bluuebunny/crossref_metadata_2025 huggingface dataset:
Resource allocation and phenology of two species of Aster (Asteraceae) and their hybrid
Authors: Brouillet Luc , Simon Jean-Pierre
Published: November 2007

The phenology and the partitioning of resources were analysed in 16 populations of two species of Aster and their hybrid: A. acuminatus, a forest understory species: A. nemoralis, a bog species; and A. × blakei. These populations were all found within a 2-km radius in southwestern Québec. The three taxa were relatively synchronous in their flowering periods, although A. acuminatus and A. × blakei initiated flowering 10 days earlier than A. nemoralis. Reproductive effort was lower in A. nemoralis (4%) than in A. acuminatus (14%) and A. × blakei, although considerable variability for this trait was found among the last two taxa. A higher proportion of energy was directed towards stem production in A. nemoralis but its foliar biomass was similar to that of A. acuminatus and A. × blakei. However, the lower number of leaves per plant and their disposition in A. acuminatus determine a higher effective leaf area in this taxon. This trade-off appears to be an adaptive shift to enhance photosynthetic efficiency under the light-limiting conditions of the forest understory.
Influence of photoperiod on sporulation of and infection by Helminthosporium turcicum on Zea mays
Authors: Benedict W. G.
Published: November 2007

The influence of photoperiod on sporulation of and infection by Helminthosporium turcicum Pass. (Trichometasphaeria turcica Luttrell), the causal agent of northern leaf blight of corn (Zea mays L.), was studied in growth chambers simulating normal, field weather conditions. The results were compared to an epidemic of the disease on sweet corn in Kent County, Ontario, in 1972 during a period of unusual weather conditions. An 8-h photoperiod was required to maintain both the diseased plants in a state of survival and the fungus in a state of repeated sporulating cycles on the plants in the growth chambers. The specific climatic component which could be correlated with growth chamber data was the photoperiod. Extremely wide temperature and rainfall variations from their long term means, and a low average exposure to light, contributed to the progress of the disease.
Influence of amino acids and ammonium on nitrate reduction in corn seedlings
Authors: Oaks Ann , Stulen Ineke , Boesel Ingrid L.
Published: November 2007

Corn seedlings were transferred 48 h after imbibition to a medium containing [Formula: see text] Hoagland's salts and 5 mM nitrate (K14NO3 or K15NO3). Three treatments were used during the ensuing 6-h induction period: (i) no further additions: (ii) corn mixture of amino acids plus 10 mM glutamine and 10 mM asparagines; and (iii) 10 mM (NH4)2SO4. The shoots, mature root sections (25–35 mm from the tip), and root tip sections (0–10 mm) were then examined for nitrate reductase activity (NR) and the ability to reduce 15NO3in vivo.Both amino acid and ammonium additions resulted in less NR in the shoots. In the roots, the development of NR was inhibited slightly by the amino acids and was enhanced by ammonium additions. Treatment with either corn amino acids or (NH4)2SO4 had no influence on the incorporation of 15N into the ammonium and amino acid fraction. Thus, although the potential end products of NR have slight effects on measured in vitro levels of NR, they have no effect on the reduction of NO3− in the intact corn seedling.
Nucleolar organization in the euglenoid Astasia longa as disclosed by selective staining, actinomycin D treatment, and cold shock
Authors: Chaly N. , Lord A. , Lafontaine J. G.
Published: November 2007

Nucleolar ultrastructure in Astasia longa (Jahn) was examined in normal cells as well as in cells treated with actinomycin D or subjected to low temperature. Selective staining for ribonucleo-proteins (RNP) revealed that, in normal cells, the fibrillar nucleolar zones consisted of a rather homogeneous, moderately dense material within which were observed circular and elongate areas having a noticeably greater density. These denser areas were interpreted as corresponding to cross and oblique sections of a coarse filamentous structure, or nucleolonema, which constitutes the main component of the fibrillar zones. Following staining with Moyne's Feulgen-like technique, the nucleolonemal profiles appeared denser than the remaining regions of the nucleolar mass, thus indicating that DNA is associated with this filamentous structure. This conclusion was supported by the observation that actinomycin D, a substance known to react with DNA, rapidly induced a transformation of the fibrillar nucleolar zones. After 1 h of such treatment and staining for RNP, the nucleolus was observed to be homogeneously dense except for the presence of a number of small, circular, lighter areas presumably representing cross sections of the transformed nucleolonema. Staining for DNA revealed similar masses which were now denser than the remaining portion of the nucleolus. As a result of prolonged treatment with actinomycin D, the Feulgen-positive material often appeared as a coarse network segregated within a crescent-shaped and peripheral region of the nucleolar body.After exposure of cells to low temperature (14.5 °C) for 1 h the granular zones of the nucleolus became looser and the nucleolonemal core appeared less distinct. Nucleolar organization reverted almost to normal when the cold shock treatment was prolonged for a 3-h period.
The influence of nutrient balance on lignin degradation by the white-rot fungus Phanerochaete chrysosporium
Authors: Reid Ian D.
Published: November 2007

The degradation by Phanerochaete chrysosporium of "natural" lignin in aspen wood, like synthetic lignin, was inhibited by nitrogen and stimulated by carbohydrate. Nitrogen delayed the appearance and reduced the level of ligninolytic activity and indirectly hastened its decline by accelerating depletion of the carbohydrate supply. The carbon:nitrogen ratio of the medium was a better predictor of lignin degradation than the absolute carbohydrate and nitrogen levels. Unlike nitrogen limitation, sulphate and phosphate limitation of growth did not stimulate lignin metabolism.
Coelomycetes on Liliales: the genus Phyllosticta
Authors: Bissett J.
Published: November 2007

