bluuebunny/crossref_metadata_2025 huggingface dataset:
Pressure transients in a Canadian sewage force main
Authors: Axworthy David H , Chabot Normand
Published: February 2005

Severe water hammer following pump shutdown was suspected to be the cause of pipe displacement at a pump station in Saguenay, Quebec, because it appeared that insufficient surge protection was installed on the force main. To confirm this assertion and prevent further pipe displacement, data logging of a field test of the sewage pump station undergoing power failure was conducted in combination with the development of a water-hammer computer model for the design of additional surge protection measures. This paper describes the results of field testing, both before and after the installation of additional surge protection, and the calibration of a method of characteristics water-hammer model that accounts for vaporous cavitation and unsteady friction effects within the force main. Good agreement is shown between measured and computed pressure head histories at the pump station and at a vacuum relief valve following loss of power to a pump. To the authors' knowledge, this paper presents one of the first applications of the unsteady friction model referenced in this paper to a real system.Key words: sewage, force main, pump, water hammer, unsteady friction, data logging.
Developing a standard methodology for measuring and classifying construction field rework
Authors: Fayek Aminah Robinson , Dissanayake Manjula , Campero Oswaldo
Published: February 2005

As the industrial construction sector in Alberta faces a period of megaprojects, cost and schedule overruns are becoming a major concern for both owners and contractors. One factor that often contributes significantly to these overruns is construction field rework. Despite the significance of rework, there are few industry standards available for defining, quantifying, and classifying field rework. This paper presents the results of a pilot study, conducted on one such megaproject, that attempts to develop a standard definition of construction field rework, a standard index for its quantification, and an approach for classifying the causes that lead to field rework so that they can be remedied. The data collection methodology developed is discussed, and the findings that arise from this methodology for the case study are presented. The main conclusion of this paper is that the proposed methodology is quite effective in its thorough analysis and treatment of the field rework issue, and it can be used as a first step towards an industry Best Practice for measuring and classifying construction field rework. It can now be used on subsequent projects over time to collect a sufficient dataset, from which the construction industry can develop industry standards and statistics on construction field rework.Key words: field rework, industrial construction, rework classification, rework index.
Numerical parametric studies on the fire endurance of fibre-reinforced-polymer-confined concrete columns
Authors: Bisby L A , Kodur V KR , Green M F
Published: February 2005

Confinement of reinforced concrete columns by circumferential fibre reinforced polymer (FRP) wraps is a promising application of FRP materials for structural strengthening and seismic upgrading of deteriorated or under-strength members. However, if this technique is to be used in buildings, parking garages, and industrial structures, then the ability of FRP materials and FRP-wrapped columns to withstand the effects of fire must be demonstrated and evaluated. This paper presents the results of parametric studies conducted using a previously presented and partially validated numerical fire simulation model to investigate the effects of a number of parameters on the fire behaviour of FRP-wrapped reinforced concrete columns. It is demonstrated that appropriately designed and adequately protected FRP-wrapped reinforced concrete columns are capable of achieving fire endurances equivalent to conventionally reinforced concrete columns. Furthermore, this study also suggests that a holistic approach to the fire design of FRP-wrapped members is required, rather than an approach based on the specific performance of the FRP materials. Design recommendations for the fire-safe design of FRP-wrapped concrete columns are presented and discussed.Key words: reinforced concrete, rehabilitation, strengthening, fibre reinforced polymer, fire endurance, fire insulation, numerical modelling.
Evaluation of the expansion attained to date by concrete affected by alkalisilica reaction. Part II: Application to nonreinforced concrete specimens exposed outside
Authors: Smaoui Nizar , Fournier Benoit , Bérubé Marc-André , Bissonnette Benoit , Durand Benoit
Published: February 2005

In part I, relationships were obtained in the laboratory between the expansion due to alkali-silica reaction (ASR) and (i) the "stiffness damage test" (SDT), (ii) the "damage rating index" (DRI), and (iii) the surface cracking of the concrete. These tests were conducted on nonreinforced concrete blocks and cylinders made with various reactive aggregates and stored at 38 °C and >95% relative humidity. The objective of part II was to verify the validity of the relationships from part I for concrete elements made in the laboratory but exposed outside. On average for the 51 blocks and 14 slabs tested, the surface cracking increased with ASR expansion and approached the measured expansion in the case of the most severely exposed sections of the specimens tested. The ratio between the expansion estimated from the surface cracking and the measured expansion varied greatly from one specimen to another (between 0 and 4.3), however. Taking into account the type of reactive aggregate involved did not explain the situation. Despite a variety of reactive aggregates, a quite good relationship (coefficient of linear regression R2= 0.89) was obtained between the DRI and the ASR expansion for the six blocks cored and tested for DRI and SDT. This relationship is significantly different from those obtained in the laboratory, however. Moreover, the exposed concretes clearly differ from the laboratory concretes regarding the most important defects observed in the DRI test. As in the laboratory, the results obtained from the SDT seem to depend on the type of reactive aggregate involved. Nevertheless, this test globally supplied results with the best agreement with the measured expansion.Key words: aggregates, alkalisilica reaction, concrete expansion, damage rating index, petrography, stiffness damage test, surface cracking.
Dynamic response of a concrete dam impounding an ice-covered reservoir: Part I. Mathematical modelling
Authors: Bouaanani Najib , Paultre Patrick , Proulx Jean
Published: February 2005

