bluuebunny/crossref_metadata_2025 huggingface dataset:
Computational Fluid Dynamic Applications for Jet Propulsion System Integration
Authors: Tindell R. H.
Published: April 2008

The impact of computational fluid dynamics (CFD) methods on the development of advanced aerospace vehicles is growing stronger year by year. Design engineers are now becoming familiar with CFD tools and are developing productive methods and techniques for their applications. This paper presents and discusses applications of CFD methods used at Grumman to design and predict the performance of propulsion system elements such as inlets and nozzles. The paper demonstrates techniques for applying various CFD codes and shows several interesting and unique results. A novel application of a supersonic Euler analysis of an inlet approach flow field, to clarify a wind tunnel-to-flight data conflict, is presented. In another example, calculations and measurements of low-speed inlet performance at angle of attack are compared. This is highlighted by employing a simplistic and low-cost computational model. More complex inlet flow phenomena at high angles of attack, calculated using an approach that combines a panel method with a Navier-Stokes (N-S) code, is also reviewed. The inlet fluid mechanics picture is rounded out by describing an N-S calculation and a comparison with test data of an offset diffuser having massively separated flow on one wall. Finally, the propulsion integration picture is completed by a discussion of the results of nozzle-afterbody calculations, using both a complete aircraft simulation in a N-S code, and a more economical calculation using an equivalent body of revolution technique.
A Comparative Evaluation of Advanced Combined Cycle Alternatives
Authors: Bolland O.
Published: April 2008

This paper presents a comparison of measures to improve the efficiency of combined gas and steam turbine cycles. A typical modern dual pressure combined cycle has been chosen as a reference. Several alternative arrangements to improve the efficiency are considered. These comprise the dual pressure reheat cycle, the triple pressure cycle, the triple pressure reheat cycle, the dual pressure supercritical reheat cycle, and the triple pressure supercritical reheat cycle. The effect of supplementary firing is also considered for some cases. The different alternatives are compared with respect to efficiency, required heat transfer area, and stack temperature. A full exergy analysis is given to explain the performance differences for the cycle alternatives. The exergy balance shows a detailed breakdown of all system losses for the HRSG, steam turbine, condenser, and piping.
Fault Detection and Diagnosis in Gas Turbines
Authors: Merrington G. , Kwon Oh-Kyu , Goodwin G. , Carlsson B.
Published: April 2008

Modern military aircraft are fitted with Engine Monitoring Systems (EMS), which have the potential to provide maintenance personnel with valuable information for diagnosing engine faults and assessing engine condition. In this study, analytical redundancy methods have been applied to gas turbine engine transient data with the view to extracting the desired fault information. The basic idea is to use mathematical models to interrelate the measured variables and then monitor the effects of fault conditions on the new estimates of the model parameters. In most of the existing literature the models used are assumed to be perfect with the primary source of error arising from the measurement noise. In the technique to be described, a new method of quantifying the effects of changes in the operating conditions is presented when simplified models are employed. The technique accounts for undermodeling effects and errors arising from linearization of an inherently nonlinear system. Results obtained show a marked improvement over those obtained with traditional methods.
Design of Robust Controllers for Gas Turbine Engines
Authors: Moellenhoff D. E. , Rao S. Vittal , Skarvan C. A.
Published: April 2008

This paper describes robust controller design methodologies for gas turbine engines. A linear state variable model for the engine is derived using partial derivatives. The Linear Quadratic Gaussian with Loop Transfer Recovery (LQG/LTR) and the Parameter Robust Linear Quadratic Gaussian (PRLQG) robust controller design methodologies have been used to design a controller for gas turbine engines. A new method is proposed by combining the features of LQG/LTR and PRLQG methods and yields good robustness properties with respect to both unstructured uncertainties in the frequency domain and structured parameter variations in the time domain. The new procedure is illustrated with the help of an aircraft gas turbine engine model.
An Approach for Evaluation of Gas Turbine Deposition
Authors: Wenglarz R. A.
Published: April 2008

An approach for estimating deposition in gas turbines is described. This approach extrapolates deposition data from lower cost experiments than turbine engine or cascade tests. The purpose is a method to screen candidate fuels and turbine protection methods so that only the most promising need be evaluated in turbine tests. The deposition approach is applied to estimate deposition maintenance intervals for a tested fuel, evaluate benefits of hot gas cleanup, and provide fuel screening criteria.
Blade Repair With Adaptive Vision Tracking
Authors: Anderson J. R. , Skinner M. J.
Published: April 2008

The paper discusses the repair welding of compressor and other blades contained in gas turbine engines. The specific topics of discussion are the application requirements, the general metallurgical considerations, the synchronized pulsation arc welding process, the adaptive vision system employed and the computer-controlled welding system. Reference to an actual installation of this technology will be included.
Progress on the Investigation of Coal-Water Slurry Fuel Combustion in a Medium-Speed Diesel Engine: Part 5—Combustion Studies
Authors: Hsu B. D. , Confer G. L. , Shen Z. J.
Published: April 2008

