bluuebunny/crossref_metadata_2025 huggingface dataset:
Non-Linear Stress Analysis of Complex Umbilical Cross-Sections
Authors: Sævik Svein , Ekeberg Knut I.
Published: March 2009

Nexans Norway is, together with Marintek, currently developing a software for detailed analysis of complex umbilical cross-section designs. The software development project combines numerical methods with small-scale testing of involved materials, as well as full-scale testing of a wide variety of umbilical designs, essential for calibration and verification purposes. Each umbilical design is modelled and comparisons are made with respect to global behaviour in terms of: • Axial strain versus axial force; • Axial strain versus torsion; • Torsion versus torsion moment for various axial force levels; • Moment versus curvature for different tension levels. The applied theory is based on curved beam and curved axisymmetric thin shell theories. The problem is formulated in terms of finite elements applying the Principle of Virtual Displacements. Each body of the cross-section interacts with the other bodies by contact elements which are formulated by a penalty formulation. The contact elements operate in the local surface coordinate system and include eccentricity, surface stiffness and friction effects. The software is designed to include the following functionality: • Arbitrary geometry modelling including helical elements wound into arbitrary order; • The helical elements may include both tubes and filled bodies; • Elastic, hyper-elastic, and elastic-plastic material models; • Initial strain; • Contact elements, including friction; • Tension, torsion, internal pressure, external pressure, bending and external contact loading (caterpillars, tensioners, etc.). The paper focuses on the motivation behind the development program including a description of the different activities. The theory is described in terms of kinematics, material models and finite element formulation. A test example is further presented comparing predicted behaviour with respect to full-scale test results.
One Step Further: 500 MPa Yield Strength Steel for Offshore Constructions
Authors: Hanus F. , Schu¨tz J. , Schu¨tz W.
Published: March 2009

Essential savings in time and money can be achieved if the topside of an offshore platform can be installed in a single piece. For the projects Grane and Valhall located in the North Sea this goal could only be met by using steels with a minimum yield strength of 500 MPa. At the same time the steel should be as easily weldable as the 420 MPa TMCP steel that had become a common offshore steel grade in Norway during the last decade. Based on profound experience in TMCP and research programmes on weldability a chemical composition was selected promising to scope the requirements for base material and HAZ. A few plates were first produced and tested successfully. Excellent weldability in terms of HAZ toughness and low preheat was proven through a vast qualification programme and test welds at the yards. In the first part of the 3500 t order for Valhall the process parameters were optimised to achieve stable properties for the whole thickness range from 15 to 80 mm. The development of this steel grade S500M3z, the results and experience gained on the first deliveries shall be presented in the paper.
Flow Assurance of Wet Gas Pipelines From a Corrosion Viewpoint
Authors: Nyborg Rolf , Dugstad Arne
Published: March 2009

In many offshore oil and gas projects under development, the pipeline costs are a considerable part of the investment and can become prohibitively high if the corrosivity of the fluid necessitates the use of corrosion resistant alloys instead of carbon steel. Development of more robust and reliable methods for internal corrosion control can increase the application range of carbon steel and therefore have a large economic impact. Corrosion control of carbon steel pipelines has traditionally often been managed by the use of corrosion inhibitors. The pH stabilization technique has been successfully used for corrosion control of several large wet gas condensate pipelines in the last few years. Precipitation of scale and salts in the pipeline and process equipment creates further challenges when formation water is produced. Different corrosion prediction models are used in the industry to assess the corrosivity of the transported fluid. An overview of the present models is given together with a link to fluid flow modeling.
The Open Sea Tests of the Offshore Floating Type Wave Power Device “Mighty Whale”: Performance of the Prototype
Authors: Ogata Teruhisa , Washio Yukihisa , Osawa Hiroyuki , Tsuritani Yasushi , Yamashita Seiya , Nagata Yoshinori
Published: March 2009

This paper presents the characteristics of wave conditions, wave energy absorption, response of hull-motion and wave height dissipation based on the results of the open sea tests. 0.5–1.0m of significant wave height and 6–7 seconds of significant wave period appear the most predominant, and average wave energy is estimated 4.88kW/m around the test site. Average power output for the test is approximately 6kWh and the maximum total energy efficiency is around 15% that is ranging from 6–7 seconds of significant wave period. Slow drift oscillation of hull was observed motion in surge, sway and yaw and the value of its amplitude almost equal to estimated values in design stage. Then the mean value of transmission coefficient is about 0.8 under 8.0 seconds of significant wave period. We are considering that the results of the tests should be useful for optimum design of an offshore floating type wave power device.
Potential Dependence of Hydrogen Embrittlement Susceptibility of Ultra High Strength Low Alloy Steel
Authors: Komazaki Shin-ichi , Maruyama Rie , Honno Tatsuo , Misawa Toshihei
Published: March 2009

