bluuebunny/crossref_metadata_2025 huggingface dataset:
GROWTH STIMULATION OF ALEXANDRIUM TAMARENSE (DINOPHYCEAE) BY HUMIC SUBSTANCES FROM THE MANICOUAGAN RIVER (EASTERN CANADA)1
Authors: Gagnon Réal , Levasseur Maurice , Weise Andrea M. , Fauchot Juliette , Campbell Peter G. C. , Weissenboeck Bryan J. , Merzouk Anissa , Gosselin Michel , Vigneault Bernard
Published: June 2005

In the St. Lawrence Estuary, annual recurrent blooms of the toxic dinoflagellate Alexandrium tamarense L. Balech are associated with brackish waters. Riverine inputs are suspected to favor bloom development by increasing water column stability and/or by providing growth stimulants such as humic substances (HS). A 17‐day culture experiment was conducted to evaluate the importance of HS as growth factors for A. tamarense. Nonaxenic cultures were exposed to four HS extracts from three different sources: humic and fulvic acids isolated from the Manicouagan River, Quebec, Canada; humic acids from the Suwannee River, Georgia, United States; and a desalted alkaline soil extract. For each extract, four concentrations were tested as supplements to the artificial Keller medium, a nitrate‐rich algal culture medium. Additions of HS from all sources significantly enhanced the overall growth rates relative to the controls. Concentrations of HS, estimated by UV spectrophotometry, remained constant throughout the exponential growth phase, suggesting that the HS were acting mainly as growth promoters during our experiment. Dose–response curves indicated that HS could increase the growth rate of A. tamarense even at low concentrations, such as those encountered in the St. Lawrence Estuary. Our results support the hypothesis that HS from the Manicouagan River plume can stimulate the development of toxic dinoflagellate blooms.
PHYLOGENETIC IMPLICATIONS OF THE CAD COMPLEX FROM THE PRIMITIVE RED ALGA CYANIDIOSCHYZON MEROLAE (CYANIDIALES, RHODOPHYTA)1
Authors: Nozaki Hisayoshi , Matsuzaki Motomichi , Misumi Osami , Kuroiwa Haruko , Higashiyama Tetsuya , Kuroiwa Tsuneyoshi
Published: June 2005

The de novo pyrimidine biosynthetic pathway consists of six enzymes: carbamoyl‐phosphate synthetase II (CPS II), aspartate carbamoyltransferase (ACT), dihydroorotase (DHO), dihydroorotate dehydrogenase, orotate phosphoribosyltransferase, and orotidine‐5′‐monophosphate decarboxylase. The origin and organization of the first three enzymes differ markedly between Opisthokonta (Metazoa and Fungi) and the Amoebozoa and green plants. However, no information has been available regarding the characteristics of such genes in other photosynthetic eukaryotes. In this study, we examined the pyrimidine biosynthetic cluster in the primitive red alga Cyanidioschyzon merolae P. DeLuca et al. isolate 10D. Unlike the situation in green plants, the CPS II, ACT, and DHO of C. merolae were fused to form a single open reading frame (the CAD complex), as in the Opisthokonta and Amoebozoa. Phylogenetic analysis of the CPS domain sequences suggested that this red algal CAD complex did not result from a recent lateral gene transfer from Metazoa or Fungi but that the fusion of the three genes occurred before the divergence of Opisthokonta, Amoebozoa, and the red algae. These results cast doubt on the recent hypothesis that the Opisthokonta and Amoebozoa form a monophyletic group, based on the presence in both of the CAD complex.
LIFE CYCLE, SIZE REDUCTION PATTERNS, AND ULTRASTRUCTURE OF THE PENNATE PLANKTONIC DIATOM PSEUDO‐NITZSCHIA DELICATISSIMA (BACILLARIOPHYCEAE)1
Authors: Amato Alberto , Orsini Luisa , D'Alelio Domenico , Montresor Marina
Published: June 2005

Pseudo‐nitzschia delicatissima (Cleve) Heiden is a very common pennate planktonic diatom found in temperate marine waters, where it is often responsible for blooms. Recently, three distinct internal transcribed spacer types have been recorded during a P. delicatissima bloom in the Gulf of Naples (Mediterranean Sea, Italy), which suggests the existence of cryptic diversity. We carried out mating experiments with clonal strains belonging to the most abundant internal transcribed spacer type. Pseudo‐nitzschia delicatissima is heterothallic and produces two functional anisogametes per gametangium. The elongated auxospore possesses a transverse and a longitudinal perizonium. The sexual phase was observed to occur over a wide size spectrum, spanning 19–80 μm and corresponding to almost the whole range of cell length observed for P. delicatissima. We also investigated cell morphology, valve ultrastructure and morphometry of parental, F1‐generation strains, and the progeny of crosses between parental and F1 strains. Although ultrastructural features match those described for P. delicatissima, variability in cell shape was recorded in the largest cells of the F1 generation as well as in valves with an abnormal arrangement of poroids. As many other diatoms, P. delicatissima undergoes size reduction over its life cycle, and cells of different size showed differences in growth rates and the amount of size reduction per cell cycle. Cells between 60 and 30 μm in length showed the fastest growth and the slowest rates of size reduction per generation. In culture, P. delicatissima cells can decrease to 8 μm in length; however, such small cells (≤30 μm) are not recorded in the sea, and this raises interesting questions about the factors that control their survival in the natural environment.
MOLECULAR AND MORPHOMETRIC DATA PINPOINT SPECIES BOUNDARIES IN HALIMEDA SECTION RHIPSALIS (BRYOPSIDALES, CHLOROPHYTA)1
Authors: Verbruggen Heroen , De Clerck Olivier , Kooistra Wiebe H. C. F. , Coppejans Eric
Published: June 2005

