bluuebunny/crossref_metadata_2025 huggingface dataset:
Flutter Alleviation by Aeroelastic Tailoring of a Transonic Rotor Blade
Authors: Jeyaraman Sankarkumar , Purushothaman Kirubakaran , Bhat Ramaraja , Prasad Deshkulkarni Kishore
Published: February 2018

High asynchronous self-excited blade response was observed in a transonic first stage rotor during the evaluation of flutter stability in high forward speed conditions. This candidate baseline rotor stage is a highly loaded, snubber-less bladed-disc configuration mounted in an axial low pressure compressor with tip speed in the order of 400 m/s. During the tests, the high asynchronous blade response was measured by strain gages, tip timing system and unsteady blade pressure transducers, which were correlated with analytical predictions. To alleviate this problem, it was attempted to tailor the first rotor blade configuration alone by adhering to all the constraints such as geometric, aerodynamic matching, material selection and utilising the same dovetail root configuration in the existing disc configuration. While tailoring the rotor blade, the critical blade parameters such as axial chord, thickness to chord, stagger, camber, leading and trailing edge radius were iterated from hub to tip. In the tailored rotor blade, the first flexure mode frequency, 1F was improved by 45% whereas the separation between second flexure, 2F and torsion mode, 1T were improved by over 30% with 4.9% weight penalty. Using the one way fluid-structure interaction approach, the blade incidence variation for different inlet pressure conditions and aerodynamic damping were evaluated using energy method for both the configuration. Blade sets of the tailored configuration were manufactured and tested in a dedicated compressor test facility, where characteristics were generated from 70% to 100% corrected speeds. The rig tests confirmed the predicted compressor performance as well as the improvement of natural frequency using blade mounted strain gages for the tailored blade. Upon the verification in the test rig, the tailored rotor configuration was further fitted in the engine and tested up to 103.3% of its design speed. The blade experienced two different inlet total pressure conditions in the test rig and engine tests. The unsteady pressure transducers and blade tip timing sensors did not show any asynchronous response in the corrected speed range for the tailored configuration. Compared to the baseline rotor blade, this tailored rotor blade demonstrated the absence of asynchronous response in the fundamental flexure mode and also well correlated with the aerodynamic damping prediction by energy method. Using this correlation, it is further analytically demonstrated that the blade will have sufficient aerodynamic damping at higher forward speeds and also minimal incidence variation in these conditions.
A Comparison of Two Reduced Order Methods for Probabilistic Mistuning Investigations
Authors: Waldherr Christian U. , Vogt Damian M.
Published: February 2018

Slight variances in the manufacturing of rotating machinery can lead to significant changes in the structural dynamic behavior compared to the behavior of ideal cyclic periodic structures. Therefore it is necessary to consider deviations from the perfect cyclic periodic structures in the mechanical design process of rotating machinery. To minimize the effort of numerical calculations, the application of reduced order models is indispensable.

The objective of this paper is the comparison of two reduction methods which are not widespread in application of rotationally periodic structures. For the validation of the implemented methods, a generic model of a thin plate meshed with shell elements and a representative large size FE model of a radial turbine wheel are used. The first reduction method is called Improved Reduced System and is based on the classical Guyan reduction. The second reduction method is called SEREP method and is from a theoretical point of view closely related to the first method although the procedure to obtain the reduction basis is quite different. The results show for both test cases an excellent agreement between the reduced order models and the unreduced finite element model. Both reduction methods are also able to capture the phenomena of mode localization. It is also found that through the application of the reduced order methods the computation time can be reduced by two orders of magnitude. Based on the first reduction method, the statistical mistuning behavior is studied using the accelerated Monte Carlo simulation.
Effect of Rotor Tip Winglet on the Performance and Stability of a Transonic Axial Compressor
Authors: Shivaramaiah Subbaramu , Nagpurwala Quamber H. , Varpe Mahesh K. , Narahari H. K.
Published: February 2018

