bluuebunny/crossref_metadata_2025 huggingface dataset:
2D-Flow Calculation Around Floating Bodies Using a Finite Element Method
Authors: Barros Astrid M. , Sphaier Sergio H.
Published: March 2009

This paper presents a numerical procedure to study the full nonlinear hydrodynamic problem of a moving body in a viscous flow in the presence of a free surface. The Navier-Stokes equations are solved numerically with the Finite Element Method using Chorin’s Projection. Moving boundaries are modelled in an Arbitrary Lagrangean-Eulerian Formulation and an adaptive mesh is used. The use of different approaches to account for the boundary condition for the hull and it’s interaction with the free surface is discussed. Three different hydrodynamic problems are solved and their results are compared with published numerical and experimental ones: 1 - the sloshing of a fluid in a angular basin; 2 - a circular cylinder oscillating horizontally close to the free surface; 3 - an oscillating rectangular floating cylinder.
Analytical Models for the Probability Distributions of Fatigue Parameters and Crack Size of Offshore Structures Based on Bayesian Updating
Authors: Heredia-Zavoni Ernesto , Montes-Iturrizaga Roberto
Published: March 2009

In this paper a bayesian framework is used for updating the probability distributions of the parameters of a fatigue model and of crack size in tubular joints using information from inspection reports of fixed offshore structures. For crack detection, the uncertainties are taken into account by means of probability-of-detection (POD) curves. According to the bayesian procedure, if during an inspection no crack is detected, the updated (posterior) distributions depend on the prior ones at time of such inspection and on the POD. On the other hand, if during an inspection a crack is detected and measured, the corresponding predicted crack depth at that time is estimated given values of parameters of a selected fatigue model and of the initial crack depth. Then, a sample value of the model and sizing error associated with the inspection performed, defined as the logarithmic difference between the measured and the predicted crack size, is calculated. Such error is considered to be a normally distributed random variable with known mean and uncertain variance. The distribution of the error variance is taken as a conjugate one for samples of normally distributed variables with known mean and uncertain variance. Based on these assumptions, an analytical expression is obtained for the updated (posterior) distributions of the parameters of the fatigue model and of crack size. It is shown that the updated distributions depend on POD and on the prior and updated parameters of the error variance distribution. Finally, the bayesian method proposed here is illustrated taking as a fatigue model the Paris-Erdogan relation, which estimates crack growth based on linear elastic fracture mechanics. Joint failure is considered to occur when the crack depth reaches the thickness of the element where the crack propagates. The evolution of reliability with time is assessed.
Reliability Based Fatigue Safety Assessment of Offshore Structures in Ice Zone
Authors: Chen Guoming , Yang Xiaocheng
Published: March 2009

The paper presents a probabilistic fatigue safety assessment procedure for offshore structures in ice zone, including establishing fatigue reliability model, determining fatigue loading probabilistic parameters, modeling fatigue resistance parameters and digital assessment on fatigue reliability. A new fatigue model based on random fatigue crack growth experiment is proposed to deal with loading interaction under stochastic ice force. There exists great probabilistic scatter in describing the fatigue loading and stress of structural member under ice loading. The paper investigates the statistical properties of annual ice term and ice strength. The normal distribution is used to describe the statistical model of ice term. The fatigue resistance parameters are discussed by presenting the experiment results of crack propagation under random ice loading history. Two digital evaluation approaches, i.e. distribution fitness method and life distribution method, are introduced to determine fatigue reliability of offshore structures under ice loading. Several engineering application examples are given.
Detection of Extreme Waves in SAR Images and Radar-Image Sequences
Authors: Dankert Heiko , Horstmann Jochen , Rosenthal Wolfgang
Published: March 2009

Extreme waves are often enclosed by other waves which are also higher than the average. These wave groups have to be taken into account for instance for the design of offshore platforms, breakwaters or ships, because successive high waves can cause more damage on those structures than the same waves separated by smaller waves. Further they can excite the resonance frequencies of moored structures like platforms due to non-linear effects or cause capsize. They are therefore of interest for engineers and scientists (e.g. Goda 1983). A method is presented to localize wave groups spatial and spatio-temporal utilizing synthetic aperture radar (SAR) images and nautical radar-image sequences. The approach to detect wave groups is based on the detection of the wave envelope. It is assumed that the sea surface elevation can be treated as a Gaussian process. The method is applied to SAR images acquired by the European satellite ERS-1 and to radar-image sequences recorded by tower-based nautical radars. In contrast to 1D sensors like buoys the SAR records an image and gives therefore a 2D description of the sea surface by measuring the radar backscatter from the sea surface. The measurements taken by a nautical radar provide the possibility to record time series of images and therefore to get a 3D description of the sea surface. Radar-image sequences are acquired by recording the spatial and temporal evolution of the sea surface backscatter, which is modulated through the surface wave field. Nautical radar-image sequences allow to detect wave groups within a time span that makes it possible to start safety programs before the group reaches a platform. The existing data sets are exploited with respect to the recognition of extreme wave events.
Heat Transfer During Gas/Condensate Flow Shut Down/Cool Down in Deepwater Lazy Wave Risers
Authors: Chin Y. Doreen , Roberts I. , Krishnathasan K.
Published: March 2009