In the GE 7FDL single-cylinder research diesel engine, coal-water slurry (CWS) fuel combustion optimization studies were conducted using electronically controlled CWS and pilot accumulator injectors. The most important performance parameters of peak firing pressure, combustion efficiency (coal burnout), and specific fuel comsumption were evaluated in relationship to CWS and pilot injection timing, CWS injector hole size, shape, and number, CWS fuel injection spray angles and injection pressure. Heat release diagrams, as well as exhaust samples (gaseous and particulate), were analyzed for each case. Interesting effects of fuel spray impingement and CWS fuel “Delayed Ignition” were observed. With the engine operating at 2.0 MPa IMEP and 1050 rpm, it was able to obtain over 99.5 percent combustion efficiency while holding the cylinder firing pressure below 17 MPa and thermal efficiency equivalent to diesel fuel operation.
Influence of a Shroud on Swirler Flow Fields
Authors: Eroglu H. , Chigier N.
Published: April 2008

The flow fields for swirlers with and without a shroud were measured using a twocomponent laser-Doppler velocimeter (LDV) system. The primary goal of this study is to investigate the effect of shrouds on swirler flow fields, in order to provide useful design information for the manufacture of gas turbine fuel nozzles, and to supply benchmark data for comparison with numerical predictions. As a result of the measurements, the radial distributions of three mean velocity components, turbulence intensity, and shear stresses were obtained at five locations (x/d = 0.1, 1, 2, 4, and 8) along the axis of the swirlers. The LDV system was operated in the 20 deg off-axis forward scatter mode with beam expanders and Bragg cell frequency shifting on both components. The flow was seeded by 1 μm mean diameter atomized particles of glycerol and water (50/50) mixture. Comparison of flow with and without the shroud showed that the jet diameter was much smaller, and the flow deceleration in the downstream direction was faster, due to the influence of the shroud, at the same supply pressure (750 mm H2O). As a result of the significant reduction in the swirl number due to the addition of the shroud, the recirculation zone disappeared. In addition to its influence on recirculation, the shroud caused a radially inward shift of the maximum mean and turbulence parameters at all axial locations. The anisotropy of turbulence increased as compared to the values for the swirler without the shroud.
Reliability Analysis of Structural Ceramic Components Using a Three-Parameter Weibull Distribution
Authors: Duffy S. F. , Powers L. M. , Starlinger A.
Published: April 2008

This paper describes nonlinear regression estimators for the three-parameter Weibull distribution. Issues relating to the bias and invariance associated with these estimators are examined numerically using Monte Carlo simulation methods. The estimators were used to extract parameters from sintered silicon nitride failure data. A reliability analysis was performed on a turbopump blade utilizing the three-parameter Weibull distribution and the estimates from the sintered silicon nitride data.
Micromechanical Analysis of the Failure Process in Ceramic Matrix Composites
Authors: Rubinstein A. A.
Published: April 2008

An analysis of the effectiveness of fiber reinforcement in brittle matrix composites is presented. The analytical method allows consideration of discrete fiber distribution and examination of the development of crack growth parameters on the microscale. The problem associated with bridging zone development is addressed here; therefore, the bridging zone is considered to be smaller than the main pre-existing crack, and the small-scale approach is used. The mechanics of the reinforcement is accurately accounted for in the process zone of a growing crack. Closed-form solutions characterizing the initial failure process are presented for linear and nonlinear forcefiber pullout displacement relationships. The implicit exact solution for the extended bridging zone is presented as well.
Precision Drilling of Ceramic-Coated Components With Abrasive-Waterjets
Authors: Hashish M. , Whalen J.
Published: April 2008

This paper addresses an experimental investigation on the feasibility of using abrasive-waterjets (AWJs) for the precision drilling of small-diameter holes in advanced aircraft engine components. These components are sprayed with ceramic thermal barrier coating (TBC), and the required holes are typically 0.025 in. in diameter with a drilling angle of 25 deg. The parameters of the AWJ were varied to study their effects on both quantitative and qualitative hole drilling parameters. The unique techniques of assisting the abrasive feed process, ramping the waterjet pressure during drilling, and varying the jet dwell time after piercing were effectively implemented to control hole quality and size. The results of the experiments indicate the accuracy and repeatability of the AWJ technique in meeting the air flow and hole size requirements. Production parts were drilled for prototype engine testing.
Extending the Fatigue Life of Aircraft Engine Components by Hole Cold Expansion Technology
Authors: Rufin A. C.
Published: April 2008

The split-sleeve cold expansion process has been used successfully for over 20 years to extend the fatigue life of holes in aircraft structures. Cold expansion technology can also be applied to enhance engine low-cycle fatigue (LCF) performance in both production and repair applications. Specific test data are presented showing that fatigue life extension can be attained by cold expansion of holes in a wide range of situations (including nonround hole geometries and low edge margins), and in components subjected to high operating temperatures. A cold expanded bushing system is compared to standard shrink-fit bushing installations. Finally, two case studies are used to illustrate the application of cold expansion to full-scale engine components.
Design and Evaluation of Silicon Nitride Turbocharger Rotors
Authors: Takama K. , Sasaki S. , Shimizu T. , Kamiya N.
Published: April 2008

