Conductivity Research Articles

Integrated versus isolated scenario for prediction dissolved oxygen at progression of water quality monitoring stations

Abstract. This study examined the potential of Multi-layer Perceptron Neural Network (MLP-NN) in predicting dissolved oxygen (DO) at Johor River Basin. The river water quality parameters were monitored regularly each month at four different stations by the Department of Environment (DOE) over a period of ten years, i.e. from 1998 to 2007. The following five water quality parameters were selected for the proposed MLP-NN modelling, namely; temperature (Temp), water pH, electrical conductivity (COND), nitrate (NO3) and ammonical nitrogen (NH3-NL). In this study, two scenarios were introduced; the first scenario (Scenario 1) was to establish the prediction model for DO at each station based on five input parameters, while the second scenario (Scenario 2) was to establish the prediction model for DO based on the five input parameters and DO predicted at previous station (upstream). The model needs to verify when output results and the observed values are close enough to satisfy the verification criteria. Therefore, in order to investigate the efficiency of the proposed model, the verification of MLP-NN based on collection of field data within duration 2009–2010 is presented. To evaluate the effect of input parameters on the model, the sensitivity analysis was adopted. It was found that the most effective inputs were oxygen-containing (NO3) and oxygen demand (NH3-NL). On the other hand, Temp and pH were found to be the least effective parameters, whereas COND contributed the lowest to the proposed model. In addition, 17 neurons were selected as the best number of neurons in the hidden layer for the MLP-NN architecture. To evaluate the performance of the proposed model, three statistical indexes were used, namely; Coefficient of Efficiency (CE), Mean Square Error (MSE) and Coefficient of Correlation (CC). A relatively low correlation between the observed and predicted values in the testing data set was obtained in Scenario 1. In contrast, high coefficients of correlation were obtained between the observed and predicted values for the test sets of 0.98, 0.96 and 0.97 for all stations after adopting Scenario 2. It appeared that the results for Scenario 2 were more adequate than Scenario 1, with a significant improvement for all stations ranging from 4 % to 8 %.

Optimal environmental range for Juncus effusus, an important plant species in an endangered insect species (Nannopya pygmaea) habitat in Korea

Juncus effusus is mostly found in freshwater wetlands and is widely used for landscaping and creating artificial wetlands due to its high ecological value. J. effusus tends to dominate during the early stage (3-10 years) of the second succession in abandoned paddy fields. This study focused on the environmental characteristics of J. effusus to create habitat for an endangered species, Nannopya pygmaea, which lives in wetlands dominated by J. effusus. Considering the distribution of J. effusus and N. pygmaea, 63 quadrats at eight wetlands were investigated between May and June 2006 during the critically dry period. Fifty-three species from 28 families co-occurred with J. effusus, and Persicaria thunbergii was the most abundant (63.5%). The optimal ranges of distribution (ORD) for the water variables were water depth, -2 to 10 cm; dissolved oxygen, 0.99-3.55 mg/kg, conductivity (CON), 23.40-115.40 <TEX>${\mu}s/cm$</TEX>, total dissolved solid, 12.53-57.60 mg/L; pH, 5.00-6.87; <TEX>$K^+$</TEX>, 0.11-1.46 mg/L; <TEX>$Ca^{2+}$</TEX>, 1.53-5.85 mg/L; <TEX>$Na^+$</TEX>, 3.16-7.47 mg/L; <TEX>$Mg^{2+}$</TEX>, 0.11-1.96 mg/L; <TEX>$NO_3$</TEX>-N, < 0.001-0.072 mg/L; <TEX>$NH_4$</TEX>-N, 0.005-0.097 mg/L; and <TEX>$PO_4$</TEX>-P, 0.006-0.047 mg/L. ORDs for the soil variables were water content, 1.05-2.96%; loss-on ignition method (LOI), 5.07-7.81%; CON, 23.70-59.70 <TEX>${\mu}s/cm$</TEX>; pH, 4.40-5.16; extracted (e) <TEX>$K^+$</TEX>, 4.34-15.73 cmol/kg; <TEX>$eCa^{2+}$</TEX>, 31.56-191.56 cmol/kg; <TEX>$eNa^+$</TEX>, < 0.01-2.61 cmol/kg; eMg, 0.04-19.82 cmol/kg; <TEX>$eNO_3$</TEX>-N, 0.514-1.175 mg/kg; <TEX>$eNH_4$</TEX>-N, 0.033-0.974 mg/kg, <TEX>$ePO_4$</TEX>-P, 0.491-11.552 mg/kg; total nitrogen, 0.016-0.200%; and total carbon, 1.06-2.37%. The appearance of rush during early succession indicated relatively lower levels of these physicochemical parameters, and that ORDs should be maintained for the J. effusus community.

