bluuebunny/crossref_metadata_2025 huggingface dataset:
Developing a traversing acoustic discharge measurement technique for the performance testing of low-head hydroelectric turbines
Authors: Doering John C , Gawne Kevin D
Published: April 2011

The efficient operation of a hydroelectric generating plant requires an accurate definition of the performance relationships for each turbine-generator unit. Of the information obtained during performance testing, discharge is the most difficult to measure accurately. Acoustic transit-time velocity measurement technology is applied herein to obtain more accurate discharge measurements than current velocity - area method practices. The technique proposed involves continuously traversing a number of acoustic paths, each providing a chordal average velocity measurement, across the turbine intake to obtain a complete integration of the complex velocity profile typical of low-head hydroelectric plants. Data from hydraulic laboratory testing of a single acoustic cell were compared with known flow rates to assess the accuracy and repeatability of the proposed discharge measurement technique. A range of continuous traverse rates was evaluated. The results indicate that the proposed continuous traversing acoustic discharge meter (TADM) can provide efficient, accurate (1-2% error), and repeatable discharge measurements.Key words: turbine, performance testing, acoustic discharge measurement, traversing.
Nonlinear seismic response predictions of walls coupled with steel and concrete beams
Authors: Harries Kent A , Mitchell Denis , Redwood Richard G , Cook William D
Published: April 2011

The design and nonlinear dynamic analyses of four coupled wall prototype structures are presented. Two ductile partially coupled and two ductile coupled wall structures are considered, each having reinforced concrete and steel coupling beams. The design of each of the prototype structures was based on the provisions of the 1995 National Building Code of Canada. Nonlinear dynamic analyses of each structure, using four different scaled earthquake ground motions are presented and the results discussed. Comparisons of the responses of the structures with concrete and steel coupling beams are made, demonstrating the advantages of using steel beams to couple reinforced concrete walls.Key words: composite construction, coupled wall, diagonally reinforced concrete coupling beam, "flexure critical" steel coupling beam, seismic design, "shear critical" steel coupling beam.
Sault Ste. Marie Lock reconstruction: hydraulic model studies of the stop log emergency closure and lock filling and emptying systems
Authors: Holder Graham K
Published: April 2011

In July 1987, a section of the southwest wall of Sault Ste. Marie Lock failed during a locking operation when a portion of limestone facing, 60 m by 8 m, separated from the rubble backing wall. Engineering investigations resulted in the selection of the Recreational Lock Option, involving either downsizing the lock chamber within the existing lock or constructing a new lock as the most viable solutions. A Dry Dock Option, where the lock would be used to store craft during the winter months, was also considered. However, this option was abandoned during the course of testing. The engineering investigations also revealed that the emergency swing dam, constructed upstream of the existing lock to protect the system should the lock gates be damaged or carried away (as happened in 1909), was in poor condition and required rehabilitation in the order of over $0.5 million. A stop log emergency system was proposed as an alternative safety device designed to stop the flow of water through the canal in the event of gate failure. Physical hydraulic model studies were carried out to evaluate the feasibility of using an emergency stop log system. The tests showed that stop logs constructed with solid horizontal web plates top and bottom result in unacceptably high hydraulic downpull forces. Open truss stop logs can be deployed to stop the flow of water through the canal in the event of gate failure. The follower should also be constructed as an open truss such that the areas of steel exposed to the flow at the top and bottom of the follower are minimized. Hydraulic uplift forces that could prevent closure can be reduced by increasing the space between the stop log and the follower. Physical hydraulic model studies of the lock filling-emptying systems are described. The first and preferred option consists of downsizing the existing lock and retaining part of the existing wooden culverts and emptying system, if possible. A new filling port, filling valves, and supply culvert would be constructed upstream. In the event that the existing wooden culverts are found to be unserviceable, a second option was considered. This second option would be to fill in the wooden culverts and then construct a new filling port, filling valves, and supply culvert that would discharge into the lock through the upstream breast wall just above floor level. The existing emptying system would be retained or rebuilt. The third option, if both the filling and discharge culverts have to be condemned, would be to build a new lock. The results of the hydraulic model studies carried out to explore these three options are described.Key words: emergency closure, stop logs, follower, canal, lock, downpull, uplift, crane capacity, filling-emptying system, culverts.
Un simulateur d'écoulement en temps réel comme aide à la prévision et à la gestion des rivières
Authors: Lavallée Daniel , Marche Claude , Therrien Francis
Published: April 2011

