bluuebunny/crossref_metadata_2025 huggingface dataset:
Particle reduction study of flocculation mixing by means of grids
Authors: Liem L E , Smith Daniel W , Stanley S J
Published: April 2011

A flocculation study was completed by means of a vertically oscillating grid mixing device. Five types of single grids with different solidity ratios were vertically oscillated inside a 2 L jar to promote floc aggregation. Kaolin was used as the simulated turbid particles and alum was applied as the chemical coagulant. The method of measurement was completed based on the particle reduction represented by the settled water turbidity. It was found that low turbidity readings could be achieved at a wide range of average volume velocity gradient [Formula: see text], especially in the case of high solidity ratio types of grids. This indicates that the grid mixing had a stable performance and was not greatly affected by mixing variations in the vessel. The floc aggregation and erosion rate coefficient analysis showed that the grid mixing produced particle contacts with low break-up rate. A general relationship among [Formula: see text], flocculation performance parameters, and grid physical characteristics was found, indicating that the flocculation performance was easily controlled. This study has shown the potential of grids as a mixing device to produce an excellent mixing environment for floc aggregation.Key words: flocculation, grid, solidity ratio, kaolin, alum, [Formula: see text], turbidity.
Construction de la paroi au coulis ciment-bentonite sous la digue nord de l'aménagement hydroélectrique La Grande 1
Authors: Massiéra Michel , Levay Jerry
Published: April 2011

As part of the La Grande complex, in northern Québec, the development of the LG-1 hydroelectric project required the construction of a 2444 m long dyke on the north shore. The presence of a wide sensitive marine clay terrace covered with deltaic and river sand and silt deposits called for several design features, including the construction of a cement-bentonite cutoff through the sand and silt deposits on the terrace. This paper describes the different construction phases of the cement-bentonite cutoff with emphasis on excavation procedure and quality control.Key words: bentonite, cement, construction, cutoff, excavation, slurry trench.
Confinement of reinforced concrete columns with fibre-reinforced composite sheets - an experimental study
Authors: Demers M , Neale K W
Published: April 2011

The wrapping of fibre-reinforced composite sheets around concrete columns is a promising method for structural strengthening and repair. This rehabilitation technique is of practical interest, as the lay-up of the sheets is rather easy; it does not require specialized tools, and the epoxy resins employed cure at ambient temperatures. Here, results of an experimental investigation are reported for 16 round reinforced concrete columns 300 mm in diameter and 1200 mm high. These columns were confined by means of carbon-epoxy sheets and loaded concentrically in axial compression. The effects of various parameters on the structural behaviour of the confined concrete columns are investigated. These parameters included the concrete strength, longitudinal steel reinforcement, steel stirrups, steel corrosion, and concrete damage. The test results show that composite confinement can considerably enhance the structural performance of concrete columns, especially with regard to ductility. The potential to restore the full strength of severely damaged columns is also demonstrated, as retrofitted columns exhibit axial load carrying capacities equal or superior to those of undamaged columns, along with significant increases in ductility. The contribution of the transverse steel reinforcement is seen to be minimal, as long as the stirrup spacing is medium to large. For such cases tests on plain concrete cylinders are sufficient for further investigations of this retrofit method, as the key parameters which really affect strength and ductility are the concrete strength, composite fibre type, and sheet thickness.Key words: fibre composite sheets, confinement, concrete, column repair, rehabilitation, strengthening.
Traitement de l'air par biofiltration
Authors: Jorio Hasnaa , Heitz Michèle
Published: April 2011

During several decades, there have been numerous studies and attempts in the field of the treatment of volatile organic solvent contaminated air, with the aim of finding a more efficient and less expensive process. In parallel with the traditional air treatment technologies, biological processes have emerged in recent years. Biofiltration appears to be a particularly preferred path due to its efficiency, its environmental aspects, and its lower costs. In this paper, the biofiltration technology is positioned in relation to conventional techniques and other biological air treatments. Subsequently, after a short historical account of biofiltration, the focus is put on the main objective of this literature review, presenting the current knowledge about the basic principles of the process, its applicability, operational conditions that influence performance and reliability of this process, and recent developments in mathematical biofilter modeling. Finally, industrial applications and biofiltration processing costs are briefly discussed.Key words: biofilter, VOC, biodegradation, modeling, kinetics, humidity, temperature, pH, nutrients, oxygen.[Journal translation]
Minimum flexural reinforcement for T-beams made of higher strength concrete
Authors: Ozcebe Guney , Ersoy Ugur , Tankut Tugrul
Published: April 2011

