bluuebunny/crossref_metadata_2025 huggingface dataset:
Compressor Washing Maintains Plant Performance and Reduces Cost of Energy Production
Authors: Stalder Jean-Pierre , van Oosten Peter
Published: February 2015

This paper reports about the results of a field test conducted over a period of 8000 operating hours on the effect of combined on line and off line compressor washing on a 66 MW gas turbine operating in a combined cycle plant at UNA’s Lage Weide 5 power plant in Utrecht. Observations have shown a sustained high output level close to the nominal guaranteed rating, despite difficult atmospheric conditions. Investigations on the correlations between fouling gradients in the compressor and atmospheric conditions are also presented. The evaluation of the results demonstrate the importance of implementing an optimised regime of on line and off line washing in the preventive turbine maintenance program. It will improve the plant profitability by reducing the costs of energy production.
An Engineering Calculation Method for Multi-Component Stagnant Droplet Evaporation With Finite Diffusivity
Authors: Chin J. S.
Published: February 2015

A practical engineering calculation method has been formulated for commercial multicomponent fuel stagnant droplet evaporation with variable finite mass and thermal diffusivity. Instead of solving the transient liquid phase mass and heat transfer partial differential equation set, a totally different approach is used. With zero or infinite mass diffusion resistance in liquid phase, it is possible to obtain vapor pressure and vapor molecular mass based on the distillation curve of these turbine fuels. It is determined that Peclet number (Pef) is a suitable parameter to represent the mass diffusion resistance in liquid phase. The vapor pressure and vapor molecular mass at constant finite Pef is expressed as a function of finite Pef, vapor pressure, and molecular mass at zero Pef and infinite Pef. At any time step, with variable finite Pef, the above equation is still valid, and PFsPef=∞, PFsPef=0, MfvPef=∞, MfvPef=0 are calculated from PFsPef≡∞, PFsPef≡0, MfvPef≡∞, MfvPef≡0, thus PFs and Mfv can be determined in a global way which eventually is based on the distillation curve of fuel.

The explicit solution of transient heat transfer equation is used to have droplet surface temperature and droplet average temperature as a function of surface Nusselt number and non-dimensional time. The effect of varying com position of multi-component fuel evaporation is taken into account by expressing the properties as a function of molecular mass, acentric factor, critical temperature, and critical pressure. A specific calculation method is developed for liquid fuel diffusion coefficient, also special care is taken to calculate the binary diffusion coefficient of fuel vapor-air in gaseous phase. The effect of Stefan flow and natural convection has been included. The predictions from the present evaporation model for different turbine fuels under very wide temperature ranges have been compared with experimental data with good agreement.
Combustion With Low Pollutant Emissions of Liquid Fuels in Gas Turbines by Premixing and Prevaporization
Authors: Poeschl G. , Ruhkamp W. , Pfost H.
Published: February 2015

This paper reports about experiments on PPM-combustion. Experiments were carried out to check the dependence between homogeneity of the mixture and pollutant emissions. An ideally homogeneous mixture could be achieved with a static mixer. Cool-flame reactions were observed and their dependences on pressure, temperature and fuel-air ratio were determinated.
Process Studies as Applied to Ceramic Gas Turbine Engine Low-Emission Double-Zone Micro-Diffusion Combustion Chamber
Authors: Sudarev A. V. , Zakharov Y. I. , Vlnogradov E. D. , Butovsky L. S. , Ranovskaya E. A. G.
Published: February 2015

Initial results of the first step (at Pa = 0.11–0.12 MPa) of an experimental investigation of the basic parameters of full-scale, micro-flame double-zone combustors with flame tubes are presented. This combustion chamber is developed for a 2.5 MW advanced ceramic gas turbine unit. (Sudarev, et al., 1991). This engine, when working at the design operation conditions, has an efficiency range of 41–46%, which is a function of using either intecooling or a heat regeneration scheme. The efficiency is the result of increasing the gas temperature to a maximum turbine inlet temperature of 1250°C and a 2.5 MW pressure ratio of 29. With such high initial parameters of the working media, the problem of nitrogen oxide emissions reduction assumes paramount importance.

The objective of the paper is to develop a combustor which would ensure NOx emissions at the design conditions not above 75 mg/Nm3 (at 15% 02) due to application of a double-stage working process of pre-mixture firing. Specific features of fuel burn-up, formation of pollutants at combustion, dependencies of combustor characteristics and upgraded algorithm of combustor loading are also shown.
Simulation of Combined Cycles With Black Liquor Gasification
Authors: Ihrén C. Niclas , Svedberg Gunnar
Published: February 2015

Black liquor, a residual of the chemical pulp industry, is a biofuel with great potential for increasing power generation. This may be accomplished by replacing the conventional recovery process using a Tomlinson recovery boiler with black liquor gasification. In addition, there are other considerable advantages.

The gasification of black liquor gives new degrees of freedom since the combustible gas may be used in a multitude of ways. For a full scale plant, a combined cycle may be an efficient way to produce process heat and power. Comparison is made with conventional CHP using a Tomlinson boiler and a steam cycle. It is shown that the generated power could be up to twice that of the conventional plant with an electrical efficiency of 30% and a total efficiency of 77% (HHV). However, the characteristics of a combined cycle in this kind of process integrated application will be quite different than those of a stand-alone powerplant. This is clearly shown when competed with conventional natural gas fired combined cycles.