This paper examines the dynamic response of a concrete dam impounding an ice-covered reservoir and subjected to forced-vibration testing. The analytical research presented is a follow-up to an extensive dynamic testing program carried out on a 84-m high concrete gravity dam located in northeastern Quebec, Canada, under harsh winter conditions, including a 1.0- to 1.5-m-thick ice sheet covering the reservoir. One of the major challenges encountered when analyzing ice-dam-reservoir-foundation interaction is modelling the complex nature of the ice and the boundary conditions governing reservoir motion. The problem is further complicated because there are little or no appropriate experimental data and observational evidence relevant to ice-dam interaction processes. Some of these challenges are addressed herein using a two-dimensional analytical approach, which investigates the effects due to ice cover, water compressibility, and reservoir bottom absorption. A frequency-domain substructure method technique is used and a new boundary condition along the ice-cover-reservoir interface is proposed. The technique developed is implemented in a finite element code specialized in the seismic analysis of concrete dams. Numerical results are discussed in the companion paper in this issue. Key words: gravity dams, concrete dams, ice, reservoirs, mathematical models, ice-structure interaction, fluid-structure interaction, forced-vibration testing, finite elements modelling.
Dynamic response of a concrete dam impounding an ice-covered reservoir: Part II. Parametric and numerical study
Authors: Bouaanani Najib , Paultre Patrick , Proulx Jean
Published: February 2005

This paper presents a numerical and parametric study of the effect of an ice cover on the dynamic response of a concrete dam using the approach proposed in the companion paper in this issue. The method was programmed and implemented in a finite element code specialized for the seismic analysis of concrete dams. The 84-m-high Outardes 3 concrete gravity dam in northeastern Quebec was chosen as a model for this research. Some basic aspects of the numerical model are established in this paper and we show that the ice cover affects the dynamic response of the ice–dam–reservoir system. Main features of this influence are emphasized and discussed in a parametric study through the analysis of: (i) acceleration frequency response curves at the dam crest, (ii) hydrodynamic frequency response curves inside the reservoir, and (iii) the hydrodynamic pressure distribution on the upstream face of the dam. Key words: gravity dams, concrete dams, ice, reservoirs, mathematical models, ice–structure interaction, fluid–structure interaction, forced-vibration testing, finite elements modelling.
Experimental study of human-induced dynamic forces due to bouncing on a perceptibly moving structure
Authors: Yao S , Wright J R , Pavic A , Reynolds P
Published: February 2005

This paper describes the first direct measurements of human-induced dynamic forces due to bouncing on a perceptibly moving force platform. A unique test rig, permitting a person to bounce physically on an idealized "single-degree-of-freedom system" with variable natural frequency and mass, is described and the test methodology explained. A set of representative results for different structure and bouncing frequencies is presented for one test subject. These results clearly demonstrate the effect that the flexibility of the structure has on the levels of force and dynamic response achieved. In particular, it was established that the applied force drops considerably when the subject bounces at a frequency fairly close to the natural frequency of the structure. However, it was found that it was physically not possible to bounce at or very close to the natural frequency for the configuration of the test rig chosen. Finally, the acceleration and displacement responses indicate that both the first and second harmonics of the bouncing force are capable of producing a near resonant response.Key words: crowd loading, flexible structure, dynamics, human-structure interaction, bouncing, jouncing, bobbing.
Nonlinear spectral dynamic analysis of guyed towers. Part I: Theory
Authors: Horr A M
Published: February 2005

One of the important parameters in the analysis and design of large space structures is to account for the dynamic forces induced by wind and the subsequent progressive collapse. During the past two decades, problems of extreme loading conditions have been considered by some authors, and special attention has been devoted to the collapse modes. Nonlinear time history dynamic analysis, involving the post-buckling characteristics of the space structures, may be analyzed using the conventional finite element method. However, to guarantee stability and accuracy of the solution, the number of elements used to model the structure may be very large. In this respect, the nonlinear spectral element method (SEM) is developed for analyzing dynamic problems in large space structures. Through use of a computer program, the proposed method has been used to obtain the nonlinear dynamic response of guyed power transmission towers under severe wind loading condition. Key words: nonlinear dynamic analysis, space structures, guyed towers, spectral element method.
Nonlinear spectral dynamic analysis of guyed towers. Part II: Manitoba towers case study
Authors: Horr A M , Yibulayin A , Disney P
Published: February 2005

Dynamic response of large complex space structures under wind loading is important in terms of performance and safety. Conventional method of wind loading calculation has been used successfully in codes to analyze large space structures. The method can be applied by approximating the air pressure, induced by wind, on the surfaces of structures. Although this replaces a wind loading test using complicated wind tunnel tests for any structural systems, the accuracy of the method, in the case of complex geometry guyed tower structures, is a matter of consideration. Hence, it is desirable to search for a procedure with more accuracy and reliability. In this respect, attention is paid to the advanced spectral element method and the computational fluid dynamics. Using the proposed formulation, a material and geometric nonlinear dynamic analyses have been performed to simulate post-buckling behaviours and also collapse modes for series of Manitoba Hydro's guyed towers under extreme wind loading conditions. Key words: computational fluid dynamics, wind loading, collapse mode, nonlinear analysis, post-buckling.
Application of recycled waste aggregate to lean concrete subbase in highway pavement
Authors: Cho Yoon-Ho , Yeo Sung-Hun
Published: February 2005

