bluuebunny/crossref_metadata_2025 huggingface dataset:
In vivo measurements of muscle specific tension in adults and children
Authors: O’Brien Thomas D. , Reeves Neil D. , Baltzopoulos Vasilios , Jones David A. , Maganaris Constantinos N.
Published: September 2009

To better understand the effects of pubertal maturation on the contractile properties of skeletal muscle in vivo, the present study investigated whether there are any differences in the specific tension of the quadriceps muscle in 20 adults and 20 prepubertal children of both sexes. Specific tension was calculated as the ratio between the quadriceps tendon force and the sum of the physiological cross‐sectional area (PCSA) multiplied by the cosine of the angle of pennation of each head within the quadriceps muscle. The maximal quadriceps tendon force was calculated from the knee extension maximal voluntary contraction (MVC) by accounting for EMG‐based estimates of antagonist co‐activation, incomplete quadriceps activation using the interpolation twitch technique and magnetic resonance imaging (MRI)‐based measurements of the patellar tendon moment arm. The PCSA was calculated as the muscle volume, measured from MRI scans, divided by optimal fascicle length, measured from ultrasound images during MVC at the estimated angle of peak quadriceps muscle force. It was found that the quadriceps tendon force and PCSA of men (11.4 kN, 214 cm2) were significantly greater than those of the women (8.7 kN, 152 cm2; P < 0.01). Both adult groups had greater values than the children (P < 0.01) but there were no differences between boys (5.2 kN, 99 cm2) and girls (6.1 kN, 102 cm2). Agonist activation was greater in men and women than in girls (P < 0.05), and antagonist activation was greater in men than in boys (P < 0.05). Moment arm length was greater in men than in boys or girls and greater in women than in boys (P < 0.05). The angle of pennation did not differ between the groups in any of the quadriceps heads. The specific tension was similar (P > 0.05) between groups: men, 55 ± 11 N cm−2; women, 57.3 ± 13 N cm−2; boys, 54 ± 14 N cm−2; and girls, 59.8 ± 15 N cm−2. These findings indicate that the increased muscle strength with maturation is not due to an increase in the specific tension of muscle; instead, it can be attributed to increases in muscle size, moment arm length and voluntary activation level.
Relative proportions of hybrid fibres are unaffected by 6 weeks of running exercise in mouse skeletal muscles
Authors: Glaser Brian W. , You Geoffrey , Zhang Min , Medler Scott
Published: September 2009

Hybrid muscle fibres co‐expressing two or more myosin heavy chain (MHC) isoforms represent a significant proportion of fibres in many muscles, but the prevalence and precise composition of these fibres varies significantly among muscles and animal species. In the present study, we used a forced running protocol for 6 weeks to determine the effects of running exercise on the relative proportion of hybrid muscle fibre types in mouse muscles. In the course of this experiment, we also determined the relative proportions of these fibres in several different skeletal muscles, since data about hybrid fibres in the mouse are sparse. We found that the proportions of hybrid fibres in mouse muscles varied significantly among specific muscles (2–25%), but these proportions were unaffected by 6 weeks of forced running exercise. In contrast, weight‐bearing muscles significantly increased in mass in response to running. These data suggest that hybrid muscle fibres are relatively refractory to the effects of moderate exercise and represent a stable phenotype in normal mouse muscles. The precise nature and physiological function of these fibres remain incompletely understood, but it is clear that hybrid fibres represent a common phenotype in many muscles.
Exergy Analysis of the Sequestration of CO2 Emissions
Authors: Chavez Rosa-Hilda , Guadarrama Javier de J. , Hernandez-Guerrero Abel
Published: September 2009

Carbon dioxide capture from flue gas using amine-based CO2 capture technology requires huge amounts of energy mostly in the form of heat. The overall objective of this study is to evaluate the feasibility of obtaining the heat required for amine absorption for a particular recovery of carbon dioxide for a given a set of equipment specifications and operating conditions from the process and to develop a model that simulates the removal of CO2 using Monoethanolamine (MEA) absorption from flue gas and design a process that will minimize the energy of CO2 capture with Aspen Plus™ will be used. A very useful procedure for analyzing a process is by means of the Second Law of Thermodynamics. Thermodynamic analyses based on the concepts of irreversible entropy increase have frequently been suggested as pointers to sources of inefficiency in chemical processes.
A Surrogate Modeling Based Approach to Renewable Mobile Hybrid Power System Design
Authors: Murphy Jonathan , Ender Tommer , Mavris Dimitri , Haynes Comas
Published: September 2009

A surrogate modeling approach was developed and implemented for facilitating the design of renewable, hybrid power systems. A time-series hybrid power system simulation code (HOMER with supplement analysis) was replicated via readily executable neural network surrogate models. These surrogate models were subsequently integrated into a conceptual design engineering tool. The tool enables the rapid sizing and optimization of system components in the face of variable environmental conditions (i.e., renewable energy resources), economic conditions and weighted objectives. Accordingly, this tool was successfully used in the multi-objective design of a deployable hybrid renewable power system. This same capability can also be used to assess the feasibility of the requirements and constraints themselves, and potentially to guide the customer to appropriate design specifications.
Study on SOFC-MGT Hybrid Cycle System With High Efficiency
Authors: Duan Liqiang , He Binbin , Yang Yongping
Published: September 2009

