bluuebunny/crossref_metadata_2025 huggingface dataset:
Economic Transportation Risk Assessment From Offshore Oil Fields to Refineries
Authors: Mendes Renato F. , Porto Silva Kleber J. A. , Oliveira Luiz Fernando S.
Published: March 2009

This paper describes an analysis of the transportation reliability and economic risk associated with potential accidents during the lifetime of a brand new enterprise. The methodology was applied during the technical-financial assessment of offshore and onshore transportation from oil fields to refineries. It considered operations involving the potential for environment damage and business interruption. The case study considered two major configurations: Maritime+Pipelines: combining FPSOs (Floating Production, Storage and Offloading), tankers, terminals, and onshore pipelines; and Pure Pipelines: SSs (Semi-submersibles) and offshore and onshore pipeline system conveying oil to refineries. Each installation/activity with potential to generate an accident was represented by one block on the diagram, in the reliability study. The consequences to the transportation enterprise were defined based on economic impact. It was necessary to mine information on the environmental costs of past accidents within the company, as well as worldwide. Business interruption was considered for the transportation project and also for the refineries connected in the process. The risk for each route configuration from oil field to refinery was developed by plotting the frequency and consequence data in a spreadsheet for each activity along the transportation route. As a result we developed a comparative risk analysis table to support a major financial assessment. Beyond the traditional process of assessing projects in terms of investment and return, PETROBRAS is now considering other aspects, such as potential accidents that may play a role in assessing financial feasibility.
Length Effects on Fatigue Behavior of Longitudinal Pipeline Dents
Authors: Rinehart Adam J. , Keating Peter B.
Published: March 2009

Dent length has been shown to have a significant effect on the fatigue cracking behavior of pipeline dents. Long dents, which experience rerounding and center cracking, have a dramatically shorter fatigue life than otherwise similar short dents, which experience peripheral cracking and little rerounding. Because the fatigue lives of long dents are much shorter than those of short dents, both safety and economy would benefit from improvements in the ability to distinguish long dents from short dents. Based on experimental evidence, a transition between short and long dent behavior is shown to exist. Finite element models are used to further explore the nature of this transition by allowing the examination of cases not available in the experimental record and by permitting stress behavior to be studied. A parametric study is used to quantify the nature of the short dent to long dent transition for a range of cases. Relative dent lengths that bound short and long dent regions of behavior are proposed for these cases.
New Electromagnetic Methods to Locate and Assess Buried CP Problems
Authors: Parker Gordon W.
Published: March 2009

In this era of increased market competitiveness and the need for cost reduction strategies, natural gas pipeline and local distribution companies are now able to control the growth of their cathodic protection (CP) pipeline maintenance costs with the emergence of several new tools and related methods for diagnosing CP problems. In the early 1990’s, corrosion control engineers at the Southern California Gas Company (SoCal) were encouraged to find new methods to reduce maintenance costs associated with the company’s approximately 173 million feet of cathodically protected pipelines, mains and services. Mindful of how the maintenance problems in their CP systems were typically being resolved, an intriguing concept was conceived that could potentially reduce these costs and increase productivity by at least 40%. Driven to become more cost efficient, SoCal and the Pacific Gas and Electric Company (PG&E) in conjunction with the Gas Research Institute, now Gas Technology Institute (GTI) partnered with Radiodetection Corporation in the mid-90’s to research and design a more efficient way of troubleshooting and fault finding on CP systems. Radiodetections experience with electromagnetic detection equipment resulted in a family of non-invasive and cost-effective techniques to evaluate coating quality and to detect and record the flow of desired and interfering CP currents. The productivity gains and cost savings produced by this technology are significant. Additionally, problems that may have been difficult or impossible to detect now can be found allowing proactive and preventative maintenance. A history of these developments is discussed along with a brief review of the instruments technical aspects and capabilities. Typical field case studies are shown that demonstrate the improved corrosion control troubleshooting efficiencies available with these new technologies.
Rotational Vibration Response of Power Transmission Systems
Authors: Berri Sidi M.
Published: March 2009

The main goal of monitoring systems for rotary machinery is to provide sufficient time between warning and failure of machine elements so that safety procedures can be implemented. The present study investigates the dynamics of transmission systems by interpreting the interaction dynamic loads of the elements of the system. This phase of the effort concerns itself with the determination of the relationship of the dynamic tooth loads to the crack size of a single cracked tooth of a spur gear pair. A mathematical model of the test rig used for the general study is proposed. In addition to accounting for the time-varying stiffness of the meshing tooth pair, the model also includes gear errors and damping. A Newmark-Beta numerical integration scheme is used to solve the system of non-linear coupled equations. Results for the dynamic tooth loads as a function of crack size are presented for a wide range of rotational speeds. Simulated and experimental vibrational signals are also presented.
Automated Ultrasonic Testing for Mapping and Correlation With ILI Internal Pitting Measurements
Authors: Scott Bryan R. , Jolivette David K. , Sjerve Eric M.
Published: March 2009