Two types of silicon nitride ceramic rotor have been introduced into the Japanese market by Toyota Motor Corporation, named CT26 and CT12A, to improve engine acceleration response by the reduction in moment of inertia. In order to design a suitable blade shape for a ceramic rotor, the critical stress of the blade was determined by the results obtained experimentally from correlating the fracture origin over spintested rotors with centrifugal stress at fracture. A suitable blade shape has been determined for the CT26 turbocharger rotor type, which is identical to the metal rotor except for the disk diameter of hub back face and the blade thickness. The CT12A type is of similar design to the CT26 type; all dimensions could be reduced except for the inlet blade thickness, which is determined by foreign object damage (FOD) resistance.
Application of Ceramics to Turbocharger Rotors for Passenger Cars
Authors: Katano Y. , Ando M. , Itoh T. , Sasaki M.
Published: April 2008

Nissan has been developing and marketing ceramic turbocharger rotors for five years. This paper outlines the major theories and techniques used in ceramic fabrication, joining of ceramic and metal components, and machining of ceramics. It also presents a dynamic stress analysis using DYNA3D and describes techniques used in performing impact damage experiments, reliability evaluation, and lifetime preprediction.
Development of a Set of Equations for Incorporating Disk Flexibility Effects in Rotordynamic Analyses
Authors: Flowers G. T. , Ryan S. G.
Published: April 2008

Rotordynamic equations that account for disk flexibility are developed. These equations employ free-free rotor modes to model the rotor system. Only transverse vibrations of the disks are considered, with the shaft/disk system considered to be torsionally rigid. Second-order elastic foreshortening effects that couple with the rotor speed to produce first-order terms in the equations of motion are included. The approach developed in this study is readily adaptable for usage in many of the codes that are currently used in rotordynamic simulations. The equations are similar to those used in standard rigid disk analyses but with additional terms that include the effects of disk flexibility. An example case is presented to demonstrate the use of the equations and to show the influence of disk flexibility on the rotor dynamic behavior of a sample system.
Combustion System Performance and Field Test Results of the MS7001F Gas Turbine
Authors: Claeys J. P. , Elward K. M. , Mick W. J. , Symonds R. A.
Published: April 2008

This paper presents the results of the combustion system test of the MS7001F installed at the Virginia Power Chesterfield station. Tests of water and steam injection for NOx control were performed. Results of emissions, combustor dynamics, and combustor hardware performance are presented. Emissions test results include NOx, CO, unburned hydrocarbons, VOC, and formaldehyde levels. Combustor dynamic activity over a range of diluent injection ratios, and the performance of an actively cooled transition duct are also discussed. Combustion system mechanical performance is described following the first combustion system inspection.
Development of a Liquid-Fueled, Lean-Premixed Gas Turbine Combustor
Authors: Cowell L. H. , Smith K. O.
Published: April 2008

Development of a lean-premixed, liquid-fueled combustor is in progress to achieve ultra-low NOx emissions at typical gas turbine operating conditions. A filming fuel injector design was tested on a bench scale can combustor to evaluate critical design and operating parameters for low-emissions performance. Testing was completed using No. 2 diesel. Key design variables tested include premixing length, swirler angle, injector centerbody diameter, and reduced liner cooling. NOx emissions below 12 ppmv at 9 bar pressure were measured. Corresponding CO levels were 50 ppmv. An optimized injector design was fabricated for testing in a three injector sector of an annular combustor. Operating parameters and test results are discussed in the paper.
Private Vehicles for Personal Transportation
Authors: Amann C. A.
Published: April 2008

In the United States, private personal transportation has become dominated by the automobile, a platform supported on four wheels and propelled by an internal combustion engine (ICE). Some of the reasons why this combination has emerged as the preferred choice are reviewed. Since urban air quality has become an issue, the ICE has kept pace with progressively more stringent exhaust-emissions regulations. Future emissions standards will encourage the use of alternative fuels and battery-electric propulsion. Looking far into the future, the depletion of fossil-fuel resources and/or definitive evidence that greenhouse gases are actually changing the global climate would foster a shift toward nuclear and solar energy. The automobile platform is compatible with such a shift. The ICE and the electric motor remain as potential motive sources, although they would face some difficult challenges.
Factors Affecting the Performance of Engine Air Filters
Authors: Jaroszczyk T. , Wake J. , Connor M. J.
Published: April 2008

Abrasive particles entering an engine because of inadequate air filtration can cause excessive wear, which may lead to premature engine failure. Despite the importance of filtration in engine systems, there is little understanding of the dynamics of the filtration process. Often, limited space is available for an engine air induction system. Therefore, filters are designed in smaller packages, resulting in higher aerosol velocities through the primary filter material. High aerosol velocities may cause dust re-entrainment and increase the amount of dust penetrating the filter. Our experiments with cellulose and synthetic-type filter media show examples of dust reentrainment for fine and coarse dust. Conditions for dust particle re-entrainment are discussed.
Combined Air-Oil Cooling on a Supercharged TC & IC TAM Diesel Engine
Authors: Trenc F. , Pavleticˇ R.
Published: April 2008

In order to reduce the maximum cylinder wall temperatures of an air-cooled TC&IC diesel engine with large longitudinal and circumferential temperature gradients, a curved, squared cross-sectional channel supplied with engine lubrication oil was introduced into the upper part of the cylinder wall. Numerical analyses of the heat transfer within the baseline air-cooled cylinder and intensive experimental work helped to understand the temperature situation in the cylinder at diverse engine running conditions. The results of the combined cooling were greatly affected by the design, dimensions, position of the channel, and the distribution of the cooling oil flow, and are presented in the paper.
Dynamic and Static Flow Analysis of a Gasoline Fuel Injector
Authors: Chen J. L. , Chen G. , Wells M.
Published: April 2008

