bluuebunny/crossref_metadata_2025 huggingface dataset:
Chronology of crustal growth and recycling in the Paleoproterozoic Amisk collage (Flin Flon Belt), Trans-Hudson Orogen, Canada
Authors: Stern R A , Machado N , Syme E C , Lucas S B , David J
Published: April 2011

U-Pb zircon ages have been compiled for magmatic and sedimentary rocks from the low metamorphic grade portion of the Flin Flon greenstone belt, now recognized as a Paleoproterozoic tectonic collage. The "Amisk collage" formed in two major magmatic periods that were separated by an interval of intraoceanic accretionary tectonics. Pre-accretionary volcanic and plutonic rocks of arc and ocean-floor tectonic affinities have crystallization ages of 1.906-1.901 and 1.888-1.881 Ga; the earlier period was dominated by juvenile tholeiitic arc basalts and related back-arc-basin basalts, and the younger period by juvenile calc-alkaline volcanic rocks and turbidites. Intraoceanic accretion of the diverse tectono-stratigraphic assemblages may have commenced between 1.90 and 1.89 Ga, but the main period was 1.88-1.87 Ga. The post-accretionary period (1.876-1.838 Ga) was characterized by intrusion of juvenile calk-alkaline plutons generated by a successor arc that stitched the diverse pre-accretionary assemblages. Marine to subaerial volcaniclastic and epiclastic units were deposited in successor basins <=1.87 Ga (Schist-Wekusko suite), succeeded by alluvial-fluvial (Missi Group) to marine (Burntwood Group) sediments after 1.85 Ga. Despite the dominance of juvenile magmatic rocks within the collage, U-Pb zircon age and Nd-isotopic data show that older (>2.2-3.0 Ga) basement fragments were present throughout the development of the Amisk collage. An arc-back-arc system close to an Archean craton is proposed as the most likely tectonic setting during formation and accretion of the Amisk collage from 1.90 to 1.84 Ga. Subsequent continental collision during peak orogeny (1.84-1.81 Ga) is interpreted to have delaminated the lower crust and upper mantle of the collage, preferentially preserving crust of intermediate bulk composition.
Extension of lithofacies and conodont biofacies models of Late Devonian to Early Carboniferous carbonate ramp and black shale systems, southern Canadian Rocky Mountains
Authors: Savoy Lauret E , Harris Anita G , Mountjoy Eric W
Published: April 2011

Uppermost Devonian and Lower Mississippian strata in the Rocky Mountains of southwestern Canada and northwestern Montana record widespread oceanographic changes during middle to late Paleozoic time associated with the termination of a carbonate ramp system, the onset of a deep-water, low-oxygen event and possible marginal tectonism, and the later reestablishment of a carbonate ramp. Integrated lithofacies and conodont biofacies developed previously for these strata between the Bow Valley and the international border have been extended northward to the Athabasca region of the Alberta Rocky Mountains. During early-middle Famennian time, the southern Canadian Rocky Mountains region was the site of a westward-deepening and westward-thickening carbonate ramp system (Palliser Formation). By late Famennian time carbonate ramp deposition ended and was followed by widespread deposition of organic-rich, low-oxygen facies in shelf to basinal environments (Exshaw Formation and correlative units). The overlying Banff Formation consists of anaerobic to marginally aerobic, starved-basin to deep-ramp lithofacies succeeded by shallower water carbonates; this sequence records basinward (westward) progradation of the Banff ramp in middle to late Tournaisian time. Distinct conodont biofacies representative of shallow-ramp to deep-basin settings that were previously recognized in the southernmost Canadian Rocky Mountains and Montana have also been identified to the north between the North Saskatchewan and Athabasca valleys. Upper Palliser carbonates contain low-diversity conodont faunas of indigenous to transported palmatolepid-, polygnathid-, and apatognathid-dominated assemblages. Exshaw deposits contain indigenous and reworked palmatolepid- and bispathodid-dominated assemblages and reworked or transported polygnathids. Lower Banff biofacies include transported and indigenous assemblages of siphonodellids, polygnathids, and pseudopolygnathids representative of the deep-middle Banff ramp. Polygnathid-hindeodid biofacies of shallower middle-ramp environments occur higher in the Banff Formation in the North Saskatchewan and Athabasca valleys.
Catchment and lake controls over the formation of varves in monomictic Nicolay Lake, Cornwall Island, Nunavut
Authors: Lamoureux Scott F
Published: April 2011