This paper presents a methodology for automated ultrasonic inspection of internal corrosion on product pipelines. The automated process replaces the standard manual methods of inspection and uses the ultrasonic ILI tool data to localize the areas of corrosion on the exposed joint. Typically, only the bottom part of the pipe must be inspected due to the predominant damage mechanism being sediment fallout that tends to collect on the bottom of the pipelines producing a corrosive environment. The result is a superior inspection, due to the increased speed, reliability and reproducibility that automated inspection provides. The ultrasonic ILI tool data and the automated ultrasonic data can also be directly compared to each other to provide a quantitative comparison between the two inspection methods. This has shown that the ILI data and the automated ultrasonic data correlated well with regards to the location and overall corrosion dimensions.
Guidelines in Pulsation Studies for Reciprocating Compressors
Authors: Howes Brian C. , Greenfield Shelley D.
Published: March 2009

While new gas compression in pipeline service tends to be dominated by centrifugal machines, reciprocating compressors still have a significant place in the industry. Specific dynamic design is required to ensure reliable and efficient operation of all reciprocating compressor installations. This requirement is particularly significant in pipeline installations, because the compressor is intended to be in service for many years, and because high efficiency is important for economic reasons. It is widely recognized that the design of these types of installations should include a “pulsation study”. A pulsation study involves analysis of the proposed installation to predict pulsation, vibration, and stress levels. Further, a pulsation vibration control scheme is developed as part of the overall design. The objective is to ensure that predicted pulsation and vibration levels meet guidelines while limiting associated pressure drops and horsepower losses to acceptable levels. Various guidelines have been used in these studies, but the most commonly used standards are in API 618. While this standard was not originally intended for pipeline service, in reality it represents the best design standard available for high specification reciprocating compressor installations in any application. Recently, work has been done to upgrade the API 618 design standard. One of the changes in the proposed new 5th edition is the addition of unbalanced force guidelines to the existing pressure pulsation guidelines. Much discussion occurred regarding the need for and the advisability of making the addition. Real examples show designs in which a reduction of pressure pulsation is accompanied by an increase in unbalanced forces, illustrating the need for an unbalanced force guideline. It is also shown that problems can occur due to unbalanced forces in parts of the piping system not currently addressed by the pulsation guidelines in API 618. The paper compares the current 4th Edition versus the draft 5th Edition. Comments are made on the applicability of the various guidelines. While API 618 is the best available design document, the addition of force guidelines will help API 618 do a better job for industry.
Dynamics of Towed Cables With Active Controls
Authors: Ersdal Svein , Faltinsen Odd M.
Published: March 2009

The transverse dynamics of a towed cable was studied both experimentally and analytically. Forced oscillation was applied on the upstream end of a cable towed in its longitudinal direction, while transverse motion in the downstream end was restricted by springs. Reynolds numbers based on length were in the 6.5 − 32.5 × 106 range and cable length to diameter ratio was 1180. The amplitude of the forced motion was 4.55 diameters. The transverse response was measured at two locations and compared to results from computer simulation, showing that the model known as the Paidoussis equation overpredicted the response by a factor of two around resonance. Modification of force coefficients with respect to a modified KC number improved the results, but important trends were not captured. Curve fitting the cross flow drag coefficient to experimental data gave a result 3.3 times the drag coefficient past a cylinder in supercritical flow. The discrepancies are believed to be caused by forward speed effect on the formation of vortices and the transient behavior of the wake, but the physics of this is not clear.
Fibre Rope Moorings for Shallow Waters
Authors: Bindingsbo̸ Arne Ulrik
Published: March 2009

During the last decade significant research has been carried out related to use of fiber ropes as moorings lines for offshore vessels. Most of this research work has been related to use in deep waters as taut mooring systems. The advantages of using fiber ropes include better station keeping, reduced vertical load on vessel, small footprint on seabed compared with conventional chain/wire systems. Due to very congested seabed at some drilling locations Norsk Hydro decided to use polyester fiber rope inserts for crossing of pipelines instead of wire segments and uplift buoys. Fiber rope inserts were used at seven drilling locations in water depths ranging from less than 100 m to 330 m. The mobile drilling units were Scarabeo 6 and Transocean Arctic. Two to four mooring lines had polyester inserts with lengths of approximately 800 m. The corresponding breaking strength was 1000 tons. With the use of modern anchor handling vessels (AHT) there was no rig time lost using the fiber inserts. No modifications were done to any of the AHTs. The crews were briefed onboard the AHTS and no problems occurred during installations. The only precautions taken was to clean the AHTS deck before spooling/unspooling the polyester rope. In addition two 5–7 ton spring buoys were used on each mooring line to avoid seabed contact with the rope. The ropes were inspected by DNV before installation. Our experience was only positive and fiber ropes inserts are now considered a proven tool for mooring of drilling rigs in congested seabed areas.
Statistical Properties of Envelope Field for Gaussian Sea Surface
Authors: Podgo´rski Krzysztof , Rychlik Igor
Published: March 2009

