bluuebunny/crossref_metadata_2025 huggingface dataset:
Phaeosphaeria
Authors: Shoemaker R. A. , Babcock C. E.
Published: September 2007

Six new subgenera are described within the genus Phaeosphaeria, which includes many species parasitic on cereals, grasses, sedges, rushes, and other grasslike plants. In subgenus Fusispora, 10 species are treated, including 4 new species: P. fetanensis, P. franklinensis, P. gigaspora, and P. moravica, all on Juncus. In subgenus Ovispora, 16 species are treated, including 4 new species: P. borealis on Luzula, P. canadensis on Carex, P. cookei on Luzula, and P. tricincta on Juncus. In subgenus Phaeosphaeria, 32 species are treated, including 8 new species: P. annulata on Elymus, P. calderi on Juncus, P. emilii on Carex, P. exarata on Carex, P. fautreyi on Arundo, P. humerata on Juncus, P. lunata on Carex, and P. minima on Deschampsia. In subgenus Sicispora, 28 species are treated, including 9 new species: P. cinnae on Cinna, P. crenata on Carex, P. erikssonii on various grasses, P. guttulata on various grasses, P. heptamera on Bromus, P. huronensis on Dactylis, P. ovei on Agropyron, P. parvograminis on Phalaris, and P. pulchra on Calamagrostis. In subgenus Spathispora, 12 species are treated, including 2 new species: P. michiganenesis on Scirpus and P. robusta on Arctagrostis. In subgenus Vagispora, 16 species are treated, including 3 new species: P. celata on Equisetum, P. gessneri on Spartina, and P. mounceae on Elymus. Detailed descriptions are given for 64 allied but excluded species including 2 new species: Leptosphaeria lassenensis on Allium and Massariosphaeria adrianii on Scirpus. A new genus, Sulcispora, based on S. pleurospora, is described.
Deposition of modern pollen and plant macroremains in a hypersaline prairie lake basin
Authors: Vance R. E. , Mathewes R. W.
Published: September 2007

Comparisons between current vegetation patterns and deposition of modern pollen and plant macroremains in a saline lake basin on the northern Great Plains are used to assess the value of plant remains as indicators of past local vegetation dynamics and lake-level changes. Results indicate that both modern pollen spectra and assemblages of plant macroremains reflect clearly the composition of the local vegetation, whereas plant macroremains best reflect lake size. Cactaceae pollen and seeds are confined to upland prairie deposits. Liguliflorae (Compositae) and Leguminosae pollen, Selaginella densa microspores, and Euphorbia and Cruciferae seeds are more abundant in prairie upland deposits than in shoreline or lacustrine environments. An abundance (> 50%) of Ruppia pollen distinguishes near-shore lake sediments, indicating that this taxon is a useful marker of shallow shoreline environments in saline lakes. Seeds of Chenopodiaceae, Erigeron, Cruciferae, and Cyperaceae, as well as Chara oogonia, are more abundant in near-shore lacustrine sediments than in the central lake area, suggesting that they too are indicators of shoreline proximity. These data are useful for paleobotanical reconstructions of past lake-level dynamics. Key words: saline lakes, Great Plains, pollen, paleobotany, paleohydrology, environmental reconstruction.
The taxonomy and biology of Tryblidiopsis pinastri
Authors: Livsey Susan , Minter D. W.
Published: September 2007

Tryblidiopsis pinastri (Pers.:Fr) P. Karsten, an ascomycete common on twigs and branches of Picea spp. is redescribed and illustrated. Tryblidiopsis piceae Velenovský is synonymized with T. pinastri and other species of Tryblidiopsis are briefly reviewed. The taxonomic position of the genus Tryblidiopsis is reviewed, concluding that it is correctly placed in the order Rhytismatales for which a new and detailed circumscription is provided. Families of that order are briefly discussed, and Tryblidiopsis is disposed in the Rhytismataceae. Tryblidiopsis pinastri is reported from trunk bark of dying mature trees. Aspects of its biology and ecology are discussed. Key words: forest pathology, endophyte, Picea, Tryblidiopsis, Rhytismatales.
Effect of prehelminthosporol, a phytotoxin produced by Bipolaris sorokiniana, on barley roots
Authors: Liljeroth E. , Franzon-Almgren I. , Gustafsson M.
Published: September 2007

The effects of prehelminthosporol, a toxin produced by Bipolaris sorokiniana, were investigated on barley roots. A concentration of 30 μg∙mL−1 prehelminthosporol or higher in nutrient solution significantly increased the rate of nuclear disintegration in the root cortex cells. The toxin also increased leakage of ATP from intact roots of barley seedlings grown in nutrient solution, but the growth rate of the seedlings was not significantly affected. However, diluted filtrate from liquid shake cultures of the fungus inhibited the growth of the seedlings by 21 – 73% over a 5-day period. The results indicate that the toxin may play an important role in pathogenesis by killing or weakening plant cells in advance of the growing hyphae and facilitating nutrient uptake and further growth of the fungus in plant tissue. Different cultivars of barley differed in sensitivity to prehelminthosporol, but sensitivities were not correlated with known levels of resistance to B. sorokiniana. Key words: Cochliobolus sativus, Hordeum vulgare, root cortex, toxin, prehelminthosporol, ATP.
The attachment organ of the parasitic angiosperms Orobanche cumana and O. aegyptiaca and its development
Authors: Joel Daniel M. , Losner-Goshen Dalia
Published: September 2007