The mechanisms of phase re-distribution and of gas/condensate flow in a deepwater lazy-wave riser after system shutdown are studied numerically and theoretically. This is the second of three papers in series. The investigated system consists of a 15-mile long subsea pipeline tieback to a floating structure, via a 9,800-ft long lazy-wave production riser. The subsea well is located at 6,350 ft of water in the Gulf of Mexico. The system transports a gas-condensate mixture with gas-oil ratio of 1000 scf/stb. This study revealed that besides pressure, the external and internal heat transfer during system cool-down are main factors for the phase re-distribution between gas and liquid and along the system. The liquid holdup variations are caused by the interfacial mass transfer between gas-liquid interface and phase re-allocation due to the combined effects of gravitational and buoyancy forces. The phenomena are discussed based on fundamental heat transfer and multiphase flow principles. Gas/condensate flow is a multiphase flow phenomenon commonly encountered in raw gas transportation. The results of this study will improve the fundamental understanding of multiphase flow transient behavior in deepwater pipeline/riser systems, and provide beneficial information for production system design.
Structural Optimization on Topside Supports for Ship-Shaped Hulls
Authors: Machado Christiane Lopes , Santos Marco Antonio
Published: March 2009

PROJEMAR S. A., a naval and offshore design company at Brasil has developed several conversion projects of FPSO’s to operate at Campos Basin. This way, PROJEMAR faced some interface difficulty in the structural design of the topside supports, mainly for the vessel reinforcement. The structural analysis of the cargo region, when performed together with the topside supports and loads, introduces significant buckling and fatigue problems in the main transverse and longitudinal structure of the vessel. The solution adopted in first instance is to reinforce the transverse structure and longitudinal bulkheads of the cargo tanks just below the topside supports. This reinforcement is expensive and takes a lot of time to be done, as hundreds of buckling bars should be installed. In order to avoid this work inside the cargo region, PROJEMAR evaluated this study to minimize the steelwork inside the cargo region, and to optimize the steel weight for topside supports. PROJEMAR analyzed three different concepts of topside supports: two transverse bulkheads supporting each topside module, two sets of strong brackets supporting each topside module, and sets of pillars supporting each topside modules. The results present the amount of steelwork inside and outside the cargo tanks, the total amount of steel reinforcement after the evaluation of stress, deflection, buckling and fatigue verification. The conclusions present cost and benefit for each solution, and some discussions on the time acceleration for the conversion.
Polyester Mooring for Ultra-Deepwater Applications
Authors: Bhat Shankar S. , Cermelli Christian A. , Lo King Him
Published: March 2009

In the past few years, drilling for oil and gas has been conducted in increasingly greater water depth, with recent records approaching 10,000.0 ft water depth. Ultra-deepwater drilling demands increased performance from mooring systems, such as tight watch circle, enhanced reliability, and ease of deployment. Synthetic fiber mooring lines are essential components to help meet these demands. Because of the lack of industry experience with this new material, advanced studies are required to properly design and optimize polyester-based mooring systems for ultra-deepwater drilling. This paper provides information on the performance of polyester mooring lines, based on coupled and un-coupled analyses and compares various design methodologies.
A 2D Computational Fluid Dynamics Analysis of Wells Turbine Blade Profiles in Isolated and Cascade Flow
Authors: Daly John , Frawley Patrick , Thakker Ajit
Published: March 2009

This paper deals with the application of Computational Fluid Dynamics (CFD) to the analysis of the aerodynamic characteristics of symmetrical airfoil blades in 2-Dimensional flow. The CFD model was used to compare blades of varying profiles to analyse the aerodynamic forces and the compressibility effects and to compare the differences in modelling the blades in isolated and cascade flow. The model was validated using correction factors with published results for the NACA 0015 blade profile, which show that the model gives good results for the aerodynamic forces. The differences in the predicted aerodynamic characteristics, such as low angle of incidence drag, as well as normal and tangential forces are compared for the isolated and cascade cases. The validated model was then used to compare proposed blade profiles for a Wells Turbine. The paper presents the results of the numerical investigation along with the analysis and comparison of the different profiles.
A Methodology for the Selection of an Alternative for a Floating Production System
Authors: Morooka C. K. , Castro G. T.
Published: March 2009

For the selection of a field production system in order to decide among several alternatives, in general, an oil company bases itself mainly on economical analysis aspects, such as net present value and internal rate of return. However, the evaluation of a field development project, generally speaking, needs a methodology for the selection of the best alternative that complies proportionally with all the objectives of the company. Which means that several other aspects besides the financial one should be taken into account in the selection decision process. The main purposes of the present work is to present the methodology for decision-making that supports selection of the best floating production system, for a given offshore oilfield. As an example, a typical field development project is evaluated based on this method. The present paper shows the importance to include technological, safety and environmental risk besides the usual financial one, used for selecting the best alternative of a floating production system in offshore field development.
Mooring System Design and Optimization for Floating Bridge of Urmia Lake
Authors: Daghigh M. , Paein Koulaei R. T. , Seif M. S.
Published: March 2009

