bluuebunny/crossref_metadata_2025 huggingface dataset:
Tandem repeats and length variation in the mitochondrial DNA control region ofEpirrita autumnata(Lepidoptera: Geometridae)
Authors: Snäll N , Huoponen K , Savontaus M -L , Ruohomäki K
Published: October 2002

The organization of the mitochondrial DNA (mtDNA) control region (CR) of the autumnal moth, Epirrita autumnata, is described. The E. autumnata CR presents a distinct type of lepidopteran CR with domains of non-repetitive and repetitive sequences. The CRs show considerable length variation owing to a variable number of short ~29-bp sequence blocks that are repeated between 6 and 14 times in tandem. The organization of such a tandem array is unique among the insect CRs examined so far. Furthermore, the E. autumnata CR, which may reach 1075 bp in length, is considerably longer than previously reported lepidopteran CRs, which reach 311499 bp in length. Like other lepidopteran CRs, the E. autumnata CR contains two long homopolymer runs that may be involved in mtDNA replication and (or) transcription.Key words: Lepidoptera, Epirrita autumnata, mitochondrial DNA, control region, tandem array.
Genus-specific localization of theTaiI family of tandem-repetitive sequences in either the centromeric or subtelomeric regions in Triticeae species (Poaceae) and its evolution in wheat
Authors: Kishii Masahiro , Tsujimoto Hisashi
Published: October 2002

The TaiI family sequences are classified as tandem repetitive DNA sequences present in the genome of tribe Triticeae, and are localized in the centromeric regions of common wheat, but in the subtelomeric heterochromatic regions of Leymus racemosus and related species. In this study, we investigated the chromosomal distribution of TaiI family sequences in other Triticeae species. The results demonstrated a centromeric localization in genera Triticum and Aegilops and subtelomeric localization in other genera, thus showing a genus-dependent localization of TaiI family sequences in one or the other region. The copy numbers of TaiI family sequences in species in the same genus varied greatly, whether in the centromeric or subtelomeric regions (depending on genus). We also examined the evolution of TaiI family sequences during polyploidization of hexaploid common wheat. A comparison of chromosomal locations of the major TaiI family signals in common wheat and in its ancestral species suggested that the centromeric TaiI family sequences in common wheat were inherited from its ancestors with little modification, whereas a mixed origin for the B genome of common wheat was indicated.Key words: TaiI family, tandem repeat, centromere, subtelomere, Triticeae.
Application of AFLP markers for QTL mapping in the rabbit
Authors: van Haeringen Wim A , Bieman M G. Den , Lankhorst Æ , van Lith H A , van Zutphen L F.M
Published: October 2002

Two rabbit (Oryctolagus cuniculus) inbred strains (AX/JU and IIIVO/JU) have been used for genetic analysis of quantitative traits related to dietary cholesterol susceptibility. Application of the AFLP (amplified fragment length polymorphism) technique with 15 primer combinations revealed 226 polymorphisms between the 2 inbred strains. A total of 57 animals from a backcross progeny (IIIVO/JU × [IIIVO/JU × AX/JU]F1) were available for the genetic analysis. These backcross animals were fed a commercial pelleted diet fortified with 0.3% w/w cholesterol during a test period that lasted five weeks. A male genetic map could be constructed, consisting of 12 linkage groups and 103 AFLP markers. Linkage analysis between the cholesterol-related traits and marker loci revealed a significant LOD score for the relative weight of adrenal glands in males (LOD score = 3.83), whereas suggestive linkages were found for basal serum total cholesterol levels in females (LOD score = 2.69), for serum total cholesterol response (area under the curve) in males (LOD score = 2.21), and for hematocrit in males (LOD score = 3.24).Key words: adrenal, AFLP, cholesterol, hematocrit, QTL, rabbit.
Highly informative nature of inter simple sequence repeat (ISSR) sequences amplified using tri- and tetra-nucleotide primers from DNA of cauliflower (Brassicaoleraceavar.botrytisL.)
Authors: Bornet B , Muller C , Paulus F , Branchard M
Published: October 2002

Inter simple sequence repeat (ISSR) sequences as molecular markers can lead to the detection of polymorphism and also be a new approach to the study of SSR distribution and frequency. In this study, ISSR amplification with nonanchored primer was performed in closely related cauliflower lines. Fourty-four different amplified fragments were sequenced. Sequences of PCR products are delimited by the expected motifs and number of repeats, which validates the ISSR nonanchored primer amplification technique. DNA and amino acids homology search between internal sequences and databases (i) show that the majority of the internal regions of ISSR had homologies with known sequences, mainly with genes coding for proteins implicated in DNA interaction or gene expression, which reflected the significance of amplified ISSR sequences and (ii) display long and numerous homologies with the Arabidopsis thaliana genome. ISSR amplifications revealed a high conservation of these sequences between Arabidopsis thaliana and Brassica oleracea var. botrytis. Thirty-four of the 44 ISSRs had one or several perfect or imperfect internal microsatellites. Such distribution indicates the presence in genomes of highly concentrated regions of SSR, or "SSR hot spots." Among the four nonanchored primers used in this study, trinucleotide repeats, and especially (CAA)5, were the most powerful primers for ISSR amplifications regarding the number of amplified bands, level of polymorphism, and their nature. Key words: inter simple sequence repeat (ISSR), nonanchored primer, DNA marker sequence, SSR, cluster of SSRs.
Molecular characterization and expression analysis of 1-aminocyclopropane-1-carboxylate oxidase homologs from potato under abiotic and biotic stresses
Authors: Nie Xianzhou , Singh Rudra P , Tai George C.C
Published: October 2002