From the viewpoint of intercrossing of thermodynamics and electrochemistry, SOFC-MGT hybrid cycle system has been studied in this paper. The key parameters that influence the system performance have been studied and optimized. The integration potential of improving the hybrid system performance by integrating SOFC with the advanced thermal cycle system is analyzed. The optimal rules of main parameters of SOFC/MGT hybrid system are revealed. The research results show that the turbine inlet temperature of MGT is an important parameter which limits the electrical efficiency of hybrid cycle systems. When the MGT system is taken as the design basis system of hybrid system, the lower the operating temperature of SOFC is, the higher the electrical efficiency of hybrid cycle systems is at the same maximum turbine entry temperature permitted, the more the needed cells are. As for the hybrid system with the fixed cell number, the operating temperature of SOFC can be enhanced as far as possible in order to get higher electrical efficiency, however, the high operating temperature will increase the turbine inlet temperature of MGT. Increasing of fuel utilization ratio is an effective way of improving the performance of hybrid cycle system; Increasing the ratio of steam to carbon is also a feasible measure which can reduce the turbine inlet temperature of MGT. In addition, with the increase of the operating pressure of cell stacks, the electrical efficiency of hybrid cycle systems will enhance obviously. The achievements obtained from this paper will provide valuable information for further study on SOFC-MGT hybrid system with high efficiency.
Performance Analysis and Design Optimization of a Mini-Channel Evacuated-Tube Solar Collector
Authors: Diaz Gerardo
Published: September 2009

The utilization of renewable energy sources is receiving considerable attention as a non-resource-depleting approach that reduces the emissions of pollutants and green-house gases to the atmosphere. Solar thermal systems have the capability to provide heat in a sustainable way for a variety of applications due to the relatively large range of temperatures that different collector configurations can attain. Most evacuated-tube solar collectors currently found on the market consist of a u-shaped round tube, concentric round tubes in counter flow regime, or a heat-pipe. The external surface in these designs is welded to a thin absorber fin that is covered with a selective coating. This paper analyzes the performance of an evacuated-tube solar collector that contains a U-shaped mini-channel tube. Comparisons of performance with respect to standard u-shaped round-tube solar collector are made. The design of a mini-channel based solar collector without absorber fin is also analyzed and its performance optimized with respect to its geometrical parameters.
Application of Thermoeconomic Analysis to the Evaluation of Potential Improvement for Energy Resources Saving in Process Plants
Authors: Verda Vittorio , Torres Ce´sar , Valero Antonio
Published: September 2009

The aim of the paper is to apply the thermoeconomic methodology to evaluate the cost of the energy resources saving that could be obtained by means of efficiency improvement in one or more components of the system and analyze its feasibility from an economical point of view. The paper is divided in two parts: In the first part the theoretical background is developed. A generalized expression of the fuel impact formula in monetary terms, which includes the formation and abatement cost of residuals or wastes, is obtained. The proposed formula is expressed as the net operating revenue (NOR) of the system improvement project. It takes advantage of the thermoeconomic isolation principle and decomposition to analyze the potential saving of each component instead the analysis of the overall system. In the second part, the proposed methodology is applied to a plant that integrates a waste-to-energy system with a gas combined cycle.
Study on Single- and Multi-Stage Adsorption Cooling Cycles Working at Sub and Above Atmospheric Conditions
Authors: Saha Bidyut B. , El-Sharkawy Ibrahim I. , Chakraborty Anutosh , Koyama Shigeru , Ng Kim Choon
Published: September 2009

This study deals with the performance analysis of single- and multi-stage adsorption cooling cycles working at partial vacuum and pressurized conditions for cooling applications. Four adsorbent-refrigerant pairs namely activated carbon fiber-ethanol, silica gel-water, Maxsorb II-R134a and Fluka-R134a pairs have been investigated. The former two pairs are deemed to be suitable for adsorption cycles working at pressures ranging from 1 to 11 kPa while the latter two are suitable for those working at above atmospheric pressure conditions typically between about 0.3 and 0.8 MPa. Invoking the adsorption isotherms of the assorted pairs, the pressure-temperature-concentration (P-T-W) diagrams have been presented. Pertaining a thermodynamic framework, the performance of both single- and multi-stage cycles in terms of specific cooling effect (SCE) and coefficient of performance (COP) has also been studied. Theoretical results show that the former two pairs i.e., the adsorption cycles working at partial vacuum pressures are suitable for surface cooling while latter two are suitable for micro cooling applications. Moreover, the multi-stage adsorption cycles can be operational at a heat source temperature below about 55°C, a region that could not be reached by any conventional adsorption cycle.
Multi-Objective Synthesis Optimization of Heat Exchanger Networks With Arbitrary Topology
Authors: Toffolo Andrea
Published: September 2009