In order to get better understanding on the response of floating bodies, different design aspects of mooring lines has been investigated in this paper. Mooring lines are categerized into two types; the catenary settling on the sea floor (type 1) and the limited one which has no dead-length on sea floor (type 2). It has been observed that the stiffness of both types may be well predicted by Jain’s formulation and in the design process of floating bodies the mooring lines may be replaced by uncoupled horizontal and vertical springs. On the other hand, the anchor capacity against sliding and release from the mean still water has been studied in this paper. From the results of a parametric study, using the discrete element method, the block anchor the dimensions for the Urmia floating bridge has been optimized and the behavior of anchor and seabed deposits for release of block anchor indicates that the burial depth and the stress level on the block anchor itself and the sea bed are in the allowable and elastic region, respectively.
Experiences With VIV Analyses of SCR’s Using Complex Modes
Authors: Moe Geir , Amitsen O̸vind A.
Published: March 2009

The theory behind a computer programme for prediction of Vortex Induced Vibrations (VIV) of risers is summarised, and some experiences with its use are given. The programme in question is named VICoMo (VIV by Complex Modes) and is based on modal analysis by means of complex modes. The approach is iterative in nature because the added mass and damping forces depend nonlinearly on motion amplitude and frequency. Experiences with some runs to model a prototype Steel Caternary Riser (SCR) are summarised. A key element herein is the strategy for the choice of the parameters governing the iterations.
Long Cruising Trial of AUV “URASHIMA”
Authors: Nakajo Hidehiko , Aoki Taro , Murashima Takashi , Tsukioka Satoshi , Hyakudome Tadahiro , Ida Tadahiko , Kabeno Tatsumasa
Published: March 2009

A Deep Sea Cruising AUV “URASHIMA” has been developed by JAMSTEC since 1998. The dimensions and weight are 10m (L), 1.3m (W), 1.5m (H), and about 7.5 tons in air. A main power source device system of AUV “URASHIMA” is a large capacity of lithium-ion (Li-ion) rechargeable battery system or Solid Polymer Electrolyte Fuel Cell (PEFC) system. AUV “URASHIMA” will be able to cruise for about 100km with Li-ion battery system and it will cruise for about 300km with fuel cell system. The cruising trial used by the fuel cell system will start at the end of 2002. The instruments for science researches are an automatic multi-water-sampling system, a CTDO, a side-scan sonar, a digital still camera with a thermoelectrically cooled CCD image sensor, a TV camera, and so on. Three operation modes, which are UROV mode, acoustic remote control mode and autonomous mode, are available. Those three kinds of modes are used acceding to each development stage and ocean researches. UROV mode is to monitor the state of the vehicle with fiber optics. At the first development stage of AUV “URASHIMA”, we carried out long cruising trial for about 100km and maximum operational depth trial at 3,500m used by Li-ion rechargeable battery system. URASHIMA was succeeded to reach at 3,518m depth of the seafloor at the sea trial of August 2001. We also carried out long cruising trial that was controlled by autonomous mode. Then, URASHIMA was cruised 70km distance at the sea trial of December 2001. We will have a next sea trail on May 2002 for 100km long cruising test. At the next development stage, we will carried out long cruising trial for 300km used by the fuel cell system.
Added Mass of Elastically Mounted Rigid Cylinder in Water Subjected to Vortex-Induced Vibrations
Authors: Fujarra Andre´ L. C. , Pesce Celso P.
Published: March 2009

Vortex Induced Vibrations (VIV) of elastically mounted rigid cylinders, with low mass-damping parameter values, are strongly dependent on the added mass coefficient. This paper aims to contribute to the technical literature by presenting some results from experiments carried out at University of Sa˜o Paulo – USP and at the Sa˜o Paulo State Technological Research Institute – IPT. A cantilevered rigid cylinder was mounted on an elastic (leaf spring) two-degree-of-freedom device. The device is not only an elastic support, but acts also as a special mechanical transducer to measure accelerations/forces/displacements in the stream-wise (x) and the cross-wise (y) directions. A comprehensive experimental calibration of such a device was carried out, both “in air” and “in water”. The added mass coefficient in the cross-wise direction was indirectly determined from forces and acceleration measurements as a function of the reduced velocity. Results from time-domain and frequency-domain analyses are compared with those obtained by Vikestad et al. (2000) [1].
Floating Thin Sheet in Waves: Drift Force, Drift Velocity and Wave Damping
Authors: Lee Choung Mook , Kang Kwan Hyoung
Published: March 2009

Wave driven force on a deformable but inextensible thin sheet is investigated analytically by taking into account the boundary layer beneath the sheet. Wave tank experiments are carried out to verify the theoretical predictions. Theoretical prediction of the drift force, drift velocity, and wave attenuation by the sheet are made. It is found that the drift velocity of a contaminated free surface is much greater than that of a clean free surface, and increase in the drift velocity is greater for the greater shear stress on the interface of the viscous surface layer and the water below. The theoretical and experimental results are found in good agreement.
Spectral Analysis of Ship-Generated Waves in Finite-Depth Water
Authors: Scragg Carl A.
Published: March 2009