This paper includes thorough analysis of some of the most important parameters of the combined cycle. It is shown that the gas turbine characteristics are the critical factors for providing a high electric efficiency. The effects of supplementary firing we also investigated. Hereby, an optimum for the steam cycle data is established.
On-Line Detergent Fluid Evaluation on a TF4OB Gas Turbine Engine
Authors: Harris Howard , Calabrese Marc
Published: February 2015

This paper presents results, evaluation, and comparisons between eleven on-line water wash detergents and water that were tested on a TF40B gas turbine engine. Comparisons were based on test cell data, field use data, environmental requirements, cost and U.S. Navy specification MIL-C-85704 Rev B, “Cleaning Compound, Turbine Engine Gas Path.” Detergents tested were: Turbotect 920 and 950, B&B TC-100, ZOK-27, R-MC, Fyrewash WB and SB. Turco 6783-50, Turboclean 2, EDC R-2701 and TEC 20. Fyrewash SB was the only solvent based online detergent tested. All other detergents were aqueous based.
The Development of the Mean Flow and Turbulence Structure in an Annular S-Shaped Duct
Authors: Britchford K. M. , Carrotte J. F. , Stevens S. J. , McGuirk J. J.
Published: February 2015

This paper describes an investigation of the mean and fluctuating flow field within an annular S-shaped duct which is representative of that used to connect the compressor spools of aircraft gas turbine engines. Data was obtained from a fully annular test facility using a 3-component Laser Doppler Anemometry (LDA) system. The measurements indicate that development of the flow within the duct is complex and significantly influenced by the combined effects of streamwise pressure gradients and flow curvature. In addition CFD predictions of the flow, using both the k-ε and Reynolds stress transport equation turbulence models, are compared with the experimental data. Whereas curvature effects are not described properly by the k-ε model, such effects are captured more accurately by the Reynolds stress model leading to a better prediction of the Reynolds shear stress distribution. This, in turn, leads to a more accurate prediction of the mean velocity profiles, as reflected by the boundary layer shape parameters, particularly in the critical regions of the duct where flow separation is most likely to occur.
Modelling Particle Deposition in Gas Turbines Employed in Advanced Coal-Fired Systems
Authors: Fackrell John E. , Brown Kevin , Young John B.
Published: February 2015

In many advanced coal-fired plant the gases being passed to the gas turbine will contain low levels of small particles. These particles may deposit on, or cause erosion of, the turbine blades, affecting the economic and technical viability of such systems. Modelling work has been undertaken to assess the effects of particulate contamination in coal-fired systems.

A number of different models for the particle behaviour have been developed and used, depending on the particular application involved. The behaviour of particles of a few microns in size and upwards is dominated by inertial effects and has been modelled by performing particle trajectory calculations in the turbine flow field, this having been first calculated with a turbine flow code.

Smaller particles tend to be deposited by a process of diffusion through the turbine blade boundary layers. Two modelling approaches have been undertaken for diffusive deposition. The simpler approach is based on a heat transfer analogy combined with extra prescriptions for thermophoresis and eddy impaction effects. The more complicated approach involves a numerical solution of the particle diffusion equation within the boundary layer, including the effects of thermophoresis and using a stopping distance model for eddy impaction effects.

Predictions from the models have been compared with experimental results at realistic conditions obtained in a PFBC rig at Grimethorpe and with laboratory results at ambient conditions.
Vibration Characteristics of Large Frame Combustion Turbines
Authors: Coslow Bill J. , Bertsch Oran L.
Published: February 2015

This paper examines the vibration characteristics of large frame land-based combustion turbines including response of the entire rotor train. The typical rotor train consists of the combustion turbine with integral axial compressor, a rigidly coupled generator, and a starting and auxiliary turning gear package connected through a flexible coupling.

Vibration characteristics during both transient and steady state conditions are considered. Analytical methods for predicting synchronous and asynchronous vibration response are examined. Actual shop and field test results am discussed including vibration components at frequencies other than running speed.

Industry standards on vibration limits are discussed with respect to current Westinghouse vibration control setting specifications.
Aerodynamic Design and 3D Navier-Stokes Analysis of a High Specific Flow Fan
Authors: Falchetti F. , Quiniou H. , Verdier L.
Published: February 2015

Advanced research is currently being conducted at Snecma to design a swept wide chord fan blade with a very high specific flow value of 230 kg/s/m2 at the aero design point instead of 212 kg/s/m2 on current turbofan engines.

This concept has the potential benefit of higher thrust than conventional engines for a given value of the fan diameter. This induces potential advantages in terms of performance (reduced nacelle drag) and installation under the wings.

These advantages are subject to the condition that we retain high fan bypass efficiency with axial Mach number close to 0.8. The intensive use of 3D Euler and 3D Navier-Stokes blade to blade computations in the aero design makes it possible to overcome this difficulty.

This paper describes the aero optimization of a swept fan blade with a specific flow of 230 kg/s/m2, a corrected tip speed of 350 m/s and a bypass pressure ratio of 1.45. Applications of the most recent numerical methods are presented, including 3D Navier-Stokes blade to blade computations.
Construction of Combined Cycle Power Generation Plants for Kawagoe Power Station by Chubu Electric Power
Authors: Mita T. , Ohara H. , Hoizumi S. , Ando N.
Published: February 2015

In response to the recent rapid increase in power demand, Chubu Electric Power is now constructing two 1,650-megawatt power plants, each consisting of seven single-shaft combined-cycle units. These will be plant Nos. 3 and 4 of the Kawagoe Power Station.