In order to investigate the susceptibility of the ultra high strength low alloy steel to hydrogen embrittlement, a slow strain rate tensile test was carried out in boric acid-borax buffer aqueous solutions of pH 10 at the potential range from corrosion potential to hydrogen gas evolution potential, including adsorbed hydrogen potential. Experimental results revealed that the susceptibility to hydrogen embrittlement was dependent on the applied potential and increased linearly with increasing applied cathodic potential in the adsorbed hydrogen potential region. On the other hand, in the hydrogen gas evolution potential region, the susceptibility was independent of the applied potential and showed almost no variation. Based on the results obtained, these changes in susceptibility to hydrogen embrittlement with applied potential have been discussed in terms of the variation in reduction behavior of oxide films on the specimen surface.
The Spectral Wave Climate in the Barents Sea
Authors: Lopatoukhin Leonid , Rozhtov Valentine , Boukhanovsky Alexander , Degtyarev Alexander , Sas’kov Kirill , Athanassoulis Gerassimos , Stefanakos Christos , Krogstad Harald E.
Published: March 2009

Based on hindcast Barents Sea wave fields, an approach to a directional spectral wave climate description is proposed. A set of classes of climatic wave spectra are identified and the probability of occurrence of spectra in each class is determined. The spatial and temporal variability of the climatic wave spectral parameters for the different classes are considered to be non-random functions of underlying random arguments.
Identifying VIV Vibration Modes by Use of the Empirical Orthogonal Functions Technique
Authors: Kleiven Gudmund
Published: March 2009

The Empirical Orthogonal Functions (EOF) technique has widely being used by oceanographers and meteorologists, while the Singular Value Decomposition (SVD being a related technique is frequently used in the statistics community. Another related technique called Principal Component Analysis (PCA) is observed being used for instance in pattern recognition. The predominant applications of these techniques are data compression of multivariate data sets which also facilitates subsequent statistical analysis of such data sets. Within Ocean Engineering the EOF technique is not yet widely in use, although there are several areas where multivariate data sets occur and where the EOF technique could represent a supplementary analysis technique. Examples are oceanographic data, in particular current data. Furthermore data sets of model- or full-scale data of loads and responses of slender bodies, such as pipelines and risers are relevant examples. One attractive property of the EOF technique is that it does not require any a priori information on the physical system by which the data is generated. In the present paper a description of the EOF technique is given. Thereafter an example on use of the EOF technique is presented. The example is analysis of response data from a model test of a pipeline in a long free span exposed to current. The model test program was carried out in order to identify the occurrence of multi-mode vibrations and vibration mode amplitudes. In the present example the EOF technique demonstrates the capability of identifying predominant vibration modes of inline as well as cross-flow vibrations. Vibration mode shapes together with mode amplitudes and frequencies are also estimated. Although the present example is not sufficient for concluding on the applicability of the EOF technique on a general basis, the results of the present example demonstrate some of the potential of the technique.
Application of Reliability-Based Techniques in MODU/MOPU Design
Authors: Morandi Alberto
Published: March 2009

Reliability based techniques have been extensively used in the assessment and re-assessment of existing offshore structures as well as in the calibration of design standards, particularly those adopting an LRFD format. At a design level, however, such techniques are yet to find a more widespread application. As far as mobile drilling unit (MODU) or mobile production unit (MOPU) concepts are concerned, the challenge is to model the complex behavior of the unit considering several different attributes, constraints and objectives. The paper outlines recent progress in reliability based techniques that may be used in future designs as well as the current limitations that need to be overcome before such techniques are more widely accepted by designers.
State-of-the-Art on Deep Water Thermal Insulation Systems
Authors: Grealish Frank , Roddy Iggy
Published: March 2009

There are currently a wide variety of insulation systems available for deep water subsea applications. These systems are applied in a number of different configurations including externally bonded systems, pre-manufactured insulation modules that are strapped on to subsea structures and pipe-in-pipe (PIP) insulation systems. The most common insulation materials include polymers such as polyurethane, epoxies and polypropylene and for deep water applications these are used in two main forms; syntactic foam and composite syntactic foam. The limits associated with current insulation systems include lack of experience on the performance of these systems in long-term deepwater service and relatively low temperature limits when exposed to hot/wet conditions. At present, tests for assessing their thermal and physical properties are manufacturer-dependent and, for a purchaser of such systems, need to be interpreted across a range of existing and new materials and manufacturer specifications. The immediate and long-term effects of temperature, hydrostatic pressure and environmental exposure are not yet fully understood. Currently there is a lack of agreed-upon standards for insulation materials. There is a requirement in the industry for the development of consistent standards for the specification, design, materials, manufacturing and testing of insulation materials and systems. To address this requirement a Joint Industry Project (JIP) commenced in April 2000 to develop a new industry wide standard for insulation and buoyancy materials, designated the InSpec JIP. Twenty companies are participating in the JIP, including nine oil companies, eight manufacturers of insulation/buoyancy products and three contractors. This paper presents a review of the current state-of-the-art for thermal insulation systems for deep water applications. The capabilities of alternative systems are reviewed and evaluated. The key issues associated with each system type and critical parameters for the most common insulation materials are presented and discussed. The development of industry standards within the InSpec JIP to address the critical issues for qualification is highlighted within this paper.
Tailor Made Freak Waves Within Irregular Seas
Authors: Kuehnlein Walter L. , Clauss Gu¨nther F. , Hennig Janou
Published: March 2009