Winglets are plane surfaces with certain thickness and different shapes. Winglets are used in aircraft to reduce wing tip vortex which is created due to differential pressure in between pressure surface and suction surface. In transonic axial compressor, rotor tip leakage vortex interaction with shock layer and shroud boundary layer leads to total pressure loss and initiation of stall phenomenon. Effect of tip winglets are investigated in compressor rotor cascade. Cascade investigation shows that rotor tip winglet are able to reduce total pressure loss due to tip leakage flow and blade passage secondary flow. Cascade studies are performed with winglet on blade suction side, pressure side and combination of both. From cascade studies it is revealed that suction side winglet are aerodynamically better than pressure side and combined winglets. Owing to favorable results of tip winglet on compressor cascade performance, it was assumed that tip winglets would enhance overall performance of transonic compressor stage with rotating rotor. Results of present CFD simulations have predicted both positive and negative effects of winglets. Effect of different winglet configurations on pressure side and suction side of rotor blade tip are investigated to analyze the compressor stage overall performance. Rotor tip winglets are able to increase stage total pressure ratio compare to the baseline stage without winglet. Stage with winglets have shown better performance in choke region. Winglets are able to vary rotor blade loading from hub to tip region. Presence of winglet has shown ability to reduce to total pressure loss in trailing edge wake region. Stall margin is decreased in compressor stage with winglets due to more blockage towards trailing edge in tip region.
High Compressible Flow Through Jet Blast Deflector
Authors: Jaiswal Abhijeet , Dhoble Ashwin S. , Tidke D. J.
Published: February 2018

Jet blast impact on aerofoil blade of the deflector is studied which redirects the high energy exhaust of jet engine during the ground testing. The geometric model of aerofoils is designed with structured mesh around the aerofoil in rectangular domain generated in ICEM 16 software. The jet blast impact on aerofoil blade of the deflector is numerically simulated with SST k-ω model based on CFD theory. The fluid flow is high-speed compressible flow and flowing fluid air is considered as an ideal gas and also Sutherland’s law viscosity is applied to account for the dependence of molecular viscosity on temperature. Flow is taken as first order upwind and flux type is AUSM (Advection Upstream Splitting Method) to get an exact resolution of contact and shock discontinuities. The distribution of temperature, pressure, velocity and streamline of fluid flow is numerically simulated by FLUENT 16 software and layout of eddies generation behind aerofoil is generated in Tecplot 360 software. The coefficient of lift (Cl) and the coefficient of drag (Cd) are calculated to study the impact on aerofoil blade in horizontal and vertical direction. The result indicates that the method presented in this paper can analyze the fluid behavior on the complicated geometry of aerofoil blade that the flow between two adjacent aerofoil blades obtains a highly reliable simulation result. The value of lift force is negative i.e it holds the deflector towards the ground, so optimum balance between drag force and lifts force is obtained by simulating at a different angle of attack and pitch. Through CFD numerical simulation at a different angle of attack and pitch, the best result is obtained and conductive suggestions can be given for the adaptation of the JBD blade.
Vortex Induced Vibration of a Rotating Blade
Authors: Hoskoti Lokanna , Misra Ajay , Manchakattil Sucheendran Mahesh
Published: February 2018

The vortex-induced vibration (VIV) of a rotating blade is studied in this paper. Euler-Bernoulli beam equation and the nonlinear oscillator satisfying Van der Pol equation are used to model the rotating blade and vortex shedding, respectively. While the fluctuating lift due to vortex shedding acts on the blade and the blade is coupled with fluid through a linear inertial coupling, resulting in a fluid-structure interaction problem. The coupled equations are discretized by using modes which satisfy the Eigenvalue problem. The work attempts to understand the instabilities associated with the frequency lock-in phenomenon. The method of multiscale is used to obtain the frequency response equation and frequency bifurcation diagrams of the coupled system. They are obtained for the primary (1:1) resonance for different values of the coupling parameter. The stability of the solution is presented by examining the nature of the Eigenvalues of the Jacobian matrix.
A Comparison of Different Mesh Topology for Numerical Analysis of a Turbulent Liquid Jet
Authors: Sonawane Rohitkumar , Kumar Vivek , Nakod Pravin
Published: February 2018

Gas turbine engine combustors widely employ injection of liquid fuel in cross flow air as a fuel atomization process. Fuel atomization has a major impact on the efficiency, exit profile and emissions of the combustors. Since the quality of spray directly affects the performance of the combustors, it is important to understand a complex phenomenon of spray formation involving trajectory evolution, surface breakup, column fracture and dispersion of secondary droplets. There are several ways of analyzing spray formation which include experimental measurements, numerical analysis using Direct Numerical Simulation (DNS), a combination of output from Volume of Fluid (VOF) and empirical correlations or a hybrid Eulerian-Lagrangian multiscale method. In any of the numerical methods used for the analysis of the sprays, the mesh topology and resolution have a great impact on the accuracy of the predictions.

