bluuebunny/crossref_metadata_2025 huggingface dataset:
Active Noise Control to Reduce the Blade Tone Noise of Centrifugal Fans
Authors: Koopmann G. H. , Neise W. , Chen W.
Published: December 2011

This paper describes an active noise control method to suppress the blade tones of centrifugal fans. Two secondary sound sources are mounted into the cutoff region of the fan casing. These sources are driven with electrical signals that are synchronized with the rotation of the impeller, and their amplitudes and phase are adjusted to give maximum reduction for the blade tone levels in the inlet and outlet duct of the fan. With this design, the sound emitted by the secondary sources is introduced into the interior of the casing near the source region where the blade tone is generated, i.e., the cutoff. The present experiments were concentrated on the reduction of the fundamental of the blade tone for centrifugal fan with impeller diameters between 280 mm (11 in.) and 710 mm (28 in.). Two different designs of secondary sources were investigated. In the first, two loudspeakers are contained within an enclosure which has an open end made of a curved perforated plate which replaces part of the original cutoff. The second design incorporates two vibrating plates which replace portions of the outlet duct side and the volute side of the cutoff. Reductions in tone sound pressure level of up to 23 dB have been observed for a variety of aerodynamic loading conditions and fan inlet geometries. To obtain a better understanding of the physical mechanism of this active noise control method, sound pressure measurements were also made on the inner surface of the fan casing along the volute. Both amplitude and phase of the blade passing frequency component were measured relative to a reference signal derived from the impeller rotation. The result of this experiment is that the sound field inside the casing is dominated by the pressure pattern rotating together with the impeller. Since the impeller tip Mach number is well below sonic speed, however, the radiation efficiency of the rotating pressures is very low. The blade tone noise measured in the far-field is generated by the unsteady pressures at the cutoff which in turn are produced by the flow leaving the impeller. This aerodynamic noise generating mechanism is modified by the active sources located in the cutoff.
Structural Modification of Advanced Turbomachine Blading by Dynamic Stiffness Matrix Operations
Authors: Jones D. I. G. , Muszynska A.
Published: December 2011

This paper examines the application of matrix transformations from the experimentally obtained receptance matrix to the dynamic stiffness matrix to determine changes of blade stiffness and/or mass characteristics which will achieve desired modifications of blade dynamic behavior. Results for a specific turbine blade configuration are used to illustrate the approach.
High Amplitude Sound Propagation at Low Frequencies in a Flow Duct Lined With Resonators: A Time Domain Solution
Authors: Cummings A. , Chang I.-J.
Published: December 2011

A quasi one-dimensional analysis of sound transmission in a flow duct lined with an array of nonlinear resonators is described. The solution to the equations describing the sound field and the hydrodynamic flow in the neighborhood of the resonator orifices is performed numerically in the time domain, with the object of properly accounting for the nonlinear interaction between the acoustic field and the resonators. Experimental data are compared to numerical computations in the time domain and generally very good agreement is noted. The method described here may readily be extended for use in the design of exhaust mufflers for internal combustion engines.
Acoustic Agglomeration of Power Plant Fly Ash for Environmental and Hot Gas Clean-up
Authors: Reethof G.
Published: December 2011

Acoustic agglomeration of power plant fly ash is an intermediate treatment of the flue gases to increase the size of the small micron (1–5) and submicron (0.1–1) particulates to large micron sizes (5–10) so that the conventional particle removal devices such as bag houses, electrostatic precipitators, and scrubbers can operate more efficiently. This paper provides a brief history of the topic, introduces some of the fundamental issues and gives some recent results of analytical models of the processes. The experimental facility is briefly described and some analytical results are shown which compare well with the experimental results. Most important of all, the paper shows that acoustic agglomeration is a technically and potentially economically viable method to improve air pollution control.
A Model of Categorization for Use in Automated Failure Analysis
Authors: Morrill J. P. , Wright D.
Published: December 2011

Categorization is the procedure of determining set membership based on either necessary or statistically suggestive conditions for membership. This procedure lies at the heart of automated metallurgical failure analysis, controlling the accuracy of the final conclusion. This article examines the tradeoff between the number of questions posed by the computer during data collection and the certainty of the final decision. After a brief overview of failure analysis decision making, a model of categorization is proposed which is derived from Bayes’ theorem that asks questions in order of relevance and stops when an adequate level of certainty is achieved. This eliminates irrelevant questions without significantly compromising the accuracy of the final conclusion. The model has been implemented as part of an artificial intelligence computer program.
Experimental Characterization of Noise Sources for Duct Acoustics
Authors: Doige A. G. , Alves H. S.
Published: December 2011

Many industrial applications involving the acoustics of ducting or piping systems require an improved description of noise sources, so that a better prediction and evaluation of system performance can be achieved. Some examples are (a) the computer simulation of intake and exhaust muffler performance, (b) the control of pressure pulsation in fluid piping systems due to control valve flow noise or reciprocating compressors, and (c) predicting pressure fluctuations in heating and air-conditioning system ductwork due to various types of fans or blowers. This paper describes two applications of a well-known linear electrical analogy for obtaining experimentally the internal acoustical source impedance and the strength of the source, both parameters which are independent of the acoustic system load impedance. Two methods are compared, one which utilizes direct measurement of source impedance with the source inactive, and a two-load method from which the source impedance is calculated from measured pressures, with the source in operation. Various applications are presented using a speaker, compressor, engine, and centrifugal fan as noise sources connected to different load impedances. Comparisons are made to highlight the relative merits of these two approaches and to demonstrate the degree of accuracy that can be obtained in predicting noise levels in any arbitrary linear acoustic system, using the measured source parameters. The methods are simple in concept and in application, and while they do not often describe the physical nature of noise sources, they do offer a way to bypass the much more difficult problem of modelling the source theoretically.
Seismic Induced Nonlinear Rotor-Bearing-Casing Interaction of Rotating Nuclear Components
Authors: Choy F. K. , Padovan J. , Li W. H.
Published: December 2011