Recent efforts to compare the waves generated by different vessels traveling in finite-depth water have struggled with difficulties presented by various data sets of wave elevations (either measurements or predictions) corresponding to different lateral distances from the ship. Some of the attempts to shift the data to a common reference location have relied upon crude and potentially misleading approximations. The use of free-wave spectral-methods not only overcomes such difficulties, but it also provides us the means to accurately extend CFD results into the far field. As in the deep-water case, one can define a free-wave spectrum that is valid for all lateral positions and distances astern of the vessel. The free-wave spectrum contains a complete description of the Kelvin wake, and wave elevations at any far-field position can be readily calculated once the spectrum is known. For the case of infinitely deep water, Eggers, Sharma, and Ward [1967] presented a method by which free-wave spectra can be determined from appropriate measurements of the far-field wave elevations. The current paper discusses the use of free-wave spectra for finite-depth problems and presents a method for the determination of free-wave spectra based upon fitting predicted wave elevations to a corresponding data set. The predicted wave elevations can be calculated from an unknown distribution of finite-depth Havelock singularities. The unknown singularities are determined by minimizing the mean-square-difference between predicted and measured wave fields. The method appears to be quite general and can be used to calculate either finite or infinite-depth free-wave spectra from experimental data or from local CFD predictions.
A 40 Year Hindcast of Wind, Sea Level and Waves in European Waters
Authors: Soares Carlos Guedes , Weisse Ralf , Carretero Juan Carlos , Alvarez Enrique
Published: March 2009

The paper describes the initial efforts in a project whose objective is to obtain a 40-year hindcast of wind, sea level and wave climatology for European waters. The 40-year global atmospheric re-analysis carried out by the National Centre for Environmental Prediction, Washington, USA (NCEP) and the National Centre for Atmospheric Research, Boulder, Colorado, USA (NCAR) will be used as forcing of limited area atmospheric models. The fine grid atmospheric fields will be used to force state-of-the-art wave models (WAM) and sea level models (HAMSOM and TELEMAC) in regional areas around Europe so as to produce climatic information on waves, sea levels, and currents in a very large extend of the European waters, including the Mediterranean, North East Atlantic and North Sea. The available satellite data, including wind, wave and sea-level data, will be collected and will be used to be compared with the hindcast results, so as to yield uncertainty measures related to the data. Statistical analysis of the produced atmospheric, sea level and wave hindcast and remote sensed data will be performed in order to provide information about the climatological trends in the European Waters and Coastal Seas.
Interactions Between Thrusters Attached to a Vessel Hull
Authors: Elkstrom L. , Brown D. T.
Published: March 2009

Many offshore vessels are equipped with rotating (azimuthing) thrusters for ease of manoeuvring and dynamic positioning. Accurate prediction of available thrust to resist horizontal environmental forces is important allowing the station-keeping capability of these vessels to be established. Additionally such thrusters are in many cases used, possibly in conjunction with tunnel thrusters and main propeller to provide propulsive power in transit. This paper presents results from a comprehensive experimental study to establish the influence on thruster performance of variations in current inflow velocity, thruster power, and thruster position relative to the hull. Furthermore the influence of two thrusters in close proximity, azimuthing so that flow into one thruster is influenced by the flow through the second thruster, is addressed. The experimental work was carried out using the wave tank and combined motion carriage facility in the Department of Mechanical Engineering at University College London.
A Preliminary Evaluation of a Multiple-Generator Drivetrain Configuration for Wind Turbines
Authors: Cotrell Jason R.
Published: March 2009

The recent trend toward large wind turbines has led to very expensive gearboxes that hinder their feasibility. The gearboxes for these wind turbines are more expensive per kilowatt (kW) of rated power than for smaller turbines because the torque increases more quickly than the power when increasing the rotor diameter. Multiple-generator drivetrain configurations can reduce the drivetrain cost for large wind turbines while increasing the energy capture and reliability. The National Renewable Energy Laboratory (NREL) is reexamining the benefits of multiple-generator configurations through the Wind Partnership for Advanced Component Technology (WindPACT) program. This paper qualitatively compares a multiple-generator drivetrain configuration to a conventional drivetrain.
Predicting temporary threshold shifts in a bottlenose dolphin (Tursiops truncatus): The effects of noise level and duration
Authors: Mooney T. Aran , Nachtigall Paul E. , Breese Marlee , Vlachos Stephanie , Au Whitlow W. L.
Published: March 2009

Noise levels in the ocean are increasing and are expected to affect marine mammals. To examine the auditory effects of noise on odontocetes, a bottlenose dolphin (Tursiops truncatus) was exposed to octave-band noise (4–8kHz) of varying durations (<2–30min) and sound pressures (130–178dB re 1μPa). Temporary threshold shift (TTS) occurrence was quantified in an effort to (i) determine the sound exposure levels (SELs) (dB re 1μPa2s) that induce TTS and (ii) develop a model to predict TTS onset. Hearing thresholds were measured using auditory evoked potentials. If SEL was kept constant, significant shifts were induced by longer duration exposures but not for shorter exposures. Higher SELs were required to induce shifts in shorter duration exposures. The results did not support an equal-energy model to predict TTS onset. Rather, a logarithmic algorithm, which increased in sound energy as exposure duration decreased, was a better predictor of TTS. Recovery to baseline hearing thresholds was also logarithmic (approximately −1.8dB/doubling of time) but indicated variability including faster recovery rates after greater shifts and longer recoveries necessary after longer duration exposures. The data reflected the complexity of TTS in mammals that should be taken into account when predicting odontocete TTS.
Nonlinear frequency shifts in acoustical resonators with varying cross sections
Authors: Hamilton Mark F. , Ilinskii Yurii A. , Zabolotskaya Evgenia A.
Published: March 2009