The envelope process is a useful analytical tool which is often used to study wave groups. Most research on statistical properties of the envelope, and thus of wave groups, was focused on one dimensional records. However for the marine application, an appropriate concept should be two dimensional in space and variable in time. Although a generalization to higher dimensions was introduced by Adler (1978), little work was done to investigate its features. Since the envelope is not defined uniquely and its properties depend on a chosen version, we discuss the definition of the envelope field for a two dimensional random field evolving in time which serves as a model of irregular sea surface. Assuming Gaussian distribution of this field we derive sampling properties of the height of the envelope field as well as of its velocity. The latter is important as the velocity of the envelope is related to the rate at which energy is transported by propagating waves. We also study how statistical distributions of group waves differ from the corresponding ones for individual waves and how a choice of a version of the envelope affects its sampling distributions. Analyzing the latter problem helps in determination of the version which is appropriate in an application in hand.
Coat-Back Length: In Passive Fire Protection of Offshore Installations
Authors: Yasseri Sirous F.
Published: March 2009

The prime objective of the fire resistance design of offshore topside structures is to retain stability and integrity of the Temporary Refuge (TR) and means of escape for a specified period of time. There is one additional prime objective of the fire resistant design of offshore topside structure, namely to prevent excessive deflections developing during the fire, which would cause loss of support of hydrocarbon equipment, new leaks forming resulting in additional explosion and fire. One of several measures taken to achieve this goal is to protect members required for safe operation of the TR with Passive Fire Protection (PFP). This selection of important members, which are either part of the framing which provide support to TR or carry heavy items, forms a stable minimal structure. The rest of topside can be allowed to degrade in a fire. The extent of PFP is kept as low as practicable to keep the deck weight down and to aid maintenance and structural monitoring. However, there unprotected members that are connected to this minimal structure and potentially could be transmit heat. To limit heat flow through these unprotected members into protected members of the minimal structure, PFP is applied to a part of the unprotected member where they are connected to the protected member. This partial coating is referred to as Coat-back. This paper addresses the problem of determining the optimal length for coat-back by deriving a closed form solution using the theory of heat transfer. Results of the analytical method are compared with experimental results, as well as those obtained using finite element methods. Correct calculation of the coat-back length has great economical and safety implications for a structure under fire attack. The application of the method is shown by several worked examples.
Fatigue of 28-inch Titanium Riser: SN Data and Defect Assessment
Authors: Berge Stig , Mainc¸on Philippe , Hauge Mons
Published: March 2009

Qualification testing was carried out on full scale titanium pipes for a gas export riser from the A˚sgard B platform. Prototype pipe sections with girth welds produced by the TIG process were delivered from three different suppliers. The wall thickness was 30 mm. The pipes were sectioned into fatigue specimens and tested in constant amplitude loading in air. The loading was transverse to the weld, simulating axial and bending loading of the pipe. Secondary stresses were measured on each specimen. SN data were obtained for the welds and compared with proposed design curves. The fracture surfaces were investigated with scanning electron microscopy, and defects were categorised and sized. Fracture mechanics analysis was carried out and the results were compared with experimental data. Problems relating to fracture mechanics modelling for fatigue life prediction and defect assessment of titanium welds were discussed.
Alternative Fatigue Lifetime Prediction Formulations for Variable-Amplitude Loading
Authors: Nijssen R. P. L. , van Delft D. R. V. , van Wingerde A. M.
Published: March 2009

Possible alternative fatigue formulations to predict lifetime under variable-amplitude loading are investigated. Test results of WISPER and WISPERX variable-amplitude tests on a material representative for wind turbine rotor blades are used. All fatigue calculations are performed using Rainflow counting of the WISPER(X) load histories and employing the Miner summation. The formulation of the SN-curve and the constant-life diagram are varied. Commonly, a log-log SN-curve is used in combination with a linear Goodman constant-life relation. However, in previous work, it was found that these formulations overestimate lifetime of specimens subjected to the variable-amplitude WISPER and WISPERX load histories. This previous work suggested that the SN-formulation be changed and also used an alternative constant-life formulation with parallel lines. These formulations and variations on them are investigated. Also, constant-amplitude data for R = 0.1 are included to construct an alternative constant-life diagram. Including R = 0.1 constant-amplitude data in the lifetime predictions for WISPER(X) seems to improve the accuracy of the calculation. The alternative constant-life formulation might remove the non-conservatism from the lifetime prediction and account for the difference in lifetime between WISPER and WISPERX.
Challenges in Modeling the Unsteady Aerodynamics of Wind Turbines
Authors: Leishman J. Gordon
Published: March 2009

Many of the aerodynamic phenomena contributing to the observed effects on wind turbines are now known, but the details of the flow are still poorly understood and are challenging to predict accurately, issues discussed herein include the modeling of the induced velocity field produced by the vortical wake behind the turbine, the various unsteady aerodynamic issues associated with the blade sections, and the intricacies of dynamic stall. Fundamental limits exist in the capabilities of all models, and misunderstandings or ambiguities can also arise in how these models should be properly applied. A challenge for analysts is to use complementary experimental measurements and modeling techniques to better understand the aerodynamic problems found on wind turbines, and to develop more rigorous models with wider ranges of application.
Wind Turbines Operating in Cold Climates: Reynolds Number and Turbulence Effects on Performances
Authors: Dabin Nathalie , Leclerc Christophe , Masson Christian , Alinot Cedric
Published: March 2009