Design codes specify minimum flexural reinforcement for reinforced concrete beams. With the extensive use of higher strength concrete, the empirical expressions of the past for minimum flexural reinforcement, in which the concrete strength is not considered, had to be revised. Six reinforced concrete T-beams, having small ratios of flexural reinforcement, were tested to study the behaviour at the positive moment region and to evaluate the code requirements on minimum flexural reinforcement. A criterion was set and evaluations of different minimum reinforcement requirements were made using this criterion and the test data.Key words: beams, crack control, ductility, flexural strength, high strength concrete, minimum flexural reinforcement, reserve strength.
An evaluation ofP-Δ amplification factors in multistorey steel moment resisting frames
Authors: Tremblay R , Côté B , Léger P
Published: April 2011

Three different amplification factors that have been proposed to account for P-Δ effects in the seismic design of multistorey building structures are described and compared. Nonlinear dynamic analyses of a typical 20-storey steel moment resisting frame are carried out under earthquake ground motions typical of eastern and western Canada to evaluate the gravity load effects and to assess the effectiveness of each type of amplification factor in accounting for these effects. All three approaches maintain the ductility demand within the level computed without P-Δ effects, but lateral deformations are generally larger than those obtained neglecting the gravity loads. Nonlinear dynamic analyses are also performed on a shear-beam (stick) model of the same building to examine the possibility of using such simple models for studying the dynamic stability of buildings subjected to ground motions. The shear-beam model does not predict adequately the seismic behaviour of steel moment resisting frames for which P-Δ effects are significant.Key words: ductility, earthquake, ground motion, lateral deformation, moment resisting frame, P-Δ effects, push-over analysis, seismic, shear-beam model, stability coefficient, amplification factor.
Seismic performance of ductile medium height reinforced concrete frame buildings designed in accordance with the provisions of the 1995 National Building Code of Canada
Authors: Heidebrecht A C , Naumoski N
Published: April 2011

This paper describes an investigation into the seismic performance of a six-storey ductile moment-resisting frame structure located in Vancouver and designed and detailed in accordance with the seismic provisions of the National Building Code of Canada (1995). Both pushover and dynamic analyses are conducted using an inelastic model of the structure as designed and detailed. The structural performance of a number of design variations is evaluated using interstorey drift and member curvature ductility response as performance measures. All frames studied are expected to perform at an operational level when subjected to design level seismic excitations and to meet life safe performance criteria at excitations of twice the design level.Key words: seismic, building, frames, ductile, design, performance, reinforced concrete, code.
Optimization of construction time-cost trade-off analysis using genetic algorithms
Authors: Hegazy Tarek
Published: April 2011

In the management of a construction project, the project duration can often be compressed by accelerating some of its activities at an additional expense. This is the so-called time-cost trade-off (TCT) problem, which has been studied extensively in the project management literature. TCT decisions, however, are complex and require planners to select appropriate resources for each project task, including crew size, equipment, methods, and technology. As combinatorial optimization problems, finding optimal decisions is difficult and time consuming considering the number of possible permutations involved. In this paper, a practical model for TCT optimization is developed using the principle of genetic algorithms (GAs). With its robust optimization search, the GAs model minimizes the total project cost as an objective function and accounts for project-specific constraints on time and cost. To maximize its benefits, the model has been implemented as a VBA macro program. This automates TCT analysis and combines it with standard resource-management procedures. Details of the proposed TCT model are described and several experiments conducted to demonstrate its benefits. The developments made in this paper provide guidelines for designing and implementing practical GA applications in the civil engineering domain.Key words: computer application, time-cost trade-off, construction management, genetic algorithms, and optimization.
An approach for auditing highway sections for safety improvements
Authors: Easa Said M , Hassan Yasser , Siczkar Dennis
Published: April 2011

The objective of this paper is to present a framework for the evaluation of traffic safety improvements on rural highways based on the existing process of the Ministry of Transportation of Ontario (MTO). The framework includes four steps to identify hazardous locations and determine the most feasible improvements. The framework was applied to a 2.2 km segment on Highway 17 (Ontario, Canada) to illustrate how the framework might be implemented in practice. The first step is defining the highway section to be studied. This section is usually a segment that was constructed in the same contract, and its surface conditions require major maintenance. The evaluation of traffic safety on sections that are undergoing major pavement rehabilitation will reduce the overall cost of road maintenance. The second step is to collect and analyze collision data, along with traffic and geometric data. The purpose of this step is to compare the actual number of collisions on the section with the expected long-run mean value and identify the causes of collisions. Based on this analysis, the third step identifies the possible improvements that would eliminate or minimize the number of collisions. These improvements can be as simple as signing improvement or as complex as a major realignment. Finally, these improvements are evaluated economically and environmentally. For this study, several sections of the Ministry of Transportation of Ontario, other ministries and levels of government, and interest groups participated in the evaluation process. A refined MTO process, currently being considered for implementation, is briefly described along with a discussion of its key features.Key words: evaluation, highway improvements, safety, three-dimensional alignments, sight distance, collision frequency.
Analysis of frames with non-prismatic members
Authors: Ozay Giray , Topcu Ahmet
Published: April 2011