The development of watersheds complicates the management of hydraulic facilities. Managers are facing economic and social imperatives that are potentially conflicting. Generally, their decisions are based on operational rules established by experience. However, these rules do not ensure that certain minimal conditions be respected and they do not determine future conditions for the river as a whole. Therefore, the communication of these conditions between managers of a same river is difficult. The present paper provides an approach to improve this situation. The real time simulator XSIM, with a graphical interface, has been developed in order to assist managers in control, design, analysis, and information transmission. It is designed based on an intumescence model functioning in an unsteady flow regime. It allows the managers to input the considered operations and provides them with the design conditions in a format adapted to their needs. It ensures the distribution and the availability of the results by creating a web page automatically. Its application to the management of complex sections of a real river is presented in order to illustrate its usefulness for day-to-day management and in emergency situations, such as a sudden flood or the rupture of a dam.Key words: flood, decision aid, management, unsteady flow regime, hydrology, graphical interface, numerical simulation.
Modélisation de la résonance dans les bassins portuaires
Authors: Ouellet Yvon , Siles Jimmy
Published: April 2011

Two numerical models have been developed to evaluate the resonance within harbours of variable depth. The first model determines the eigenvalues of a system, corresponding to the natural mode of vibration of the water body within the harbour. Although the model produced interesting frequency values for completely open harbours, the computed values exhibited discrepancies of about 15% compared with measured frequencies. Moreover, the model is limited by the fact that an artificial nodal line must be set at the mouth of the harbour and that the amplification factor cannot be interpreted without the prior knowledge of the wave amplitude affecting the water body. Hence, the model ignores influences from the water body outside the harbour, which can be considered as infinite. The second model uses the method of finite boundary elements and introduces radiation terms to account for the infinite water body outside the harbour. This model yielded good results compared with the exact solution and the laboratory measurements by Yoshida and Ijima (1983), who studied the behaviour of an open harbour with variable depth. Differences of up to 12% were observed for the amplification factor around certain frequencies close to the second vibration mode. A comparison with field spectral density measurements from Sainte-Thérèse-de-Gaspé shows a good agreement between the modelled results and the vibratory behaviour of this harbour, thus supporting the use of this model for case studies. Nonlinear terms, along with flow friction and separation effects near the inside edges of the mouth of the harbour, may also be included within the model.Key words: resonance, waves, finite elements, finite boundary elements.[Journal translation]
Uplift on rooftop walkways and cable trays
Authors: Mattacchione Angelo , Mattacchione Livia
Published: April 2011

A code review is presented, along with current state-of-knowledge and in situ observations, in order to gain a better understanding of the effect of wind-induced uplift on timber walkways and metal cable trays located on rooftops.Key words: wind uplift, pavers, small structural elements, timber walkways, metal cable trays, pressure equalization.
Residence time distribution analysis as related to the effective contact time
Authors: Liem L E , Stanley S J , Smith Daniel W
Published: April 2011

Sixteen full-scale tracer studies were completed at two water treatment plants to assess disinfection performance under the concentration-time (CT) concept. The step residence time distribution (F RTD) was developed for each case. The value of the effective contact time, t10, in the CT concept was then obtained. For reservoirs without baffles, the t10 values were found to be much smaller than the expected values, indicating poor performance under the CT concept. Several models were used to interpret the F RTD characteristics, but the results were unsatisfactory. The standard jet model was then applied and was able to match the field data F RTD curve up to the relative concentration c/co [Formula: see text] 0.2. This showed that the momentum causing jet was responsible for the rapid movement of water through the system causing small t10 values. The work shows the importance of the momentum causing jet in reservoirs, and that in addition to traditional criteria it should be considered in the evaluation of water treatment component design. Other models that are commonly used to predict the t10 value should be applied carefully as a result of this jet effect.Key words: tracer study, F RTD, t10, CT concept, jet, water treatment component design.
Variability of traffic-flow measures across freeway lanes
Authors: Carter Mark , Rakha Hesham , Aerde Michel Van
Published: April 2011

On most freeways, a number of factors interact to produce lane-to-lane variations in speed and volume which are both site and volume dependent. The following paper explores and statistically verifies these variations using detector data and a combination of complementary techniques based on data collected for 30 days at 27 detector stations in May 1994 along the Queen Elizabeth Way freeway near Toronto, Ontario. The analysis indicates that considerable volume dependencies exist at each site, and that these dependencies are site specific. In addition to their independent variations, speed and flow are also shown to interact differently across different lanes and result in different underlying speed-flow relationships. The findings are intended to be relevant to the calibration of microscopic traffic simulation models and automatic incident detection algorithms. As such, the paper does not attempt to specifically identify the underlying causes for the variations, but rather attempts to recognize the aggregated effects of these causes in a fashion that would be useful to real-time freeway traffic management system control strategies relying solely on loop detector inputs.Key words: traffic-flow theory, traffic modeling, traffic simulation, incident-detection algorithms.
Carbon fibre reinforced polymer (CFRP) post-tensioned masonry diaphragm walls: prestressing, behaviour, and design recommendations
Authors: Sayed-Ahmed Ezzeldin Y , Lissel Shelley L , Tadros Gamil , Shrive Nigel G
Published: April 2011