Evolution of streaming potential near the borehole during drilling

The theoretical approach to the description of dynamics of an electric field near the borehole result� ing from penetration of drilling mud filtrate into the collector under the influence of excessive pressure during drilling is developed. Water based drilling mud containing a solid clay fraction, the most abundant in drilling procedures, is considered. The evolution of hydrophysical properties and electric conductivity of the nearborehole zone during borehole drilling is well studied for vertical (1, 2) and less for horizontal (3) boreholes. Realistic mathematical models have been developed, and the evolution of streaming potential in connection with filtration of drilling mud in per� meable rocks has been considered for the widely applied method of the streaming potential. The streaming potential appears as a result of electroki� netic effects in the nearborehole zone and changes in time with the depth of filtrate penetration and growth of the mudcake on the wall of the borehole. Calculations performed on the basis of the suggested mathematical model particularly demonstrate that, under definite drilling regimes, change in permeable zone depth by several tens of centimeters results in such variations of the potential on the wall of the borehole which may be registered by probes with a standard resolution (several mV). MATHEMATICAL MODEL The excess of pressure in the borehole over the for� mation pressure during drilling and other operations in the borehole results in penetration of fluid different from that in the rock that influences the evolution of electrophysical properties of the nearborehole zone. Information about the depth of the permeable zone is important for interpretation of the data of electromag� netic well logging, as well as for subsequent exploita� tion. The question about the possibility of estimation of the depth of the permeable zone by measurement of the streaming potential on the wall of the borehole may be reduced to study of the electric field near the borehole depending on the position of the penetration front at which parameters such as electric conductiv� ity, hydraulic permeability, and others have jumps.

Geographical Information System Techniques for Evaluation of Groundwater Quality

Problem statement: The present paper tries to assess groundwater suit ability for irrigation purpose in Damghan plain (5400 ha). Approach: Twenty four water samples were collected from the active wells. Parameters such as Electrical Conduct ivity (EC), pH, Total Dissolved Solids (TDS), were recorded in the field and major anions and cations (Ca 2+ , Mg 2+ , K + , Na + , CO3 2- , HCO 3- , Cl - , SO4 2- and NO 3- ) were analyzed in the laboratory. The data of wate r wells were imported into the GIS software and the different water quality maps were produced usin g point data. Then Suitability index of groundwater quality determined by overlaying of water quality m aps. Results: Suitability index values revealed that the ground water in Amin Abad, Abdi, Abd Abad, Nasr Abad and parts of Shams Abad villages of study area had Suitable quality with the suitability in dex range between 75-100 and therefore can be used for irrigation usage. Suitability index of the groundwa ter in Hasnie, Gani Abad and parts of Shams Abad villages were Moderate quality with the range bet ween 35-70 and Abas Abad, Abir Abad and Shaman villages had unsuitable quality and cannot be use d for irrigation purposes. In respect of all evalua ting criteria, villages of study areas that had Suitabl e and Moderate quality could safely be used for long- term irrigation purposes. Conclusion: The present study demonstrated high efficiency for GIS to analyze complex spatial data and groundwater quality suitab ility.