Molecular systematic studies have changed the face of algal taxonomy. Particularly at the species level, molecular phylogenetic research has revealed the inaccuracy of morphology‐based taxonomy: Cryptic and pseudo‐cryptic species were shown to exist within many morphologically conceived species. This study focused on section Rhipsalis of the green algal genus Halimeda. This section was known to contain cryptic diversity and to comprise species with overlapping morphological boundaries. In the present study, species diversity within the section and identity of individual specimens were assessed using ITS1–5.8S–ITS2 (nrDNA) and rps3 (cpDNA) sequence data. The sequences grouped in a number of clear‐cut genotypic clusters that were considered species. The same specimens were subjected to morphometric analysis of external morphological and anatomical structures. Morphological differences between the genotypic cluster species were assessed using discriminant analysis. It was shown that significant morphological differences exist between genetically delineated species and that allocation of specimens to species on the basis of morphometric variables is nearly perfect. Anatomical characters yielded better results than external morphological characters. Two approaches were offered to allow future morphological identifications: a probabilistic approach based on classification functions of discriminant analyses and the classical approach of an identification key.
HIGH LEVELS OF GENETIC DIVERSITY AND LOW LEVELS OF GENETIC DIFFERENTIATION IN NORTH SEA PSEUDO‐NITZSCHIA PUNGENS (BACILLARIOPHYCEAE) POPULATIONS1
Authors: Evans Katharine M. , Kühn Stefanie F. , Hayes Paul K.
Published: June 2005

Six microsatellite markers were used to investigate the genetic structure of North Sea Pseudo‐nitzschia pungens (Grunow ex P. T. Cleve) Hasle populations. Isolates were collected on 42 separate occasions from waters surrounding the German islands of Helgoland and Sylt over the course of three sampling periods: spring 2002, spring 2003, and autumn 2003. In total, 464 isolates were genotyped, of which 453 were different (i.e. clonal diversity was 98%). The numbers of alleles per locus ranged from 6 to 24 and the observed heterozygosities from 0.59 to 0.87 (mean Ho and He were 0.73); there were no significant departures from Hardy‐Weinberg equilibrium at any of the six loci. Sexual reproduction therefore appears to be important in the production of genetic variation. Over the temporal and spatial scales sampled (18 months and 100 km), weak genetic differentiation was detected both within and between sampling periods (significant FST values ranged from 0.0018 to 0.0389), suggesting that the German North Sea supports a single largely unstructured population of P. pungens.
GALEIDINIIUM RUGATUM GEN. ET SP. NOV. (DINOPHYCEAE), A NEW COCCOID DINOFLAGELLATE WITH A DIATOM ENDOSYMBIONT1
Authors: Tamura Maiko , Shimada Satoshi , Horiguchi Takeo
Published: June 2005

A new sand‐dwelling dinoflagellate from Palau, Galeidinium rugatum Tamura et Horiguchi gen. et sp. nov., is described. The life cycle of this new alga consists of a dominant nonmotile phase and a brief motile phase. The motile cell transforms itself directly into the nonmotile cell after swimming for a short period, and cell division takes place in the nonmotile phase. The nonmotile cell possesses a dome‐like cell covering, which is wrinkled and equipped with a transverse groove on the surface. The cell has 10–20 chloroplasts and a distinct eyespot. The motile cell is Gymnodinium‐like in shape. The dinoflagellate possesses an endosymbiotic alga to which the chloroplasts belong and which is separated from the host (dinoflagellate) cytoplasm by a unit membrane. The endosymbiont cytoplasm also possesses its own eukaryotic nucleus and mitochondria. The eyespot is surrounded by triple membranes and is located in the host cytoplasm. Photosynthetic pigment analysis, using HPLC, revealed that G. rugatum possesses fucoxanthin as the principal accessory pigment instead of peridinin. The rbcL tree showed that G. rugatum is monophyletic with Durinskia baltica (Levander) Carty et Cox and Kryptoperidinium foliaceum (Stein) Lindemann and that this clade is closely related to the pennate diatom, Cylindrotheca sp. The endosymbiont of G. rugatum is therefore shown to be a diatom. Phylogenetic analysis based on small subunit rDNA sequences demonstrated that G. rugatum, D. baltica, and K. foliaceum, all of which are known to harbor an endosymbiont of diatom origin, are closely related.
THE ROLE AND EVOLUTION OF SUPEROXIDE DISMUTASES IN ALGAE1
Authors: Wolfe‐Simon Felisa , Grzebyk Daniel , Schofield Oscar , Falkowski Paul G.
Published: June 2005