The use of post-tensioned masonry can lead to economic and elegant structures. A major problem associated with post-tensioning is the corrosion of the steel tendons, especially for unbonded tendons. If carbon fibre reinforced polymer (CFRP) tendons could be used to replace the traditional steel tendons, the corrosion problem would be overcome. However, a number of issues need to be resolved before CFRP tendons can be used comfortably in post-tensioning applications. The first part of this paper deals with a diaphragm wall post-tensioned using CFRP tendons. The post-tensioning procedures are described and the prestress losses occurring in the past 12 months are presented. Results from thermal, flexure, and racking shear tests performed on the wall are reported. The second part of the paper deals with the development of design procedures and equations based on both the test results and the database currently available. The equations presented are specifically for CFRP unbonded post-tensioned masonry diaphragm walls but with appropriate modification could be applied to the design of any CFRP post-tensioned masonry wall. A design example is included.Key words: anchorage system, carbon fibre reinforced polymers, diaphragm walls, flexural strength, masonry walls, prestress losses, prestressed masonry, post-tensioning, shear strength, thermal loads.
Capacity and performance of roundabouts
Authors: Al-Masaeid Hashem R
Published: April 2011

Empirical and theoretical approaches for assessing the capacity and performance of roundabout entries have provided inconsistent results. It was believed that an efficient modeling of gap-acceptance behavior of drivers entering into a roundabout would provide more insight for assessing roundabout operation. Accordingly, this study used logit modeling to predict the probability that a randomly selected driver will accept a given gap in the circulating traffic stream based upon roundabout and gap characteristics. Also, the study has developed move-up time models using both the roundabout geometry and circulating traffic characteristics. The developed gap-acceptance and move-up time models have implications in roundabout capacity estimation analysis. Finally, the results of the developed models are incorporated into the Australian and German gap theoretical models to judge the feasibility of using these theoretical models for Jordan conditions. Compared with an empirical data set, the Australian theoretical model with a minimum headway of 0.5 s provides reasonable results.Key words: capacity analysis, probabilistic approach, roundabouts.
On the use of steel-free concrete bridge decks in continuous span bridges
Authors: Mufti A A , Newhook J P
Published: April 2011

This note discusses the use of the steel-free concrete bridge deck technology in continuous span bridge structures. Conventional slab-on-girder design often utilizes the longitudinal steel reinforcement in the deck to resist the negative bending moments created at the internal piers of continuous bridges. The steel-free bridge deck is devoid of all internal steel reinforcement and hence requires an alternate design approach which is presented in this note. A key aspect of this approach is the recommended use of fibre-reinforced polymer reinforcement to control cracking of the deck over the intermediate supports. Limiting these crack widths is essential to the durability performance of the concrete, particularly in freeze-thaw environments. The results of an experimental program are also reviewed. The tensile stresses from the global longitudinal negative moment are shown to have little effect on the punching behaviour of the slab. It is noted that the concepts presented in this note were utilized in the construction of a three-span highway bridge which incorporated the steel-free bridge deck technology.Key words: bridges, design, continuous span, concrete decks, punching-shear, fibre-reinforced polymers.
A simulation approach for examining capacity and operational performance at freeway diverge areas
Authors: Al-Kaisy A , Stewart J A , Aerde M Van
Published: April 2011

Freeway diverge areas, and particularly those in the proximity of exit ramps, are often viewed as potential bottlenecks in freeway operations. The existing diverge procedures within the 1994 and 1997 Highway Capacity Manual updates are limited in that they do not provide a direct estimate of freeway capacity nor do they model performance at oversaturated traffic conditions. Moreover, a parallel investigation on these procedures revealed some inconsistencies in predicting measures of performance at those critical areas. This paper describes the use of computer traffic simulation to explore the patterns of capacity and operational performance behaviour at these areas under the impact of some key geometric and traffic variables. For this purpose, the microscopic traffic simulation model INTEGRATION was selected to conduct an extensive experimental work on a typical ramp-freeway diverge section. Five control variables were investigated, namely, total upstream demand, off-ramp demand, length of deceleration lane, off-ramp free-flow speed, and number of lanes at mainline. The impact of upstream or downstream ramps is considered beyond the scope of this research. Except for off-ramp free-flow speed, the impact of other control variables on capacity and operational performance was shown to be significant. Also, the simulated trends of traffic behaviour showed considerable agreement with logic and expectations in light of the current state of knowledge on freeway operations.Key words: freeways, diverge, capacity, operations, traffic simulation.
Influence of corrosion on prestress strands
Authors: Lopes SMR , Simões L MLP
Published: April 2011