Phyllosticta crypta sp. nov. and P. cumminsii sp. nov. are described. Both fungi cause leaf spots on various species of Smilax in North America. Four other Phyllostictas previously reported from North American Liliaceae are redescribed, and a key is provided to distinguish the eight Phyllosticta species currently recognized on the Liliales.
Ultrastructural changes induced in zoospores of Lagenidium callinectes by exposure to Captan
Authors: Ruch D. G. , Bland C. E.
Published: November 2007

The effects of the fungicide Captan on growth, development, and fine structure of the marine fungus Lagenidium callinectes Couch are studied. At the minimum lethal concentration (LC100) of Captan for L. callinectes (3.2 ppm active component), zoospores exposed for 30 min failed to encyst or germinate. Ultrastructural changes caused by exposure to Captan included "washing-out" of the mitochondrial matrix and disappearance of many of the cristae, clumping of the chromatin and disappearance of the nuclear matrix, and swelling of the cisternae of the endoplasmic reticulum. Longer exposure of zoospores to Captan resulted ultimately in breakdown of the plasma membrane. These observations were in agreement with those of previous studies which indicated that the toxic action of Captan occurs primarily in mitochondria.
Production of aerial mycelium and teliospores of Puccinia horiana in chrysanthemum callus cultures
Authors: Ando Katsuhiko , Katsuya Keizo , Sato Shoji
Published: November 2007

Chrysanthemum callus tissues were grown from leaf pieces infected with Puccinia horiana. Feltlike aerial mycelia were frequently produced on the callus tissue. Callus tissue with aerial mycelium was maintained in vitro for more than 1 year by transplants at 4-month intervals. Teliospores were produced on the callus surface, in enlarged intercellular spaces of callus tissue, and in callus cells. Teliospores were longer than normal and had one to three cells instead of two cells. Aerial mycelium on callus tissue infected excised host leaves.
Merimbla gen. no v. for the anamorphic state of Talaromyces avellaneus
Authors: Pitt J. I. , Hocking Ailsa D.
Published: November 2007

Merimbla ingelheimense (van Beyma) Pitt is described for the anamorphic state of Talaromyces avellaneus C.R. Benjamin, a holomorphic fungus. Diagnostic features are discussed, together with a key for distinguishing Merimbla from Aspergillus, Geosmithia, Paecilomyces, Penicillium, and Raperia.
Effects of low temperature on leaf diffusion resistance of Ulmus americana and Fraxinus pennsylvanica seedlings
Authors: Kozlowski T. T. , Pallardy S. G.
Published: November 2007

Low temperatures (3–10 °C) for 1 h to 6 days increased leaf diffusion resistance (r1) of Ulmus americana and Fraxinus pennsylvanica seedlings, indicating rapid stomatal closure. The change in r1 increased as the temperature was lowered over a range of 10–3 °C. After cessation of cold-stress treatment, r1 values recovered within 1 day to prestress levels. No significant differences were found in speed of recovery of r1 in plants after exposure to cold over a range of 3– 10 °C. Stomatal closure could account thus for at least part of the decrease in photosynthesis at low temperatures.
The ultrastructure of meiosis in Plasmodiophora brassicae (Plasmodiophorales)
Authors: Garber Robert C. , Aist James R.
Published: November 2007

Meiosis was examined in plasmodia of the protist Plasmodiophora brassicae within artificially inoculated cabbage roots, using light and electron microscopy. Meiotic nuclear divisions occur following the cessation of vegetative growth of the Plasmodium. Synaptonemal complexes develop in nuclei of the “akaryote stage,” which represents prophase I. Meiosis I and II take place concurrently with cleavage of the Plasmodium into resting sporangia. Previous reports of synaptonemal complexes and sporangiogenic meiosis in the Plasmodiophorales are thus corroborated. Centrioles are paired and bipolar until the end of meiosis I; then they separate and migrate to opposite poles, without replicating, between prophase II and metaphase II. Centrioles elongate considerably between prophase I and the end of meiosis II, then appear to disintegrate as uninucleate resting sporangia are formed and are absent from mature sporangia.
Callus formation and shoot bud differentiation in anther culture of Solanum surattense
Authors: Sinha S. , Roy R. P. , Jha K. K.
Published: November 2007

In anther culture of Solatium surattense, the Murashige and Skoog's medium supplemented with 2,4-dichlorophenoxyacetic acid (2.2 mg/L), indoleacetic acid or naphthaleneacetic acid (1.9 mg/L), and kinetin (2.2 mg/L) served as “callus-producing medium.” Histological and cytological observations indicated that the callus originated from the pollen grains. Synergistic action of kinetin (5.0 mg/L) and coconut milk (15%) in basal medium was able to induce differentiation of shoot buds either from the anthers directly or from the callus. Directly differentiating buds were formed by whole shoot bud morphogenesis of pollen. They were produced at a low frequency and showed presence of well-developed radicular and plumular regions. But the buds originating from callus lacked radicular ends. Root initiation in such buds was achieved by transferring them to basal medium. Cytological examination of the androgenic plantlets revealed a chromosomal series ranging from the haploid to the hexaploid with a few aneuploids.
On the role of anthocyanins in vegetative tissues: a relationship with stem length in pea seedlings
Authors: Nozzolillo Constance
Published: November 2007

Red-stemmed pea seedlings grown from a heterogeneous lot of seeds (P.I. 356980) were shorter than green-stemmed seedlings grown from the same lot. Crosses between the two types show that the red stems are dominant to green stems with a 3:1 ratio in the F2. Stem lengths of the red-stemmed F2 plants, however, were not significantly different from those of the green-stemmed F2 plants. It is concluded that the presence of anthocyanins is not a direct cause of shorter stem length, nor are the genetic loci concerned linked. Other reasons for the association of shorter stems with red colouration are being investigated.
Localized populational differences in the photosynthetic response to temperature and irradiance in Plantago lanceolata
Authors: Teramura Alan H. , Strain Boyd R.
Published: November 2007