The study of the dynamics of turbomachinery during seismic events has been of continuous interest to both researchers and designers of large rotating equipment. Failure in such equipment, especially those associated with nuclear power generation, can lead to catastrophic consequences. Hence, there is a general trend for corporations to “overdesign” the equipment without any indepth understanding of the dynamical performance of the machine under extreme operating conditions. The overall objectives of this paper are fourfold, namely: (1) To study the nonlinear dynamics of rotor-bearing casing system during rub interactions; (2) To examine the effects of suddenly induced imbalance and base motion in the global dynamical behavior of the system: (3) To develop engineering insights through the modal parameters in both time and frequency domain; (4) To generate signature analysis on rub forces for pattern recognition. These goals are achieved through the development of a modal impact model. Accuracy and efficiency of this transient model are maintained using a self-adaptive integration scheme. A numerical FFT scheme is applied to examine the modal participations, bearing forces, and rub signatures in the frequency domain. A typical nuclear water pump will be used as an example for this approach.
Improvement of a Reduced Torsional Model by Means of Parameter Identification
Authors: Schwibinger P. , Nordmann R.
Published: December 2011

Turbogenerator sets in operation may be excited to transient torsional vibrations by dynamic electrical moments at the generator due to short-circuits or faulty synchronization. For the solution of the torsional vibration problem it is essential to find an appropriate torsional model of the original system. A common approach is to model the torsional system finely by the finite element method which normally results in a very accurate mechanical model with many degrees of freedom (DOF). However for some applications it is desirable to have a torsional model with a reduced number of DOF which reproduces the original system exactly only in the lower eigenfrequencies and modes. This paper describes a method which allows finding a most accurate reduced torsional model with discrete masses and springs from a finite element model with many DOF. The results for the eigenfrequencies, the modes, and internal moments due to a short-circuit excitation of a 600 MW turbogenerator set are presented. They are compared with other reduction methods.
Analysis of a High-Speed Flexible Four-Bar Linkage: Part II—Analytical and Experimental Results on the Apollo
Authors: Liou F. W. , Erdman A. G.
Published: December 2011

By using the equations of motion derived from the virtual displacement [1], a general finite element analysis computer code FEMAP (Four-bar Elastic Mechanism Analysis Program) for the planar motion is developed on the Apollo computer. The output of this program includes the following analysis for any point in the mechanism: velocity, acceleration, natural frequency, displacement, stress and strain. The displacement, stress and strain can be either quasi-static or full vibration analysis. The animation of the entire motion of the flexible linkage can be displayed on the screen. Analytical results are compared with results from a new experimental method which combines high-speed photography with a digital image processing technique.
A Design Criterion for Avoiding Resonance in Lumped Mass Normal Mode Systems
Authors: Ross A. D. S. , Inman D. J.
Published: December 2011

A simple design criterion that determines whether a normal mode multiple degree of freedom damped linear lumped parameter system can or cannot resonate is presented. The relations are derived based on criteria for resonance in the single degree of freedom case, and on the definiteness of certain combinations of coefficient matrices. An example follows that both numerically verifies the derivation and illustrates the simplicity of implementing the result as a design criterion.
Active Control of Impact Vibration Using Feedforward Control Method
Authors: Tanaka N. , Kikushima Y.
Published: December 2011

For the purpose of developing a vibrationless forge hammer, this paper presents a principle of the vibrationless forge method based upon an active vibration control technique. Then, from a viewpoint of feedforward control method, the vibrationless forge system is analyzed, and state equations of the system are derived. Next, with a view to simulating the vibrationless forge system using an analog computer, a signal wave of an impact force actually taken in a hammering test is employed as an input to the analog computer. Moreover, the control effect for suppressing the impact vibration is discussed. Finally, in order to obtain a perspective to realize the vibrationless forge hammer, an experiment is carried out, and the effectiveness of the vibrationless forge method is verified.
Passive Diagnostics and Reliability Experiment: Application in Machine Condition Monitoring
Authors: Cempel C.
Published: December 2011

For many critical machines the only source of diagnostic knowledge is passive experiment during machine operation. If we treat the observed vibration symptoms for a group of machines as an outcome of the Weibull type stochastic process we can calculate the average symptom life-curve and the alarm and break-down ratio. These appear to be dependent on the Weibull shape factor (existing machine quality) and maintenance parameters used at a given plant. The results of passive experiment shown in the paper confirm fully the paper’s theoretical consideration.
Fluid-Structure Interaction Forces at Pump-Impeller-Shroud Surfaces for Rotordynamic Calculations
Authors: Childs D. W.
Published: December 2011