The effect of the electrical pulse width and the fuel temperature on dynamic flow and static flow rate of a gasoline fuel injector has been numerically and experimentally investigated. In numerical analysis, the physical domain covers the region from upstream of the valve seat to the injector exit. The three-dimensional unsteady Navier-Stokes equations in a curvilinear coordinate system are solved. Due to the needle movement in fuel injection, the physical domain is considered as a function of time. In the experimental study, the test stand consisting of a hydraulic system and an electrical system was designed to meet the requirements of Society of Automotive Engineers. The pulse width of 0.97–7.5 ms and the temperature of 20–100°C were used to study the pintle injector performance. Predicted dynamic flow and static flow rates show higher values at a temperature of 80°C, which are consistent with the test results.
Heat Release Analysis of Oxygen-Enriched Diesel Combustion
Authors: Assanis D. , Karvounis E. , Sekar R. , Marr W.
Published: April 2008

A heat release correlation for oxygen-enriched diesel combustion is being developed through heat release analysis of cylinder pressure data from a single-cylinder diesel engine operating under various levels of oxygen enrichment. Results show that standard combustion correlations available in the literature do not accurately describe oxygen-enriched diesel combustion. A novel functional form is therefore proposed, which is shown to reproduce measured heat release profiles closely, under different operating conditions and levels of oxygen enrichment. The mathematical complexity of the associated curve-fitting problem is maintained at the same level of difficulty as for standard correlations. When the novel correlation is incorporated into a computer simulation of diesel engine operation with oxygen enrichment, the latter predicts pressure traces in excellent agreement with measured pressure data. This demonstrates the potential of the proposed combustion simulation to guide the application of oxygen-enriched technology successfully to a variety of multicylinder diesel systems.
Multidimensional Modeling of Diesel Ignition and Combustion Using a Multistep Kinetics Model
Authors: Kong S.-C. , Reitz R. D.
Published: April 2008

Ignition and combustion mechanisms in diesel engines were studied using the KIVA code, with modifications to the combustion, heat transfer, crevice flow, and spray models. A laminar-and-turbulent characteristic-time combustion model that has been used successfully for spark-ignited engine studies was extended to allow predictions of ignition and combustion in diesel engines. A more accurate prediction of ignition delay was achieved by using a multistep chemical kinetics model. The Shell knock model was implemented for this purpose and was found to be capable of predicting successfully the autoignition of homogeneous mixtures in a rapid compression machine and diesel spray ignition under engine conditions. The physical significance of the model parameters is discussed and the sensitivity of results to the model constants is assessed. The ignition kinetics model was also applied to simulate the ignition process in a Cummins diesel engine. The post-ignition combustion was simulated using both a single-step Arrhenius kinetics model and also the characteristic-time model to account for the energy release during the mixing-controlled combustion phase. The present model differs from that used in earlier multidimensional computations of diesel ignition in that it also includes state-of-the-art turbulence and spray atomization models. In addition, in this study the model predictions are compared to engine data. It is found that good levels of agreement with the experimental data are obtained using the multistep chemical kinetics model for diesel ignition modeling. However, further study is needed of the effects of turbulent mixing on post-ignition combustion.
Modeling and Identification of the Combustion Pressure Process in Internal Combustion Engines: II—Experimental Results
Authors: Connolly F. T. , Yagle A. E.
Published: April 2008

In Connolly and Yagle (1992, 1993) we presented a new model relating cylinder combustion pressure to crankshaft angular velocity in an internal combustion engine, primarily the fluctuations in velocity near the cylinder firing frequency. There are three aspects to this model. First, by changing the independent variable from time to crankshaft angle, a nonlinear differential equation becomes a linear first-order differential equation. Second, a new stochastic model for combustion pressure uses the sum of a deterministic waveform and a raised-cosine window amplitude-modulated by a Bernoulli-Gaussian random sequence, parametrizing the pressure by the sample modulating sequence. This results in a state equation for the square of angular velocity sampled every combustion, with the modulating sequence as input. Third, the inverse problem of reconstructing pressure from noisy angular velocity measurements was formulated as a state-space deconvolution problem, and solved using a Kalman-filter-based deconvolution algorithm. Simulation results in Connolly and Yagle (1992, 1993) show that the parametrized pressure can be deconvolved at low to moderate noise levels, and combustion misfires detected, all in real time. This paper presents and discusses experimental results that confirm this model, at least at the relatively low-speed, low-to-moderate load operating conditions analyzed. They show that cyclic combustion pressure variation is fairly well modeled and may be directly estimated from angular velocity measurements. They also show that the deconvolution algorithm is able to detect misfires and possibly classify their severity. Since the experimental data are taken from an actual V-6 automobile engine, and the algorithms are simple enough to be implemented in real time, these results are directly applicable to real-world combustion pressure identification.
Synteny and Collinearity in Plant Genomes
Authors: Tang Haibao , Bowers John E. , Wang Xiyin , Ming Ray , Alam Maqsudul , Paterson Andrew H.
Published: April 2008

