bluuebunny/crossref_metadata_2025 huggingface dataset:
Recruitment dynamics of walleyes (Stizostedion vitreum) in Kansas reservoirs: generalities with natural systems and effects of a centrarchid predator
Authors: Quist Michael C , Guy Christopher S , Stephen James L
Published: September 2003

Knowledge of factors influencing recruitment dynamics of walleyes (Stizostedion vitreum) in different systems and regions is important for developing a better understanding of walleye ecology. Therefore, we investigated associations among walleye recruitment and climatic, water-level, and biotic characteristics in four Kansas reservoirs during 19851999. Walleye recruitment was positively related to spring storage ratios and temperatures and negatively associated with spring water levels and abundance of 130- to 199-mm white crappies (Pomoxis annularis). The influence of juvenile white crappie predation on larval walleyes was examined by conducting a manipulative experiment. Regardless of zooplankton density or water clarity, mortality of larval walleyes resulting from white crappie predation was over 90%. Based on our empirical and experimental results, we propose a bioticabiotic confining hypothesis (BACH) to explain abiotic and biotic effects on walleye recruitment dynamics. Specifically, high variability in walleye recruitment was observed during years with low densities of 130- to 199-mm white crappies and likely resulted from the effects of abiotic factors. When white crappie abundance was high, walleye recruitment was low and exhibited little variability, suggesting that white crappies can have an overriding influence on walleye recruitment regardless of abiotic conditions.
Spatial dynamics of large-scale, multistage crab (Callinectes sapidus) dispersal: determinants and consequences for recruitment
Authors: Etherington Lisa L , Eggleston David B
Published: September 2003

We assessed determinants and consequences of multistage dispersal on spatial recruitment of the blue crab, Callinectes sapidus, within the Croatan, Albemarle, Pamlico Estuarine System (CAPES), North Carolina, U.S.A. Large-scale sampling of early juvenile crabs over 4 years indicated that spatial abundance patterns were size-dependent and resulted from primary post-larval dispersal (pre-settlement) and secondary juvenile dispersal (early post-settlement). In general, primary dispersal led to high abundances within more seaward habitats, whereas secondary dispersal (which was relatively consistent) expanded the distribution of juveniles, potentially increasing the estuarine nursery capacity. There were strong relationships between juvenile crab density and specific wind characteristics; however, these patterns were spatially explicit. Various physical processes (e.g., seasonal wind events, timing and magnitude of tropical cyclones) interacted to influence dispersal during multiple stages and determined crab recruitment patterns. Our results suggest that the nursery value of different habitats is highly dependent on the dispersal potential (primary and secondary dispersal) to and from these areas, which is largely determined by the relative position of habitats within the estuarine landscape.
Temporal variation in synchrony among chinook salmon (Oncorhynchus tshawytscha) redd counts from a wilderness area in central Idaho
Authors: Isaak Daniel J , Thurow Russell F , Rieman Bruce E , Dunham Jason B
Published: September 2003

Metapopulation dynamics have emerged as a key consideration in conservation planning for salmonid fishes. Implicit to many models of spatially structured populations is a degree of synchrony, or correlation, among populations. We used a spatially and temporally extensive database of chinook salmon (Oncorhynchus tshawytscha) redd counts from a wilderness area in central Idaho to examine patterns in synchrony as these fish underwent a sixfold decrease in abundance. Our results suggested that populations became strongly synchronous as abundances decreased and that the range, or diversity of correlations, exhibited among populations also decreased. These changes indicate that the likelihood of simultaneous extirpations has increased, which could have long-term detrimental consequences for metapopulation persistence. Implications for management are that the resilience of many metapopulations to large-scale disturbance and anthropogenic suppression may not depend solely on attempts to maintain large and productive component populations, but also on efforts to desynchronize populations that have become strongly correlated. Such efforts could entail promoting the existence of a broad distribution and diversity of habitats that support a wide array of life-history forms and ensuring that some habitats are sufficiently spatially disjunct so that risks from catastrophic stochastic events are minimized.
Design for forces induced by seismic torsion
Authors: Humar JagMohan , Yavari Soheil , Saatcioglu Murat
Published: September 2003

Eccentricities between the centres of rigidity and centres of mass in a building cause torsional motion during an earthquake. Seismic torsion leads to increased displacement at the extremes of the building and may cause distress in the lateral load-resisting elements located at the edges, particularly in buildings that are torsionally flexible. For an equivalent static load method of design against torsion, the 1995 National Building Code of Canada specifies values of the eccentricity of points through which the inertia forces of an earthquake should be applied. In general, the code requirements are quite conservative. They do not place any restriction on the torsional flexibility, however. New proposals for 2005 edition of the code which simplify the design eccentricity expressions and remove some of the unnecessary conservatism are described. The new proposals will require that a dynamic analysis method of design be used when the torsional flexibility of the building is large. Results of analytical studies, which show that the new proposals would lead to satisfactory design, are presented.Key words: torsional response to earthquake, natural torsion, accidental torsion, design for torsion, National Building Code of Canada, interdependence of strength and stiffness.
Development of seismic hazard maps for the proposed 2005 edition of the National Building Code of Canada
Authors: Adams John , Atkinson Gail
Published: September 2003

