bluuebunny/crossref_metadata_2025 huggingface dataset:
Key Parameters for the Performance of Impaction-Pin Nozzles Used in
Inlet Fogging of Gas Turbine Engines
Authors: Chaker Mustapha A.
Published: March 2007

The application of inlet air fogging to gas turbine engines for power augmentation has become common practice, with more than 1000 installations worldwide, including a large number of advanced gas turbines. In this paper an experimental investigation and empirical analysis of key operating parameters on the performance of impaction pin nozzles will be investigated. To date, no such correlation is available for impaction pin nozzles, which are currently used in about 75% of this type of applications. The correlations are developed from a series of experiments conducted in a wind tunnel equipped with the Malvern Spraytec droplet size measurement system. The conducted analysis covered a wide range of the relevant parameters. Mainly, the water flow rate from the nozzle orifice was (0.00126 to 0.00063 ls−1: 0.02 gpm to 0.1 gpm), the operating pressure was (34.5 to 204.1 bars: 500 to 3000 psi), the airflow velocity was (1.5 to 15.2 ms−1: 295 to 3000 fpm), the distance between the nozzle orifice and the location of measurement was (0.0127 to 0.508 m: 0.5 to 20 in.). Other parameters such as the plume spray cone angle and the surrounding ambient psychrometric conditions, which may affect the droplet size for impaction pin nozzles, is also discussed.
Investigation of Entropy Noise in Aero-Engine Combustors
Authors: Bake Friedrich , Michel Ulf , Roehle Ingo
Published: March 2007

Strong evidence is presented that entropy noise is the major source of external noise in aero-engine combustion. Entropy noise is generated in the outlet nozzles of combustors. Low-frequency entropy noise, which was predicted earlier in theory and numerical simulations, was successfully detected in a generic aero-engine combustion chamber. It is shown that entropy noise dominates even in the case of thermo-acoustic resonances. In addition to this, a different noise generating mechanism was discovered that is presumably of even higher relevance to jet engines: There is strong evidence of broad band entropy noise at higher frequencies (1 to 3kHz in the reported tests). This unexpected effect can be explained by the interaction of small scale entropy perturbations (hot spots) with the strong pressure gradient in the outlet nozzle. The direct combustion noise of the flame zone seems to be of minor importance for the noise emission to the ambiance. The combustion experiments were supplemented by experiments with electrical heating. Two different methods for generating entropy waves were used, a pulse excitation and a sinusoidal excitation. In addition, high-frequency entropy noise was generated by steady electrical heating.
Automatic Optimization of Preswirl Nozzle Design
Authors: Ciampoli Fabio , Chew John W. , Shahpar Shahrokh , Willocq Elisabeth
Published: March 2007

The objective of the research described here is to develop and demonstrate use of automatic design methods for preswirl nozzles. Performance of preswirled cooling air delivery systems depends critically on the design of these nozzles which is subject to manufacturing and stress constraints. The best solution may be a compromise between cost and performance. Here it is shown that automatic optimization using computational fluid dynamics (CFD) to evaluate nozzle performance can be useful in design. A parametric geometric model of a nozzle with appropriate constraints is first defined and the CFD meshing and solution are then automated. The mesh generation is found to be the most delicate task in the whole process. Direct hill climbing (DHC) and response surface model (RSM) optimization methods have been evaluated. For the test case considered, significant nozzle performance improvements were obtained using both methods, but the RSM model was preferred.
Numerical Simulations of Isothermal Flow in a Swirl Burner
Authors: García-Villalba M. , Fröhlich J. , Rodi W.
Published: March 2007

In this paper, the non-reacting flow in a swirl burner is studied using large eddy simulation. The configuration consists of two unconfined coannular jets at a Reynolds number of 81,500. The flow is characterized by a Swirl number of 0.93. Two cases are studied in the paper differing with respect to the axial location of the inner pilot jet. It was observed in a companion experiment (Bender and Büchner, 2005, Proc. 12 Int. Cong. Sound and Vibration, Lisbon, Portugal) that when the inner jet is retracted the flow oscillations are considerably amplified. This is also found in the present simulations. Large-scale coherent structures rotating at a constant rate are observed when the inner jet is retracted. The rotation of the structures leads to vigorous oscillations in the velocity and pressure time signals recorded at selected points in the flow. In addition, the mean velocities, the turbulent fluctuations, and the frequency of the oscillations are in good agreement with the experiments. A conditional averaging procedure is used to perform a detailed analysis of the physics leading to the low-frequency oscillations.
Effect of Vortex Flow on Heat Transfer to Combustion Chamber Wall
Authors: Ghafourian A. , Saidi M. H. , Jahangirian S. , Abarham M.
Published: March 2007

A new experimental facility was designed, fabricated, and tested to model and study the effect of bidirectional swirl flow on the rate of heat transfer to combustion chamber walls. Reduction of this heat transfer can result in time and cost of design and fabrication methods of combustion chambers. The experimental study was performed using propane and air with oxygen as fuel and oxidizer, respectively. For similar flow rates, in cases where bidirectional flow was present, wall temperature reductions of up to 70% were observed. In cases where only some of the oxidizer was injected from the chamber end to generate the bidirectional swirl flow, the lowest wall temperature existed. This can be due to better mixing of fuel and oxidizer and absence of hot spots in the combustion core.
Prediction of Peak Cylinder Pressure Variations Over Varying Inlet Air Condition of Compression-Ignition Engine
Authors: Chen Gong
Published: March 2007