In the present work, evaluation of mesh topology particularly hexahedral and polyhedral meshes, is carried out to understand their effect on the accuracy of the spray prediction and explore the possibility of employing the polyhedral mesh for such a complex phenomenon. The mesh generation for polyhedral meshes is comparatively easier than hexahedral meshes and it has better control on the growth of the element size, resulting in lesser mesh count. A hybrid Eulerian-Lagrangian multiscale method developed earlier is used along with scale resolving turbulence model (Large Eddy Simulation) in this work. The test case considered for the analysis is taken from the experimental analysis done by Gopala et al. [2]. Momentum flux ratio of 10 and weber number of 1500 are selected for the present analysis. Simulation results from both the mesh topologies are compared with the experimental results for quantities like jet penetration length, Sauter mean diameter and droplet velocity profiles at different z/d locations. It is observed that both the mesh topologies considered, perform equally well and therefore, polyhedral mesh topology can be employed successfully for hybrid spray modeling.
A Study on the Nonlinear Dynamic Characteristics of Gas Turbine Engine Components
Authors: Murty Pilli Narayana , Kasina Lakshman , Bommisetty Kondaiah , Karri Sreenivas , Raghavan Kotur Srinivasan
Published: February 2018

Rotating as well as static components of aero engines such as rotors and casings must be capable of withstanding vibrations which arises from various engine order excitations. HCF is attributed as one of the major failures due to its high crack propagation rate. The tolerances to vibration have become a key point to avoid resonance in operating range. Analytical predictions of individual components gives better accuracy and good agreement with test data. However, when the components are assembled, the accuracy of analyses can considerably depreciate since models describing stiffness and friction properties of joints are linearized. In such conditions proper predictions of dynamic response becomes difficult and may lead to under prediction or over prediction of dynamic response.

A nonlinear analysis is required to study the influence of joints flexibility on dynamic response. In this paper different nonlinear joint models are investigated to assess the dynamic behavior of the contact interface in terms of slipping and sticking contact parameters. The study shows significant changes over dynamic characteristics when compared to linear analysis. From this study, it is evident that nonlinear behavior of the contact in dynamic analysis phase due to slip and separation plays vital role over the dynamic characteristics of the component. This study emphasizes to consider physical behavior of joints in dynamic analysis to avoid catastrophic HCF failures.
Prediction of Soot Formation Trends in Turbulent Kerosene-Air Diffusion Jet Flames With Elevated Operating Pressure
Authors: Nakod Pravin , Patwardhan Saurabh , Verma Ishan , Orsino Stefano
Published: February 2018

Emission standard agencies are coming up with more stringent regulations on soot, given its adverse effect on human health. It is expected that Environmental Protection Agency (EPA) will soon place stricter regulations on allowed levels of the size of soot particles from aircraft jet engines. Since, aircraft engines operate at varying operating pressure, temperature and air-fuel ratios, soot fraction changes from condition to condition. Computation Fluid Dynamics (CFD) simulations are playing a key role in understanding the complex mechanism of soot formation and the factors affecting it.