In this work, we report cloning of two full-length 1-aminocyclopropane-1-carboxylate oxidase (ACO) cDNAs (ACO1 and ACO2) from potato (Solanum tuberosum) and their expression in potato tissues. The sequence data indicate that the two cDNAs share a high degree of homology with each other, and with known ACO genes from other plant species, including monocots and dicots. However, these potato genes lack homology at the 5' and 3' ends, despite similarities in their open reading frames and encoded amino acids. Phylogenetic analysis places them in two subfamilies of ACOs. The genes are tissue specific: expression is high in leaves and low in roots and tubers. In sprouts and tubers, ACO1 is induced by heat (40°C) and cold (0°C) stresses, whereas ACO2 is induced only by cold (0°C). ACO1 is markedly induced in leaves by wounding, soil-flooding, and exogenous application of 1-aminocyclopropane-1-carboxylic acid (ACC). In contrast, ACO2 induction is lower under these treatments. ACO1 and ACO2 are regulated very differently in potato leaves with respect to senescence. ACO2 expression is unaffected by senescence, whereas that of ACO1 is closely related to the age and senescence in both attached and detached leaves. Exogenous ACC not only induces ACO1, but also accelerates leaf senescence. ACO1 transcripts are induced significantly in leaves, stems, and tubers in the Potato virus A (PVA)-resistant potato cultivar Shepody when graft inoculated with PVA.Key Words: ACO, ethylene, gene isolation, phylogeny, Solanum tuberosum.
Genetic diversity among Canadienne, Brown Swiss, Holstein, and Jersey cattle of Canada based on 15 bovine microsatellite markers
Authors: Hansen C , Shrestha J N.B , Parker R J , Crow G H , McAlpine P J , Derr J N
Published: October 2002

The genetic diversity among Canadienne, Brown Swiss, Holstein, and Jersey cattle was estimated from relationships determined by genotyping 20 distantly related animals in each breed for 15 microsatellites located on separate chromosomes. The Canadienne, Holstein, and Jersey cattle had an average of six alleles per loci compared with five alleles for Brown Swiss. Furthermore, a number of potentially breed-specific alleles were identified. The allele size variance among breeds was similar, but varied considerably among loci. All of the loci studied were equally heterozygous, as were Brown Swiss, Canadienne, and Holstein cattle (0.680.69) whereas Jersey cattle showed lower heterozygosity (0.59). The within-breed estimates of genetic distance were greater than zero and significant. The genetic distance between Canadienne and Holstein (0.156), Brown Swiss (0.243), and Jersey (0.235) was negligible, suggesting close relationship. Concurrently, Brown Swiss and Holstein (0.211) cattle also demonstrated close relationship. In contrast, the Jersey breed was genetically distant from the Brown Swiss and Holstein cattle (0.427 and 0.320, respectively). The characterization of Canadienne cattle, as part of the genetic resource conservation effort currently underway in Canada, underscores the difficulty in scientifically establishing unique breeds. Therefore, the need to consider all relevant morphological characteristics and production performance in combination with available cultural, historical, pedigree, and molecular information becomes relevant when identifying breeds for conservation.Key words: genetic distance, microsatellites, cattle, genetic resource conservation.
A set of microsatellite markers for fingerprinting and breeding applications in Pinus radiata
Authors: Devey M E , Bell J C , Uren T L , Moran G F
Published: October 2002

Fifty microsatellite markers were developed and characterized in Pinus radiata, and from among these, a subset of 10 easily scored and highly polymorphic markers was selected for use in fingerprinting, quality control, and breeding applications. The markers were characterized based on reliable and reproducible amplification, observed and expected heterozygosities, number of alleles, a low frequency of null alleles, and a lack of close linkage with other selected markers. Allele numbers and frequencies were estimated using 24 first-generation breeding clones from Australia and New Zealand. Observed heterozygosities for the selected markers were all greater than 0.67, and there was an average of 10.5 alleles/locus. The occurrence of null alleles was checked with megagametophytes from mother trees for loci that appeared to be homozygous. The 10 markers are not closely linked (r < 0.20 and LOD > 3) to each other. The selected microsatellites fall into three discrete size classes, and with appropriate selection of fluorescent dyes for 5' end labeling, can be multiplexed with up to 6 markers/sample on an ABI PRISM 310 or similar instrument.Key words: pine microsatellites, multiplexing, null alleles.
Resolving the aphid resistance locusSd-1 on a BAC contig within a sub-telomeric region ofMaluslinkage group 7
Authors: Cevik Volkan , King Graham J
Published: October 2002