Leaves of Plantago lanceolata L. were collected from populations growing in shaded, sunflecked, and open habitats. Cloning techniques were used to propagate ramets of at least 10 individuals from each population. Photosynthetic and diffusion resistance responses were measured in ramets grown at a standard condition. Highly significant differences in the photosynthetic responses to temperature and irradiance were found among the three populations. These large differences were associated with similarly large differences in stomatal and nonstomatal diffusion resistances. The temperature response differences could be interpreted as adaptive to the site of origin of the various biotypes. Consequently, we present evidence of localized ecotypic differentiation which has occurred despite the potential for gene exchange among the populations.
Neighbour relationships in grass–legume communities. II. Temporal stability and community evolution
Authors: Aarssen Lonnie W. , Turkington Roy , Cavers Paul B.
Published: November 2007

Surveys of three old pastures near London, Ontario, over a period of 2 years revealed three categories of plant associations important in community evolution: stable, seasonal, and temporary. These are considered as counterparts to stabilizing, directional, and disruptive selection pressures in species evolution. Trifolium repens is proposed as a major "driving force" in directing community evolution. It is suggested that seral stages in secondary grassland succession are manifested through seasonal and random associations, whereas stable associations characterize the approach to subclimax.
Dinitrogen fixation associated with disomic chromosome substitution lines of spring wheat
Authors: Rennie R. J. , Larson R. I.
Published: November 2007

The modification of the genotype of the Cadet and Rescue cultivars of spring wheat (Triticum aestivum L. emend. Thell) by disomic chromosome substitution altered the amount of plant nitrogen derived from dinitrogen fixation by the associated bacterium in a phytotron experiment. With the exception of the C-R5B line, inoculation of the parent Cadet or its substitution lines with either the bacillus C-11-25 or Azospirillum brasilense increased plant dry matter and the total N yield. Rescue lines were unaffected by inoculation unless genotypically altered by substitution of the 5B or 5D chromosome from Cadet. Different substitution lines reacted uniquely to inoculation with the specific bacteria: C-R2A and R-C2D promoted greater dinitrogen fixation by A. brasilense; C-R5D, R-C5B, and R-C5D promoted greater dinitrogen fixation by the C-11-25 bacillus. Both bacteria had high and identical levels of dinitrogen fixation in association with the C-R2D line; neither bacterium fixed N when grown in association with the C-R5B, Rescue, or R-C2A lines. Although the ability of spring wheat to induce dinitrogen fixation in associated bacteria is influenced by chromosomes 5B (which controls root rot reaction) and 5D, it does not appear to be directly related to reaction to common root rot.
Fusarium species associated with grassland soils
Authors: McMullen M. P. , Stack R. W.
Published: November 2007

Soils from six grassland sites in North Dakota were analyzed for the presence and abundance of Fusarium species. Samples were collected during the growing seasons of 1979–1981 from an undisturbed sandhills tall-grass prairie, a heavily grazed mixed-grass prairie, two undisturbed mixed-grass prairies, and two cultivated fields. Samples were analyzed using a combination of isolation techniques and isolation media, which yielded 3602 isolates and 20 Fusarium taxa. Ten taxa occurred at all sites and their relative density accounted for 94.2% of the total. Fusarium oxysporum (46.1%) and F. equiseti (22.2%) were the most frequently isolated species. Statistically significant species by site interactions occurred. Recovery of F. acuminatum and F. avenaceum was significantly greater at the mixed-grass prairie sites dominated by blue-grama grass, while recovery of F. oxysporum was significantly greater at the undisturbed sites and significantly less at the disturbed sites. The cultivated sites were characterized by a significantly greater than expected recovery of F. equiseti. Seasonal trends in recovery of certain species were also statistically significant.
Phytophthora pseudotsugae, a new species causing root rot of Douglas-fir
Authors: Hamm P. B. , Hansen E. M.
Published: November 2007

Phytophthora pseudotsugae n. sp. was isolated from rotted roots of Douglas-fir growing in forest tree nurseries in Oregon and Washington. It is distinguished by large oogonia and oospores, mostly paragynous antheridia, and predominantly spherical or ovoid, persistent sporangia borne primarily on simple and unbranched sporangiophores. Sporangia are formed occasionally in liquid culture, rarely in solid media. Phytophthora pseudotsugae is distinguished most readily from P. cactorum by its unbranched sporangiophores and persistent sporangia. It also differs in growth on defined media, electrophoretic protein patterns, and pathogenicity. Comparison is also made with P. iranica, the other species in group 1 of Waterhouse.
Is autosporulation a feature of Nannochloris?
Authors: Brown Lewis M. , Elfman Beverly
Published: November 2007

The green algal genus Nannochloris Naumann was originally described as having a simple binary division mechanism and lacking autosporulation and a parental cell wall. An initial observation of autosporulation in one isolate ascribed to this genus encouraged a broader investigation to determine whether or not autosporulation is restricted to only certain forms or is the reproductive mechanism used in the genus as a whole. Five cultures were examined; all had typically chlorophycean ultrastructure and both chlorophylls a and b. Nannochloris atomus differed from the other forms (two Nannochloris spp., Nannochloris bacillaris, and Nannochloris maculants) in having a pyrenoid and different wall structure and other ultrastructural features. However, reproduction in all five was by autosporulation with a thin, yet clearly defined, parental wall surrounding the two–four daughter cells in electron micrographs. These and related findings of other workers point to the need for a redefinition of the genus.
The pattern of in situ summer nitrogenase activity in terrestrial Nostoc commune from Stipa–Bouteloa grassland, southern Alberta
Authors: Coxson D. S. , Kershaw K. A.
Published: November 2007