In the present work, soot formation prediction from numerical analyses for turbulent kerosene-air diffusion jet flames at five different operating pressures in the range of 1 atm. to 7 atm. is presented. The geometrical and test conditions are obtained from Young’s thesis [1]. Coupled combustion-soot simulations are performed for all the flames using steady diffusion flamelet model for combustion and Mass-Brookes-Hall 2-equation model for soot with a 2D axisymmetric mesh. Combustion-Soot coupling is required to consider the effect of soot-radiation interaction. Simulation results in the form of axial and radial profiles of temperature, mixture fraction and soot volume fraction are compared with the corresponding experimental measured profiles. The results for temperature and mixture fraction compare well with the experimental profiles. Predicted order of magnitude and the profiles of the soot volume fraction also compare well with the experimental results. The correct trend of increasing the peak soot volume fraction with increasing the operating pressure is also captured.
A Study on Performance of Aero-Engine With Fluidic Thrust Vector Nozzle
Authors: Xiao-bo Zhang , Zhan-xue Wang , Jing-wei Shi
Published: February 2018

Shock Vector Controlling (SVC) nozzle is one of the most effective ways to obtain the thrust vector for the advanced engine. The SVC nozzle has the advantages of simple structure, light weight and fast response. Numerous analytical, numerical and experimental studies have been carried out on SVC nozzle in recent years. While these studies mainly focus on the nozzle and ignore the influence between SVC nozzle and engine. In fact, the secondary flows of fluidic thrust vectoring nozzle are all extracted from the engine fan or high pressure compressor, no matter it is based on SVC or others. The extraction and injection of the secondary flow both influence the components matching and engine performance. And the mass flow and pressure of secondary flow are constrained by engine working condition in turn. So the SVC nozzle should be installed in the engine environment for evaluation.

The influence of SVC nozzle secondary flow on engine thermodynamic cycle and performance is in two major ways. First, when the secondary flow extracts from the fan or HPC, the operating point of the engine will change. It results in the thermodynamic parameters at each engine stations and the performance of engine change. The reason for this change is that the bleeding of secondary flow broke the mass flow balance equations between the engine components. Second, the injection of secondary flow in the expansion section of nozzle also leads to engine performance change, while the engine operating point remains normal.

The characteristic of certain SVC nozzle is obtained by computational fluid dynamics method. Then the Response Surface Method (RSM) model based on the design of experiment is employed to build the relations of performance parameters and design variables of SVC nozzle. Combining basic engine performance simulation model with SVC nozzle RSM model, the model for engine with SVC nozzle is built. To evaluate the performance of the engine with SVC nozzle, the conceptual design of double bypass variable cycle engine with SVC nozzle is given. The influence of the secondary flow extracting from the fan outlet, CDFS outlet and the first stage of HPC is discussed. And its performances such as vector angle, thrust coefficient, thrust and specific fuel consumption are obtained by employing the engine simulation model built by this paper.
Cold Blade Profile Generation Methodology for Compressor Rotor Blades Using FSI Approach
Authors: Purushothaman Kirubakaran , Jeyaraman Sankar Kumar , Pratap Ajay , Prasad Deshkulkarni Kishore
Published: February 2018

This paper describes a methodology for obtaining correct blade geometry of high aspect ratio axial compressor blades during running condition taking into account of blade untwist and bending. It discusses the detailed approach for generating cold blade geometry for axial compressor rotor blades from the design blade geometry using fluid structure interaction technique. Cold blade geometry represents the rotor blade shape at rest, which under running condition deflects and takes a new operating blade shape under centrifugal and aerodynamic loads. Aerodynamic performance of compressor primarily depends on this operating rotor blade shape. At design point it is expected to have the operating blade shape same as the intended design blade geometry and a slight mismatch will result in severe performance deterioration. Starting from design blade profile, an appropriate cold blade profile is generated by applying proper lean and pre-twist calculated using this methodology. Further improvements were carried out to arrive at the cold blade profile to match the stagger of design profile at design operating conditions with lower deflection and stress for first stage rotor blade. In rear stages, thermal effects will contribute more towards blade deflection values. But due to short blade span, deflection and untwist values will be of lower values. Hence difference between cold blade and design blade profile would be small. This methodology can especially be used for front stage compressor rotor blades for which aspect ratio is higher and deflections are large.
Necessity of Kinematic Strain Hardening in Simulating Impact Events
Authors: Kirloskar Sharang , Singh Gurmeet , Kumar Avinash
Published: February 2018

Impact events are very high speed and short duration events. Experimental analysis of such events tends to be extremely expensive and challenging to study because of the apparatus and measurement systems required to capture the event. Due to this, impact events are studied extensively through simulations. The ability to simulate these events is a dictating factor for developing better and more efficient designs.