Governing equations of motion are derived for a bulk-flow model of the leakage path between an impeller shroud and a pump housing. The governing equations consist of a path-momentum, a circumferential-momentum, and a continuity equation. The fluid annulus between the impeller shroud and pump housing is assumed to be circumferentially symmetric when the impeller is centered; i.e., the clearance can vary along the pump axis but does not vary in the circumferential direction. A perturbation expansion of the governing equations in the eccentricity ratio yields a set of zeroth and first-order governing equations. The zeroth-order equations define the leakage rate and the circumferential and path velocity distributions and pressure distributions for a centered impeller position. The first-order equations define the perturbations in the velocity and pressure distributions due to either a radial-displacement perturbation or a tilt perturbation of the impeller. Integration of the perturbed pressure and shear-stress distribution acting on the rotor yields the reaction forces and moments acting on the impeller face. Calculated results yield predictions of possible resonance peaks of the fluid within the annulus formed by the impeller shroud and housing. Centrifugal acceleration terms in the path-momentum equation are the physical origin of these unexpected predictions. For normalized tangential velocities at the inlet to the annulus, uθ0(0) = Uθ0(0)/Riω of 0.5, the phenomenon is relatively minor. As uθ0(0) is increased to 0.7, sharp peaks are predicted. Comparisons for rotordynamic coefficient predictions with test results of Bolleter et al. show reasonable agreement for cross-coupled stiffness and direct damping terms. Calculated results are provided which make comparisons between seal forces and shroud forces for a typical impeller/wear-ring-seal combination.
Development of an On-Line Rotor Crack Detection and Monitoring System
Authors: Imam I. , Azzaro S. H. , Bankert R. J. , Scheibel J.
Published: December 2011

A very comprehensive technology of on-line rotor crack detection and monitoring has been developed. The technique, based on the vibration signature analysis (VSA) approach, can detect incipient transverse rotor cracks in an “on-line mode.” The technique is generic and is applicable to all machines whose rotors are subjected to some kind of bending load. These machines include turbines, generators, pumps and motors, etc. The technique is based on the analytical modeling of the dynamics of the system. The basic idea is that through the modeling approach, the crack symptoms can be determined in terms of characteristic vibration signatures. These signatures are then used to diagnose the flaw in real life situations. A 3-D finite element crack model and a nonlinear rotor dynamic code have also been developed to accurately model a cracked rotor system. This program has been used to develop a variety of unique vibration signatures indicating a rotor crack. Both the analytical crack model and the crack signature analysis techniques have been experimentally validated. A microprocessor-based on-line rotor crack detection and monitoring system has been developed. The system has successfully detected cracks of the order of 1 to 2 percent of shaft diameter deep in an “on-line” mode in a series of large-scale laboratory tests. The system has been installed on a turbine-generator set at a utility in the field in October 1986 and has since been operating continuously, both in on-line as well as in coast-down modes, essentially, flawlessly. The system has also been applied in a crack detection program for nuclear reactor vertical coolant pumps. This paper describes all aspects of the development, starting from the technical concept to the commercial field applications.
Piezoelectric Pushers for Active Vibration Control of Rotating Machinery
Authors: Palazzolo A. B. , Lin R. R. , Alexander R. M. , Kascak A. F. , Montague J.
Published: December 2011

The active control of rotordynamic vibrations and stability by magnetic bearings and electromagnetic shakers has been discussed extensively in the literature. These devices, though effective, are usually large in volume and add significant weight to the stator. The use of piezoelectric pushers may provide similar degrees of effectiveness in light, compact packages. This paper contains analyses which extend quadratic regulator and derivative feedback control methods to the “prescribed displacement” character of piezoelectric pushers. The structrual stiffness of the pusher is also included in the theory. Tests are currently being conducted at NASA Lewis Research Center with piezoelectric pusher-based active vibration control. The paper presents results performed on the NASA test rig as preliminary verification of the related theory.
Development of a Centrifugal Pendulum Absorber for Reducing Ship Superstructure Vibration
Authors: Yoshida Y.
Published: December 2011

A vibration absorber (designated as the Super Dynamic Damper) for installation on ship superstructures, based on a tuned centrifugal pendulum concept, was developed through theoretical analyses followed by tests on units mounted on a vibrating platform and on actual ships. The tests confirmed the analytically estimated performance, and demonstrated that the vibrating amplitude would be reduced, to limit it to a constant low level independent of imparted exciting force. Results of analysis indicate the most important quality demanded of a tuned absorber to be the tuning accuracy. The tolerance permissible for the tuning accuracy is determined by the mass ratio: A smaller mass ratio calls for correspondingly higher tuning accuracy. The centrifugal pendulums are governed by Coulomb damping, which results in a damping behavior distinct from normal viscous damping. Both analysis and measurements attested to the importance of accurately controlling the absorber rotating speed, short of which the absorber risked becoming a vibration amplifier.
Hot-Stretching Effects on Thermally Loaded Rotors
Authors: Elbella A. , Seireg A.
Published: December 2011

This paper presents a simplified computer-based algorithm which can be used to study the beneficial effects of hot-stretching on thermally loaded rotors. The procedure is applicable to rotors with variable thickness and can be used to determine the optimum hot-stretching parameters as well as the optimum profile of the disk for any given thermal and mechanical loading condition.
Stress Concentration Factors in Angled Flexural Members of Rectangular Cross-Section
Authors: Siddiqui F. M. A. , Beseler J. W.
Published: December 2011