The frequency response and nonlinear resonance frequency shift of an acoustical resonator with losses and having a varying cross section were investigated previously using Lagrangian mechanics and perturbation for resonator shapes that are close to cylindrical [M. F. Hamilton, et al., J. Acoust. Soc. Am. 110, 109–119 (2001)]. The same approach is extended here to include resonators having any shape for which the Webster horn equation is a valid model in the linear approximation. Admissible shapes include cones and bulbs proposed for acoustical compressors. The approach is appropriate for approximate but rapid parameter estimations for resonators with complicated shapes, requiring far less computation time than for direct numerical solution of the one-dimensional model equation frequently used for such resonators [Ilinskii et al., J. Acoust. Soc. Am. 104, 2664–2674 (1998)]. Results for cone and bulb shaped resonators with losses are compared with results from the direct numerical solution. The direction of the resonance frequency shift is determined by the efficiency of second-harmonic generation in modes having natural frequencies below versus above the frequency of the second harmonic, and how the net effect of this coupling compares with the frequency shifts due to cubic nonlinearity and static deformation.
Entropy in statistical energy analysis
Authors: Le Bot Alain
Published: March 2009

In this paper, the second principle of thermodynamics is discussed in the framework of statistical energy analysis (SEA). It is shown that the “vibrational entropy” and the “vibrational temperature” of sub-systems only depend on the vibrational energy and the number of resonant modes. A SEA system can be described as a thermodynamic system slightly out of equilibrium. In steady-state condition, the entropy exchanged with exterior by sources and dissipation exactly balances the production of entropy by irreversible processes at interface between SEA sub-systems.
Acoustic field in a quasi-spherical resonator: Unified perturbation model
Authors: Guianvarc’h Cécile , Pitre Laurent , Bruneau Michel , Bruneau Anne-Marie
Published: March 2009

Gas-filled quasi-spherical resonators are excellent tools for the measurement of thermophysical properties of gas and have also been retained for the determination of the Boltzmann constant with a low uncertainty, which can be derived from measurements of both the speed of sound in a noble gas and the volume of the resonator. To achieve this, a detailed modeling of the acoustic field in quasi-spherical resonators is of importance. Several phenomena and perturbations must be taken into account, including, among inertia and compressibility, heat conduction, viscosity, the shape of the resonator, small irregularities on the wall, and so on. The aim of this paper is to provide improvements to the current models of the acoustic field in such resonator. Namely, the model given here takes into account all the different perturbing elements together in a unique formalism, including the coupling between the different perturbing elements and the resulting modal coupling in a consistent manner. The first results obtained from this analytical model on a simple configuration show that the effect of modal coupling is small but should not be neglected regarding the accuracy required here, even if several improvements could still be provided to this new unified model.
Model of coupled pulsation and translation of a gas bubble and rigid particle
Authors: Hay Todd A. , Hamilton Mark F. , Ilinskii Yurii A. , Zabolotskaya Evgenia A.
Published: March 2009

A model of the interaction of a spherical gas bubble and a rigid spherical particle is derived as a coupled system of second-order differential equations using Lagrangian mechanics. The model accounts for pulsation and translation of the bubble as well as translation of the particle in an infinite, incompressible liquid. The model derived here is accurate to order R5∕d5, where R is a characteristic radius and d is the separation distance between the bubble and particle. This order is the minimum accuracy required to account for the interaction of the bubble and particle. Dependence on the size and density of the particle is demonstrated through numerical integration of the dynamical equations for both the free and forced response of the system. Numerical results are presented for models accurate to orders higher than R5∕d5 to demonstrate the consequences of truncating the equations at order R5∕d5.
Temporal integration in vowel perception
Authors: Wallace Andrew B. , Blumstein Sheila E.
Published: March 2009

Psychoacoustic research suggests that multiple auditory channels process incoming sounds over temporal windows of different durations, resulting in multiple auditory representations being available to higher-level processes. The current experiments investigate the size of the temporal window used in vowel quality perception using an acoustic priming paradigm with nonspeech and speech primes of varying duration. In experiment 1, identification of vowel targets was facilitated by acoustically matched nonspeech primes. The magnitude of this effect was greatest for the shortest (25 and 50ms) primes, remained level at medium (100 and 150ms) duration primes, and declined significantly at longer prime durations, suggesting that the auditory stages of vowel quality perception integrate sensory input over a relatively short temporal window. In experiment 2, the same vowel targets were primed by speech stimuli, consisting of vowels using the same duration values as those in experiment 1. A different pattern of results emerged with the greatest priming effects found for primes of around 150ms and less priming at the shorter and longer durations, indicating that longer-scale temporal processes operate at higher levels of analysis.
Competitive Electrochemiluminescence Wash and No-Wash Immunoassays for Detection of Serum Antibodies to Smooth
Brucella
Strains
Authors: Thompson Iain , McGiven John , Sawyer Jason , Thirlwall Rachel , Commander Nicola , Stack Judy
Published: March 2009