Some species of Orobanche are parasitic weeds attacking the roots of various crops and causing extensive damage. The development of the young parasite was investigated using light and electron microscopy. Germinating O. aegyptiaca and O. cumana form a short root, with no root cap, which is covered by a thin cuticle. As soon as the root reaches a host, elongation stops, the apex expands, and peripheral cells become papillate. The extended apex becomes the young attachment organ. The outer papillar surface of the extended apex bears wall protuberances that are encircled with a thick cuticular belt and covered with a thin cuticle. These protuberances secrete a carbohydrate that accumulates in a subcuticular space and is released to the surface, forming a thin adhesive layer that binds the parasite to its host. Bacteria are commonly found in the secretion pool, on the papillae, and in the outer cell walls. The event of attachment of the young parasite to host surface signals a shift from the independent to parasitic phase. This change also includes a shift from the accumulation of lipids to the accumulation of starch. Key words: Orobanche, broomrape, parasitic plants, haustorium, attachment organ, root.
Genetics and cytology of age-related resistance in North American cultivars of cowpea (Vigna unguiculata) to the cowpea rust fungus (Uromyces vignae)
Authors: Heath Michèle C.
Published: September 2007

Increasing leaf age was accompanied by increases in resistance in three incompatible cowpea cultivars inoculated with race 1 of Uromyces vignae and in three of four cultivars that had previously been considered susceptible to race N2. Selected crosses between cultivars suggested that resistance to race 1 was controlled by the same genes in young and old leaves, and they indicated that age-related resistance to race N2 was primarily controlled by a single, and different, gene in each cultivar. All examples of resistance were expressed cytologically as a range of infection site types in a single leaf, the frequency distribution of which was affected by the type of resistance gene, gene heterozygosity, and leaf age. These frequency distributions shifted with increasing leaf age towards infection sites with less fungal growth and more rapid plant cell necrosis, often abolishing the cytological differences between cultivars and genotypes seen in younger plants. The data suggest that each rust resistance gene in cowpea can generate a range of infection site types, and that fungal growth and plant responses at each infection site are governed by a combination of the number and type of resistance genes in the plant, the race of the fungus, and age-affected features of individual plant cells. Key words: cowpea, rust fungi, age-related resistance.
Ecological growth response specificity of two Douglas-fir ecotypes inoculated with coexistent beneficial rhizosphere bacteria
Authors: Chanway C. P. , Holl F. B.
Published: September 2007

The influence of inoculation with rhizosphere bacteria on Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedling emergence in a controlled environment and on survival and growth in the field was investigated. Seed or seedlings of interior and coastal Douglas-fir ecotypes originating from the vicinity of Williams Lake and Chilliwack, British Columbia, Canada, respectively, were inoculated with two strains of rhizosphere bacteria, Arthrobacter oxydans strain N74 and Pseudomonas aureofaciens strain K23. These strains were previously isolated from naturally regenerating Douglas-fir seedlings collected from the Williams Lake and Chilliwack sites, respectively. Seed inoculation with either strain of bacteria, K23 or N74, stimulated the rate of seedling emergence, but these effects were not ecotype specific. While inoculation did not affect germination percentage, ecotype-specific seedling growth responses were detected 13 months after field planting. Arthrobacter oxydans strain N74 significantly stimulated seedling branching and enhanced root and shoot dry weight of the Williams Lake ecotype but had no significant stimulatory effect on growth of the Chilliwack ecotype. Pseudomonas aureofaciens strain K23 significantly stimulated shoot branching and root dry weight of Chilliwack Douglas-fir but had no significant stimulatory effect on growth of that from Williams Lake. When treatments of Douglas-fir seedlings and rhizosphere bacteria that originated from the same geographic site were pooled and compared with uninoculated controls, significant increases in shoot branch number and root dry weight were also detected. No significant difference in seedling growth was detected when treatments of seedlings and bacteria that originated from different sites were pooled and compared with uninoculated controls. Based on these results, we hypothesize that plant–microbe specificity may be an important component of Douglas-fir – beneficial rhizosphere bacteria interactions in the field. Key words: Douglas-fir seedlings, emergence, growth, rhizosphere bacteria, inoculation.
Microchaete robinsonii sp.nov., a new heteropolar cyanoprokaryote (cyanophyte, cyanobacterium) from southern Manitoba, Canada
Authors: Komárek Jirí
Published: September 2007