Water quality prediction model utilizing integrated wavelet-ANFIS model with cross-validation

This paper discusses the accuracy performance of training, validation and prediction of monthly water quality parameters utilizing Adaptive Neuro-Fuzzy Inference System (ANFIS). This model was used to analyse the historical data that were generated through continuous monitoring stations of water quality parameters (i.e. the dependent variable) of Johor River in order to imitate their secondary attribute (i.e. the independent variable). Nevertheless, the data arising from the monitoring stations and experiment might be polluted by noise signals owing to systematic and random errors. This noisy data often made the predicted task relatively difficult. Thus, in order to compensate for this augmented noise, the primary objective of this study was to develop a technique that could enhance the accuracy of water quality prediction (WQP). Therefore, this study proposed an augmented wavelet de-noising technique with Neuro-Fuzzy Inference System (WDT-ANFIS) based on the data fusion module for WQP. The efficiency of the modules was examined to predict critical parameters that were affected by the urbanization surrounding the river. The parameters were investigated in terms of the following: the electrical conductivity (COND), the total dissolved solids (TDSs) and turbidity (TURB). The results showed that the optimum level of accuracy was achieved by making the length of cross-validation equal one-fifth of the data records. Moreover, the WDT-ANFIS module outperformed the ANFIS module with significant improvement in predicting accuracy. This result indicated that the proposed approach was basically an attractive alternative, offering a relatively fast algorithm with good theoretical properties to de-noise and predict the water quality parameters. This new technique would be valuable to assist decision-makers in reporting the status of water quality, as well as investigating spatial and temporal changes.

다중벽 탄소나노튜브와 폴리우레탄 복합화 필름의 물성특성

―This study studies on the physical property of MWNT/PU composit e film for electrostatic dissipation (ESD) function by dispersing multi-wall carbon nanotubes (MWNT) in dimethylfor mamide (DMF) and by combining it with polyurethane(PU). For this purpose, four kinds of MWNT were selected and the composit e films were made by dispersion processing, and their physical properties were measured and investigated in terms of electrica l conductivity. For dispersion parameters, four MWNT contents(0 .5, 1, 2, 5wt%) and two dispersion times(30min, 120min) were select ed. The dispersion property and the electrical conductivity of MWNT/PU film was measured using a UV-Vis spectrometer and condu ctivity measuring apparatus. Finally, their physical properties according to the dispersion conditions were analyzed and discus sed with various processing conditions.

Electrical conductivity of zirconia-based solid electrolyte with submicron grain size

The electrical conductivity of the Zr(Y)O2 electro� lyte ceramics with the highest density and the grain size from 90 to 800 nm was studied by impedance spectroscopy. The ceramics was obtained by magnetic pulse compacting of weakly aggregated nanopowders and subsequent sintering. The grain boundary con� ductivity was shown to depend on the grain size. The grain boundary resistance was found to increase with an increase in the grain size in the range of 90- 800 nm. In the grain size range of 1-18 µm, according to the data obtained previously, the grain boundary resistance in the ceramics of this composition mono� tonically decreased with an increase in the grain size. This indicates that a maximum exists in the size dependence of the grainboundary resistance. One of the factors that influence the efficiency of devices with solid oxide electrolytes are the losses due to the voltage drop in the electrolyte. In this connec� tion, the technological problem of decreasing the thickness of the electrolyte layer becomes increasingly urgent. However, in the framework of the ceramic method, the thickness of membranes cannot be decreased without the corresponding decrease in the grain size. This dictates the practical significance of the present work. Attempts to obtain nanosized oxide materials with a facecentered cubic (fcc) lattice of the fluorite type are known in the literature. For ceria� based materials, it was shown (1) that these microand nanosized ceramic samples differ in both the conduc� tivity values and the character of the temperature and oxygen pressure dependences of the conductivity. The models were developed (2, 3) to describe the depen� dences observed by regarding the grain boundaries in the ceramic as a second phase. This concept is obvious for describing heterogeneous materials, for example, a mixture of a cationconducting solid electrolyte and an insulator, as it was done in the classic works of J. Maier (see, for example, (3)), but should be eluci� dated in the general case of homogeneous ceramics. On the other hand, the presence of the Ce 3+ /Ce 4+ redox system complicates the interpretation of the phenomena observed. In this connection, it is of inter� est to study the zirconiabased ceramics. Dense nano� sized Zr(Y)O2 ceramic samples with fcc lattice have not been previously obtained. It turned out to be a very difficult technical task. To succeed, we used magnetic pulse compaction of weakly agglomerated nanopow� ders obtained by laser evaporation. This method allows one to reach pressures up to 15-17 t/cm 2 .