Peak cylinder pressure (pmax) of a compression-ignition engine can be affected by the engine inlet air condition, such as its inlet air temperature (Ti) and pressure (pi). The variation of peak cylinder pressure due to varying inlet air temperature or pressure is analytically studied. A model is developed and simplified, and thus the variations of pmax can be predicted along with varying inlet air temperature or pressure. The analysis and prediction indicate that cylinder active compression ratio (CR) and intake air boost ratio (pm0∕pi0) play relatively significant roles in affecting the variation of pmax over inlet air temperature and pressure, and the pressure variation is proportional to CRk and ratio pm0∕pi0. Comparison between the predicted results using the simplified model and those from engine experiments shows a close agreement in both the trend and magnitude. The investigation and prediction also include modeling the variation in pmax due to varying the cylinder TDC clearance volume (Vc). The simplified model is presented and shows that the change in pmax versus varying Vc also depends on the cylinder compression ratio. It is indicated that for a certain change in the clearance volume, a higher compression-ratio configuration would produce a greater change in pmax than a lower one does, especially as the rest of the engine design and operating parameters remain unchanged.
Combustion Oscillation Monitoring Using Flame Ionization in a Turbulent Premixed Combustor
Authors: Chorpening B. T. , Thornton J. D. , Huckaby E. D. , Benson K. J.
Published: March 2007

To achieve very low NOx emission levels, lean-premixed gas turbine combustors have been commercially implemented that operate near the fuel-lean flame extinction limit. Near the lean limit, however, flashback, lean blow off, and combustion dynamics have appeared as problems during operation. To help address these operational problems, a combustion control and diagnostics sensor (CCADS) for gas turbine combustors is being developed. CCADS uses the electrical properties of the flame to detect key events and monitor critical operating parameters within the combustor. Previous development efforts have shown the capability of CCADS to monitor flashback and equivalence ratio. Recent work has focused on detecting and measuring combustion instabilities. A highly instrumented atmospheric combustor has been used to measure the pressure oscillations in the combustor, the OH emission, and the flame ion field at the premix injector outlet and along the walls of the combustor. This instrumentation allows examination of the downstream extent of the combustion field using both the OH emission and the corresponding electron and ion distribution near the walls of the combustor. In most cases, the strongest pressure oscillation dominates the frequency behavior of the OH emission and the flame ion signals. Using this highly instrumented combustor, tests were run over a matrix of equivalence ratios from 0.6 to 0.8, with an inlet reference velocity of 25m∕s(82ft∕s). The acoustics of the fuel system for the combustor were tuned using an active-passive technique with an adjustable quarter-wave resonator. Although several statistics were investigated for correlation with the dynamic pressure in the combustor, the best correlation was found with the standard deviation of the guard current. The data show a monotonic relationship between the standard deviation of the guard current (the current through the flame at the premix injector outlet) and the standard deviation of the chamber pressure. Therefore, the relationship between the standard deviation of the guard current and the standard deviation of the pressure is the most promising for monitoring the dynamic pressure of the combustor using the flame ionization signal. This addition to the capabilities of CCADS would allow for dynamic pressure monitoring on commercial gas turbines without a pressure transducer.
The Effects of High-Pressure Injection on a Compression–Ignition, Direct Injection of Natural Gas Engine
Authors: McTaggart-Cowan G. P. , Jones H. L. , Rogak S. N. , Bushe W. K. , Hill P. G. , Munshi S. R.
Published: March 2007

This study investigated the effects of injection pressure on the performance and emissions of a pilot-ignited, late-cycle direct-injected natural gas fueled heavy-duty engine. The experiments, conducted on a single-cylinder engine, covered a wide range of engine speeds, loads, and exhaust gas recirculation fractions. The injection pressure was varied at each operating condition while all other parameters were held constant. At high loads, increasing the injection pressure substantially reduced particulate matter and CO emissions, with small increases in NOx and no significant effect on hydrocarbon emissions or fuel consumption. At low loads, injection pressure had no significant impact on either emissions or performance. At high loads, higher injection pressures consistently reduced both the number density and the size of particles in the exhaust stream. Injection pressure had reduced effects at increased engine speeds.
Multifunctional Energy System (MES) With Multifossil Fuels and Multiproducts
Authors: Jin Hongguang , Han Wei , Gao Lin
Published: March 2007

A new kind of multifunctional energy system (MES) with multifossil fuels and multiproducts is proposed in this paper. This new system consumes coal and natural gas as fuel simultaneously, and cogenerates methanol and power. Coal and natural gas are utilized synthetically based on the method of dual-fuel reforming, which integrates the methane/steam reforming and the combustion of coal. During the dual-fuel reforming process, combustion of coal provides high-temperature thermal energy to methane/steam reforming reaction to product syngas. Then, the chemical energy of syngas is used efficiently since the new system integrates the chemical process and power plant. In this manner, the energy including both chemical energy of fuels and thermal energy can be used more effectively from the viewpoint of the whole system. As a result, the total energy efficiency of this new system was about 60–66%. Compared with the conventional systems, the new system provides an energy savings of about 8–15%. The results obtained here indicate that this new system may provide a new way to utilize coal and natural gas more efficiently and economically.
Experimental Contribution to High-Precision Characterization of Magnetic Forces in Active Magnetic Bearings
Authors: Kjølhede Klaus , Santos Ilmar F.
Published: March 2007