The synthesis of heat exchanger networks (HENs) is one of the most studied problems in process synthesis, because a high level of integration of the internal heat transfer is necessary to reduce both primary energy consumption and total costs. This work develops a methodology for the multi-objective optimization of HEN synthesis. A two-level hybrid algorithm operating on a population of candidate HEN topologies is proposed to search for the best tradeoffs between the maximization of energy recovery and the minimization of total HEN costs. The advantages deriving from graph representations of a HEN are fully exploited in order to handle topologies with arbitrary complexity and to simplify the optimization procedure required to evaluate the objective functions for a given topology. The Aromatics Plant problem, a well-known test case in the literature about HEN synthesis, is used as a test case to show the potentialities of the proposed methodology.
Utilization of Expansion Work in Transcritical CO2 Heat Pumps in Combined Heating and Cooling
Authors: Stosic Nikola , Smith Ian K.
Published: September 2009

The use of CO2 as a refrigerant in transcritical vapour compression cycles has significant advantages, for systems which require simultaneous heating and cooling at approximately equal rates. However, then need for a compressor, to operate across high pressure differences, and the large throttle losses associated with these pressure differences have limited its use. This paper describes a study carried out to evaluate the efficiency gains and cost benefits possible from such a system when a twin screw machine is used to both compress and expand the working fluid in a single unit. It also shows the values of the critical design parameters required to optimise the system’s potential advantages when used in larger combined heating and cooling systems in industrial process and heat generation plants. The results show that recovery of work from the expansion process improves the COP by 15 to 20%. For the design conditions specified in this paper, this implies that the expander is worth fitting if it can be installed for a cost of less than approximately €750/kW of shaft power input. Thus, depending on the operating conditions, transcritical CO2 heat pumps using a compressor-expander can produce hot water at 90°C with a COP of approximately 6, with thermal outputs of up to 1.5 MW. This could be extended with simple control strategies up to outputs of 10 MW.
Constructing 3-D Wind Fields for Nellis Dunes in Nevada
Authors: Wang Xiuling , Pepper Darrell W. , Buck Brenda , Goossens Dirk
Published: September 2009

An h-adaptive, mass consistent finite element model (FEM) is used to construct 3-D wind fields over irregular terrain utilizing sparse meteorological tower data. The element size in the computational domain is dynamically controlled by a–posteriori error estimator based on the L2 norm. In the h-adaptive FEM algorithm, large element sizes are typically associated with computational regions where the flow is smooth and small errors; small element sizes are attributed to fast changing flow regions and large errors. The adaptive procedure uses mesh refinement/unrefinement to satisfy error criteria. The application of a mass consistent approach essentially poses a least-squares problem in the computational domain. Preliminary results are obtained for constructing 3-D wind fields for Nellis Dunes in Nevada.
Using Support Vector Regression in the Study of Product Form Images
Authors: Shieh Meng-Dar , Fang Hsin-En
Published: September 2009

In this paper, Support Vector Regression (SVR) training models using three different kernels: polynomial, Radial Basis Function (RBF), and mixed kernels, are constructed to demonstrate the training performance of unarranged data obtained from 32 virtual 3-D computer models. The 32 samples used as input data for training the three SVR models are represented by the coordination value sets of points extracted from 3-D models built by the 3-D software according to the shapes of 32 actual hairdryer products. To train the SVR model, an adjective (streamline) is used to evaluate all the 32 samples by 37 subjects. Then the scores of all the subjects are averaged to be the target values of the training models. In addition, a technique called k-fold cross-validation (C-V) is used to find the optimal parameter combination for optimizing the SVR models. The performance of the SVR using these three kernels to estimate the product image values is determined by the values of the Root Mean Square Error (RMSE). The results show that the optimal SVR model using the polynomial kernel performed better than the one using the RBF kernel. However, it is important to note that the mixed kernel had the best performance of the three. It is also shown in this study that the single RBF has a local characteristic and cannot process the broadly distributed data well. It can, however, be used to improve the power of the SVR by combining with the polynomial kernel.
Experimental Testing of a Thermoelectric-Based Hydronic Cooling and Heating Device With Transient Charging of Sensible Thermal Energy Storage Water Tank
Authors: Kazmierczak Michael J. , Krishnamoorthy Sreenidhi , Gupta Abhishek
Published: September 2009

Experiments were performed to charge either cold or hot water thermal energy storage tanks using a heat exchanger equipped with multiple thermoelectric (TE) modules. The primary objective was to design a simple, but effective, modular Peltier heat pump system component to provide chilled or hot water for domestic use at the appliance level, and when arranged in multiple unit combinations, a system that can potentially satisfy small home cooling and heating requirements. Moreover, when the TEs are directly energized using solar PV panels, the system provides a renewable, pollution free and off-the-grid solution to supplement home energy needs. The present work focuses on the design and testing of a thermoelectric heat exchanger component that consists of two water channels machined from two aluminum plates with an array of three or five thermoelectric modules placed in between to transiently cool and/or heat the water in the thermal energy storage tank. The water passing over either the cold or hot side of the TE modules is recirculated to charge the cold or hot thermal storage tank, respectively. The temperatures in the prototype Peltier heat exchanger test component and thermal energy water storage tank were measured during both cold tank charging and hot tank charging operation. The thermal efficiencies of TE heat pump cooling/heating system are reported. The effects of TE power input, number of TE units and rate of fluid flow are studied.
Structural and Thermal Design Challenges of Portable Micro Fuel Cell Systems
Authors: Minas Constantinos
Published: September 2009