Corrosion on prestress strands affects their mechanical properties as well as the coefficient of friction in the surface strand/duct. In previous research on prestress beams, the authors have observed different coefficients of friction depending on the surface condition of the strands and wires used in investigation. Some of the strands used for the experiments were stored for some months in the laboratory and gained some rust on the surface. This was enough to influence the coefficient of friction in a noticeable manner. To study the influence of corrosion on the mechanical properties of prestress strands several samples were stored under different environmental conditions to produce various levels of corrosion. These samples were tested afterwards to determine the influence of corrosion on fatigue properties and the coefficient of friction. Apart from the coefficient of friction, light rust decreases none of the other studied mechanical properties of the strands and may even increase the bond characteristics. The presence of rust does not necessarily mean that the strands should be rejected. The work described in this paper was conducted to investigate the level of rust that could be considered acceptable and how corrosion influences some mechanical properties of prestressing strands.Key words: reinforced concrete, prestressed concrete, prestressed beams and girders, structural design, structural members, corrosion, fatigue, losses.
Application of uniform hazard spectra in seismic design of multistorey buildings
Authors: Humar J L , Rahgozar M A
Published: April 2011

The use of uniform hazard spectra for obtaining the seismic design forces is being considered for the next version of the National Building Code of Canada. Such spectra provide the spectral accelerations of a single-degree-of-freedom system for a range of periods but for a uniform level of hazard. One of the issues that need to be resolved before uniform hazard spectra are used in the design of multistorey buildings is the adjustment required in the base shear to account for the higher mode effects present in a multi-degree-of-freedom system. This issue is examined through analytical studies of the response of idealised elastic and inelastic multistorey building frames to ground motions representative of the seismic hazard in the eastern and western regions of Canada. Representative values are obtained for the adjustment factors that must be applied to the design base shear and to the base overturning moment.Key words: seismic design base shear, uniform hazard spectra, higher mode effects, base shear adjustment factor, base overturning moment reduction factor.
Correlation between measurement of an ice detector and the mass of ice accreted on two different sized conductors
Authors: Druez J , McComber P , Farzaneh M
Published: April 2011

In cold regions, atmospheric icing is an important parameter for the design and reliability of exposed structures. A test site, located on Mt. Valin (Québec) Canada, is used to obtain field data on icing events. This test site mainly includes two test lines supporting four types of electrical conductors, instrumentation, and an ice detector. The ice detector monitors ice accretion by measuring the shift in frequency, at resonance, of a vibrating cylindrical probe, under the effect of the mass of ice accreted. This instrument, which is electrically de-iced, sends a cumulative alarm signal for each ice mass accretion reaching a preset value. The correlation between the ice detector signal and the mass of ice accreted on two different sized conductors is presented for three typical icing events monitored during the 1994-1995 season. In order to improve the correlation, a procedure rejects the data points corresponding to the shedding of ice during an icing event. The comparison between the mass of ice accreted on different conductors and the ice detector signal is a convenient way to calibrate the instrument. Then, these results could be used for predicting the ice mass accreted on similar cables, using the number of alarm signals from the ice detector. Results indicate the need to take into consideration the cable diameter and the apparent area of the probe with respect to the direction of droplets in the calibration of such ice detector.Key words: ice accretion, ice detector, electrical conductor, correlation, calibration, icing model, ice prediction, in-cloud icing, precipitation icing.
The benefits of computerized real-time river basin management in the Malahayu reservoir system
Authors: Ilich Nesa , Simonovic Slobodan P , Amron Mochtar
Published: April 2011

This paper describes the developments of operating rules for the Malahayu reservoir system in Indonesia. The analysis in this study is based on the use of a simulation model with a nested network flow optimization subprogram, which required hydrologic time series of reservoir inflows as input data. Since estimates of historic naturalized flows were of insufficient length, they were used as a basis for developing a 100-year stochastic series which offered a more challenging input while preserving the relevant statistics of the original historic series. This study shows by how much the reservoir yield could have been increased in the past, assuming that short-term inflow and demand forecasts are available and that the proposed reservoir operating rule is obeyed. The increase is estimated by comparing the long- term average of the simulated diversions at the three weirs with the actual historic diversions which are on the record. A more efficient reservoir operating policy would increase the reservoir yield by 38% in the March-June period and by 33% in the July-October period. If additional local runoff into the weirs is utilized in the same period, the increased supply would range up to 66% in the March-June period and 43% in the July-October period. The results from this study provide a strong argument in favour of investing in modern technology as opposed to massive additional infrastructure development. Key words: linear programming, reservoir rule curve, simulation, optimization, stochastic inflow series.
Assessment of time-dependent reliability of reinforced concrete columns with uncertain load eccentricity
Authors: Hong H P , Zhou W
Published: April 2011

An approach for the time-dependent reliability analysis of reinforced concrete (RC) columns considering the correlation between the axial load and the bending moment or the uncertainty in the load eccentricity is presented. The approach recursively uses the efficient first-order reliability method for the time-dependent reliability analysis. The proposed approach is more efficient than the ones used in the literature for the reliability analysis of RC columns. The proposed approach is used to carry out sensitivity analyses of the reliability of short RC columns to the time-dependent live load effects and to the correlation between the axial load and the bending moment. Results of the analyses suggest that the reliability of RC columns can be sensitive to the correlation between the axial load and the bending moment due to live load. The differences between the reliability indices obtained by considering the live load modeled as a pulse process and as an extreme variate can be large.Key words: reliability, load, time-dependent, time-independent, uncertainty, correlation, concrete, reinforcement, column.
The effect of tailwater depth on the dynamics of local scour
Authors: Balachandar R , Kells J A , Thiessen R J
Published: April 2011