A new seismic hazard model, the fourth national model for Canada, has been devised by the Geological Survey of Canada to update Canada's current (1985) seismic hazard maps. The model incorporates new knowledge from recent earthquakes (both Canadian and foreign), new strong ground motion relations to describe how shaking varies with magnitude and distance, the newly recognized hazard from Cascadia subduction earthquakes, and a more systematic approach to reference site conditions. Other new innovations are hazard computation at the 2% in 50 year probability level, the use of the median ground motions, the presentation of results as uniform hazard spectra, and the explicit incorporation of uncertainty via a logic-tree approach. These new results provide a more reliable basis for characterizing seismic hazard across Canada and have been approved by the Canadian National Committee on Earthquake Engineering (CANCEE) as the basis of the seismic loads in the proposed 2005 edition of the National Building Code of Canada.Key words: seismic hazard, earthquake, probability, uniform hazard spectrum, maps, Cascadia subduction, strong ground motions, uncertainty, CANCEE, National Building Code of Canada.
Load factor calibration for the proposed 2005 edition of the National Building Code of Canada: Statistics of loads and load effects
Authors: Bartlett F M , Hong H P , Zhou W
Published: September 2003

The 2005 edition of the National Building Code of Canada (NBCC) will adopt a companion-action format for load combinations and specify wind and snow loads based on their 50 year return period values. This paper summarizes statistics for dead load, live load due to use and occupancy, snow load, and wind load that have been adopted for calibration, and a companion paper presents the calibration itself. A new survey of typical construction tolerances indicates that statistics for dead load widely adopted for building code calibration are adequate unless the dead load is dominated by thin, cast-in-place concrete toppings. Unique statistics for live load due to use and occupancy are derived that pertain specifically to the live load reduction factor equation used in the NBCC. Statistics for snow and wind loads are normalized using the 50 year values that will be specified in the 2005 NBCC. New statistics are determined for the factors that transform wind speeds and ground snow depths into wind and snow loads on structures.Key words: buildings, code calibration, companion action, dead loads, live loads, load combinations, load factors, reliability, safety, snow loads, wind loads.
Regular papers / Articles ordinaires A numerical approach for the static analysis of the body of pressurized dry gas holders
Authors: You L H , Zhang J J , Wu H B , Sun R B
Published: September 2003

In this paper, a numerical method is developed to calculate deformations and stresses of the body of dry gas holders under gas pressure. The deformations of the wall plates are decomposed into out-of-plane bending and in-plane deformation. The out-of-plane bending of the wall plates is described by the theory of orthotropic plates and the in-plane deformation by the biharmonic equation of flat plates under plane stress. The theories of beam columns and beams are employed to analyze the columns and corridors, respectively. By considering compatibility conditions between the members and boundary conditions, equations for the determination of deformations and stresses of dry gas holders under gas pressure are obtained. Both the proposed approach and the finite element method are used to investigate the deformations and stresses of the body of a dry gas holder under gas pressure. The results from the proposed method agree with those from the finite element method. Because far fewer unknowns are involved, the proposed method is computationally more efficient than both the finite element method and the series method developed from the theory of stiffened plates.Key words: numerical approach, body of dry gas holders, gas pressure.
Dynamic analysis of buildings for earthquake-resistant design
Authors: Saatcioglu Murat , Humar JagMohan
Published: September 2003

The proposed 2005 edition of the National Building Code of Canada specifies dynamic analysis as the preferred method for computing seismic design forces and deflections, while maintaining the equivalent static force method for areas of low seismicity and for buildings with certain height limitations. Dynamic analysis procedures are categorized as either linear (elastic) dynamic analysis, consisting of the elastic modal response spectrum method or the numerical integration linear time history method, or nonlinear (inelastic) response history analysis. While both linear and nonlinear analyses require careful analytical modelling, the latter requires additional considerations for proper simulation of hysteretic response and necessitates a special study that involves detailed review of design and supporting analyses by an independent team of engineers. The paper provides an overview of dynamic analysis procedures for use in seismic design, with discussions on mathematical modelling of structures, structural elements, and hysteretic response. A discussion of the determination of structural period to be used in association with the equivalent static force method is presented.Key words: dynamic analysis, earthquake engineering, elastic analysis, fundamental period, hysteretic modelling, inelastic analysis, National Building Code of Canada, seismic design, structural analysis, structural design.
Knowledge-based risk identification in infrastructure projects
Authors: Zoysa Sanjaya De , Russell Alan D
Published: September 2003