As one unit of plants, these power plants not only will be among the most powerful (in output) in the world, but will also offer the following features:

1) The main equipment of these plants, a gas turbine, will be a GE-Hitachi Model F7FA, the state-of-the-art 60 Hz model, for large equipment capacity and high efficiency. The heat recovery steam generator of each plant will use serrated fin tubes for high efficiency and compactness.

2) Plant efficiency will be at least 48.5% by means of optimizing the combined-cycle system and using the single-shaft triple-pressure reheat cycle.

3) As middle-load thermal plants, these plants are designed to use the advantages of a single-shaft combined cycle, thus offering operational convenience.

4) For global environmental preservation, which is nowadays an important concern of the local community, these plants are designed to reduce NOx emissions, warm discharge water, and noise.

5) To save labor for operation, and to improve its man-machine interface, these plant will utilize a large screen and CRT operation.

Selection of these units and systems has entailed various feasibility studies and simulations for optimization, as well as new developments and reliability verifications.

This paper takes the example of plant No. 3 to describe how the method of system selection and to present the design outline.
A New Matching Procedure for Multishaft Gas Turbines Modelled With the Mean Line Prediction Method
Authors: Hånde Bjørn M.
Published: February 2015

A new matching procedure adapted for multishaft gas turbines modelled with the mean line prediction method, is presented. Mass flow and pressure convergence is achieved with stage by stage marching in the flow direction where the high pressure and low pressure units are treated together. Independent iteration on the power balance gives a stable procedure that can be applied in static as well as dynamic simulations. The procedure can be accelerated with an algoritm combining an advanced version of the Ellipse equation with the mean line prediction method.
One of the World’s Biggest Desalination Plants in Dubai: Jebel Ali Gas Turbine and MSF Desalination Station “G”
Authors: Gilli Paul , Stroiβnig Gerhard , Povoden Rudolf
Published: February 2015

Near the city of Dubai a gas turbine and desalination station is presently being commissioned and has already partly been taken over by the client.

This project has been carried out within 34 months from the award of the order to the acceptance by the client by an international consortium.

Upon its completion the plant will produce 60 million gallons of drinking water per day and will have an electric capacity of 457 MW.

The paper presents the technical concept of steam generators of relatively big capacity and very low steam pressures for the production of saturated steam for two designs, i.e. an oil and gas fired self-supporting steam generator and a waste heat recovery boiler behind a gas turbine including a very powerful supplementary firing system.
Effervescent Atomizers for Small Gas Turbines
Authors: Li Jibao , Lefebvre Arthur H. , Rollbuhler James R.
Published: February 2015

An experimental investigation is conducted into the potential of effervescent atomizers as fuel injectors for gas turbine engines. The designs studied include three different configurations of multihole effervescent atomizers and an effervescent/airblast hybrid atomizer. In all tests the liquid employed is water. The spray characteristics investigated include drop size distributions and liquid flux distributions within the spray. The results obtained show that multi hole effervesent atomizers combine good atomization with uniform liquid flux distribution. This makes them especially suitable for application to annular combustors because they allow appreciable reductions to be made 1n the number of fuel injectors needed to achieve uniform circumferential fuel distribution. The hybrid atomizer also combines good atomization with the capability of wide cone angles.

The only drawback exhibited by these atomizers is the need for a separate supply of atomizing air. This drawback could restrict their applications to non-aeronautical gas turbine engines.
Computer aided detection of surgical retained foreign object for prevention
Authors: Hadjiiski Lubomir , Marentis Theodore C. , Chaudhury Amrita R. , Rondon Lucas , Chronis Nikolaos , Chan Heang‐Ping
Published: February 2015

Purpose:

Surgical retained foreign objects (RFOs) have significant morbidity and mortality. They are associated with approximately $1.5 × 109annually in preventable medical costs. The detection accuracy of radiographs for RFOs is a mediocre 59%. The authors address the RFO problem with two complementary technologies: a three‐dimensional (3D) gossypiboma micro tag, theμTag that improves the visibility of RFOs on radiographs, and a computer aided detection (CAD) system that detects theμTag. It is desirable for the CAD system to operate in a high specificity mode in the operating room (OR) and function as a first reader for the surgeon. This allows for fast point of care results and seamless workflow integration. The CAD system can also operate in a high sensitivity mode as a second reader for the radiologist to ensure the highest possible detection accuracy.

Methods:

The 3D geometry of theμTag produces a similar two dimensional (2D) depiction on radiographs regardless of its orientation in the human body and ensures accurate detection by a radiologist and the CAD. The authors created a data set of 1800 cadaver images with the 3DμTag and other common man‐made surgical objects positioned randomly. A total of 1061 cadaver images contained a singleμTag and the remaining 739 were withoutμTag. A radiologist marked the location of theμTag using an in‐house developed graphical user interface. The data set was partitioned into three independent subsets: a training set, a validation set, and a test set, consisting of 540, 560, and 700 images, respectively. A CAD system with modules that included preprocessingμTag enhancement, labeling, segmentation, feature analysis, classification, and detection was developed. The CAD system was developed using the training and the validation sets.