Superoxide dismutases (SOD) catalyze the disproportionation of the potentially destructive superoxide anion radical (O2•−, a byproduct of aerobic metabolism) to molecular oxygen and hydrogen peroxide: 2O2•−+2H+→H2O2+O2. Based on metal cofactors, four known metalloforms of SOD enzymes have been identified: they contain either Fe, Mn, Cu and Zn, or Ni. Orthologs of all metalloforms are present in oxygenic photoautotrophs. The expression of SOD is highly regulated, with specific metalloforms playing an inducible protective role for specific cellular compartments. The various metalloforms of SOD are not distributed equally within either cyanobacteria or eukaryotic algae. Typically, cyanobacteria contain either an NiSOD alone or combinations of Mn and Ni or Fe and Mn metalloforms (CuZn is rare among the cyanobacteria). The bacillariophytes and rhodophytes retain an active MnSOD, whereas the chlorophytes, haptophytes, and embryophytes have either FeSOD or multiple combinations of Fe, Mn, and CuZnSODs. The NiSOD is a relatively novel SOD and has been generally excluded from evolutionary analyses. In both cyanobacteria and chlorophyte algae, the FeSOD metalloform appears to be associated with PSI, where its primary role is most likely to deactivate reactive oxygen produced by the Mehler reaction. The CuZnSOD also appears to be associated with the plastid but is phylogenetically more restricted in its distribution. In eukaryotic algae, SODs are all nuclear encoded and, based on nucleotide sequence, protein structures, and phylogenetic distributions, appear to have unique evolutionary histories arising from the lateral gene transfer of three distinct genes to the nucleus after the endosymbiotic acquisition of mitochondria and plastids. The varied phylogenetic histories and subcellular localizations suggest significantly different selection on these SOD metalloforms after the endosymbiont organelle‐to‐host gene transfer.
EVIDENCE OF A LATENT OXIDATIVE BURST IN RELATION TO WOUND REPAIR IN THE GIANT UNICELLULAR CHLOROPHYTE DASYCLADUS VERMICULARIS1
Authors: Ross Cliff , Küpper Frithjof C. , Vreeland Valerie , Herbert Waite J. , Jacobs Robert S.
Published: June 2005

We investigated the kinetics and composition of the second phase of the wound repair process of Dasycladus vermicularis ([Scropoli] Krasser) using fluorescent probes, chromatography, UV spectroscopy, and histochemistry. Our new evidence supports the hypothesis that the second phase of wound repair (initiated at approximately 35–45 min postinjury) is based on the activation of an oxidative burst that produces micromolar H2O2 levels. These results provide evidence of peroxidase activity at the wound site, real‐time measurements of an oxidative burst, and catechol localization in wound plugs. Strong evidence is presented indicating that the biochemical machinery exists for oxidative cross‐linking to ensue in the wound‐healing process of D. vermicularis.
Finite Element Analysis of High Contact Ratio Spur Gears in Mesh
Authors: Wang Jiande , Howard Ian
Published: June 2005

High contact ratio gears have been demonstrated to provide significant advantages for decreasing tooth root and contact stresses with potential flow-on benefits for increased load carrying capacity. Previous investigations with high contact ratio gears have involved analytical, numerical and experimental aspects. Much of the earlier numerical work using FEA was limited in its usefulness due to several factors; (i) the difficulty in predicting load sharing over roll angles covering two or three teeth simultaneously in mesh, (ii) the difficulty for the analysis to obtain quality results when modelling Hertzian contact deflection simultaneously with the bending, shear and angular deflections, and (iii) the problem of primary unconstrained body motion when (long) profile modifications were applied. This paper presents methods and results for overcoming these difficulties with recent computer hardware and software improvements. Particular developments discussed include the use of FE analysis of High Contact Ratio Gears in mesh and the results obtained when adaptive meshing is used. The details of transmission error, combined torsional mesh stiffness, load-sharing ratio, contact stress and tooth root stress against various input loads over a complete mesh cycle are also given. Results with various tooth profile modifications are presented and comparisons between the results show evidence for the optimal profile modification expected to gain the maximum benefit of HCRG.
Determination of the Discharge Coefficient of a Thin-Walled Orifice Used in Hydrostatic Bearings
Authors: Charles S. , Bonneau O. , Fre^ne J.
Published: June 2005

The characteristics of hydrostatic bearings can be influenced by the compensating device they use, for example, a thin-walled orifice (diaphragm). The flow through the orifice is given by a law where an ad hoc discharge coefficient appears, and, in order to guarantee the characteristics of the hydrostatic bearing, this coefficient must be calibrated. The aim of this work is to provide an accurate estimation of the discharge coefficient under specific conditions. Therefore an experimental bench was designed and a numerical model was carried out. The results obtained then by the experimental and theoretical approach were compared with the values given by the literature. Finally, the influence of the discharge coefficient on the behavior of a thrust bearing is examined.
Experimental Characterization of the Influence of Coating Materials on the Hydrodynamic Behavior of Thrust Bearings: A Comparison of Babbitt, PTFE, and PFA
Authors: Mahieux C. A.
Published: June 2005

The present paper is the first of a series dealing with the experimental characterization of the coating materials’ influence on the hydrodynamic behavior of thrust bearings. This paper presents a unique set of experimental data characterizing the influence of material coating on hydrodynamic oil films. The data are presented for extensive experimental conditions in which the load, the rotation speed, and the temperature were systematically varied. Seven main parameters characterizing the oil film were recorded. One metallic coating (Babbitt) and two Teflon-based coatings (polytetrafluoroethylene and polyperfluoroalkoxyethylene) were tested. It was clearly evidenced that the nature of the material strongly influences the hydrodynamic behavior. As expected in the hydroelastic regime, coatings with different properties (i.e., metals versus polymers) exhibit strong differences in their hydrodynamic behavior. The originality of the paper lies, however, in that the two polymers showed very different behavior.
The Difficulty of Measuring Low Friction: Uncertainty Analysis for Friction Coefficient Measurements
Authors: Schmitz, Tony L. , Action, Jason E. , Ziegert, and John C. , Sawyer W. Gregory
Published: June 2005