The two-dimensional local scour occurring downstream from a submerged sluice gate for various tailwater depths was studied using a video imaging technique and a laser-Doppler anemometer. The flow field was found to be dynamic (i.e., varied with time). Previously reported equilibrium scour profiles for similar test conditions were not attained even after 96 h of laboratory testing. The scaling laws suggested in the literature were found to be unsuitable. New scaling laws are presented for the condition when a stable equilibrium state has not yet been attained. Velocity profiles are presented at various stations during digging and refilling conditions. Key words: local scour, time scale, video imaging, scour profile, velocity profile, sluice gate, cohesionless material, tailwater effect.
Reinforced concrete slab-column edge connections with shear studs
Authors: El-Salakawy Ehab F , Polak Maria Anna , Soliman Monir H
Published: April 2011

The paper reports the results of an experimental investigation on the influence of shear studs on the behaviour of reinforced concrete slab-column edge connections with openings. The test parameters were the location of openings around the column, the size of openings, and the existence of shear reinforcement. The objective of the paper is to present and discuss the results of large-scale tests on slabs with shear stud reinforcement and compare these test results with those of tests on identical slabs but without shear reinforcement. All tested slabs contained same amounts of typical flexural reinforcement (ACI 318-95 and CSA A23.3-94). The presented test results can be used for studying the behaviour of slab-column connections and for calibration of the predictive models.Key words: reinforced concrete, edge connections, flat concrete plates, punching shear, shear strength, openings, failure, shear studs, shear reinforcement.
Alkali-aggregate research in New Brunswick
Authors: DeMerchant D P , Fournier B , Strang F
Published: April 2011

New Brunswick is located within the northeast-southwest trending Appalachian Region. The basement rocks consist largely of metamorphosed sedimentary types with some granitic intrusions and the composition of the natural gravels reflects the bedrock types. Research into alkali-aggregate reaction (AAR) problems in the province was sponsored initially solely by CANMET and more recently in association with the Department of Transportation. The research consisted of (i) petrographic studies of aggregates, (ii) petrographic studies and case histories of existing concrete structures, and (iii) laboratory expansion testing of concrete and mortar bar specimens. Alkali-aggregate reaction has been found to be one of the factors responsible for premature concrete deterioration in New Brunswick. Visual signs of Alkali-aggregate reaction require up to 10 years to appear and the reaction takes up to 30 years to fully develop. Principal reactive rock types are greywacke, argillites, and fine-grained volcanic rocks. The reactive component is thought to be fine-grained quartz less than 100 µm in size. Laboratory expansion test results on concrete specimens are sensitive to alkali levels. Concrete prism tests (CSA A23.2-14A) with 5.5-5.4 kg/m3 Na2O equivalent have been used to predict aggregate performance. By comparison the water soluble alkali contents of field concretes constructed since about 1970 have been found to range from 3.5 to 5 kg/m3 Na2O equivalent. Accelerated mortar bar expansion test results (CSA A23.2-25A) do not correlate well with concrete prism expansion tests and indicate a much higher percentage of deleterious aggregates. Use of supplementary cementing materials such as fly ash and silica fume have been found to be effective in long duration laboratory tests to control aggregate reactions.Key words: concrete, aggregates, alkali-aggregate reaction, standard and accelerated testing for AAR, fly ash, silica fume.
Cyclic loading of end plate moment connections
Authors: Adey B T , Grondin G Y , Cheng J JR
Published: April 2011

An experimental investigation of 15 cyclically loaded extended end plate connections was undertaken to assess the significance of some design parameters. The parameters investigated were beam size, bolt layout, end plate thickness, use of extension stiffeners, welding process, and weld preparation. Eleven of the 15 full-scale test specimens were designed to confine failure to the end plate and four were designed to develop the plastic moment capacity of the beam. Of the beam sizes tested (W360×51, W460×97, and W610×125) the W460×97 beam connections provided the most ductility. The relaxed bolt configuration provided more energy dissipation and connection ductility. The use of extension stiffeners improved the ability of the end plates to dissipate energy and increased the connection rotation at yield. An increase in end plate thickness results in an increase in the connection flexural strength. No significant difference in behaviour was observed between the connections fabricated using the shielded metal arc welding process and those fabricated using the flux-cored arc welding process. Bolt bending and loss of preload were observed in all the test specimens. End plate thickness prediction equations proposed by various researchers were evaluated by comparing predicted plate thickness with plate thickness used for the test specimens. New prediction equations that use yield lines in close agreement with those observed in the test specimens are proposed. The proposed prediction equations are able to predict the thickness of the end plate to within 13%. The proposed prediction equations are applicable to stiffened and unstiffened end plate moment connections with various bolt layouts. Extended end plate moment connections showed good potential for use in seismic zones.Key words: cyclic loading, energy absorption, extended end plates, moment connections, steel, yield line.
Finite element analysis of buckling of corroded ship plates
Authors: Slater P A , Pandey M D , Sherbourne A N
Published: April 2011