Correlated gene arrangements among taxa provide a valuable framework for inference of shared ancestry of genes and for the utilization of findings from model organisms to study less-well-understood systems. In angiosperms, comparisons of gene arrangements are complicated by recurring polyploidy and extensive genome rearrangement. New genome sequences and improved analytical approaches are clarifying angiosperm evolution and revealing patterns of differential gene loss after genome duplication and differential gene retention associated with evolution of some morphological complexity. Because of variability in DNA substitution rates among taxa and genes, deviation from collinearity might be a more reliable phylogenetic character.
Encoding Gender and Individual Information in the Mouse Vomeronasal Organ
Authors: He Jie , Ma Limei , Kim SangSeong , Nakai Junichi , Yu C. Ron
Published: April 2008

The mammalian vomeronasal organ detects complex chemical signals that convey information about gender, strain, and the social and reproductive status of an individual. How these signals are encoded is poorly understood. We developed transgenic mice expressing the calcium indicator G-CaMP2 and analyzed population responses of vomeronasal neurons to urine from individual animals. A substantial portion of cells was activated by either male or female urine, but only a small population of cells responded exclusively to gender-specific cues shared across strains and individuals. Female cues activated more cells and were subject to more complex hormonal regulations than male cues. In contrast to gender, strain and individual information was encoded by the combinatorial activation of neurons such that urine from different individuals activated distinctive cell populations.
Evaluation of Eight Anti-Rubella Virus Immunoglobulin G Immunoassays That Report Results in International Units per Milliliter
Authors: Dimech Wayne , Panagiotopoulos Lena , Francis Barbara , Laven Nicholas , Marler Joan , Dickeson David , Panayotou Tony , Wilson Kim , Wootten Robyn , Dax Elizabeth M.
Published: April 2008

An evaluation of anti-rubella virus immunoglobulin G (IgG) immunoassays that report in international units per milliliter (IU/ml) was performed to determine their analytical performance and the degree of correlation of the test results. A total of 321 samples were characterized based on results from a hemagglutination inhibition assay. The 48 negative and 273 positive samples were used to determine the sensitivity and specificity of the assays. When equivocal results were interpreted as reactive, the sensitivity of the immunoassays ranged from 98.9 to 99.9% and the specificity ranged from 77.1 to 95.8%. All assays had positive and negative delta values of less than 2. A significant difference between the mean results of all assays was demonstrated by analysis of variance. However, post hoc analysis showed there was good correlation in the mean results expressed in IU/ml between some of the assays. Our results show the level of standardization between anti-rubella virus IgG immunoassays reporting results expressed as IU/ml has improved since a previous study in 1992, but further improvement is required.
Improved Detection of
vanB2
-Containing
Enterococcus faecium
with Vancomycin Susceptibility by Etest Using Oxgall Supplementation
Authors: Grabsch E. A. , Chua K. , Xie S. , Byrne J. , Ballard S. A. , Ward P. B. , Grayson M. L.
Published: April 2008

We have isolated a number of
vanB
-containing
Enterococcus faecium
isolates on bile esculin screening agar containing 6 mg/liter vancomycin, which on subsequent susceptibility testing using Etest have repeatedly demonstrated vancomycin MICs of ≤4 mg/liter. To investigate this genotype-phenotype incongruence of “low-MIC vancomycin-resistant enterococci” (LM-VRE), we examined the molecular characteristics of these isolates, including the presence of the
vanB
operon, using PCR amplification and DNA sequencing. All LM-VRE isolates contained
vanB
associated with the transposon Tn
1549
and were polyclonal. Sequencing of the
vanB
ligase gene showed no differences from the prototype
vanB2
. In addition, we examined supplemented media to improve phenotypic detection of these isolates. Etest detection of LM-VRE improved when Mueller-Hinton agar (MHA) and brain heart infusion agar (BHIA) were supplemented with 10 g/liter oxgall (MHA-Oxg and BHIA-Oxg, respectively). We assessed the sensitivity and specificity of these media to detect vancomycin resistance using vancomycin-resistant
vanB
-containing
E. faecium
(
n
= 11), vancomycin-susceptible (
van
negative)
E. faecium
(
n
= 11), vancomycin-susceptible (
van
negative)
E. faecalis
(
n
= 11), and our LM-VRE (
n
= 23) isolates. After 48 h of incubation, both MHA-Oxg and BHIA-Oxg were 100% (34/34) sensitive and 100% (22/22) specific in the identification of vancomycin resistance. These findings suggest that supplementation of MHA or BHIA with 10 g/liter oxgall should be considered in laboratories where VRE detection protocols rely primarily on strain phenotype rather than early
vanB
gene detection by PCR.
Functional and Physical Interactions of the Herpes Simplex Virus Type 1 UL20 Membrane Protein with Glycoprotein K
Authors: Foster Timothy P. , Chouljenko Vladimir N. , Kousoulas K. G.
Published: April 2008