The experimental evaluation of friction coefficient is a common laboratory procedure; however, the corresponding measurement uncertainty is not widely discussed. This manuscript examines the experimental uncertainty associated with friction measurements by following the guidelines prescribed in international standards. The uncertainty contributors identified in this analysis include load cell calibration, load cell voltage measurement, and instrument geometry. A series of 20 tests, carried out under nominally identical conditions, was performed using a reciprocating pin-on-disk tribometer. A comparison between the experimental standard deviation and uncertainty analysis results is provided.
Revisiting the Removal Rate Model for Oxide CMP
Authors: Sorooshian Jamshid , Borucki Leonard , Stein David , Timon Robert , Hetherington Dale , Philipossian Ara
Published: June 2005

This study seeks to explain removal rate trends and scatter in thermal silicon dioxide and PECVD tetraethoxysilane-sourced silicon dioxide (PE-TEOS) CMP using an augmented version of the Langmuir-Hinshelwood mechanism. The proposed model combines the chemical and mechanical facets of interlevel dielectric (ILD) CMP and hypothesizes that the chemical reaction temperature is determined by transient flash heating. The agreement between the model and data suggests that the main source of apparent scatter in removal rate data plotted as rate versus pressure times velocity is competition between mechanical and thermochemical mechanisms. A method of visualizing removal rate data is described that shows, apart from any particular interpretative theory, that a smooth and easily interpretable surface underlies the apparent scatter.
A Study of Roughness and Non-Newtonian Effects in Lubricated Contacts
Authors: Kane Malal , Bou-Said Benyebka
Published: June 2005

This article is concerned with the simulation of a lubricated contact considering the fluid to be non-Newtonian of the Maxwell type. Severe operating conditions lead to very small surface-to-surface distances. In this situation it is necessary to take roughness effects into account. A popular method consists in averaging the film thickness following Patir and Cheng (ASME J. Lubr. Technol., 100, pp. 12–17, 1978), or more recently Wang et al. (Tribol. Trans., 45(1), pp. 1–10, 2000), with good reported results compared with experimental data. To overcome certain limitations that become apparent at very small film thickness, notably when the roughness is two-dimensional, in 1995 Jai (Math. Modell. Numer. Anal., 29(2), pp. 199–233, 1995) introduced a new technique based on a rigorous homogenization theory in the case of compressible fluid flow. This procedure was further mathematically developed by Buscaglia and Jai (Math. Probl. Eng., 7(4), pp. 355–377, 2001) and applied to tribological problems by Jai and Bou-Saı¨d (ASME J. Tribol., 124, pp. 327–355, 2002). In this paper, we propose a similar homogenized approach in the case of non-Newtonian fluids to avoid numerical problems which are often encountered in other approaches. Results in the homogenized roughness case are obtained and compared with direct numerical solutions.
Improving Tribological Performance of Piston Rings by Partial Surface Texturing
Authors: Kligerman Y. , Etsion I. , Shinkarenko A.
Published: June 2005

An analytical model is developed to study the potential use of partial laser surface texturing (LST) for reducing the friction between a piston ring and cylinder liner. The hydrodynamic pressure distribution and the time-dependent clearance between the piston ring and cylinder liner are obtained from a simultaneous solution of the Reynolds equation and the ring equation of motion in the radial direction. The time behavior of the friction force is calculated from the shear stresses in the viscous fluid film and the time-dependent clearance. An intensive parametric investigation is performed to identify the main parameters of the problem. The optimum LST parameters such as dimples depth, texture area density, and textured portion of the nominal contact surface of the piston ring are evaluated.
Modeling and Identification of Gas Journal Bearings: Externally Pressurized Gas Bearing Results
Authors: Viktorov V. , Belforte G. , Raparelli T.
Published: June 2005

Static and dynamic characteristics of externally pressurized gas journal bearings with four supply orifices positioned at the central cross section for rotating shaft displacements near the bearing center are investigated. Results for transfer functions and for gas-film coefficients derived using the developed mathematical model are compared with the results derived from numerical computations of a nonlinear distributed parameter model of the gas bearings. Averaging and corrective coefficients are elaborated. The results obtained demonstrate that analytical data are in good agreement with the numerical data for the wide range of parameters and the mathematical model developed makes the simple calculation of static and dynamic characteristics of this type of externally pressurized gas bearings possible. Derived analytical relations for transfer functions and for gas-film coefficients of gas bearings provide an efficient means for designing rotor-bearing systems.
Combined Navier–Stokes and Bulk-Flow Analysis of Hybrid Bearings: Radial and Angled Injection
Authors: Hélène M. , Arghir M. , Frêne J.
Published: June 2005

The present work deals with the Navier–Stokes and bulk-flow analysis of hybrid bearings intended for use in aerospace applications. These bearings are expected to work at high rotational speeds and high feeding pressures. In such a case, the pressure in the shallow pockets of the bearing is no longer constant and is influenced by hydrostatic and hydrodynamic effects. It has been shown in the literature that the recess pressure pattern can have an important influence on the dynamic characteristics of the bearing. The present work investigates the pressure field in the recess of centered hybrid bearings with radial and angled injection by using a numerical Navier–Stokes analysis. The recess pressure pattern is then subsequently characterized by combining these results with some parametric descriptions. For calculating the dynamic characteristics of the bearing, the parametric pressure pattern is then injected into a bulk-flow model. The proposed model is an alternative analysis to the one advanced by San Andrés [ASME J. Tribole, 112, pp. 699–707; 119, 179–187] and in order to evaluate the validity of the bulk-flow code, the numerical predictions are compared with experimental data taken from the literature for radial and angled injection. The favourable effect of the counter-rotating angled injection is then explained by using the velocity field issued from the Navier–Stokes analysis and the pressure field given by the bulk-flow model.
Unsteady Analysis of a Mechanical Seal Using Duhamel’s Method
Authors: Salant Richard F. , Cao Bin
Published: June 2005