The paper presents a nonlinear technique for generating high and highest freak waves by using deterministic wave packets which are also embedded into irregular seas. First, the technique is developed for small water elevations with a linear description of the wave. Afterwards the method is extended to a nonlinear description based on the introduction of a “wave information” which includes the (linear) information of waves as Fourier Transforms. Combined with a modified wave celerity (information speed) the propagation of high waves can be developed by using Stokes higher order solutions or semi empirical expansion equations. As a result, the nonlinear wave contours, registrations and associated wave data are derived from the respective wave information. As the mentioned methods are not only used as a theoretical approach for describing steep wave trains a wide range of applications for generating high deterministic waves in model basins is presented. Thus extreme waves with heights of more than 3 m have been generated. This technique has also been adapted for the demands of computer controlled seakeeping tests. As both model and wave probe do not necessarily move at the same velocity, a time domain procedure is introduced for transforming the registration of the wave elevation from the wave probe posi-tion to the model position which leads, especially in astern and quartering seas, to extraordinary wave contours experienced by a moving vessel.
Experiments on Deep-Water Waves With Two-Dimensional Surface Patterns
Authors: Hammack Joseph L. , Henderson Diane M.
Published: March 2009

Experiments are conducted in a three-dimensional wave basin with a wavemaker system comprising 32 side-by-side paddles for which there is precise control. Two types of wavemaker forcings are used to create two-dimensional surface patterns: (1) two symmetric carrier waves interacting at an oblique angle and (2) a single carrier wave propagating in the x-direction with a Jacobi elliptic, sn-function modulation in the y-direction. Data are presented from overhead photographs and from time series obtained by traversing a wave-gage through the patterns. Two parameters are systematically varied: the horizontal aspect ratio of the cells comprising the surface pattern and the measure of nonlinearity of the input wavefield. Unlike such waves in shallow water for which the surface pattern is made up of six-sided cells, the wave pattern for waves in deep water is made up of rectangular cells. Both the overhead photographs and the time series show that for most values of the two parameters, the wavefields evolve with significant modulations in both the x and y directions. In particular, when the aspect ratio of the cells is below about 0.4 for a fixed measure of nonlinearity, there is significant modulation in the y-direction that results in cells with smaller aspect ratios. For aspect ratio above about 0.4, the cells appear to be stable (except for viscous decay) for smaller values of nonlinearity. However, for larger values of nonlinearity even these cells modulate in the y-direction, further increasing the aspect ratio of the evolving cells. For the largest value of nonlinearity considered, the pattern evolves into one that comprises cells with aspect ratios of about 1.
Sensitivity of the Expected Ships Availability to Different Seakeeping Criteria
Authors: Fonseca Nuno , Soares Carlos Guedes
Published: March 2009

The paper presents a methodology to calculate the seakeeping performance of ships, which is given as an operability index, and discusses the sensitivity of the results to the use of different seakeeping criteria. The calculation of the operability index, which represents the percentage of time during which the ship is operational, depends on the wave climate of the ocean area where the ship operates, the dynamic response of the ship to the waves, and the ship mission. The relation between the ship operability and the mission characteristics is established through the seakeeping criteria. The calculation of operability indexes and the sensitivity analysis are carried out for a containership operating in the North Atlantique between Europe and the United states, and a fishing vessel operating near the Portuguese west coast. These are two ships with different mission profiles, which permits assessment of the sensitivity of the estimated operability index to different ship types.
Mooring- and Riser-Induced Damping in Fatigue Seastates
Authors: Garrett D. L. , Gordon R. B. , Chappell J. F.
Published: March 2009

Viscous damping due to drag on mooring lines and risers is seastate dependent and significantly affects the motion of a floating platform in deep water, particularly in everyday seastates. This in turn impacts design of the risers, which are typically controlled by fatigue. The dynamic interaction between the platform, mooring and risers cannot be evaluated using conventional uncoupled analysis tools, where each is analyzed separately. Rather, coupled analysis is required to provide a consistent way to model the drag-induced damping from mooring lines and risers. We describe a coupled, frequency domain approach (RAMS – Rational Approach to Marine Systems) for calculating the dynamic response of vessel, mooring and risers. In coupled analysis, the risers and mooring lines are included in the model along with the floater. In this way, damping of the floater motion due to drag on the mooring lines and risers is incorporated directly. It is also valuable to estimate the linear damping factors from the full, coupled analysis results. These damping factors may then, for example, be used in an equivalent linear model of the floating system in which the stiffness and damping effects of the mooring and risers are represented as additions to the floater stiffness and damping matrices. Such a model could be used to efficiently design a subsystem (e.g.; an export riser). We describe a technique to determine the equivalent linear damping factors from the coupled analysis results. This paper also illustrates the use of these methods for a West Africa FPSO. The need for coupled analysis is shown by comparing results from the fully coupled model with those obtained using an uncoupled method in which the mooring line damping is approximated.
A Three-Dimensional Finite Element Analysis of Unburied Flexible Flowline: A Case Study
Authors: Zhang Wenchao , Tuohy Justin
Published: March 2009