A new heteropolar nostocalean cyanoprokaryote Microchaete robinsonii sp.nov. is described from the benthic periphytic assemblage found on stones in the eutrophic Souris River near Dunclody in southwestern Manitoba, Canada. This species belongs to the group of species with narrow trichomes attenuated to the apex but never forming hairs. The morphology of this species is described and its taxonomic position within the genus Microchaete is presented. It differs from other Microchaete species by morphology of filaments, trichomes and sheaths, dimensions, mode of disintegration of trichomes into hormogonia, and its ecology. The morphological features of heteropolar nostocalean genera useful in generic delimitation are reviewed and discussed. Key words: cyanoprokaryotes, Microchaete, new species, rivers, periphyton, Canada.
Molecular genetic approaches to leaf development: Knotted and beyond
Authors: Smith Laurie G. , Hake Sarah
Published: September 2007

Molecular genetics provides a promising alternative to other experimental approaches for furthering our understanding of the mechanisms controlling leaf development. We investigated the molecular basis of dominant Knotted (Kn1) mutations in maize, which cause cells associated with the lateral veins of the leaf blade to acquire characteristics of sheath or auricle and sporadically form outgrowths called knots. The kn1 gene encodes a homeodomain, a DNA-binding domain shared by many transcription factors that regulate developmental processes in animals and fungi. In normal plants, the expression of kn1 is confined to the shoot apex, but in Kn1 mutants, the gene is also expressed ectopically in the veins of developing leaves, apparently causing cells to change their developmental fates. The kn1 gene may function in the shoot apex of normal plants to promote indeterminate growth. Consistent with this hypothesis, when kn1 is expressed constitutively at high levels in the leaves of transgenic tobacco, shoots are formed on the leaf surface. Thus, our results indicate that while the kn1 gene may normally have no function in leaf development, it can alter the development of maize and tobacco leaves when it is expressed in the leaf inappropriately. Genes that normally play a role in leaf development are more likely to be defined by recessive mutations that alter leaf morphogenesis and histogenesis. Key words: leaf development, molecular genetics, Knotted.
Morphological and anatomical development in the Vitaceae. VI. Cissus antarctica
Authors: Gerrath Jean M. , Posluszny Usher
Published: September 2007

The developmental morphology of Cissus antarctica Vent, was followed from seed to seed. As in the other taxa in the family we have examined (Vitis, Parthenocissus, Ampelopsis), both leaves and uncommitted primordia arise on the flank of the apical meristem. Also as in the other taxa, the uncommitted primordium may develop into either a tendril, an inflorescence, or an intermediate organ. An abaxial bract forms on the uncommitted primordium. If the primordium is going to develop into an inflorescence, the lateral arm develops in the axil of the bract. A second order inflorescence arm may also form and it is on these two axillary structures that most of the flowers develop. Each arm of the inflorescence forms a compound series of dichasia, with each dichasium oriented at 90° from the previous one. Flowers are tetramerous. The first two sepals are initiated at approximately 90° to the last-formed inflorescence branch primordium, in the same position as the dichasial bracts would form. Thus the early distinction between a floral and an inflorescence branch primordium is very difficult. A ring primordium then forms and the calyx becomes continuous. The petals arise simultaneously, followed by the stamens, which are petal-opposed. Thus there is no common petal–stamen primordium. The gynoecium arises as a ring primordium, and subsequently two septa form opposite one another on its inner wall. The septa touch, but they do not fuse. Two ovules form at the base of each septum. A floral nectary develops from the ovary base. At anthesis, the greenish petals reflex, usually for a day or less and then are shed, along with the stamens. Fruits are dark bluish and are usually one-seeded. Key words: development, flowers, Vitaceae, Cissus, morphology.
Expression of shoot features in early leaf development of Murraya paniculata (Rutaceae)
Authors: Lacroix Christian R. , Sattler Rolf
Published: September 2007

The early development of the pinnately compound leaves in Murraya paniculata was studied using both epi-illumination and scanning electron microscopy as well as semithin plastic sectioning of the same specimens that were illustrated by means of epi-illumination. It is shown that morphological conclusions may be influenced by technical approaches such as the plane of sectioning. If the developing leaves are sectioned in the (median) sagittal plane, they appear to be rather different from stems and shoots. If, however, they are sectioned in the frontal plane, perpendicular to the sagittal plane, they appear more shoot-like in early development. Their apex could be described in terms of a tunica-corpus organization and the leaflet primordia are initiated like leaf primordia on a shoot tip with distichous phyllotaxy sensu lato. Subsequently, due to differential growth, reorientation of the leaflets occurs in one plane. Thus, the planar structure of the pinnate leaf is ontogenetically secondary. From a phylogenetic perspective, at least two conclusions are possible for plants with pinnate leaves such as those of Murraya: (i) if the ancestor of a pinnate taxon had simple leaves, the pinnate condition arose through homeosis, i.e., the expression of shoot features in leaf sites; (ii) if the ancestor of a pinnate taxon did not have simple leaves, the shoot-like early development of the pinnate leaves may indicate a common evolutionary basis of shoots and pinnate leaves in primitive branching systems. Since it is generally thought that the most primitive angiosperms have simple leaves, the homeotic hypothesis appears to be the preferred hypothesis for the origin of compound leaves in flowering plants. Key words: leaf development, comparative morphogenesis, shoot–leaf relationships, partial shoot theory of the leaf, homeosis.
Spore germination in the Psilotaceae
Authors: Whittier Dean P. , Braggins John E.
Published: September 2007