Aphids cause serious physical and economic damage to most major crops throughout the world, and there is a pressing requirement to isolate genes conferring aphid resistance. The Sd-1 locus in Malus spp. (apple) confers resistance against the rosy leaf-curling aphid (Dysaphis devecta Wlk.), and was recently positioned within a 1.3-cM region on linkage group 7, flanked by molecular markers. These markers were used as a basis for development of a BAC contig spanning the locus, together with adapter-mediated amplification of flanking sequences to obtain BAC insert-end sequences, and fingerprinting of BAC clones. Approximately 800 kb of the Sd-1 genomic region was covered by 19 overlapping BACs, with an average insert size of 75150 kb. The physical  genetic distance ratio was estimated at 460 kb/cM, although the distribution of recombination events was irregular with respect to estimated physical distance. Recombinant analysis and development of new markers allowed Sd-1 to be positioned within an interval of approximately 180 kb located on either of two overlapping BACs. From one of these, an insert end sequence showed a significant degree of similarity to nucleotide binding site  leucine rich repeat (NBSLRR) resistance genes. Fluorescent in situ hybridization (FISH) of BAC clones within the contig enabled positioning and orientation of the locus within a euchromatic region, very close to the telomere of linkage group 7.Key words: aphid, resistance gene, apple, Malus, physical map.
Estimating the cost of capital projects: an empirical study of accuracy levels for municipal government projects
Authors: AbouRizk S M , Babey G M , Karumanasseri G
Published: October 2002

This paper highlights the findings of a study undertaken to assess the accuracy of cost estimates for construction projects at various levels of design maturity. Specifically, this paper addresses the accuracy of cost estimates for major types of municipal works including drainage, roadways, and building projects over a span of 3 years. Over 200 projects were statistically evaluated in the study at four levels of the design, namely, concept, preliminary, detailed, and award. Those estimates were then compared with actual incurred cost at project completion. In general, it was found that estimates are not as accurate as generally believed. It was also confirmed that cost estimates for rehabilitation work were less accurate than those for new work. In the absence of major changes to the design and estimation processes, more tempered accuracy limits were derived and proposed.Key words: estimating, budgeting, construction costs, variability in capital costs.
Positioning of bearings for curved continuous spread-box girder bridges
Authors: Samaan Magdy , Sennah Khaled , Kennedy John B
Published: October 2002

The type and arrangement of bearings for a bridge superstructure are important considerations in bridge design. For a curved continuous spread-box girder bridge, the support conditions for the bridge superstructure may significantly influence the distribution factors for maximum stresses, reactions, and shear forces as well as the bridge natural frequencies and mode shapes. Current design practices in North America recommend very few guidelines for bearing arrangements and types. This paper describes an extensive study carried out using an experimentally calibrated finite element model, in which curved continuous prototype bridges were analyzed to determine their structural response. Six different types and arrangements of support bearings were studied to determine their effect on the maximum stress and reaction distributions as well as on the natural frequencies of such bridges. The results were used to suggest the most favourable bearing arrangement and type.Key words: bridge bearings, composite, continuous, curved bridges, design, distribution factors, finite element, spread-box.
Timber shear walls with large openings: experimental and numerical prediction of the structural behaviour
Authors: Richard Nicolas , Daudeville Laurent , Prion Helmut , Lam Frank
Published: October 2002

A numerical model based on the finite element method is presented for prediction of the cyclic response of wood frame structures. The model predicts the cyclic response of shear walls. Nonlinear phenomena are assumed to be concentrated in the connections that are modelled through elements linking the structural elements including the posts, beams, and sheathing panels. Identification of model parameters relies on tests on individual connections. Connection tests on different nail lengths were conducted under monotonic and cyclic lateral loads. Based on the results from past studies that indicate the pull-through failure is an important failure mode in common nail connections with lumber and oriented strand board (OSB), washers were considered as a means to reinforce the connection. The influence of reinforced nailing on the static and dynamic performance of full-size wood frame shear walls with large openings, sheathed with OSB panels, was evaluated experimentally. Combinations of parameters were studied, such as the number of hold-downs, the panel shapes, the nail distribution, and the bracing systems. Comparisons of the dissipated energy per cycle revealed a higher capacity for walls using nails with washer reinforcement than without. Results from numerical simulations of the monotonic and cyclic tests performed on the walls are presented.Key words: timber shear wall, connections, finite element, dissipated energy.
Evaluation of standard error of forecast of runoff volume using linear regression models
Authors: Luo Wuben , Weiss Eric
Published: October 2002

Optimizing reservoir operations requires forecasts of seasonal inflow and a good understanding of the associated uncertainties. When forecasting seasonal runoff volume to a reservoir using a linear regression model, hydrologic forecasters typically use the standard error of residuals as the standard error of forecast to give water managers a sense of uncertainties in the forecast. However, this practice accounts for only the random error and ignores the modeling error in the volume forecast, resulting in underestimation of the standard error of the forecast. The underestimation can become significant in extreme runoff years for which reservoir operations tend to be most critical. This paper presents the algorithm for calculating the standard error of forecast, which takes into consideration both random and modeling errors. A simple way of calculating the standard error of forecast using built-in functions in Microsoft Excel is described. An example is used to demonstrate the potentially significant underestimation of the true error of a forecast if modeling error is ignored.Key words: standard error of forecast, residuals, runoff volume forecast, regression analysis.
Surface rutting of thin pavements and gravel roads under standard and reduced tire inflation pressures
Authors: Shalaby Ahmed , Reggin Alan
Published: October 2002