Parameter identification procedures and model validation are major steps toward intelligent machines supported by active magnetic bearings (AMB). The ability of measuring the electromagnetic bearing forces, or deriving them from measuring the magnetic flux, strongly contributes to the model validation and leads to novel approaches in identifying crucial rotor parameters. This is the main focus of this paper, where an intelligent AMB is being developed with the aim of aiding the accurate identification of damping and stiffness coefficients of active lubricated journal bearings. The main contribution of the work is the characterization of magnetic forces by using two different experimental approaches. Such approaches are investigated and described in detail. A special test rig is designed where the four pole AMB is able to generate forces up to 1900N. The high-precision characterization of the magnetic forces is conducted using different experimental tests: (i) by using hall sensors mounted directly on the poles (precise measurements of the magnetic flux) and by an auxiliary system, composed of strain gages and flexible beams attached to the rotor, (ii) by measuring the input current and bearing gap variations, monitoring the bearing input signals. Advantages and drawbacks of the different methodologies are critically discussed. The linearity ranges are experimentally determined and the characterization of magnetic forces with a high accuracy of <1% is achieved (percent error is normalized with respect to the instantaneous measured force obtained from the strain gauges signals).
Test Results and Analytical Predictions for Rotor Drop Testing of an Active Magnetic Bearing Expander/Generator
Authors: Hawkins Lawrence , Filatov Alexei , Imani Shamim , Prosser Darren
Published: March 2007

A cryogenic gas expander system that incorporates a high-performance, high-speed permanent magnet, direct-drive generator and low loss magnetic bearings is described. Flow loop testing to 30,000rpm was completed at the system manufacturer’s facility in January 2005, and field installation is scheduled for October 2005. As part of the system testing, the rotor was dropped onto the backup bearings multiple times at an intermediate speed and at 30,000rpm. Orbit and time-history data from a full speed drop and spin down are presented and discussed in detail. A transient, nonlinear rotordynamic analysis simulation model was developed for the machine to provide insight into the dynamic behavior. The model includes the dead band clearance, the flexible backup bearing support, and hard stop. Model predictions are discussed relative to the test data.
Genetic Algorithm Optimization for Primary Surfaces Recuperator of Microturbine
Authors: Qiuwang Wang , Hongxia Liang , Gongnan Xie , Min Zeng , Laiqin Luo , ZhenPing Feng
Published: March 2007

In recent years, the genetic algorithm (GA) technique has gotten much attention in solving real-world problems. This technique has a strong ability for global searching and optimization based on various objectives for their optimal parameters. The technique may be applied to complicated heat exchangers and is particularly useful for new types. It is important to optimize the heat exchanger, for minimum volume/weight, to save fabrication cost or for improved effectiveness to save energy consumption, under the requirement of allowable pressure drop; simultaneously it is mandatory to optimize geometry parameters of heating plate from technical and economic standpoints. In this paper, GA is used to optimize the cross wavy primary surface (CWPS) and cross corrugated primary surface (CCPS) geometry characteristic of recuperator in a 100kW microturbine, in order to get more compactness and minimum volume and weight. Two kinds of fitness assignment methods are considered. Furthermore, GA parameters are set optimally to yield smoother and faster fitness convergence. The comparison shows the superiority of GA and confirms its potential to solve the objective problem. When the rectangular recuperator core size and corrugated geometries are evaluated, in the CWPS the weight of the recuperator decreases by 12% or more; the coefficient of compactness increases by up to 19%, with an increase of total pressure drop by 0.84% compared to the original design data; and the total pressure drop versus the operating pressure is controlled to be less than 3%. In the CCPS area compactness is increased to 70% of the initial data by decreasing pitch and relatively high height of the passage, the weight decreases by 17–36%, depending on the inclination angle (θ). Comparatively the CCPS shows superior performance for use in compact recuperators in the future. The GA technique chooses from a variety of geometry characters, optimizes them and picks out the one which provides the closest fit to the recuperator for microturbine.
Experimental Investigation of Flow Phenomena of a Single Fuel Jet in Cross-Flow During Highly Preheated Air Combustion Conditions
Authors: Mörtberg Magnus , Blasiak Wlodzimierz , Gupta Ashwani K.
Published: March 2007

Particle image velocimetry and a spectroscopy technique has been used to obtain information on the flow dynamics and flame thermal signatures of a fuel jet injected into a cross-flow of normal temperature and very high-temperature combustion air. Flame fluctuations were obtained using a high-speed camera and then performing fast Fourier transform on the signal. High-temperature air combustion has been demonstrated to provide significant energy savings, higher heat flux, and reduction of pollution and equipment size of industrial furnaces. The dynamics of flow associated with high temperature combustion air conditions (for mean velocity, axial strain rate and vorticity) has been obtained in two-dimensional using propane and methane as the fuels. The data have been compared with normal temperature combustion air case, including the nonburning case. A specially designed experimental test furnace facility was used to provide well-controlled conditions and allowed air preheats to 1100°C using regenerative burners. Four different experimental cases have been examined. The momentum flux ratio between the burning and nonburning conditions was kept constant to provide comparison between cases. The results provide the role of high-temperature combustion air on the dynamics of the flow, turbulence, and mixing under nonburning and combustion conditions. The data provide the direct role of combustion on flow dynamics, turbulence, and flame fluctuations. High-temperature combustion air at low-oxygen concentration showed larger flame volume with less fluctuation than normal or high-temperature normal air cases. High-temperature combustion air technology prolongs mixing in the combustion zone to enhance the flame volume, reduce flame fluctuations, and to provide uniform flow and thermal characteristics. This information assists in model validation and model development for new applications and technology development using high-temperature air combustion principles.
Components Map Generation of Gas Turbine Engine Using Genetic Algorithms and Engine Performance Deck Data
Authors: Kong Changduk , Ki Jayoung
Published: March 2007