An unsteady numerical model of a mechanical seal, with mixed lubrication, has been developed. The thermal analysis is performed using Duhamel’s method in combination with a numerical experiment to determine Duhamel’s auxiliary function. The results using this semiempirical approach compare well with those from a finite element analysis. The model has been used to predict the performance of a mechanical seal during startup and shutdown.
Tribological Study of Microbearings for MEMS Applications
Authors: Kim Daejong , Cao Dongmei , Bryant Michael D. , Meng Wenjin , Ling Frederick F.
Published: June 2005

Microsleeve bearings intended for microrotational machinery were fabricated by X-ray lithography and Ni electroplating. Coated to the working surfaces of the bearings was a 900nm thick uniform tungsten hydrocarbon (W–C:H) coating using an inductively coupled plasma (ICP) assisted, hybrid chemical vapor deposition (CVD)/physical vapor deposition (PVD) tool. Tribological characteristics and mechanical properties of as-electrodeposited Ni microbearings, annealed Ni microbearings at 800°C, and W–C:H coated microbearings were investigated. Potential applications of the microbearings may involve very light contact pressure (5-30MPa) and high sliding speed, such as micromotors and microturbines. Conventional pin-on disk test methods on top flat surfaces, (001) planes, cannot effectively predict tribological characteristics because these microbearings use the sidewall (110 plane) as a working surface. A special micro wear tester and friction tester were developed. Surface morphologies of new and worn bearing surfaces were studied using SEM. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) characterized the W–C:H coated microbearings. Test results of the W–C:H coated microbearings (wear characteristics and friction) are also presented. W–C:H coated microbearings had much lower wear rate than uncoated bearings. During the wear test, a transfer layer formed on the counter steel shaft even under very small contact pressure, leading to low steady state friction and high wear resistance.
Experimental and Numerical Investigation of Dynamic Instability in the Head Disk Interface at Proximity
Authors: Ambekar Rohit , Gupta Vineet , Bogy David B.
Published: June 2005

As the flying height decreases to achieve greater areal density in hard disk drives, different proximity forces act on the air bearing slider, which results in fly height modulation and instability. Identifying and characterizing these forces has become important for achieving a stable fly height at proximity. One way to study these forces is by examining the fly height hysteresis, which is a result of many constituent phenomena. The difference in the touchdown and takeoff rpm (hysteresis) was monitored for different slider designs, varying the humidity and lubricant thickness of the disks, and the sliders were monitored for lubricant pickup while the disks were examined for lubricant depletion and modulation. Correlation was established between the observed hysteresis and different possible constituent phenomena. One such phenomenon was identified as the Intermolecular Force from the correlation between the lubricant thickness and the touchdown velocity. Simulations using 3D dynamic simulation software explain the experimental trends.
New Methodology to Evaluate the Rolling Contact Fatigue Performance of Bearing Steels With Surface Dents: Application to 32CrMoV13 (Nitrided) and M50 Steels
Authors: Nélias D. , Jacq C. , Lormand G. , Dudragne G. , Vincent A.
Published: June 2005

A new methodology is proposed to evaluate the rolling contact fatigue (RCF) performance of bearing steels in presence of surface dents. The experimental procedure consists of denting the raceway of test specimens with a hardness machine using spherical diamond tips of different radii (i.e., 200, 400, and 600μm) and with an applied normal load ranging from 5to50daN. Analysis of various dent geometries yield an analytical law with five parameters useful for fitting experimental profiles for contact simulation. Fatigue tests are conducted using a two-disk machine to study the effect of different operating conditions on RCF and to compare the performances of nitrided 32CrMoV13 steel versus M50 reference steel. A numerical investigation is conducted to analyze experimental result. Initially, the local residual stresses and plastic strains around the dent are obtained through finite element simulations of the indentation process. Second, the overrolling of the dent is simulated with a contact code. Finally, an indent-based endurance limit, called H1I, is proposed and comparisons are made with test results. Both RCF tests and numerical simulations show improved performance with nitrided 32CrMoV13 steel when compared to the M50 reference steel. The dominating role of sliding is also experimentally highlighted and two areas of damage initiation are identified. The effects of normal load and hoop stress are less marked.
Light and electron microscopy of teliospores and teliospore germination in the rust fungus Coleosporium ipomoeae
Authors: Mims C W , Richardson E A
Published: June 2005