Herpes simplex virus type 1 glycoprotein K (gK) and the UL20 protein (UL20p) are coordinately transported to the trans-Golgi network (TGN) and cell surfaces and are required for cytoplasmic virion envelopment at the TGN. In addition, cell surface expression of gK and UL20p is required for virus-induced cell fusion. Previously, confocal microscopy colocalization and intracellular transport experiments strongly suggested direct protein-protein interactions between gK and UL20p. Direct protein-protein interactions between gK and UL20p were demonstrated through reciprocal coimmunoprecipitation experiments, as well as with glutathione
S
-transferase (GST) pull-down experiments. A fusion protein consisting of the amino-terminal 66 amino acids of UL20p fused in-frame with GST was expressed in
Escherichia coli
and purified via glutathione column chromatography. Precipitation of GST-UL20p from mixtures of GST-UL20p fusion protein with cellular extracts containing gK specifically coprecipitated gK but not other viral glycoproteins. The purified UL20p-GST fusion protein reacted with all gK-associated protein species. It was concluded that the amino terminus of UL20p, most likely, interacted with gK domain III, which is predicted to lie intracellularly. UL20p-gK domain-specific interactions must serve important functions in the coordinate transport of UL20p and gK to the TGN, because retention of UL20p in the endoplasmic reticulum (ER) via the addition of an ER retention signal at the carboxyl terminus of UL20p forced the ER retention of gK and drastically inhibited intracellular virion envelopment and virus-induced cell fusion.
APOBEC3-Independent Interferon-Induced Viral Clearance in Hepatitis B Virus Transgenic Mice
Authors: Turelli Priscilla , Liagre-Quazzola Alexandra , Mangeat Bastien , Verp Sonia , Jost Stephanie , Trono Didier
Published: April 2008

Interferon (IFN) has been part of the standard treatment of chronic hepatitis B infection for more than 2 decades, yet the mechanism of action of this antiviral remains poorly understood. It was recently observed that members of the human APOBEC family of cytidine deaminases endowed with anti-hepatitis B virus (HBV) activity are upregulated by type I and II IFNs. However, we demonstrated that, in tissue culture, these cellular enzymes are not essential effectors of the anti-HBV action of these cytokines. Here, we show that murine APOBEC3 (muA3) can also block HBV replication. While expressed at low levels in the mouse liver at baseline, muA3 is upregulated upon IFN induction. However, in HBV-transgenic muA3 knockout mice, IFN induction blocked HBV DNA production as efficiently as in control HBV-transgenic muA3-competent animals. We conclude that APOBEC3 is not an essential mediator of the IFN-mediated inhibition of HBV in vivo.
Genetic Analysis of Israel Acute Paralysis Virus: Distinct Clusters Are Circulating in the United States
Authors: Palacios G. , Hui J. , Quan P. L. , Kalkstein A. , Honkavuori K. S. , Bussetti A. V. , Conlan S. , Evans J. , Chen Y. P. , vanEngelsdorp D. , Efrat H. , Pettis J. , Cox-Foster D. , Holmes E. C. , Briese T. , Lipkin W. I.
Published: April 2008

Israel acute paralysis virus (IAPV) is associated with colony collapse disorder of honey bees. Nonetheless, its role in the pathogenesis of the disorder and its geographic distribution are unclear. Here, we report phylogenetic analysis of IAPV obtained from bees in the United States, Canada, Australia, and Israel and the establishment of diagnostic real-time PCR assays for IAPV detection. Our data indicate the existence of at least three distinct IAPV lineages, two of them circulating in the United States. Analysis of representatives from each proposed lineage suggested the possibility of recombination events and revealed differences in coding sequences that may have implications for virulence.
Candidate Microbicide PPCM Blocks Human Immunodeficiency Virus Type 1 Infection in Cell and Tissue Cultures and Prevents Genital Herpes in a Murine Model
Authors: Mesquita Pedro M. M. , Wilson Sarah S. , Manlow Philippe , Fischetti Lucia , Keller Marla J. , Herold Betsy C. , Shattock Robin J.
Published: April 2008

A structurally novel candidate microbicide, PPCM, which is formed from the reaction of
d,l
-mandelic acid with sulfuric acid, provides activity against human immunodeficiency virus (HIV) and herpes simplex virus (HSV) and is not cytotoxic. The objectives of the current studies were to comprehensively evaluate the activity of PPCM in cell and explant cultures, explore the possibility of combining PPCM with HIV-specific reverse transcriptase inhibitors, and evaluate the efficacy of a formulated gel against genital herpes in a murine model. PPCM inhibited infection by laboratory and clinical R5 and X4 clade B and clade C HIV strains in cell culture. Ectocervical and endocervical tissue explants exposed to HIV-1
BaL
in the presence of PPCM were protected (50% inhibitory concentrations [IC
50
] of 3.9 μg/ml for ectocervix and 3.1 μg/ml for endocervix), and transfer of virus to target T cells via migratory cells was significantly impaired (IC
50
of 35.7 μg/ml for ectocervix and 54.6 μg/ml for endocervix). The drug also blocked infection by cell-associated virus. Combinations of PPCM with UC-781 or PMPA in vitro exhibited additive anti-HIV activity. PPCM was incorporated into stable, low-pH gel formulations at concentrations of 0.4% and 4%. Both gels prevented genital herpesvirus infection in mice, even when virus was introduced in human seminal plasma. The abilities of PPCM to inhibit primary HIV isolates, reduce infection by cell-associated virus, and transfer of HIV from migratory to T cells, combined with the complete protection provided by formulated gel against genital herpes, indicate that this drug is an excellent candidate for inclusion in a combination microbicide and would provide protection against both HIV and HSV.
In Vivo Natural Killer Cell Depletion during Primary Simian Immunodeficiency Virus Infection in Rhesus Monkeys
Authors: Choi Elisa I. , Reimann Keith A. , Letvin Norman L.
Published: April 2008