Results:

On the training set, the CAD achieved 81.5% sensitivity with 0.014 false positives (FPs) per image in a high specificity mode for the surgeons in the OR and 96.1% sensitivity with 0.81 FPs per image in a high sensitivity mode for the radiologists. On the independent test set, the CAD achieved 79.5% sensitivity with 0.003 FPs per image in a high specificity mode for the surgeons and 90.2% sensitivity with 0.23 FPs per image in a high sensitivity mode for the radiologists.

Conclusions:

To the best of the authors’ knowledge, this is the first time a 3DμTag is used to produce a recognizable, substantially similar 2D projection on radiographs regardless of orientation in space. It is the first time a CAD system is used to search for man‐made objects over anatomic background. The CAD system for theμTags achieved reasonable performance in both the high specificity and the high sensitivity modes.
Who's Teaching What in High School Physics?
Authors: White Susan , Tyler John
Published: February 2015

During the 2012–13 school year, approximately 27,000 teachers taught at least one physics course in a U.S. high school. About one-third of those teachers have earned a degree in physics or physics education; the vast majority of the others have earned degrees in a variety of other science fields.1 About 53,000 physics classes were taught, ranging from conceptual physics through AP and second-year physics classes.2 Using data from our 2012–13 Nationwide Survey of High School Physics Teachers, we look at the teaching experience and academic preparation of teachers teaching various physics classes. We see that teachers with a degree in physics or physics education teach mostly physics classes (as opposed to non-physics). Furthermore, teachers with physics teaching experience and a degree in physics or physics education teach more AP and Honors physics classes than any other group of teachers.
Drinking-Straw Microbalance and Seesaw: Stability and Instability
Authors: Chapman Peter , Glasser Leslie
Published: February 2015

The mechanics of a beam balance are little appreciated and seldom understood. We here consider the conditions that result in a stable balance, with center of gravity below the fulcrum (pivot point), while an unstable balance results when the center of gravity is above the fulcrum. The highly sensitive drinking-straw microbalance, which uses a plastic drinking straw as a rigid beam, is briefly described with some slight convenient modifications. Different placements of the center of gravity are considered analytically to explain the equilibrium neutrality, stability, and instability of such beam balances as the microbalance, the playground “seesaw” or “teeter-totter,” the “dipping bird,” and other toys and magic tricks.
Water Jets from Bottles, Buckets, Barrels, and Vases with Holes
Authors: Lopac Vjera
Published: February 2015

Observation of the water jets flowing from three equidistant holes on the side of a vertical cylindrical bottle is an interesting and widely used didactical experiment illustrating the laws of fluids in motion. In this paper we analyze theoretically and numerically the ranges of the stationary water jets flowing from various rotationally symmetric vessels with holes, and their dependence on the height of the holes above the bottom, on thickness of the block supporting the vessel, and on different shapes of the vessel profile. This investigation was motivated by controversial descriptions and illustrations repeatedly found in physics textbooks and by the fact that previously in the physics teaching literature only the cylindrical vessel was treated.
Influence of fiber orientation on the inherent acoustic nonlinearity in carbon fiber reinforced composites
Authors: Chakrapani Sunil Kishore , Barnard Daniel J. , Dayal Vinay
Published: February 2015

This paper presents the study of non-classical nonlinear response of fiber-reinforced composites. Nonlinear elastic wave methods such as nonlinear resonant ultrasound spectroscopy (NRUS) and nonlinear wave modulation spectroscopy have been used earlier to detect damages in several materials. It was observed that applying these techniques to composites materials becomes difficult due to the significant inherent baseline nonlinearity. Understanding the non-classical nonlinear nature of the composites plays a vital role in implementing nonlinear acoustic techniques for material characterization as well as qualitative nondestructive testing of composites. Since fiber reinforced composites are orthotropic in nature, the baseline response variation with fiber orientation is very important. This work explores the nature of the inherent nonlinearity by performing nonlinear resonant spectroscopy (NRS) in intact unidirectional carbon/epoxy samples with different fiber orientations with respect to major axis of the sample. Factors such as frequency shifts, modal damping ratio, and higher harmonics were analyzed to explore the non-classical nonlinear nature of these materials. Conclusions were drawn based on the experimental observations.
Spectral and temporal resolutions of information-bearing acoustic changes for understanding vocoded sentences
Authors: Stilp Christian E. , Goupell Matthew J.
Published: February 2015