Field rates of nitrogenase activity by N. commune were followed over a 1-month summer period in Stipa–Bouteloa grassland of southern Alberta, using repeated short-term acetylene-reduction assays. Concurrent patterns of temperature, moisture, and light at the soil surface were continuously monitored. There is a rapid response of nitrogenase activity to both small precipitation events and dewfall hydration periods. Typically, thalli wet by thundershower activity in the previous evening showed a midday maximum of acetylene reduction of up to 5 nmol C2H4 mg−1 h−1, followed by a rapid cessation of activity as thalli desiccated below critical moisture levels. Over extended precipitation periods rates continue to climb throughout the day, gradually falling over the night period. Dry thalli frequently experience surface temperatures of up to 65 °C, without any discernable effects on rehydration recovery of nitrogenase activity. Equally, ground frosts early in the study period did not affect subsequent activity. Surface densities of up to 23.9 g m−2 were found for N. commune, with a mean cover of 4.3 g m−2. Mean cumulative nitrogen fixation over the 31-day field period was estimated to be 10.0 mg N m−2, although up to 77.3 mg N m−2 might be expected in localized microsites. The utilization of small rainfall events in large part accounts for the magnitude of observed nitrogenase activity. Although subsequent losses of fixed nitrogen through denitrification and volatilization are yet unknown, a significant proportion of nitrogen input to this grassland site must originate from asymbiotic biological fixation.
Transfer of additive "minor-effect" genes for resistance to Puccinia striiformis from Triticum dicoccoides into Triticum durum and Triticum aestivum
Authors: Reinhold M. , Sharp E. L. , Gerechter-Amitai Z. K.
Published: November 2007

Transgressive segregation for higher resistance to stripe rust (Puccinia striiformis) was found in segregating populations of crosses of Triticum dicoccoides × Triticum aestivum and T. dicoccoides × Triticum durum. This indicates that additive "minor-effect" gene resistance to stripe rust can be transferred directly from the wild emmer (AABB) to cultivated tetraploid and hexaploid wheats. Since "major-effect" genes for stripe-rust resistance seem to be limited in number, Triticum dicoccoides appears to be a valuable currently untapped reservoir for additive genes which can be combined with genes existing in the tetraploid and hexaploid wheats.
TUTANKHAMUN'S GOLDEN MASK INVESTIGATED WITH XRDF
Authors: UDA M. , YOSHIMURA S. , ISHIZAKI A. , YAMASHITA D. , SAKURABA Y.
Published: November 2007

This is a preliminary report for “the joint investigation between Japan and Egypt on Tutankhamun's golden mask”. This experiment was performed in the Egyptian Museum in Cairo using an XRDF (X-Ray Diffractometer equipped with x-ray Fluorescence spectrometer) setup invented by one of the authors (M. U.) and improved here. A diffraction pattern and a fluorescence spectrum can be obtained by the XRDF setup in the air from one and the same small area (1–2 mm in diameter) on a specimen.

The face and neck, and the other parts of the Tutankhamun's golden mask were composed of 23.2–23.5 K matrix covered with an 18 K Au - Ag - Cu thin layer, whitish gold in color, and with a 22.5 K Au - Ag - Cu thin layer, gold in color, respectively.

A dark blue material used for the nemes (headdress) was characterized with a new kind of glass paste which includ main components of Amarna blue and Egyptian blue, and is named here as Tutankhamun blue. A grayish blue material used for a false beard had a similar chemical composition to the dark blue one. Pectoral red and green beads were made of carnelian and amazonite, respectively.
IT-OUTSOURCING AND IT-OFFSHORING: TRENDS AND IMPACTS ON SE/KE CURRICULA
Authors: HIRA RON , DIESTE OSCAR , SPANOUDAKIS GEORGE , VISAGGIO GIUSEPPE , WIRTZ GUIDO , CHANG S. K.
Published: November 2007

As a result of IT outsourcing and offshoring, IT professionals and educators are faced with the following question: What SE & KE skill sets will make a software engineer or a knowledge engineer immune to the impact of outsourcing and offshoring? This article summarizes the position papers from a panel held during the 2006 International Conference on Software Engineering and Knowledge Engineering from July 5 to 7 at the Hotel Sofitel, Redwood City in California, USA. Bringing software and knowledge engineers closer to the needs of their prospective customers and providing more value than simply pure software development and maintenance, is an open challenge at least for traditional computer science and software engineering curricula.
ON GROUPS WHICH CONTAIN NO HNN-EXTENSIONS
Authors: ROBINSON DEREK J. S. , RUSSO ALESSIO , VINCENZI GIOVANNI
Published: November 2007

A group is called HNN-free if it has no subgroups that are nontrivial HNN-extensions. We prove that finitely generated HNN-free implies virtually polycyclic for a large class of groups. We also consider finitely generated groups with no free subsemigroups of rank 2 and show that in many situations such groups are virtually nilpotent. Finally, as an application of our results, we determine the structure of locally graded groups in which every subgroup is pronormal, thus generalizing a theorem of Kuzennyi and Subbotin.
DARK ENERGY IN GLOBAL BRANE UNIVERSE
Authors: PING YONGLI , XU LIXIN , ZHANG CHENGWU , LIU HONGYA
Published: November 2007