Wear resistance of hot-pressed composites based on reprocessed ШХ15 steel in friction at electrical contacts

When mechanical and electrical energy is intro� duced in a system with normal friction, all the pro� cesses are localized in a thin surface layer, with the for� mation of secondary structures (1). Secondary struc� tures provide protection against deformation and failure, and their properties determine the wear resis� tance of the frictional contact. A lubricantfree wear� resistant slipping electrical contact with a current den� sity above 100 A/cm 2 should be ensured by the forma� tion of secondary structures with high electrical con� ductivity and plasticity and low shear strength. The overall wear resistance of the frictional contact depends on the phase composition, manufacturing method, and structure of the initial materials, as well as the porosity of the composite. Previous studies have shown that sintered compos� ites based on reprocessed ШХ15 steel are promising for wearresistant slipping electrical contacts with a high current density. The porosity of the sintered com� posites is 8-30% (2). A possible method of reducing the porosity is hot pressing. It is expedient to use hot pressing to produce denser materials, with increase in the wear resistance. Another method of increasing the wear resistance of the contact is to introduce alloying elements in the composite's primary structure. We know that introducing nickel in powder steel improves the mechanical characteristics, on account of the action of nickel at the particle boundaries. Nickel also increases the extent of metallic contact and increases the shrinkage and density of the compo� nents. Lead does not form solid solutions or chemical compounds with copper and nickel and its introduc� tion in composites based on ШХ15 steel should increase the plasticity of the secondary structures. Titanium forms carbides and increases the wear resis� tance of powders (3). Therefore, it is of interest to investigate the structure and properties of the fric� tional zone of hotpressed model composites based on reprocessed ШХ15 steel with additions of nickel, lead, and titanium. Steel 45 may be used as the counterbody, analogously to (2). In the present work, we study the structure and per� formance of hotpressed composites based on repro� cessed

The Relative Importance of Road Density and Physical Watershed Features in Determining Coastal Marsh Water Quality in Georgian Bay

We used a GIS-based approach to examine the influence of road density and physical watershed features (watershed size, wetland cover, and bedrock type) on water quality in coastal marshes of Georgian Bay, Ontario. We created a GIS that included landscape information and water-quality data from a 9-year synoptic survey of 105 coastal marshes covering 28 quaternary watersheds. Multiple regressions and partial correlations were used to discern confounding effects of human-induced (road density) versus natural physical watershed determinants of water quality. Road density was the dominant factor influencing many water quality variables, showing positive correlations with specific conductivity (COND), total suspended solids (TSS), and inorganic suspended solids (ISS) and a negative correlation with overall Water Quality Index scores. Road density also showed positive correlations with total nitrate nitrogen (TNN) and total phosphorus (TP). By comparison, larger watershed area was the main factor leading to elevated TP concentrations. The proportion of the watershed occupied by wetlands explained the largest amount of variation in TNN concentrations (negative correlation) and was also negatively correlated with COND and positively correlated with TSS and ISS when we controlled for road density. Bedrock type did not have a significant effect in any of the models. Our findings suggest that road density is currently the overriding factor governing water quality of coastal marshes in Georgian Bay during the summer low-flow period. We recommend that natural variation in physical watershed characteristics be considered when developing water quality standards and management practices for freshwater coastal areas.