Effective risk management is a central function in the successful planning and execution of large infrastructure projects. This paper explores how current knowledge-based approaches for risk management can be improved upon so that they are more responsive to the attributes of a project and the needs of system users. A review of existing knowledge-based systems for risk management provides a backdrop for a discussion on desirable characteristics of such an approach. The proposed methodology adopts a model-based technique in that explicit abstractions of project components and processes, and the physical, regulatory, political, social, financial, economic, contractual, and organizational environments in which they are located, are created to assist in the reasoning about possible risks. This contrasts with several current systems that use only implicit representations. The reasoning schema and models of the physical project and environment that are used for the reasoning process are described in the paper.Key words: risk identification, project modeling, knowledge management, infrastructure projects.
Supercritical flow over a rectangular side weir
Authors: Ghodsian Masoud
Published: September 2003

Side weirs are flow-diversion devices widely used in irrigation, land drainage, and urban sewage systems. Hydraulic characteristics of a sharp-crested rectangular side weir under supercritical flow have been studied in this paper. The concept of elementary discharge coefficient for supercritical flow is introduced. The elementary discharge coefficient has been related to head weir height ratio and local Froude number. Suitable equations for the elementary discharge coefficient are introduced.Key words: supercritical flow, sharp crested, rectangular side weir, elementary discharge coefficient.
Bétons à haute performance à base de ciments composés contenant du laitier et de la fumée de silice
Authors: Saric-Coric Mladenka , Aïtcin Pierre-Claude
Published: September 2003

For each tonne of cement used, the cement industry emits an average of 0.9 t of CO2, which contributes to the greenhouse effect. To satisfy the demands of the concrete industry for cementing materials, new environmental requirements, and the implementation of a sustainable development policy, the use of supplementary cementitious material as a replacement of part of the Portland cement has proven to be an interesting avenue that has not yet been fully explored. Granulated blast-furnace slag has been and is being used as a supplementary cementitious material in replacement of cement in many countries. In Canada, its proportion is usually limited to 20-25% of cement replacement owing to a significant decrease in early age compressive strength as well as a lower scaling resistance. In this study, we have tried to show that by reducing the water:cement ratio we can increase cement replacement by slag up to 50% without harming its short-term compressive strength and scaling resistance. The concretes that were prepared had a workability comparable to that of the reference concrete without slag, sufficient compressive strength to allow demoulding after 24 h, very low chloride ion permeability even at 28 d, as well as very good freeze-thaw and scaling resistance, as long as it is water-cured for a slightly longer period.Key words: high-performance concrete, blast-furnace slag, sustainable development, superplasticizers, workability, durability, silica fume.
Constraint-based genetic algorithm for earthmoving fleet selection
Authors: Marzouk Mohamed , Moselhi Osama
Published: September 2003

This paper presents a constraint-based genetic algorithm dedicated to optimizing earthmoving operations. The algorithm aims to minimize the total cost of earthmoving operations, accounting for efficient use of the selected equipment fleet. Total cost, duration, and utilization of the equipment fleets involved are estimated via computer simulation and passed to the developed algorithm to optimize fleet selection. Users specify the lower limits of equipment utilization as constraints that guide the algorithm search. The developed algorithm has powerful features: (i) it runs in canonical and genitor forms and (ii) it allows normalization of fitness values of chromosomes using three methods, namely inversion, linear ranking, and nonlinear ranking normalization. The algorithm supports roulette wheel and tournament methods for random selection of chromosomes. Crossover can be applied in a discrete or arithmetic form. In addition, the algorithm performs its computations in an efficient manner by elite best-fit chromosome in all generations and by storing chromosome information in its database. The proposed algorithm is explained in the context of a numerical example to clarify its useful features.Key words: earthmoving, equipment selection, optimization, genetic algorithms, computer simulation.
Erosion of undisturbed clay samples from the banks of the St. Lawrence River
Authors: Gaskin S J , Pieterse J , Shafie A Al , Lepage S
Published: September 2003

In some regions the clay banks of the St. Lawrence River along the Montréal to Lac St. Pierre reach have recession rates of up to 13 m/year. The banks are formed of structured marine clays of the Champlain Sea (Leda clay). In this laboratory study, undisturbed samples of this high-plasticity inorganic clay taken at Îles de Verchères were subjected to a unidirectional current and a constant wave climate to investigate the mechanisms of erosion and the factors influencing erosion rates. Initially, surface erosion resulted in the formation and enlargement of cracks and the smoothing of competent surfaces. The dominant erosion process was a mass erosion of the blocks of clay delineated by the cracks. Desiccation or weathering significantly increased erosion rates, as tension cracks formed due to drying, and upon rewetting, the formation of microfissures resulted in disintegration into small, easily erodable flakes. The estimated critical shear stress of the samples was 620 Pa. For the St. Lawrence River, these results suggest that waves are the dominant erosion mechanism, with shipping contributing significantly to the erosion of banks close to the navigation channel. Weathering caused by wetting and drying from changing water levels or wave runup greatly increases erosion rates.Key words: erosion, Leda clay, undisturbed clay, natural clay structure, St. Lawrence River, waves, weathering, desiccation, vegetation.
A three-dimensional model for bolted connections in wood
Authors: Moses D M , Prion H G.L
Published: September 2003