A combination of light, scanning, and transmission electron microscopy was used to examine teliospores and teliospore germination in the rust fungus Coleosporium ipomoeae (Schw.) Burrill, a parasite of the wild morning glory Ipomoea coccinea L. Telia developed on abaxial surfaces of infected leaves and appeared as orange, waxy crusts usually associated with uredinia. Mature teliospores were cylindrical to slightly clavate in shape and thin-walled. The presence of chitin in the spore wall was demonstrated using wheat germ agglutinin gold labeling. Teliospores were surrounded by an electron-dense extracellular material. Each spore possessed a large prominent nucleus containing synaptonemal complexes indicative of prophase I meiotic nuclei. Following hydration, the nucleus of each spore completed meiosis and the spore was divided into four uninucleate compartments by the formation of three transverse septa. Each compartment gave rise to a germ tube into which the nucleus and cytoplasm migrated. Germ tubes developed into long slender sterigmata that grew through the extracellular material within the telium to become exposed on the leaf surface. A basidiospore then developed at the tip of each sterigma. Once the nucleus moved from the sterigma into the spore, a septum formed to delimit the spore from the tip of the sterigma.Key words: fungal spores, transmission and scanning electron microscopy, high pressure freezing.
Ultrastructure of the fertilized embryo sac in the dwarf mistletoe Arceuthobium americanum (Viscaceae) and development of the caecum
Authors: Ross Cynthia M , Sumner Michael J
Published: June 2005

Post-fertilization changes in the seven-celled embryo sac of the parasitic angiosperm Arceuthobium americanum Nutt. ex Engelm. were investigated with light, fluorescence, and electron microscopy. Two embryo sacs, of which only one is fertilized, are found within the reduced ategmic ovule (the placentalnucellar complex). All cells of the fertilized embryo sac developed thickened cellulosic and (or) hemicellulosic bounding walls and, aside from the degenerative synergid, acquired ultrastructure reflective of metabolically active cells. The filiform apparatus became thickened in the persistent synergid, and a similar structure developed in the antipodals. Unlike the changes observed in the zygote and central cell, those in the persistent synergid and antipodals were unusual, as these cells regularly degenerate after fertilization in a typical angiosperm; therefore, in A. americanum, they likely play a role in providing nutrition to the zygote and (or) central cell. A pouch-like outgrowth (caecum) initiated from the central cell near the primary endosperm nucleus and, after vacuolar expansion and intercellular growth, reached the base of the placentalnucellar complex in three days. The observation of mitochondria clusters within the central cell, caecum, and adjacent placentalnucellar complex cells suggests the caecum functions in embryo sac expansion and haustorial nutrient absorption.Key words: Arceuthobium, caecum, cell walls, fertilized embryo sac, mistletoe, ultrastructure.
Characterization of a nonphotosynthetic NADP-malic enzyme from germinating soybean cotyledons: interaction with a 94-kDa polypeptide identified as a lipoxygenase
Authors: Ferreyra María Lorena Falcone , Drincovich María Fabiana , Andreo Carlos S , Podestá Florencio E
Published: June 2005

The major NADP-malic enzyme (NADP-ME) isoform expressed in Glycine max L. cotyledons, leaves, and roots had a subunit molecular mass of 65 kDa and a pI of 6.9. The developmental profile of NADP-ME activity in cotyledons revealed a peak around day 7 post-imbibition (1.53 U·g1fresh mass, 33-fold that of day 1), declining markedly thereafter. NADP-ME was partially purified (33-fold) from 7-d germinated soybean cotyledons with a yield of 41% and a final specific activity of 2.8 U·mg1. NADP-ME had an optimal pH of 7.3 and the Kmvalues for NADP and L-malate were 33 µmol·L1and 0.78 mmol·L1, respectively. The high enzymatic activity found in soybean cotyledons suggests that it plays an important role prior to the establishment of photosynthesis. NADP-ME co-purified with a 94-kDa polypeptide (p94) through various chromatographic steps. Non-denaturing electrophoresis followed by SDS-PAGE and immunoprecipitation assays indicated that NADP-ME is physically associated with p94. Matrix-assisted laser desorption and ionization  time of flight MS of p94 tryptic peptides identified p94 as a lipoxygenase. Although the association was verified by different approaches, the functional role for such interaction is still speculative. Possible hypothesis are discussed.Key words: germinating cotyledon, isozyme, lipoxygenase, NADP-malic enzyme, proteinprotein interaction, soybean.
A forty-year journey in plant research: original contributions to flavonoid biochemistry
Authors: Ibrahim Ragai K
Published: June 2005

This review highlights original contributions by the author to the field of flavonoid biochemistry during his research career of more than four decades. These include elucidation of novel aspects of some of the common enzymatic reactions involved in the later steps of flavonoid biosynthesis, with emphasis on methyltransferases, glucosyltransferases, sulfotransferases, and an oxoglutarate-dependent dioxygenase, as well as cloning, and inferences about phylogenetic relationships, of the genes encoding some of these enzymes. The three-dimensional structure of a flavonol O-methyltransferase was studied through homology-based modeling, using a caffeic acid O-methyltransferase as a template, to explain their strict substrate preferences. In addition, the biological significance of enzymatic prenylation of isoflavones, as well as their role as phytoanticipins and inducers of nodulation genes, are emphasized. Finally, the potential application of knowledge about the genes encoding these enzyme reactions is discussed in terms of improving plant productivity and survival, modification of flavonoid profiles, and the search for new compounds with pharmaceutical and (or) nutraceutical value.Key words: flavonoid enzymology, metabolite localization, gene cloning, 3-D structure, phylogeny.
NONTEMPLATE-DEPENDENT POLYMERIZATION PROCESSES: Polyhydroxyalkanoate Synthases as a Paradigm
Authors: Stubbe JoAnne , Tian Jiamin , He Aimin , Sinskey Anthony J. , Lawrence Adam G. , Liu Pinghua
Published: June 2005