The paper is concerned with the assessment of ship plates in which corrosion has reduced their overall thickness making them vulnerable to buckling-related failures. The uniaxial buckling of simply supported square plates is studied for several corrosion patterns, which are allowed to progressively engulf the entire plate. The finite element method is employed for computing buckling loads of corroded plates with different boundary conditions. Numerical results are presented in the form of generic plots of buckling load versus volumetric metal loss for several corrosion patterns considered in the paper. The mechanics of buckling load variations by corrosion is discussed in detail. The spatial location of the corrosion patch appears to have a significant effect on the buckling strength. It is noted that the case of uniform corrosion is not the most detrimental case, rather corrosion confined in a corner or central area appears to be more critical.Key words: ship structures, square plate, buckling load, corrosion, uniaxial compression, finite element method.
Wood fibre - cement composites by extrusion
Authors: Shao Yixin , Moras Shylesh , Ulkem Nilgun , Kubes George
Published: April 2011

Wood fibres derived from both hardwood and softwood, being relatively inexpensive and in ample supply, have gained increasing popularity in the fibre-cement building product industry. Presently, the manufacture of most wood fibre - cement composites employs the Hatschek process. The purpose of this paper is to examine the feasibility of using extrusion technology for the production. Wood fibre - cement sheets, composed of both hardwood and softwood fibres of different fibre contents, were fabricated using an auger-type extruder. The flexural behavior, moisture content, water absorption, and density of all batches were evaluated. To investigate the weathering durability of the extruded composites, materials were also subjected to a temperature-cycling test and a natural exposure weathering test. With a relative ease of manufacture and a much cleaner production, extrusion was found to be a suitable means for making cement composite thin sheets with up to 8% fibres by weight. The extruded composites exhibited a performance comparable to or even better than that of the Hatschek products. Hardwood fibres, which are cheaper and more available than the softwood fibres, were found to be more suitable for extrusion production in terms of the extrudability, finished surface, and long-term mechanical properties.Key words: wood fibre - cement composites, hardwood pulp, softwood pulp, extrusion, strength, toughness index, temperature cycling, natural weathering.
Experimental investigation of the role of reinforcement in the strength of concrete deck slabs
Authors: Khanna O Shervan , Mufti Aftab A , Bakht Baidar
Published: April 2011

To study systematically the role of each layer of steel reinforcement in conventionally reinforced deck slabs of girder bridges, a full-scale model was built of a 175 mm thick concrete deck slab on two steel girders with a center-to-center spacing of 2.0 m. The 12 m long deck slab was conceptually divided into four 3 m long segments, identified as segments A, B, C, and D. Segment A contained isotropic steel reinforcement in two layers, conforming to the requirements of the Ontario Highway Bridge Design Code (OHBDC). Segment B contained only the bottom layer of steel reinforcement. Segment C contained only the bottom transverse steel bars. Segment D contained only bottom transverse glass fibre reinforced polymer (GFRP) bars having the same axial stiffness, but 8.6 times the axial tensile strength, as those of the steel bars in segment C. Each segment of the deck slab was tested to failure under a central concentrated load, simulating the dual tire footprint of 250 × 500 mm dimension of a typical commercial vehicle. All segments failed in the punching shear mode. The failure loads for the four segments were found to be 808, 792, 882, and 756 kN, respectively; these failure loads are similar in magnitude to that of a 175 mm thick steel-free deck slab with steel straps having nearly the same cross-sectional area per metre length of the slab as those of the bottom transverse steel bars in the first three segments. The tests on the four segments of the full-scale model have confirmed that (i) only the bottom transverse reinforcement influences the load carrying capacity of a reinforced concrete deck slab and (ii) the stiffness of the bottom transverse reinforcement, rather than its strength, is of paramount importance.Key words: arching, deck slab, FRP, shake down, slab-on-girder bridge.
Pathways of glucose catabolism in the smut fungus Ustilago violacea
Authors: Held Gary , Goldman Manuel
Published: April 2011

The pathways of glucose catabolism were examined in haploid and diploid strains of the smut fungus Ustilago violacea. Radiorespirometric studies indicated that both of the haploid mating types and diploid strains of this basidiomycete catabolized glucose through the Embden–Meyerhof and hexose monophosphate shunt pathways. The Entner–Doudoroff pathway was not utilized by any of the strains examined. Radiorespirometric data also suggested functioning of an active tricarboxylic acid cycle. In vitro enzyme assays established the presence in this organism of all the enzymes integral to the operative pathways plus the presence of the enzymes of the glyoxylate cycle. Enzyme activities specific to the Entner–Doudoroff pathway were not detected. No major differences in the routes of glucose dissimilation were found between the two haploid mating types or between haploid and diploid forms of this organism.
Site-specific independent double labeling of proteins with reporter atoms
Authors: Wallace Carmichael JA , Clark-Lewis Ian
Published: April 2011