The present study is motivated by several observations of unexpected, recurring, high levels of power for stall-regulated wind turbines operating under very low temperatures. As power levels recorded largely exceed design levels of the rotor, operation in such conditions can cause dramatic damage to turbine. This study aims to understand the origin of such phenomenon by analyzing experimental data gathered from a stall-controlled wind turbine, having a nominal power of more than 500 kW, and comparing the experimental behaviour with numerical simulations. To provide a quantitative estimate of density and atmospheric turbulence effects on power output, a procedure based on the IEC 61400-12 international standard for elaboration of a wind turbine power curve is used. The numerical simulations is based on the solution of the time-averaged, steady-state, incompressible Navier-Stokes equations with an appropriate turbulence closure model. The actuator disk model, together with blade element theory, are used to model the turbines. The stall-regulated turbine analyzed has shown to produce measured power increases significantly higher than increases of density. Regarding the influence of turbulence intensity, it has been observed that for constant hub height incoming wind velocity and density, power output increases with turbulence intensity at low winds, the opposite being true at higher winds. The numerical simulations show a good agrement with the measurements.
The NREL Large-Scale Turbine Inflow and Response Experiment: Preliminary Results
Authors: Kelley Neil , Hand Maureen , Larwood Scott , McKenna Ed
Published: March 2009

The accurate numerical dynamic simulation of new large-scale wind turbine designs operating over a wide range of inflow environments is critical because it is usually impractical to test prototypes in a variety of locations. Large turbines operate in a region of the atmospheric boundary layer that currently may not be adequately simulated by present turbulence codes. In this paper, we discuss the development and use of a 42-m (137-ft) planar array of five, high-resolution sonic anemometers upwind of a 600-kW wind turbine at the National Wind Technology Center (NWTC). The objective of this experiment is to obtain simultaneously collected turbulence information from the inflow array and the corresponding structural response of the turbine. The turbulence information will be used for comparison with that predicted by currently available codes and establish any systematic differences. These results will be used to improve the performance of the turbulence simulations. The sensitivities of key elements of the turbine aeroelastic and structural response to a range of turbulence-scaling parameters will be established for comparisons with other turbines and operating environments. In this paper, we present an overview of the experiment, and offer examples of two observed cases of inflow characteristics and turbine response collected under daytime and nighttime conditions, and compare their turbulence properties with predictions.
The neural processing of masked speech: Evidence for different mechanisms in the left and right temporal lobes
Authors: Scott Sophie K. , Rosen Stuart , Beaman C. Philip , Davis Josh P. , Wise Richard J. S.
Published: March 2009

It has been previously demonstrated that extensive activation in the dorsolateral temporal lobes associated with masking a speech target with a speech masker, consistent with the hypothesis that competition for central auditory processes is an important factor in informational masking. Here, masking from speech and two additional maskers derived from the original speech were investigated. One of these is spectrally rotated speech, which is unintelligible and has a similar (inverted) spectrotemporal profile to speech. The authors also controlled for the possibility of “glimpsing” of the target signal during modulated masking sounds by using speech-modulated noise as a masker in a baseline condition. Functional imaging results reveal that masking speech with speech leads to bilateral superior temporal gyrus (STG) activation relative to a speech-in-noise baseline, while masking speech with spectrally rotated speech leads solely to right STG activation relative to the baseline. This result is discussed in terms of hemispheric asymmetries for speech perception, and interpreted as showing that masking effects can arise through two parallel neural systems, in the left and right temporal lobes. This has implications for the competition for resources caused by speech and rotated speech maskers, and may illuminate some of the mechanisms involved in informational masking.
Photoacoustic tomography with a single detector in a reverberant cavity
Authors: Cox B. T. , Beard P. C.
Published: March 2009

In conventional biomedical photoacoustic tomography (PAT), ultrasonic pulses generated through the absorption of nanosecond pulses of near-infrared light are recorded over an array of detectors and used to recover an image of the initial acoustic pressure distribution within soft tissue. This image is related to the tissue optical coefficients and therefore carries information about the tissue physiology. For high resolution imaging, a large-area detector array with a high density of small, sensitive elements is required. Such arrays can be expensive, so reverberant-field PAT has been suggested as a means of obtaining PAT images using arrays with a smaller number of detectors. By recording the reflections from an acoustically reverberant cavity surrounding the sample, in addition to the primary acoustic pulse, sufficient information may be captured to allow an image to be reconstructed without the need for a large-area array. An initial study using two-dimensional simulations was performed to assess the feasibility of using a single detector for PAT. It is shown that reverberant-field data recorded at a single detector are sufficient to reconstruct the initial pressure distribution accurately, so long as the shape of the reverberant cavity makes it ray-chaotic. The practicalities of such an approach to photoacoustic imaging are discussed.
Laser ultrasonic inspection of the microstructural state of thin metal foils
Authors: Balogun O. , Huber R. , Chinn D. , Spicer J. B.
Published: March 2009