Pipelines in the service of conveying hot fluid will tend to expand due to pressure and differential temperature. However, since the flowline is generally fixed at the end terminations to rigid structures or equipment, such an expansion will be restricted in longitudinal direction. This is particularly the case for the section remote from the pipe ends, and results in an axial compression in the pipe section. In many cases, a subsea flowline has to be trenched or buried for the purposes of protection and thermal insulation. Consequently, the lateral movement of a flexible flowline is greatly limited, and an upward displacement is encouraged that may become excessive. Eventually, the flowline may lift out of the trench when the uplift resistance provided by the backfill cover and self-weight of the flowline is gradually overcome by the strain energy built up in the flowline. For flexible pipe, it is this excessive upward deformation being termed as the Upheaval Buckling, which can be prevented by employing adequate downward restraint, such as sand bag/rock dump or by designing a subsea pipe route to overcome this phenomenon. In this paper a case study of the full three-dimensional finite element analysis of a trenched but unburied 6.0-inch production flowline is presented following a description of Wellstream Finite Element Method (FEM) based methodology for Upheaval Buckling analysis of flexible pipes. The effect Bending Stiffness Hysteresis and Upheaval Creep–unique to flexible pipe characteristics, is considered in addition to the general loads such as the flowline self-weight and backfill, pretension, pressure, temperature distribution and prescribed forces (either concentrated or distributed) and displacements. The effects of environmental loads, such as the action of currents that would result in scouring off the backfill, can also be addressed. The finite element analysis program package ANSYS was chosen for this case study due to its special feature of ANSYS Parametric Design Language (APDL) and contact/target elements; and the general three-dimensional shell and solid elements were used to represent the flexible pipe and trench soil respectively.
Polyamide 11: A High Tenacity Thermoplastic, Its Material Properties and the Influence of Ageing in Offshore Conditions
Authors: Werth Michael , Hochstetter Gilles , Dang Patrick , Chedozeau Nathalie
Published: March 2009

Polyamide 11 is a key material in the fabrication of offshore flexible pipes. It is mainly used as the flexible pressure layer assuring the impermeability of the fluid and gas carrying flexible pipe. A further important use is as outer sheath material where it protects efficiently the metal strip structure from sea water ingress even in highly dynamic applications. Given these important functions of polyamide 11 the knowledge of its precise material properties is essential for the design and the operating limits of flexible pipes. This paper aims to give a detailed understanding of the scope of the material properties such as fracture toughness, fatigue resistance and the mechanical response function. In a further step the influence of ageing on these properties is outlined with the aid of aged model specimen studies.
Remotely Operated Underwater Thermal Cutting Processes for the Decommissioning of Large North Sea Platforms
Authors: Frazer Ian , Fyffe Lindsey , Gibson Oliver J. , Lucas Bill
Published: March 2009

A study has demonstrated the automation of underwater thermal cutting processes for remote decommissioning operations. The first phase of cutting trials evaluated five cutting processes underwater (air plasma, oxy-hydrogen, flux-cored arc, oxy-petrol and Kerrie cable systems). In the second phase, three manual cutting systems (oxy-petrol, “Broco” type system and Kerrie cable) were adapted for operation by a manipulator arm of the type commonly used offshore on Remotely Operated Vehicles. This manipulator, which usually requires a human operator, was interfaced to computer simulation and control software. The results of underwater cuts on steel plate using these systems are discussed, with applicability to offshore decommissioning. Ongoing work using other novel thermal cutting processes is also described.
Statistics for the Draupner January 1995 Freak Wave Event
Authors: Hagen O̸istein
Published: March 2009

The wave time series recorded at “Draupner”, January 1, 1995 at 15:20 exhibits an unsymmetrical, freak wave event. The statistics of the peak event is studied within the framework of traditional non-Gaussian process models. Assuming that the sea surface is adequately described by (one of) commonly applied non-Gaussian wave models, the paper shows that the probability of occurrence of a freak event like the one observed at Draupner January 1995 is very low.
Coupling Between In-Line and Transverse VIV Response
Authors: Huse Erling , Nielsen Finn Gunnar , So̸reide Tore
Published: March 2009