Direct methanol fuel cell (DMFC) systems are currently being developed for portable electronic applications. A DMFC system that uses neat methanol with energy content of near 5 Whr/cc along with a compact fuel cell and compact auxiliaries can result in energy densities higher than the Li-Ion battery. An optimized fuel cell design along with a compact structural and thermal system design is thus essential, in order to simultaneously minimize the volume of the system and maximize its energy content. The portable fuel cell system performance over a range of environmental conditions is also essential for both consumer and military applications. An optimization was carried out in order to determine the fuel cell optimal operating conditions. A structural and thermal design of a portable micro fuel cell system was presented which addressed the aforementioned challenges. Nonlinear structural and thermal finite element analysis was carried out in order to develop the successful design.
Production and perception of French vowels by congenitally blind adults and sighted adults
Authors: Ménard Lucie , Dupont Sophie , Baum Shari R. , Aubin Jérôme
Published: September 2009

The goal of this study is to investigate the production and perception of French vowels by blind and sighted speakers. 12 blind adults and 12 sighted adults served as subjects. The auditory-perceptual abilities of each subject were evaluated by discrimination tests (AXB). At the production level, ten repetitions of the ten French oral vowels were recorded. Formant values and fundamental frequency values were extracted from the acoustic signal. Measures of contrasts between vowel categories were computed and compared for each feature (height, place of articulation, roundedness) and group (blind, sighted). The results reveal a significant effect of group (blind vs sighted) on production, with sighted speakers producing vowels that are spaced further apart in the vowel space than those of blind speakers. A group effect emerged for a subset of the perceptual contrasts examined, with blind speakers having higher peak discrimination scores than sighted speakers. Results suggest an important role of visual input in determining speech goals.
Bicylindrical model of Herschel–Quincke tube-duct system: Theory and comparison with experiment and finite element method
Authors: Poirier B. , Ville J. M. , Maury C. , Kateb D.
Published: September 2009

An analytical three dimensional bicylindrical model is developed in order to take into account the effects of the saddle-shaped area for the interface of a n-Herschel–Quincke tube system with the main duct. Results for the scattering matrix of this system deduced from this model are compared, in the plane wave frequency domain, versus experimental and numerical data and a one dimensional model with and without tube length correction. The results are performed with a two-Herschel–Quincke tube configuration having the same diameter as the main duct. In spite of strong assumptions on the acoustic continuity conditions at the interfaces, this model is shown to improve the nonperiodic amplitude variations and the frequency localization of the minima of the transmission and reflection coefficients with respect to one dimensional model with length correction and a three dimensional model.
Fast multipole boundary element method to calculate head-related transfer functions for a wide frequency range
Authors: Kreuzer Wolfgang , Majdak Piotr , Chen Zhengsheng
Published: September 2009

Head-related transfer functions (HRTFs) play an important role in spatial sound localization. The boundary element method (BEM) can be applied to calculate HRTFs from non-contact visual scans. Because of high computational complexity, HRTF simulations with BEM for the whole head and pinnae have only been performed for frequencies below 10kHz. In this study, the fast multipole method (FMM) is coupled with BEM to simulate HRTFs for a wide frequency range. The basic approach of the FMM and its implementation are described. A mesh with over 70 000 elements was used to calculate HRTFs for one subject. With this mesh, the method allowed to calculate HRTFs for frequencies up to 35kHz. Comparison to acoustically-measured HRTFs has been performed for frequencies up to 16kHz, showing a good congruence below 7kHz. Simulations with an additional shoulder mesh improved the congruence in the vertical direction. Reduction in the mesh size by 5% resulted in a substantially-worse representation of spectral cues. The effects of temperature and mesh perturbation were negligible. The FMM appears to be a promising approach for HRTF simulations. Further limitations and potential advantages of the FMM-coupled BEM are discussed.
Prediction of binaural speech intelligibility with frequency-dependent interaural phase differences
Authors: Beutelmann Rainer , Brand Thomas , Kollmeier Birger
Published: September 2009

The aim of this study was to test the hypothesis of independent processing strategies in adjacent binaural frequency bands underlying current models for binaural speech intelligibility in complex configurations and to investigate the effective binaural auditory bandwidth in broad-band signals. Speech reception thresholds (SRTs) were measured for binaural conditions with frequency-dependent interaural phase differences (IPDs) of speech and noise. SRT predictions with the binaural speech intelligibility model by Beutelmann and Brand (2006, J. Acoust. Soc. Am. 120, 331–342) were compared with the observed data. The IPDs of speech and noise had a sinusoidal shape on a logarithmic frequency scale. The bandwidth between zeros of the IPD function was varied from 1∕8 to 4 octaves. Speech and noise had either the same IPD function (reference condition) or opposite signs of the IPD function (binaural condition). Each condition had two subconditions with alternating and non-alternating signs, respectively, of the IPD function. The binaural unmasking with respect to the reference condition decreased from 6dB to zero with decreasing IPD bandwidth for the alternating condition while it stayed significantly larger than zero for the non-alternating condition. The observed results were well predicted by the model with an analysis filter bandwidth of 2.3 equivalent rectangular bandwidths (ERBs).
Critical ratios in harbor porpoises (Phocoena phocoena) for tonal signals between 0.315 and 150 kHz in random Gaussian white noise
Authors: Kastelein Ronald A. , Wensveen Paul J. , Hoek Lean , Au Whitlow W. L. , Terhune John M. , de Jong Christ A. F.
Published: September 2009