On the basis of thin-section sedimentology, 137Cs and 210Pb profiles, and the pronounced seasonality of runoff and sediment delivery, sediments from Nicolay Lake, Cornwall Island, Nunavut (77°46'N, 94°40'W) are interpreted as varves. In thin section, the laminae are conformable, normally graded units of silt and clay. Depending on the location in the lake, the varves frequently contain one or more subannual rhythmites and inclusions of coarse sand and silt grains. Given the unstratified nature of the lake, the rhythmites are interpreted as products of sediment inflow events derived from rainfall, snowmelt, or mass wasting processes. In the most proximal site, these rhythmites may reflect insolation-driven diurnal variations in sediment transport. Isolated coarse grains in the varves are interpreted as eolian sediments washed off the lake ice cover. The lake is currently isothermal, and persistent ice cover and cold inflow prevent the formation of thermal stratification. The high accumulation rate is a critical factor in varve formation and it is probable that increased sediment yield during the past 500 years has led to the formation of varves, compared to the underlying massive mud that accumulated when deposition was focused inland of the lake during higher relative sea level. Evidence in the catchment indicates that high-elevation deglacial deposits have acted as an important fine-grained sediment source throughout the Holocene. These sediments moved progressively downstream through a series of basins by successive degradation and aggradation controlled by glacioisostatic emergence, hence, limiting the progression of this paraglacial sediment wave to areas upstream of the lake until the late Holocene. These results identify the importance of shifting catchment boundary conditions on sediment yield throughout the Holocene, and also indicate the difficulty of interpreting low-frequency yield variations as the direct consequence of changing climate in similar varve records.
Origins of the Zippa Mountain pluton: a Late Triassic, arc-derived, ultrapotassic magma from the Canadian Cordillera
Authors: Coulson Ian M , Russell James K , Dipple Gregory M
Published: April 2011

The Zippa Mountain intrusion is of Late Triassic age and is situated in the Iskut River area of northwest British Columbia. The pluton is elliptical in shape and 3.5 by 5 km in diameter. The pluton intrudes Palaeozoic and Triassic rocks within Stikinia and is compositionally zoned from clinopyroxenite at the pluton margins to a core of syenite. The Zippa Mountain pluton comprises aegirine-augite, potassium feldspar, and minor biotite, hornblende, nepheline, vishnevite, titanian andradite, titanite, and apatite. Based on new field, petrographic, and chemical data this intrusion is shown to be silica-undersaturated, strongly alkaline, and ultrapotassic. We interpret the pluton as a single pulse of magma, which entered a shallow-level crustal magma chamber. The potassic nature is a characteristic of the parental magma, but is enhanced by fractional crystallization and crystal sorting processes. The parental magma has affinities with arc-type magmas related to subduction (shoshonitic magma series), as is evidenced by high LILE/LREE ratio, and select depletion of HFSE. Upon emplacement, crystallization of clinopyroxene and then K-feldspar, and efficient physical sorting within the magma chamber, resulted in sidewall, marginal pyroxenite and roof-zone syenites, respectively. Continued fractionation in the core of the intrusion increased volatile contents and led to the crystallization of feldspathoids. Potentially, a mass of residual melt, and crystals of K-feldspar and feldspathoid, was buoyant relative to the surrounding pyroxenite, which allowed it it to rise and partly intrude the syenites.
Tectonic and thermal history of the Anialik River area, northwestern Slave Province, Canada
Authors: Relf C , Sandeman H A , Villeneuve M E
Published: April 2011

The Anialik River area in the northwestern Slave Province comprises two geological domains of different age and origin that were tectonically juxtaposed at ca. 2650 Ma. The older domain, the Kangguyak gneiss belt, comprises ca. 3300-2700 Ma orthogneisses and paragneisses, interpreted as the remnants of a Mesoarchean continental margin. The younger domain, the Anialik River greenstone belt, consists of ca. 2680 Ma mafic to felsic volcanic rocks interpreted to have formed in an ensimatic island-arc setting. Structural and geochronological evidence suggest collision of the two domains began around 2650 Ma in a transpressive regime that involved oblique (sinistral) subduction of the greenstone belt beneath the Kangguyak domain along the Tokhokatak shear zone. Displacement continued until at least ca. 2600 Ma, when late, two-mica granites intruded along and were deformed in the shear zone. Following ca. 2600 Ma, rocks in both domains and along the fault cooled rapidly to about 350°C. Strongly overprinted muscovite spectra and the young ages for biotite throughout the region imply that a thermal event reset all biotites (but not muscovite) at ca. 2000-1900 Ma, possibly associated with crustal thickening associated with Wopmay (Calderian) orogenesis. The tectonic history of the Anialik River area is significantly different from that documented in the south-central part of the Slave Province, suggesting the Kangguyak domain is a distinct fragment of continental crust that accreted independently from continental crust in the southern Slave Province.
A summary of electromagnetic studies on the Abitibi-Grenville transect
Authors: Boerner David E , Kurtz Ron D , Craven James A
Published: April 2011

Electromagnetic surveys on the Abitibi-Grenville Lithoprobe transect have elucidated a number of conductivity signatures that can be genetically linked to Precambrian tectonic processes. Some major fault zones are moderately conductive, possibly signalling graphite deposition from a mantle CO2 flux along crust-penetrating fault systems. However, conductive (graphitic) metasedimentary rocks characteristic of foreland basins are apparently absent from the transect area. A weak inverse correlation between metamorphic grade and electrical conductivity was observed by following rock units across the Grenville Front into high-grade equivalents within the parautochthonous belt. A uniformly conductive mid-crustal layer extends across the Grenville Front, apparently without change in character. The existence of this ubiquitous mid-crustal conductor has been interpreted to mean that electrical conductivity is controlled by the present-day pressure, temperature, and fluid saturation of the lower crust, independent of ancient structure, mineralogy, or metamorphic grade. Lower crustal (upper mantle?) electrical anisotropy is pervasive across the transect area. An apparent spatial correlation of conductivity anisotropy with Archean tectonic deformation patterns has been interpreted to indicate that the lithosphere has remained intact since the Neoarchean.
Microstratigraphic study of meristic variation in an Eocene fish from a 10 000-year varved interval at Horsefly, British Columbia
Authors: Barton Douglas G , Wilson Mark VH
Published: April 2011