Diatom distributions and species optima for phosphorus and current velocity in rivers from ZhuJiang Watershed within a Karst region of south-central China

The relationships between limestone bedrock geology (with extensive Karst topography), water chemistry and the community structure of benthic diatoms were examined for 35 riffle sites using multivariate analysis. The results showed that physical and chemical environmental variables had a notable effect on the biological diversity of benthic diatoms. Eighteen environmental variables were studied, including velocity (current flow), total phosphorus (TP), conductivity (COND), total nitrogen (TN), oxidation-reduction potential (ORP), chemical oxygen demand (COD), water temperature (WT), pH, silicon dioxide (SiO 2 ), turbidity, major ions (Na + , K + , Ca 2+ , Mg 2+ , HCO 3 ― +CO 3 2― , Cl ― , NO ― 3 , SO 4 2― ). Two variables, TP and velocity were found to be the most important factors explaining diatom distributions. With further analysis using weighted average inference models, the results showed good predictive statistics for diatom composition and TP (R 2 = 0.654, RMSE = 0.036; R 2 boot = 0.483; RMSE boot = 0.048) and velocity (R 2 = 0.641, RMSE = 0.378; R 2 boot = 0.416, RMSE boot = 0.500). Indicator diatom species for TP and velocity were identified and assessed using weighted average optima and tolerances. Fifty-seven taxa were identified as biological indicators, which included Fragilaria vaucheriae, Achnanthidium convergens, A. lineare, Kolbesia suchlandtii and Nitzschia frustulum for high TP (> 200 μg l ―1 ) and Reimeria sinuata, Achnanthidium minutissimum var. scoticum, A. exile, Cymbella leptoceris, and Navicula cf. pseudokotschyi for low TP (50―97 μg l ―1 ). These taxa are useful as monitoring tools for eutrophication in ZhuJiang watershed within a Karst region of south-central China. Diatom richness followed a Gaussian distribution with the most taxa observed in waters with moderate levels of TP This distribution supports the intermediate disturbance hypothesis which predicts that species richness and diversity will be highest under moderate environmental conditions. A Gaussian distribution was also observed for species richness under changing current flow. Measures of diatom diversity, richness, and species optima from the south-central highlands of China will be useful as indicator values for future water-quality assessments.

Anomalous thermal conductivity in Nd＿1.67Sr0.33NiO＿4

The temperature dependence of thermal conductivity (K),resistivity (ρ) and low field ac susceptibility (χ) of perovskite nick elates Nd＿2-xSr＿xNiO＿4(x =0.33,1.35) have been measured at temperatures from 77 to 300 K. The thermal conductivity an omalies associated with charge_order (CO) and spin_order (SO) are observed simultaneously in Nd＿1.67Sr0.33NiO＿4 for the firs t time so far as we know. The thermal conductivity is enhanced belowT_CO , but is suppressed near T＿SO. There is also response to CO and S O in the χ-Τ curve. Only CO is observed in the ρ-Τ curve. In contrast, th ere are no anomalies in K-Τ, ρ-Τ andχ-Τ of Nd＿1.67Sr0.33NiO＿4. The anomalous phonon thermal conductivi ty in Nd＿1.67Sr0.33NiO＿4 indicates that there are strong charg e_phonon interaction and the spin_phonon interaction in this compound.