As aggregates recycled from various types of construction waste are continuously being produced, interest has focused on how to apply them for use in highway pavement. This paper considers the application of waste aggregates to lean concrete, based on basic mechanical property tests and environmental toxicity. Compared with natural aggregates, waste aggregates derived mainly from recycled concrete have low specific gravity and high water absorption characteristics. After testing their environmental toxicity, it was found that waste aggregates do not release any metallic ions when introduced to alkaline conditions but do release a small but seemingly harmless amount of metallic ions when introduced to acidic solutions. Concrete made with waste aggregates has significant limitations in strength, particularly flexural strength, which is the main parameter of quality control and design for concrete pavement. It is therefore not practical to use waste aggregates for the surface layer of concrete without using additives or special treatments. It is possible, however, to apply concrete with waste aggregates for lean bases. In testing, lumps of asphalt, cement paste, bricks, and glass were classified as impurities and were observed for changes in strength based on the percentage of impurities used. If the amount of impurities is greater than 25%, the 7-d compressive strength does not meet the strength requirements specified for lean concrete.Key words: recycled waste aggregates, lean concrete, impurity content, concrete pavement.
Aspects aléatoires de l'érosion d'une digue : simulations de la brèche par des algorithmes génétiques
Authors: Seidou Ousmane , Marche Claude , Mahdi Tewfik
Published: February 2005

Attempts to forecast the final form of a dam-break suffer from various uncertainty sources such as field data (topography, hydraulic and geotechnical parameters), and modeling assumptions. So the result seems to be at least partially chaotic and difficult to match with the objectives of the dam-safety engineers in which the goal is to model dam-break flow evolution in time. On the other hand, the principle of minimal energy dissipation rate makes it possible to predict the shape towards which the geometry of the breach will evolve to under stationary hydraulic conditions. In this article, one uses energy minimization by a genetic algorithm to integrate at the same time the two concepts of random result and convergence towards an equilibrium state. They are used to simulate the submersion failure of a clay dam, and the results agree reasonably with the field data. This approach makes it possible to obtain as realistic breach shapes as those obtained by actual models, and to introduce a random component in the process of dam-breach formation, which remains, however, guided by a physical principle.Key words: erosion, dam breach, genetic algorithms, sediment transport.
Morphological changes of Giardia lamblia cysts after treatment with ozone and chlorine
Authors: Li Yanning , Smith Daniel W , Belosevic Miodrag
Published: February 2005

Morphological changes of Giardia lamblia cysts after treatment with ozone, free chlorine, or combinations of oxidants were documented using transmission electron microscopy. Experiments were conducted using in vitro-derived G. lamblia cysts. Nucleic acid staining employing LIVE/DEAD BacLightTM was used for the evaluation of cyst viability. Cyst wall damage, plasmalemma breakage, lysis of peripheral vacuoles, and nuclear degradation were main features of cyst injury elicited by ozone or chlorine. Cell death pathways were found to be oxidant-specific. Morphological changes in G. lamblia cysts treated with both ozone and chlorine showed that the preconditioning of the cyst wall by exposure to the first oxidant allowed for easier penetration and increased damage induced by the second oxidant. Taken together, our results indicate that pretreatment of G. lamblia cysts with low doses of one oxidant significantly increases the susceptibility of the parasite to the sequentially applied second oxidant. Key words: ozone, chlorine, oxidation, Giardia, inactivation, morphology, cell death, synergy.
Forecasting the performance of membrane bioreactor process for groundwater denitrification
Authors: Tsai Hsun-Hao , Ravindran Varadarajan , Williams Mark D , Pirbazari Massoud
Published: February 2005

A mathematical model was developed for performance prediction, simulation, and design of membrane bioreactor (MBR) process for biological denitrification of two groundwaters. The process mass transfer chronologically involved the following aspects: biological reaction in bulk liquid phase, film transfer from liquid phase to biofilm, biofilm diffusion and biological reaction, adsorption at the biofilm–adsorbent interface, and adsorbent particle diffusion. The liquid film and biofilm transport equations constituted a time-varying moving boundary problem. Model biokinetic parameters for denitrification using ethanol as electron donor were estimated from batch reactor studies. Laboratory-scale MBR experiments showed that steady state was reached rapidly and over 99% nitrate removal was consistently achieved for influent concentrations in the 16 to 45 mg/L range. Furthermore, comparison of experimental data and model predictions established the accuracy, reliability, and utility of the model. The MBR experiments also demonstrated that powdered activated carbon (PAC) did not particularly improve nitrate removal or permeate flux. Model sensitivity studies illustrated the dependence of process dynamics on parameters related to influent nitrate concentration, biomass concentration, biodegradation kinetics, and hydraulic residence time. Key words: bioreactor, membrane bioreactor, denitrification, biodegradation, membrane filtration, water treatment, membrane fouling.
Comparison of process options for treatment of water treatment residual streams
Authors: Bourgeois J C , Walsh M E , Gagnon G A
Published: February 2005