This paper presents a more realistic and comprehensive static analysis technique for structures having non-prismatic members. In the proposed method a general stiffness matrix for non-prismatic members that is applicable to Timoshenko beam theory has been derived. The stiffness coefficients have been determined for constant, linear, and parabolic height variations of members, employing analytical and (or) numerical integration techniques. Uniform, triangular, and trapezoidal distributed loads over the entire member or along any part of it, concentrated loads, moments at points on the member, and any of these load combinations are taken into consideration to determine the fixed-end forces. A computer program has been coded in Fortran which analyses two-dimensional frames using the proposed stiffness matrix and fixed-end forces for a wide range of external loads. The fixed-end forces may include the effect of shear deformations. The importance of the shear deformations in non-prismatic members with high depth-to-span ratios is shown using numerical examples. The accuracy of the proposed analysis technique is verified by comparing the results of the numerical examples with those obtained from the general analysis program SAP90 using a large number of subelements. Key words: computer programs, fixed-end forces, loads (forces), non-prismatic (tapered), shear deformations, stiffness, structural analysis.
Laboratory experiments with an FM-CW reflectometry system proposed for detecting and monitoring bridge scour in real time
Authors: Yankielun Norbert E , Zabilansky Leonard
Published: April 2011

Thousands of bridges throughout the United States have been identified as being scour critical (i.e., susceptible to failure from pier and (or) abutment scour). Scour occurs during times of rapid river flow when sediments, including rocks, gravel, and silt, are transported by the currents, undermining bridge pier foundations and similar structures. It can be increased by the presence of an ice cover. The scour process is dynamic; erosion and deposition can occur during the same high-energy river event, so the worst-case and the net effect cannot be easily predicted or dynamically monitored using previously available equipment. Herein, a technique and system (U.S. Patent #5,790,471) employing frequency modulated - continuous wave (FM-CW) reflectometry are discussed. This system is proposed for continuous monitoring of the extent of scour around riverine structures. A bench scale version of the system with a 490-MHz linearly swept bandwidth was implemented and tested in the laboratory, where sediments were incrementally added to a water-filled plastic barrel containing an 86-cm-long scour probe. Reflectometer data were taken after each increment of sediment was added. The data indicating the sediment boundary were plotted in a waterfall format that clearly shows the progressive sedimentation. This system has the potential for continuous round-the-clock operation and accuracy to within 5 cm of sediment depth. Key words: reflectometry, real-time monitoring, frequency modulated continuous wave, scour, sediment transport.
The effect of zinc orthophosphate and pH-alkalinity adjustment on metal levels leached into drinking water
Authors: Churchill D M , Mavinic D S , Neden D G , MacQuarrie D M
Published: April 2011

A 12-month pilot plant study was conducted to evaluate a number of corrosion control treatments to reduce metal leaching from typical household plumbing materials. A pipe loop system was used to test six treatment options, with a control loop of the characteristically soft, acidic, Greater Vancouver Water District (GVWD) water. Four pH- alkalinity combinations and two concentrations of zinc orthophosphate (0.37 mg/L and 1.0 mg/L as Zn) were studied. at regular intervals, the flowing, treated, and control waters were allowed to stagnate in the pipe loop system for 8- and 16-h periods. Following the designated standing time, water samples taken from the lead/tin solder jointed, soft copper plumbing coils, the submerged, free standing coils of 50/50 lead/tin solder, and the brass faucets, were measured for lead, copper, and zinc levels. Overall, when compared to the control loop, the pH-alkalinity treatments appeared to exacerbate metal leaching in standing samples. The zinc orthophosphate treated loops were both effective at reducing lead and copper leaching to below control levels. In general, the two standing times showed little difference in the levels of leached metals. The exception to this occurred in the higher dose zinc orthophosphate loop, which had higher copper and zinc levels at the longer standing time. Key words: copper, corrosion, drinking water, lead, zinc orthophosphate.
Canadian ports-external challenges and reform
Authors: Ircha Michael C , Wood Jeff
Published: April 2011

The federal ports system in Canada faces considerable challenges and opportunities from the rapidly changing international trading environment in which they operate. Global trade has grown as a result of tariff reductions and removal of non-tariff barriers emanating from successive rounds of GATT trade discussions. Ports in Canada and the U.S. have been pressured to improve productivity to handle increasing amounts of cargo in a timely manner. Trans-border trade continues to grow due to the FTA and subsequent NAFTA. However, most continental trade is transported by surface mode to the detriment of ports and the coastal trade in both countries. Improvements to transport technology and economic deregulation challenge ports due to the growth of an integrated intermodal system serving a continental transportation network. Such integrated intermodalism enables the diversion of containerized cargo through load-centre ports in both countries. The many challenges facing Canadian ports are partly driving the current port reform process. Steps have been taken over the past several years to involve the Canadian transportation industry in the development of a national marine policy. The Canada Marine Act, which recently was given royal assent, shifts major commercial ports towards a more businesslike setting. However, this may not be enough, as ports need to be freed from the strictures of the federal government to operate independently in a continental competitive transportation environment.Key words: ports, international trade, shipping, technology, deregulation, reform.
Transient bottom topography changes in alluvial streams
Authors: Fares Y R
Published: April 2011