A psychoacoustic behavioral technique was used to determine the critical ratios (CRs) of two harbor porpoises for tonal signals with frequencies between 0.315 and 150 kHz, in random Gaussian white noise. The masked 50% detection hearing thresholds were measured using a “go/no-go” response paradigm and an up-down staircase psychometric method. CRs were determined at one masking noise level for each test frequency and were similar in both animals. For signals between 0.315 and 4 kHz, the CRs were relatively constant at around 18 dB. Between 4 and 150 kHz the CR increased gradually from 18 to 39 dB (∼3.3 dB/octave). Generally harbor porpoises can detect tonal signals in Gaussian white noise slightly better than most odontocetes tested so far. By combining the mean CRs found in the present study with the spectrum level of the background noise levels at sea, the basic audiogram, and the directivity index, the detection threshold levels of harbor porpoises for tonal signals in various sea states can be calculated.
Hydroacoustic measurements of the behavioral response of arctic riverine fishes to seismic airguns
Authors: Jorgenson John K. , Gyselman Eric C.
Published: September 2009

Seismic surveys for hydrocarbon exploration in the Mackenzie River involve the use of airguns. Airguns produce a repetitive, intense, low-frequency sound that has the potential to cause physiological damage and behavioral changes in fishes. Some of these impacts have been documented in marine environments but few studies have been conducted in freshwater systems where the confining nature of the environment produces a different acoustic regime and could constrain possible fish response. In the current study, hydroacoustic surveys are conducted in the presence of airgun firing in the Mackenzie River to determine if fish behavior can mitigate or enhance the potential impact of this sound. It is shown that fish behavioral characteristics measured in this study are generally not changed by the presence of airgun noise. The most likely mechanism to facilitate a severe physiological effect in fishes from a mobile airgun firing is a herding response in front of the airgun, resulting in prolonged exposure to the noise. Analysis of tracked fish directional movement does not indicate that herding behavior occurs. Consequently, no evidence is found to indicate that fishes in this study would sustain severe physiological damage from this airgun seismic survey.
Near field acoustic holography based on the equivalent source method and pressure-velocity transducers
Authors: Zhang Yong-Bin , Jacobsen Finn , Bi Chuan-Xing , Chen Xin-Zhao
Published: September 2009

The advantage of using the normal component of the particle velocity rather than the sound pressure in the hologram plane as the input of conventional spatial Fourier transform based near field acoustic holography (NAH) and also as the input of the statistically optimized variant of NAH has recently been demonstrated. This paper examines whether there might be a similar advantage in using the particle velocity as the input of NAH based on the equivalent source method (ESM). Error sensitivity considerations indicate that ESM-based NAH is less sensitive to measurement errors when it is based on particle velocity input data than when it is based on measurements of sound pressure data, and this is confirmed by a simulation study and by experimental results. A method that combines pressure- and particle velocity-based reconstructions in order to distinguish between contributions to the sound field generated by sources on the two sides of the hologram plane is also examined.
Speech production modifications produced in the presence of low-pass and high-pass filtered noise
Authors: Lu Youyi , Cooke Martin
Published: September 2009

In the presence of noise, do speakers actively shift their spectral energy distribution to regions least affected by the noise? The current study measured speech level, fundamental frequency, first formant frequency, and spectral center of gravity for read speech produced in the presence of low- and high-pass filtered noise. In both filtering conditions, these acoustic parameters increased relative to speech produced in quiet, a response which creates a release from masking for listeners in the low-pass condition but which actually increases masking in the high-pass noise condition. These results suggest that, at least for read speech, speakers do not adopt production strategies in noise which optimize listeners’ information reception but that instead the observed shifts could be a passive response which creates a fortuitous masking release in the low-pass noise. Independent variation in parameters such as F0, F1 and spectral center of gravity may be severely constrained by the increase in vocal effort which accompanies Lombard speech.
The kinetics and acoustics of fingering and note transitions on the flute
Authors: Almeida André , Chow Renee , Smith John , Wolfe Joe
Published: September 2009

Motion of the keys was measured in a transverse flute while beginner, amateur, and professional flutists played a range of exercises. The time taken for a key to open or close was typically 10 ms when pushed by a finger or 16 ms when moved by a spring. Because the opening and closing of keys will never be exactly simultaneous, transitions between notes that involve the movement of multiple fingers can occur via several possible pathways with different intermediate fingerings. A transition is classified as “safe” if it is possible to be slurred from the initial to final note with little perceptible change in pitch or volume. Some transitions are “unsafe” and possibly involve a transient change in pitch or a decrease in volume. Players, on average, used safe transitions more frequently than unsafe transitions. Delays between the motion of the fingers were typically tens of milliseconds, with longer delays as more fingers become involved. Professionals exhibited smaller average delays between the motion of their fingers than did amateurs.
Improvement of acoustic theory of ultrasonic waves in dilute bubbly liquids
Authors: Ando Keita , Colonius Tim , Brennen Christopher E.
Published: September 2009