▪ Abstract  This review focuses on nontemplate-dependent polymerases that use water-soluble substrates and convert them into water-insoluble polymers that form granules or inclusions within the cell. The initial part of the review summarizes briefly the current knowledge of polymer formation catalyzed by starch and glycogen synthases, polyphosphate kinase (a polymerase), cyanophycin synthetases, and rubber synthases. Specifically, our current understanding of their mechanisms of initiation, elongation (including granule formation), termination, remodeling, and polymer reutilization will be presented. General underlying principles that govern these types of polymerization reactions will be enumerated as a paradigm for all nontemplate-dependent polymerizations. The bulk of the review then focuses on polyhydroxyalkanoate (PHA) synthases that generate polyoxoesters. These enzymes are of interest as they generate biodegradable polymers. Our current knowledge of PHA production and utilization in vitro and in vivo as well as the contribution of many proteins to these processes will be reviewed.
THE STRUCTURE AND FUNCTION OF SMC AND KLEISIN COMPLEXES
Authors: Nasmyth Kim , Haering Christian H.
Published: June 2005

▪ Abstract  Protein complexes consisting of structural maintenance of chromosomes (SMC) and kleisin subunits are crucial for the faithful segregation of chromosomes during cell proliferation in prokaryotes and eukaryotes. Two of the best-studied SMC complexes are cohesin and condensin. Cohesin is required to hold sister chromatids together, which allows their biorientation on the mitotic spindle. Cleavage of cohesin's kleisin subunit by the separase protease then triggers the movement of sister chromatids into opposite halves of the cell during anaphase. Condensin is required to organize mitotic chromosomes into coherent structures that prevent them from getting tangled up during segregation. Here we describe the discovery of SMC complexes and discuss recent advances in determining how members of this ancient protein family may function at a mechanistic level.
Improved Attachment of Natural HCV Isolate to Daudi Cells upon Elimination of Immune Complexes and Close pH Control
Authors: Quer Josep , Cos Joan , Murillo Pedro , Esteban Juan Ignacio , Esteban Rafael , Guardia Jaume
Published: June 2005

Objectives: To study the viral requirements for attachment, entry and infection using natural isolates of HCV (infectious plasma of a patient infected with HCV from genotype 1b) and a cell line which has previously been shown to support HCV replication (Daudi cells). Methods: We studied attachment of HCV to Daudi cells, a human B-cell line. Quantification was done by real-time RT-PCR. Results: The best attachment levels were obtained using plasma depleted of immunocomplexes. Results of kinetics of HCV attachment to Daudi cells show that attachment is maximum at pH 7.0, and that it decreased drastically at any other pH studied (5.5, 6.0, 6.5, 7.5 and 8.0). Conclusions: Depletion of immunocomplexes and pH control during infection are important parameters to improve attachment of HCV to Daudi cells using plasma as a natural source of virus.
Selective Cytolysis of Tumor Cells by Mumps Virus S79
Authors: Yan Yin-Fang , Chen Xiao , Zhu Ying , Wu Jian-Guo , Dong Chang-Yuan
Published: June 2005

We studied the sensitivity of several human cancer cell strains (HeLa, HT1080, SPC-A1, and ACHN) and normal cell strains (MRC-5 and Wish) to mumps virus (MuV) S79, a live attenuated vaccine strain. These cells exhibited a differential sensitivity to infection with MuV, and the susceptible sequences were ACHN > HeLa > HT1080 > SPC-A1 > Wish > MRC-5. In experiments in vivo, nude mice with HT1080 fibrosarcoma xenografts were randomly divided into three groups for intratumoral treatment with MuVS79, UV-inactivated MuVS79, and PBS. At 107 PFU, live MuVS79 injection caused in 7 of 9 mice complete regression by day 15 while rapid tumor growth occurred in all 9 mice treated with PBS. Rapid tumor progression also occurred in all 8 mice treated with UV-inactivated virus; however, tumor growth was delayed in the logarithmic phase relative to the PBS-treated tumors.
Development and Evaluation of a Sensitive PCR-ELISA for Detection of Adenoviruses in Feces
Authors: Metzger-Boddien Christoph , Kehle Johannes
Published: June 2005

Objective: Most of the PCR-based assays for the detection of adenoviruses require gel electrophoresis for resolution, which is time- and work-consuming and interpretation difficulties often occur. Therefore our objective was to develop and evaluate a PCR-ELISA for broad detection of adenoviruses, that is easy to perform and leads to an increase of specificity in virus detection. Methods: A total of 64 fecal specimens from patients with acute gastroenteritis, previously tested negative for other viruses than adenovirus and for bacterial pathogens, were tested for adenovirus in parallel with an Antigen-ELISA, virus isolation in cell culture, with a previously published hybridization-based PCR and our newly developed semi-nested PCR-ELISA. Results: The new PCR-ELISA turned out to be the best method with 26 samples positive for adenovirus. Of these, 22 became positive by Ag-ELISA, 19 by virus isolation in cell culture and only 14 by the previously published hybridization-based PCR. Conclusion: The semi-nested PCR-ELISA is a sensitive, reliable and rapid method for the detection of enteric adenoviruses from fecal samples.
Efficient Therapeutic Gene Expression in Cultured Rat Hippocampal Neurons Mediated by Human Foamy Virus Vectors: A Potential for the Treatment of Neurological Diseases
Authors: Liu Wanhong , He Xiaohua , Cao Zhijian , Sheng Jiqun , Liu Hui , Li Zhi , Li Wenxin
Published: June 2005