Spores of several species of Psilotum and Tmesipteris were sown on a nutrient medium containing minerals and 0.2% glucose. The nutrient medium contained ammonium as the nitrogen source and lacked nitrate. From 52 to 98% of the spores of P. nudum, P. complanatum, T. lanceolata, and T. sigmatifolia germinated after 6 months in the dark. Haploid spores of P. nudum began germinating in less than 2 months; however spores of the two Tmesipteris species reached 50% germination sooner than those of the Psilotum species. Spores of T. tannensis never germinated and those of T. elongata and P. × intermedium rarely germinated (<0.1%) and never formed mature gametophytes. Spores from only one species, T. lanceolata, occasionally germinated in the light, but gametophytic development never proceeded beyond the two-celled stage. Spores of T. lanceolata and T. sigmatifolia stored at −70 °C for 21 months germinated essentially as well as the fresh spores. The nutrient medium appears suitable for studies on gametophytes of the Psilotaceae because it promoted spore germination and gametophytic growth for most of the species tested. Key words: Psilotum, Tmesipteris, spore, germination.
Modeling the architecture of expanding Fraxinus pennsylvanica shoots using L-systems
Authors: Prusinkiewicz P. W. , Remphrey W. R. , Davidson C. G. , Hammel M. S.
Published: September 2007

This paper presents a mathematical model of Fraxinus pennsylvanica (green ash) shoots, which yields realistic computer graphics images of shoot geometry, and makes it possible to visualize shoot expansion using computer animation. The model is based on the mathematical formalism of Lindenmayer systems (L-systems). The paper emphasizes the process of model construction, with the aim of making the methodology applicable to other plant species. The central issue is the identification of field data necessary to build a comprehensive developmental model of plant architecture. Key words: Fraxinus pennsylvanica, plant architecture, shoot expansion, modeling, L-system, computer graphics.
Développement et phyllotaxie de l'inflorescence du Symplocarpus foetidus (Araceae)
Authors: Barabé Denis
Published: September 2007

The inflorescence of Symplocarpus foetidus constitutes good material to analyse the biological processes and physical constraints involved in the development of plants. At the adult stage, the inflorescence has an ovoid form. It contains about 65 flowers with a pentagonal or hexagonal form. The floral primordia appears in alternate rows from the basal to the upper part of the inflorescence. Growth zones can be recognized, but it is not possible to determine the exact order of appearance of successive flowers. The phyllotactic systems observed are 5(2,3), 4(3,4), 2(4,3), 6(1,2), and (9,8). The form of the inflorescence changes during growth. In the early stages, when the floral primordia appear, the inflorescence is as wide as long. Afterwards, it becomes longer than wide. The younger primordia have a circular form that they lose when the floral organs begin to grow. The contact parastichies are recognized during the first stages of development but, as the floral parts begin to grow, the phyllotactic system loses its regularity. During the development of the inflorescence, two morphogenetic periods can be distinguished (i) before and (ii) during and after the initiation of floral parts. During the first period, when the floral primordia appear, the phyllotactic system could be explained by global processes at the inflorescence level. During the second period, the development of floral parts produces patterns which can be explained by local processes at the floral level. In this analysis, the author defines the concepts of open system and closed system in phyllotaxis. In a closed system (e.g., spadix), the elements are arranged on a continuous and closed surface. In an open system (e.g., shoot apex), the elements appear on a surface periodically renewed and are spaced by the intercalary growth. Key words: angiosperms, morphogenesis, phyllotaxis, development, model.
Possibilité nouvelle de comparer les formes végétatives par analyse en composantes principales
Authors: Jeune Bernard
Published: September 2007

Principal components analysis allows for the translation of forms, from a single cell to a whole plant, within a specific space. Comparison of structures and of plants, contemporary or not, can be made with this method. The author proposes a specific technique (division of the plant in morphological blocks fitting into each other) to enlarge the field of application of the principal components analysis leading to continuist and process morphology. Key words: principal components analysis, process morphology, continuist morphology, morphological blocks. [Journal translation]
Study of information technology development for the Canadian construction industry
Authors: Froese Thomas , Han Zonghai , Alldritt Michael
Published: September 2007

This paper studies the state of companies that develop information technology (IT) for the construction industry in Canada. The study collects survey results and other data about these companies. It explores the number and nature of companies; their products and markets; and their opinions about IT trends, opportunities and barriers, and collaboration with government and university resources. The study concludes that a small construction IT industry exists in Canada, with some established successful companies and a number of younger ventures. These companies offer some products on par with the best construction IT in other countries, but they fall somewhat behind other countries in forming an advanced construction IT community of practice.Key words: information technology, development, construction industry, survey, Canada.
Finite element studies of reinforced concrete slab - edge column connections with openings
Authors: Guan Hong , Polak Maria Anna
Published: September 2007