Most present-day programs for engineering prediction of VIV response are based on experimental lift and mass coefficients derived from 2D tests, where the cylinder has been constrained in in-line direction. The present paper describes a preliminary investigation into the coupling between in-line and transverse VIV response. A simple pendulum test set-up was used to study how the in-line response influenced the transverse one. For reduced velocities above 5, when the in-line oscillation frequency was exactly twice the transverse frequency, it was found that the transverse response was significantly reduced when allowing the cylinder to oscillate in both directions simultaneously, compared to the case when it was constrained in-line.
Installation and Pull-Out Capacities of Drag-In Plate Anchors
Authors: Elkhatib Sarah , Lonnie Breyden , Randolph Mark
Published: March 2009

The trend towards taut-wire mooring systems, instead of catenary chains, to anchor floating facilities for offshore exploration requires high-capacity anchoring systems capable of withstanding vertical loading components. Conventional drag anchors have very limited vertical capacity, and this has led to the development of alternative drag-in plate anchors, or vertically loaded anchors (VLAs). VLAs are installed in a similar way to conventional drag anchors, but they are ultimately loaded normal to their plate surface, and thus act like embedded plate anchors. A critical issue in the overall mooring system design is the ratio of the pull-out load to the anchor installation load, and this is termed the performance ratio. The performance of a model VLA was modelled in a geotechnical centrifuge, with particular attention to the performance ratios. Whilst the performance ratios obtained were much lower than expected, the testing proved that VLAs provide a simple and inexpensive alternative to other anchoring systems.
Navier-Stokes Predictions of the NREL Phase VI Rotor in the NASA Ames 80-By-120 Wind Tunnel
Authors: So̸rensen N. N. , Michelsen J. A. , Schreck S.
Published: March 2009

The application of an incompressible Reynolds Averaged Navier-Stokes solver to cases from the NREL/NASA Ames wind tunnel test is described. Six cases of the NREL PHASE-VI rotor in the upwind configuration under zero yaw and zero degrees tip pitch are computed. Favorable comparison of the computed results with measurements in the form of shaft torque, root moments, spanwise force distributions, and pressure distributions are shown. The good agreement documents the feasibility of 3D CFD computations in connection with prediction of the performance of new rotors. Additionally it is shown how CFD computations can be used to determine the three dimensional effects in rotor flows.
An Examination of Key Aerodynamic Modeling Issues Raised by the NREL Blind Comparison
Authors: Coton Frank N. , Wang Tongguang , Galbraith Roderick A. McD.
Published: March 2009

This paper describes some recent work undertaken in the aftermath of the ‘blind comparison’ with the NREL Unsteady Aerodynamics Experimental data collected in the NASA Ames wind tunnel. The data set collected in the NASA Ames tunnel represents a unique opportunity for aerodynamic modelers to enhance the capability of prediction schemes by comparison with ‘clean’ aerodynamic data. In this paper, the sensitivity of the results predicted by the Glasgow University prescribed wake model (HAWTDAWG) to a range of parameters including the blade section aerodynamic data is examined with reference to the measured data. In addition, specific modeling considerations highlighted by the measured data set are also discussed.
Aerodynamic Simulations of Wind Turbines Operating in Atmospheric Boundary Layer With Various Thermal Stratifications
Authors: Alinot Cedric , Masson Christian
Published: March 2009

This paper presents a numerical method for performance predictions of wind turbines immersed into stable, neutral, or unstable atmospheric boundary layer. Tile flowfield around a turbine is described by the Reynolds’ averaged Navier-Stokes equations complemented by the k-ε turbulence model. The density variations are introduced into the momentum equation using the Boussinesq approximation and appropriate buoyancy terms are included into the k and ε equations. An original expression for the closure coefficient related to the buoyancy production term is proposed in order to improve the accuracy of the simulations. The turbine is idealized as actuator disk surface, on which external surficial forces exerted by the turbine blade on the flow are prescribed according to the blade element theory. The resulting mathematical model has been implemented in FLUENT. The results presented in the paper include the power output and wake development under various thermal stratifications of an isolated wind turbine. In stable stratification, the power output is 4% lower than in neutral condition, while in unstable situation, the power is 3% larger. The predicted wake velocity defects are qualitatively in agreement with experimental observations.
Short-Term Power Fluctuations of Large Wind Power Plants
Authors: Wan Yih-Huei , Bucaneg Demy
Published: March 2009

With electric utilities and other power providers showing increased interest in wind power and with growing penetration of wind capacity into the market, questions about how wind power fluctuations affect power system operations and about wind power’s ancillary services requirements are receiving lots of attention. To evaluate short-term wind power fluctuations and the range of ancillary service of wind power plants, the National Renewable Energy Laboratory (NREL), in cooperation with Enron Wind, has started a project to record output power from several large commercial wind power plants at the 1-Hertz rate. The project’s purpose is to acquire actual, long-term wind power output data for analyzing wind power fluctuations, frequency distribution of the changes, the effects of spatial diversity, and wind power ancillary services. This paper presents statistical properties of the data collected so far and discusses the results of data analysis. Although the efforts to monitor wind power plants are ongoing, we can already conclude from the available data that despite the stochastic nature of wind power fluctuations, the magnitudes and rates of wind power changes caused by wind speed variations are seldom extreme, nor are they totally random. Their values are bounded in narrow ranges. Power output data also show significant spatial variations within a large wind power plant.
Pattern-dependent maternal plastid inheritance in Pennisetum americanum
Authors: Subrahmanyam N. C. , Satyaprasad M. , Rao S. Appa , Mengesha M. H.
Published: March 2009