In Canada, over 300 heavy vehicles equipped with central tire inflation systems are being used in forestry, mining, and grain hauling. Since 1995, Saskatchewan Highways and Transportation has permitted truck fleets to operate with primary highway axle loads on secondary highways under a partnership program. This paper reports on the comparison of rutting progression on an accelerated field experiment utilizing standard and reduced tire pressures. The experiment was conducted by Saskatchewan Highways and Transportation in the Big Quill Lake area of southern Saskatchewan. The vehicles used in the experiment were nine-axle B trains, eight-axle B trains, and six-axle semi-trailers. The statistical analysis of rutting data presented in the paper shows that reduced tire pressures can effectively extend the pavement service life of gravel and thin membrane surfaced roads. On the thin membrane pavements, there was less rutting on the low-pressure lane until twice as many vehicles had trafficked the road, and rutting was no worse on the low-pressure lane even when 10 times as many vehicles had trafficked the road. On the gravel surface, rut depth was lower on the low-pressure lane until twice as many trucks had trafficked that lane.Key words: rutting, pavement, central tire inflation, tire pressure, low-volume roads, unsurfaced roads.
Mechanical properties of self-tapping screws and nails in wood
Authors: Hansen Klavs Feilberg
Published: October 2002

This paper presents results of a research programme investigating the mechanical properties of self-tapping screws and nails in wood. The programme consisted of deformation-controlled tests to determine embedment strength, withdrawal strength, pull-through strength, bending capacity of individual screws, shear strength of screwed and nailed woodwood connections, and shear strength of screwed woodsteel connections. All test specimens showed ductile behaviour. Based on the results from the first four types of tests, a simple calculation model for the shear strength of screwed woodwood and woodsteel connections was set up and compared with test results from the last two types of tests. The calculation model took dowel action and friction (woodwood and woodsteel) into account and showed excellent agreement with the test results.Key words: connections, screws, nails, shear strength, embedment strength, withdrawal strength, pull-through strength.
Composite steel-free deck bridges: Numerical modelling and pilot parametric study
Authors: Salem Adel H , El-Aghoury Mohamed A , Sayed-Ahmed Ezzeldin Y , Moustafa Tarek S
Published: October 2002

During the past decade, composite steel-free deck bridges came to reality in Canada through the construction of five bridges. The new structural system enables the construction of a concrete deck that is totally devoid of all internal steel reinforcement. Traditionally, reinforced concrete bridge decks are designed to sustain loads in flexure. The steel-free deck bridge system develops internal compressive forces "internal arching," which leads to failure by punching shear at substantially higher loads than the flexural design load. The fibre-reinforced concrete deck is usually attached to the steel girders through flexible shear connectors. These steel girders are transversely tied together by steel straps and cross frames. In this paper, the concept of the new bridge system is briefly discussed. The generations of the deck slabs are introduced. Brief outlines of the bridges built to date with this new technology are presented. A three-dimensional finite element model is then proposed to study the behaviour of the main structural component of the new system. The model is verified against previous experimental results and is used to perform a parametric study on some aspects which are thought to significantly affect the behaviour of the new steel-free deck bridge system.Key words: bridges, composite girders, finite element method, steel-free deck, steel straps.
Comparison of fuzzy set ranking methods for implementation in water resources decision-making
Authors: Prodanovic Predrag , Simonovic Slobodan P
Published: October 2002

A new multicriteria technique, fuzzy compromise programming (FCP), is used to evaluate discrete alternatives in the context of water resources decision-making. All uncertain variables (subjective and objective) are modeled by way of fuzzy sets. Fuzzy set ranking methods are employed to compare, rank, and (or) sort the fuzzy output produced by FCP. The literature suggests that many ranking methods are available; however, not all may be appropriate for water resources decision-making. The objective of this paper is to compare fuzzy set ranking methods that can be implemented with FCP. Nine such ranking methods are considered in this research, two of which are fully tested using case studies from the literature. It was found that for all case studies, the ranking of alternatives was not very sensitive to changes in the degree of risk acceptance by experts or changes in the ranking methods themselves.Key words: fuzzy set ranking methods, risk preferences, compromise decision, water resources systems.
A simplified approach for the historical analysis of urban person travel
Authors: Shalaby Amer S
Published: October 2002

This paper presents a simplified approach to quantify the contribution of individual factors to the historical growth or decline in total travel between two points in time. The method employs person trip rates and distributions of the individual characteristics at the two time points to determine the portion of urban person travel increase or decrease associated with the change in each factor. The paper presents the application of the approach to investigate changes in person travel in the Greater Toronto Area between 1986 and 1996. Specifically, the study determined the change in person travel attributed to each of the following factors independently: change in population size, change in age distribution, change in residential location distribution, and change in employment status distribution (full time, part time, work at home). The data were obtained from the 1986 and 1996 Transportation Tomorrow Surveys (TTSs).Key words: transportation planning, travel demand.
A comparison of index flood estimation procedures for ungauged catchments
Authors: Grover Patrick L , Burn Donald H , Cunderlik Juraj M
Published: October 2002