Determining Radiative Heat Transfer Through Heterogeneous Multilayer Nonwoven Materials

A theoretical equation of the combined thermal conductive, convective, and radiative heat flow through heterogeneous multilayer fibrous materials is presented. Samples whose properties are analyzed by this equation were constructed from glass and ceramic webs and used in an earlier work to experimentally determine their thermal conductivities. In that experimental work, overall effective thermal conductivities were determined using a guarded hot plate instrument with temperatures ranging from 430 to 480°C. In the theoretical equation presented here, thermal convective heat flow is ignored because of fabric structural conditions, and the conduction component of the overall conductivity is determined by Fricke's equation. Furthermore, the results of Fricke's equation and the overall effective thermal conductivity are used to estimate the radiative thermal conduc tivity of the samples.

Preparation and characterization of a new perovskite-type oxide ion conductor KN b1-xMgxO3-δ

A series of solid electrolytes KNb1-xMgxO3-δ (x=0.0—0.3) with an orthorhombic perovskite structure was synthesized under high temperature and high pressure（4.0GPa，870℃）. The effect of Mg-doping on the structure transformation and electrical properties was systematically studied in this paper. The Raman spectra at different temperatures and differential thermal analysis results indicate that the structure of the samples transforms from ferroelectric orthorhombic to tetragonal phase, and finally to paraelectric cubic phase with increasing temperature. Weakening of the coupling effect of A-site cation on BO6 octahedra and the B-site cation contribution to spontaneous polarization, as a result of the Mg2+ doping in KNbO3, leads to th e decrease of Curie temperature.The Curie point of KNb0.85Mg0.15 O2.775,decreasing by about 40℃ in comparison with KNbO3 ,is 392℃.Impedance spectroscopic data show that the conductivity of the samples is ionic, the grai n-boundary effect is very significant, and the conductivity of the samples is de termined mainly by the grain-boundary. Mg-doping increases the oxygen ion conduc tivity of the samples. KNb0.9Mg0.1O2.85 has the highest conduc tivity of 1.2×10-3S/cm at 700℃ in all of the samples,which makes it a kind of promising oxygen ionic conduction materials.

The thermal/electronic transport properties of new superconductor MgB2 and MgCNi3

The temperature dependence of thermal conductivity and electronic conductivity in superconductor MgB2, MgCNi3 and Bi2Sr2Ca0.9Ce0.1Cu2O8+y are presented. The thermal conductivity of Bi2Sr2Ca0.9Ce 0.1Cu2O8+y shows a peak under Tc observ ed in cuprates, but those of MgB 2 and MgCNi3 decrease monotonously. We calculate the elec tron thermal condu ctivity and the phonon thermal conductivity by Wiedemann-Franz law. The electron s contribute a large fraction to the thermal conductivity in normal state of MgB 2 and MgCNi3 because of the non-localigation of mutual eff ect of electrons. The analysis on electronic thermal conductivity indicates that the scattering by impurities prevails in electronic thermal resistance of both samples.

Ionic dialysance measurement is urea distribution volume dependent: a new approach to better results.