Short-time spectral changes in the speech signal are important for understanding noise-vocoded sentences. These information-bearing acoustic changes, measured using cochlea-scaled entropy in cochlear implant simulations [CSECI; Stilp et al. (2013). J. Acoust. Soc. Am. 133(2), EL136–EL141; Stilp (2014). J. Acoust. Soc. Am. 135(3), 1518–1529], may offer better understanding of speech perception by cochlear implant (CI) users. However, perceptual importance of CSECI for normal-hearing listeners was tested at only one spectral resolution and one temporal resolution, limiting generalizability of results to CI users. Here, experiments investigated the importance of these informational changes for understanding noise-vocoded sentences at different spectral resolutions (4–24 spectral channels; Experiment 1), temporal resolutions (4–64 Hz cutoff for low-pass filters that extracted amplitude envelopes; Experiment 2), or when both parameters varied (6–12 channels, 8–32 Hz; Experiment 3). Sentence intelligibility was reduced more by replacing high-CSECI intervals with noise than replacing low-CSECI intervals, but only when sentences had sufficient spectral and/or temporal resolution. High-CSECI intervals were more important for speech understanding as spectral resolution worsened and temporal resolution improved. Trade-offs between CSECI and intermediate spectral and temporal resolutions were minimal. These results suggest that signal processing strategies that emphasize information-bearing acoustic changes in speech may improve speech perception for CI users.
Influence of the stimulus presentation rate on medial olivocochlear system assays
Authors: Boothalingam Sriram , Purcell David W.
Published: February 2015

Click evoked otoacoustic emissions (CEOAEs) are commonly used both in research and clinics to assay the medial olivocochlear system (MOC). Clicks presented at rates >50 Hz in the contralateral ear have previously been reported to evoke contralateral MOC activity. However, in typical MOC assays, clicks are presented in the ipsilateral ear in conjunction with MOC elicitor (noise) in the contralateral ear. The effect of click rates in such an arrangement is currently unknown. A forward masking paradigm was used to emulate typical MOC assays to elucidate the influence of ipsilateral click presentation rates on MOC inhibition of CEOAEs in 28 normal hearing adults. Influence of five click rates (20.83, 25, 31.25, 41.67, and 62.5 Hz) presented at 55 dB peSPL was tested. Results indicate that click rates as low as 31.25 Hz significantly enhance contralateral MOC inhibition, possibly through the activation of ipsilateral and binaural MOC neurons with potential contributions from the middle ear muscle reflex. Therefore, click rates ≤25 Hz are recommended for use in MOC assays, at least for 55 dB peSPL click level.
Effects of envelope bandwidth on importance functions for cochlear implant simulations
Authors: Whitmal Nathaniel A. , DeMaio Decia , Lin Rongheng
Published: February 2015

Frequency-importance functions (FIFs) quantify intelligibility contributions of spectral regions of speech. In previous work, FIFs were considered as instruments for characterizing intelligibility contributions of individual cochlear implant electrode channels. Comparisons of FIFs for natural speech and vocoder-simulated implant processed speech showed that vocoding shifted peak importance regions downward in frequency by 0.5 octaves. These shifts were attributed to voicing cue changes, and may reflect increased reliance on low-frequency information (apart from periodicity cues) for correct voicing perception. The purpose of this study was to determine whether increasing channel envelope bandwidth would reverse these shifts by improving access to voicing and pitch cues. Importance functions were measured for 48 subjects with normal hearing, who listened to vowel-consonant-vowel tokens either as recorded or as output from five different vocoders that simulated implant processing. Envelopes were constructed using filters that either included or excluded pitch information. Results indicate that vocoding-based shifts are only partially counteracted by including pitch information; moreover, a substantial baseline shift is present even for vocoders with high spectral resolution. The results also suggest that vocoded speech intelligibility is most sensitive to a loss of spectral resolution in high-importance regions, a finding with possible implications for cochlear implant electrode mapping.
Loudness of low-frequency pure tones lateralized by interaural time differences
Authors: Koehl Vincent , Paquier Mathieu
Published: February 2015

Directional loudness is that phenomenon by which the loudness of a sound may vary according to the localization of its source. This phenomenon has been mainly observed for high-frequency sounds, for sources located in the horizontal plane. Because of the acoustic shadow of the head, the left and right ear pressures are modified depending on the source azimuth and the global loudness resulting from a summation process may vary accordingly. Directional loudness has also been reported to occur at 400 Hz, where shadowing effects are usually rather small. It might therefore be suspected that directional loudness effects could be influenced by other parameters involved in the localization process. This study assessed the loudness of low-frequency pure tones (200 and 400 Hz) lateralized with headphones by applying an interaural time difference (ITD) but no interaural level difference. It showed small but significant variations of loudness with respect to ITD at a low loudness level (40 phon): ITD values associated with virtual azimuths of ±60° and ±90° led to a small but significant increase in loudness (up to 1.25 dB). However, there was no such effect at a moderate loudness level (70 phon).
Effects of age and hearing loss on recognition of unaccented and accented multisyllabic words
Authors: Gordon-Salant Sandra , Yeni-Komshian Grace H. , Fitzgibbons Peter J. , Cohen Julie I.
Published: February 2015

The effects of age and hearing loss on recognition of unaccented and accented words of varying syllable length were investigated. It was hypothesized that with increments in length of syllables, there would be atypical alterations in syllable stress in accented compared to native English, and that these altered stress patterns would be sensitive to auditory temporal processing deficits with aging. Sets of one-, two-, three-, and four-syllable words with the same initial syllable were recorded by one native English and two Spanish-accented talkers. Lists of these words were presented in isolation and in sentence contexts to younger and older normal-hearing listeners and to older hearing-impaired listeners. Hearing loss effects were apparent for unaccented and accented monosyllabic words, whereas age effects were observed for recognition of accented multisyllabic words, consistent with the notion that altered syllable stress patterns with accent are sensitive for revealing effects of age. Older listeners also exhibited lower recognition scores for moderately accented words in sentence contexts than in isolation, suggesting that the added demands on working memory for words in sentence contexts impact recognition of accented speech. The general pattern of results suggests that hearing loss, age, and cognitive factors limit the ability to recognize Spanish-accented speech.
Reflection of a plane wave from a two-layered seafloor with non-parallel interface between the layers
Authors: Papadakis Panagiotis I. , Piperakis George S. , Kalogerakis Michael A.
Published: February 2015