Flood frequency analysis is used by water resources professionals to estimate the probability of exceedence associated with a flood of a given magnitude. The estimation of flood frequencies is important because they are used in the planning and design of hydraulic structures, in flood-plain management, and in reservoir operation. The index flood method is commonly used to develop a flood frequency curve that relates flood magnitude to flood rarity. This method involves scaling a dimensionless flood frequency curve by the index flood. The index flood is a middle-sized flood for which the mean or median of the flood data series is typically used. When the catchment of interest is ungauged, statistical models, such as multiple regression, are often used to relate the index flood to catchment descriptors. In this study six different parameter estimation techniques and three regionalization techniques are compared in terms of ability to predict the index flood for an ungauged catchment. A case study employing a split-sample experiment with data from catchments in Ontario, Canada, was used to evaluate the approaches. The models were assessed using three performance indices to evaluate the capability to predict the index flood for 20 stations. The dimensionless nonlinear model outperformed all of the other parameter estimation techniques for each of the three indices selected. The performance was improved through the use of geostatistical residual mapping, however, the improvement was small. The residual mapping was found to greatly improve the estimates obtained using ordinary least-squares regression.Key words: index flood, flood frequency analysis, regression, residual mapping, geostatistics.
The effects of fibers on the confinement models for concrete columns
Authors: Campione Giuseppe
Published: October 2002

A mathematical model is developed to express the stressstrain relationships in compression of fiber-reinforced concrete (FRC) columns for both normal- and high-strength concrete, with and without conventional steel reinforcement. This model allows one to determine the maximum strength and strain capacity by determining the effective concrete core of the confining devices at rupture. Analytical expressions are also given for the ultimate load corresponding to the complete formation of the concrete failure plane. The proposed model incorporates the most relevant parameters of confinement, i.e., type of confinement, volumetric ratio, spacing, yielding strength, shape of the member cross section, type of fiber (length, diameter, shape), and fiber volume. The model has been verified against data obtained from concentric compressive tests on concrete specimens reinforced with transverse steel and fibers.Key words: high-strength concrete, fiber-reinforced concrete, lateral reinforcement, stressstrain curves.
User cost savings in eliminating pavement excavations through employing trenchless technologies
Authors: Tighe S , Knight M , Papoutsis D , Rodriguez V , Walker C
Published: October 2002

When a pipeline is installed under flexible pavement structures using open excavation and fill methods, the excavation can result in premature pavement deterioration due to difficulties associated with trench site restoration and soil and asphalt compaction. In developed areas, trenchless construction methods have become a popular alternative to open trench excavation because of reduced surface disruptions and reinstatement costs, a shorter construction period, and significantly reduced traffic delay costs associated with construction by saving time in construction operations. This paper summarizes a recent study that examined how pipeline installations on 1- and 7-year-old Ontario municipal collectors and minor arterial roads impact the 30-year life cycle of a pavement in terms of performance, future maintenance costs, and user-delay costs. Study results indicated that (1) approximately 30% reduction in pavement life can be expected once an excavation is made in a road; (2) increased maintenance and rehabilitation costs for excavating 1-year-old pavement were determined to be approximately Can$146/m2, and the costs for excavating 7-year-old pavement vary from Can$85 to $140/m2; and (3) the use of trenchless technology with good construction practices has the potential to significantly reduce road maintenance and rehabilitation costs and user-delay costs.Key words: pavement performance, open excavation, trenchless technologies, user-delay costs.
Strength of wind load bearing wall stud-to-track connections
Authors: Fox Steven R , Schuster Reinhold M
Published: October 2002

Cold-formed steel structural members are often used in building construction, with a common application being wind load bearing steel studs. The studs frame into horizontal steel track members at the top and bottom of the wall assembly, with the stud-to-track connection typically being made with self-drilling screws or welds. The design of the wall stud must include a check of the web crippling capacity at the end reactions. The type of end bearing that exists in these stud-to-track connections is not explicitly addressed by the current North American cold-formed steel design documents. Reported in this paper are the results and analysis of a collection of end-one-flange web crippling tests of common stud-to-track connections. The tests show that there are two failure modes: web crippling of the stud, and punch-through of the track flange. Design expressions are proposed to predict the capacity of the connection based on these two modes of failure. The effects of increasing the gap between the stud and the track and the effects of missing screws in the stud-to-track connection are also discussed.Key words: cold-formed steel, steel studs, structural design, connections, web crippling.
Stability of concrete macro-roughness linings for overflow protection of earth embankment dams
Authors: Manso Pedro de Almeida , Schleiss Anton J
Published: October 2002