The theory of the acoustics of dilute bubbly liquids is reviewed, and the dispersion relation is modified by including the effect of liquid compressibility on the natural frequency of the bubbles. The modified theory is shown to more accurately predict the trend in measured attenuation of ultrasonic waves. The model limitations associated with such high-frequency waves are discussed.
Uncertainty model for contact instability prediction
Authors: Culla Antonio , Massi Francesco
Published: September 2009

Contact between sliding bodies can cause vibrations leading to instability. The problem of squeal due to high frequency noise from brake systems is due to unstable vibrations generated at the contact interface between the pad and disk. Squeal noise is characterized by extreme unpredictability due to large uncertainties on the values of parameters of the system. Parametrical complex eigenvalue analysis is a common tool used to predict squeal instability. In this paper a substructured linear finite element model of a simplified brake system is studied. A parametrical analysis is focused on a test case and compared to experimental results. The analysis is developed as a function of the parameters assumed to be the most influential but also the most uncertain: friction coefficient and the parameters driving the dynamics of the system. The uncertainties are accounted for by considering parameters such as random variables. A Monte Carlo simulation and a probabilistic technique are performed simultaneously to study the probability of squeal occurrence. Finally, a reduced model based on the transfer function calculated at the contact is developed to perform the analysis with reduced computational effort.
47-channel burst-mode recording hydrophone system enabling measurements of the dynamic echolocation behavior of free-swimming dolphins
Authors: Starkhammar Josefin , Amundin Mats , Nilsson Johan , Jansson Tomas , Kuczaj Stan A. , Almqvist Monica , Persson Hans W.
Published: September 2009

Detailed echolocation behavior studies on free-swimming dolphins require a measurement system that incorporates multiple hydrophones (often >16). However, the high data flow rate of previous systems has limited their usefulness since only minute long recordings have been manageable. To address this problem, this report describes a 47-channel burst-mode recording hydrophone system that enables highly resolved full beamwidth measurements on multiple free-swimming dolphins during prolonged recording periods. The system facilitates a wide range of biosonar studies since it eliminates the need to restrict the movement of animals in order to study the fine details of their sonar beams.
Patch near-field acoustic holography: Regularized extension and statistically optimized methods
Authors: Pascal Jean-Claude , Paillasseur Sébastien , Thomas Jean-Hugh , Li Jing-Fang
Published: September 2009

The patch holography method allows one to make measurements on an extended structure using a small microphone array. Increased attention has been paid to the two techniques, which are quite different at first glance. One is to extrapolate the pressure field measured on the hologram plane while the other is to use statistically optimized processing. A singular value decomposition formulation of the latter is proposed in this paper. The similarity of the two techniques is shown here. Both use a convolution of the measured pressure patch to obtain a better estimate of the wavenumber spectrum backward propagated on the structure. By using the Morozov discrepancy principle to compute the regularization parameter, the two methods lead to very close results.
Statistical Assessment of Variability of Terminal Restriction Fragment Length Polymorphism Analysis Applied to Complex Microbial Communities
Authors: Rossi Pierre , Gillet François , Rohrbach Emmanuelle , Diaby Nouhou , Holliger Christof
Published: September 2009

The variability of terminal restriction fragment polymorphism analysis applied to complex microbial communities was assessed statistically. Recent technological improvements were implemented in the successive steps of the procedure, resulting in a standardized procedure which provided a high level of reproducibility.
Diverse Enterotoxin Gene Profiles among Clonal Complexes of
Staphylococcus aureus
Isolates from the Bronx, New York
Authors: Varshney Avanish K. , Mediavilla José R. , Robiou Natalie , Guh Alice , Wang Xiabo , Gialanella Philip , Levi Michael H. , Kreiswirth Barry N. , Fries Bettina C.
Published: September 2009

Staphylococcal
enterotoxins (SE) can cause toxin-mediated disease, and those that function as superantigens are implicated in the pathogenesis of allergic diseases. The prevalence of 19 enterotoxin genes was determined by PCR in clinical
S. aureus
strains derived from wounds (108) and blood (99). We performed
spa
typing and multilocus sequence typing (MLST) to determine clonal origin, and for selected strains staphylococcal enterotoxin B (SEB) production was measured by enzyme-linked immunosorbent assay. Strains carried a median of five SE genes. For most SE genes, the prevalence rates among methicillin-resistant and methicillin-sensitive
S. aureus
isolates, as well as wound- and blood-derived isolates, did not differ. At least one SE gene was detected in all except two
S. aureus
isolates (>99%). Complete
egc
clusters were found in only 11% of
S. aureus
isolates, whereas the combination of
sed
,
sej
, and
ser
was detected in 24% of clinical strains.
S. aureus
strains exhibited distinct combinations of SE genes, even if their pulsed-field gel electrophoresis and MLST patterns demonstrated clonality. USA300 strains also showed considerable variability in SE content, although they contained a lower number of SE genes (mean, 3). By contrast, SE content was unchanged in five pairs of serial isolates. SEB production by individual strains varied up to 200-fold, and even up to 15-fold in a pair of serial isolates. In conclusion, our results illustrate the genetic diversity of
S. aureus
strains with respect to enterotoxin genes and suggest that horizontal transfer of mobile genetic elements encoding virulence genes occurs frequently.
Pathotype and Antibiotic Resistance Gene Distributions of
Escherichia coli
Isolates from Broiler Chickens Raised on Antimicrobial-Supplemented Diets
Authors: Bonnet Claudie , Diarrassouba Fatoumata , Brousseau Roland , Masson Luke , Topp Edward , Diarra Moussa S.
Published: September 2009