Recent criticism of the bolted connection requirements in the Canadian wood design code CSA Standard O86 indicates that the code lacks consideration of the different modes of failure, particularly as they relate to multiple-bolt connections. A finite element model is proposed to predict loaddisplacement behaviour, stress distributions, ultimate strength, and mode of failure in single- and multiple-bolt connections. The three-dimensional (3-D) model uses anisotropic plasticity for the wood member and elastoplasticity for the bolt. The Weibull weakest link theory is used to predict failure at given levels of probability. Predictions for connection behaviour in Douglas-fir and laminated strand lumber (LSL) correspond to experimentally observed behaviour. The output from the 3-D model is used for a multiple-bolt connection spring model to illustrate many of the phenomena described in the literature.Key words: bolt, Douglas-fir, connection, model, plasticity, weakest link, wood.
Shear and fatigue strength of grout-type transverse joints
Authors: Kim Yoon-Chil , Shin Soobong , Park Jong-Jin
Published: September 2003

Grout-type transverse joints between precast concrete slabs were tested to study their static and fatigue behaviours. The tests were performed with loading equipment especially designed and constructed in the laboratory to introduce shear force on the joints of the test specimens. The aim of this study was to improve the shear and fatigue strength of grout-type transverse joints by identifying the effects of prestressing the specimens. The results indicated that longitudinal prestressing was an effective method to increase both the shear and fatigue strengths of grout-type transverse joints. Rational methods to estimate the cracking and ultimate loads for grout-type transverse joints are proposed based on the static loading tests. An estimation of the fatigue strength with respect to the amount of prestress is also suggested to aid in design of the grout-type transverse joint.Key words: grout-type transverse joints, precast concrete slabs, shear and fatigue strength, prestressing.
A general relationship between porosity and uniaxial strength of engineering materials
Authors: Li Li , Aubertin Michel
Published: September 2003

The mechanical behavior of engineering materials, whether of natural or artificial origin, varies with their internal structure. As the uniaxial strength σuis commonly used to characterize basic responses to external loading, it is of value to evaluate the effect of porosity n on the magnitude of σu. The authors first review some existing relationships developed and applied to quantify the influence of n on uniaxial strength, in compression (σc) and in tension (σt). A new general formulation, applicable to various materials over a wide range of porosities, is then proposed. Using experimental data from different sources, the validity of this new relationship is demonstrated and briefly discussed.Key words: uniaxial strength, compression, tension, porosity, porous media, experimental results, soil, rock, concrete.
Improving the flood control at a lower cost for a future Hydro-Québec hydroelectric facility on the Toulnustouc River, Canada
Authors: Gaudette M , Bulota G
Published: September 2003

Prior to the construction of a new hydroelectric facility on the Toulnustouc River, Quebec, Canada, optimization was carried out on the dams and spillway design, resulting in a CAN$6 million reduction in the total project cost while improving flood control. This result was obtained using a new approach to the design of civil works, in which the dam and spillway were in complete interaction with one another. In this approach, the possibility of increasing the freeboard of the dams more than that usually required by Hydro-Québec criteria was allowed. The additional freeboard or reservoir volume is strictly assigned to flood control to reduce the maximum released discharge to existing downstream facilities. The raising of dam crests generates additional cost that is more than compensated for by a reduction in spillway capacity and cost.Key words: flood, control, cost, spillway, dam, optimization, security, freeboard.
Carbon fibre reinforced polymer wrapping for the rehabilitation of masonry columns
Authors: Masia Mark J , Shrive Nigel G
Published: September 2003

The use of carbon fibre reinforced polymer (CFRP) wrapping to strengthen existing cracked masonry columns was investigated experimentally. The study was aimed at quantifying the increase in strength that can be achieved and assessing the effect of column size on the strength increase. Eighteen columns were tested, with three different square cross-sectional sizes (290 mm × 290 mm, 390 mm × 390 mm, 490 mm × 490 mm) and two different types of clay masonry unit. Six columns were constructed in each size, two columns using unit type 1 and four columns using unit type 2. Strengthening was achieved by wrapping the square section columns directly with a single-layer CFRP laminate or by wrapping the columns after first casting a circular concrete jacket around the column. The latter treatment was applied to two of the small-sized columns and two of the intermediate-sized columns. All other square section columns were wrapped directly. Significant strength increases were achieved, particularly when the columns were provided with the cylindrical concrete jacket. These preliminary tests indicate that the use of CFRP wrapping is an effective technique for rehabilitating damaged masonry columns. Decisive conclusions could not be made regarding the effect of column size (cross-sectional area) on the strength increase achieved. Further tests together with nonlinear finite element modelling aimed at duplicating the experimental observations would greatly enhance the information provided by the current tests.Key words: masonry, columns, rehabilitation, strengthening, fibre reinforced polymer, experimental.
Prévision par modélisation numérique de la zone de risque bordant un tronçon de rivière subissant une crue exceptionnelle
Authors: Mahdi T , Marche C
Published: September 2003