An extended nonlinear layered finite element method (LFEM) is used to investigate the influence of openings and shear stud reinforcement (SSR) on the behaviour of reinforced concrete slab – edge column connections. In all, ten large-scale slab – edge column connections tested previously are analyzed. The laboratory test variables were the size and location of the openings in the vicinity of an edge column and the existence of SSR. The numerical results of the load–deflection response, the ultimate strength, and the crack patterns are compared with the experimental findings and good agreement is achieved. A numerical study on two connections is also carried out to determine the influence of the locations of opening in slab – edge column connections with SSR. Discussion on code provisions for slabs with openings is provided. The comparative and numerical studies confirm the accuracy, reliability, and effectiveness of the LFEM in the analysis of slab – edge column connections with both openings and SSR.Key words:slab–column connection, punching shear, opening, shear stud reinforcement, finite element analysis.
Tornado hazard assessment for southern Ontario
Authors: Banik S S , Hong H P , Kopp G A
Published: September 2007

Southern Ontario experiences a number of natural hazards including tornado. However, quantitative tornado hazard assessment in terms of annual probability of exceeding a given wind speed has not been reported for this region. To carry out such a tornado hazard assessment, a statistical characterization of tornado parameters in southern Ontario has been developed using the tornado database of Ontario and that of the neighbouring regions in the United States. These parameters include the tornado occurrence rate, intensity, path length and width, and motion direction. Using the developed statistics and an existing wind field model, a probabilistic assessment of the tornado hazard in terms of wind speed is obtained for southern Ontario. The analysis suggests that for point-like structures such as residential structures, which are usually designed for a 30 year return period wind speed with a load factor of 1.5, the probability that a tornado wind speed exceeds the factored 30 year wind is very low. However, for line structures or elongated systems such as transmission lines, the tornado hazard becomes significant and increases with an increase in the length of the system. Key words: tornado hazard, wind speed, transmission line, probability, wind field, southern Ontario.
Reliability-based optimal design software for earthquake engineering applications
Authors: Liang Hong , Haukaas Terje , Royset Johannes O
Published: September 2007

This paper describes a functional tool for engineers to make rational design decisions by balancing cost and safety. Focus is on seismic design, in which nonlinear structural response must be considered. For this purpose, we implement and apply a state-of-the-art algorithm for reliability-based design optimization. The work extends the OpenSees software, which is rapidly gaining users in the earthquake engineering community. Consequently, design optimization with sophisticated nonlinear finite element models of real structures is possible. An object-oriented software architecture is employed that focuses on maintainability and extensibility of the software. This approach also offers flexibility in the choice of optimization and reliability methods for each specific problem, supported by the decoupled nature of the optimization algorithm. Our work utilizes and extends the existing tools for structural reliability analysis in OpenSees. In particular, we employ response sensitivities that are computed within the finite element code by direct differentiation. The implementation is tested through case studies with nonlinear structural response. Discontinuous response gradients are overcome by use of fibre cross sections and smoothed material models. The numerical examples include the seismic design optimization of a six-storey, three-bay, reinforced concrete building. Key words: reliability-based design optimization, nonlinear finite elements, earthquake engineering, object-oriented software development, OpenSees.
Performance assessment of reinforced concrete bridge columns using a damage index
Authors: Kim Tae-Hoon , Kim Young-Jin , Kang Hyeong-Taek , Shin Hyun Mock
Published: September 2007

A procedure is presented for assessment of the performance of reinforced concrete bridge columns. Fourteen circular reinforced concrete bridge columns were tested under a constant axial load and a cyclically reversed horizontal load. A computer program, named RCAHEST (reinforced concrete analysis in higher evaluation system technology), was used to analyze these reinforced concrete structures. A damage index based on the predicted hysteretic behavior of a reinforced concrete bridge column was used. Damage indices aim to provide a means of quantifying numerically the performance level of reinforced concrete bridge columns under earthquake loading. The proposed numerical method for the performance assessment of reinforced concrete bridge columns was verified by comparison with the experimental results. Key words: assessment procedure, reinforced concrete bridge columns, damage index, hysteretic behavior, performance level.
Influence of pavement surface noise: the Korea Highway Corporation test road
Authors: Mun Sungho , Cho Dae Seung , Choi Tae Muk
Published: September 2007

Because of a significant increase in the number of vehicles using national highway networks that link major urban centers, road traffic noise—with its harmful impact on the environment—has become a major pavement system issue. Therefore, it is necessary to assess the characteristics of different types of pavement and their influence on road traffic noise. The Korea Highway Corporation test road, with eight different pavement surfaces, was used to test and analyze noise from tire–pavement interaction and from vehicle power trains. Noise was measured in a novel test approach using a surface microphone. The results show that traffic noise levels vary widely according to pavement surface type, vehicle type, and vehicle speed. The findings of this investigation can be used to determine appropriate pavement surfaces that will satisfy specific environmental impact assessments for given traffic conditions and requirements.Key words: road traffic noise, tire–pavement noise, power-train noise, surface microphone.
Effect of micro air void system on the permeability of latex-modified concretes with ordinary Portland and very early strength cements
Authors: Yun K K , Kim D H , Kim K J
Published: September 2007