The descendents of the "stripe" mutant of Pennisetum americanum consisted of green, variegated, and yellow seedlings. Variegation pattern differed from plant to plant, from tiller to tiller within a plant, and from leaf to leaf on the same tiller. The chlorophyll content (A663 per square decimetre) also differed among the variegated plants and leaves. The progeny from each of the variegated plants consisted of green, yellow, and variegated seedlings in varying proportions. In general, more green progeny were recovered from plants with wider green sectors in their top two leaves and more yellow seedlings were recovered from plants with top leaves showing wider yellow sectors. However, variegated seedlings were predominant among the progeny of plants exhibiting a greater number of interspersions of green and yellow stripes, irrespective of the total area of each colour. The variations in the proportions of different progeny are dependent upon the variegation pattern and the chlorophyll content of the top two leaves. The production of exclusively yellow seedlings from yellow spikelets irrespective of pollen source and the reciprocal differences in the interspikelet crosses suggest maternal plastid inheritance. Thus, the breeding behaviour of the variegated plants and the results of interspikelet crosses indicate a pattern-dependent maternal plastid inheritance.
A rapid staining technique for assessment of ectomycorrhizal infection of oak roots
Authors: Daughtridge Ann Todd , Boese Steven R. , Pallardy Stephen G. , Garrett Harold E.
Published: March 2009

A staining procedure was developed to facilitate assessment of ectomycorrhizal infection on oak roots. Roots of northern red oak (Quercus rubra L.) seedlings previously inoculated with Pisolithus tinctorius (Pers.) Coker & Couch were stained with 0.1% Ponceau S (acid red 112) in 10% acetic acid. Mycorrhizal short roots were stained bright red by this procedure while nonmycorrhizal areas of the root remained unstained. To confirm the accuracy of the method, mycorrhizal and nonmycorrhizal oak root samples (as indicated by Ponceau S staining) were cleared and stained with trypan blue in lactophenol, a widely used procedure for confirming the presence of fungi on roots. For over 3000 short root samples, the two methods gave nearly identical results, with an error of only about 1%. The new method offers potential advantages for rapid assessment of mycorrhizal infection for several species of plants and fungi.
The effect of smelting operations on peatlands near Sudbury, Ontario, Canada
Authors: Gignac L. Dennis , Beckett Peter J.
Published: March 2009

Accumulations of six metals (Cu, Ni, Mn, Al, Fe, and Ca) were analysed in peat and water for 18 peatlands east northeast of Falconbridge, Ontario, Canada. The peatlands had a minimum of 30 cm accumulation of peat, < 10 μg mL−1 Ca2+ in the water, and were from a variety of physiognomic dominance types. Significant correlations existed between the distance from smelting operations and the concentrations of Cu and Ni in the peat and water. Levels of Mn, Fe, and Ca were not related to distance. The vegetation was analysed on 11 of the 18 peatlands. With the exception of the two sites closest to the smelter, all are low shrub peatlands, dominated by Chamaedaphne calyculata. Effects on the vegetation range from severe within 2 km of the smelter to minimal at 30 km. Sphagnum species that normally dominate the moss layer of these peatlands begin to appear at approximately 12 km from the smelter and are found almost exclusively in the moat area. With increasing distance and decreasing concentrations of Cu and Ni, conditions gradually permit growth of the oligotrophic Sphagnum species. Beyond 30 km, Sphagnum dominates all portions of the peatlands.
Spore wall development in the liverwort, Haplomitrium hookeri
Authors: Brown Roy Curtiss , Lemmon Betty E.
Published: March 2009

Spore wall development in Haplomitrium hookeri (Calobryales) is initiated while the sporocyte is in meiotic prophase. Extracellular exine precursor material is preferentially deposited within the sporocyte wall in a highly specific pattern that is predictive of the pilate – retiplilate ornamentation of the mature exine. Tripartite structures characteristic of hepatic exine are polymerized in exine precursors that become elevated on stalks of projecting cytoplasm. Plasma membranes of the cytoplasmic projections become extremely contorted and membrane displacement eventually isolates stalks from cytoplasm. An inner multilaminar layer is formed by apposition of tripartite lamellae. By the late tetrad stage the distinctive wall layers of the mature spore are present; capitula of heavily coated lamellae that cap projections of the continuous foveolate layer, a multilaminar inner exine layer of approximately 20 alternating light and dark bands, and a fibrillar intine. All but the intine become acetolysis resistant indicating the presence of sporopollenin. During maturation the sporopollenin framework of the capitula and foveolate layer become obscured by the addition of electron-dense, non-acetolysis-resistant materials. Based on spore wall micromorphology, Haplomitrium hookeri appears most closely allied to certain of the Metzgeriales, e.g., Pallavicinia.
Variation in wild rice (Zizania palustris) stands across northern Saskatchewan
Authors: Archibold O. W. , Weichel B. J.
Published: March 2009