The results of stress analysis of angled members subjected to pure flexure are presented. The stress analysis was performed using the ANSYS finite element program. Stress concentration factors varying from 1.25 to 2.5 can be expected at the reentrant corner of the member depending on the ratio of the fillet radius to the width and the deviating angle.
Computer-Aided Design of Power Transmission Shafts Subject to Size, Strength, and Deflection Constraints Using a Nonlinear Programming Technique
Authors: Umasankar G. , Mischke C. R.
Published: December 2011

The problem of synthesis of power transmission shafts supported on two bearings, subject to dimensional, strength, and deflection constraints is posed as a nonlinear programming (NP) problem. The formulation of the design problem and its solution using the gradient projection (GP) algorithm are presented. A computer program for shaft design against a user-definable weight/cost criterion, based on the formulation and solution presented, is made available. A design example illustrating this approach to power transmission shaft design is included.
A Complex Modal Analysis Method for Damped Vibration Systems (The Representation in the Second Order Differential Form of a Modal Equation and its Use for Practical Application)
Authors: Inoue Y. , Fujikawa T.
Published: December 2011

Second order uncoupled differential equations for the general damped vibration systems are derived theoretically. The equations are written in a form similar to the classical real modal equations by using the natural frequency, the modal damping ratio, and the newly defined complex modal mass. Introducing supplementary variables, the response analysis is carried out in a similar manner to the real modal analysis. By comparing these equations to the classical ones, physical meanings of the derived equations are clarified. For the vibration problems near the resonant point, approximate complex modal equations are derived which have almost the same form as the classical one. Some applications of the proposed method to vibration problems are discussed.
Active Damping in a Three-Axis Robotic Manipulator
Authors: Meckl P. , Seering W.
Published: December 2011

This paper explores several methods to eliminate residual vibration of a robot arm at the end of a move, using open-loop control. The robot structure is modeled as lumped masses and springs with negligible damping, representative of a three-axis Cartesian manipulator. Vibration control is achieved using two different types of forcing functions: (1) a “bang-bang” control function for time-optimal response, and (2) a function constructed to avoid exciting resonance throughout the move. These functions are then compared in their ability to attenuate residual vibration in practice and the response time using (2) is compared with the optimal time using (1).
Signal Processing Criteria and Statistical Error Analysis for Acoustic Measurements in Duct Systems
Authors: Seybert A. F.
Published: December 2011

A one-dimensional acoustic theory for random sound fields is presented. The theory is applied to the description of a random sound field in a tube of finite length terminated at the source and passive ends by arbitrary acoustical impedances. The theory is used to illustrate the spatial and spectral features of the acoustic field. These features are in many respects analogous to the well-known characteristics of a pure-tone sound field in a duct. However, the formulation in terms of a random sound field permits a more general investigation of measurement error than is possible using the pure-tone analysis. For example, it is shown that the familiar standing wave measurement problem is complicated by the presence of bias errors introduced by signal processing requirements.
Forced Convection Heat Transfer Using High Temperature and Pressure Water in an Upward-Inclined Tube
Authors: Gang Wu , Bi Qincheng , Wang Han , Yang Zhendong , Zhu Xiaojing , Hu Zhihong
Published: December 2011

Within the range of pressure from 9 to 28 MPa, mass flux from 600 to 1500 kg/m2s, heat flux at inside wall from 200 to 600 kW/m2, and wall temperature up to 650 °C, experiments were conducted to research the forced convection heat transfer of water in an inclined upward tube with an inclination angle of 20 deg and an inner diameter of 26 mm. According to the experimental data, the effects of pressure and heat flux on heat transfer of water were analyzed in detail. In the subcritical pressure region, it was found that heat transfer characteristics of water are not uniform along the circumference of the inclined tube. Temperature of the top is always higher than that of the bottom, which can be attributed to the buoyancy effect in the inclined tube. In the supercritical pressure region, natural convection makes the low-density hot fluid gather at the top of the inclined tube; hence, heat transfer condition is deteriorated and wall temperature is increased. Furthermore, the criterions of Petukhov and Jackson were selected to judge the buoyancy effect in the inclined upward tube. The result seems acceptable but these criterions should be further improved to get a better applicability for an inclined tube.
Elastic Stability of a Cantilever Beam (Rod) Supported by an Elastic Foundation, With Application to Nano-Composites
Authors: Suhir E.
Published: December 2011

A simple analytical (“mathematical”) predictive model is developed with an objective to establish the condition of elastic stability for a compressed cantilever beam (rod) of finite length lying on a continuous elastic foundation. Based on the developed model, practical guidelines are provided for choosing the adequate length of the beam and/or its flexural rigidity and/or the spring constant of the foundation, so that the beam remains elastically stable. The obtained solution can be used, perhaps with some additional assumptions and modifications, for the assessment of the critical force for high-modulus and low-expansion fibers (including nano-fibers) embedded into a low-modulus and high-expansion medium (matrix). Composite systems are often fabricated at elevated temperatures and operated at lower temperature conditions. It is imperative that an embedded fiber remains elastically stable, i.e., does not buckle as a result of the thermal contraction mismatch of its material with the material of the matrix. If buckling occurs, the functional (e.g., thermal) and/or the structural (“physical”) performance of the composite might be compromised.
Investigation of the factors determining the SIMS depth resolution in silicon-isotope multiple layers
Authors: Tomita M. , Koike M. , Akutsu H. , Takeno S. , Kawamura Y. , Shimizu Y. , Uematsu M. , Itoh K. M.
Published: December 2011