This work studies the reflection coefficient of a plane wave incident on a seafloor consisting of two layers (sediment and substrate), whose interface is linear but not parallel to the water-sediment interface. This is an extension of the well-established and studied reflection coefficient concept for seafloors with parallel layers. Moreover this study introduces the concept of the Coherent Reflection Coefficient (CRC) that extends the usual Rayleigh reflection coefficient definition not only at the water-sediment interface but inside the water column as well. The mathematical formulation of the CRC is derived and its numerical implementation is explained. Based on this implementation a numerical code is developed and incorporated—among other codes—in a user-friendly graphics toolbox that was built to facilitate CRC calculations. Numerical examples for realistic seafloors are presented and the derived results are compared to similar ones for parallel layers, indicating that even for small inclination angles the reflection coefficient difference between parallel and slanted interface layers is substantial, hence cannot be ignored. An imminent application of the extended seafloor model and the CRC introduced in this work is the enhancement of geophysics inversion schemes for the estimation of the seafloor parameters.
Wind noise under a pine tree canopy
Authors: Raspet Richard , Webster Jeremy
Published: February 2015

It is well known that infrasonic wind noise levels are lower for arrays placed in forests and under vegetation than for those in open areas. In this research, the wind noise levels, turbulence spectra, and wind velocity profiles are measured in a pine forest. A prediction of the wind noise spectra from the measured meteorological parameters is developed based on recent research on wind noise above a flat plane. The resulting wind noise spectrum is the sum of the low frequency wind noise generated by the turbulence–shear interaction near and above the tops of the trees and higher frequency wind noise generated by the turbulence–turbulence interaction near the ground within the tree layer. The convection velocity of the low frequency wind noise corresponds to the wind speed above the trees while the measurements showed that the wind noise generated by the turbulence–turbulence interaction is near stationary and is generated by the slow moving turbulence adjacent to the ground. Comparison of the predicted wind noise spectrum with the measured wind noise spectrum shows good agreement for four measurement sets. The prediction can be applied to meteorological estimates to predict the wind noise under other pine forests.
Peptidyl Aldehyde NK-1.8k Suppresses Enterovirus 71 and Enterovirus 68 Infection by Targeting Protease 3C
Authors: Wang Yaxin , Yang Ben , Zhai Yangyang , Yin Zheng , Sun Yuna , Rao Zihe
Published: February 2015

Enterovirus (EV) is one of the major causative agents of hand, foot, and mouth disease in the Pacific-Asia region. In particular, EV71 causes severe central nervous system infections, and the fatality rates from EV71 infection are high. Moreover, an outbreak of respiratory illnesses caused by an emerging EV, EV68, recently occurred among over 1,000 young children in the United States and was also associated with neurological infections. Although enterovirus has emerged as a considerable global public health threat, no antiviral drug for clinical use is available. In the present work, we screened our compound library for agents targeting viral protease and identified a peptidyl aldehyde, NK-1.8k, that inhibits the proliferation of different EV71 strains and one EV68 strain and that had a 50% effective concentration of 90 nM. Low cytotoxicity (50% cytotoxic concentration, >200 μM) indicated a high selective index of over 2,000. We further characterized a single amino acid substitution inside protease 3C (3C
pro
), N69S, which conferred EV71 resistance to NK-1.8k, possibly by increasing the flexibility of the substrate binding pocket of 3C
pro
. The combination of NK-1.8k and an EV71 RNA-dependent RNA polymerase inhibitor or entry inhibitor exhibited a strong synergistic anti-EV71 effect. Our findings suggest that NK-1.8k could potentially be developed for anti-EV therapy.
Antibiotic-Resistant Klebsiella pneumoniae and Escherichia coli High-Risk Clones and an IncFII
k
Mosaic Plasmid Hosting Tn
1
(
bla
TEM-4
) in Isolates from 1990 to 2004
Authors: Rodríguez Irene , Novais Ângela , Lira Felipe , Valverde Aránzazu , Curião Tânia , Martínez José Luis , Baquero Fernando , Cantón Rafael , Coque Teresa M.
Published: February 2015

We describe the genetic background of
bla
TEM-4
and the complete sequence of pRYC11::
bla
TEM-4
, a mosaic plasmid that is highly similar to pKpQIL-like variants, predominant among TEM-4 producers in a Spanish hospital (1990 to 2004), which belong to
Klebsiella pneumoniae
and
Escherichia coli
high-risk clones responsible for the current spread of different antibiotic resistance genes. Predominant populations of plasmids and host adapted clonal lineages seem to have greatly contributed to the spread of resistance to extended-spectrum cephalosporins.
Effects of Raltegravir or Elvitegravir Resistance Signature Mutations on the Barrier to Dolutegravir Resistance
In Vitro
Authors: Seki Takahiro , Suyama-Kagitani Akemi , Kawauchi-Miki Shinobu , Miki Shigeru , Wakasa-Morimoto Chiaki , Akihisa Erika , Nakahara Koichiro , Kobayashi Masanori , Underwood Mark R. , Sato Akihiko , Fujiwara Tamio , Yoshinaga Tomokazu
Published: February 2015