We discuss the exact solutions of brane universes and the results indicate that the Friedmann equations on the branes are modified with a new density term. Then, we assume the new term as the density of dark energy. Using Wetterich's parametrization equation of state (EOS) of dark energy, we obtain that the new term varies with the redshift z. Finally, the evolutions of the mass density parameter Ω2, dark energy density parameter Ωx and deceleration parameter q2 are studied.
PHASE COEXISTENCE AND SPINODALS IN ASYMMETRIC NUCLEAR MATTER
Authors: DUTRA M. , LOURENÇO O. , DELFINO A. , SÁ MARTINS J. S.
Published: November 2007

In this work we study the thermodynamic properties of an asymmetric system with arbitrary proton fraction, [Formula: see text]. We employ a Skyrme model in which surface and Coulomb effects are included phenomenologically to treat finite nuclei. We analyze the chemical and mechanical instabilities as a function of the asymmetry parameter. The coexistence surfaces (binodals) for different temperatures are constructed. We present applications to a set of finite nuclei, taking their critical parameters into account.
GEOMETRIC NONLINEAR ANALYSIS OF CABLE STRUCTURES WITH A TWO-NODE CABLE ELEMENT BY GENERALIZED DISPLACEMENT CONTROL METHOD
Authors: YANG Y. B. , TSAY JIUNN-YIN
Published: November 2007

This paper presents a two-node catenary cable element for the analysis of three-dimensional cable-supported structures. The stiffness matrix of the catenary cable element was derived as the inverse of the flexibility matrix, with allowances for selfweight and pretension effects. The element was then included, along with the beam and truss elements, in a geometric nonlinear analysis program, for which the procedure for computing the stiffness matrix and for performing iterations was clearly outlined. With the present element, each cable with no internal joints can be modeled by a single element, even for cables with large sags, as encountered in cable nets, suspension bridges and long-span cable-stayed bridges. The solutions obtained for all the examples are in good agreement with the existing ones, which indicates the accuracy and applicability of the element presented.
BUCKLING AND POSTBUCKLING ANALYSIS OF MULTI-WALLED CARBON NANOTUBES BASED ON THE CONTINUUM SHELL MODEL
Authors: HE X. Q. , QU C. , QIN Q. H. , WANG C. M.
Published: November 2007

Buckling and postbuckling behaviors of multi-walled carbon nanotubes (MWCNTs) under a compressive force are studied. MWCNTs are modeled by Donnell's shallow shell nonlinear theory with the allowance of van der Waals (vdW) interaction between the walls. It is shown herein that the buckling load decreases while the buckling strain increases as the innermost radius of MWCNT increases. For the postbuckling behavior, the shortening-load curves show an initial steep gradient that gradually level up when the radius of the innermost tube changes from a small value to a large value. However, the deflection-load curves are almost level for various radii of MWCNTs. In addition, the analytical results showed that the shortening-load curves are almost linear but the deflection-load curves are nonlinear and the stability of MWCNTs can be enhanced by adding tubes.
STRUCTURAL HEALTH MONITORING ORIENTED FINITE ELEMENT MODEL OF TSING MA BRIDGE TOWER
Authors: FEI QING GUO , XU YOU LIN , NG CHI LUN , WONG K. Y. , CHAN W. Y. , MAN K. L.
Published: November 2007

The modeling, updating and validation of a structural health monitoring oriented finite element model (FEM) of the Tsing Ma suspension bridge towers are presented in this paper. The portal-type bridge tower is composed of two hollow reinforced concrete legs and four deep pre-stressed cross-beams with a steel truss cast in the concrete of each cross-beam to form a narrow corridor for access between two legs. Except that steel trusses are modeled by beam elements, all structural components are modeled by solid elements to facilitate local damage detection, in particular at member joints. The established tower model is then updated using sensitivity-based model updating method taking the natural frequencies identified from field measurement data as reference. Furthermore, a two-level validation criterion is proposed and implemented to examine the replication performance of the updated finite element model of the bridge tower in terms of (1) natural frequencies in higher modes of vibration and (2) dynamic characteristics of the tower-cable system. The validation results show that a good replication of dynamic characteristics is achieved by the updated tower model when compared to the field measurement results. Finally, stress distribution and concentration of the bridge tower are investigated through nonlinear static analysis of the tower-cable system.
QUANTUM HALL DROPLETS ON DISC AND EFFECTIVE WESS–ZUMINO–WITTEN ACTION FOR EDGE STATES
Authors: DAOUD MOHAMMED , JELLAL AHMED
Published: November 2007

We algebraically analyze the quantum Hall effect of a system of particles living on the disc B1 in the presence of a uniform magnetic field B. For this, we identify the non-compact disc with the coset space SU(1,1)/U(1). This allows us to use the geometric quantization in order to get the wavefunctions as the Wigner [Formula: see text]-functions satisfying a suitable constraint. We show that the corresponding Hamiltonian coincides with the Maass Laplacian. Restricting to the lowest Landau level, we introduce the noncommutative geometry through the star product. Also we discuss the state density behavior as well as the excitation potential of the quantum Hall droplet. We show that the edge excitations are described by an effective Wess–Zumino–Witten action for a strong magnetic field and discuss their nature. We finally show that LLL wavefunctions are intelligent states.
RISK CONCEPTION AND RISK MANAGEMENT IN CORPORATE INNOVATION: LESSONS FROM TWO SWEDISH CASES
Authors: BERGLUND HENRIK
Published: November 2007

Risk is central to innovation, but in order to be theoretically interesting and of practical use, the relation between risk and innovation needs to be investigated in more specific situations. This paper explores the risk conceptions of innovators in two large corporations and identifies three themes that illuminate the relationship between risk and innovation in the corporate setting. The first relates risk to the issues of boundaries and control over parts of the innovation process; the second shows how risk is primarily related to innovation as process and not as output, and the third shows how a flexible view of business models can be used to manage risk in corporate innovation.
Plant Immunity to Insect Herbivores
Authors: Howe Gregg A. , Jander Georg
Published: November 2007