A macro-roughness lining system for the protection of earth embankment dams during overflow is presented. It consists of precast concrete elements placed on a drainage-separation layer. The main difference between this system and other existing concrete element systems is the stability concept, based on the self-weight of the blocks. Several types of elements were developed and tested in a physical model for a typical dam slope of 1V:3H. Failure conditions were identified after submitting the elements to increasing flow discharges. Furthermore, different foundation drainage and shear conditions between the elements and their foundation and different joint alignments were studied. Flow characteristics were observed and measured for quasi-uniform flow conditions. Based on the experimental results, a stability model was developed to compute the design safety factor. The model is based on the governing overturning equation (predominant failure mechanism) and on assumptions concerning the acting hydrodynamic forces, the hydrostatic uplift, and the concentration of air in the flow. Synoptic design charts were derived for 1V:3H dam slopes, allowing the rapid estimate of the lining characteristics as dimensions and weight for a certain withstood design unit discharge, for various margins of safety. The developed macro-roughness lining system is envisaged for the spillway rehabilitation of existing dams, but also for the design and construction of spillways of low dams (up to 30 m in height) and for the protection of overflow cofferdams.Key words: overflow dams, erosion protection, linings, macro-roughness, stability, drainage and spillways.
Effect of joint contamination on the quality of butt-fused high-density polyethylene (HDPE) pipe joints
Authors: Zhao Jack Q , Daigle Lyne , Beaulieu Denis
Published: October 2002

Butt fusion is an effective method for joining high-density polyethylene (HDPE) pipe on job sites. However, there is lack of quantitative methods to evaluate pipe joint quality. The objective of this study was to develop such a quantitative approach to determine the effect of joint contamination on the quality of the fused joints. The study included testing a total of 21 butt-fused HDPE pipe joints that were made under different dust conditions. The results of the tests were then used to determine the effect of dust contamination on the quality of the fused joints. Microscopic examination of the fracture surfaces of the test specimens showed that not all the contaminants at the welding interface were squeezed out into the beads formed during the fusion process. Four failure modes were identified and a failure criterion was established to categorize the quality of a fused joint into four grades: bad, poor, good, and excellent. Among the properties of the materials considered, tensile energy to break (TEB) and maximum strain were found to be the most acceptable parameters for distinguishing between joints of different quality. Furthermore, the results showed that under optimum joining conditions, the quality of butt-fused joints can be as good as that of the parent pipe.Key words: polyethylene pipe, butt fusion, joint contamination, tensile energy to break, failure criterion.
Reliability assessment in highway bridge design
Authors: Cheung M S , Li W C
Published: October 2002

The current practice of highway bridge design in Canada is based on limit states design. Ideally, by means of the properly calibrated load and resistance factors specified in the applicable design code, limit states design will yield a consistent and uniform safety level for all designed bridge structures. Some factors neglected in the standard design procedures, however, may have unexpected effects on the reliability of a particular design. In this case, to follow a design code exactly may still lead to a certain degree of underdesign or overdesign. Therefore, the reliability assessment is recommended for each particular design, and a simulation-based approach for this assessment is proposed in this study. Examples are presented to support the afore-mentioned recommendation.Key words: highway bridges, reliability, design code, simulation, finite strip method.
Stable heteroplasmy but differential inheritance of a large mitochondrial DNA deletion in nematodes
Authors: Tsang William Y , Lemire Bernard D
Published: October 2002

Many human mitochondrial diseases are associated with defects in the mitochondrial DNA (mtDNA). Mutated and wild-type forms of mtDNA often coexist in the same cell in a state called heteroplasmy. Here, we report the isolation of a Caenorhabditis elegans strain bearing the 3.1-kb uaDf5 deletion that removes 11 genes from the mtDNA. The uaDf5 deletion is maternally transmitted and has been maintained for at least 100 generations in a stable heteroplasmic state in which it accounts for ~60% of the mtDNA content of each developmental stage. Heteroplasmy levels vary between individual animals (from ~20 to 80%), but no observable phenotype is detected. The total mtDNA copy number in the uaDf5 mutant is approximately twice that of the wild type. The maternal transmission of the uaDf5 mtDNA is controlled by at least two competing processes: one process promotes the increase in the average proportion of uaDf5 mtDNA in the offspring, while the second promotes a decrease. These two forces prevent the segregation of the mtDNAs to homoplasmy.Key words: mtDNA deletion, Caenorhabditis elegans, heteroplasmy, inheritance, mtDNA copy number.
Phagocytosis and the microtubule cytoskeleton
Authors: Harrison Rene E , Grinstein Sergio
Published: October 2002

Phagocytosis is a critical host defense mechanism used by macrophages and neutrophils to clear invading pathogens. The complex sequence of events resulting in internalization and degradation of the pathogens is a coordinated process involving lipids, signaling proteins, and the cytoskeleton. Here, we examine the role of the microtubule cytoskeleton in supporting both the engulfment of pathogens and their elimination within phagolysosomes.Key words: macrophage, microtubule, phagocytosis, maturation, Fc receptor.
Transport characteristics of HL-1 cells: a new model for the study of adenosine physiology in cardiomyocytes
Authors: Chaudary Naz , Shuralyova Irina , Liron Tamar , Sweeney Gary , Coe Imogen R
Published: October 2002