Varved, lacustrine rocks of the Middle Eocene Horsefly deposits in British Columbia are ideal for microstratigraphic studies. Temporal resolution in such varved deposits can theoretically be as small as a year. In the Horsefly beds, specimens can be assigned precisely to their position in the stratigraphic section by comparing the laminations enclosing the fossils with those of a reference section. Each fossil can thus be assigned to a relative year of death. Some 700 specimens of the catostomid fish Amyzon aggregatum from the 10 000-year "H3" varved interval are examined for meristic variation. Very few of the meristic variables are significantly correlated with each other. Meristic series that are the last to develop ontogenetically are also the most phenotypically variable. In the studied interval, meristic variation has a strong temporal component, particularly in the case of fin rays and in the ratio between precaudal and caudal vertebral counts. Much, but not all, of this temporal variation occurs in conjunction with environmental changes in the lake as estimated by taphonomy and is consistent with some combination of ecophenotypic and (or) evolutionary responses of the fish population to the environmental change.
Geochronology and radiogenic isotope geochemistry of plutonic rocks from the central Abitibi subprovince: significance to the internal subdivision and plutono-tectonic evolution of the Abitibi belt
Authors: Davis W J , Lacroix S , Gariépy C , Machado N
Published: April 2011

Nine new U-Pb ages are reported for plutons of the central granite-gneiss zone of the Abitibi belt in Quebec. The large plutonic complex along Lithoprobe seismic reflection line 28 formed by multiple intrusion over at least 40 million years, synchronous with and postdating formation of adjacent volcanic sequences. Ages for the four principal plutons within the complex are: Mistaouac at 2726 ± 2 Ma, Boivin at 2713 ± 2 Ma, Rousseau at 2703 ± 2 Ma, and Paradis at 2686 ± 2 Ma. The latter also constrains deformation within the Laberge deformation zone to be at least in part younger than 2686 Ma. Inherited zircons in the Mistaouac pluton indicate that the oldest pluton formed in significantly older crust (>2.75 Ga), not presently exposed in the area. The La Reine and Waswanapi plutons have ages of ca. 2695 Ma similar to other tonalitic plutons in the area and elsewhere in the Abitibi belt. A syenite pluton deformed within the Douay fault zone, a late fault associated with the Casa Berardi zone, has an age of 2676+6-5 Ma, similar to alkalic plutons associated with the Destor-Porcupine and Cadillac-Larder Lake deformation zones of the southern Abitibi belt. Two samples from the Lac Case pluton yielded monazite ages of 2676 ± 3 and 2660 ± 3 Ma. Nd, Pb, and Sr isotopic compositions for central Abitibi belt plutons show dominantly juvenile sources with minor contributions of older crust in the Lac Case pluton. Although geochronological data for volcanic rocks has been used to suggest that the northern zone is older and magmatic activity youngs to the south, consideration of the ages for plutonic and volcanic rocks does not support such hypothesis. The available data indicate that magmatism occurred throughout the Abitibi subprovince from 2730 to 2685 Ma, permissive of a linked tectono-magmatic evolution for the northern and southern zones.
The simulated response of the climate system to changes in soil moisture parameterization under paleoclimatic boundary conditions at 6000 years before present
Authors: Vettoretti G , Peltier W R , McFarlane N A , groups P M I P participating
Published: April 2011

We present the results of a sensitivity study involving modifications to the simple land surface scheme implemented in the second-generation atmospheric general circulation model (GCMII) of the Canadian Climate Centre for Modelling and Analysis (CCCma), under paleoclimatic boundary conditions characteristic of 6000 calendar years before present (6 ka BP). The land surface parameterization is modified in two primary respects. Firstly, we modify the space dependant bucket depth scheme in the original model to one in which this depth is taken to be constant. Secondly, we modify the evapotranspiration parameterization from the space dependant form employed in the control model to a more conventional space independent scheme. In all, 4 experiments have been performed to enable us to resolve both the modern control and the 6 ka BP response to the land surface modifications. A subset of these simulations is also compared with results obtained using other models in the context of the Paleoclimate Model Intercomparison Project (PMIP) to investigate the mid-latitude behaviour of these models to reveal the extent to which model response to a change in radiative forcing may be significantly influenced by changes in the land surface parameterization. These comparisons reveal that the original Canadian GCMII model is an extreme outlier among the members of the set of all models in that its Northern Hemisphere mid-latitude surface continental response to the 6 ka BP insolation anomaly is significantly cold biased in the summer season. We investigate the extent to which this anomalous behaviour may be explained as a consequence of modifications to the land surface parameterizations employed in GCMII. Our results reveal a strong sensitivity in the modern control model to changes in bucket depth, but not to the modification of the evapotranspiration scheme. More interesting, however, is the fact that the model climate sensitivity at 6 ka BP is influenced both by changes in bucket depth and by changes in the evapotranspiration scheme. A detailed investigation of the surface energy balance, cloud cover, surface albedo, and snow cover reveals the role of each of the components that contribute to the 6 ka BP surface temperature response. Comparison of the predictions of the CCCma model with proxy climate indicators of lake levels and surface temperature over Canada, furthermore, demonstrate the extreme sensitivity of climate predictions for this geographical region to changes in the manner in which land surface processes are represented.
Oxygen isotope evolution of volcanic rocks at the Sturgeon Lake volcanic complex, Ontario
Authors: King E M , Valley J W , Davis D W
Published: April 2011