Spent filter backwash water (SFBW) and clarifier sludge comprise the majority of the waste streams from conventional surface water treatment plants and collectively are referred to as composite residuals stream. Composite residuals streams can comprise up to 3–10% of the plant throughput and generally consist of concentrated metals (e.g., aluminum), colloidal material, natural organic matter (NOM), and pathogens (e.g., Giardia and Cryptosporidium). This research project evaluated the performance of four different treatment processes in terms of their capability of restoring this waste stream to a quality that was equal to or better than that of the source water quality. The unit operations evaluated were (i) gravity thickening, (ii) sedimentation with reflocculation, (iii) dissolved air flotation (DAF) with reflocculation, and (iv) ultrafiltration (UF). The water quality from the optimal trials met or exceeded the average raw water quality of the source water for all measured parameters with the exception of manganese. The optimal pH for sedimentation was determined to be 6.0 with no alum addition. The best coagulant dosage and recycle ratio for dissolved air flotation (DAF) were found to be 30 mg/L and 20%, respectively. The optimum settling time for thickening was determined to be 0.8–1.0 d, after which soluble metal concentrations began to increase because of re-solubilization. Ultrafiltration required no coagulant and yielded superior results to the other unit operations evaluated. Key words: filter backwash water, residual treatment, gravity thickening, sedimentation, dissolved air flotation, ultrafiltration.
Bench-scale study of the biodegradation of grease trap sludge with yard trimmings or synthetic food waste via composting
Authors: Lemus G R , Lau A K , Branion R M.R. , Lo K V
Published: February 2005

The aim of this study was to evaluate the biodegradation of lipid-rich residues (grease trap sludge) when composted under aerobic conditions, using two different substrates — yard trimmings and synthetic food waste. Addition of lipids seemed to have a very marked effect on the temperature profiles. For the high-rate phase of composting, grease trap sludge was degraded by 39%–51% for the yard trimmings experiments and 10%–27% for the synthetic food waste treatments. For the curing phase, lipids reductions were 9%–26% and 16%–45% for treatments with yard trimmings and synthetic food waste, respectively. For the active phase of composting, the volatile solids biodegradation rate coefficient for the grease trap sludge treatments was 0.009–0.033 d–1, while the average biodegradation rate coefficient for grease trap sludge alone was 0.058 d–1. The yard trimmings treatment with grease trap sludge added at 5% dry solids (ds) resulted in enhanced performance, in terms of temperature profile, rate and extent of biodegradation of solids and lipids, and reduction in wet mass and water content, when compared with the composting of yard trimmings alone. For the synthetic food waste treatments, the addition of grease trap sludge (up to 10% ds) seemed to be inhibitory of the composting process. Key words: lipid residues, compostability, biodegradation rate, biodegradation extent.
Optimized extraction of total proteic mass from water hyacinth dry leaves
Authors: Bodo Ruben , Ahmanache Kamel , Hausler Robert , Azzouz Abdelkrim
Published: February 2005

Optimization and effect simulation of the one-step solid:liquid extraction of the proteic mass from water hyacinth were achieved for glutathione recovery, through a factorial 33 experiment design. The experiment was carried out using dry water hyacinth leaves, previously crushed into a fine powder with particle size not exceeding 0.1 mm, and a sodium phosphate buffer as the extracting phase. For this purpose, 27 attempts were made by varying the dry leaves to buffer w/v ratio (solid:liquid (S/L)), the buffer pH, and extraction time, which are regarded as being key parameters. The total protein mass extracted attained values of 75–76 wt.% of the initial mass of dry hyacinth leaves, at 30 °C, S/L = 1:7.5–1:8.0 and pH 8.2. Time has no influence on the amount of extracted proteins, but a minimum time of 20 min is recommended. The effects of acidity and ionic strength upon protein fractionation were also investigated via potentiometric titrations of the collected extract with citric acid and ammonium sulphate, respectively, in a temperature range (20–60 °C). Most of proteins precipitate at pH 4.5–6.0 in the presence of citric acid and at pH 6.5–5.85 in the presence of ammonium sulphate. Glutathione was detected using high performance liquid chromatography (HPLC) in a liquid fraction after protein precipitation at pH = 5.65 in the presence of ammonium sulphate. Key words: Factorial 33 Design, solid:liquid extraction, water hyacinth, protein separation, optimization, glutathione.
Stormwater runoff from open windrow composting facilities
Authors: Wilson Bruce G , Haralampides Katy , Levesque Sheila
Published: February 2005

Most of the 4000 composting sites in North America employ open windrow composting techniques in which rainfall often comes into contact with the compost. The resulting runoff can leach contaminants from the compost, making the runoff unsuitable for direct release into receiving waters. Stormwater from these facilities is usually collected in a detention pond and treated prior to release. There is little guidance for determining the appropriate size of these runoff detention ponds. One barrier to modelling the hydrology of composting sites is a lack of basic information regarding rainfall–runoff relationships for compost. This note describes the results of laboratory and field experiments designed to estimate the fraction of rainfall incident on a compost windrow that leaches from the windrow onto the composting pad and into the detention pond. The results indicate that approximately 68% of the rainfall incident on a saturated compost windrow will eventually run off. Key words: solid waste management, composting, runoff, detention pond.
Time course observations of nitrifying biofilm development using microelectrodes
Authors: Li Jin , Bishop Paul L
Published: February 2005