Brucellosis is a bacterial zoonotic disease of major global importance. Natural hosts for
Brucella
species include animals of economic significance, such as cattle and small ruminants. Controlling brucellosis in natural hosts by high-throughput serological testing followed by the slaughter of seropositive animals helps to prevent disease transmission. This study aimed to convert an existing competitive enzyme-linked immunosorbent assay (cELISA), used for the serodiagnosis of brucellosis in ruminants, to two electrochemiluminescence (ECL) immunoassays on the Meso Scale Discovery (MSD) platform. The first assay employed a conventional plate washing step as part of the protocol. The second was a no-wash assay, made possible by the proximity-based nature of ECL signal generation by the MSD platform. Both ECL wash and no-wash assays closely matched the parent cELISA for diagnostic sensitivity and specificity. The results also demonstrated that both ECL assays met World Organization for Animal Health (OIE) standards, as defined by results for the OIE standard serum (OIEELISA
SP
SS). This report is the first to describe an ECL assay incorporating lipopolysaccharide, an ECL assay for serodiagnosis of a bacterial infectious disease, a separation-free (no-wash) ECL assay for the detection of serum antibodies, and the use of the MSD platform for serodiagnosis. The simple conversion of the cELISA to the MSD platform suggests that many other serodiagnostic tests could readily be converted. Furthermore, the alignment of these results with the multiplex capability of the MSD platform offers the potential of no-wash multiplex assays to screen for several diseases.
Immunogenicity of a Whole-Cell Pertussis Vaccine with Low Lipopolysaccharide Content in Infants
Authors: Zorzeto Tatiane Queiroz , Higashi Hisako Gondo , da Silva Marcos Tadeu Nolasco , Carniel Emilia de Faria , Dias Waldely Oliveira , Ramalho Vanessa Domingues , Mazzola Taís Nitsch , Lima Simone Corte Batista Souza , Morcillo André Moreno , Stephano Marco Antonio , Antonio Maria Ângela Reis de Góes , Zanolli Maria de Lurdes , Raw Isaias , Vilela Maria Marluce dos Santos
Published: March 2009

The lack of a clear correlation between the levels of antibody to pertussis antigens and protection against disease lends credence to the possibility that cell-mediated immunity provides primary protection against disease. This phase I comparative trial had the aim of comparing the in vitro cellular immune response and anti-pertussis toxin (anti-PT) immunoglobulin G (IgG) titers induced by a cellular pertussis vaccine with low lipopolysaccharide (LPS) content (wPlowvaccine) with those induced by the conventional whole-cell pertussis (wP) vaccine. A total of 234 infants were vaccinated at 2, 4, and 6 months with the conventional wP vaccine or the wPlowvaccine. Proliferation of CD3+T cells was evaluated by flow cytometry after 6 days of peripheral blood mononuclear cell culture with stimulation with heat-killedBordetella pertussisor phytohemagglutinin (PHA). CD3+, CD4+, CD8+, and T-cell receptor γδ-positive (γδ+) cells were identified in the gate of blast lymphocytes. Gamma interferon, tumor necrosis factor alpha, interleukin-4 (IL-4), and IL-10 levels in supernatants and serum anti-PT IgG levels were determined using enzyme-linked immunosorbent assay (ELISA). The net percentage of CD3+blasts in cultures withB. pertussisin the group vaccinated with wP was higher than that in the group vaccinated with the wPlowvaccine (medians of 6.2% for the wP vaccine and 3.9% for the wPlowvaccine;P= 0.029). The frequencies of proliferating CD4+, CD8+, and γδ+cells, cytokine concentrations in supernatants, and the geometric mean titers of anti-PT IgG were similar for the two vaccination groups. There was a significant difference between the T-cell subpopulations forB. pertussisand PHA cultures, with a higher percentage of γδ+cells in theB. pertussiscultures (P< 0.001). The overall data did suggest that wP vaccination resulted in modestly better specific CD3+cell proliferation, and γδ+cell expansions were similar with the two vaccines.
Rapid Mycobacterial Liquid Culture-Screening Method forMycobacterium aviumComplex Based on Secreted Antigen-Capture Enzyme-Linked Immunosorbent Assay
Authors: Shin Sung Jae , Anklam Kelly , Manning Elizabeth J. B. , Collins Michael T.
Published: March 2009