Herbivorous insects use diverse feeding strategies to obtain nutrients from their host plants. Rather than acting as passive victims in these interactions, plants respond to herbivory with the production of toxins and defensive proteins that target physiological processes in the insect. Herbivore-challenged plants also emit volatiles that attract insect predators and bolster resistance to future threats. This highly dynamic form of immunity is initiated by the recognition of insect oral secretions and signals from injured plant cells. These initial cues are transmitted within the plant by signal transduction pathways that include calcium ion fluxes, phosphorylation cascades, and, in particular, the jasmonate pathway, which plays a central and conserved role in promoting resistance to a broad spectrum of insects. A detailed understanding of plant immunity to arthropod herbivores will provide new insights into basic mechanisms of chemical communication and plant-animal coevolution and may also facilitate new approaches to crop protection and improvement.
Extending X-Ray Crystallography to Allow the Imaging of Noncrystalline Materials, Cells, and Single Protein Complexes
Authors: Miao Jianwei , Ishikawa Tetsuya , Shen Qun , Earnest Thomas
Published: November 2007

In 1999, researchers extended X-ray crystallography to allow the imaging of noncrystalline specimens by measuring the X-ray diffraction pattern of a noncrystalline specimen and then directly phasing it using the oversampling method with iterative algorithms. Since then, the field has evolved moving in three important directions. The first is the 3D structural determination of noncrystalline materials, which includes the localization of the defects and strain field inside nanocrystals, and quantitative 3D imaging of disordered materials such as nanoparticles and biomaterials. The second is the 3D imaging of frozen-hydrated whole cells at a resolution of 10 nm or better. A main thrust is to localize specific multiprotein complexes inside cells. The third is the potential of imaging single large protein complexes using extremely intense and ultrashort X-ray pulses. In this article, we review the principles of this methodology, summarize recent developments in each of the three directions, and illustrate a few examples.
IFN-α induces barrier destabilization and apoptosis in renal proximal tubular epithelium
Authors: Lechner Judith , Malloth Nadia , Seppi Thomas , Beer Bea , Jennings Paul , Pfaller Walter
Published: November 2007

Type I IFNs, like IFN-α, are major immune response regulators produced and released by activated macrophages, dendritic cells, and virus-infected cells. Due to their immunomodulatory functions and their ability to induce cell death in tumors and virus-infected cells, they are used therapeutically against cancers, viral infections, and autoimmune diseases. However, little is known about the adverse effects of type I IFNs on nondiseased tissue. This study examined the effects of IFN-α on cell death pathways in renal proximal tubular cells. IFN-α induced apoptosis in LLC-PK1 cells, characterized by the activation of caspase-3, -8, and -9, DNA fragmentation, and nuclear condensation. IFN-α also caused mitochondrial depolarization. Effector caspase activation was dependent on caspase-8 and -9. In addition to apoptosis, IFN-α exposure also decreased renal epithelial barrier function, which preceded apoptotic cell death. Caspase inhibition did not influence permeability regulation while significantly attenuating and delaying cell death. These results indicate that IFN-α causes programmed cell death in nondiseased renal epithelial cells. IFN-α-induced apoptosis is directed by an extrinsic death receptor signaling pathway, amplified by an intrinsic mitochondrial pathway. Caspase-dependent and -independent apoptotic mechanisms are involved. These findings reveal a novel aspect of IFN-α actions with implications for normal renal function in immune reactions and during IFN-α therapy.
TH and NPY in sympathetic neurovascular cultures: role of LIF and NT-3
Authors: Damon Deborah H.
Published: November 2007

The sympathetic nervous system is an important determinant of vascular function. The effects of the sympathetic nervous system are mediated via release of neurotransmitters and neuropeptides from postganglionic sympathetic neurons. The present study tests the hypothesis that vascular smooth muscle cells (VSM) maintain adrenergic neurotransmitter/neuropeptide expression in the postganglionic sympathetic neurons that innervate them. The effects of rat aortic and tail artery VSM (AVSM and TAVSM, respectively) on neuropeptide Y (NPY) and tyrosine hydroxylase (TH) were assessed in cultures of dissociated sympathetic neurons. AVSM decreased TH (39 ± 12% of control) but did not affect NPY. TAVSM decreased TH (76 ± 10% of control) but increased NPY (153 ± 20% of control). VSM expressed leukemia inhibitory factor (LIF) and neurotrophin-3 (NT-3), which are known to modulate NPY and TH expression. Sympathetic neurons innervating blood vessels expressed LIF and NT-3 receptors. Inhibition of LIF inhibited the effect of AVSM on TH. Inhibition of neurotrophin-3 (NT-3) decreased TH and NPY in neurons grown in the presence of TAVSM. These data suggest that vascular-derived LIF decreases TH and vascular-derived NT-3 increases or maintains NPY and TH expression in postganglionic sympathetic neurons. NPY and TH in vascular sympathetic nerves are likely to modulate NPY and/or norepinephrine release from these nerves and are thus likely to affect blood flow and blood pressure. The present studies suggest a novel mechanism whereby VSM would modulate sympathetic control of vascular function.
Saccharomyces boulardiiamelioratesCitrobacter rodentium-induced colitis through actions on bacterial virulence factors
Authors: Wu X. , Vallance B. A. , Boyer L. , Bergstrom K. S. B. , Walker J. , Madsen K. , O'Kusky J. R. , Buchan A. M. , Jacobson K.
Published: November 2007