A laser-based ultrasonic technique suitable for characterization of the microstructural state of metal foils is presented. The technique relies on the measurement of the intrinsic attenuation of laser-generated longitudinal waves at frequencies reaching 1 GHz resulting from ultrasonic interaction with the sample microstructure. In order to facilitate accurate measurement of the attenuation, a theoretical model-based signal analysis approach is used. The signal analysis approach isolates aspects of the measured attenuation that depend strictly on the microstructure from geometrical effects. Experimental results obtained in commercially cold worked tungsten foils show excellent agreement with theoretical predictions. Furthermore, the experimental results show that the longitudinal wave attenuation at gigahertz frequencies is strongly influenced by the dislocation content of the foils and may find potential application in the characterization of the microstructure of micron thick metal foils.
Conformal Fourier wavenumber decompositions on continuous differentiable surfaces
Authors: Romano Anthony J. , Abraham P. B. , Valdivia N. P. , Houston B. H. , Bucaro J. A. , Dey S.
Published: March 2009

In this manuscript, a method is introduced for the evaluation of Fourier wavenumber decompositions on C1 vibrating surfaces for spatial-spectral analysis. Whereas typical Fourier analysis is restricted to geometries that are separable for meaningful interpretations of the corresponding wave motion, this approach allows for conformal spectral analysis along curved surfaces. This is accomplished by restricting the wavevectors to lie within the local tangent to the surface and to be spatially dependent. The theoretical development is presented and it is demonstrated that commonly utilized kernels appropriate for some simple geometries can be recovered. Additionally, this approach is applied in the analysis of the vibration and radiation of a point driven, fluid loaded cone, where the displacements and pressures have been obtained using the finite element method.
Measurements of three-dimensional propagation in a continental shelf environment
Authors: Heaney Kevin D. , Murray James J.
Published: March 2009

Although a significant amount of theoretical and numerical modeling effort has been put into the study of three-dimensional (3D) acoustic propagation on a coastal wedge, including the development of the ASA 3D benchmark problem set, there have been few observations of the predicted 3D propagation effects. Significant horizontal multipath arrivals were observed in a pair of acoustic transmission tests on the continental shelf off the east coast of Florida in September 2007 and February 2008. For many transmissions, arrivals were received coming from nearly the global positioning system (GPS) bearing of the ship, as well as up to 30 deg inshore of the true bearing. The inshore path was up to 25 dB stronger than the direct path in some cases. The experimental waveforms transmitted included continuous-wave transmissions ranging in frequency from 24 to 415 Hz as well as wideband linear frequency modulation pulses (20–420 Hz). Horizontal multipath arrivals were observed for source ranges from 10 to 80 km, source depths of 20 and 100 m, and along several different bearings (inshore and along the 250 m isobath). It is a conclusion of this paper that the bearing bias and multiple horizontal arrivals are the result of 3D propagation due to the local shoaling bathymetry.
Nonlinear nonclassical elasticity applied to the analysis of low frequency flexural vibrations: Theory and experiments
Authors: Perez-Miravete Ignacio Tinao , Campos-Pozuelo Cleofé , Perea Angel
Published: March 2009

Motivated by the increasing interest on nonlinear nondestructive damage detection, a comparison of the nonlinear elastic behavior of damaged samples and their intact state is presented. Flexural vibration is induced in thin glass plates with laser thermal shock induced micro-cracks by means of two thin piezo-ceramic patches glued in a bimorph configuration. The cases of direct excitation of a resonance and excitation of an internal resonance cases are considered. The resulting nonlinear vibrations exhibit the main features of quadratic hysteresis: linear variation of the resonance frequency and quadratic production of the third harmonic. A theoretical model for nonlinear resonant flexural vibrations based on the Preisach–Mayergoyz constitutive relations is proposed for damage quantification. Experimental comparison between the intact and damaged sample indicates an increase in the relevant nonlinearity parameter, indicating a widening of the hysteresis loop due to damage.
Verifying the attenuation of earplugsin situ: Method validation on human subjects including individualized numerical simulations
Authors: Bockstael Annelies , Van Renterghem Timothy , Botteldooren Dick , D’Haenens Wendy , Keppler Hannah , Maes Leen , Philips Birgit , Swinnen Freya , Vinck Bart
Published: March 2009

The microphone in real ear (MIRE) protocol allows the assessment of hearing protector’s (HPD) attenuation in situ by measuring the difference between the sound pressure outside and inside the ear canal behind the HPD. Custom-made earplugs have been designed with an inner bore to insert the MIRE probe containing two microphones, the reference microphone measuring the sound pressure outside and the measurement microphone registering the sound pressure behind the HPD. Previous research on a head and torso simulator reveals a distinct difference, henceforth called transfer function, between the sound pressure at the MIRE measurement microphone and the sound pressure of interest at the eardrum. In the current study, similar measurements are carried out on humans with an extra microphone to measure the sound pressure at the eardrum. The resulting transfer functions confirm the global frequency dependency found earlier, but also show substantial variability between the ears with respect to the exact frequency and amplitude of the transfer functions’ extrema. In addition, finite-difference time-domain numerical models of an ear canal with earplug are developed for each individual ear by including its specific geometrical parameters. This approach leads to a good resemblance between the simulations and their corresponding measurements.
Lateralization of stimuli with independent fine-structure and envelope-based temporal disparities
Authors: Dietz Mathias , Ewert Stephan D. , Hohmann Volker
Published: March 2009