This study focused on the impact of the micro air void system on the chloride permeability of latex-modified concretes with ordinary Portland and very early strength cements. The micro air void system was analyzed with the image analysis method. The results of this study will help field engineers and researchers gain a better understanding of the chloride permeability characteristics of latex-modified concretes. The results show that the latex-modified concretes made with both Portland and very early strength cements have more micro air voids, ranging 50 to 500 µm, than ordinary concretes. These small air voids decrease the spacing factor, which is defined as half the average distance that unstable water must travel to reach an escape boundary. The specific surface ranges from 8 to 27 mm–1 and the spacing factor ranges from 275 to 602 µm for ordinary Portland and very early strength cement concretes without and with latex modification. The specific surface tends to decrease as the spacing factor increases. The spacing factors of concretes tend to decrease with latex modification and with very early strength cement. It seems clear that the use of polymer latex in concrete can significantly lower the value of the air void spacing factor by entraining a large number of micro air voids (below 100 µm in diameter). Key words: latex-modified concrete (LMC), micro air void system, chloride permeability, image analysis.
Theoretical and experimental studies on repaired and rehabilitated reinforced concrete frames
Authors: Li Yeou-Fong , Lin Yan-Jie , Chen Cheng-Wei , Lin Chih-Tsung
Published: September 2007

In this paper, an effective repair and rehabilitation working method is proposed for moderately damaged reinforced concrete (RC) building structures after major earthquakes. Three RC frames with nil, half-height, and full-height brick walls are designed and tested at the National Center for Research on Earthquake Engineering (NCREE), Taiwan. After the columns of these nonductile RC frames are damaged, steel wire cables with nonshrinkage mortar are used to repair the damaged columns, and carbon fiber reinforced polymers (CFRP) are used to rehabilitate the damaged columns. A stress–strain relationship of the confined concrete is used in the theoretical sectional analysis. The columns are confined by steel wires and CFRP, and the "equivalent column model" is proposed in this paper and used to analyze the brick walls inside the RC frames. The analytical results can reasonably predict the lateral force–displacement relationships of these RC frames. Key words: nonductile frame, carbon fiber reinforced polymers, steel wire cable, repair, rehabilitation.
Two new types of bridges: under-deck cable-stayed bridges and combined cable-stayed bridges — the state of the art
Authors: Ruiz-Teran A M , Aparicio A C
Published: September 2007

At least 20 cable-stayed bridges have been built over the last 30 years that cannot be classified under existing typologies for cable-stayed bridges. These structures represent two new types of cable-stayed bridges that we herein define as "under-deck cable-stayed bridges" and "combined cable-stayed bridges." The evolution of these new bridge types is explored through consideration of the different proposals and structures that have been built throughout this period, pointing out the innovations made in each of them. In this paper we propose a new classification system for bridges prestressed by means of tendons into which these two new bridge types will fit. Studies that have been made of these structural types are also highlighted. On the basis of the aforementioned, we describe the state-of-the-art for these structural types, compiling and cataloguing information, documents, and knowledge that were previously highly dispersed. Lastly, we make a critical analysis of the current situation and draw some key conclusions.Key words: under-deck cable-staying, combined cable-staying, cable-stayed bridges, extradosed prestressing, intradosed prestressing, prestressing.
Life-cycle cost assessment model for fiber reinforced polymer bridge deck panels
Authors: Hong TaeHoon , Hastak Makarand
Published: September 2007

To enhance the application of fiber reinforced polymer (FRP) bridge deck panels in the infrastructure area, a practical method is required that would allow probable assessment of the life-cycle cost of advanced composite applications in construction compared with that of conventional materials, at various discount rates, while integrating the available reference data. The overall objective of this research is to develop a performance-based probable life-cycle cost assessment model for FRP bridge deck panels. The life-cycle cost assessment model for FRP bridge deck panels comprises a life-cycle performance module (module-1) and a life-cycle cost optimization module (module-2). The model thus developed in this paper can then be used for other applications of composites in construction. The objective of module-1 is to develop an analytical model that is capable of predicting the structural deterioration over time to assess the deterioration rating per year of FRP bridge deck panels. The objective of module-2 is to develop an analytical model that is capable of assessing the optimal life-cycle cost of FRP bridge deck panels. Three case studies were conducted to validate the logic and results of the process algorithm for the life-cycle cost assessment. The model will be very helpful for the construction industry in evaluating various material options and to justify or deny the feasibility of using composite materials on specific construction projects. Since the life-cycle cost assessment of composite materials in construction has not been dealt with as proposed, it is anticipated that many of the procedures and systems mentioned would include fundamental research and possible innovations.Key words: fiber reinforced materials, Monte Carlo method, life-cycle cost, performance valuation.
Real-time decision support for planning concrete plant operations enabled by integrating vehicle tracking technology, simulation, and optimization algorithms
Authors: Lu Ming , Dai Fei , Chen Wu
Published: September 2007