Saccharomyces boulardii has received increasing attention as a probiotic effective in the prevention and treatment of infectious and inflammatory bowel diseases. The aim of this study was to examine the ameliorating effects of S. boulardii on Citrobacter rodentium colitis in vivo and identify potential mechanisms of action. C57BL/6 mice received 2.5 × 108C. rodentium by gavage on day 0, followed by S. boulardii (25 mg; 5 × 108live cells) gavaged twice daily from day 2 to day 9. Animal weights were monitored until death on day 10. Colons were removed and assessed for epithelial barrier function, histology, and myeloperoxidase activity. Bacterial epithelial attachment and type III secreted proteins translocated intimin receptor Tir (the receptor for bacterial intimin) and EspB (a translocation apparatus protein) required for bacterial virulence were assayed. In infected mice, S. boulardii treatment significantly attenuated weight loss, ameliorated crypt hyperplasia (234.7 ± 7.2 vs. 297.8 ± 17.6 μm) and histological damage score (0.67 ± 0.67 vs. 4.75 ± 0.75), reduced myeloperoxidase activity (2.1 ± 0.4 vs. 4.7 ± 0.9 U/mg), and attenuated increased mannitol flux (17.2 ± 5.0 vs. 31.2 ± 8.2 nm·cm−2·h−1). The ameliorating effects of S. boulardii were associated with significantly reduced numbers of mucosal adherent C. rodentium, a marked reduction in Tir protein secretion and translocation into mouse colonocytes, and a striking reduction in EspB expression and secretion. We conclude that S. boulardii maintained colonic epithelial barrier integrity and ameliorated inflammatory sequelae associated with C. rodentium infection by attenuating C. rodentium adherence to host epithelial cells through putative actions on the type III secretion system.
EGF receptor transactivation and MAP kinase mediate proteinase-activated receptor-2-induced chloride secretion in intestinal epithelial cells
Authors: van der Merwe Jacques Q. , Hollenberg Morley D. , MacNaughton Wallace K.
Published: November 2007

We examined the stimulus-secretion pathways whereby proteinase-activated receptor 2 (PAR-2) stimulates Cl−secretion in intestinal epithelial cells. SCBN and T84 epithelial monolayers grown on Snapwell supports and mounted in modified Ussing chambers were activated by the PAR-2-activating peptides SLIGRL-NH2and 2-furoyl-LIGRLO-NH2. Short-circuit current ( Isc) was used as a measure of net electrogenic ion transport. Basolateral, but not apical, application of SLIGRL-NH2or 2-furoyl-LIGRLO-NH2caused a concentration-dependent change in Iscthat was significantly reduced in Cl−-free buffer and by the intracellular Ca2+blockers thapsigargin and BAPTA-AM, but not by the Ca2+channel blocker verapamil. Inhibitors of PKA (H-89) and CFTR (glibenclamide) also significantly reduced PAR-2-stimulated Cl−transport. PAR-2 activation was associated with increases in cAMP and intracellular Ca2+. Immunoblot analysis revealed increases in phosphorylation of epidermal growth factor (EGF) receptor (EGFR) tyrosine kinase, Src, Pyk2, cRaf, and ERK1/2 in response to PAR-2 activation. Pretreatment with inhibitors of cyclooxygenases (indomethacin), tyrosine kinases (genistein), EGFR (PD-153035), MEK (PD-98059 or U-0126), and Src (PP1) inhibited SLIGRL-NH2-induced increases in Isc. Inhibition of Src, but not matrix metalloproteinases, reduced EGFR phosphorylation. Reduced EGFR phosphorylation paralleled the reduction in PAR-2-stimulated Isc. We conclude that activation of basolateral, but not apical, PAR-2 induces epithelial Cl−secretion via cAMP- and Ca2+-dependent mechanisms. The secretory effect involves EGFR transactivation by Src, leading to subsequent ERK1/2 activation and increased cyclooxygenase activity.
Effects of α-lipoic acid on ischemia-reperfusion-induced renal dysfunction in rats
Authors: Bae Eun Hui , Lee Kyun Sang , Lee JongUn , Ma Seong Kwon , Kim Nam Ho , Choi Ki Chul , Frøkiær Jørgen , Nielsen Søren , Kim Sun Young , Kim Sung Zoo , Kim Suhn Hee , Kim Soo Wan
Published: November 2007

We investigated whether α-lipoic acid (α-LA), an antioxidant, attenuates the ischemia-reperfusion (I/R)-induced dysregulation of these transporters. Both renal pedicles of male Sprague-Dawley rats were clamped for 40 min. α-LA (80 mg/kg) was administered intraperitoneally before and immediately after induction of ischemia. After 2 days, the expression of aquaporins (AQPs), sodium transporters, and nitric oxide synthases (NOS) was determined in the kidney by immunoblotting and immunohistochemistry. The expression of endothelin-1 (ET-1) mRNA was determined by real-time PCR. Activities of adenylyl cyclase and guanylyl cyclase were measured by stimulated generation of cAMP and cGMP, respectively. The expression of AQP1–3 as well as that of the α1-subunit of Na-K-ATPase, type 3 Na/H exchanger, Na-K-2Cl cotransporter, and Na-Cl cotransporter was markedly decreased in response to I/R. The expression of type VI adenylyl cyclase was decreased in I/R-injured rats, which was counteracted by the treatment of α-LA. AVP-stimulated cAMP generation was blunted in I/R rats and was then ameliorated by α-LA treatment. α-LA treatment attenuated the downregulation of AQPs and sodium transporters. The expression of endothelial NOS was decreased in I/R rats, which was prevented by α-LA. The cGMP generation in response to sodium nitroprusside was blunted in I/R rats, which was also significantly prevented by α-LA. The mRNA expression of ET-1 was increased, which was recovered to the control level by α-LA treatment. In conclusion, α-LA treatment prevents I/R-induced dysregulation of AQPs and sodium transporters in the kidney, possibly through preserving normal activities of local AVP/cAMP, nitric oxide/cGMP, and ET systems.
Currents Contributing to Decision Making in Neurons B31/B32 ofAplysia
Authors: Hurwitz Itay , Ophir Amit , Korngreen Alon , Koester John , Susswein Abraham J.
Published: November 2007