In order to identify their controlling factors, the depth resolution parameters for secondary ion mass spectrometry, which include the decay length and the standard deviation of the Gaussian function (also referred to as the depth resolution function), for silicon atoms in a silicon matrix with silicon-isotope multiple layers were investigated under oxygen (O2+) and cesium (Cs+) ion bombardments with a wide ion energy range (from 200 eV to 10 keV) and with several incident angles. The use of silicon-isotope multiple layers in this investigation eliminated the chemical segregation effect caused by the sample composition. Measures were also taken to prevent ripple formation on the sputtered sample surface. The obtained depth resolution parameters were proportional to E1/2cos θ, where E is the primary ion energy per atom and θ is the incident angle relative to the surface normal. The relationships for decay length and standard deviation were different for the Cs+ ion, the O2+ ion with full oxidization, and the O2+ ion without full oxidization. The damage depth was measured by high-resolution Rutherford backscattering spectrometry and it was found that the relationships of the standard deviation versus damage depth depend only on the damage depth with a small dependence on the ion species (O2+/Cs+). The degree of mixing near the sputtered surface of thin silicon-isotope multiple layers bombarded by O2+/Cs+ ions was measured using laser-assisted atom probe analysis, and the relationship of the degree of mixing with the depth resolution parameters indicated that the decay length was degraded according to the degree of mixing. Atomic mixing/sputtering simulations revealed the factors determining the depth resolution parameters for secondary ion mass spectrometry. The standard deviation is found to be mainly degraded by the damage depth, which agrees with the results obtained by Rutherford backscattering spectrometry, whereas the decay length is mainly extended by the variance of the damage density profile, which is a parameter of the Gaussian function and governs the degree of mixing near the surface.
Phonemic restoration effect reversed in a reverberant room
Authors: Srinivasan Nirmal Kumar , Zahorik Pavel
Published: December 2011

Classic demonstrations of the phonemic restoration effect show increased intelligibility of interrupted speech when the interruptions are caused by a plausible masking sound rather than by silent periods. Previous studies of this effect have been conducted exclusively under anechoic or nearly anechoic listening conditions. This study demonstrates that the effect is reversed when sounds are presented in a realistically simulated reverberant room (broadband T60 = 1.1 s): intelligibility is greater for silent interruptions than for interruptions by unmodulated noise. Additional results suggest that the reversal is primarily due to filling silent intervals with reverberant energy from the speech signal.
Pharmacodynamics of TD-1792, a Novel Glycopeptide-Cephalosporin Heterodimer Antibiotic Used against Gram-Positive Bacteria, in a Neutropenic Murine Thigh Model
Authors: Hegde Sharath S. , Okusanya Olanrewaju O. , Skinner Robert , Shaw Jeng-Pyng , Obedencio Glenmar , Ambrose Paul G. , Blais Johanne , Bhavnani Sujata M.
Published: December 2011

TD-1792 is a novel glycopeptide-cephalosporin heterodimer investigational antibiotic that displays potent bactericidal effects against clinically relevant Gram-positive organisms
in vitro
. The present studies evaluated the
in vivo
pharmacokinetics (PK) and pharmacodynamics (PD) of TD-1792 in the neutropenic murine thigh infection animal model. TD-1792, dosed subcutaneously (SC), produced dose-dependent reduction in the thigh bacterial burden of several organisms, including methicillin-susceptible and -resistant strains of
Staphylococcus aureus
and
Staphylococcus epidermidis
(MSSA, MRSA, MSSE, MRSE, respectively), penicillin-susceptible strains of
Streptococcus pneumoniae
(PSSP),
Streptococcus pyogenes
, and vancomycin-intermediate-susceptible
Staphylococcus aureus
(VISA). In single-dose efficacy studies, the 1-log
10
CFU kill effective dose (ED
1-log kill
) estimates for TD-1792 ranged from 0.049 to 2.55 mg/kg of body weight administered SC, and the bacterial burden was reduced by up to 3 log
10
CFU/g from pretreatment values. Against
S. aureus
ATCC 33591 (MRSA), the total 24-h log
10
stasis dose (ED
stasis
) and ED
1-logkill
doses for TD-1792 were 0.53 and 1.11 mg/kg/24 h, respectively, compared to 23.4 and 54.6 mg/kg/24 h for vancomycin, indicating that TD-1762 is 44- to 49-fold more potent than vancomycin. PK-PD analysis of data from single-dose and dose-fractionation studies for MRSA (ATCC 33591) demonstrated that the total-drug 24-h area under the concentration-time curve-to-MIC ratio (AUC/MIC ratio) was the best predictor of efficacy (
r
2
= 0.826) compared to total-drug maximum plasma concentration of drug-to-MIC ratio (Cmax/MIC ratio;
r
2
= 0.715) and percent time that the total-drug plasma drug concentration remains above the MIC (%Time>MIC;
r
2
= 0.749). The magnitudes of the total-drug AUC/MIC ratios associated with net bacterial stasis, a 1-log
10
CFU reduction from baseline and near maximal effect, were 21.1, 37.2, and 51.8, respectively. PK-PD targets based on such data represent useful inputs for analyses to support dose selection decisions for clinical studies of patients.
Decrease of Antibiotic Consumption in Children with Upper Respiratory Tract Infections after Implementation of an Intervention Program in Cyprus
Authors: Papaevangelou V. , Rousounides A. , Hadjipanagis A. , Katsioulis A. , Theodoridou M. , Hadjichristodoulou C.
Published: December 2011