The development of a quasi two-dimensional computational model for simulating the transient variations of bed topography profiles in alluvial river channels is reported. The formulation of the model is based on combining the longitudinal flow momentum with the continuity principle of the sediment bed load. The Engelund-Hansen formula is employed in estimating the total sediment bed load along the reach of a river channel. The lateral bed load contribution from the total load is calculated in the same way as in calculating the lateral secondary currents from the main flow velocities. The numerical scheme and the computational procedure used in the study are described in detail. The simulated bed level profiles are verified through comparisons with experimental and field measurements taken from case studies in the literature for different flow conditions, channel characteristics, and sediment properties. The correlation between flow discharge, bed load, boundary friction, and channel slope is discussed. On the basis of the reasonably good comparisons with field data, it may be deduced that the model can be used for predicting the bottom topography variations in river channels.Key words: meandering rivers, bottom topography, sediment transport, bed load, boundary roughness, field measurements, experimental data, computational modelling, finite difference method.
Alkali-aggregate reactivity in Nova Scotia
Authors: Langley W S
Published: April 2011

Alkali-silica reactivity, a reaction between alkalies usually contained in the cement paste and siliceous aggregates, was positively identified in Nova Scotia in 1962. Powerhouse structures on the Mersey River constructed in 1928-1929 showed intolerable expansion by 1938, and this expansion continues to the present day. Extensive research conducted in the 1960s and 1980s has shown that widespread meta-sediments in Nova Scotia are the principal rock types responsible for the reaction. The rate and extent of reactivity is somewhat dependent on the degree to which the rock has been re-crystallized as a result of contact with intrusive granites. Supplementary cementing materials are effective in reducing or eliminating the excessive expansions caused by the reaction. Class F fly ash has been in general use in Nova Scotia since 1986 and used specifically for reducing alkali-aggregate reactivity since 1990.Key words: alkali-aggregate reaction, expansion, fly ash, meta-sediments, mortar bar test, pozzolans, prism test, quarries, supplementary cementing materials.
Finite element analysis of reinforced concrete columns confined with composite materials
Authors: Parent S , Labossière P
Published: April 2011

The use of composite materials in civil engineering, especially for the strengthening and retrofitting of existing structural elements, is a domain that is growing at a fast pace. The rapid expansion of the structural repair business has already provided numerous opportunities to demonstrate the potential of these materials. However, it has also indicated the need to better understand their properties and the necessity of reliable models to predict the behaviour of repaired structures and the long-term response of those materials considering the effects of freeze and thaw or UV exposure. This article presents a model to predict the ultimate load of a reinforced concrete column confined with composite materials without post-peak response. In addition to the ultimate load, the model identifies the evolution of stresses and strains in the column during the entire loading process. Calculations are made under constant axial and incremental lateral load. The finite element calculations presented here are based on the use of bar elements. These are numerically integrated, considering the appropriate behaviour of the materials in the section of the column. Special attention was paid to the development of a stress-strain relationship representative of the actual behaviour of concrete confined with composite materials.Key words: composite materials, reinforced concrete column, repair, modelling.
Acoustic discharge measurements for the performance testing of low-head hydroelectric turbines under disturbed flow conditions
Authors: Doering John C , Gawne Kevin D
Published: April 2011

Field performance testing of a low-head hydroelectric turbine is essential to evaluate the efficiency and economics of an operation. For low-head hydroelectric turbines, it is difficult to accurately measure the discharge through a unit. Transit-time velocity measurement technology has recently been used to develop, in a laboratory setting, a unique traversing acoustic discharge meter for low-head hydroelectric applications. This technology was recently combined with Gauss-Legendre quadrature integration as an alternative method of measuring the flow through a low-head hydroelectric turbine. However, laboratory testing of this technology has only dealt with undisturbed or ideal flow conditions. Additional physical modeling has been performed to compare the relative accuracy of the continuous traversing acoustic discharge meter with that of a multilevel Gauss-Legendre quadrature integration in disturbed or nonideal flow conditions. The data indicate that while Gauss-Legendre quadrature may provide more accurate estimates in ideal flow conditions, the continuous traversing acoustic discharge meter is better suited to disturbed flow condition because it can better resolve an intricate velocity profile. The accuracy of this instrumentation is sensitive to relatively large scale vorticity rotating in the plane of the acoustic transducers, although accuracies within 2% are still attainable, which is better than the conventional velocity-area method. Key words: acoustic discharge measurement, disturbed flow, turbine, performance testing.
Use of condensed silica fume for making high-strength, self-consolidating concrete
Authors: Kwan A KH
Published: April 2011