Vectors derived from human foamy virus (HFV), with their nonpathogenic nature and a wide tissue tropism, have been successfully used as retroviral gene transfer vehicles. However, transduction of primary hippocampal neurons (HNs) with HFV vectors has little been studied. To investigate the potential of HFV-derived vector in gene therapy for neurological diseases, efficient foreign gene expression in cultured rat HNs was first demonstrated by successful enhanced green fluorescent protein (EGFP) transduction through a HFV vector bearing an EGFP expression cassette. Furthermore, we tested the effect on HNs that were transduced by a novel HFV vector expressing the human glutamic acid decarboxylase (GAD) cDNA, a therapeutic gene for neurological disorders such as epilepsy and Parkinson’s disease. The transduced HNs showed significant increase in isoform-specific expression of GAD, synthesis of γ-aminobutyric acid (GABA) and stimulation-evoked GABA release. These findings indicated for the first time that cultured rat HNs could be efficiently transduced by HFV vectors, and the GAD-expressing HFV vector has potential therapeutic value in the treatment of neurological diseases.
Inhibition of Influenza-Virus-Induced Apoptosis in Chorion Cells of Human Fetal Membranes by Nordihydroguaiaretic Acid
Authors: Uchide Noboru , Ohyama Kunio , Bessho Toshio , Toyoda Hiroo
Published: June 2005

Objectives: It has been postulated that the pathogenesis of influenza virus infection involves not only the virus-proliferation-mediated apoptotic cell death in infected cells, but also a direct reactive oxygen species (ROS)-induced cellular injury in the infected organs. We examined effects of an antioxidant, nordihydroguaiaretic acid (NDGA), on apoptosis induction and viral proliferation. Subsequently, the results were compared with those of pyrrolidine dithiocarbamate (PDTC), another antioxidant. Methods: The levels of ROS production were measured with 2′,7′-dichlorofluorescein diacetate; apoptosis induction and viral proliferation were analyzed by DNA fragmentation and plaque-forming assays, respectively. Results: The treatment of infected cells with NDGA inhibited ROS overproduction, apoptotic DNA fragmentation and virus proliferation. The maximum inhibition against DNA fragmentation (76%) was observed with 500 µM NDGA. The antiviral activity of NDGA against influenza virus was more potent than that of PDTC. Conclusions: The present study, therefore, suggests for the first time that NDGA, a known antioxidant reagent, inhibits the induction of apoptosis in human fetal membrane chorion cells infected with influenza virus through the more potent antiviral activity than that of PDTC.
Report of the National Heart, Lung, and Blood Institute Working Group on Outcomes Research in Cardiovascular Disease
Authors: Krumholz Harlan M. , Peterson Eric D. , Ayanian John Z. , Chin Marshall H. , DeBusk Robert F. , Goldman Lee , Kiefe Catarina I. , Powe Neil R. , Rumsfeld John S. , Spertus John A. , Weintraub William S.
Published: June 2005

The National Heart, Lung, and Blood Institute convened a working group on outcomes research in cardiovascular disease (CVD). The working group sought to provide guidance on research priorities in outcomes research related to CVD. For the purposes of this document, “outcomes research” is defined as investigative endeavors that generate knowledge to improve clinical decision making and healthcare delivery to optimize patient outcomes. The working group identified the following priority areas: (1) national surveillance projects for high-prevalence CV conditions; (2) patient-centered care; (3) translation of the best science into clinical practice; and (4) studies that place the cost of interventions in the context of their real-world effectiveness. Within each of these topics, the working group described examples of initiatives that could serve the Institute and the public. In addition, the group identified the following areas that are important to the field: (1) promotion of the use of existing data; (2) facilitation of collaborations with other federal agencies; (3) investigations into the basic science of outcomes research, with an emphasis on methodological advances; (4) strengthening of appropriate study sections with individuals who have expertise in outcomes research; and (5) expansion of opportunities to train new outcomes research investigators. The working group concluded that a dedicated investment in CV outcomes research could directly improve the care delivered in the United States.
The MIMIC Model as a Method for Detecting DIF: Comparison With Mantel-Haenszel, SIBTEST, and the IRT Likelihood Ratio
Authors: Finch Holmes
Published: June 2005

This study compares the ability of the multiple indicators, multiple causes (MIMIC) confirmatory factor analysis model to correctly identify cases of differential item functioning (DIF) with more established methods. Although the MIMIC model might have application in identifying DIF for multiple grouping variables, there has been little examination of how well the technique works in terms of correct and incorrect identification of DIF. A Monte Carlo methodology is used in this study, with manipulation of the number of items, number of examinees, differences between the mean abilities of the reference and focal groups, level of DIF contamination of the anchor items, and amount of DIF in the target item. Results indicate that the MIMIC model is effective for DIF identification for 50 items or when the two-parameter logistic model underlies the data but has a very high rate of incorrect DIF identification for 20 items with three-parameter logistic data.
Exploring Local Item Dependence Using a Random-Effects Facet Model
Authors: Wang Wen-Chung , Wilson Mark
Published: June 2005

The random-effects facet model that deals with local item dependence in many-facet contexts is presented. It can be viewed as a special case of the multidimensional random coefficients multinomial logit model (MRCMLM) so that the estimation procedures for the MRCMLM can be directly applied. Simulations were conducted to examine parameter recovery and effects of model misspecification. Results indicated that the item and person parameters as well as the random effects could be recovered very accurately when the data were analyzed using the generating random-effects facet model. When local item dependence was ignored and the standard facet model was used, the parameter estimates were shrunken and the test reliability was overestimated. Two empirical examples about journal quality ratings and rater effects are given to illustrate implications and applications of the proposed random-effects facet model.