The contribution of natural killer (NK) cells to the immune containment of human immunodeficiency virus infection remains undefined. To directly assess the role of NK cells in an AIDS animal model, we depleted rhesus monkeys of >88% of CD3−CD16+CD159a+NK cells at the time of primary simian immunodeficiency virus (SIV) infection by using anti-CD16 antibody. During the first 11 days following SIV inoculation, when NK cell depletion was most profound, a trend toward higher levels of SIV replication was noted in NK cell-depleted monkeys compared to those in control monkeys. However, this treatment did not result in significant changes in the overall levels or kinetics of plasma viral RNA or affect the SIV-induced central memory CD4+T-lymphocyte loss. These findings are consistent with a limited role for cytotoxic CD16+NK cells in the control of primary SIV viremia.
HLA Class I-Driven Evolution of Human Immunodeficiency Virus Type 1 Subtype C Proteome: Immune Escape and Viral Load
Authors: Rousseau Christine M. , Daniels Marcus G. , Carlson Jonathan M. , Kadie Carl , Crawford Hayley , Prendergast Andrew , Matthews Philippa , Payne Rebecca , Rolland Morgane , Raugi Dana N. , Maust Brandon S. , Learn Gerald H. , Nickle David C. , Coovadia Hoosen , Ndung'u Thumbi , Frahm Nicole , Brander Christian , Walker Bruce D. , Goulder Philip J. R. , Bhattacharya Tanmoy , Heckerman David E. , Korber Bette T. , Mullins James I.
Published: April 2008

Human immunodeficiency virus type 1 (HIV-1) mutations that confer escape from cytotoxic T-lymphocyte (CTL) recognition can sometimes result in lower viral fitness. These mutations can then revert upon transmission to a new host in the absence of CTL-mediated immune selection pressure restricted by the HLA alleles of the prior host. To identify these potentially critical recognition points on the virus, we assessed HLA-driven viral evolution using three phylogenetic correction methods across full HIV-1 subtype C proteomes from a cohort of 261 South Africans and identified amino acids conferring either susceptibility or resistance to CTLs. A total of 558 CTL-susceptible and -resistant HLA-amino acid associations were identified and organized into 310 immunological sets (groups of individual associations related to a single HLA/epitope combination). Mutations away from seven susceptible residues, including four in Gag, were associated with lower plasma viral-RNA loads (
q
< 0.2 [where
q
is the expected false-discovery rate]) in individuals with the corresponding HLA alleles. The ratio of susceptible to resistant residues among those without the corresponding HLA alleles varied in the order Vpr > Gag > Rev > Pol > Nef > Vif > Tat > Env > Vpu (Fisher's exact test;
P
≤ 0.0009 for each comparison), suggesting the same ranking of fitness costs by genes associated with CTL escape. Significantly more HLA-B (χ
2
;
P
= 3.59 × 10
−5
) and HLA-C (χ
2
;
P
= 4.71 × 10
−6
) alleles were associated with amino acid changes than HLA-A, highlighting their importance in driving viral evolution. In conclusion, specific HIV-1 residues (enriched in Vpr, Gag, and Rev) and HLA alleles (particularly B and C) confer susceptibility to the CTL response and are likely to be important in the development of vaccines targeted to decrease the viral load.
Critical Role for Endocytosis in the Regulation of Signaling by the Kaposi's Sarcoma-Associated Herpesvirus K1 Protein
Authors: Tomlinson Christine C. , Damania Blossom
Published: April 2008

Kaposi's sarcoma-associated herpesvirus (KSHV) is a member of the gammaherpesvirus family. KSHV is the etiologic agent of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. The first open reading frame of the KSHV genome encodes a type 1 transmembrane glycoprotein named K1. K1 is structurally similar to the B-cell receptor (BCR), and its cytoplasmic tail contains an immunoreceptor tyrosine-based activation motif that can activate Syk kinase and the phosphatidylinositol 3-kinase (PI3K)/Akt pathway. Recent evidence suggests that receptor signaling occurs not only at the cell membrane, but from intracellular compartments as well. We have found that K1 is internalized in a clathrin-dependent manner, and efficient internalization is coupled to its signaling function. Once internalized, K1 traffics from the early endosome to the recycling endosome. Interestingly, blocking K1's activation of Syk and PI3K prevents K1 from internalizing. We have also found that blocking clathrin-mediated endocytosis prevents downstream signaling by K1. These results strongly suggest that internalization of K1 is intimately associated with normal signaling. When K1 internalization was examined in B lymphocytes, we found that K1 cointernalized with the BCR. Altogether, these results suggest that K1's signaling function is tightly coupled to its internalization.
Incomplete Protection against Simian Immunodeficiency Virus Vaginal Transmission in Rhesus Macaques by a Topical Antiviral Agent Revealed by Repeat Challenges
Authors: Ambrose Zandrea , Compton Lara , Piatak Michael , Lu Ding , Alvord W. Gregory , Lubomirski Mariusz S. , Hildreth James E. K. , Lifson Jeffrey D. , Miller Christopher J. , KewalRamani Vineet N.
Published: April 2008