A high concrete strength can be achieved by lowering the water/binder ratio and a high workability by adding a higher dosage of superplasticizer. However, a high-performance concrete with both high strength and high workability cannot be produced by just these means because lowering the water/binder ratio leads to lower workability and there is a limit to the increase in workability that can be attained by adding superplasticizer. To produce a high-strength, high-workability concrete, the concrete strength needs to be increased without lowering the water/binder ratio. This can be done by adding condensed silica fume. In this study, a series of trial mixing aimed at developing high-strength, self-consolidating concrete (mean cube strength >80 MPa and needs no compaction for consolidation) was carried out. Several mixes suitable for making such high-performance concrete have been developed and it was found that the addition of condensed silica fume may, under favourable conditions, increase not only the strength but also the workability of the concrete mix. Based on the trial mix results, charts for the design of high-strength, high-workability concrete mixes made of the studied constituents are presented.Key words: condensed silica fume, high-strength concrete, self-consolidating concrete.
Behaviour of reinforced concrete frames rehabilitated with concentric steel bracing
Authors: Abou-Elfath H , Ghobarah A
Published: April 2011

The seismic performance of low-rise nonductile reinforced concrete (RC) buildings rehabilitated using concentric steel bracing is investigated. A three-story building was analysed using various ground motion records. The effectiveness of the steel bracing in rehabilitating the three-story building was examined. The effect of the distribution of the steel bracing along the height of the RC frames on the seismic performance of the rehabilitated building was studied. The behaviour of the nonductile RC frame members is represented using a beam-column element capable of modelling the strength softening and the effects of the axial force on the yield moment and the deformation capacities at peak strength of these members. The performance of the building is evaluated in terms of global and story drifts and damage indices. A simplified approach is proposed for selecting the proper brace distribution.Key words: reinforced concrete, frame, nonductile, rehabilitation, concentric steel brace.
Fibre reinforced polymer reinforcing bars for bridge decks
Authors: Hassan T , Abdelrahman A , Tadros G , Rizkalla S
Published: April 2011

This paper describes the behaviour of two full-scale models of a portion of highway bridge slab reinforced with fibre reinforced polymer (FRP) reinforcement. The first slab was reinforced totally with carbon FRP (CFRP), and the second slab was reinforced with hybrid glass FRP (GFRP) and steel reinforcement. The models were tested under static loading up to failure using a concentrated load acting on each span of the continuous slab and the two cantilevers to simulate the effect of a truck wheel load. Load-deflection behaviour, crack patterns, strain distribution, and failure mode are reported. The measured values are compared to values calculated using nonlinear finite element analysis model. The accuracy of the nonlinear finite element analysis is demonstrated using independent test results conducted by others. The analytical model is used to examine the influence of various parameters, including the type of reinforcement, boundary conditions, and reinforcement ratio. Based on serviceability and ultimate capacity requirements, reinforcement ratios for using CFRP and GFRP reinforcement for typical bridge deck slabs are recommended.Key words: bridges, deflection, FRP, reinforcement, concrete, punching, slabs, shear, finite element model, strain.
Incidence of antibiotic resistance and characterization of plasmids in Campylobacter jejuni strains isolated from clinical sources in Alberta, Canada
Authors: Taylor Diane E. , Chang N. , Garner R. S. , Sherburne R. , Mueller L.
Published: April 2011

Antibiotic susceptibilities of 382 strains of Campylobacter jejuni isolated in Alberta, Canada, in 1980 and 1981 were determined. Although none were resistant to erythromycin or gentamicin, 5.4 and 22% of strains were resistant to ampicillin in 1980 and 1981, respectively. Tetracycline resistance was noted in 6.8% of strains in 1980 and in 8.6% in 1981. Moreover, resistance to high-level tetracycline (32–128 μg/mL) was always mediated by a plasmid of 45–50 kilobases. Three transmissible plasmids from the Alberta strains were compared with the prototype plasmid pMAK175 by restriction enzyme analysis and some minor differences in restriction sites were noted between pMAK175 and pUA183. The two other plasmids pUA142 and pUA143 were 4 kilobases larger than pMAK175 and contained additional restriction sites. However, in all plasmids examined, the HincII and AccI fragments where the tetracycline-resistance determinant was located were shown to be conserved.
Mouse models of infection for Neisseria meningitidis B,2b and Haemophilus influenzae type b diseases
Authors: Brodeur Bernard R. , Tsang Peggy S. , Hamel Josée , Larose Yolande , Montplaisir Serge
Published: April 2011