By integrating the vehicle tracking system, discrete-event simulation algorithm, and evolutionary optimization algorithm, we developed HKCONSIM-Realtime, a decision-support platform created specifically for handling ready-mixed concrete operations. This platform is capable of (1) tracking the positions of concrete trucks and monitoring the motion and status of concrete deliveries in real time, (2) transforming the tracking records into data that provide updated input to simulation, and (3) optimizing the operations and logistics of concrete production based on simulation of the production system using the most current data. This paper presents an overview of the design and development of (1) the hardware and software modules, (2) the data flow and processing throughout the system, and (3) the role of the system in providing interactive, effective support for the human operator to attain cost efficiency. Case studies are given to demonstrate the functionality and application of the prototype system. Key words: simulation, optimization, vehicle tracking, construction planning, ready-mixed concrete, Hong Kong.
Variations des efforts hydrodynamiques sur radiers horizontal et affouillé en aval d'un dissipateur d'énergie de type auge
Authors: Amri A El , Verrette J L
Published: September 2007

The distribution of the hydrodynamic efforts under solid horizontal or scoured bed downstream of a roller bucket spillway can be represented by two typical distributions: type A and B for pressure and type I and II for pressure fluctuation. However, the scoured bed presents a pressure distribution that is closer to the equilibrium pressure compared with that of the horizontal bed and a much lower pressure fluctuation distribution. This could be due to the bed scour in the vicinity of the bucket that carries an effective value for the height of the bucket lip, which decreases the suction effect, and the fact that the eroded shape of the bed corresponds with reduced pressure efforts, which translates into weaker turbulence and therefore a more stable flow. These results show the advantage of a scoured bed that could be more secure when the bucket lip height of the roller bucket spillway is well chosen.Key words: hydrodynamic efforts, pressure, pressure fluctuation, hydraulic energy dissipation, roller bucket.
Increased metabolic potential of Rhizobium spp. is associated with bacterial competitiveness
Authors: Wielbo Jerzy , Marek-Kozaczuk Monika , Kubik-Komar Agnieszka , Skorupska Anna
Published: September 2007

Of 105 rhizobial isolates obtained from nodules of commonly cultivated legumes, we selected 19 strains on the basis of a high rate of symbiotic plant growth promotion. Individual strains within the species Rhizobium leguminosarum bv. trifolii , R. leguminosarum bv. viciae , and Rhizobium etli displayed variation not only in plasmid sizes and numbers but also in the chromosomal 16S–23S internal transcribed spacer. The strains were tagged with gusA gene and their competitiveness was examined in relation to an indigenous population of rhizobia under greenhouse conditions. A group of 9 strains was thus isolated that were competitive in relation to native rhizobia in pot experiments. Nineteen selected competitive and uncompetitive strains were examined with respect to their ability to utilize various carbon and energy sources by means of commercial Biolog GN2 microplate test. The ability of the selected strains to metabolize a wide range of nutrients differed markedly and the competitive strains were able to utilize more carbon and energy sources than uncompetitive ones. A major difference concerned the utilization of amino and organic acids, which were metabolized by most of the competitive and only a few uncompetitive strains, whereas sugars and their derivatives were commonly utilized by both groups of strains. A statistically significant correlation between the ability to metabolize a broad range of substrates and nodulation competitiveness was found, indicating that metabolic properties may be an essential trait in determining the competitiveness of rhizobia.
Oxidative burst induced pseudosclerotium formation ofMorchella steppicolaZerova on different malt agar media
Authors: Király I. , Czövek P.
Published: September 2007

Morchella steppicola Zerova mycelia was grown on modified MS (MSK) medium and on MSK medium containing different malt content. Starvation induced an enhanced pseudosclerotium formation in a given zone of the culture. The malondialdehyde content of the mycelium at the site of pseudosclerotium formation was related to the acceleration of lipid peroxidation and oxidative stress. Superoxide dismutase activity was monitored in control and stressed vegetative hyphae subjected to malt withdrawal. In the formation zone of resting bodies, an enhanced oxidative burst was observed. The glucose and trehalose contents of M. steppicola mycelium during pseudosclerotium formation were also investigated. The glucose concentration of the mycelia approached a minimum during pseudosclerotium formation. At the same time, trehalose concentration reached a maximum in the zone of pseudosclerotium formation. The dry mass of mycelia in these zones was higher than average. The dry matter content of the pseudosclerotium-forming zones significantly exceeded the average of the whole culture. The correlation among trehalose accumulation, oxidative burst, and pseudosclerotium formation was clearly demonstrated.
Iron effects on colonization behavior, motility, and enzymatic activity of marine bacteria
Authors: Tang Kam W. , Grossart Hans-Peter
Published: September 2007

Iron availability in the ocean has been shown to affect the growth and production of phytoplankton and free-living bacteria. A large fraction of marine bacteria are specialized in colonizing and living on particles and aggregates, but the effects of iron limitation on these bacteria are not fully known. We conducted laboratory experiments to study the effects of iron availability on particle colonization behavior, motility, and enzymatic activities of 4 strains of marine bacteria. Iron depletion reduced the bacterial particle colonization rate by 1.7%–43.1%, which could be attributed to reduced swimming speeds in 2 of the 4 strains. Protease activity was not affected by iron availability. However, attached bacteria did show higher protease activities than their free counterparts. Our results suggest that iron limitation in the ocean could in some cases reduce bacteria–particle interactions by reducing bacterial motility and colonization rate.
Phenotypic and genetic analysis of Enterobacter spp. from a Brazilian oligotrophic freshwater lake
Authors: Pontes Daniela Santos , Lima-Bittencourt Cláudia Iracema , Azevedo Marcela Santiago Pacheco , Chartone-Souza Edmar , Nascimento Andréa Maria Amaral
Published: September 2007