Psychoacoustic experiments were conducted to investigate the role and interaction of fine-structure and envelope-based interaural temporal disparities. A computational model for the lateralization of binaural stimuli, motivated by recent physiological findings, is suggested and evaluated against the psychoacoustic data. The model is based on the independent extraction of the interaural phase difference (IPD) from the stimulus fine-structure and envelope. Sinusoidally amplitude-modulated 1-kHz tones were used in the experiments. The lateralization from either carrier (fine-structure) or modulator (envelope) IPD was matched with an interaural level difference, revealing a nearly linear dependence for both IPD types up to 135°, independent of the modulation frequency. However, if a carrier IPD was traded with an opposed modulator IPD to produce a centered sound image, a carrier IPD of 45° required the largest opposed modulator IPD. The data could be modeled assuming a population of binaural neurons with a physiological distribution of the best IPDs clustered around 45°–50°. The model was also used to predict the perceived lateralization of previously published data. Subject-dependent differences in the perceptual salience of fine-structure and envelope cues, also reported previously, could be modeled by individual weighting coefficients for the two cues.
Microbiologic Diagnosis of Prosthetic Shoulder Infection by Use of Implant Sonication
Authors: Piper Kerryl E. , Jacobson Melissa J. , Cofield Robert H. , Sperling John W. , Sanchez-Sotelo Joaquin , Osmon Douglas R. , McDowell Andrew , Patrick Sheila , Steckelberg James M. , Mandrekar Jayawant N. , Fernandez Sampedro Marta , Patel Robin
Published: March 2009

We recently described a sonication technique for the diagnosis of prosthetic knee and hip infections. We compared periprosthetic tissue culture to implant sonication followed by sonicate fluid culture for the diagnosis of prosthetic shoulder infection. One hundred thirty-six patients undergoing arthroplasty revision or resection were studied; 33 had definite prosthetic shoulder infections and 2 had probable prosthetic shoulder infections. Sonicate fluid culture was more sensitive than periprosthetic tissue culture for the detection of definite prosthetic shoulder infection (66.7 and 54.5%, respectively;
P
= 0.046). The specificities were similar (98.0% and 95.1%, respectively;
P
= 0.26).
Propionibacterium acnes
was the commonest species detected among culture-positive definite prosthetic shoulder infection cases by periprosthetic tissue culture (38.9%) and sonicate fluid culture (40.9%). All subjects from whom
P. acnes
was isolated from sonicate fluid were male. We conclude that sonicate fluid culture is useful for the diagnosis of prosthetic shoulder infection.
Multiplex PCR Testing Detection of Higher-than-Expected Rates of CervicalMycoplasma,Ureaplasma, andTrichomonasand Viral Agent Infections in Sexually Active Australian Women
Authors: McIver Christopher J. , Rismanto Nikolas , Smith Catherine , Naing Zin Wai , Rayner Ben , Lusk M. Josephine , Konecny Pamela , White Peter A. , Rawlinson William D.
Published: March 2009

Knowing the prevalence of potential etiologic agents of nongonococcal and nonchlamydial cervicitis is important for improving the efficacy of empirical treatments for this commonly encountered condition. We describe four multiplex PCRs (mPCRs), designated VDL05, VDL06, VDL07, and VDL09, which facilitate the detection of a wide range of agents either known to be or putatively associated with cervicitis, including cytomegalovirus (CMV), enterovirus (EV), Epstein-Barr virus (EBV), varicella-zoster virus (VZV), herpes simplex virus type 1 (HSV-1), and herpes simplex virus type 2 (HSV-2) (VDL05);Ureaplasma parvum,Ureaplasma urealyticum,Mycoplasma genitalium, andMycoplasma hominis(VDL06);Chlamydia trachomatis,Trichomonas vaginalis,Treponema pallidum, and group B streptococci (VDL07); and adenovirus species A to E (VDL09). The mPCRs were used to test 233 cervical swabs from 175 women attending a sexual-health clinic in Sydney, Australia, during 2006 and 2007. The agents detected alone or in combination in all cervical swabs (percentage of total swabs) included CMV (6.0), EV (2.1), EBV (2.6), VZV (4.7), HSV-1 (2.6), HSV-2 (0.8), HSV-2 and VZV (0.4),U. parvum(57.0),U. urealyticum(6.1),M. genitalium(1.3),M. hominis(13.7),C. trachomatis(0.4),T. vaginalis(3.4), and group B streptococci (0.4). Adenovirus species A to E andT. pallidumwere not detected. These assays are adaptable for routine diagnostic laboratories and provide an opportunity to measure the true prevalence of microorganisms potentially associated with cervicitis and other genital infections.
Diversity of Spirochetes in Endodontic Infections
Authors: Sakamoto Mitsuo , Siqueira José F. , Rôças Isabela N. , Benno Yoshimi
Published: March 2009