In order to estimate the gas turbine engine performance precisely, the component maps containing their own performance characteristics should be used. Because the components map is an engine manufacturer’s propriety obtained from many experimental tests with high cost, they are not provided to the customer generally. Some scaling methods for gas turbine component maps using experimental data or data partially given by engine manufacturers had been proposed in a previous study. Among them the map generation method using experimental data and genetic algorithms had showed the possibility of composing the component maps from some random test data. However not only does this method need more experimental data to obtain more realistic component maps but it also requires some more calculation time to treat the additional random test data by the component map generation program. Moreover some unnecessary test data may introduced to generate inaccuracy in component maps. The map generation method called the system identification method using partially given data from the engine manufacturer (Kong and Ki, 2003, ASME J. Eng. Gas Turbines Power, 125, 958–979) can improve the traditional scaling methods by multiplying the scaling factors at design point to off-design point data of the original performance maps, but some reference map data at off-design points should be needed. In this study a component map generation method, which may identify the component map conversely from some calculation results of a performance deck provided by the engine manufacturer using the genetic algorithms, was newly proposed to overcome the previous difficulties. As a demonstration example for this study, the PW206C turbo shaft engine for the tilt rotor type smart unmanned aerial vehicle which has been developed by Korea Aerospace Research Institute was used. In order to verify the proposed method, steady-state performance analysis results using the newly generated component maps were compared with them performed by the Estimated Engine Performance Program deck provided by the engine manufacturer. The performance results using the identified maps were also compared with them using the traditional scaling method. In this investigation, it was found that the newly proposed map generation method would be more effective than the traditional scaling method and the methods explained above.
Lean Blowout Limits and NOx Emissions of Turbulent, Lean Premixed, Hydrogen-Enriched Methane/Air Flames at High Pressure
Authors: Griebel P. , Boschek E. , Jansohn P.
Published: March 2007

Flame stability is a crucial issue in low NOx combustion systems operating at extremely lean conditions. Hydrogen enrichment seems to be a promising option to extend lean blowout limits (LBO) of natural gas combustion. This experimental study addresses flame stability enhancement and NOx reduction in turbulent, high-pressure, lean premixed methane/air flames in a generic combustor capable of a wide range of operating conditions. Lean blowout limits and NOx emissions are presented for pressures up to 14bar, bulk velocities in the range of 32–80m∕s, two different preheating temperatures (673K, 773K), and a range of fuel mixtures from pure methane to 20% H2∕80%CH4 by volume. The influence of turbulence on LBO limits is also discussed. In addition to the investigation of perfectly premixed H2-enriched flames, LBO and NOx are also discussed for hydrogen piloting. Experiments have revealed that a mixture of 20% hydrogen and 80% methane, by volume, can typically extend the lean blowout limit by ∼10% compared to pure methane. The flame temperature at LBO is ∼60K lower resulting in the reduction of NOx concentration by ≈35%(0.5→0.3ppm∕15%O2).
Transient Rotor/Active Magnetic Bearing Control Using Sampled Wavelet Coefficients
Authors: Cade Iain S. , Keogh Patrick S. , Sahinkaya M. Necip
Published: March 2007

A novel method for transient rotor/active magnetic bearing control using sampled wavelet coefficients is proposed. Control currents are formulated in the wavelet transform domain, prior to signal reconstruction. The wavelet based controller is designed from target transient responses due to step changes in wavelet coefficients of applied forces. Transient system dynamics are embedded in the controller and evaluated from on-line system identification. Experimental validation is undertaken using a flexible rotor/active magnetic bearing system. Mass loss tests were performed at two critical speeds corresponding to near sudden changes in unbalance that are capable of exciting rotor dynamic modes in a transient manner. The controller is shown to suppress the transient responses within a finite settling time.
A Microfluidic Mixer Utilizing Electrokinetic Relay Switching and Asymmetric Flow Geometries
Authors: Wang Yiou , Zhe Jiang , Dutta Prashanta , Chung Benjamin T.
Published: March 2007