Traditionally, loads occurring due to impact events are assumed to monotonically increase and hence pure isotropic strain hardening is sufficient to model the material behavior. However, this assumption doesn’t hold true for all impact events. When the loads caused by an impact do not monotonically increase but instead oscillate causing tension and compression cycles, pure isotropic hardening could lead to unrealistic results.

In this work, different strain hardening rules are studied and analyzed for a plate under impact loading. The process to obtain a parameter which sets a realistic combination of isotropic and kinematic strain hardening rules is demonstrated and discussed. Limitations of the existing practice of using isotropic hardening in impact loading cases are studied. An alternative approach to accommodate the kinematic hardening rule into material models using LS-DYNA, a finite element solver, is discussed.
Simulation Study of Transient Responses of Laminated Composite Sandwich Plate
Authors: Katariya Pankaj , Panda Subrata Kumar
Published: February 2018

In this article, the transient responses of the laminated composite sandwich plate structure are obtained numerically using the commercial finite element package to reduce the computational cost without hampering the accuracy. The plate structure is discretized using the available shell element (SHELL281) from ANSYS library. In order to compute the responses, an ANSYS parametric design language code has been developed based on the finite element steps and Newmark integration technique. The model accuracy and stability have been checked and few numerical examples have been solved. Finally, the effect of different parameters like side-to-thickness ratios, core-to-face thickness ratios, and lamination schemes are computed to show the necessary influences on the time-dependent deflection of the laminated composite sandwich structure.
Dynamic Analysis of Active Vibration Absorber by Time Delay Acceleration Feedback Using Higher Order Method of Multiple Scales
Authors: Mohanty S. , Dwivedy S. K.
Published: February 2018

In the present work, analysis of a nonlinear active vibration absorber is carried out by time delay acceleration feedback. The primary system consisting of spring, mass and damper is subjected to multi harmonic and parametric excitation. It is proposed to reduce the vibration of both the primary system and the absorber by attaching a lead zirconate titanate (PZT) stack actuator connected in series with a spring in absorber configuration which act as an active vibration absorber. Due to the external excitation on the primary mass strain is developed in the PZT sensor, which produces voltage and this voltage converted to a counter acting force by the PZT actuator to suppress the vibration of the primary system. Second order method of multiple scales (MMS) is used to obtain approximate solution of the system to study frequency responses for simultaneous primary resonance, principal parametric and 1:1 internal resonance conditions. The analysis is performed for the mass ratio of 0.01 between the absorber and the primary mass.
Characterization of Ti-6Al-4V Alloy Modified by Plasma Nitriding Process
Authors: Bhavsar Vaibhav N. , Jha Jyoti Shankar , Jhala Ghanshyamsinh , Joseph Alphonsa , Mishra Sushil , Tewari Asim
Published: February 2018

Titanium alloys are gaining widespread acceptance in aerospace industry because of its high specific strength, corrosion resistance and good fatigue properties. Dovetails of the compressor blades, gears, splines etc. are some aerospace components that fail through premature fatigue crack initiation and propagation under the action of wear, fatigue and fretting fatigue. The fretting failure originates from the surface or near surface and leads to the damage of the components. Therefore the surface of components can be modified to improve the tribological performance by plasma nitriding which improve the titanium alloy by forming layer of hard TiN and Ti2N phases on surface. Plasma nitriding of titanium alloys has several advantages over gas and liquid nitriding methods where the phase formation and the depth of nitriding can be controlled. In this study Ti-6Al-4V alloy is taken as surrogate material for gas turbine application and its surface is modified by plasma nitriding at three different temperatures 500, 700 and 800 °C with N2:H2 ratio of 4:1 at 5 mbar pressure for 5 hrs. It is observed from XRD that at 500 and 700 °C temperature, nucleation of ε-Ti2N and δ-TiN started and complete titanium nitride layer formed at 800 °C. Nucleation and growth mechanism was studied by surface and cross section SEM analysis. Nitride layer of around 0.5 μm with ε-Ti2N and around 2 μm thick of both ε-Ti2N and δ-TiN phases were formed at 700 and 800 °C respectively. It is observed that the surface roughness increases with increasing the temperature for plasma nitriding. Vickers microhardness (HV0.1) is observed to be increased from 393.7 HV to 1016.4 HV by plasma nitriding at 800 °C.
Design and Analysis of Radial Turbine for Turbocharger Application
Authors: Desikan Bharathan Raghavan , Rajendran David John , Kapil Sharad , Ramana Murty Seepana Venkata , Kishore Prasad Deshkulkarni
Published: February 2018