Conductivity (CD)-based dialysance measurements precisely match urea dialysance with <5% difference. For measurement, a CD step-profile is applied by increasing dialysate inlet CD at time t0 for 10% above baseline and lasting for 2-5 min until t1, followed by a decrease to -4% until t2 and a final return to baseline, meanwhile recording dialysate CD at filter inlet (cdi) and outlet (cdo), dialysate flow (Qd), and ultrafiltration (UF)-rate (Qf). Electrolytic dialysance (KeCn) is calculated by KeCnI,J = (1 -[cdoI-cdoJ]/[cdiI-cdiJ])(Qd+Qf) with time index I not = J. The combinations in I,J are not equivalent: KeCn0,1 < KeCn1,2 < KeCn0,2. Each difference is 2% to 5%, and a difference versus urea clearance remains. An in vivo on-line clearance study (10 patients, 100 dialysis sessions, 265 measurements) with automatic electrolytical dialysance measurements and permanent data recording was conducted. Two methods were applied: a CD step-profile and a significantly smaller, dynamic CD bolus. Both were compared to laboratory reference of urea clearance. Reference Kt/V has been calculated using equilibrated single-pool methods and direct quantification. Urea generation was ignored. The results are as follows. The reference blood-side urea clearance was 164.0 +/- 11.8 ml/min, n = 265. The mean errors of the ionic dialysance results are KeCn0,1: -9.1 +/- 4.8%, n = 250; KeCn1,2: -5.6 +/- 4.4%, n = 250; KeCn0,2: 6.8 +/- 7.7%, n = 250; KeCnBolus: 0.1 +/- 4.8%, n = 162. The KeCnI,J error is urea distribution volume related. Kt/V comparison to equilibrated single pool is as follows: KeCn1,2t/V: 0.0 +/- 5.0% (r = 0.96, n = 45); KeCnBolust/V: 5.3 +/- 3.9% (r = 0.98, n = 44). The comparison to direct quantification is as follows: KeCn1,2t/V: -2 +/- 6.4% (r = 0.95, n = 68); KeCnBolust/V: 3.2 +/- 6.3% (r = 0.95, n = 66). V could roughly be measured. Dialysance measured by the step-function method was dependent on sodium load and distribution volume while the CD-bolus dialysance was not. Errors are generated by measurement-induced sodium shift that is sufficient even to estimate urea distribution volume. For dialysance measurements, small dynamic CD boli are preferable to stable step functions.

Macrobenthic invertebrate richness and composition along a latitudinal gradient of European glacier‐fed streams

1. The influence of 11 environmental variables on benthic macroinvertebrate communities was examined in seven glacier‐fed European streams ranging from Svalbard in the north to the Pyrenees in the south. Between 4 and 11 near‐pristine reaches were studied on each stream in 1996–97.2. Taxonomic richness, measured at the family or subfamily (for Chironomidae) levels for insects and higher levels for non‐insects, increased with latitude from Svalbard (3 taxa) to the Pyrenees (29 taxa).3. A Generalized Additive Model (GAM) incorporating channel stability [Pfankuch Index (PFAN)], tractive force, Froude number (FROU), water conductivity (COND), suspended solids (SUSP) concentration, and maximum temperature explained 79% of the total deviance of the taxonomic richness per reach. Water temperature and the PFAN of stability made the highest contribution to this deviance. In the model, richness response to temperature was positive linear, whereas the response to the PFAN was bell‐shaped with an optimum at an intermediate level of stability.4. Generalized Additive Models calculated for the 16 most frequent taxa explained between 25 (Tipulidae) and 79% (Heptageniidae) of the deviance. In 10 models, more than 50% of the deviance was explained and 11 models had cross‐validation correlation ratios above 0.5. Maximum temperature, the PFAN, SUSP and tractive force (TRAC) were the most frequently incorporated explanatory variables. Season and substrate characteristics were very rarely incorporated.5. Our results highlight the strong deterministic nature of zoobenthic communities in glacier‐fed streams and the prominent role of water temperature and substrate stability in determining longitudinal patterns of macroinvertebrate community structure. The GAMs are proposed as a tool for predicting changes of zoobenthic communities in glacier‐fed streams under climate or hydrological change scenarios.

Separation and detection of common mono- and divalent cations by ion chromatography with an ODS column and conductivity/UV detection

The retention and detection behavior of common mono- and divalent cations (M +, alkali metal (Li +, Na +, K +, Rb +, Cs +) and ammonium ions (NH 4 +); M 2+, alkaline earth metal ions (Mg 2+, Ca 2+, Sr 2+, Ba 2+) was examined using an ODS column (150×4.6 mm I.D.) and conductivity (CD)/UV detection. The results obtained were as follows: (1) for M +, the mobile phase, 0.1 m M sodium dodecyl sulphate (SDS)+10 m M HNO 3 and indirect CD detection were effective. (2) Addition of Ce(III) in the mobile phase accelerated the elution of both M + and M 2+. The separation of above 10 cations on an ODS column was achieved for the first time without any coelution of cations and disturbance by system peak. Addition of higher SDS resulted in good separation of M + and M 2+ with longer retention times. CD detection was possible for M + and M 2+ and UV detection for M 2+. (3) For M 2+, the mobile phase, 0.8 m M Ce(III)+0.1 m M SDS+1 m M HNO 3 and indirect UV detection were effective. The IC methods were applied to real samples.