Igneous zircons from the Sturgeon Lake volcanic complex, host to several massive sulphide deposits in the Superior Province, Canada, have an average δ18O(zircon) of 5.4 ± 0.3 VSMOW (n = 9 rocks). These zircons are from units differing in age by 18 million years in the 2.7 Ga complex. There is no detectable interaction of high δ18O, supracrustal lithologies in the magma. Quartz from volcanic units beneath the largest ore body, the Mattabi deposit, has an average δ18O of 9.3 ± 0.6. Quartz phenocrysts from the Mattabi unit and overlying volcanics have elevated and heterogeneous δ18O values averaging 13.8 ± 0.9 and are not in magmatic equilibrium with zircons. The δ18O values of whole-rock powders range from 5.6 to 14.3 and follow the trend observed in the δ18O values of quartz. Healed microcracks are visible in cathodoluminescence images (but are not obvious optically) of quartz phenocrysts from units with high δ18O values and disequilibrium Δ(quartz-zircon) suggesting that recrystallization facilitates the elevation of δ18O. Quartz phenocrysts from volcanic units with Δ(quartz-zircon) values near equilibrium at magmatic temperatures do not display healed microcracks in cathodoluminescence. The elevated δ18O(quartz) values are not restricted to units hosting orebodies, but are seen in all rocks in the volcanic stratigraphy that postdate eruption of the Mattabi unit. Oxygen isotope ratios combined with physical volcanology studies suggest that impermeable volcanic layers control the size and location of the many hydrothermal systems that may have occurred in the Sturgeon Lake complex.
The subglacial geomorphology of southeast Alberta: evidence for subglacial meltwater erosion
Authors: Beaney Claire L , Shaw John
Published: April 2011

A coherent pattern of landforms in southeast Alberta forms a subglacial landform continuum. Scoured bedrock tracts, flutes, transverse bed forms, and tunnel channels in this continuum are inferred to be products of erosion by turbulent subglacial meltwater flows beneath the Laurentide Ice Sheet. Bedrock and glacigenic sediment are truncated by an erosional surface. Flutes and extensive boulder lags across the truncation surface strongly suggest erosion by high-velocity turbulent flows. Tunnel channels dissect the erosion surface and record channelization of earlier sheet flows. Convex longitudinal profiles of channels indicate subglacial meltwater flow. Northeast-southwest trending transverse bed forms are superimposed on the preglacial divide and may be either glaciotectonic ridges or fluvial bed forms. Landforms reflect the dominance of erosion in the subglacial environment, likely by catastrophic meltwater flows of the Livingstone Lake megaflood event. The subglacial meltwater hypothesis accounts for each of the above landforms observed in southeast Alberta and suggests a less complex subglacial system than hypotheses requiring multiple processes to account for the landforms.
The complexity of the crust and Moho under the southeastern Superior and Grenville provinces of the Canadian Shield from seismic refraction - wide-angle reflection data
Authors: Mereu R F
Published: April 2011

The major features of the individual velocity models, Poisson's ratio values, and crustal complexity derived from the interpretation of seismic data sets from four long-range seismic refraction - wide-angle reflection experiments are summarized. The experiments were conducted from 1982-92 in the southeastern portion of the Canadian Shield. In the conventional analysis of seismic refraction - wide-angle reflection data, only the onset times and amplitudes of the major arrival phases are used to derive seismic velocity models of the region under study. These models are over smoothed, have a number of intermediate discontinuities, are unable to explain the Pg coda, and bear very little resemblance to the models derived from the analysis of near-vertical seismic reflection data. In this paper some of the differences between seismic models derived from near-vertical reflection analysis and those from refraction analysis are reconciled from an analysis of the wide-angle reflection fields of the crustal coda waves that follow the first arrivals. This was done using a migration technique that to a first approximation maps the amplitudes of the record sections into a two-dimensional (2-D) complexity section. These new sections show significant lateral variations in crustal and Moho reflectivity and may be used to complement the 2-D velocity anomaly sections and near-vertical reflection sections. The method was based on a numerical study that showed that the coda can be explained with a class of complex heterogeneous models in which sets of small-scale, high-contrast sloping seismic reflectors are "embedded" in a uniform seismic velocity gradient field.
Interaction among upper crustal, lower crustal, and mantle materials in the Port Mouton pluton, Meguma Lithotectonic Zone, southwest Nova Scotia
Authors: Clarke D Barrie , Fallon Raymond , Heaman Larry M
Published: April 2011