Performances of a hybrid electrokinetic-passive micromixer are predicted numerically. An h/p-type spectral element method is used to simulate the mixing behavior in microdevices. The numerical algorithm employs modal spectral expansion in quadrilateral and unstructured triangular meshes and provides high-order numerical accuracy. A second-order accurate, stiffly stable integration scheme is used for temporal integration. In the numerical technique, the electric double layer is not resolved to avoid expensive computation, rather a slip velocity is assigned at the channel surface based on the electric field and the electroosmotic mobility. The presented hybrid mixing scheme takes advantages of mixing enhancements induced by asymmetric flow geometries and electrokinetic relay actuation. Effects of relay frequency, applied electric potential, channel width, and channel geometry on micromixing have been conducted. Numerical results show that electrokinetic relay at an appropriate frequency causes effective mixing. Moreover, asymmetric flow geometries and narrow channel width are critical for ultraeffective mixing. The proposed hybrid mixing scheme not only provides excellent mixing within very short time, but also can easily be integrated with microdevices for “lab-on-a-chip” applications because there is no need of any external mechanical pumps.
A Study of the Effect of Polymer Solution in Promoting Friction
Reduction in Turbulent Channel Flow
Authors: Cunha F. R. , Andreotti M.
Published: March 2007

In this work, turbulent drag reduction in a pipe is investigated by using laser Doppler velocimetry. The effect of decreasing the friction factor of the flow is obtained by addition of high molecular weight polymers. The mechanism of drag reduction is explained in terms of a stress anisotropy that inhibits the transversal transport of momentum by turbulent fluctuations. Semi-theoretical models based on a nonlinear constitutive equation, which takes into account an extra extensional rate of strain in the flow produced by the local additive orientation, are presented. The semi-theoretical models used to predict the friction factor of the flow in the presence of the polymer have successfully described the experimental measurements. The results have revealed a reduction in the friction factor of 65% for a concentration of 350ppm in volume of polyacrylamide (PAMA) in an aqueous solution. In addition, the flow statistics, such as the axial and radial velocity fluctuations, the normalized autocorrelation functions as well as the power spectra for both velocity fluctuation components, are examined for the Newtonian flow of pure water and the flow of a 120ppm solution of PAMA at the same friction velocity. Next, the results are compared in order to characterize the effect of the additive on the turbulent flow.
Carbon Nanotube–Magnetite Composites, With Applications to Developing Unique Magnetorheological Fluids
Authors: Samouhos Stephen , McKinley Gareth
Published: March 2007

The development of carbon nanotube (CNT) based technology is limited in part by the lack of effective bulk methods for precisely manipulating and aligning nanotubes at the very fine scale. Moreover, the innate hydrophobic and inert nature of the CNT surface limits their compatibility with aqueous systems and flexibility for surface chemistry functionalization. This paper assesses the variety of methods developed to couple magnetically susceptible components such as ferromagnetic material with CNTs in order to overcome these limitations. In addition to reviewing the past 16 years of relevant literature, our own methods for noncovalent surface coating of CNT’s with magnetite nanoparticles are described. The application of such composites is then explored within the framework of a magnetorheological (MR) fluid. It is found that the addition of magnetite nanoparticles to a MR fluid enriches the available MR response, resulting, in some cases, in an increased sedimentation stability, larger saturation critical stresses, and faster response to time varying magnetic fields. Finally, our own composite based MR fluid is discussed, and shown to possess a field dependent response that is a hybrid between that observed in ferrofluids and conventional MR fluids.
Jet Wiping in Hot-Dip Galvanization
Authors: Gosset Anne , Buchlin Jean-Marie
Published: March 2007

This paper presents an analysis of the gas-jet wiping process in hot-dip galvanization. This technique consists of reducing the liquid film thickness on a moving substrate by applying gas slot jets. A theoretical development allows the computation of the film thickness evolution in the wiping zone. It is further simplified to an engineering model which predicts directly the final coating thickness, in good agreement with wiping experiments. The limit of applicability of jet wiping is due to the occurence of a violent film instability, called splashing, which takes the form of a liquid droplet emission just upstream the nozzle. An experimental investigation of this phenomenon is conducted on a water-model facility. Two nozzle designs are tested. The effect of process parameters such as the strip speed, the nozzle pressure, the standoff distance, and the tilt angle of the nozzle on splashing is emphasized. A dimensionless correlation is established to predict the operating conditions leading to splashing occurence. It is successfully confronted to observations made on galvanization lines.
Simulation of Fiber Suspensions—A Multiscale Approach
Authors: Mäkipere Krista , Zamankhan Piroz
Published: March 2007

The present effort is the development of a multiscale modeling, simulation methodology for investigating complex phenomena arising from flowing fiber suspensions. The present approach is capable of coupling behaviors from the Kolmogorov turbulence scale through the full-scale system in which a fiber suspension is flowing. Here the key aspect is adaptive hierarchical modeling. Numerical results are presented for which focus is on fiber floc formation and destruction by hydrodynamic forces in turbulent flows. Specific consideration was given to dynamic simulations of viscoelastic fibers in which the fluid flow is predicted by a method that is a hybrid between direct numerical simulations and large eddy simulation techniques and fluid fibrous structure interactions will be taken into account. Dynamics of simple fiber networks in a shearing flow of water in a channel flow illustrate that the shear-induced bending of the fiber network is enhanced near the walls. Fiber-fiber interaction in straight ducts is also investigated and results show that deformations would be expected during the collision when the surfaces of flocs will be at contact. Smaller velocity magnitudes of the separated fibers compare to the velocity before collision implies the occurrence of an inelastic collision. In addition because of separation of vortices, interference flows around two flocs become very complicated. The results obtained may elucidate the physics behind the breakup of a fiber floc, opening the possibility for developing a meaningful numerical model of the fiber flow at the continuum level where an Eulerian multiphase flow model can be developed for industrial use.
A Theoretical Discussion of a Menisci Micropump Driven by an Electric Field
Authors: Herescu Alexandru , Allen Jeffrey S.
Published: March 2007