The impact of feed supplementation with bambermycin, monensin, narasin, virginiamycin, chlortetracycline, penicillin, salinomycin, and bacitracin on the distribution of
Escherichia coli
pathotypes in broiler chickens was investigated using an
E. coli
virulence DNA microarray. Among 256
E. coli
isolates examined, 59 (23%) were classified as potentially extraintestinal pathogenic
E. coli
(ExPEC), while 197 (77%) were considered commensal. Except for chlortetracycline treatment, the pathotype distribution was not significantly different among treatments (
P
> 0.05). Within the 59 ExPEC isolates, 44 (75%) were determined to be potentially avian pathogenic
E. coli
(APEC), with the remaining 15 (25%) considered potentially “other” ExPEC isolates. The distribution within phylogenetic groups showed that 52 (88%) of the ExPEC isolates belonged to groups B2 and D, with the majority of APEC isolates classified as group D and most commensal isolates (170, 86%) as group A or B1. Indirect assessment of the presence of the virulence plasmid pAPEC-O2-ColV showed a strong association of the plasmid with APEC isolates. Among the 256 isolates, 224 (88%) possessed at least one antimicrobial resistance gene, with nearly half (107, 42%) showing multiple resistance genes. The majority of resistance genes were distributed among commensal isolates. Considering that the simultaneous detection of antimicrobial resistance
tet
(A),
sulI
, and
bla
TEM
genes and the integron class I indicated a potential presence of the resistance pAPEC-O2-R plasmid, the results revealed that 35 (14%) of the isolates, all commensals, possessed this multigene resistance plasmid. The virulence plasmid was never found in combination with the antimicrobial resistance plasmid. The presence of the ColV plasmid or the combination of
iss
and
tsh
genes in the majority of APEC isolates supports the notion that when found together, the plasmid,
iss
, and
tsh
serve as good markers for APEC. These data indicate that different resistant
E. coli
pathotypes can be found in broiler chickens and that the distribution of such pathotypes and certain virulence determinants could be modulated by antimicrobial agent feed supplementation.
Cryptosporidium
Propidium Monoazide-PCR, a Molecular Biology-Based Technique for Genotyping of Viable
Cryptosporidium
Oocysts
Authors: Brescia Cristin C. , Griffin Shannon M. , Ware Michael W. , Varughese Eunice A. , Egorov Andrey I. , Villegas Eric N.
Published: September 2009

Cryptosporidium
is an important waterborne protozoan parasite that can cause severe diarrhea and death in the immunocompromised. The current methods used to monitor for
Cryptosporidium
oocysts in water are the microscopy-based USEPA methods 1622 and 1623. These methods assess total levels of oocysts in source waters, but do not determine oocyst viability or genotype. Recently, propidium monoazide (PMA) has been used in conjunction with molecular diagnostic tools to identify species and assess the viability of bacteria. The goal of this study was the development of a
Cryptosporidium
PMA-PCR (CryptoPMA-PCR) assay that includes PMA treatment prior to PCR analysis in order to prevent the amplification of DNA from dead oocysts. The results demonstrated that PMA penetrates only dead oocysts and blocks amplification of their DNA. The CryptoPMA-PCR assay can also specifically detect live oocysts within a mixed population of live and dead oocysts. More importantly, live oocysts, not dead oocysts, were detected in raw waste or surface water samples spiked with
Cryptosporidium
oocysts. This proof-of-concept study is the first to demonstrate the use of PMA for pre-PCR treatment of
Cryptosporidium
oocysts. The CryptoPMA-PCR assay is an attractive approach to specifically detect and genotype viable
Cryptosporidium
oocysts in the water, which is critical for human health risk assessment.
Effect of Cinnamon Oil on
icaA
Expression and Biofilm Formation by
Staphylococcus epidermidis
Authors: Nuryastuti Titik , van der Mei Henny C. , Busscher Henk J. , Iravati Susi , Aman Abu T. , Krom Bastiaan P.
Published: September 2009

Staphylococcus epidermidis
is notorious for its biofilm formation on medical devices, and novel approaches to prevent and kill
S. epidermidis
biofilms are desired. In this study, the effect of cinnamon oil on planktonic and biofilm cultures of clinical
S. epidermidis
isolates was evaluated. Initially, susceptibility to cinnamon oil in planktonic cultures was compared to the commonly used antimicrobial agents chlorhexidine, triclosan, and gentamicin. The MIC of cinnamon oil, defined as the lowest concentration able to inhibit visible microbial growth, and the minimal bactericidal concentration, the lowest concentration required to kill 99.9% of the bacteria, were determined using the broth microdilution method and plating on agar. A checkerboard assay was used to evaluate the possible synergy between cinnamon oil and the other antimicrobial agents. The effect of cinnamon oil on biofilm growth was studied in 96-well plates and with confocal laser-scanning microscopy (CLSM). Biofilm susceptibility was determined using a metabolic 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Real-time PCR analysis was performed to determine the effect of sub-MIC concentrations of cinnamon oil on expression of the biofilm-related gene,
icaA
. Cinnamon oil showed antimicrobial activity against both planktonic and biofilm cultures of clinical
S. epidermidis
strains. There was only a small difference between planktonic and biofilm MICs, ranging from 0.5 to 1% and 1 to 2%, respectively. CLSM images indicated that cinnamon oil is able to detach and kill existing biofilms. Thus, cinnamon oil is an effective antimicrobial agent to combat
S. epidermidis
biofilms.
Insufficiency of Copper Ion Homeostasis Causes Freeze-Thaw Injury of Yeast Cells as Revealed by Indirect Gene Expression Analysis
Authors: Takahashi Shunsuke , Ando Akira , Takagi Hiroshi , Shima Jun
Published: September 2009