The diversity of spirochetes in primary endodontic infections of teeth with chronic apical periodontitis or acute apical abscesses was investigated using 16S rRNA gene clone library analysis. The prevalences of three common cultivable oral
Treponema
species were also determined using species-specific nested PCR. All detected spirochetes belonged to the genus
Treponema
. Overall, 28 different taxa were identified from the 431 clones sequenced: 9 cultivable and validly named species, 1 cultivable as-yet-uncharacterized strain, and 18 as-yet-uncultivated phylotypes, 17 of which were novel. The large majority of clones (94%) were from cultivable named species. The numbers of
Treponema
species/phylotypes per selected positive sample ranged from 2 to 12. Species-specific nested PCR detected
T. denticola
,
T. socranskii
, and
T. maltophilum
in 59 (66%), 33 (37%), and 26 (29%) of the 90 cases of primary endodontic infections, respectively. Clone library analysis revealed diverse
Treponema
species/phylotypes as part of the microbiota associated with asymptomatic and symptomatic (abscess) endodontic infections. Although several as-yet-uncultivated
Treponema
phylotypes were disclosed, including novel taxa, cultivable named species were more abundant and frequently detected.
Identification of
Legionella
Species by Use of an Oligonucleotide Array
Authors: Su Hsun-Pi , Tung Seng-Kai , Tseng Lei-Ron , Tsai Wen-Cherng , Chung Tung-Ching , Chang Tsung Chain
Published: March 2009

The genus
Legionella
contains a diverse group of motile, asaccharolytic, nutritionally fastidious gram-negative rods.
Legionella pneumophila
is the most important human pathogen, followed by
L. micdadei, L. longbeachae, L. dumoffii
, and other rare species. Accurate identification of
Legionella
spp. other than
L. pneumophila
is difficult because of biochemical inertness and phenotypic identity of different species. The feasibility of using an oligonucleotide array for identification of 18 species of
Legionella
was evaluated in this study. The method consisted of PCR amplification of the macrophage infectivity potentiator
mip
gene, followed by hybridization of the digoxigenin-labeled PCR products to a panel of 30 oligonucleotide probes (16- to 24-mers) immobilized on a nylon membrane. A collection of 144 target strains (strains we aimed to identify) and 50 nontarget strains (44 species) were analyzed by the array. Both test sensitivity (144/144 strains) and specificity (50/50 strains) of the array were 100%. The whole procedure for identification of
Legionella
species by the array can be finished within a working day, starting from isolated colonies. It was concluded that species identification of clinically relevant
Legionella
spp. by the array method is very reliable and can be used as an accurate alternative to conventional or other molecular methods for identification of
Legionella
spp.
Effects of pH on the early development and growth and otolith microstructure of chinook salmon, Oncorhynchus tshawytscha
Authors: Geen G. H. , Neilson J. D. , Bradford M.
Published: March 2009

Chinook salmon (Oncorhynchus tshawytscha) eggs, alevins, and fry were reared in pH 4.5, 5.0. 5.5, 6.2 (control), and 7.0 water from the eyed stage of development. Survival through hatching was >90% in all instances. Alevin mortality was high at pH 4.5 and 5.0. Fry were more tolerant of low pH than alevins. Growth rates of alevins and fry held at or above pH 5.0 and 4.5, respectively, were not affected by pH, nor did exposure to acidic water retard otolith development or result in their resorption. One otolith daily growth increment was formed every 24 h in alevins and fry irrespective of pH. Widths of otolith daily growth increments decreased when fry were transferred to pH 4.5 water and increased on their return to higher pH indicating changes in growth rate. Transfer of fry from pH 6.2 to pH 5.0 or 5.5 had no effect on increment widths.
Hatching success in relation to egg size in painted turtles (Chrysemys picta)
Authors: Gutzke William H. N. , Packard Gary C.
Published: March 2009

Most hypotheses addressing the significance of intraspecific variation in size of reptilian eggs have focused on potential benefits accruing to the large hatchlings that usually emerge from large eggs. We find, however, that large eggs of painted turtles (Chrysemys picta) have a significantly higher probability of hatching than do small eggs incubated under many conditions of temperature and moisture. Surface area to volume considerations may account for differences in hatching success between large and small eggs incubated in dry conditions. Natural selection for size of reptilian eggs may therefore be more intense than has been suspected heretofore, because differential mortality related to egg size probably occurs in prenatal as well as early postnatal stages in the life cycle.
Effects of elevated hydrogen ion and aluminum concentrations on the survival of amphibian embryos and larvae
Authors: Clark Karen L. , Hall Ronald J.
Published: March 2009