Biophysical properties of neurons contributing to the ability of an animal to decide whether or not to respond were examined. B31/B32, two pairs of bilaterally symmetrical Aplysia neurons, are major participants in deciding to initiate a buccal motor program, the neural correlate of a consummatory feeding response. B31/B32 respond to an adequate stimulus after a delay, during which time additional stimuli influence the decision to respond. B31/B32 then respond with a ramp depolarization followed by a sustained soma depolarization and axon spiking that is the expression of a commitment to respond to food. Four currents contributing to decision making in B31/B32 were characterized, and their functional effects were determined, in current- and voltage-clamp experiments and with simulations. Inward currents arising from slow muscarinic transmission were characterized. These currents contribute to the B31/B32 depolarization. Their slow activation kinetics contribute to the delay preceding B31/B32 activity. After the delay, inward currents affect B31/B32 in the context of two endogenous inactivating outward currents: a delayed rectifier K+current ( IK-V) and an A-type K+current ( IK-A), as well as a high-threshold noninactivating outward current ( Imaintained). Hodgkin-Huxley kinetic analyses were performed on the outward currents. Simulations using equations from these analyses showed that IK-Vand IK-Aslow the ramp depolarization preceding the sustained depolarization. The three outward currents contribute to braking the B31/B32 depolarization and keeping the sustained depolarization at a constant voltage. The currents identified are sufficient to explain the properties of B31/B32 that play a role in generating the decision to feed.
Activation of Postsynaptic GABABReceptors Modulates the Bursting Pattern and Synaptic Activity of Olfactory Bulb Juxtaglomerular Neurons
Authors: Karpuk Nikolay , Hayar Abdallah
Published: November 2007

Olfactory bulb glomeruli are formed by a network of three major types of neurons collectively called juxtaglomerular (JG) cells, which include external tufted (ET), periglomerular (PG), and short axon (SA) cells. There is solid evidence that γ-aminobutyric acid (GABA) released from PG neurons presynaptically inhibits glutamate release from olfactory nerve terminals via activation of GABABreceptors (GABAB-Rs). However, it is still unclear whether ET cells have GABAB-Rs. We have investigated whether ET cells have functional postsynaptic GABAB-Rs using extracellular and whole cell recordings in olfactory bulb slices. In the presence of fast synaptic blockers (CNQX, APV, and gabazine), the GABAB-R agonist baclofen either completely inhibited the bursting or reduced the bursting frequency and increased the burst duration and the number of spikes/burst in ET cells. In the presence of fast synaptic blockers and tetrodotoxin, baclofen induced an outward current in ET cells, suggesting a direct postsynaptic effect. Baclofen reduced the frequency and amplitude of spontaneous EPSCs in PG and SA cells. In the presence of sodium and potassium channel blockers, baclofen reduced the frequency of miniature EPSCs, which were inhibited by the calcium channel blocker cadmium. All baclofen effects were reversed by application of the GABAB-R antagonist CGP55845 . We suggest that activation of GABAB-Rs directly inhibits ET cell bursting and decreases excitatory dendrodendritic transmission from ET to PG and SA cells. Thus the postsynaptic GABAB-Rs on ET cells may play an important role in shaping the activation pattern of the glomeruli during olfactory coding.
Vitamin E Supplementation Reduces Cardiovascular Events in a Subgroup of Middle-Aged Individuals With Both Type 2 Diabetes Mellitus and the Haptoglobin 2-2 Genotype
Authors: Milman Uzi , Blum Shany , Shapira Chen , Aronson Doron , Miller-Lotan Rachel , Anbinder Yefim , Alshiek Junia , Bennett Lawrence , Kostenko Maria , Landau Michele , Keidar Shlomo , Levy Yishai , Khemlin Alexander , Radan Arman , Levy Andrew P.
Published: November 2007

Objective—

Clinical trials of vitamin E have failed to demonstrate a decrease in cardiovascular events. However, these studies did not address possible benefit to subgroups with increased oxidative stress. Haptoglobin (Hp), a major antioxidant protein, is a determinant of cardiovascular events in patients with Type 2 diabetes mellitus (DM). The Hp gene is polymorphic with 2 common alleles, 1 and 2. The Hp 2 allelic protein product provides inferior antioxidant protection compared with the Hp 1 allelic product. We sought to test the hypothesis that vitamin E could reduce cardiovascular events in DM individuals with the Hp 2-2 genotype, a subgroup that comprises 2% to 3% of the general population.

Methods and Results—

1434 DM individuals ≥55 years of age with the Hp 2-2 genotype were randomized to vitamin E (400 U/d) or placebo. The primary composite outcome was myocardial infarction, stroke, and cardiovascular death. At the first evaluation of events, 18 months after initiating the study, the primary outcome was significantly reduced in individuals receiving vitamin E (2.2%) compared with placebo (4.7%;
P
=0.01) and led to early termination of the study.

Conclusions—

Vitamin E supplementation appears to reduce cardiovascular events in individuals with DM and the Hp 2-2 genotype (ClinicalTrials.gov NCT00220831).