The direct impacts of floods are often considered as limited to the maximum downstream area exposed to the flooding. Considering the size of exceptional floods, the river bed could undergo deep changes. Pairing the GSTARS sediment transport model to a slope stability model (modified Bishop method) that we developed, this paper presents a methodology leading to the definition of a true safety zone along the shores as it takes into account the risk of floods and soil movements: each section of this river undergoes changes due to sediment-fluvial hydraulics ( erosion-deposit) and then eventual landslides modify the profiles. To analyze this, we had first to determine the hydraulic and geotechnical characteristics then use them to test the slope stability of the various legs of the watercourse before and during flooding. The application of this method to a tributary of the Saguenay River for the 1996 "downpour" shows a very good correlation of results with those collected in situ. The method can be directly applied to define the anticipated evacuation zone in case of dam failure.Key words: flooding, evacuation zone, numerical simulations, slope stability, transportation of solids.[Journal Translation]
Sulphate resistance of silica fume blended mortars exposed to various sulphate solutions
Authors: Moon Han-Young , Lee Seung-Tae , Kim Seong-Soo
Published: September 2003

The different performances of silica fume blended mortars placed in various sulphate-bearing exposure conditions were investigated. Experimental study was carried out on mortars immersed in 5% sodium sulphate, 5% magnesium sulphate, and mixed 5% sodium sulphate and 5% magnesium sulphate solutions for 270 d of sulphate exposure. Another variable was the replacement ratio of cement with silica fume (0, 5, 10, and 15% of the cement by weight). The results showed conclusively that silica fume should be given serious consideration for use in sulphate environments. In other words, in a sodium sulphate solution, silica fume showed a beneficial effect on mitigating compressive strength reduction and length change of mortars. However, the strength deterioration factor of the mortar specimen with some silica fume content (especially 15% of the cement by weight) was greater than that of the mortar specimen without silica fume under Mg2+ ion oriented attack. These different sulphate deterioration mechanisms are presented in the study. Microstructural investigations such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDXA), and mercury intrusion porosimetry (MIP) were also used to support the explanation for these mechanisms.Key words: sodium sulphate, magnesium sulphate, silica fume, strength deterioration factor, length change.
Behaviour of square hollow structural steel braces with end connections under reversed cyclic axial loading
Authors: Shaback Brad , Brown Tom
Published: September 2003

The hysteretic behaviour of nine square hollow structural steel (HSS) sections with gusset plate end con nections subject to inelastic cyclic loading has been examined by an experimental investigation. Brace slenderness ratio, width to thickness ratio, and to a lesser extent, the end connection were identified as the key parameters in the tests. It was shown that the effective slenderness ratio is the most important parameter governing the hysteretic behaviour. The out-of-plane deflection of the brace can be accurately calculated using a simplified geometrical model or a model calibrated against the test results. Reduced compressive capacity as specified by the current Canadian Standards Asso ciation (CSA) standard was nonconservative for the specific loading sequence employed in this series of tests. Quantification of the energy dissipation proved that the gusset plates account for a small percentage of the total energy dissipated. The experimental fracture life of the specimens proved to be most affected by the width to thickness ratio and the effective slenderness ratio. An empirical equation is proposed to more accurately determine the theoretical fracture life of an HSS brace.Key words: brace, hysteresis, steel, hollow structural section, cyclic, end connection, fracture, energy dissipation, compressive capacity, effective slenderness ratio.
Influence de la pouzzolane de Beni-saf sur les caractéristiques mécaniques des bétons
Authors: Belaribi N Belas , Semcha M , Laoufi L
Published: September 2003

Builders in our country are not familiar with the practice of using mineral additives, as cement substitutes, in cast-in-place and in ready-mix concretes. It thus seemed important to study and evaluate the impact of these additives, as cement substitutes, on the properties of set concrete. The mineral additive used is natural pozzolan found in large quantities in Western Algeria (Béni-Saf); however, it must be beneficiated. To do so, we designed three pozzolan-based concretes (20, 25, and 30%). We measured compressive strengths at various times and produced a reference control concrete for comparison purposes.Key words: pozzolan, dosage, concrete, composition, substitution, compressive strength.[Journal translation]
Modélisation non paramétrique de la relation entre les caractéristiques du vent et la différence de niveaux sur un grand réservoir
Authors: Haché Mario , Durocher Marc , Bobée Bernard
Published: September 2003