A disseminated and fatal infection was established in C57BL mice, injected intraperitoneally with either Neisseria meningitidis B,2b or Haemophilus influenzae type b bacteria plus enhancement factors. The effects of mucin, hemoglobin, and iron dextran as enhancement of bacterial infectivity in mice were evaluated individually and in combination. A mixture of mucin and hemoglobin was most effective in enhancing the virulence of the pathogens. Inbred mouse lines were more susceptible than outbred ones. Relative virulence of a number of bacterial strains was also compared in one selected mouse line. Neisseria meningitidis B,2b and Haemophilus influenzae type b strains were more virulent than non-B,2b and nontypable strains. Finally, the course of bacteremia for the two infections in mice was followed by quantitative blood cultures. The animals succumbed to the generalized condition within 72 h. In the case of Neisseria meningitidis B,2b, 10 organisms with 4% mucin and 1.6% hemoglobin were sufficient to kill 50% of the animals. For Haemophilus influenzae type b, 300 bacteria with 5% mucin and 2% hemoglobin were necessary to obtain similar effects.
A method for separating fungal hyphae from soil
Authors: Bingle Wade H. , Paul Eldor A.
Published: April 2011

When fungal hyphae were separated from two mineral soils by wet sieving and density gradient centrifugation, a preparation consisting of 50% of the total soil fungal hyphae and 3% of the soil dry weight was obtained. Residual soil particles were removed by an additional sieving step which resulted in a final recovery of 20% of the fungal hyphae from soil. Scanning electron microscopy revealed that some soil particles still contaminated the hyphae but the exact amount of soil could not be determined by dry weight measurements. These data indicated that reasonable separation of fungal hyphae from soil for use in biomass (i.e., nutrient analysis) studies is feasible.
Susceptibility of Gram-negative bacteria to the synergistic bactericidal action of serum and polymyxin B nonapeptide
Authors: Viljanen Petri , Käyhty Helena , Vaara Martti , Vaara Timo
Published: April 2011

Polymyxin B nonapeptide was able to sensitize Escherichia coli strains and strains of Salmonella typhimurium, Klebsiella spp., Enterobacter cloacae, Pseudomonas aeruginosa, and Haemophilus influenzae to the bactericidal action of fresh normal human serum. The degree of sensitization varied significantly within the strains. Strains of Proteus mirabilis, Neisseria gonorrhoeae, and N. meningitidis remained resistant.
Pseudomonas syringae pv. savastanoi lipopolysaccharide as receptor of a new bacteriophage
Authors: Cañas L. A. , Santaolalla M.
Published: April 2011

A new bacteriophage was found growing on Pseudomonas syringae pv. savastanoi isolates from knots of diseased Spanish olive trees. The bacteriophage had a contractile tail (type A1 of Bradley's classification: Myoviridae) of 60 × 14 nm and an icosahedral head (diameter, 45 nm) which contains DNA. Lipopolysaccharide from the outer membrane of the host bacteria was found to be the specific receptor for the bacteriophage. Phage inactivation was measured as a percentage decrease in plaque-forming units and by electron microscopy. This lipopolysaccharide showed an ultrastructure and chemical composition very similar to those obtained from other Gram-negative pathogenic bacteria. Mild hydrolysis of the lipopolysaccharide with 1% acetic acid liberated the carbohydrate moiety (degraded polysaccharide) from the lipid A. After hydrolysis, monosaccharides and fatty acids were studied by gas–liquid chromatography. The polysaccharide was mainly composed of rhamnose, glucose, and 2-keto-3-deoxyoctulosonic acid; the lipid A contained glucosamine, phosphate, and fatty acids, both hydroxylated (3-OH 10:0, 2-OH 12:0, and 3-OH 12:0) and nonhydroxylated (12:0, 16:1, and 16:0).
Activins and their receptors in female reproduction
Authors: Peng Chun , Mukai Spencer T
Published: April 2011

Activins are growth and differentiation factors belonging to the transforming growth factor-β superfamily. They are dimeric proteins consisting of two inhibin β subunits. The structure of activins is highly conserved during vertebrate evolution. Activins signal through type I and type II receptor proteins, both of which are serine/threonine kinases. Subsequently, downstream signals such as Smad proteins are phosphorylated. Activins and their receptors are present in many tissues of mammals and lower vertebrates where they function as autocrine and (or) paracrine regulators of a variety of physiological processes, including reproduction. In the hypothalamus, activins are thought to stimulate the release of gonadotropin-releasing hormone. In the pituitary, activins increase follicle-stimulating hormone secretion and up-regulate gonadotropin-releasing hormone receptor expression. In the ovaries of vertebrates, activins are expressed predominantly in the follicular layer of the oocyte where they regulate processes such as folliculogenesis, steroid hormone production, and oocyte maturation. During pregnancy, activin-A is also involved in the regulation of placental functions. This review provides a brief overview of activins and their receptors, including their structures, expression, and functions in the female reproductive axis as well as in the placenta. Special effort is made to compare activins and their receptors in different vertebrates.