The potential for miniaturization of analytical devices made possible by advances in micro-fabrication technology is driving demand for reliable micropumps. A wide variety of micropumps exist with many types of actuating mechanisms. One such mechanism is electrohydrodynamic (EHD) forces which rely upon Coulomb forces on free charges and/or polarization forces on induced dipoles within the liquid to induce fluid motion. EHD has been used to pump liquid phases and to displace gas–liquid interfaces for enhanced boiling heat transfer as well as to displace gas/vapor bubbles. A novel concept for using EHD polarization forces to deflect a stationary meniscus in order to compress and pump a gaseous phase is described. The pumping mechanism consists in alternative compression of two gas volumes by continuous deflection of the two pinned menisci of an entrapped liquid slug in an electric field. Using the Maxwell stress relations, the electric field strength necessary to operate the pump is determined. The operational limits are determined by analyzing the stability limits of the two menisci from inertial and viscous standpoints, corroborated with the natural frequencies of the gas–liquid interfaces.
Evaluation of the Novel
Helicobacter pylori
ClariRes Real-Time PCR Assay for Detection and Clarithromycin Susceptibility Testing of
H. pylori
in Stool Specimens from Symptomatic Children
Authors: Lottspeich Christian , Schwarzer Andrea , Panthel Klaus , Koletzko Sibylle , Rüssmann Holger
Published: March 2007

The aim of the present study was to evaluate the
Helicobacter pylori
ClariRes assay (Ingenetix, Vienna, Austria) for the detection of
H. pylori
infection and the simultaneous clarithromycin susceptibility testing of the
H. pylori
isolates in stool samples from 100 symptomatic children. The results obtained by this novel biprobe real-time PCR method were directly compared with the results obtained from histological examination of gastric biopsy specimens, culturing, the [
13
C]urea breath test, and a monoclonal antibody-based stool antigen enzyme immunoassay (EIA). Fecal specimens from all 54 children who were shown to be noninfected by “gold standard” tests gave true-negative PCR results (specificity, 100%). Of the remaining 46 individuals with a positive
H. pylori
status, 29 were found to be positive by real-time PCR (sensitivity, 63%). For these 29 cases, the
H. pylori
ClariRes assay confirmed all results from phenotypic clarithromycin susceptibility testing by Etest. In summary, this investigation demonstrates that detection of
Helicobacter
DNA in stool samples by real-time PCR is a difficult task and that this method cannot replace the stool antigen EIA (sensitivity, 95.7%) for the accurate diagnosis of
H. pylori
infection in children.
Phenotypic Characterization of Clonal and Nonclonal
Pseudomonas aeruginosa
Strains Isolated from Lungs of Adults with Cystic Fibrosis
Authors: Tingpej Pholawat , Smith Lucas , Rose Barbara , Zhu Hua , Conibear Tim , Al Nassafi Khaled , Manos Jim , Elkins Mark , Bye Peter , Willcox Mark , Bell Scott , Wainwright Claire , Harbour Colin
Published: March 2007

The emergence of virulent
Pseudomonas aeruginosa
clones is a threat to cystic fibrosis (CF) patients globally. Characterization of clonal
P. aeruginosa
strains is critical for an understanding of its clinical impact and developing strategies to meet this problem. Two clonal strains (AES-1 and AES-2) are circulating within CF centers in eastern Australia. In this study, phenotypic characteristics of 43 (14 AES-1, 5 AES-2, and 24 nonclonal)
P. aeruginosa
isolates were compared to gain insight into the properties of clonal strains. All 43 isolates produced bands of the predicted size in PCRs for
vfr
,
rhlI
,
rhlR
,
la
s
A
,
lasB
,
aprA
,
rhlAB
, and
exoS
genes; 42 were positive for
lasI
and
lasR
, and none had
exoU
. Thirty-seven (86%) isolates were positive in total protease assays; on zymography, 24 (56%) produced elastase/staphylolysin and 22 (51%) produced alkaline protease. Clonal isolates were more likely than nonclonal isolates to be positive for total proteases (
P
= 0.02), to show elastase and alkaline protease activity by zymography (
P
= 0.04 and
P
= 0.01, respectively), and to show elastase activity by the elastin-Congo red assay (
P
= 0.04). There were no other associations with genotype. Overall, increasing patient age was associated with decreasing elastase activity (
P
= 0.03). Thirty-two (74%) isolates had at least one
N
-acylhomoserine lactone (AHL) by thin-layer chromatography.
rhl
-associated AHL detection was associated with the production and level of total protease and elastase activity (all
P
< 0.01). Thirty-three (77%) isolates were positive for ExoS by Western blot analysis, 35 (81%) produced rhamnolipids, and 34 (79%) showed chitinase activity. Findings suggest that protease activity during chronic infection may contribute to the transmissibility or virulence of these clonal strains.
Bacterial Arthritis Caused by
Leptotrichia amnionii
Authors: Goto Miki , Hitomi Shigemi , Ishii Tomoo
Published: March 2007