Nitrifying biofilms were cultured in laboratory scale rotating drum biofilm reactors. Biofilm growth, substrate removal and product formation were monitored using microelectrodes with tip diameters less than 5 µm throughout the experiment. Three stages were observed during the formation of the biofilm: establishment of heterotrophic bacteria, establishment of nitrifiers, and possible establishment of denitrifiers. At each stage of the biofilm formation, microelectrode measurements were made to obtain the microprofiles of dissolved oxygen, ammonium, nitrate, pH, and redox potential within the biofilms. The results of this study provide validation of the heterogeneous nature of biofilm and the stratification of different microbial processes in biofilms. Key words: nitrification, denitrification, biofilm, microelectrode, biofilm formation, mass transport.
Modeling the transport of dissolved contaminants originating from a nonaqueous phase liquid source containing polycyclic aromatic hydrocarbon compounds in groundwater
Authors: Lee Kenneth Y , Kostarelos Konstantinos , Fennell Donna E
Published: February 2005

A three-dimensional mathematical model is developed for simulating the transport of dissolved contaminants originating from a well-defined, multicomponent nonaqueous phase liquid (NAPL) source containing polycyclic aromatic hydrocarbon (PAH) compounds in groundwater. The dissolution process for each NAPL component is envisioned to occur in a successive series of small dissolution intervals (or pulses). The equilibrium aqueous phase concentration of each component and the source dimensions are assumed to remain constant for the duration of each dissolution interval. The model accounts for possible solidification of PAH components as the NAPL source dissolves. Aqueous phase contaminant concentrations resulting from each dissolution interval are calculated using an existing analytical solution. A synthetic PAH-rich NAPL mixture consisting of benzene and eight PAH components is used for model simulations. The model is useful for evaluation and prediction of downstream aqueous phase contaminant concentrations resulting from dissolution of a PAH-rich NAPL source. Key words: contaminant transport, groundwater, nonaqueous phase liquid (NAPL), mathematical modeling, polycyclic aromatic hydrocarbons.
An experimental procedure for identifying the aerobic-phase biological source of nitrous oxide in anoxic–aerobic wastewater treatment systems
Authors: Shiskowski D M , Simm R A , Mavinic D S
Published: February 2005

This paper describes a relatively simple experimental procedure used to assess the relative contribution of autotrophic and heterotrophic organisms in the generation of aerobic-phase nitrous oxide from a mixed microbial population in a bench-scale, anoxic–aerobic, sequencing batch reactor (SBR) wastewater treatment system. The procedure eliminated ammonia oxidation from a "perturbation" cycle, while maintaining pH and dissolved oxygen levels similar to the "baseline" cycle. Nitrite and carbon oxidation were maintained during the perturbation cycle. Compared to more complex methods such as stable isotope labelling techniques, the described procedure is logistically simple and requires equipment readily available in most environmental engineering laboratories. When applied to an SBR system treating synthetic wastewater (influent ammonia N concentration = 160 mg/L), the experimental results strongly suggest that essentially all of the nitrous oxide produced during the aerobic phase of the cycle was generated by autotrophic, ammonia oxidizing organisms. Little, if any, nitrous oxide appeared to be generated by heterotrophic denitrification during the aerobic phase of the cycle. Key words: nitrification, aerobic denitrification, nitrous oxide, nitrite reduction.
Low genetic diversity amongFrankiaspp. strains nodulating sympatric populations of actinorhizal species of Rosaceae,Ceanothus(Rhamnaceae) andDatisca glomerata(Datiscaceae) west of the Sierra Nevada (California)
Authors: Vanden Heuvel Brian D , Benson David R , Bortiri Esteban , Potter Daniel
Published: February 2005

Frankia spp. strains typically induce N2-fixing root nodules on actinorhizal plants. The majority of host plant taxa associated with the uncultured Group 1 Frankia strains, i.e., Ceanothus of the Rhamnaceae, Datisca glomerata (Datiscaceae), and all actinorhizal members of the Rosaceae except Dryas, are found in California. A study was conducted to determine the distribution of Frankia strains among root nodules collected from both sympatric and solitary stands of hosts. Three DNA regions were examined, the 5' end of the 16S rRNA gene, the internal transcribed spacer region between the 16S and 23S rRNA genes, and a portion of the glutamine synthetase gene (glnA). The results suggest that a narrow range of Group 1 Frankia spp. strains dominate in root nodules collected over a large area of California west of the Sierra Nevada crest with no apparent host-specificity. Comparisons with Group 2 Frankia strain diversity from Alnus and Myrica within the study range suggest that the observed low diversity is peculiar to Group 1 Frankia strains only. Factors that may account for the observed lack of genetic variability and host specificity include strain dominance over a large geographical area, current environmental selection, and (or) a past evolutionary bottleneck.Key words: actinorhizal Rosaceae, Ceanothus, Frankia, Datisca, strain diversity.
Differentiation of group VIII Spiroplasma strains with sequences of the 16S–23S rDNA intergenic spacer region
Authors: Regassa Laura B , Stewart Kimberly M , Murphy April C , French Frank E , Lin Tao , Whitcomb Robert F
Published: February 2005