Key words: activins, activin receptors, reproductive axis, placenta.
Stress-relaxation and contraction of a collagen matrix induces expression of TGF-β and triggers apoptosis in dermal fibroblasts
Authors: Varedi M , Tredget E E , Ghahary A , Scott P G
Published: April 2011

Extracellular matrix serves as a scaffold for cells and can also regulate gene expression and ultimately cell behaviour. In this study, we compared the effects of three forms of type I collagen matrix, which differed only in their mechanical properties, and plastic on the expression of transforming growth factor-β1 (TGF-β1), matrix metalloproteinase-1 (collagenase), and type I collagen and on the growth and survival of human dermal fibroblasts. These effects were correlated with alterations in cell morphology and organization of intracellular actin. Cells in detached or stress-relaxed matrices were spherical, lacked stress fibres, and showed increased TGF-β1 mRNA compared to the cells in anchored collagen matrices or on plastic, which were polygonal or bipolar and formed stress fibres. The levels of TGF-β measured by bioassay were higher in detached and stress-relaxed collagen matrices, than in anchored collagen matrices. Cells on plastic contained little or no immunoreactive TGF-β, while most cells in collagen matrices were stained. The levels of collagenase mRNA were significantly higher in all the collagen matrix cultures compared to those on plastic, but there were no statistically significant differences between them. Levels of mRNA for procollagen type I were not significantly affected by culture in the collagen matrices. Apoptotic fibroblasts were detected by the TUNEL assay in detached (5.7%) and to a lesser extent in stress-relaxed (2.2%) matrices, but none were observed in anchored collagen matrices or on plastic. These results show that alterations in the mechanical properties of matrix can induce the expression of TGF-β and trigger apoptosis in dermal fibroblasts. They further suggest that inability to reorganize this matrix could be responsible for the maintenance of the fibroproliferative phenotype associated with fibroblasts in hypertrophic scarring.

Key words: transforming growth factor-β, apoptosis, fibroblasts.
Reversible changes in size of cell nuclei isolated fromAmoeba proteus: Role of the cytoskeleton
Authors: Pomorski Pawel , Grebecka Lucyna , Grebecki Andrzej , Makuch Robert
Published: April 2011

Micrurgically isolated interphasal nuclei of Amoeba proteus, which preserve F-actin cytoskeletal shells on their surface, shrink after perfusion with imidazole buffer without ATP, and expand to about 200% of their cross-sectional area upon addition of pyrophosphate. These changes in size may be reproduced several times with the same nucleus. The shrunken nuclei are insensitive to the osmotic effects of sugars and distilled water, whereas the expanded ones react only to the distilled water, showing further swelling. The shrinking-expansion cycles are partially inhibited by cytochalasins. They are attributed to the state of actomyosin complex in the perinuclear cytoskeleton, which is supposed to be in the rigor state in the imidazole buffer without ATP, and to dissociate in the presence of pyrophosphate. Inflow of external medium to the nuclei during dissociation of the myosin from the perinuclear F-actin may be due to colloidal osmosis depending on other macromolecular components of the karyoplasm.Key words: Amoeba proteus, isolated nuclei, perinuclear cytoskeleton.
Molecular integration of hypothalamo-pituitary-adrenal axis-related neurohormones on the GnRH neuron
Authors: Tellam David J , Mohammad Yasmin N , Lovejoy David A
Published: April 2011

Gonadotropin-releasing hormone (GnRH) secretion from the hypothalamus is pivotal to the regulation of reproductive physiology in vertebrates. GnRH and the reproductive axis, in general, can be inhibited during periods of stress or injury. Stress, in the form of mechanical, psychological or immunological insult to an organism results in the activation of the hypothalamo-pituitary-adrenal (HPA) axis initiated by the hypothalamic release of corticotropin-releasing factor (CRF). Recent studies indicate that CRF may act either directly on the GnRH neuron to down-regulate GnRH synthesis, or indirectly via a β-endorphin-mediated pathway. Moreover, in vitro studies suggest that CRF-related peptides can increase the sensitivity of the GnRH neuron to prolactin by increasing the synthesis of the prolactin receptor.
Contractile elements of Lemna trisulca L. glycerinated cell models during chloroplast translocations
Authors: Rinaldi Robert A , Kalisz-Nowak Barbara , Korohoda Wlodzimierz , Wieckowski Stanislaw , Kilarski Wincenty , Kozlowska Maria
Published: April 2011

Electron microscopy of Lemna glycerinated cell models depicts contractile elements during chloroplast translocations. One contractile element, the thin ectoplasmic layer, is [Formula: see text] 0.4 µm thick, pressed against plasma membrane-cell wall. Thin ectoplasmic layer contains numerous oriented filaments and some appear to be actin and myosin. Another contractile element is the outer chloroplast membrane which envelops each chloroplast and joins or fuses with the thin ectoplasmic layer. Choroplast interconnections are formed between two or more chloroplasts by outer chloroplast membranes; they enhance chloroplast communications, translocations, and molecular exchanges.Key words: chloroplast translocations, contractility, tubular connections.
Neurons from stem cells: Implications for understanding nervous system development and repair
Authors: Mansergh Fiona C , Wride Michael A , Rancourt Derrick E
Published: April 2011