Many types of physical, spectroscopic, and biological studies of proteins and other macromolecules are facilitated by the incorporation of reporter groups. In many cases these are single atom substitutes, for example isotopes (13C for C), or light (F for H) and heavy (Se for S) atom homologs. In some circumstances the incorporation of two different labels in the same molecule would be greatly desirable. Commonly used protein engineering methods for incorporating them can rarely cope with differential double labeling, and have other limitations such as universal, non-specific, or random incorporation. Although de novo peptide synthesis has the power to achieve highly specific labeling, the difficulties inherent in creating long sequences lead us to propose protein semisynthesis as the most practical approach. By ligating combinations of natural and labeled synthetic fragments to reform holoproteins, we can overcome any of the limitations discussed. Using cytochrome c as a model protein we show that two reporter atoms, selenium and bromine, can be simultaneously and site-specifically incorporated without significant consequences to structure and (or) function. This capability opens up the prospect of advances in a number of areas in structural biology.

Key words: semisynthesis, peptide synthesis, reporter groups, cytochrome c, structural biology.
Expression of purinergic P2X2 receptor-channels and their role in calcium signaling in pituitary cells
Authors: Stojilkovic Stanko S , Tomic Melanija , Goor Fredrick Van , Koshimizu Taka-aki
Published: April 2011

Pituitary cells express purinergic receptor-channels (P2XR), the activation of which by ATP is associated with the facilitation of Ca2+ influx. Pharmacological, RT-PCR, and nucleotide sequence analyses confirm the presence of a wild type P2X2aR and a spliced isoform P2X2bR, which lacks a portion of carboxyl terminal amino acids. Wild type and spliced isoform receptors have a similar EC50 for ATP and time-course for activation, but the spliced isoform exhibits rapid and complete desensitization, whereas the wild type channel desensitizes slowly and incompletely. Deletion and insertion studies have revealed that a 6 residue sequence located in carboxyl tail (Arg371-Pro376) is required for sustained Ca2+ influx through wild type receptors. When co-expressed, the wild type and spliced channels form functional heteropolymeric channels. The patterns of Ca2+ signaling in the majority of pituitary cells expressing ATP-gated receptor-channels are highly comparable to those observed in cells co-transfected with P2X2aR and P2X2bR. ATP-induced [Ca2+]i response in pituitary cells is partially inhibited by nifedipine, a blocker of voltage-gated L-type Ca2+ channels, suggesting that P2X2R not only drive Ca2+ into the cell, but also activate voltage-gated Ca2+ entry. Our results indicate that ATP represents a paracrine and (or) autocrine factor in the regulation of Ca2+ signaling, and that its actions are mediated in part by heteropolymeric P2X2R.

Key words: ATP-gated channels, gonadotrophs, lactotrophs, somatotrophs.
Proteasome from cytokine-treated human cells shows stimulated BrAAP activity and depressed PGPH activity
Authors: Nelson Judith E , Altschuller-Felberg Claudia , Loukissa Anna , Cardozo Christopher
Published: April 2011

The branched chain amino acid-preferring (BrAAP) activity of multicatalytic proteinase complex isolated from human umbilical vein endothelial cells and treated with interferon-gamma was increased more than 2-fold, which was associated with a marked increase in LMP7 expression and decreased peptidylglutamyl peptide-hydrolyzing activity. Increases in BrAAP activity in supernatants from cells treated with interferon-gamma, tumor necrosis factor-alpha, interleukin-1beta, interleukin-6, or lipopolysaccharide paralleled the increases in LMP7 expression. These findings are consistent with the conclusion that the increased BrAAP activity of LMP-containing multicatalytic proteinase complex results from incorporation of LMP7 or other LMP subunits.
Cytosensor techniques for examining signal transduction of neurohormones
Authors: Smart D , Wood M D
Published: April 2011

This review describes the principles of microphysiometry and how they can be applied, using the Cytosensor, to the investigation of the signal transduction mechanisms activated by both G-protein and non-G-protein coupled hormone and neuropeptide receptors. The use of the Cytosensor to study desensitisation and cross-talk is also discussed, as are the benefits and limitations of this technique.Key words: Cytosensor, microphysiometry, signal transduction, neuropeptides, hormones.
The ZF87/MAZ transcription factor functions as a growth suppressor in fibroblasts
Authors: Stubbs Matthew C , Min InSung , Izzo Marc W , Rallapalli Ravikumar , Derfoul Assia , Hall David J
Published: April 2011