Leptotrichia amnionii
is an organism that rarely causes female genital tract infection. We describe a case of a male patient with arthritis on the left knee joint due to this organism.
Kaposi's Sarcoma-Associated Herpesvirus/Human Herpesvirus 8 ORF50/Rta Lytic Switch Protein Functions as a Tetramer
Authors: Bu Wei , Carroll Kyla Driscoll , Palmeri Diana , Lukac David M.
Published: March 2007

The Kaposi's sarcoma-associated herpesvirus open reading frame 50 (ORF50) protein (called Rta), is necessary and sufficient for reactivation of the virus from latency. We previously demonstrated that a truncated mutant of ORF50 lacking its C-terminal transcriptional activation domain, called ORF50ΔSTAD, formed mixed multimers with wild-type (WT) ORF50 and functioned as a dominant negative inhibitor of reactivation. For this report, we investigated the requirements for multimerization of ORF50/Rta in transactivation and viral reactivation. We analyzed multimerization of WT, mutant, and chimeric ORF50 proteins, using Blue Native polyacrylamide gel electrophoresis and size exclusion chromatography. WT and mutant ORF50 proteins form tetramers and higher-order multimers, but not monomers, in solution. The proline-rich, N-terminal leucine heptapeptide repeat (LR) of ORF50 (amino acids [aa] 244 to 275) is necessary but not sufficient for oligomer formation and functions in concert with the central portion of ORF50/Rta (aa 245 to 414). The dominant negative mutant ORF50ΔSTAD requires the LR to form mixed multimers with WT ORF50 and inhibit its function. In the context of the WT ORF50/Rta protein, mutagenesis of the LR, or replacement of the LR by heterologous multimerization domains from the GCN4 or p53 proteins, demonstrates that tetramers of Rta are sufficient for transactivation and viral reactivation. Mutants of Rta that are unable to form tetramers but retain the ability to form higher-order multimers are reduced in function or are nonfunctional. We concluded that the proline content, but not the leucine content, of the LR is critical for determining the oligomeric state of Rta.
Human Immunodeficiency Virus Bearing a Disrupted Central DNA Flap Is Pathogenic In Vivo
Authors: Marsden Matthew D. , Zack Jerome A.
Published: March 2007

The central DNA flap is an important component of lentiviral vectors, but its significance in the context of wild-type human immunodeficiency virus (HIV) is currently unclear. To address this issue, we have compared the in vitro infection kinetics of NL4-3 with those of a flap-deficient mutant and evaluated the in vivo growth characteristics of these viruses by using the SCID-hu mouse model of HIV infection. Flap-deficient virus was only modestly attenuated in vitro, as assessed by single-round and spreading infection assays, and exhibited levels of replication and pathogenesis close to those of the wild-type in vivo. Hence, an intact central flap is not essential for HIV replication.
Structural Basis for the Recognition of Blood Group Trisaccharides by Norovirus
Authors: Cao Sheng , Lou Zhiyong , Tan Ming , Chen Yutao , Liu Yijin , Zhang Zhushan , Zhang Xuejun C. , Jiang Xi , Li Xuemei , Rao Zihe
Published: March 2007

Noroviruses are one of the major causes of nonbacterial gastroenteritis epidemics in humans. Recent studies on norovirus receptors show that different noroviruses recognize different human histo-blood group antigens (HBGAs), and eight receptor binding patterns of noroviruses have been identified. The P domain of the norovirus capsids is directly involved in this recognition. To determine the precise locations and receptor binding modes of HBGA carbohydrates on the viral capsids, a recombinant P protein of a GII-4 strain norovirus, VA387, was cocrystallized with synthetic type A or B trisaccharides. Based on complex crystal structures observed at a 2.0-Å resolution, we demonstrated that the receptor binding site lies at the outermost end of the P domain and forms an extensive hydrogen-bonding network with the saccharide ligand. The A and B trisaccharides display similar binding modes, and the common fucose ring plays a key role in this interaction. The extensive interface between the two protomers in a P dimer also plays a crucial role in the formation of the receptor binding interface.
The DNA Binding Domain of a Papillomavirus E2 Protein Programs a Chimeric Nuclease To Cleave Integrated Human Papillomavirus DNA in HeLa Cervical Carcinoma Cells
Authors: Horner Stacy M. , DiMaio Daniel
Published: March 2007

Viral DNA binding proteins that direct nucleases or other protein domains to viral DNA in lytically or latently infected cells may provide a novel approach to modulate viral gene expression or replication. Cervical carcinogenesis is initiated by high-risk human papillomavirus (HPV) infection, and viral DNA persists in the cancer cells. To test whether a DNA binding domain of a papillomavirus protein can direct a nuclease domain to cleave HPV DNA in cervical cancer cells, we fused the DNA binding domain of the bovine papillomavirus type 1 (BPV1) E2 protein to the catalytic domain of the FokI restriction endonuclease, generating a BPV1 E2-FokI chimeric nuclease (BEF). BEF introduced DNA double-strand breaks on both sides of an E2 binding site in vitro, whereas DNA binding or catalytic mutants of BEF did not. After expression of BEF in HeLa cervical carcinoma cells, we detected cleavage at E2 binding sites in the integrated HPV18 DNA in these cells and also at an E2 binding site in cellular DNA. BEF-expressing cells underwent senescence, which required the DNA binding activity of BEF, but not its nuclease activity. These results demonstrate that DNA binding domains of viral proteins can target effector molecules to cognate binding sites in virally infected cells.
Macaques Infected with a CCR5-Tropic Simian/Human Immunodeficiency Virus (SHIV) Develop Broadly Reactive Anti-HIV Neutralizing Antibodies
Authors: Kraft Zane , Derby Nina R. , McCaffrey Ruth A. , Niec Rachel , Blay Wendy M. , Haigwood Nancy L. , Moysi Eirini , Saunders Cheryl J. , Wrin Terri , Petropoulos Christos J. , McElrath M. Juliana , Stamatatos Leonidas
Published: March 2007