The recently approved HIV-1 integrase strand transfer inhibitor (INSTI) dolutegravir (DTG) (S/GSK1349572) has overall advantageous activity when tested
in vitro
against HIV-1 with raltegravir (RAL) and elvitegravir (EVG) resistance signature mutations. We conducted an
in vitro
resistance selection study using wild-type HIV-1 and mutants with the E92Q, Y143C, Y143R, Q148H, Q148K, Q148R, and N155H substitutions to assess the DTG
in vitro
barrier to resistance. No viral replication was observed at concentrations of ≥32 nM DTG, whereas viral replication was observed at 160 nM RAL or EVG in the mutants. In the Q148H, Q148K, or Q148R mutants, G140S/Q148H, E138K/Q148K, E138K/Q148R, and G140S/Q148R secondary mutations were identified with each INSTI and showed high resistance to RAL or EVG but limited resistance to DTG. E138K and G140S, as secondary substitutions to Q148H, Q148K, or Q148R, were associated with partial recovery in viral infectivity and/or INSTI resistance. In the E92Q, Y143C, Y143R, and N155H mutants, no secondary substitutions were associated with DTG. These
in vitro
results suggest that DTG has a high barrier to the development of resistance in the presence of RAL or EVG signature mutations other than Q148. One explanation for this high barrier to resistance is that no additional secondary substitution of E92Q, Y143C, Y143R, or N155H simultaneously increased the fold change in 50% effective concentration (EC
50
) to DTG and infectivity. Although increased DTG resistance via the Q148 pathway and secondary substitutions occurs at low concentrations, a higher starting concentration may reduce or eliminate the development of DTG resistance in this pathway
in vitro
.
Activity of Debio1452, a FabI Inhibitor with Potent Activity against Staphylococcus aureus and Coagulase-Negative Staphylococcus spp., Including Multidrug-Resistant Strains
Authors: Flamm Robert K. , Rhomberg Paul R. , Kaplan Nachum , Jones Ronald N. , Farrell David J.
Published: February 2015

Staphylococcus aureusand coagulase-negative staphylococci (CoNS) are responsible for a wide variety of human infections. The investigational antibacterial Debio1450 (previously AFN-1720), a prodrug of Debio1452 (previously AFN-1252), specifically targets staphylococci without significant activity against other Gram-positive or Gram-negative species. Debio1452 inhibits FabI, an enzyme critical to fatty acid biosynthesis in staphylococci. The activity of Debio1452 against CoNS, methicillin-susceptibleS. aureus(MSSA), and methicillin-resistantS. aureus(MRSA), including significant clones, was determined. A globally diverse collection of 574 patient isolates from 35 countries was tested that included CoNS (6 species, 103 strains), MSSA (154 strains), MRSA (163 strains), and molecularly characterized strains (includingspa-typed MRSA clones; 154 strains). The isolates were tested for susceptibility by CLSI broth microdilution methods against Debio1452 and 10 comparators. The susceptibility rates for the comparators were determined using CLSI and EUCAST breakpoint criteria. AllS. aureusand CoNS strains were inhibited by Debio1452 concentrations of ≤0.12 and ≤0.5 μg/ml, respectively. The MIC50s for MSSA, MRSA, and molecularly characterized MRSA strains were 0.004 μg/ml, and the MIC90s ranged from 0.008 to 0.03 μg/ml. The MICs were higher for the CoNS isolates (MIC50/90, 0.015/0.12 μg/ml). AmongS. aureusstrains, resistance was common for erythromycin (61.6%), levofloxacin (49.0%), clindamycin (27.6%), tetracycline (15.7%), and trimethoprim-sulfamethoxazole (7.0%). Debio1452 demonstrated potent activity against MSSA, MRSA, and CoNS. Debio1452 showed significantly greater activity overall (MIC50, 0.004 μg/ml) than the other agents tested against these staphylococcal species, which included dominant MRSA clones and strains resistant to currently utilized antimicrobial agents.
Proteomic-Based Approach To Gain Insight into Reprogramming of THP-1 Cells Exposed to Leishmania donovani over an Early Temporal Window
Authors: Singh Alok Kumar , Pandey Rajeev Kumar , Siqueira-Neto Jair Lage , Kwon Yong-Jun , Freitas-Junior Lucio H. , Shaha Chandrima , Madhubala Rentala
Published: February 2015