Neurodegenerative diseases cost the economies of the developed world billions of dollars per annum. Given ageing population profiles and the increasing extent of this problem, there has been a surge of interest in neural stem cells and in neural differentiation protocols that yield neural cells for therapeutic transplantation. Due to the oncogenic potential of stem cells a better characterisation of neural differentiation, including the identification of new neurotrophic factors, is required. Stem cell cultures undergoing synchronous in vitro neural differentiation provide a valuable resource for gene discovery. Novel tools such as microarrays promise to yield information regarding gene expression in stem cells. With the completion of the yeast, C. elegans, Drosophila, human, and mouse genome projects, the functional characterisation of genes using genetic and bioinformatic tools will aid in the identification of important regulators of neural differentiation.Key words: neural differentiation, neural precursor cell, brain repair, central nervous system repair, CNS.
Semaphorin function in the developing invertebrate peripheral nervous system
Authors: Bonner Jennifer , O'Connor Timothy P
Published: April 2011

Different members of the semaphorin family of secreted and transmembrane guidance molecules play important and diverse roles during neuronal development. Within the developing grasshopper limb bud, two semaphorins are expressed in relatively non-overlapping and distinct expression patterns. The establishment of the tibial sensory projection within the limb bud relies on the combinatorial action of both semaphorins. In this review, we describe the function of the two semaphorins in axonal guidance and propose that a hierarchy of cues guide sensory neurons in the developing peripheral nervous system.Key words: semaphorin, axon guidance, grasshopper, peripheral nervous system, review.
Cellular mechanisms of netrin function: Long-range and short-range actions
Authors: Kennedy Timothy E
Published: April 2011

Netrins are secreted proteins that direct axon extension and cell migration during neural development. They are bifunctional cues that act as an attractant for some cell types and as a repellent for others. Several lines of evidence suggest that two classes of receptors, the deleted in colorectal cancer (DCC) family and the UNC-5 family, mediate the attractant and repellent response to netrin. Although netrins were first identified as diffusible long-range cues for developing axons, recent findings provide evidence that they also function as short-range cues close to the surface of the cells that produce them. This short-range function of netrin contributes to guiding neurite outgrowth and mediating cell-cell interactions during development and perhaps also in adults.
The chickenstathmingene and its expression in the embryo
Authors: Soodeen-Karamath Sharon , Verrinder Gibbins Ann M
Published: April 2011

Stathmin, which functions as an intracellular relay in signal transduction pathways, has been suggested as a potential indicator of pluripotent cells in the early mouse embryo. In this study, chicken stathmin cDNA and genomic DNA were analyzed. In mammals stathmin consists of five exons and four introns; exons 3, 4, and 5 in the mammalian stathmin gene are equivalent to one relatively large exon in the chicken stathmin gene. Introns equivalent to introns 3 and 4 in the mammalian stathmin gene are not present in the counterpart gene in chickens and, although intron 2 was shown to be present in both mammals and birds, it is smaller in the chicken stathmin gene. Despite differences in the genomic organization of the gene and its smaller size in chickens compared with that in humans and mice, similarities in the coding sequences and in the expression of the chicken and mouse stathmin genes at certain stages of embryo development, as determined by whole-mount in situ hybridization experiments, suggest that their products are functional homologues. The argument is thus substantiated for further investigations into the use of regulatory regions of the stathmin gene in a system for the establishment of long-term cultures of germline competent chicken embryonic stem (ES) cells by the selective ablation of differentiated cells in culture using drug selection.Key words: stathmin, chicken, ES cells, oct 3/4.
Xenopus adenine nucleotide translocase mRNA exhibits specific and dynamic patterns of expression during development
Authors: Crawford Michael J , KhosrowShahian Farhad , Liversage Richard A , Varmuza Susannah L
Published: April 2011

We report the isolation and characterization of the Xenopus homolog to human T1 ANT (adenine nucleotide translocase). The 1290-nucleotide sequence contains initiation and termination signals, and encodes a conceptual protein of 298 amino acids. The sequence shares high amino acid identity with the mammalian adenine translocases. The transcript is present in unfertilized eggs, and it is expressed at higher levels during formation of the antero-posterior dorsal axis in embryos. Although low levels are expressed constitutively except in endodermal cells, adenine nucleotide translocase (ANT) expression is dynamically regulated during neurulation. At this stage, expression in ectoderm rapidly diminishes as the neural folds form, and then ANT expression increases slightly in mesoderm. At the culmination of neurulation, the neural tube briefly expresses ANT, and thereafter its expression predominates in the somitic mesoderm and also the chordoneural hinge. In addition, ANT expression is particularly high in the prosencephalon, the mesencephalon, the branchial arches, eye, and the otic vesicle. Treatment of embryos with retinoic acid has the effect of diminishing constitutive expression of ANT, but microinjection studies demonstrate that immediate and local repression cannot be induced in dorsal structures.Key words: adenine nucleotide translocase, Xenopus, retinoic acid, pattern formation, gastrulation.