We characterized a population of Enterobacter spp. of the Enterobacter cloacae complex isolated from an oligotrophic lake; most isolates were identified as E. cloacae. Fingerprinting polymerase chain reaction (PCR), along with morphological, biochemical, physiological, and plasmid profiles analyses, including antimicrobial susceptibility testing, were performed on 22 environmental isolates. Misidentification occurred when using the API 20E identification system. Analysis of 16S rDNA sequences confirmed the close relatedness between species of the E. cloacae complex. The tDNA PCR allowed the differentiation and identification of the E. cloacae isolates. Evaluation of genetic diversity by 16S rDNA sequence, tDNA, internal transcribed spacers, and enterobacterial repetitive intergenic concensus profiles revealed nearly identical isolates, although they exhibited different physiological and antimicrobial resistance profiles. Among the Enterobacter isolates, 96% were resistant to at least one antimicrobial; multiple resistance was also found at a high frequency (86%). The antimicrobials against which resistance was found most frequently were β-lactams, chloramphenicol, and streptomycin. Plasmids were found in 21 of the 22 Enterobacter isolates. This confirms the conception that antibiotic resistance can occur in oligotrophic freshwater lake bacteria, which has important implications for public health.
Molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) isolates from major hospitals in Riyadh, Saudi Arabia
Authors: Baddour Manal M. , Abuelkheir Manal M. , Fatani Amal J. , Bohol Marie F. , Al-Ahdal Mohammad N.
Published: September 2007

The few studies that have reported the incidence of methicillin-resistant Staphylococcus aureus (MRSA) in Saudi Arabia have indicated that a diverse number of circulating MRSA strains have been detected in several major hospitals. Thus, this study was designed to track the presence of MRSA strains in major hospitals in Riyadh, Saudi Arabia, and perform comparative chromosomal DNA analysis of MRSA strains for epidemiological investigation using pulsed-field gel electrophoresis (PFGE). Correlation of the PFGE types generated with microbiological and clinical data of the isolates was attempted. Screening for decreased susceptibility to vancomycin among the isolates was also done. A dendogram was generated using PFGE macrorestriction fragments and 6 types were identified (M1–M6) with M1 being predominant and widespread. A clear link between PFGE types and some clinical and microbiological data available for the strains was found. For example, M1 was statistically associated with male patients, whereas the unique types were associated with female patients, M2 was associated with isolates from wounds and age group <5 years, and M4 was associated with isolates from patients admitted to intensive care units. M5 was highly correlated with low sensitivity to linezolid. No vancomycin-resistant isolates were detected.
Differential regulation of interchromosomal copies of ToxR-induced genes
Authors: Nag Sanjay , Chaudhuri Keya
Published: September 2007

In Vibrio cholerae , ToxR transcriptionally activates a number of virulence genes in response to various environmental signals. In the present study, transcription profiling by macroarray was carried out with 13 pairs of genes, one copy of which is present in each chromosome under ToxR-inducing (pH 6.5, osmolarity 66 mmol/L, 30 °C) and ToxR-repressing (pH 8.5, osmolarity 300 mmol/L, 37 °C) conditions followed by high pH (8.5) and low pH (6.5) conditions to eliminate pH effect. The genes dacAII, tagEII, secDII, pmmI, pmmII, and immII showed increased expression in the ToxR-inducing conditions, but not at low pH, suggesting that the expression of these genes might be regulated by ToxR. The expression of pmmII, dacAII, tagEII, secDII, and immII genes decreased significantly in the toxR insertion mutant as determined by RT–PCR, whereas the expression of the chromosome I copy of pmm increased in toxR mutant compared with wild-type cells. Thus, the chromosome II copy of these genes, which show increased expression under ToxR-inducing conditions, are all regulated by ToxR in V. cholerae, whereas the chromosome I copy of pmm may be regulated by other factors under ToxR-inducing conditions.
Overexpression of a metacaspase gene stimulates cell growth and stress response inSchizosaccharomyces pombe
Authors: Lim Hye-Won , Kim Su-Jung , Park Eun-Hee , Lim Chang-Jin
Published: September 2007

A unique gene named pca1+, encoding a metacaspase, was cloned from the fission yeast Schizosaccharomyces pombe and was used to create a recombinant plasmid, pPMC. The metacaspase mRNA level was markedly elevated in the fission yeast cells harboring the plasmid pPMC. Overexpressed Pca1+appeared to stimulate the growth of the fission yeast cells instead of arresting their growth. Its expression was enhanced by stress-inducing agents such as H2O2, sodium nitroprusside, and CdCl2, and it conferred cytoprotection, especially against CdCl2. However, such protection was not reproducible in the budding yeast Saccharomyces cerevisiae harboring pPMC. Taken together, these results propose that Pca1+may be involved in the growth and stress response of the fission yeast.