The Port Mouton pluton is unique among the Late Devonian peraluminous granitoid bodies in the Meguma Lithotectonic Zone of southwestern Nova Scotia in its lithological heterogeneity, extensive physical and chemical interaction with the country rocks, clear evidence for mingling and mixing with mafic magmas, and highly abundant pegmatites. New UPb age determinations on monazite establish an intrusion age of 373 ± 1 Ma, similar to the ages of other Meguma Lithotectonic Zone granitoid plutons and mafic intrusions. Field relations, petrology, and geochemistry define three stages of intrusion of the Port Mouton pluton: (i) early stage, discontinuously exposed around the outer margin of the pluton, dominated by coarse-grained tonalite-granodiorite, and with Rb/Sr < 0.55, Eu/Eu* > 0.40, and GdN/LuN < 2; (ii) middle stage, occupying the interior of the pluton, dominated by medium-grained granodiorite-monzogranite, and with Rb/Sr > 0.55, Eu/Eu* < 0.40, and GdN/LuN > 2; and (iii) late stage, consisting of abundant minor sheets throughout the pluton, dominated by fine-grained tonalite, granodiorite, and leucogranite that are similar to rocks of the early and middle stages. The Port Mouton pluton shows a wider range of 87Sr/86Sri (0.7036-0.7154), and a wider range and generally higher εNdi (3.72 to +2.12), than other granitoid rocks in the Meguma Lithotectonic Zone, potentially reflecting a complex, partially equilibrated, interaction among mantle, lower crust, and upper crust. Field, petrological, and chemical evidence for the involvement of mantle-derived magmas and melting of upper crust permit modelling of the Port Mouton pluton granitoid compositions by three simultaneous mixing equations. These mixing model results suggest that the early stage granitoid rocks can form from simple three-component mixing relationships when the bulk distribution coefficients between residuum and melt for Sr and Nd range from 1.05 to 1.18, or two-component mixing combined with fractionation of material like the known felsic lower crust. The middle stage granitoid rocks only yield solutions involving two-component mixing and fractionation of material unlike the known felsic lower crust. We conclude that the Late Devonian mafic magmas played a major role in the formation of granitoid magmas in the Meguma Lithotectonic Zone by supplying heat and material to cause partial fusion of the Avalon lower crust.
Molecular cloning of DNA complementary to Drosophila melanogaster α-amylase mRNA
Authors: Benkel Bernhard F. , Abukashawa Sumaia , Boer Poppo H. , Hickey Donal A.
Published: April 2011

Several lambda clones containing cDNAs from Drosophila melanogaster were identified in a lambda cDNA bank using two different approaches: (i) cross-species hybridization using a mouse amylase cDNA probe, and (ii) probing with a differential probe, generated from Drosophila RNA. An amylase cDNA fragment was used, in turn, for the isolation and characterization of amylase genomic clones. The size of the Drosophila amylase mRNA was estimated at 1650 b. This is comparable with the size of the murine amylase messenger that encodes a protein of similar molecular weight. In Drosophila larvae, amylase mRNA can account for as little as 0.01% of the poly(A)+ RNA under conditions of dietary glucose repression or greater than 1% of poly(A)+ RNA under derepressing dietary conditions.

Key words: Drosophila, amylase cDNA, genomic clones.
Hordeum chilense (2n = 14) computer-assisted Giemsa karyotypes
Authors: Armstrong K. C. , Craig Iris L. , Merritt C.
Published: April 2011

The Giemsa karyotype of three accessions of Hordeum chilense Roem. and Schult were studied in detail. The idiograms were developed using a computer-assisted software program that contained the ability to straighten and measure chromosomes. Distinctive banding patterns were formed on each of the seven chromosome pairs, which in conjunction with length and arm ratio allowed the identification of each chromosome. Some differences in the banding patterns of the accessions were noted.

Key words: Hordeum, chromosome banding.
The phylogeny of the polyploid wheats Triticum aestivum (bread wheat) and Triticum turgidum (macaroni wheat)
Authors: Kerby K. , Kuspira J.
Published: April 2011

The phylogeny of the polyploid wheats has been the subject of intense research and speculation during the past 70 years. Various experimental approaches have been employed to ascertain the diploid progenitors of these wheats. The species having donated the D genome to Triticum aestivum has been unequivocally identified as Aegilops squarrosa. On the basis of evidence from many studies, Triticum monococcum has been implicated as the source of the A genome in both Triticum turgidum and Triticum aestivum. However, numerous studies since 1968 have shown that Triticum urartu is very closely related to Triticum monococcum and that it also carries the A genome. These studies have prompted the speculation that Triticum urartu may be the donor of this chromosome set to the polyploid wheats. The donor of the B genome to Triticum turgidum and Triticum aestivum remains equivocal and controversial. Six different diploid species have been implicated as putative B genome donors: Aegilops bicornis, Aegilops longissima, Aegilops searsii, Aegilops sharonensis, Aegilops speltoides, and Triticum urartu. Until recently, evidence presented by different researchers had not permitted an unequivocal identification of the progenitor of the B genome in polyploid wheats. Recent studies, involving all diploid and polyploid wheats and putative B genome donors, lead to the conclusion that Aegilops speltoides and Triticum urartu can be excluded as B genome donors and that Aegilops searsii is the most likely source of this chromosome set. The possibility of the B genome having arisen from an AAAA autotetraploid or having a polyphyletic origin is discussed.