To assess the impact of intervention on antibiotic misuse in children, parents' and pediatricians' knowledge, attitudes, and practices (KAP) concerning antibiotic use were evaluated pre- and postintervention in Larnaca (Cyprus) and Limassol (Cyprus). Concurrently, pediatricians documented upper respiratory tract infection (URTI) visits and pharmacists provided antibiotic consumption data. Intervention was implemented for parents and pediatricians residing in Larnaca. The consumption/URTI incidence index was significantly reduced in Larnaca but not in Limassol. Parental responses to a KAP questionnaire remained unchanged; therefore, antibiotic consumption reduction is attributable to pediatricians' education.
Impact of Feed Efficiency and Diet on Adaptive Variations in the Bacterial Community in the Rumen Fluid of Cattle
Authors: Hernandez-Sanabria Emma , Goonewardene Laksiri A. , Wang Zhiquan , Durunna Obioha N. , Moore Stephen S. , Guan Le Luo
Published: December 2011

Limited knowledge of the structure and activities of the ruminal bacterial community prevents the understanding of the effect of population dynamics on functional bacterial groups and on host productivity. This study aimed to identify particular bacteria associated with host feed efficiency in steers with differing diets and residual feed intake (RFI) using culture-independent methods: PCR-denaturing gradient gel electrophoresis (DGGE) and quantitative real-time PCR analysis. PCR-DGGE profiles were generated from the ruminal fluid of 55 steers fed a low-energy-density diet and then switched to a high-energy-density diet. Bacterial profile comparisons by multivariate statistical analysis showed a trend only for RFI-related clusters on the high-energy diet. When steers (
n
= 19) belonging to the same RFI group under both diets were used to identify specific bacterial phylotypes related to feed efficiency traits, correlations were detected between dry matter intake, average daily gain, and copy numbers of the 16S rRNA gene of
Succinivibrio
sp. in low-RFI (efficient) steers, whereas correlations between
Robinsoniella
sp. and RFI (
P
< 0.05) were observed for high-RFI (inefficient) animals.
Eubacterium
sp. differed significantly (
P
< 0.05) between RFI groups that were only on the high-energy diet. Our work provides a comprehensive framework to understand how particular bacterial phylotypes contribute to differences in feed efficiency and ultimately influence host productivity, which may either depend on or be independent from diet factors.
Functional Characterization of Crp/Fnr-Type Global Transcriptional Regulators in Desulfovibrio vulgaris Hildenborough
Authors: Zhou Aifen , Chen Yunyu I. , Zane Grant M. , He Zhili , Hemme Christopher L. , Joachimiak Marcin P. , Baumohl Jason K. , He Qiang , Fields Matthew W. , Arkin Adam P. , Wall Judy D. , Hazen Terry C. , Zhou Jizhong
Published: December 2011

Crp/Fnr-type global transcriptional regulators regulate various metabolic pathways in bacteria and typically function in response to environmental changes. However, little is known about the function of four annotated Crp/Fnr homologs (DVU0379, DVU2097, DVU2547, and DVU3111) inDesulfovibrio vulgarisHildenborough. A systematic study using bioinformatic, transcriptomic, genetic, and physiological approaches was conducted to characterize their roles in stress responses. Similar growth phenotypes were observed for thecrp/fnrdeletion mutants under multiple stress conditions. Nevertheless, the idea of distinct functions of Crp/Fnr-type regulators in stress responses was supported by phylogeny, gene transcription changes, fitness changes, and physiological differences. The fourD. vulgarisCrp/Fnr homologs are localized in three subfamilies (HcpR, CooA, andcc). Thecrp/fnrknockout mutants were well separated by transcriptional profiling using detrended correspondence analysis (DCA), and more genes significantly changed in expression in a ΔDVU3111 mutant (JW9013) than in the other three paralogs. In fitness studies, strain JW9013 showed the lowest fitness under standard growth conditions (i.e., sulfate reduction) and the highest fitness under NaCl or chromate stress conditions; better fitness was observed for a ΔDVU2547 mutant (JW9011) under nitrite stress conditions and a ΔDVU2097 mutant (JW9009) under air stress conditions. A higher Cr(VI) reduction rate was observed for strain JW9013 in experiments with washed cells. These results suggested that the four Crp/Fnr-type global regulators play distinct roles in stress responses ofD. vulgaris. DVU3111 is implicated in responses to NaCl and chromate stresses, DVU2547 in nitrite stress responses, and DVU2097 in air stress responses.
Discovering Novel Bile Protection Systems in Bifidobacterium breve UCC2003 through Functional Genomics
Authors: Ruiz Lorena , Zomer Aldert , O'Connell-Motherway Mary , van Sinderen Douwe , Margolles Abelardo
Published: December 2011