An evaluation of nitrile gloves as an alternative to natural rubber latex for handling chemotherapeutic agents

Introduction. In 1986 and 1995, the Occupational Safety and Health Administration issued guidelines for the handling of chemotherapeutic agents. Natural rubber latex gloves are recommended for all levels of handling these drugs; these gloves provide both pro tection to the health care worker and a high degree of manual dexterity in performing tasks requiring fine motor skills. However, many health care workers experience allergic reactions to natural rubber latex, with symptoms ranging from minor skin irritation to systemic anaphylaxis; the latter is a serious life-threat ening condition. Therefore, it is extremely important that alternative glove materials be found that offer protection against biological and chemical agents and also afford health care workers ease of use and fit. Methods. In this study, we tested a thin-gauge (0.0045-inch gauge) disposable nitrile glove; this glove, which offers fine motor skill ability to its users, has been tested against a wide range of chemicals but has not yet been tested specifically against chemo therapeutic agents. Using American Society for Test ing and Materials method F739-92, these gloves were tested for permeation resistance at three concentra tions, simulating exposures to Pharmacy, Nursing, and Housekeeping staff. Eleven commonly used che motherapeutic drugs were investigated. Conductivity was used to determine whether drug was present in the test solutions. Result. Drug was not detected in any of the samples collected. When carmustine was tested, the effluent had a distinct alcohol odor, but no conduc tivity was noted. Conclusions. These disposable nitrile gloves appear to be acceptable for preparing the chemother apy agents tested. Hospitals must be open to finding replacements to natural rubber latex products and must alert their staff members about the potential for latex sensitivity in both patients and other staff mem bers. Manufacturers of non-latex gloves should be encouraged to conduct chemotherapy permeability studies on their products.

Finite Element Analysis of Hot Rolled Coil Cooling.

A new unit layer model for the equiva lent t hermal co nductivity of layered steel strips has been proposed. The equivale nt thermal conductivity is a functio n of strip thickness, surface characteristics and compressive stress. The modeled eq ui valent thermal conduct ivity corresponds well to the ex perimental data. Finite element analyses (FE M) fo r cooli ng of hot rol led coil have been carried out under various cooling condi tions using the equivale nt ther mal conduct ivity as the thermal conductivity in radial di rection of hot rol led coi l. A new calculation procedure using ABAQUS has been developed, where th e radi al compress ive ther mal stres s is taken into account for ca lculatio n of the eq ui va lent th ermal conduct i vi tι or th e orthotropic stress dependent ther ma l co nductivity . The calcul ated cool ing curv es using the orthotrop ic stress dependent thermal conductivity have been compared with data calculated usi ng isot ropic and orthotropic stress independent conductiv ity and with experimenta l data. The cooling curves ca lcul ated usi ng eq uivalent thermal conductivity as rad ial thermal conductivi ty are in better ag reement with ex per imental data.

Conductivity Measurement—A Simple Method for Determining Dye / Surfactant Interaction

Surfactants present in the dyebath are responsible for a considerable change in the state of dye in solution, predominately caused by interactions between dye and sur factant. Among several known methods for investigating these interactions, the con ductivity measurement is a simple and accessible method for determining the degree of interaction between direct or acid dye and nonylphenolethoxylates. In order to explain the results conveniently, a fraction named the conductance ratio is defined and used as a measure of the degree of dye /surfactant interaction. The kind of surfactant does indeed exert significant influence on the degree of interaction.