The rising prevalence of human immunodeficiency virus type 1 (HIV-1) infection in women, especially in resource-limited settings, accentuates the need for accessible, inexpensive, and female-controlled preexposure prophylaxis strategies to prevent mucosal transmission of the virus. While many compounds can inactivate HIV-1 in vitro, evaluation in animal models for mucosal transmission of virus may help identify which approaches will be effective in vivo. Macaques challenged intravaginally with pathogenic simian immunodeficiency virus (SIV
mac251
) provide a model to preclinically evaluate candidate microbicides. 2-Hydroxypropyl-β-cyclodextrin (BCD) prevents HIV-1 and SIV infection of target cells at subtoxic doses in vitro. Consistent with these findings, intravaginal challenge of macaques with SIV
mac251
preincubated with BCD prevented mucosal transmission, as measured by plasma viremia and antiviral antibodies, through 10 weeks postchallenge. In an initial challenge, BCD applied topically prior to SIV
mac251
prevented intravaginal transmission of virus compared to controls (
P
< 0.0001). However, upon a second virus challenge following BCD pretreatment, the majority of the previously protected animals became infected. The mechanism through which animals become infected at a frequency similar to that of controls after prior exposure to BCD and SIV
mac251
in subsequent intravaginal virus challenges (
P
= 0.63), despite the potent antiviral properties of BCD, remains to be determined. These results highlight the unpredictability of antiviral compounds as topical microbicides and suggest that repeated exposures to candidate treatments should be considered for in vivo evaluation.
Fecundity, Atresia, and Egg Size of Captive Atlantic Cod (Gadus morhua) in Relation to Proximate Body Composition
Authors: Kjesbu O. S. , Klungsøyr J. , Kryvi H. , Witthames P. R. , Walker M. Greer
Published: April 2008

Captive Atlantic cod (Gadus morhua) were fed at four ration levels (starvation, maintenance, moderate, and excess) for periods of 6–9 mo prior to and during spawning. At the end of the experiment, water, protein, glycogen, and fat contents of the liver, white muscle, and ovary were estimated. The depletion of the white muscle and liver was related to oocyte maturation and in particular to the proportion of eggs spawned (PES). The influx of protein into the ovary, the mean hydrated egg diameter, and the egg dry weight all reached maximum values at 10% PES and subsequently declined. Mean vitellogenic oocyte diameter was small prior to spawning but rose to a maximum at PES = 10%. Cod with high condition factors produced more previtellogenic oocytes and used a larger fraction during vitellogenesis. Actual fecundity of specimens deprived of food during the spawning period was between 20 and 80% of the potential fecundity depending on the nutritional status of the fish. Intensity of atresia in moderate ration fish increased from 0% at PES = 0% to 33% at PES = 80%. Estimates of durations of α-atretic vitellogenic oocytes varied between 10 and 13 d at 8 °C assuming a spawning period of 50 d.
Seasonal Development of Ice Algae Near Chesterfield Inlet, N.W.T., Canada
Authors: Welch H. E. , Bergmann M. A. , Siferd T. D. , Amarualik P. S.
Published: April 2008

Ice algal chlorophyll a, (Chl), an estimator of biomass, was measured throughout the growing season (March–May) near Chesterfield Inlet on the northwest coast of Hudson Bay (63°30′N). The log10 transformation of Chl per square metre was a negative linear function of snow depth at any given date and location. Maximum biomass reached about 170 mg Chl∙m−2 over deep water but only one tenth as much over shallow water. This smaller standing crop was correlated with lower concentrations of nitrate in shallow water, postulated to result from nitrogen uptake by kelp. Ice-associated amphipods were abundant but had little detectable effect on the development of ice algal biomass. Ice algal Chl over deep water was predicted closely by the model developed for Resolute at 75°N, relating Chl to overlying snow depth and cumulative surface light. It appears that, where nutrients are adequate, ice algal biomass below first-year sea ice can be predicted for much of the Arctic from two variables, cumulative surface light and snow depth.
A Method for Estimating Gillnet Selectivity of Walleye (Stizostedion vitreum vitreum) in Muitimesh Multifilament Gill Nets in Lake Erie, and Its Application
Authors: Henderson Bryan A. , Wong Jonathan L.
Published: April 2008

A new method is described for adjusting gillnet catches for gear selectivity. Twelve years (1978–89) of walleye (Stizostedion vitreum vitreum) catches (n = 10 761) were pooled to derive frequency distributions of the ratios of fish girth and mesh perimeter for 11 mesh sizes. A gamma function was fitted to each of the 11 frequency distributions so that a selectivity curve could be derived for experimental gill nets used in Lake Erie, or any combination of meshes. An encounter model based on the swimming speed of walleye was used to estimate the probability of walleye encountering gill nets. Adjustments were made to walleye catches for both retention and encounter probabilities. Annual mortality and recruitment rates were compared for standardized and raw data from 1978 to 1989.