Tolerance of gut commensals to bile salt exposure is an important feature for their survival in and colonization of the intestinal environment. A transcriptomic approach was employed to study the response of
Bifidobacterium breve
UCC2003 to bile, allowing the identification of a number of bile-induced genes with a range of predicted functions. The potential roles of a selection of these bile-inducible genes in bile protection were analyzed following heterologous expression in
Lactococcus lactis
. Genes encoding three transport systems belonging to the major facilitator superfamily (MFS), Bbr_0838, Bbr_0832, and Bbr_1756, and three ABC-type transporters, Bbr_0406-0407, Bbr_1804-1805, and Bbr_1826-1827, were thus investigated and shown to provide enhanced resistance and survival to bile exposure. This work significantly improves our understanding as to how bifidobacteria respond to and survive bile exposure.
Effect of
Rj
Genotype and Cultivation Temperature on the Community Structure of Soybean-Nodulating Bradyrhizobia
Authors: Shiro Sokichi , Yamamoto Akihiro , Umehara Yosuke , Hayashi Masaki , Yoshida Naoto , Nishiwaki Aya , Yamakawa Takeo , Saeki Yuichi
Published: December 2011

The nodulation tendency and community structure of indigenous bradyrhizobia on
Rj
genotype soybean cultivars at cultivation temperatures of 33/28°C, 28/23°C, and 23/18°C for 16/8 h (day/night degrees, hours) were investigated using 780 bradyrhizobial DNA samples from an Andosol with 13 soybean cultivars of four
Rj
genotypes (non-
Rj
,
Rj
2
Rj
3
,
Rj
4
, and
Rj
2
Rj
3
Rj
4
). A dendrogram was constructed based on restriction fragment length polymorphism of the PCR products (PCR-RFLP) of the 16S-23S rRNA gene internal transcribed spacer region. Eleven
Bradyrhizobium
U.S. Department of Agriculture strains were used as a reference. The dendrogram indicated seven clusters based on similarities among the reference strains. The occupancy rate of the Bj123 cluster decreased with increasing cultivation temperature, whereas the occupancy rates of the Bj110 cluster, Be76 cluster, and Be94 cluster increased with increasing cultivation temperature. In particular, the
Rj
2
Rj
3
Rj
4
genotype soybeans were infected with a number of Bj110 clusters, regardless of the increasing cultivation temperature, compared to other
Rj
genotype soybean cultivars. The ratio of beta diversity to gamma diversity (
H′
β
/
H′
γ
), which represents differences in the bradyrhizobial communities by pairwise comparison among cultivation temperature sets within the same soybean cultivar, indicated that the bradyrhizobial communities tended to be different among cultivation temperatures. Multidimensional scaling analysis indicated that the infection of the Bj110 cluster and the Bj123 cluster by host soybean genotype and the cultivation temperature affected the bradyrhizobial communities. These results suggested that the
Rj
genotypes and cultivation temperatures affected the nodulation tendency and community structures of soybean-nodulating bradyrhizobia.
Molecular and Histological Characterization of Primary (Betaproteobacteria) and Secondary (Gammaproteobacteria) Endosymbionts of Three Mealybug Species
Authors: Gatehouse Laurence N. , Sutherland Paul , Forgie Shaun A. , Kaji Ryohei , Christeller John T.
Published: December 2011

Microscopic localization of endosymbiotic bacteria in three species of mealybug (
Pseudococcus longispinus
, the long-tailed mealybug;
Pseudococcus calceolariae
, the citrophilus mealybug; and
Pseudococcus viburni
, the obscure mealybug) showed these organisms were confined to bacteriocyte cells within a bacteriome centrally located within the hemocoel. Two species of bacteria were present, with the secondary endosymbiont, in all cases, living within the primary endosymbiont. DNA from the dissected bacteriomes of all three species of mealybug was extracted for analysis. Sequence data from selected 16S rRNA genes confirmed identification of the primary endosymbiont as “
Candidatus
Tremblaya princeps,” a betaproteobacterium, and the secondary endosymbionts as gammaproteobacteria closely related to
Sodalis glossinidius
. A single 16S rRNA sequence of the primary endosymbiont was found in all individuals of each mealybug species. In contrast, the presence of multiple divergent strains of secondary endosymbionts in each individual mealybug suggests different evolutionary and transmission histories of the two endosymbionts. Mealybugs are known vectors of the plant pathogen
Grapevine leafroll-associated virus 3
. To examine the possible role of either endosymbiont in virus transmission, an extension of the model for interaction of proteins with bacterial chaperonins, i.e., GroEL protein homologs, based on mobile-loop amino acid sequences of their GroES homologs, was developed and used for analyses of viral coat protein interactions. The data from this model are consistent with a role for the primary endosymbiont in mealybug transmission of
Grapevine leafroll-associated virus 3
.
Potential Probiotic Kluyveromyces marxianus B0399 Modulates the Immune Response in Caco-2 Cells and Peripheral Blood Mononuclear Cells and Impacts the Human Gut Microbiota in an
In Vitro
Colonic Model System
Authors: Maccaferri Simone , Klinder Annett , Brigidi Patrizia , Cavina Piero , Costabile Adele
Published: December 2011