Key words: phylogeny; Triticum aestivum; Triticum turgidum; A, B, and D genomes.
Genetic variation in three subspecies of Melanoplus sanguinipes (F.). I. Morphometric traits
Authors: Chapco William
Published: April 2011

Samples of three subspecies of Melanoplus sanguinipes (M. s. sanguinipes, M. s. vulturnus, and M. s. defectus), raised under the same laboratory conditions, differ significantly in a number of morphometric traits. The heritable nature of these differences was explored by performing intersubspecific crosses, hybrid crosses, and backcrosses. On the whole, the genetics underlying each trait was complex, with the presence or absence of heterosis, of genic interaction, and of maternal effects being dependent on the strains compared and the sex of the insects.

Key words: Melanoplus sanguinipes, Acrididae, quantitative genetics, morphometric traits.
Topographical changes in rye chromosome ultrastructure caused by the C-banding procedure
Authors: Dille J. E. , Gustafson J. P. , Brown Jr. M. , Appels R. , Craig S.
Published: April 2011

The changes in the surface features of rye chromosome 1 induced by the C-banding procedure was investigated using the scanning electron microscope. Each step in the procedure produced significant changes in the surface topography of the chromosome and minor differences in its general morphology. The most noticeable alteration, chromosomes flattened and smooth, occurred when they were incubated in phosphate buffer without Leishman's stain. Since chromosomes not treated with barium hydroxide were uniformly stained, it seems probable that this alkali removes chromatin unselectively and that the C-bands produced here are due to a differential affinity of the heterochromatin to the stain.

Key words: rye, heterochromatin, C-banding.
Genetic variants in progeny of regenerated maize plants
Authors: Lee Michael , Phillips R. L.
Published: April 2011

Tissue culture has been shown to be a method of generating genetic variation in regenerated plants and their progeny for several maize (Zea mays L.) genotypes. The objectives of this study were to (i) estimate the frequency and types of variants arising from maize tissue cultures, (ii) investigate the effect of culture age on the frequency of variants per regenerated plant, and (iii) estimate the frequency of sectoring among regenerated plants of an F3 from Oh43/A188 genetic background that had not been examined previously for genetic stability in culture. Organogenic callus cultures were initiated from immature F3 embryos for several Oh43ms isoline × A188 crosses. Plants were regenerated either 3 to 4 or 8 to 9 months after culture initiation. Progenies of 248 plants regenerated from 74 cultures were scored for kernel, seedling, and other sporophytic variants following one or two generations of self-pollination. The frequency of variants per regenerated plants increased from 0.5 after 3 to 4 months of culture to 1.3 after 8 to 9 months. A total of 44 variant phenotypes were observed. Defective kernels were the most frequent variant. Most variants were inherited as single-gene recessives. Segregation patterns suggested that the ear and tassel of several (40 of 80) self-pollinated, regenerated plants were genetically discordant.

Key words: Zea mays L., tissue culture, somaclonal variation, chimera, qualitative variation.
Inheritance of organelle DNA in barley and Hordeum × Secale intergeneric hybrids
Authors: Soliman K. , Fedak G. , Allard R. W.
Published: April 2011

Four reciprocal hybrids of Hordeum vulgare (deficiens type) and seven nonreciprocal hybrids resulting from controlled pollination between two Hordeum and three Secale species were assayed for variation in their organelle DNA. The chloroplast and mitochondrial DNAs of these hybrids were distinct. Genetic variability exists within species of the genus Hordeum with organelle transmission being strictly maternal. On the other hand, biparental inheritance was obtained in the intergeneric hybrids involving Hordeum and Secale. There was selective transmission of Secale bands and the number of gene copies transmitted through the pollen was under genetic control. No recombination occurred between the two parental genomes.

Key words: DNA, organelle, intergeneric hybrids, Hordeum Secale.
Ascospore abortion in crosses of Cochliobolus heterostrophus heterozygous for the virulence locus Tox1
Authors: Bronson Charlotte R.
Published: April 2011

Crosses heterozygous for the virulence locus Tox1 show a high frequency of nonrandom ascospore abortion, in addition to a high frequency of random abortion seen in homozygous crosses. In crosses among closely related laboratory strains, the frequency of asci with eight mature, viable spores dropped from 35–47% of asci with mature spores in crosses homozygous for Tox1 to 3–17% in heterozygous crosses. Segregation for alternate alleles of Tox1 was 2:2 in 98% of asci with four viable spores. Patterns of abortion in crosses involving field isolates were similar to the patterns in crosses among laboratory strains. No recombinants between Tox1 and the abortion-inducing factor were detected among 112 progeny of laboratory strains. The results suggest that race T (TOX1) and race O (tox1) strains of C. heterostrophus differ by a chromosome rearrangement, possibly a reciprocal translocation, with a breakpoint at or near Tox1.Key words: fertility, T-toxin, Cochliobolus heterostrophus, Helminthosporium maydis, Bipolaris maydis, Drechslera maydis, chromosome rearrangement, reciprocal translocation.
The chromosome location of four recombinants between Agropyron chromosome 7el2 and a wheat chromosome
Authors: Knott D. R.
Published: April 2011