Spiroplasma species (Mollicutes: Spiroplasmataceae) are associated with a wide variety of insects, and serology has classified this genus into 34 groups, 3 with subgroups. The 16S rRNA gene has been used for phylogenetic analysis of spiroplasmas, but this approach is uninformative for group VIII because the serologically distinct subgroups generally have similarity coefficients >0.990. Therefore, we investigated the utility of the 16S–23S rRNA spacer region as a means to differentiate closely related subgroups or strains. We generated intergenic sequences and detailed serological profiles for 8 group VIII Spiroplasma strains. Sequence analyses using Maximum Parsimony, Neighbor Joining, and Maximum Likelihood placed the strains into 2 clades. One clade consisted of strains BARC 2649 and GSU5367. The other clade was divided into clusters containing representatives of the 3 designated group VIII subgroups (EA-1, DF-1, and TAAS-1) and 3 previously unclassified strains. The stability of the positions of the strains in various analytical models and the ability to provide robust support for groupings tentatively supported by serology indicates that the 16S–23S intergenic rDNA sequence will prove useful in intragroup analysis of group VIII spiroplasmas.Key words: Mollicutes, Spiroplasma, phylogeny, Tabanidae.
Characteristics of rhizobia nodulating beans in the central region of Minnesota
Authors: Bernal G R , Tlusty B , de Jensen C Estevez , van Berkum P , Graham P H
Published: February 2005

Until recently, beans (Phaseolus vulgaris L.) grown in Minnesota were rarely inoculated. Because of this, we hypothesized that bean rhizobia collected in Minnesota would either share characteristics identifiable with Rhizobium etli of Mesoamerican or Andean origin, introduced into the region as seed-borne contaminants, or be indigenous rhizobia from prairie species, such as Dalea spp. The latter organisms have been shown to nodulate and fix N2with Phaseolus vulgaris. Rhizobia recovered from the Staples, Verndale, and Park Rapids areas of Minnesota were grouped according to the results of BOXA1R–PCR fingerprint analysis into 5 groups, with only one of these having banding patterns similar to 2 of 4 R. etli reference strains. When representative isolates were subject to fatty acid - methyl ester analysis and 16S rRNA gene sequence analysis, the results obtained differed. 16S rRNA gene sequences of half the organisms tested were most similar to Rhizobium leguminosarum. Rhizobia from Dalea spp., an important legume in the prairie ecosystem, did not play a significant role as the microsymbiont of beans in this area. This appears to be due to the longer time needed for them to initiate infection in Phaseolus vulgaris. Strains of Rhizobium tropici IIB, including UMR1899, proved tolerant to streptomycin and captan, which are commonly applied as seed treatments for beans. Local rhizobia appeared to have very limited tolerance to these compounds.Key words: Rhizobium diversity, Phaseolus vulgaris, seed treatment, taxonomy.
Endophytic fungal diversity of 2 sand dune wild legumes from the southwest coast of India
Authors: Seena S , Sridhar K R
Published: February 2005

Endophytic fungi of 3 age classes (seeds, seedlings, and mature plants) and 5 tissue classes (cotyledons, seed coats, roots, stems, and leaves) of coastal sand dune legumes Canavalia cathartica and Canavalia maritima were assessed by plating surface-sterilized segments on malt extract agar. Forty-six fungal taxa comprising 6 ascomycetes, 33 mitosporic fungi, 2 zygomycetes, and 5 sterile morphospecies were recovered. There was no significant difference in the colonization frequency of endophytes between plant species (p = 0.4098, Student's t test). Among the age classes, endophytic fungi colonized over 90% of seedlings and mature plants. Similarly, among tissue classes, endophytic fungi colonized over 90% of root, stem, and leaf segments. Diversity and richness of endophytic fungi were higher in C. cathartica than in C. maritima. Rarefaction curves revealed a "higher expected number of species" in mature plants of C. cathartica and seedlings of C. maritima, whereas it was highest in leaves of both plant species. The most dominant endophyte, Chaetomium globosum, colonized over 50% of the root, stem, and leaf segments of C. maritima and over 50% of the root segments of C. cathartica. The colonization frequency of C. globosum was found to be 5%–12.5% in seeds and increased up to 40%–64.4% in seedlings or mature plants. Halosarpheia sp. was the only marine fungus recovered among the endophytes.Key words: sand dunes, coast, legumes, Canavalia, diversity, endophytes, fungi, Chaetomium globosum.
Deletion of theCandidaalbicansG-protein-coupled receptor, encoded byorf19.1944and its alleleorf19.9499, produces mutants defective in filamentous growth
Authors: Sciascia Quentin L , Sullivan Patrick A , Farley Peter C
Published: February 2005

Filamentous growth of Candida albicans occurs in response to a variety of environmental signals. The C. albicans gene orf19.1944 and its allele orf19.9499 are identical and are predicted to encode an 823-residue, 7-transmembrane-domain protein that has all the expected features of a G-protein-coupled receptor. The protein is 20.9% identical to the Saccharomyces cerevisiae Gpr1p receptor that signals both glucose availability and nitrogen limitation. Deletion of both copies of the gene in C. albicans abolished filamentation by colonies embedded in rich media (YPS, YPGal, and YPGlu), whereas mutants carrying a single copy of the gene were indistinguishable from the parental strain under these conditions. On medium containing low concentrations of ammonia (SLAD and SLAM media), surface colonies of both the homozygous deletion mutants and the mutants carrying a single copy of the gene were defective in filamentation. Serum-induced germ tube formation was unaffected by deletion of this gene, as was filamentation of the mutants growing on the surface of solid Spider medium at 37 °C or embedded in solid Spider medium at 25 °C. The protein encoded by orf19.1944 and orf19.9499 has a role in filamentation by both surface and embedded colonies, presumably as a sensor of environmental cues.Key words: Candida albicans, G-protein-coupled receptor, orf19.1944, embedded agar, filamentation.
Potential application of low-stringency single specific primer-PCR in the identification ofLeptospirain the serum of patients with suspected leptospirosis
Authors: Ooteman Márcia Costa , Vago Annamaria Ravara , Koury Matilde Cota
Published: February 2005