Considering the increase in the consumption of yeasts as human probiotics, the aim of this study was to broadly investigate the beneficial properties of the lactic yeast
Kluyveromyces marxianus
(formerly
Kluyveromyces fragilis
) B0399. Several potential probiotic traits of
K. marxianus
B0399 were investigated by using
in vitro
assays, including adhesion and immune modulation, and the effect of the administration of 10
7
CFU/day of
K. marxianus
B0399 on the composition and metabolic activity of the human intestinal microbiota was investigated in a 3-stage continuous-culture system simulating the human colon. We demonstrated that this strain was highly adhesive to human enterocyte-like Caco-2 cells and modulated the immune response, inducing proinflammatory cytokines in peripheral blood mononuclear cells (PBMCs). In the presence of inflammatory stimulation with lipopolysaccharide (LPS),
K. marxianus
B0399 provoked decreases in the levels of production of proinflammatory cytokines in PBMCs and Caco-2 cells, thus ameliorating the inflammatory response. Furthermore,
K. marxianus
B0399 impacted the colonic microbiota, increasing the bifidobacterial concentration in the stages of the colonic model system simulating the proximal and transverse colon. The amounts of the short-chain fatty acids acetate and propionate also increased following yeast supplementation. Finally,
K. marxianus
B0399 was found to induce a decrease of the cytotoxic potential of the culture supernatant from the first stage of the colonic model system. The effects of
K. marxianus
B0399 on adhesion, immune function, and colonic microbiota demonstrate that this strain possesses a number of beneficial and strain-specific properties desirable for a microorganism considered for application as a probiotic.
Effects of Temperature, Relative Humidity, Absolute Humidity, and Evaporation Potential on Survival of Airborne Gumboro Vaccine Virus
Authors: Zhao Yang , Aarnink Andre J. A. , Dijkman Remco , Fabri Teun , de Jong Mart C. M. , Groot Koerkamp Peter W. G.
Published: December 2011

Survival of airborne virus influences the extent of disease transmission via air. How environmental factors affect viral survival is not fully understood. We investigated the survival of a vaccine strain of Gumboro virus which was aerosolized at three temperatures (10°C, 20°C, and 30°C) and two relative humidities (RHs) (40% and 70%). The response of viral survival to four metrics (temperature, RH, absolute humidity [AH], and evaporation potential [EP]) was examined. The results show a biphasic viral survival at 10°C and 20°C, i.e., a rapid initial inactivation in a short period (2.3 min) during and after aerosolization, followed by a slow secondary inactivation during a 20-min period after aerosolization. The initial decays of aerosolized virus at 10°C (1.68 to 3.03 ln % min
−1
) and 20°C (3.05 to 3.62 ln % min
−1
) were significantly lower than those at 30°C (5.67 to 5.96 ln % min
−1
). The secondary decays at 10°C (0.03 to 0.09 ln % min
−1
) tended to be higher than those at 20°C (−0.01 to 0.01 ln % min
−1
). The initial viral survival responded to temperature and RH and potentially to EP; the secondary viral survival responded to temperature and potentially to RH. In both phases, survival of the virus was not significantly affected by AH. These findings suggest that long-distance transmission of airborne virus is more likely to occur at 20°C than at 10°C or 30°C and that current Gumboro vaccination by wet aerosolization in poultry industry is not very effective due to the fast initial decay.
Interaction Forces Drive the Environmental Transmission of Pathogenic Protozoa
Authors: Dumètre Aurélien , Aubert Dominique , Puech Pierre-Henri , Hohweyer Jeanne , Azas Nadine , Villena Isabelle
Published: December 2011

The protozoan parasites
Giardia duodenalis
,
Cryptosporidium
spp., and
Toxoplasma gondii
are pathogens that are resistant to a number of environmental factors and pose significant risks to public health worldwide. Their environmental transmission is closely governed by the physicochemical properties of their cysts (
Giardia
) and oocysts (
Cryptosporidium
and
Toxoplasma
), allowing their transport, retention, and survival for months in water, soil, vegetables, and mollusks, which are the main reservoirs for human infection. Importantly, the cyst/oocyst wall plays a key role in that regard by exhibiting a complex polymeric coverage that determines the charge and hydrophobic characteristics of parasites' surfaces. Interaction forces between parasites and other environmental particles may be, in a first approximation, evaluated following the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory of colloidal stability. However, due to the molecular topography and nano- to microstructure of the cyst/oocyst surface, non-DVLO hydrophobic forces together with additional steric attractive and/or repulsive forces may play a pivotal role in controlling the parasite behavior when the organism is subjected to various external conditions. Here, we review several parameters that enhance or hinder the adhesion of parasites to other particles and surfaces and address the role of fast-emerging techniques for mapping the cyst/oocyst surface, e.g., by measuring its topology and the generated interaction forces at the nano- to microscale. We discuss why characterizing these interactions could be a crucial step for managing the environmental matrices at risk of microbial pollution.
Characterization of
bla
CMY-2
Plasmids in Salmonella and Escherichia coli Isolates from Food Animals in Canada
Authors: Martin Laura C. , Weir Emily K. , Poppe Cornelis , Reid-Smith Richard J. , Boerlin Patrick
Published: December 2011

One hundred thirty-four
bla
CMY-2
plasmids from
Salmonella
and
Escherichia coli
strains from animals and food in Canada were characterized. Five plasmid groups were identified based on replicon type and restriction profiles. Three groups contained
E. coli
plasmids only. IncA/C plasmids included most multiresistant plasmids and all those of bovine origin.