Variations in wild rice (Zizania palustris L.) morphology and stand productivity have been evaluated for 20 sites across northern Saskatchewan. Although considerable within-stand variation occurred, significant between-site differences were also detected, and regional trends were clearly evident. Plant development was more rapid in the eastern part of the province, and harvest began about 1 week earlier here. However, in the west, individual plants were typically more robust, tillering was more common, and the number of florets borne on the panicle was generally larger. Consequently, potential seed production from an individual plant was highest in these western districts, although differences in stem density and seed weight at the various sites offset individual plant performance to some extent. Differences in water temperature and water depth occurred across the province in July, while in August, water depth, pH, and conductivity were significantly correlated with longitude. Water depth and pH were most strongly related to plant performance, shallower water and higher pH being characteristic of the western sites.
New keratinophilic species of Chrysosporium
Authors: Sigler Lynne , Guarro J. , Punsola L.
Published: March 2009

Two new keratinophilic species, Chrysosporium europae and C.mephiticum, are described and illustrated. The differences between these and other similar species are discussed.
Thirty-five years of secondary succession in a Festuca viridula – Lupinus latifolius dominated meadow at Sunrise, Mount Rainier National Park, Washington
Authors: Frank Douglas A. , Moral Roger del
Published: March 2009

Colonization patterns were investigated in a Festuca viridula – Lupinus latifolius dominated meadow at Sunrise, Mount Rainier National Park. Floristic records of a site profoundly disturbed in 1946 were examined from permanent plots in 1960, 1970, and 1981. Aster alpigenus, Carex spectabilis, Juncus drummondii, and Potentilla flabellifolia, four species relatively uncommon in the surrounding undisturbed meadow, have dominated the disturbed area since 1960. All of these species produce many dispersible seeds. Conversely, Festuca viridula and Lupinus latifolius, dominants in the surrounding meadow, are uncommon in the disturbed area. Poorly dispersed seeds of L. latifolius and extremely low viable seed production and poor seedling survival of Festuca viridula appear to be reasons for their poor colonizing abilities. Average percent similarity of the permanent plots has increased since 1960, indicating a small tendency towards greater homogeneity in the disturbed area. This is illustrated by a detrended correspondence analysis of the permanent-plot data. However, the disturbed area remains distinct after over 35 years of undisturbed existence. The development of a Festuca–Lupinus dominated community in the disturbed area may eventually occur, but the alternative outcome, a permanently deflected succession producing a community dominated by successful colonists, appears more likely.
The use of fluorescent dyes in the microinjection of alfalfa protoplasts
Authors: Reich Terry J. , Iyer V. N. , Haffner Margaret , Holbrook Larry A. , Miki Brian L.
Published: March 2009

A major obstacle in the development of microinjection technology for plant protoplasts has been the poor resolution of the intracellular compartments by conventional light microscopy. This was overcome through the use of fluorescent stains. The nuclei of living alfalfa (Medicago sativa) protoplasts were stained specifically with both Hoechst 33258 and 4′,6-diamidino-2-phenylindole. Mitochondria were stained specifically with 3,3′-diethyloxadicarbocyanine iodide and rhodamine 123. Cytoplasm was stained selectively with fluorescein diacetate. Under the specific conditions employed, the stains did not retard or suppress DNA synthesis, mitosis, cell division, or microcolony formation. Intranuclear microinjection did not significantly inhibit cell division in protoplasts stained with Hoechst 33258. Furthermore, the pattern of protein synthesis remained constant during the early stages of protoplast culture and was not perturbed by staining. These combined results demonstrated the suitability of alfalfa protoplasts stained with fluorescent dyes as hosts for microinjection.
LOAD DISTRIBUTION IN CONGESTED SCALE-FREE NETWORKS
Authors: ZHENG JIAN-FENG , GAO ZI-YOU , FU BAI-BAI
Published: March 2009

In this work, we study the effects of scale-free topology and congestion on load distribution. Congestion effect can be described by link cost functions, which map link flows into travel times. Two different kinds of link's practical capacity (it is similar to link's capacity for transport) which is a parameter in link cost functions, i.e., uniform case and nonuniform case, are investigated. After introducing the effect of congestion, load distribution is typically discussed in Barábasi–Albert and Goh scale-free networks. In the uniform case, for Barábasi–Albert scale-free networks, we recover a power-law behavior for load distribution with a larger exponent, as compared with the distribution of betweenness centrality; for Goh scale-free networks, we also recover a power-law behavior and its exponent approaches to the exponent of degree distribution. While in the nonuniform case, the power-law behavior for load distribution may not always be conserved in both Barábasi–Albert and Goh scale-free networks. That is to say, different kinds of load distributions are obtained under different conditions. It may shed some light to study traffic dynamics on scale-free networks.
ANTI-RED BOND CALCULATION ALGORITHM IN PERCOLATION
Authors: SCHOLDER OLIVIER
Published: March 2009