ZF87/MAZ is a zinc finger transcription factor that activates expression of tissue-specific genes and represses expression of the c-myc proto-oncogene. Infection of NIH3T3 fibroblasts with a retrovirus expressing ZF87/MAZ leads to a significant reduction in G418-resistant colonies, compared to cells infected with a retroviral control. Further, only a small fraction of the G418-resistant colonies express ZF87/MAZ. When the ZF87/MAZ-expressing colonies are expanded, they demonstrate a slow growth phenotype, a delayed transit through G1 phase and a decrease in endogenous c-myc gene expression and cyclin A and cyclin E protein levels. Consistent with a partial G1 arrest, the ZF87/MAZ-expressing cells show a reduced sensitivity to the S phase specific chemotherapeutic agent camptothecin. These data indicate that ZF87/MAZ is a growth suppressor protein in nontransformed cells, in part, by affecting the levels of key cell cycle regulatory proteins.Key words: cell cycle, ZF87/MAZ, cancer.
Autocrine regulation of calcium influx and gonadotropin-releasing hormone secretion in hypothalamic neurons
Authors: Goor Fredrick Van , Krsmanovic Lazar Z , Catt Kevin J , Stojilkovic Stanko S
Published: April 2011

Gonadotropin-releasing hormone (GnRH) receptors are expressed in hypothalamic tissues from adult rats, cultured fetal hypothalamic cells, and immortalized GnRH-secreting neurons (GT1 cells). Their activation by GnRH agonists leads to an overall increase in the extracellular Ca2+-dependent pulsatile release of GnRH. Electrophysiological studies showed that GT1 cells exhibit spontaneous, extracellular Ca2+-dependent action potentials, and that their inward currents include Na+, T-type and L-type Ca2+components. Several types of potassium channels, including apamin-sensitive Ca2+-controlled potassium (SK) channels, are also expressed in GT1 cells. Activation of GnRH receptors leads to biphasic changes in intracellular Ca2+concentration ([Ca2+]i), with an early and extracellular Ca2+-independent peak and a sustained and extracellular Ca2+-dependent plateau phase. During the peak [Ca2+]iresponse, electrical activity is abolished due to transient hyperpolarization that is mediated by SK channels. This is followed by sustained depolarization and resumption of firing with increased spike frequency and duration. The agonist-induced depolarization and increased firing are independent of [Ca2+]iand are not mediated by inhibition of K+currents, but by facilitation of a voltage-insensitive and store depletion-activated Ca2+-conducting inward current. The dual control of pacemaker activity by SK and store depletion-activated Ca2+channels facilitates voltage-gated Ca2+influx at elevated [Ca2+]ilevels, but also protects cells from Ca2+overload. This process accounts for the autoregulatory action of GnRH on its release from hypothalamic neurons.
Characterization of the interaction of recombinant apolipoprotein(a) with modified fibrinogen surfaces and fibrin clots
Authors: Sangrar Waheed , Koschinsky Marlys L
Published: April 2011

Elevated levels of lipoprotein(a) [Lp(a)] in plasma are a significant risk factor for the development of atherosclerotic disease, a property which may arise from the ability of this lipoprotein to inhibit fibrinolysis. In the present study we have quantitated the binding of recombinant forms of apolipoprotein(a) [17K and 12K r-apo(a); containing 8 and 3 copies, respectively, of the major repeat kringle sequence (kringle IV type 2)] to modified fibrinogen surfaces. Iodinated 17K and 12K r-apo(a) bound to immobilized thrombin-modified fibrinogen (i.e., fibrin) surfaces with similar affinities (Kd~ 1.2 - 1.6 µM). The total concentration of binding sites (Bmax) present on the fibrin surface was ~4-fold greater for the 12K than for the 17K (Bmaxvalues of 0.81 ± 0.09 nM, and 0.20 ± 0.01 nM respectively), suggesting that the total binding capacity on fibrin surfaces is reduced for larger apolipoprotein(a) (apo(a)) species. Interestingly, binding of apo(a) to intact fibrin was not detected as assessed by measurement of intrinsic fluorescence of free apo(a) present in the supernatants of sedimented fibrin clots. In other experiments, the total concentration apo(a) binding sites available on plasmin-modified fibrinogen surfaces was shown to be 13.5-fold higher than the number of sites available on unmodified fibrin surfaces (Bmaxvalues of 2.7 ± 0.3 nM and 0.20 ± 0.01 nM respectively) while the affinity of apo(a) for these surfaces was similar. The increase in Bmaxwas correlated with plasmin-mediated exposure of C-terminal lysines since treatment of plasmin-modified fibrinogen surfaces with carboxypeptidase B produced a significant decrease in total binding signal as detected by ELISA (enzyme linked immunosorbent assay). Taken together, these data suggest that apo(a) binds to fibrin with poor affinity (low µM) and that the total concentration of apo(a) binding sites available on modified-fibrinogen surfaces is affected by both apo(a) isoform size and by the increased availability of C-terminal lysines on plasmin-degraded fibrinogen surfaces. However, the low affinity of apo(a) for fibrin indicates that Lp(a) may inhibit fibrinolysis through a mechanism distinct from binding to fibrin, such as binding to plasminogen.Key words: fibrinolysis, lipoprotein(a), plasminogen activation.