The natural inflow at a site is a key variable for optimal management of water resources, particularly for hydroelectric production. For sites with dams and hydroelectric powerplants, this variable cannot be measured directly, and the water balance equation is used to determine the quantity of water a site receives on its surface during a certain period of time. However, several errors affect the natural inflows computed this way. One of the principal sources of uncertainty for large reservoirs is the nonrepresentativeness of water level because of the wind effect. To quantify the effect of wind on the reservoir surface, a nonparametric regression model was used to relate the water level differences between several stations located on the same reservoir and the characteristics of the wind (direction and intensity). The study showed that the nonparametric regression model substantially improves the knowledge of the water level differences between several stations when there is presence of wind. With this model, it is possible to characterize the types of wind affecting the reservoir and to establish validation strategies for the data. The studied reservoirs are Outardes-4 and Gouin, two large reservoirs located in the north of the province of Québec, Canada.Key words: wind, reservoir, water level, nonparametric regression, natural inflow, performance criteria.
Preliminary investigation of the vacuum pyrolysis of bituminous roofing waste materials
Authors: Chaala A , Roy C
Published: September 2003

The treatment of bituminous roofing waste materials by vacuum pyrolysis was tested in a pilot plant. The pyrolysis experiment was carried out batchwise at a temperature of 500°C and a total maximum pressure of 16 kPa. The amount of feedstock tested was 37 kg. Pyrolysis product yields were 52.3 wt.% oils, 31.2 wt.% solids, 14.4 wt.% pyrolysis gas, and 0.4 wt.% water. Losses were 1.7 wt.%. The pyrolysis oils have a gross calorific value of 42.7 MJ/kg and can be used as a heating fuel. The oil as a whole also represents a valuable material for petrochemical applications. The gas is rich in hydrocarbons and can be used as a make-up heat source (45.2 MJ/kg) for the thermal decomposition process. The solid residues exhibit a moderate calorific value of 17.5 MJ/kg and might find their way as a solid fuel in cement kilns. The nature of the minerals present in the solid residues, which amount to 49.7 wt.%, seems to be compatible with the cement composition. The vacuum pyrolysis technology is viewed as a potential solution to landfill and incineration of this waste construction material. Key words: construction, waste, shingles, bituminous, roofing, pyrolysis, fuels, environment, petrochemicals.
Development of a high performance liquid chromatography method to monitor the biodegradation of naphthenic acids
Authors: Clemente J S , Yen T -W , Fedorak P M
Published: September 2003

Naphthenic acids are found in wastewaters from petroleum refineries and from the extraction process used to recover bitumen from large oil sands deposits found in northeastern Alberta, Canada. The naphthenic acids, comprised mainly of a complex mixture of carboxylic acids, are toxic to many forms of aquatic life. Previous studies have shown that biodegradation in natural settings or in laboratory cultures reduces the toxicity of naphthenic acids. A high performance liquid chromatography (HPLC) method was developed to follow the removal of naphthenic acids from aerobic, laboratory cultures. Small samples of the culture supernatants (100 μμL) were derivatized with 2-nitrophenylhydrazine, and the derivatized carboxylic acids were separated from the excess derivatizing agent by HPLC. The derivatized acids eluted as an unresolved hump in the chromatogram. Comparing the areas under the humps in standard preparations (containing 5200 mg naphthenic acids/L), and in culture supernatants allowed measurements of the depletion of naphthenic acids from the microbial cultures. Three naphthenic acids preparations were studied, and up to 40% of the naphthenic acids were removed by cultures during 30- to 40-d incubation periods. Carbon dioxide formation accompanied the decrease in the naphthenic acids concentration determined by HPLC. Key words: biodegradation, high performance liquid chromatography, naphthenic acids, 2-nitrophenylhydrazine, oil sands.
Advanced leachate treatment at Buckden landfill, Huntingdon, U.K.
Authors: Robinson Howard , Carville Martin , Walsh Tim
Published: September 2003

During April 1994, Aspinwall and Company was appointed to design and commission a treatment plant to treat leachate from the Buckden South Landfill Site, located about 1 km SW of Huntingdon in Cambridgeshire, U.K. The landfill is located in the flood plain of the River Great Ouse, which flows within 400 m of the site. Leachate characterization and flow studies took place during early 1994, after an extensive fin drain collection and interception system had been installed. Aspinwall then undertook leachate treatment trials, as part of the detailed design of the on-site treatment plant that needed to be capable of treating 200 m3/d of leachate to very high standards. The treatment trials were carried out to investigate and design an aerobic biological process that would provide primary treatment, before secondary effluent polishing stages that would involve reed beds and ozonation. The latter specialized stage was intended to provide treatment of a range of pesticides, including the herbicides mecoprop and isoproturon, which were found in leachate and might not be removed fully by biological treatment stages. The leachate also contained contaminants typical of methanogenic conditions, including ammoniacal-N at values in excess of 400 mg/L, with a required effluent discharge consent standard of 10 mg/L. Key words: leachate, mecoprop, isoproturon, biological treatment, ozonation, reed bed, toxicity-based consent.
Improved sludge dewatering by addition of electro-osmosis to belt filter press
Authors: Hwang S , Min K -S
Published: September 2003