Adenosine is a physiologically important nucleoside in the cardiovascular system where it can act as a cardioprotectant and modulator of energy usage. Adenosine transporters (ATs) modulate cellular adenosine levels, which, in turn, can affect a number of processes such as receptor activation and glucose uptake, but their role in cardiac physiology is poorly understood. Therefore, we have developed a new cell model by determining various adenosine-related characteristics of HL-1, an immortalized atrial cardiomyocyte murine cell line. Adenosine uptake in HL-1 cells is sodium independent, saturable, and inhibitable by nucleoside transport inhibitors (nitrobenzylthioinosine (NBTI), dipyridamole, dilazep). Reverse transcription  polymerase chain reaction analysis confirmed that HL-1 cells possess mouse equilibrative nucleoside transporters 1 and 2 (mENT1, mENT2) and kinetic analyses indicate moderate-affinity (Km= 51.3 ± 12.9 μM), NBTI-sensitive adenosine transport. NBTI binds at a high-affinity single site (Bmax= 520 ± 10 fmol/mg protein, Kd= 0.11 ± 0.04 nM, 1.6 × 105NBTI-binding sites/cell). HL-1 cells possess adenosine receptor, metabolic enzyme, protein kinase C isoform, and insulin-stimulated glucose transport profiles that match normal mouse heart. Therefore, HL-1 is an excellent model to study ATs within cardiomyocytes and the first model for evaluating in detail the role of the ATs in modulating effects of adenosine.Key words: adenosine, nucleoside transport, HL-1 cells, cardiovascular, glucose transport, protein kinase C.
Molecular basis of voltage gating of OmpF porin
Authors: Robertson Kindal M , Tieleman D Peter
Published: October 2002

OmpF and PhoE from Escherichia coli and related homologous proteins from other Gram-negative bacteria allow the passive transport of small polar molecules across the bacterial outer membrane. In vitro, they exhibit voltage gating depending on the experimental conditions. We review current hypotheses on the underlying molecular mechanism of voltage gating of OmpF porin and show how computer simulations can be used to examine each of the proposed mechanisms. Key words: β-barrels, eyelet region, porins, E. coli, α-haemolysin.
Glycosylphosphatidylinositol-anchored proteins: structure, function, and cleavage by phosphatidylinositol-specific phospholipase C
Authors: Sharom Frances J , Lehto Marty T
Published: October 2002

A wide variety of proteins are tethered by a glycosylphosphatidylinositol (GPI) anchor to the extracellular face of eukaryotic plasma membranes, where they are involved in a number of functions ranging from enzymatic catalysis to adhesion. The exact function of the GPI anchor has been the subject of much speculation. It appears to act as an intracellular signal targeting proteins to the apical surface in polarized cells. GPI-anchored proteins are sorted into sphingolipid- and cholesterol-rich microdomains, known as lipid rafts, before transport to the membrane surface. Their localization in raft microdomains may explain the involvement of this class of proteins in signal transduction processes. Substantial evidence suggests that GPI-anchored proteins may interact closely with the bilayer surface, so that their functions may be modulated by the biophysical properties of the membrane. The presence of the anchor appears to impose conformational restraints, and its removal may alter the catalytic properties and structure of a GPI-anchored protein. Release of GPI-anchored proteins from the cell surface by specific phospholipases may play a key role in regulation of their surface expression and functional properties. Reconstitution of GPI-anchored proteins into bilayers of defined phospholipids provides a powerful tool with which to explore the interactions of these proteins with the membrane and investigate how bilayer properties modulate their structure, function, and cleavage by phospholipases.Key words: glycosylphosphatidylinositol anchor, lipid bilayers, reconstitution, ecto-5'-nucleotidase, placental alkaline phosphatase.
Tryptophan-rich antimicrobial peptides: comparative properties and membrane interactions
Authors: Schibli David J , Epand Raquel F , Vogel Hans J , Epand Richard M
Published: October 2002

The interaction of several tryptophan (Trp)-rich cationic antimicrobial peptides with membranes was investigated. These peptides included tritrpticin, indolicidin, lactoferricin B (Lfcin B), and a shorter fragment of lactoferricin (LfcinB49). The average environment of the Trp residues of these peptides was assessed from their fluorescence properties, both the wavelength of maximal emission as well as the red edge effect. The insertion of the peptides into vesicles of differing composition was examined using quenching of the Trp fluorescence, with both soluble acrylamide and nitroxide-labelled phospholipids as well as by chemical modification of the Trp residues with N-bromosuccinimide. The results were consistent with the Trp side chains positioned mostly near the membranewater interface. The extent of burial of the Trp side chains appears to be greater in vesicles containing phospholipids with the anionic phosphatidylglycerol headgroup. Leakage of the aqueous contents of liposomes was also measured using the 8-aminonaphthalene-1,3,6-trisulfonic acid  p-xylene-bis-pyridinium bromide assay. Tritrpticin, which demonstrated the greatest red edge shift, also displayed the largest amount of leakage from liposomes. Taken together, the results illustrate that cationic Trp-rich antimicrobial peptides preferentially disrupt large unilamellar vesicles with a net negative charge following their insertion into the interfacial region of the phospholipid bilayer.Key words: lactoferricin B, indolicidin, tritrpticin, antimicrobial peptide, membrane, vesicle, fluorescence, spin-label, quenching.
Comparison of the interaction of uridine, cytidine, and other pyrimidine nucleoside analogues with recombinant human equilibrative nucleoside transporter 2 (hENT2) produced inSaccharomyces cerevisiae
Authors: Vickers Mark F , Kumar Rakesh , Visser Frank , Zhang Jing , Charania Jahangir , Raborn R Taylor , Baldwin Stephen A , Young James D , Cass Carol E
Published: October 2002