This paper presents an algorithm, which computes the number of anti-red bonds in a simple cubic lattice (site percolation) for different sizes and densities. Our interest was the fractal dimension of anti-red bonds at the percolation threshold. The value is found to be 1.18 ± 0.01. Two different theories proposed by Conigilio resp. Gouyet suggested a fractal dimension of 1.25 resp. 0.9. Thus, we can exclude the theory of Gouyet and are consistent with the one by Coniglio.
IMPROVED COLLABORATIVE FILTERING ALGORITHM VIA INFORMATION TRANSFORMATION
Authors: LIU JIAN-GUO , WANG BING-HONG , GUO QIANG
Published: March 2009

In this paper, we propose a spreading activation approach for collaborative filtering (SA-CF). By using the opinion spreading process, the similarity between any users can be obtained. The algorithm has remarkably higher accuracy than the standard collaborative filtering using the Pearson correlation. Furthermore, we introduce a free parameter β to regulate the contributions of objects to user–user correlations. The numerical results indicate that decreasing the influence of popular objects can further improve the algorithmic accuracy and personality. We argue that a better algorithm should simultaneously require less computation and generate higher accuracy. Accordingly, we further propose an algorithm involving only the top-N similar neighbors for each target user, which has both less computational complexity and higher algorithmic accuracy.
CASIMIR PISTONS FOR MASSIVE SCALAR FIELDS
Authors: ZHAI XIANG-HUA , ZHANG YAN-YAN , LI XIN-ZHOU
Published: March 2009

The Casimir force on two-dimensional pistons for massive scalar fields with both Dirichlet and hybrid boundary conditions is computed. The physical result is obtained by making use of generalized ζ-function regularization technique. The influence of the mass and the position of the piston in the force is studied graphically. The Casimir force for massive scalar field is compared to that for massless scalar field.
A trial of the objective structured practical examination in physiology at Melaka Manipal Medical College, India
Authors: Abraham Reem Rachel , Raghavendra Rao , Surekha Kamath , Asha Kamath
Published: March 2009

A single examination does not fulfill all the functions of assessment. The present study was undertaken to determine the reliability and student satisfaction regarding the objective structured practical examination (OSPE) as a method of assessment of laboratory exercises in physiology before implementing it in the forthcoming university examination. The present study was undertaken in the Department of Physiology of Melaka Manipal Medical College, Manipal Campus, India. During the OSPE, students were made to rotate through 11 stations, of which 8 stations were composed of questions that tested their knowledge and critical thinking and 2 stations were composed of skills that students had to perform before the examiner. One station was kept as the rest station. Performance of the students was assessed by comparing the students' scores in the traditional practical examination (TPE) and OSPE using “Bland-Altman technique.” Student perspectives regarding the OSPE were obtained by asking them to respond to a questionnaire. The Bland-Altman plot showed that ∼63% of the students showed a performance in the scores obtained using the OSPE and TPE within the acceptable limit of 8; 32% of the students scored much above the anticipated difference in the scores, and the rest scored below the anticipated difference in the scores on the OSPE and TPE. Feedback indicated that students were in favor of the OSPE compared with the TPE. Feedback from the students provided scope for improvement before the OSPE was administered for the first time in the forthcoming university examination.
Teaching neurophysiology, neuropharmacology, and experimental design using animal models of psychiatric and neurological disorders
Authors: Morsink Maarten C. , Dukers Danny F.
Published: March 2009

Animal models have been widely used for studying the physiology and pharmacology of psychiatric and neurological diseases. The concepts of face, construct, and predictive validity are used as indicators to estimate the extent to which the animal model mimics the disease. Currently, we used these three concepts to design a theoretical assignment to integrate the teaching of neurophysiology, neuropharmacology, and experimental design. For this purpose, seven case studies were developed in which animal models for several psychiatric and neurological diseases were descibed and in which neuroactive drugs used to treat or study these diseases were introduced. Groups of undergraduate students were assigned to one of these case studies and asked to give a classroom presentation in which 1) the disease and underlying pathophysiology are described, 2) face and construct validity of the animal model are discussed, and 3) a pharmacological experiment with the associated neuroactive drug to assess predictive validity is presented. After evaluation of the presentations, we found that the students had gained considerable insight into disease phenomenology, its underlying neurophysiology, and the mechanism of action of the neuroactive drug. Moreover, the assignment was very useful in the teaching of experimental design, allowing an indepth discussion of experimental control groups and the prediction of outcomes in these groups if the animal model were to display predictive validity. Finally, the highly positive responses in the student evaluation forms indicated that the assignment was of great interest to the students. Hence, the currently developed case studies constitute a very useful tool for teaching neurophysiology, neuropharmacology, and experimental design.