Gravity-thickened sludge (GTS) and anaerobically-digested sludge (ADS) from a wastewater treatment plant and sludge from drying bed (DBS) from a water treatment plant were dewatered using the pilot-scale electro-osmotic belt filter press (EBFP). The results indicated that the addition of electro-osmosis greatly improved sludge dewaterability, lowering water content (WC) and heavy metal concentration, and increasing heating value. For instance, EBFP produced 56.0% WC for GTS, 58.4% for ADS, and 69.6% for DBS when current density was 41.1, 42.1, and 17.9 A/m2, respectively, and a cationic coagulant was dosed at 0.36% on dried solid, 0.46%, and 0.19%, respectively. Without the addition of electricity, the system achieved only 74.3% WC for GTS, 72.8% for ADS, and 74.7% for DBS. Therefore, EBFP would produce a proper cake WC by simply controlling the current density, depending on the destination of dewatered cake such as land application, compost, or incineration. Key words: belt filter press, cake, electro-osmosis, heating value, heavy metal concentration, water content.
Dispersion of discharged ship ballast water in Vancouver Harbour, Juan De Fuca Strait, and offshore of the Washington Coast
Authors: Larson Max R , Foreman Michael G.G , Levings Colin D , Tarbotton Michael R
Published: September 2003

The dispersion of harmful nonindigenous biological organisms that may be present in discharged ship ballast water is an issue of international interest. The present paper examines this issue as it applies to Vancouver Harbour and Juan de Fuca Strait, British Columbia, and the adjacent U.S. waters. The objective is to determine whether potential mechanisms exist to transport viable organisms that might be present in discharged ballast water to favourable reproductive habitats within British Columbian coastal waters. The study applied three-dimensional harmonic finite element models to generate representative tidal, atmospheric, and density-driven flow fields. Particle-tracking techniques were used to simulate representative trajectories of passive and active ballast water organisms discharged at existing deballasting sites. It was determined that the safest deballasting sites are off the west coast. Under normal conditions, organisms move southward (summer) or northward (winter) in the Shelf Break Current and only under strong eastward or northward winds are they transported to the Washington or Vancouver Island shorelines. Key words: ship ballast water, discharge, microorganism, trajectory, Vancouver Harbour, West Coast.
Pilot-scale operation of thermophilic aerobic digestion for volatile fatty acid production and distribution
Authors: Li Jowitt Z , Mavinic Donald S , Kelly Harlan G
Published: September 2003

Thermophilic aerobic sludge digestion is operated at elevated temperatures, to achieve sludge stabilization, volatile solids (VS) destruction, and pasteurization. The thermophilic aerobic digestion (TAD) of sludge, under a "microaerated" condition, whereby the system oxygen demand exceeds the supply, has been found to accumulate high concentrations of volatile fatty acids (VFAs), namely acetate and propionate. This VFA-rich TAD supernatant is a potential carbon alternative for phosphorus and nitrogen removal enhancement in biological nutrient removal (BNR) processes. This pilot-scale continuous TAD operation was designed to produce VFA-rich supernatant, without sacrificing sludge solids destruction efficiency. A molecular weight cut-off (MWCO) method was used to analyze the carbonaceous and nutrient distributions in the TAD supernatant. Results suggested that real-time aeration control is necessary to control the micro-aeration operation and optimize the VFA production. The oxidation-reduction potential (ORP) did not correlate well to the actual VFA concentration; however, the ORP monitoring did reflect the status of the micro-aeration condition and the existence of VFAs in the system. The average VFA concentration was found to be in proportion to the sludge concentration in the feed. Also, a certain portion of VFAs was found to associate with particulates and colloids in the TAD supernatant. Key words: digested sludge supernatant, molecular weight cut-off, microaerated, thermophilic aerobic digestion, volatile fatty acids, volatile solids destruction, ultrafiltration.
Release of arsenic and molybdenum by reductive dissolution of iron oxides in a soil with enriched levels of native arsenic
Authors: Bennett Brooke , Dudas Marvin J
Published: September 2003

This study examined the release of arsenic (As), molybdenum (Mo), and iron (Fe) into the aqueous phase during reductive dissolution of iron oxides in an amended acid sulfate soil naturally enriched in arsenic. These acid sulfate soils occur worldwide and have a significant distribution in parts of Alberta and British Columbia. Reactions were studied in incubation vessels under controlled laboratory conditions. Soils were driven anaerobic by stimulation of indigenous bacteria using a glucose addition and then periodically analyzed for redox potential (Eh), pH, electrical conductivity, and aqueous concentrations of Fe, As, Mo, and other chemical species. Dissolution of iron oxides was pronounced when Eh values dropped to below +100 mV. With dissolution, concentrations of Fe, As, and Mo increased in the solution phase. Aqueous As concentrations increased from 0.87 to 119 μμg L1 during a reduction period of 48 d. Molybdate (MoO42), an oxyanion similar to arsenate, also closely followed the release of Fe and As into solution during the incubation. The results indicate both As and Mo behave similarly in response to the dissolution of soil iron oxides under reducing conditions and that their aqueous phase concentrations are largely controlled by dissolution and desorption from the iron oxide host. Key words: acid sulfate soil, arsenic, molybdenum, iron, redox potential, desorption.
Expression and export of aRuminococcus albuscellulase inButyrivibrio fibrisolvensthrough the use of an alternative gene promoter and signal sequence
Authors: Kobayashi Yasuo , Taguchi Hidenori , Goto Takashi N , Koike Satoshi , Ohmiya Kunio
Published: September 2003