The human equilibrative nucleoside transporters 1 and 2 (hENT1, hENT2) share 50% amino acid identity and exhibit broad selectivities, accepting purine and pyrimidine nucleosides as permeants. The permeant selectivity of hENT2 is less well understood because of the low abundance of the native transporter in cells amenable to functional analysis. Recent studies of hENT2 produced in recombinant form in functional expression systems have shown that it differs from hENT1 in that it transports nucleobases. To further understand the structural requirements for permeant interaction with hENT2, we compared the relative abilities of uridine, cytidine, and their analogues to inhibit transport of [3H]uridine by recombinant hENT1 and hENT2 produced in yeast. hENT1 and hENT2 tolerated halogen modification at the 5 position of the base and the 2' and 5' positions of the ribose moieties of uridine whereas removal of the hydroxyl group at the 3' position of the ribose moiety of uridine eliminated interaction with both transporters. hENT2 displayed a lower ability, compared with hENT1, to interact with cytidine and cytidine analogues, suggesting a low tolerance for the presence of the amino group at the 4 position of the base.Key words: hENT2, hENT1, araC, uridine, NBMPR.
Origami in the outer membrane: the transmembrane arrangement of mitochondrial porins
Authors: Bay Denice C , Court Deborah A
Published: October 2002

Voltage-dependent anion-selective channels (VDAC), also known as mitochondrial porins, are key regulators of metabolite flow across the mitochondrial outer membrane. Porins from a wide variety of organisms share remarkably similar electrophysiological properties, in spite of considerable sequence dissimilarity, indicating that they share a common structure. Based on primary sequence considerations, analogy with bacterial porins, and circular dichroism analysis, it is agreed that VDAC spans the outer membrane as a β-barrel. However, the residues that form the antiparallel β-strands comprising this barrel remain unknown. Various predictive methods, largely based on the known structures of bacterial β-barrels, have been applied to the primary sequences of VDAC. Refinement and confirmation of these predictions have developed through numerous investigations of wild-type and variant porins, both in mitochondria and in artificial membranes. These experiments have involved VDAC from several sources, precluding the generation of a unified model. Herein, using the Neurospora VDAC sequence as a template, the published structural information and predictions have been reassessed to delineate a model that satisfies most of the available data.Key words: VDAC, mitochondrial porin, β-barrel.
Controversy regarding the secondary active water transport hypothesis
Authors: Lapointe Jean-Yves , Gagnon Marilène P , Gagnon Dominique G , Bissonnette Pierre
Published: October 2002

Historically, water transport across biological membranes has always been considered a passive process, i.e., the net water transport is proportional to the gradients of hydrostatic and osmotic pressure. More recently, this dogma was challenged by the suggestion that secondary active transporters such as the Na/glucose cotransporter (SGLT1) could perform secondary active water transport with a fixed stoichiometry. In the case of SGLT1, the stoichiometry would consist of one glucose molecule to two Na+ ions to 220400 water molecules. In the present minireview, we summarize and criticize the evidence supporting and opposing this water cotransport hypothesis. Published and unpublished observations from our own laboratory are also presented in support of the idea that transport-dependent osmotic gradients begin to build up immediately after cotransport commences and are fully responsible for the cell swelling observed.Key words: Xenopus oocyte, intracellular diffusion, water cotransport, SGLT1.
Structure and function of the NHE1 isoform of the Na+/H+exchanger
Authors: Slepkov Emily , Fliegel Larry
Published: October 2002

The Na+/H+exchanger is a ubiquitous, integral membrane protein involved in pH regulation. It removes intracellular acid, exchanging a proton for an extracellular sodium ion. There are seven known isoforms of this protein that are the products of distinct genes. The first isoform discovered (NHE1) is ubiquitously distributed throughout the plasma membrane of virtually all tissues. It plays many different physiological roles in mammals, including important functions in regulation of intracellular pH, in heart disease, and in cytoskeletal organization. The first 500 amino acids of the protein are believed to consist of 12 transmembrane helices, a membrane-associated segment, and two reentrant loops. A C-terminal regulatory domain of approximately 315 amino acids regulates the protein and mediates cyto skel etal interactions. Studies are underway to determine the amino acid residues important in NHE1 function. At present, it is clear that transmembrane segment IV is important in NHE1 function and that transmembrane segments VII and IX are also involved in transport. Further experiments are required to elucidate the mechanism of transport and regulation of this multifunctional protein.Key words: cation transport, intracellular pH, membrane proteins, Na+/H+exchanger.