Sensors in automated liquid culture systems for mycobacteria, such as MGIT, BacT/Alert 3D, and Trek ESP II, flag growth of any type of bacteria; a positive signal does not mean that the target mycobacteria are present. All signal-positive cultures thus require additional and often laborious testing. An immunoassay was developed to screen liquid mycobacterial cultures for evidence ofMycobacterium aviumcomplex (MAC). The method, called the MAC-enzyme-linked immunosorbent assay (ELISA), relies on detection of MAC-specific secreted antigens in liquid culture. Secreted MAC antigens were captured by the MAC-ELISA with polyclonal anti-Mycobacterium aviumsubsp.paratuberculosischicken immunoglobulin Y (IgY), detected using rabbit anti-MAC IgG, and then revealed using horseradish peroxidase-conjugated goat anti-rabbit IgG. When the MAC-ELISA was evaluated using pure cultures of known mycobacterial (n= 75) and nonmycobacterial (n= 17) organisms, no false-positive or false-negative MAC-ELISA results were found. By receiver operator characteristic (ROC) analysis of 1,275 previously identified clinical isolates, at the assay optimal cutoff the diagnostic sensitivity and specificity of the MAC-ELISA were 92.6% (95% confidence interval [95% CI], 90.3 to 94.5) and 99.9% (95% CI, 99.2 to 100), respectively, with an area under the ROC curve of 0.992. Prospective evaluation of the MAC-ELISA with an additional 652 clinical samples inoculated into MGIT ParaTB medium and signaling positive per the manufacturer's instructions found that the MAC-ELISA was effective in determining those cultures that actually contained MAC species and warranting the resources required to identify the organism by PCR. Of these 652 MGIT-positive cultures, the MAC-ELISA correctly identified 96.8% (of 219 MAC-ELISA-positive cultures) as truly containing MAC mycobacteria, based on PCR or high-performance liquid chromatography (HPLC) as reference tests. Only 6 of 433 MGIT signal-positive cultures (1.4%) were MAC-ELISA false negative, and only 7 of 219 MGIT signal-negative cultures (3.2%) were false positive. The MAC-ELISA is a low-cost, rapid, sensitive, and specific test for MAC in liquid cultures. It could be used in conjunction with or independent of automated culture reading instrumentation. For maximal accuracy and subspecies-specific identification, use of a confirmatory multiplex MAC PCR is recommended.
Antibody Response to Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Nonstructural Proteins and Implications for Diagnostic Detection and Differentiation of PRRSV Types I and II
Authors: Brown Elizabeth , Lawson Steven , Welbon Craig , Gnanandarajah Josephine , Li Juan , Murtaugh Michael P. , Nelson Eric A. , Molina Ramon M. , Zimmerman Jeffery J. , Rowland Raymond R. R. , Fang Ying
Published: March 2009

To further characterize the humoral immune response of pigs to porcine reproductive and respiratory syndrome virus (PRRSV), direct enzyme-linked immunosorbent assays (ELISA) were used to study the kinetics of antibody responses directed against PRRSV nonstructural proteins in pigs experimentally exposed to the virus. The highest immunoreactivities were against nsp1, nsp2, and nsp7. Using the recombinant nsp7 as an antigen, we validated a dual ELISA for the simultaneous detection and differentiation of serum antibodies against type I and type II PRRSV. Receiver operating characteristic analysis based on 1,334 known-positive and 1,357 known-negative samples showed good specificity (98.3% to type I and 99.3% to type II) and sensitivity (97.4% for type I and 99.8% for type II). To differentiate type I and type II PRRSV, 470 sera originating from experimentally inoculated pigs were tested, and positive sera were correctly differentiated in 469 of 470 samples. The capability of the nsp7 dual ELISA to detect serum antibody responses from pigs infected with various genetically different field strains was determined. The nsp7 dual ELISA possessed 97.6% agreement with the Idexx HerdChek PRRS 2XR ELISA. In further testing of Idexx ELISA suspected false-positive samples, the nsp7 dual ELISA resolved 98% of the samples as negative. Taken together, these results indicate that the nsp7 dual ELISA can be used as a differential test for PRRSV serology with high levels of sensitivity and specificity. This ELISA offers an additional tool for routine or follow-up diagnostics, as well as having substantial value in epidemiological surveys and outbreak investigations.
Molecular Genetic Characterization of the Merozoite Surface Protein 1 Gene of
Plasmodium vivax
from Reemerging Korean Isolates
Authors: Kim So-Hee , Hwang Seung-Young , Shin Jeong Hwan , Moon Chi-Sook , Kim Dong-Wook , Kho Weon-Gyu
Published: March 2009

Plasmodium vivax
merozoite surface protein 1 (PvMSP-1) has been considered a major candidate for the development of an antimalaria vaccine, but the molecule exhibits antigenic diversity among isolates. The extent of genetic polymorphism in the region between interspecies conserved blocks 4 and 5 (ICB4 and ICB5) of the PvMSP-1 gene was analyzed for 30 Korean isolates. Two genotypes, SK-A and SK-B, were identified on the basis of amino acid substitution. Almost all the amino acid sequences of the Korean isolates were nearly identical to those of the Solomon Island isolate Solo-83 (97.8 to 99.9% similarity) and Philippine isolates Ph-79, Ph-52-2, and Ph-49 (97.3 to 99.8% similarity). Also, we report two sequences in the isolates that were characterized on the basis of restriction fragment length polymorphism (RFLP). The RFLP profiles following digestion with the DraI restriction enzyme produced two distinguishable patterns. This study might be the first report of the region between ICB4 and ICB5 of the MSP-1 gene of
P. vivax
in South Korea.
Low Rates of
Pseudomonas aeruginosa
Misidentification in Isolates from Cystic Fibrosis Patients
Authors: Kidd Timothy J. , Ramsay Kay A. , Hu Honghua , Bye Peter T. P. , Elkins Mark R. , Grimwood Keith , Harbour Colin , Marks Guy B. , Nissen Michael D. , Robinson Philip J. , Rose Barbara R. , Sloots Theo P. , Wainwright Claire E. , Bell Scott C.
Published: March 2009