Four stem rust (Puccinia graminis tritici Eriks. &Henn.) resistant wheat (Triticum aestivum L.) – Agropyron recombinants were analyzed to determine the wheat chromosomes involved. The Agropyron chromosome, 7el2, was known to be homoeologous to the group 7 chromosomes of wheat. Monosomic analysis showed that all four recombinants involved wheat chromosome 7D.Key words: rust resistance, Puccinia, Agropyron, wheat, Triticum, homoeologous recombination.
Proposed provisions for the design of steel beam-columns in S16-2001
Authors: Essa Hesham S , Kennedy DJ Laurie
Published: April 2011

The provisions for the design of steel beam-columns in CSA Standard CAN/S16.1-94 are reviewed and changes are proposed to provide more consistent reliability in the next edition, CAN/CSA-S16-2001. The in-plane strength interaction equations have been checked using plastic-zone finite element analysis based on realistic residual stress patterns and initial imperfections. The same overall format is maintained. P-δ effects have been found to be negligible for members in sway frame. The interaction equation for checking the in-plane strength of sway beam-columns has been modified by taking the factor U1as 1.0 for members in unbraced frames. For weak-axis bending, a new factor β accounts for the effect of the distributed plasticity on stability. The concept of the notional load for sway buckling, also used in Australia and in Eurocode 3, is now applied for all load combinations and not just as a minimum. The upper limit on U2of 1.4 is removed. Examples are given illustrating these changes. A re-analysis of the local buckling experiments of other researchers on Class 2 sections, using a widely accepted buckling criterion, shows that no distinction need be made between Class 1 and 2 section beam-columns, i.e., Class 2 sections are treated as Class 1 sections. The changes in total do not increase the complexity of the standard, but reflect better the behaviour of beam-columns. The standard is aligned more closely with the best international practice.Key words: analysis, beam-column, buckling, compact, design, interaction equation, resistance, stability, steel, sway.
One-way shear strength of large footings
Authors: Adebar Perry
Published: April 2011

Results are presented from 23 shear tests on 1-m deep specimens made of low-strength concrete and tested with shear span-to-effective depth ratios between 1.4 and 2.4 to obtain information that is relevant to the one-way shear strength of footings. Based on these results and other test results from the literature, an amendment is proposed to the 1994 Canadian concrete code one-way shear strength provisions for members without stirrups. In order to account for the beneficial effects of strut-action in deep members such as footings, it is proposed that the reduction in shear strength due to size not be applied to sections located less than 2d from the face of a support or concentrated load when the applied shear introduces compression into the member. The strut-and-tie provisions in the Canadian code, which has stress limits to prevent concrete compression failures, normally should be used to design deep members, but should not be used to design members without minimum stirrups. The proposed revision eliminates the unnecessary increase in footing depths that is needed to meet the one-way shear strength requirements of the 1994 Canadian concrete code.Key words: building codes, footings, reinforced concrete, shear strength, structural design, tests.
Fibre optic sensors in civil engineering structures
Authors: Tennyson R C , Coroy T , Duck G , Manuelpillai G , Mulvihill P , Cooper David JF , Smith PW E , Mufti A A , Jalali S J
Published: April 2011

This paper presents an overview of the development and application of ISIS fibre optic sensor (FOS) technology by the University of Toronto Institute for Aerospace Studies and Department of Electrical and Computer Engineering. The primary focus of this technology has involved the use of fibre Bragg gratings (FBGs) to measure strain and temperature in concrete structures and fibre reinforced plastic (FRP) overwraps applied to concrete structures. A brief review of existing fibre optic sensor configurations and the advantages of using FOS compared to other strain sensors is first presented. Subsequently, the development of new sensor concepts such as a long gauge of arbitrary length, a distributed gauge for measuring local strain gradients, and multiple FBGs on a single fibre optic cable are discussed, with examples of their application to civil engineering structures. In addition, the specialized instruments under development that are essential for obtaining strain information from these sensors are also described. Finally, the issue of wireless remote monitoring of FOS systems is addressed.Key words: fibre optic sensors, Bragg gratings, civil engineering structures, instrumentation.
Fibre reinforced polymer strengthening of the Sainte-Émélie-de-l'Énergie bridge: design, instrumentation, and field testing
Authors: Labossière P , Neale K W , Rochette P , Demers M , Lamothe P , Lapierre P , Desgagné G
Published: April 2011

An experimental research project was undertaken to evaluate the need to strengthen existing reinforced concrete bridges belonging to the Ministère des Transports du Québec. A typical bridge consisting of a single-span bridge with T-shaped sections was identified. Evaluation of the bridge showed that an increase in bending strength and shear strength would be necessary to satisfy current loading conditions and code requirements. The increase in bending strength was obtained by bonding carbon-reinforced composite materials to the underface of the beams, with fibres in the longitudinal direction. External U-shaped stirrups made of glass-reinforced composite materials were installed on the outside faces of the beams in order to increase their shear strength. This paper presents a selection of experimental results initially obtained on T-section beams, scaled 1:3 with respect to the bridge under consideration. The actual reinforcement scheme selected for the bridge is then presented, accompanied by comments on the construction process. Conventional instrumentation and fibre optic sensors were incorporated to the repair work in order to evaluate the behaviour of the bridge, before and after strengthening. Initial results of this ongoing evaluation are presented here.Key words: bridge strengthening, FRP, composite materials, instrumentation, field testing.
Shear rehabilitation of G-girder bridges in Alberta using fibre reinforced polymer sheets
Authors: Deniaud Christophe , Cheng JJ Roger
Published: April 2011