The development of anti-human immunodeficiency virus (anti-HIV) neutralizing antibodies and the evolution of the viral envelope glycoprotein were monitored in rhesus macaques infected with a CCR5-tropic simian/human immunodeficiency virus (SHIV), SHIVSF162P4. Homologous neutralizing antibodies developed within the first month of infection in the majority of animals, and their titers were independent of the extent and duration of viral replication during chronic infection. The appearance of homologous neutralizing antibody responses was preceded by the appearance of amino acid changes in specific variable and conserved regions of gp120. Amino acid changes first appeared in the V1, V2, C2, and V3 regions and subsequently in the C3, V4, and V5 regions. Heterologous neutralizing antibody responses developed over time only in animals with sustained plasma viremia. Within 2 years postinfection the breadth of these responses was as broad as that observed in certain patients infected with HIV type 1 (HIV-1) for over a decade. Despite the development of broad anti-HIV-1 neutralizing antibody responses, viral replication persisted in these animals due to viral escape. Our studies indicate that cross-reactive neutralizing antibodies are elicited in a subset of SHIVSF162P4infected macaques and that their development requires continuous viral replication for extended periods of time. More importantly, their late appearance does not prevent progression to disease. The availability of an animal model where cross-reactive anti-HIV neutralizing antibodies are developed may facilitate the identification of virologic and immunologic factors conducive to the development of such antibodies.
Human Immunodeficiency Virus Type 1-Associated CD40 Ligand Transactivates B Lymphocytes and Promotes Infection of CD4+T Cells
Authors: Martin Geneviève , Roy Jocelyn , Barat Corinne , Ouellet Michel , Gilbert Caroline , Tremblay Michel J.
Published: March 2007

Abnormal activation of B lymphocytes is a feature commonly seen in human immunodeficiency virus type 1 (HIV-1)-infected persons. However, the mechanism(s) responsible for this dysfunction is still poorly understood. Having recently shown that CD40L, the ligand for CD40, is inserted within emerging HIV-1 particles, we hypothesized that the contact between virus-anchored host CD40L and CD40 on the surface of B lymphocytes might result in the activation of this cell type. We report here that CD40L-bearing viruses, but not isogenic virions lacking host-derived CD40L, can induce immunoglobulin G and interleukin-6 production. Furthermore, such viral entities were found to induce B-cell homotypic adhesion. These effects were paralleled at the intracellular level by the nuclear translocation of the ubiquitous transcription factor NF-κB. The presence of host-derived CD40L within virions resulted in an increased virus attachment to B cells and a more-efficient B-cell-mediated transfer of HIV-1 to autologous CD4+T lymphocytes. All the above processes were independent of the virus-encoded envelope glycoproteins. Altogether, the data gathered from this series of investigations suggest that the incorporation of host-encoded CD40L in HIV-1 is likely to play a role in the B-cell abnormalities that are seen in infected individuals.
Identification and Characterization of Dominant Helper T-Cell Epitopes in the Nucleocapsid Protein of Severe Acute Respiratory Syndrome Coronavirus
Authors: Zhao Jincun , Huang Qianrong , Wang Wei , Zhang Yan , Lv Ping , Gao Xiao-Ming
Published: March 2007

By using a series of overlapping synthetic peptides covering 98% of the amino acid sequence of the nucleocapsid protein (NP) of severe acute respiratory syndrome coronavirus (SARS-CoV), four helper T-cell (Th) epitopes (NP11, residues 11 to 25; NP51, residues 51 to 65; NP61, residues 61 to 75; and NP111, residues 111 to 125) in C57BL mice (H-2b), four (NP21, residues 21 to 35; NP91, residues 91 to 105; NP331, residues 331 to 345; and NP351, residues 351 to 365) in C3H mice (H-2k), and two (NP81, residues 81 to 95; and NP351, residues 351 to 365) in BALB/c mice (H-2d) have been identified. All of these peptides were able to stimulate the proliferation of NP-specific T-cell lines or freshly isolated lymph node cells from mice immunized with recombinant NP. Immunization of mice with synthetic peptides containing appropriate Th epitopes elicited strong cellular immunity in vivo, as evidenced by delayed-type hypersensitivity. Priming with the helper peptides (e.g., NP111 and NP351) significantly accelerated the immune response induced by recombinant NP, as determined by the production of NP-specific antibodies. When fused with a conserved neutralizing epitope (SP1143-1157) from the spike protein of SARS-CoV, NP111 and NP351 assisted in the production of high-titer neutralizing antibodies in vivo. These data provide useful insights regarding immunity against SARS-CoV and have the potential to help guide the design of peptide-based vaccines.