Pseudomonas aeruginosa
is an important cause of pulmonary infection in cystic fibrosis (CF). Its correct identification ensures effective patient management and infection control strategies. However, little is known about how often CF sputum isolates are falsely identified as
P. aeruginosa
. We used
P. aeruginosa
-specific duplex real-time PCR assays to determine if 2,267
P. aeruginosa
sputum isolates from 561 CF patients were correctly identified by 17 Australian clinical microbiology laboratories. Misidentified isolates underwent further phenotypic tests, amplified rRNA gene restriction analysis, and partial 16S rRNA gene sequence analysis. Participating laboratories were surveyed on how they identified
P. aeruginosa
from CF sputum. Overall, 2,214 (97.7%) isolates from 531 (94.7%) CF patients were correctly identified as
P. aeruginosa
. Further testing with the API 20NE kit correctly identified only 34 (59%) of the misidentified isolates. Twelve (40%) patients had previously grown the misidentified species in their sputum.
Achromobacter xylosoxidans
(
n
= 21),
Stenotrophomonas maltophilia
(
n
= 15), and
Inquilinus limosus
(
n
= 4) were the species most commonly misidentified as
P. aeruginosa
. Overall, there were very low rates of
P. aeruginosa
misidentification among isolates from a broad cross section of Australian CF patients. Additional improvements are possible by undertaking a culture history review, noting colonial morphology, and performing stringent oxidase, DNase, and colistin susceptibility testing for all presumptive
P. aeruginosa
isolates. Isolates exhibiting atypical phenotypic features should be evaluated further by additional phenotypic or genotypic identification techniques.
Clostridium glycolicum
Wound Infections: Case Reports and Review of the Literature
Authors: Jiang Wei , Abrar Sahibzada , Romagnoli Mark , Carroll Karen C.
Published: March 2009

We describe two cases of
Clostridium glycolicum
wound infections in immunocompetent adults. The bacterium was identified by 16S rRNA gene sequencing. This is the third published report of the recovery of this organism from human clinical material and highlights the importance of the organism as a potential human pathogen. Our report extends the spectrum of the diseases caused by
C. glycolicum
.
The putative tumour modifier gene ATP5A1 is not mutated in human colorectal cancer cell lines but expression levels correlate with TP53 mutations and chromosomal instability
Authors: Seth R , Keeley J , Abu-Ali G , Crook S , Jackson D , Ilyas M
Published: March 2009

Background:

Both the putative modifier gene ATP5a1 and the tumour suppressor gene TP53 are involved in the regulation of apoptosis and may be involved in the development of colorectal cancers.

Aims:

To investigate the relationship between these genes in 16 colorectal cancer cell lines.

Methods:

Each gene was screened for mutation using high resolution melting analysis and sequencing. Expression of ATP5a1 mRNA was tested by quantitative PCR.

Results:

Sequence changes in ATP5a1 were found in 9/16 (56%) cell lines and consisted of mainly novel single nucleotide polymorphisms (SNPs) found in the 5′ UTR, introns 4/5/9 and exon 7. TP53 mutations were also found in 9/16 (56%) cell lines; these were consistent with previous reports. High levels of ATP5a1 expression were seen in cell lines with TP53 mutation compared with those with wild type TP53 (p = 0.02). Furthermore, an A→G change at the −18 position in intron 4 of ATP5a1 was significantly associated with increased gene expression (p = 0.0391). Comparison with genotype showed that cell lines with chromosomal instability (CIN) had significantly higher levels of ATP5a1 expression than those with microsatellite instability (MSI) (p = 0.02).

Conclusion:

Higher levels of ATP5a1 expression are associated with certain SNPs and withTP53mutation. High expression also occurs in CIN and may facilitate tumour development along this pathway. Conversely, low levels of ATP5a1 expression may facilitate development of tumours with MSI.
Aging in fish
Authors: Craig J. F.
Published: March 2009

Theories on aging are well advanced but empirical data lag far behind them mainly because few fish populations are unexploited and are allowed to reach old age. There is more evidence supporting the theory of genetic aging controlled by a biological clock than aging by random damage, but the two are probably interconnected. Growth and natural mortality are closely correlated between and within species and populations. Fast growth and early maturity curtail the life-span; slow growth and late maturity have the reverse effect. There appears to be a trade-off between reproductive effort and longevity to ensure the production of the maximum number of progeny over the life-span of the mature adults. This trade-off is influenced by a feedback system dependent on reproductive success. Genetic control of growth and thus mortality is not well understood and is obscured by environmental factors. Anatomical and physiological changes with age are similar to those of mammals and include the appearance of malignant tumors. Changes in growth and natural mortality have an important influence on yield and recruitment in fisheries. The understanding of aging processes lies in an improved knowledge of bioenergetic processes and the environmental factors that control them.
Predatory behaviour of squid (Illex illecebrosus) feeding on surface swarms of euphausiids
Authors: Nicol S. , O'dor R. K.
Published: March 2009

Squid (lllex illecebrosus) were observed and filmed feeding on daytime surface swarms of the euphausiid, Meganyctiphanes norvegien. in the Bay of Fundy. The squid captured euphausiids by tentacular attack, a predatory behaviour described previously for this and other species of squid feeding on mobile prey. This method of prédation is quite different from the only other documented account of squid feeding on euphausiid surface swarms.