Leishmania donovani, a protozoan parasite, is the causative agent of visceral leishmaniasis. It lives and multiplies within the harsh environment of macrophages. In order to investigate how intracellular parasite manipulate the host cell environment, we undertook a quantitative proteomic study of human monocyte-derived macrophages (THP-1) following infection withL. donovani. We used the isobaric tags for relative and absolute quantification (iTRAQ) method and liquid chromatography-tandem mass spectrometry (LC-MS/MS) to compare expression profiles of noninfected andL. donovani-infected THP-1 cells. We detected modifications of protein expression in key metabolic pathways, including glycolysis and fatty acid oxidation, suggesting a global reprogramming of cell metabolism by the parasite. An increased abundance of proteins involved in gene transcription, RNA splicing (heterogeneous nuclear ribonucleoproteins [hnRNPs]), histones, and DNA repair and replication was observed at 24 h postinfection. Proteins involved in cell survival and signal transduction were more abundant at 24 h postinfection. Several of the differentially expressed proteins had not been previously implicated in response to the parasite, while the others support the previously identified proteins. Selected proteomics results were validated by real-time PCR and immunoblot analyses. Similar changes were observed inL. donovani-infected human monocyte-derived primary macrophages. The effect of RNA interference (RNAi)-mediated gene knockdown of proteins validated the relevance of the host quantitative proteomic screen. Our findings indicate that the host cell proteome is modulated afterL. donovaniinfection, provide evidence for global reprogramming of cell metabolism, and demonstrate the complex relations between the host and parasite at the molecular level.
Analysis of the Activity and Regulon of the Two-Component Regulatory System Composed by Cjj81176_1484 and Cjj81176_1483 of Campylobacter jejuni
Authors: Luethy Paul M. , Huynh Steven , Parker Craig T. , Hendrixson David R.
Published: February 2015

Campylobacter jejuniis a leading cause of bacterial diarrheal disease and a frequent commensal of the intestinal tract in poultry and other animals. For optimal growth and colonization of hosts,C. jejuniemploys two-component regulatory systems (TCSs) to monitor environmental conditions and promote proper expression of specific genes. We analyzed the potential ofC. jejuniCjj81176_1484(Cjj1484) andCjj81176_1483(Cjj1483) to encode proteins of a cognate TCS that influences expression of genes possibly important forC. jejunigrowth and colonization. Transcriptome analysis revealed that the regulons of the Cjj81176_1484 (Cjj1484) histidine kinase and the Cjj81176_1483 (Cjj1483) response regulator contain many common genes, suggesting that these proteins likely form a cognate TCS. We found that this TCS generally functions to repress expression of specific proteins with roles in metabolism, iron/heme acquisition, and respiration. Furthermore, the TCS repressed expression ofCjj81176_0438andCjj81176_0439, which had previously been found to encode a gluconate dehydrogenase complex required for commensal colonization of the chick intestinal tract. However, the TCS and other specific genes whose expression is repressed by the TCS were not required for colonization of chicks. We observed that the Cjj1483 response regulator binds target promoters in both unphosphorylated and phosphorylated forms and influences expression of some specific genes independently of the Cjj1484 histidine kinase. This work further expands the signaling mechanisms ofC. jejuniand provides additional insights regarding the complex and multifactorial regulation of many genes involved in basic metabolism, respiration, and nutrient acquisition that the bacterium requires for optimal growth in different environments.

IMPORTANCEBacterial two-component regulatory systems (TCSs) link environmental cues to expression of specific genes that enable optimal bacterial growth or colonization of hosts. We found that theCampylobacter jejuniCjj1484 histidine kinase and Cjj1483 response regulator function as a cognate TCS to largely repress expression of target genes encoding a gluconate dehydrogenase complex required for commensal colonization of the chick intestinal tract, as well as other genes encoding proteins for heme or iron acquisition, metabolism, and respiration. We also discovered different modes by which Cjj1483 may mediate repression with and without Cjj1484. This work provides insight into the signal transduction mechanisms of a leading cause of bacterial diarrheal disease and emphasizes the multifactorial and complex regulation of specific biological processes inC. jejuni.
Chromosome Organization and Replisome Dynamics in Mycobacterium smegmatis
Authors: Santi Isabella , McKinney John D.
Published: February 2015

Subcellular organization of the bacterial nucleoid and spatiotemporal dynamics of DNA replication and segregation have been studied intensively, but the functional link between these processes remains poorly understood. Here we use quantitative time-lapse fluorescence microscopy for single-cell analysis of chromosome organization and DNA replisome dynamics in
Mycobacterium smegmatis
. We report that DNA replication takes place near midcell, where, following assembly of the replisome on the replication origin, the left and right replication forks colocalize throughout the replication cycle. From its initial position near the cell pole, a fluorescently tagged chromosomal locus (
attB
, 245° from the origin) moves rapidly to the replisome complex just before it is replicated. The newly duplicated
attB
loci then segregate to mirror-symmetric positions relative to midcell. Genetic ablation of ParB, a component of the ParABS chromosome segregation system, causes marked defects in chromosome organization, condensation, and segregation. ParB deficiency also results in mislocalization of the DNA replication machinery and SMC (structural maintenance of chromosome) protein. These observations suggest that ParB and SMC play important and overlapping roles in chromosome organization and replisome dynamics in mycobacteria.

IMPORTANCE
We studied the spatiotemporal organization of the chromosome and DNA replication machinery in
Mycobacterium smegmatis
, a fast-growing relative of the human pathogen
Mycobacterium tuberculosis
. We show that genetic ablation of the DNA-binding proteins ParB and SMC disturbs the organization of the chromosome and causes a severe defect in subcellular localization and movement of the DNA replication complexes. These observations suggest that ParB and SMC provide a functional link between chromosome organization and DNA replication dynamics. This work also reveals important differences in the biological roles of the ParABS and SMC systems in mycobacteria versus better-characterized model organisms, such as
Escherichia coli
and
Bacillus subtilis
.