Many bridges were built in Alberta after World War II with type G-girder precast concrete elements. Today, there are approximately 1500 G-girder bridges still in service all over the province. These bridges are typical short span (approximately 6 m long), simply supported, and without shear keys between girders. Structural deficiency of the G-girders, especially in shear, plus the economic constraints of the government demand that an economical and efficient method for rehabilitation of these bridges be developed. A research program at the University of Alberta, in collaboration with Alberta Transportation and Utilities and ISIS Canada, has been established to study the feasibility of using fibre reinforced polymers (FRP) to rehabilitate concrete bridge girders deficient in shear. This paper will address the structural deficiency of the G-girders and present eight full-scale test results from four G-girders removed from existing bridges. Carbon and glass FRP sheets and two repair schemes were used in the rehabilitation. Three commonly used shear strength evaluation methods, strut-and-tie model, modified compression field theory, and grid analysis, are investigated. The loads predicted by these three methods are in good agreement with the experimental results. The shear contribution of the FRP sheets at any angle can be accurately accounted for in the analysis. All three methods are found to be consistent.Key words: analysis, beams, bridges, composite materials, design, fibre reinforced polymers, rehabilitation, reinforced concrete, shear strengthening.
Field inspection and laboratory testing of highway pavement rutting
Authors: Al-Suleiman Turki I , Obaidat Mohammed Taleb , Abdul-Jabbar Ghassan T , Khedaywi Taisir S
Published: April 2011

The main objective of this research was to investigate the contribution of pavement characteristics, traffic, and physical and mechanical properties of asphaltic mixtures to highway pavement rutting. A total of 51 pavement sections from the rural highway network in Jordan were selected for a case study. The average rut depths for these sections were measured and three cores were drilled for comprehensive laboratory testing. The investigation was performed using four approaches. The first approach considered pavement characteristics represented by surface thickness, last overlay thickness, pavement age, and subgrade California bearing ratio. The average annual equivalent single axle load was also included in this approach. The second approach included Marshall test parameters such as stability, flow, stiffness, and Marshall modulus. The third approach dealt with the effect of mixture air voids on rutting. The variables examined in this approach include air void content within the ruts, voids between ruts, voids near the pavement centerline, and the difference between centerline and rut voids. The fourth approach considered the dynamic permanent deformation characteristics of the pavement surface layer represented by the dynamic modulus. Regression analysis techniques were employed to develop statistical relationships between average rut depths and the parameters examined in each individual approach. The combined effect of these significant parameters on pavement rutting was also examined for prediction purposes. Rutting formation was found to be most dependent on the traffic loading, dynamic modulus of the bituminous mixture and its susceptibility to further compaction, and foundation soil strength.Key words: pavement rutting and characteristics, Marshall test, traffic loading, air voids, static creep, dynamic permanent deformation.
Ambient and forced-vibration tests of the Beauharnois suspension bridge
Authors: Paultre P , Proulx J , Bégin T
Published: April 2011

Ambient and forced vibration tests were carried out on the Beauharnois Bridge, a unique, 177-m combined suspension and cable-stayed structure near Montreal. A rehabilitation program was completed on the bridge during which the deck was completely rebuilt with an orthotropic slab on two steel trusses. The rehabilitation program also included the addition of two pairs of stay cables on both towers, creating a hybrid suspension system. The paper presents a series of dynamic tests performed to evaluate the dynamic properties and the dynamic amplification factor (DAF) for the rehabilitated bridge. The experimental program involved the measurement of vertical, transverse, and longitudinal acceleration responses of the deck and tower under ambient and controlled traffic loads. Displacement, strain, and integrated acceleration DAFs were computed under different loading conditions. Modal properties were evaluated and used to correlate a three-dimensional finite element model for the bridge, including nonlinear cable behaviour. The paper discusses the experimental setup and the techniques used to evaluate vibration frequencies, mode shapes, and the DAF. Correlation of numerical dynamic properties and experimental results is also presented. Key words: cable-stayed bridge, dynamic amplification, dynamic testing, numerical correlation, modal analysis, suspension bridge.
Evaluation of ductility and allowable moment redistribution in reinforced concrete structures
Authors: Shakir Adnan , Rogowsky David M
Published: April 2011

Designers can use moment redistribution to reduce the design bending moment envelope. Code provisions for moment redistribution are not entirely rational. They neglect the effects of important parameters on permissible moment redistribution and can be very conservative. To establish a realistic limit on permissible moment redistribution, one needs a rational model for predicting the plastic rotation capacity of critical sections (plastic hinges). This paper presents a model for computing the plastic rotation capacity, θp, and permissible moment redistribution, β, in reinforced concrete beams. Important parameters, affecting θp and β, are identified and incorporated in the model. The model is validated against experimental results and shows good agreement. A comparison of the moment redistribution limits is made between the model and CSA A23.3-94. Although the code provides a reasonable estimate of β for unfavourable combinations of parameters, the code can be very conservative when conditions are favourable for moment redistribution. Deeper beams with closely spaced stirrups allow significantly more moment redistribution than that predicted by the code.Key words: moment redistribution, ductility, plastic rotation capacity, bond-slip, shear cracking, reinforced concrete beams, c/d, ultimate concrete strain.