Saccharomyces cerevisiae
is exposed to freeze-thaw stress in commercial processes, including frozen dough baking. Cell viability and fermentation activity after a freeze-thaw cycle were dramatically decreased due to freeze-thaw injury. Because this type of injury involves complex phenomena, the injury mechanisms are not fully understood. We examined freeze-thaw injury by indirect gene expression analysis during postthaw incubation after freeze-thaw treatment using DNA microarray profiling. The results showed that genes involved in the homeostasis of metal ions were frequently contained in genes that were upregulated, depending on the freezing period. We assessed the phenotype of deletion mutants of the metal ion homeostasis genes that exhibited freezing period-dependent upregulation and found that the strains with deletion of the
MAC1
and
CTR1
genes involved in copper ion homeostasis exhibited freeze-thaw sensitivity, suggesting that copper ion homeostasis is required for freeze-thaw tolerance. We found that supplementation with copper ions during postthaw incubation increased intracellular superoxide dismutase activity and intracellular levels of reactive oxygen species were decreased. Moreover, cell viability was increased by supplementation with copper ions. These results suggest that insufficiency of copper ion homeostasis may be one of the causes of freeze-thaw injury.
Dominant Bacteria and Biomass in the Kuytun 51 Glacier
Authors: Xiang Shu-Rong , Shang Tian-Cui , Chen Yong , Jing Ze-Fan , Yao Tandong
Published: September 2009

Dominant bacteria in the different habitats in the Kuytun 51 Glacier were investigated using a 16S rRNA gene clone library sequencing technique. Results showed diverse bacteria on the glacial surface, with the dominant phyla being
Proteobacteria
,
Cyanobacteria
, and
Bacteroidetes.
UniFrac data showed distinct community patterns between the Kuytun and Himalayan Rongbuk glaciers.
Engineering of
Bacillus subtilis
168 for Increased Nisin Resistance
Authors: Hansen Mette E. , Wangari Romilda , Hansen Egon B. , Mijakovic Ivan , Jensen Peter R.
Published: September 2009

Nisin is a natural bacteriocin produced commercially by
Lactococcus lactis
and widely used in the food industry as a preservative because of its broad host spectrum. Despite the low productivity and troublesome fermentation of
L. lactis
, no alternative cost-effective host has yet been found.
Bacillus subtilis
had been suggested as a potential host for the biosynthesis of nisin but was discarded due to its sensitivity to the lethal action of nisin. In this study, we have reevaluated the potential of
B. subtilis
as a host organism for the heterologous production of nisin. We applied transcriptome and proteome analyses of
B. subtilis
and identified eight genes upregulated in the presence of nisin. We demonstrated that the overexpression of some of these genes boosts the natural defenses of
B. subtilis
, which allows it to sustain higher levels of nisin in the medium. We also attempted to overcome the nisin sensitivity of
B. subtilis
by introducing the nisin resistance genes
nisFEG
and
nisI
from
L. lactis
under the control of a synthetic promoter library.
Correlation of Methane Production and Functional Gene Transcriptional Activity in a Peat Soil
Authors: Freitag Thomas E. , Prosser James I.
Published: September 2009

The transcription dynamics of subunit A of the key gene in methanogenesis (methyl coenzyme M reductase;
mcrA
) was studied to evaluate the relationship between process rate (methanogenesis) and gene transcription dynamics in a peat soil ecosystem. Soil methanogen process rates were determined during incubation of peat slurries at temperatures from 4 to 37°C, and real-time quantitative PCR was applied to quantify the abundances of
mcrA
genes and transcripts; corresponding transcriptional dynamics were calculated from
mcrA
transcript/gene ratios. Internal standards suggested unbiased recovery of mRNA abundances in comparison to DNA levels. In comparison to those in pure-culture studies,
mcrA
transcript/gene ratios indicated underestimation by 1 order of magnitude, possibly due to high proportions of inactive or dead methanogens. Methane production rates were temperature dependent, with maxima at 25°C, but changes in abundance and transcription of the
mcrA
gene showed no correlation with temperature. However,
mcrA
transcript/gene ratios correlated weakly (regression coefficient = 0.76) with rates of methanogenesis. Methanogen process rates increased over 3 orders of magnitude, while the corresponding maximum transcript/gene ratio increase was only 18-fold.
mcrA
transcript dynamics suggested steady-state expression in peat soil after incubation for 24 and 48 h, similar to that in stationary-phase cultures.
mcrA
transcript/gene ratios are therefore potential in situ indicators of methanogen process rate changes in complex soil systems.