Turbochargers are used in internal combustion engines to increase their volumetric efficiency and power. Turbochargers consist of a centrifugal compressor driven by a radial turbine. Radial turbines convert the excess kinetic energy in the exhaust gases to power. Vane less radial turbine consists of a volute and a turbine wheel. It is preferred because of its low cost, robustness and good off-design performance. In this study, a radial turbine wheel and volute are designed to meet the power and efficiency requirements. A number of trials are carried out, and the design, which gives the necessary performance and meets the customer requirements, is chosen. The design is analyzed using a validated 3D Navier-Stokes (NS) solver, viz. ANSYS-CFX software at both design and off-design conditions and turbine characteristics are generated.
Performance Optimization of Trapezium Rib Parameters Using Response Surface Methodology
Authors: Sharma Naveen , Sharma Vaibhav , Tariq Andallib
Published: February 2018

In the present work, transient liquid crystal thermography (LCT) has been used for capturing the temperature field as well as the local heat transfer distribution inside a rectangular duct. Experiments have been carried out in an open loop airflow system at a Reynolds number (based on the channel hydraulic diameter) of 58850 and for rib height to channel hydraulic diameter ratio of 0.125. This investigation emphases headed for assessing the potential impact of design parameters such as chamfering angle and rib pitch to height ratio of the trapezium ribbed rectangular duct on the thermo-hydraulic performances, which forms the basis of analysis while using response surface methodology (RSM). The chamfering angle has been varied from 0 to 20° in a step of 5°, while the rib pitch to height ratio is varied from 8 to 12 in a step of 2. The quadratic model generated by RSM is used to predict the optimal performance parameters. The results show that different geometrical parameters have to be considered simultaneously in order to improve the performance of ribbed-duct. Eventually, based on this analysis, the optimum levels of design parameters for trapezium rib corresponding to the highest augmentation Nusselt number, the lowest friction factor, and the highest thermo-hydraulic performance have been determined. Finally, the desired correlations for all performance parameters have been developed using RSM. The comparison of predicted values with the experimental values has been carried out, which is found to be in harmony with the experimental values in the uncertainty range of ±5%., which are found to predict the performance parameters with reasonably good accuracy.
Three-microphone probe bias errors for acoustic intensity and specific acoustic impedance
Authors: Lawrence Joseph S. , Whiting Eric B. , Gee Kent L. , Rasband Reese D. , Neilsen Tracianne B. , Sommerfeldt Scott D.
Published: February 2018

In acoustic intensity estimation, adding a microphone at the probe center removes errors associated with pressure averaging. Analytical bias errors are presented for a one-dimensional, three-microphone probe for active intensity, reactive intensity, and specific acoustic impedance in a monopole field. Traditional estimation is compared with the Phase and Amplitude Gradient Estimator (PAGE) method; the PAGE method shows an increased bandwidth for all three quantities. The two- and three-microphone methods are compared experimentally, showing reduced bias errors with three-microphone PAGE for active and reactive intensity, whereas using two microphones is preferred for specific acoustic impedance.
Antifungal Susceptibility of the Aspergillus viridinutans Complex: Comparison of Two
In Vitro
Methods
Authors: Lyskova Pavlina , Hubka Vit , Svobodova Lucie , Barrs Vanessa , Dhand Navneet K. , Yaguchi Takashi , Matsuzawa Tetsuhiro , Horie Yoshikazu , Kolarik Miroslav , Dobias Radim , Hamal Petr
Published: February 2018

