Properties and Growth of Barley

A compost of high copper (Cu) and zinc (Zn) content was added to soil, and the growth of barley (Hordeum vulgare L.) was evaluated. Four treatments were established, based on the addition of increasing quantities of compost (0, 2, 5, and 10% w/w). Germination, plant growth, biomass production, and element [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sodium (Na), magnesium (Mg), iron (Fe), Cu, manganese (Mn), and Zn] contents of soil and barley were determined following a 16‐week growing period. Following harvesting of the barley, analysis of the different mixtures of soil and compost was performed. Micronutrient contents in soils as affected by compost additions were determined with diethylene–triamine–pentaacetic acid (DTPA) (Cu, Mn, Fe, and Zn) or ammonium acetate [Ca, Na, Mg, K, cation exchange capacity (CEC)] extractions, and soils levels were compared to plant uptake where appropriate. Increasing rates of compost had no affect on Ca, Mg, or K concentration in barley. Levels of Cu, Zn, Mn, and Na, however, increased with compost application. High correlations were found for DTPA‐extractable Cu and Zn with barley head and shoot content and for Mn‐DTPA and shoot Mn content. Ammonium acetate–extractable Na was highly correlated with Na content in the shoot. High levels of electrical conductivity (EC), Cu, Zn, and Na may limit utilization of the compost.

Estudio de las torres de refrigeración asociadas a brotes comunitarios de legionelosis

Objetive To evaluate the factors of risk of the risk cooling towers associated to a community outbreak of legionellosis according to its characteristics of maintenance and the quality of the water with the purpose of improving the systems of prevention of this one disease. Method To compare the piece of information gathered between the 4 types of cooling towers: control 1, control 2, probable and confirmed. A total of 184 cooling towers have been studied associated to 17 community outbreak of legionellosis of the province of Barcelona (Spain) during the year 2004, of which 112 are control 1, 54 control 2, 8 probable and 10 confirmed. Results The confirmed towers are characterized by: high levels of conductivity, total aerobes, calcic hardness, total solids in dissolution, temperature and turbidity; low levels of chlorine (< 2 ppm); of use hypochlorite as disinfectant in a 10%; greater degree of breach of the revision program and cleaning of the internal elements of the tower (tray, stuffed and separating of drops); degree of performance of the periodic disinfections and the cleaning of deposits of the 100%. A 47% of the investigated towers do not use the previous treatments of the water in spite of diminishing the parametric values of the quantitatives variables. Conclusions Measures of prevention of the legionellosis would be due to guarantee: a good quality of the water and the pursuit of its quantitatives variables; chlorine levels superior to 2 ppm; the evaluation of the individual risk for each installation; the performance of the 100% of the program of revision of the internal elements of the towers.

Study of refrigeration towers associated with community outbreaks of legionellosis

OBJECTIVE To evaluate the factors of risk of the risk cooling towers associated to a community outbreak of legionellosis according to its characteristics of maintenance and the quality of the water with the purpose of improving the systems of prevention of this one disease. METHOD To compare the piece of information gathered between the 4 types of cooling towers: control 1, control 2, probable and confirmed. A total of 184 cooling towers have been studied associated to 17 community outbreak of legionellosis of the province of Barcelona (Spain) during the year 2004, of which 112 are control 1, 54 control 2, 8 probable and 10 confirmed. RESULTS The confirmed towers are characterized by: high levels of conductivity, total aerobes, calcic hardness, total solids in dissolution, temperature and turbidity; low levels of chlorine (< 2 ppm); of use hypochlorite as disinfectant in a 10%; greater degree of breach of the revision program and cleaning of the internal elements of the tower (tray, stuffed and separating of drops); degree of performance of the periodic disinfections and the cleaning of deposits of the 100%. A 47% of the investigated towers do not use the previous treatments of the water in spite of diminishing the parametric values of the quantitatives variables. CONCLUSIONS Measures of prevention of the legionellosis would be due to guarantee: a good quality of the water and the pursuit of its quantitatives variables; chlorine levels superior to 2 ppm; the evaluation of the individual risk for each installation; the performance of the 100% of the program of revision of the internal elements of the towers.