In this study we tested the potential use of low-stringency single specific primer-PCR (LSSP-PCR) for genetically typing Leptospira directly from biological samples. Serum samples obtained from 29 patients with clinically suspected leptospirosis were amplified by specific PCR, using the previously selected G1 and G2 primers. The PCR products of approximately 300 bp were subsequently used as a template for LSSP-PCR analysis. We were able to produce genetic signatures from the leptospires present in the human samples, which permitted us to make a preliminary identification of the infective serovar by comparing the LSSP-PCR profiles obtained directly from serum samples with those from reference leptospires. Thus, LSSP-PCR has the potential to become a useful diagnostic tool for identifying leptospires in biological samples without the need for bacteria isolation and culture.Key words: LSSP-PCR, Leptospira.
Fate ofEscherichia coliO157:H7 in irrigation water on soils and plants as validated by culture method and real-time PCR
Authors: Ibekwe A Mark , Watt Pamela M , Shouse Peter J , Grieve Catherine M
Published: February 2005

One of the most common vehicles by which Escherichia coli O157:H7 may be introduced into crops is contaminated irrigation water. Water contamination is becoming more common in rural areas of the United States as a result of large animal operations, and up to 40% of tested drinking-water wells are contaminated with E. coli. In this study, 2 contrasting soil samples were inoculated with E. coli O157:H7 expressing green fluorescent protein through irrigation water. Real-time PCR and culture methods were used to quantify the fate of this pathogen in phyllosphere (leaf surface), rhizosphere (volume of soil tightly held by plant roots), and non-rhizosphere soils. A real-time PCR assay was designed with the eae gene of E. coli O157:H7. The probe was incorporated into real-time PCR containing DNA extracted from the phyllosphere, rhizosphere, and non-rhizosphere soils. The detection limit for E. coli O157:H7 quantification by real-time PCR was 1.2 × 103in the rhizosphere, phyllosphere, and non-rhizosphere samples. E. coli O157:H7 concentrations were higher in the rhizosphere than in the non-rhizosphere soils and leaf surfaces, and persisted longer in clay soil. The persistence of E. coli O157:H7 in phyllosphere, rhizosphere, and non-rhizosphere soils over 45 days may play a significant part in the recontamination cycle of produce in the environment. Therefore, the rapidity of the real-time PCR assay may be a useful tool for quantification and monitoring of E. coli O157:H7 in irrigation water and on contaminated fresh produce.Key words: real-time PCR, Escherichia coli O157:H7, irrigation, survival, quantification.
Optimization of extracellular fungal peroxidase production by 2 Coprinus species
Authors: Ikehata Keisuke , Pickard Michael A , Buchanan Ian D , Smith Daniel W
Published: February 2005

Optimum culture conditions for the batch production of extracellular peroxidase by Coprinus cinereus UAMH 4103 and Coprinus sp. UAMH 10067 were explored using 2 statistical experimental designs, including 2-level, 7-factor fractional factorial design and 2-factor central composite design. Of the 7 factors examined in the screening study, the concentrations of carbon (glucose) and nitrogen (peptone or casitone) sources showed significant effects on the peroxidase production by Coprinus sp. UAMH 10067. The optimum glucose and peptone concentrations were determined as 2.7% and 0.8% for Coprinus sp. UAMH 10067, and 2.9% and 1.4% for C. cinereus UAMH 4103, respectively. Under the optimized culture condition the maximum peroxidase activity achieved in this study was 34.5 U·mL–1 for Coprinus sp. UAMH 10067 and 68.0 U·mL–1 for C. cinereus UAMH 4103, more than 2-fold higher than the results of previous studies.Key words: Coprinus peroxidase, central composite design, fractional factorial design, production optimization, response surface.
Cryptococcus festucosus sp. nov. a new hymenomycetous yeast in the Holtermannia clade
Authors: Golubev Wladyslav I , Sampaio José P , Alves Leonor , Golubev Nikita W
Published: February 2005

Five yeast strains belonging to the genus Cryptococcus Vuillemin were isolated from steppe plants and turf collected in the Prioksko-terrasny biosphere reserve (Moscow region, Russia). Sequence analyses of the D1/D2 domains of the 26S rDNA and of the internal transcribed spacer region revealed that these yeast strains and strain CBS 8016 have almost identical sequences and belong to the Holtermannia clade of the Tremellomycetidae (Basidiomycota, Hymenomycetes). A novel species named Cryptococcus festucosus (type strain VKM Y-2930) is proposed to accommodate these strains. Physiological characteristics and mycocin sensitivity patterns distinguishing Cryptococcus festucosus from the other species of this clade are presented.Key words: mycocin sensitivity, rDNA sequencing, Cryptococcus, Holtermannia.
In vitro attachment of phylloplane yeasts toBotrytis cinerea,Rhizoctonia solani, andSclerotinia homoeocarpa
Authors: Allen Tom W , Burpee Leon L , Buck James W
Published: February 2005