Cryptic species of
Aspergillus fumigatus
, including the
Aspergillus viridinutans
species complex, are increasingly reported to be causes of invasive aspergillosis. Their identification is clinically relevant, as these species frequently have intrinsic resistance to common antifungals. We evaluated the susceptibilities of 90 environmental and clinical isolates from the
A. viridinutans
species complex, identified by DNA sequencing of the calmodulin gene, to seven antifungals (voriconazole, posaconazole, itraconazole, amphotericin B, anidulafungin, micafungin, and caspofungin) using the reference European Committee on Antimicrobial Susceptibility Testing (EUCAST) method. The majority of species demonstrated elevated MICs of voriconazole (geometric mean [GM] MIC, 4.46 mg/liter) and itraconazole (GM MIC, 9.85 mg/liter) and had variable susceptibility to amphotericin B (GM MIC, 2.5 mg/liter). Overall, the MICs of posaconazole and the minimum effective concentrations of echinocandins were low. The results obtained by the EUCAST method were compared with the results obtained with Sensititre YeastOne (YO) panels. Overall, there was 67% agreement (95% confidence interval [CI], 62 to 72%) between the results obtained by the EUCAST method and those obtained with YO panels when the results were read at 48 h and 82% agreement (95% CI, 78 to 86%) when the results were read at 72 h. There was a significant difference in agreement between antifungals; agreement was high for amphotericin B, voriconazole, and posaconazole (70 to 86% at 48 h and 88 to 93% at 72 h) but was very low for itraconazole (37% at 48 h and 57% at 72 h). The agreement was also variable between species, with the maximum agreement being observed for
A. felis
isolates (85 and 93% at 48 and 72 h, respectively). Elevated MICs of voriconazole and itraconazole were cross-correlated, but there was no correlation between the other azoles tested.
Dissociation between Iron and Heme Biosyntheses Is Largely Accountable for Respiration Defects ofShewanella oneidensis furMutants
Authors: Fu Huihui , Liu Lulu , Dong Ziyang , Guo Shupan , Gao Haichun
Published: February 2018

Iron, a major protein cofactor, is essential for most organisms but can simultaneously be toxic. Iron homeostasis thus has to be effectively maintained under a range of iron regimes. This may be particularly true withShewanella oneidensis, a representative of dissimilatory metal-reducing bacteria (DMRB), which are capable of respiring a variety of chemicals as electron acceptors (EAs), including iron ores. Although iron respiration and its regulation have been extensively studied in this bacterium, how iron homeostasis is maintained remains largely unknown. Here, we report that the loss of the iron homeostasis master regulator Fur negatively affects the respiration of all EAs tested. This defect appears mainly to be a result of reduced cytochromec(cytc) production, despite a decrease in the expression of reductases that are under the direct control of Fur. We also show thatS. oneidensisFur interacts with canonical Fur box motifs in F-F-x-R configuration rather than the palindromic motif proposed before. Thefurmutant has lowered total iron and increased free iron contents. Under iron-rich conditions, overproduction of the major iron storage protein Bfr elevates the total iron levels of thefurmutant over those of the wild-type but does not affect free iron levels. Intriguingly, such an operation only marginally improves cytcproduction by affecting hemebbiosynthesis. It is established that iron dictates hemeb/cytcbiosynthesis inS. oneidensisfur+strains, but thefurmutation annuls the dependence of hemeb/cytcbiosynthesis on iron. Overall, our results suggest that Fur has a profound impact on the iron homeostasis ofS. oneidensis, through which many physiological processes, especially respiration, are transformed.

IMPORTANCEIron reduction is a signature ofS. oneidensis, and this process relies on a large number of typeccytochromes, whichper seare iron-containing proteins. Thus, iron plays an essential and special role in iron respiration, but to date, the nature of iron metabolism and regulation of the bacterium remains largely unknown. In this study, we investigated impacts of Fur, the master regulator of iron homeostasis, on respiration. The loss of Fur causes a general defect in respiration, a result of impaired cytcproduction rather than specific regulation. Additionally, thefurmutant is unresponsive to iron, resulting in imbalanced iron homeostasis and dissociation between iron and cytcproduction. These findings provide important insights into the iron biology of DMRB.
Targeting the HUβ Protein Prevents Porphyromonas gingivalis from Entering into Preexisting Biofilms
Authors: Rocco Christopher J. , Bakaletz Lauren O. , Goodman Steven D.
Published: February 2018