Ruminococcal cellulase (Ruminococcus albus F-40 endoglucanase EgI) was successfully expressed in Butyrivibrio fibrisolvens OB156C, using the erm promoter from pAMβ1. A newly identified signal peptide coding region of xynA from B. fibrisolvens 49 allowed efficient translocation of the foreign EgI into the extracellular fraction. First, B. fibrisolvens xynA with or without its own putative signal peptide (XynA SP) coding region was cloned into a shuttle vector to transform B. fibrisolvens OB156C. Both plasmids caused a 2- to 2.4-fold increase in xylanase activity. The transformant expressing XynA with the signal peptide showed a significantly higher proportion of activity in the extracellular fraction than the transformant with XynA lacking the signal peptide (75% vs. 19%), demonstrating the significance of XynA SP in the translocation of the expressed enzyme. Second, using the XynA SP coding region, secretion of EgI was attempted in B. fibrisolvens. Since the signal peptide of R. albus EgI did not function in B. fibrisolvens, it was replaced with the XynA SP. A high activity variant of EgI containing the XynA SP was transcribed using the erm promoter, resulting in a 27-fold increase in endoglucanase activity, most of which (>93%) was in the extracellular fraction of the B. fibrisolvens transformant. EgI without the XynA SP was scarcely detected in the extracellular fraction (<10%).Key words: Butyrivibrio fibrisolvens, Ruminococcus albus, cellulase, gene promoter, signal peptide.
Survival and colonization of rhizobacteria in a tomato transplant system
Authors: Yan Zhinong , Reddy M S , Kloepper Joseph W
Published: September 2003

Plant-growth-promoting rhizobacteria (PGPR) are used on crops most often as seed treatments; however, an alternative application method for transplanted vegetables is mixing PGPR into the soilless medium in which the transplants are grown. Studies were undertaken to compare root colonization and persistence of rifampicin-resistant mutants of PGPR strains Bacillus pumilus SE34 and Pseudomonas fluorescens 89B61, SE34r and 89B61r, on tomato as a function of application method. When the bacteria were incorporated into Promix(tm) soilless medium at log 6, 7, and 8 colony- forming units/g, populations of strain SE34r per gram of medium maintained the initial inoculum densities, while populations of 89B61r decreased approximately one to two orders of magnitude by 4 weeks after planting. The populations of each PGPR strain colonizing roots after application into the soilless medium showed a similar pattern at 6 weeks as that at 4 weeks after planting, with higher populations on the whole roots and lateral roots than on the taproots. Strain SE34r but not 89B61r moved upwards and colonized the phyllosphere when incorporated into the soilless medium. Following application as seed treatment, populations of SE34r were significantly higher on upper roots and on the taproot than were populations following application through the soilless medium. Conversely, populations were higher on lower roots and lateral roots following application through the soilless medium than were populations following application as seed treatment. While strain SE34 enhanced plant growth with application both to the medium and as seed treatment, the level of growth promotion was significantly greater with application in the soilless medium. The results indicate that PGPR can be successfully incorporated into soilless media in vegetable transplant production systems.Key words: rhizobacteria, plant colonization, Bacillus pumilus, Pseudomonas fluorescens.
A calcium-dependent bacterial surface protein is involved in the attachment of rhizobia to peanut roots
Authors: Dardanelli Marta , Angelini Jorge , Fabra Adriana
Published: September 2003

As part of a project to characterize molecules involved in the crack-entry infection process leading to nodule development, a microscopic assay was used to visualize the attachment of cells of Bradyrhizobium sp. strains SEMIA 6144 and TAL 1000 (labelled by introducing a plasmid expressing constitutively the green fluorescent protein GFP-S65T) to Arachis hypogaea L. (peanut). Qualitative and quantitative results revealed that attachment was strongly dependent on the growth phase of the bacteria. Optimal attachment occurred when bacteria were at the late log or early stationary phase. Cell surface proteins from the Bradyrhizobium sp. strains inhibited the attachment when supplied prior to the attachment assay. Root incubation with a 14-kDa protein (eluted from sodium dodecyl sulphate  gel electrophoresis of the cell surface fraction) prior to the attachment assay resulted in a strong decrease of attachment. The adhesin appeared to be a calcium-binding protein, since cells treated with EDTA were found to be able to bind to adhesin-treated peanut roots. Since this protein has properties identical to those reported for rhicadhesin, we propose that this adhesin is also involved in the attachment process of rhizobia to root legumes that are infected by the crack-entry process.Key words: peanut, crack entry, rhizobia, attachment, adhesin.