The ability of yeasts to attach to hyphae or conidia of phytopathogenic fungi has been speculated to contribute to biocontrol activity on plant surfaces. Attachment of phylloplane yeasts to Botrytis cinerea, Rhizoctonia solani, and Sclerotinia homoeocarpa was determined using in vitro attachment assays. Yeasts were incubated for 2 d on potato dextrose agar (PDA) prior to experimentation. A total of 292 yeasts cultured on PDA were screened for their ability to attach to conidia of B. cinerea; 260 isolates (89.1%) attached to conidia forming large aggregates of cells, and 22 isolates (7.5%) weakly attached to conidia with 1 or 2 yeast cells attached to a few conidia. Ten yeasts (3.4%), including 8 isolates of Cryptococcus laurentii, 1 isolate of Cryptococcus flavescens, and an unidentified species of Cryptococcus, failed to attach to conidia. All non-attaching yeasts produced copious extracellular polysaccharide (EPS) on PDA. Seventeen yeast isolates did not attach to hyphal fragments of B. cinerea, R. solani, and S. homoeocarpa after a 1 h incubation, but attachment was observed after 24 h. Culture medium, but not culture age, significantly affected the attachment of yeast cells to conidia of B. cinerea. The 10 yeast isolates that did not attach to conidia when grown on agar did attach to conidia (20%–57% of conidia with attached yeast cells) when cultured in liquid medium. Attachment of the biocontrol yeast Rhodotorula glutinis PM4 to conidia of B. cinerea was significantly greater at 1 × 107yeast cells·mL–1than at lower concentrations of yeast cells. The ability of yeast cells to attach to fungal conidia or hyphae appears to be a common phenotype among phylloplane yeasts.Key words: adhesion, biological control, Cryptococcus laurentii, Rhodotorula glutinis.
Phylogenetic analysis of bacterial populations in waters of the former Texcoco Lake, Mexico
Authors: Jan-Roblero Janet , Magos Xochitl , Fernández Luis , Hernández-Rodríguez César , Le Borgne Sylvie
Published: February 2005

Molecular techniques were used to compare the compositions of the bacterial communities of the 2 following lagoons from the former soda Texcoco Lake, Mexico: the restored Facultativa lagoon and the Nabor Carrillo lagoon. Ribosomal intergenic spacer analysis (RISA) revealed that bacterial communities of the 2 lagoons were different and presented a relatively low diversity. Clone libraries of 16S rDNA genes were constructed, and significant phylotypes were distinguished by restriction fragment length polymorphism (RFLP). A representative clone from each phylotype was partially sequenced. Molecular identification and phylogenetic analyses based on ribosomal sequences revealed that the Facultativa lagoon harbored mainly γ- and β-Proteobacteria, low G+C Gram-positive bacteria, and several members of the Halobacteriaceae family of archaea. The Nabor Carrillo lagoon mainly included typical halophilic and alkaliphilic low G+C Gram-positive bacteria, γ-Proteobacteria, and β-Proteobacteria similar to those found in other soda lakes. Several probably noncultured new bacterial species were detected. Three strains were isolated from the Nabor Carrillo lagoon, their partial 16S rDNA sequences were obtained. On this basis, they were identified as Halomonas magadiensis (H1), Halomonas eurihalina (H2), and Staphylococcus sciuri (H3). This is the first study that uses molecular techniques to investigate potential genetic diversity in the Texcoco lakes. In this preliminary evaluation, we infer the presence of alkalophilic, halophilic, or haloalkaliphilic bacteria potentially useful for biotechnology.Key words: bacterial diversity, 16S rDNA gene, soda lakes, former soda Texcoco Lake, Mexico, alkaliphiles, halophiles, haloalkaliphiles.
Isolation of sterols from the marine fungusCorollospora lacera
Authors: MacKenzie Sabrena E , Gurusamy G Soundari , Piórko Adam , Strongman Douglas B , Hu Tingmo , Wright Jeffrey LC
Published: February 2005

Several marine fungi collected from the waters of Prince Edward Island, Canada, were screened for the presence of natural products exhibiting antibacterial activity. Both broths and mycelia of these fungi were studied using the bioassay-guided chromatographic separation. The 4 fractions from the extract of mycelia of Corollospora lacera exhibited weak antibacterial activity and were analyzed further. From these fractions, 2 sterols (5α,8α-epidioxyergosterol and 22E,24R-ergosta-7,22-diene-3β,5α,6β-triol) and a 3:1 mixture of linoleic and oleic acids were isolated. The presence of ergosterol was confirmed in dichloromethane extracts of mycelia of every fungus in this study and this sterol was isolated from the extract of mycelium of Corollospora lacera. Two other known compounds (5-hydroxymethylfuran-2-carbaldehyde and bis(2-ethylhexyl) phthalate), were isolated from the dichloromethane extract of mycelium of Monodictys pelagica. The phthalate was reported in the literature as a metabolite isolated from the fungi, but in our study it was proven to be an artifact of the culturing and (or) extraction procedures rather than a true fungal metabolite.Key words: marine fungus, sterols, metabolites.