Egg hatching success was measured for three amphibian species (Bufo americanus, Rana sylvatica, and Ambystoma maculatum) exposed to varying hydrogen ion, aluminum, and dissolved organic carbon (DOC) concentrations. In the first experiment, hatching success in six stream pools was negatively correlated with Al and DOC and positively correlated with pH. Effects of any one chemical variable, however, could not be separated from the others. In a second experiment, to separate effects of pH and Al from DOC, eggs and larvae were exposed to simulated stream pools in which pH was reduced. At pH 4.8 and 37 μg/L inorganic monomeric Al, only eggs of A. maculatum were affected. At pH 4.3, 46 μg/L inorganic monomeric Al was more toxic (compared with 34–35 μg/L at pH 4.8 and 4.3) to B. americanus and R. sylvatica embryos. Bufo americanus was more sensitive to low pH and elevated Al than R. sylvatica. Mortality of eggs of both species mainly occurred within 1 day of exposure but continued until hatching. Mortality of A. maculatum eggs, however, did not occur during the 4 days of acidification, but 2–3 weeks later, at the time of hatching. Larval survival in general was not affected by reduced pH (pH 4.3) and (or) elevated Al (up to 46 μg/L inorganic monomeric Al).
Effect of nuptial feeding on the mating behaviour of female ground crickets
Authors: Bidochka Michael J. , Snedden William A.
Published: March 2009

Female striped ground crickets, Allonemobius fasciatus, feed on male tibial glands while in copula. This behaviour has been interpreted as nuptial feeding and a method by which copula duration is increased. Females terminated copulation significantly earlier with males whose tibial spurs were covered with paint, as opposed to males with exposed tibial spurs. However, the number of successful matings was not reduced in those males whose tibial spurs were covered. The mean duration of spermatophore attachment did not differ between females mated to different experimental groups.
The effects of bird predation on an estuarine stickleback (Pisces: Gasterosteidae) community
Authors: Whoriskey F. G. , Fitzgerald G. J.
Published: March 2009

Eight species of birds fed on a community of sticklebacks living in salt marsh pools along the southern shore of the St. Lawrence estuary in May and June when the fish breed. Three birds, the black-crowned night heron (Nycticorax nycticorax), the bronzed grackle (Quiscalus quiscula), and the ring-billed gull (Larus delawarensis) accounted for 80% of the estimated captures. Bird predation removed about 30% of the sticklebacks in the marsh. Significantly more male than female Gasterosteus aculeatus and G. wheatlandi were eaten, indicating selective predation is playing a role in structuring this fish community.
Fat reserves and condition indices in greater snow geese
Authors: Gauthier G. , Bédard J.
Published: March 2009

We evaluate several external condition indices as predictors of total fat reserves (TFR) in greater snow geese. In 1979 and 1980, we collected 373 adult geese during their spring staging halt along the St. Lawrence estuary, Québec, and determined their fat content by ether extraction. Body weight (BW) alone and BW divided by various morphometric measurements are relatively poor predictors of TFR (maximum r2 = 0.56). The thickness of subcutaneous fat (measured externally with an adiposimeter) combined with BW is the best predictor of TFR (R2 = 0.65). This condition index can be useful in predicting the average condition of living geese, provided a reasonable sample size is available. We also examined some internal condition indices. Of these, the dry weight of abdominal fat is the easiest to apply and one of the most reliable (r2 = 0.86).
Occurrence of the eyefluke, Diplostomum (Diplostomum) baeri bucculentum Dubois et Rausch, 1948, in salmonid fishes of northern British Columbia
Authors: Ching Hilda Lei
Published: March 2009

As a result of experimental infections in chicks, diplostomula found in the retina of chinook salmon from the Nechako River were identified as Diplostomum (Diplostomum) baeri bucculentum. Eyeflukes in other salmonids were considered to be the same species based on similar measurements and site in the eyes. These eyeflukes varied in prevalence and mean intensity in seven salmonid species surveyed in nine localities in 1979–1981. The following fish were sampled: rainbow trout (Salmo gairdneri), 505; mountain whitefish (Prosopium williamsoni), 334; lake whitefish (Coregonus clupeaformis), 32; Dolly Varden (Salvelinus malma), 66; lake trout (S. namaycush), 13; kokanee or sockeye salmon (Oncorhynchus nerka), 323; and chinook salmon (O. tshawytscha), 164. Eyeflukes had prevalences ranging from 84 to 100% in six lakes, 64% in the river, 53% in one reservoir site, and a prevalence of 15% in the other reservoir site. Mountain and lake whitefishes had high mean intensities while kokanee had low mean intensities. Correlation of increased intensity with increased fish size was significant for 6 of 27 samples. Four samples of lake whitefish, mountain whitefish, rainbow trout, and chinook salmon showed significant asymmetry when numbers of diplostomula were compared between eyes. More of the heavily infected fish showed asymmetry than did the lightly infected fish.
New material of Psychrolutes sio (Scorpaeniformes, Psychrolutidae) from the eastern Pacific of South America and comments on the taxonomy of Psychrolutes inermis and Psychrolutes macrocephalus from the eastern Atlantic of Africa
Authors: Nelson Joseph S. , Chirichigno Norma , Balbontsín Fernando
Published: March 2009

Psychrolutes sio Nelson, previously known only from the holotype and one small paratype, is redefined from six new specimens. The species is now known to range from northernmost Peru to near Valparaíso, Chile, and to occur at depths of 700–1200 m. Psychrolutes macrocephalus (Gilchrist) is recognized as a separate species from Psychrolutes inermis (Vaillant) and as the more common species in South Africa.