The oral cavity is home to a wide variety of bacterial species, both commensal, such as various streptococcal species, and pathogenic, such asPorphyromonas gingivalis, one of the main etiological agents of periodontal disease. Our understanding of how these bacteria ultimately cause disease is highly dependent upon understanding how they coexist and interact with one another in biofilm communities and the mechanisms by which biofilms are formed. Our research has demonstrated that the DNABII family of DNA-binding proteins are important components of the extracellular DNA (eDNA)-dependent matrix of bacterial biofilms and that sequestering these proteins via protein-specific antibodies results in the collapse of the biofilm structure and release of the resident bacteria. While the high degree of similarity among the DNABII family of proteins has allowed antibodies derived against specific DNABII proteins to disrupt biofilms formed by a wide range of bacterial pathogens, the DNABII proteins ofP. gingivalishave proven to be antigenically distinct, allowing us to determine if we can use anti-P. gingivalisHUβ antibodies to specifically target this species for removal from a mixed-species biofilm. Importantly, despite forming homotypic biofilmsin vitro,P. gingivalismust enter preexisting biofilmsin vivoin order to persist within the oral cavity. The data presented here indicate that antibodies derived against theP. gingivalisDNABII protein, HUβ, reduce by half the amount ofP. gingivalisorganisms entering into preexisting biofilm formed by four oral streptococcal species. These results support our efforts to develop methods for preventing and treating periodontal disease.

IMPORTANCEPeriodontitis is one of the most prevalent chronic infections, affecting 40 to 50% of the population of the United States. The root cause of periodontitis is the presence of bacterial biofilms within the gingival space, withPorphyromonas gingivalisbeing strongly associated with the development of the disease. Periodontitis also increases the risk of secondary conditions and infections such as atherosclerosis and infective endocarditis caused by oral streptococci. To induce periodontitis,P. gingivalisneeds to incorporate into preformed biofilms, with oral streptococci being important binding partners. Our research demonstrates that targeting DNABII proteins with an antibody disperses oral streptococcus biofilm and preventsP. gingivalisentry into oral streptococcus biofilm. These results suggest potential therapeutic treatments for endocarditis caused by streptococci as well as periodontitis.
Evaluation of the Diagnostic Accuracy of Two Immunochromatographic Tests Detecting Campylobacter in Stools and Their Role in Campylobacter Infection Diagnosis
Authors: Bessède Emilie , Asselineau Julien , Perez Paul , Valdenaire Guillaume , Richer Olivier , Lehours Philippe , Mégraud Francis
Published: February 2018

The detection of campylobacters in stools is performed essentially by culture, but this technique has a low sensitivity. New detection methods are now available. Among them, immunochromatography tests (ICTs) are very attractive in that they offer a result within 15 min. However, previous studies suggest that these tests have a relatively low specificity. The objective of this study was to evaluate the performance of these tests. During the study period, all patients who consulted the emergency units and had a stool culture were included. Their stool samples were tested with two ICTs, Ridaquick Campylobacter and Immuno
Card
STAT! Campy. Stools were also tested by a home-made PCR and two commercially available enzyme-linked immunosorbent assays (ELISAs) when one of the ICTs was positive. The composite reference standard (CRS) was defined as positive if the culture was positive or, in case of a negative culture, if the PCR and one of the ELISAs were positive simultaneously. Three hundred and five patients were included. Among the 50 positive specimens with Ridaquick Campylobacter, 47 were considered true positives by the CRS, corresponding to a positive predictive value (PPV) of 94.0%. Among the 52 positive specimens with Immuno
Card
STAT! Campy, 44 were considered true positives by the CRS, corresponding to a PPV of 84.6%. The negative predictive values were estimated at 94.9 and 92.4% for the Ridaquick Campylobacter and Immuno
Card
STAT! Campy tests, respectively. ICTs appear to be very efficient and allow a very rapid detection of campylobacters, which is important for treating early campylobacter infections with an adapted antibiotherapy.
Superinfection Exclusion between Two High-Risk Human Papillomavirus Types during a Coinfection
Authors: Biryukov Jennifer , Meyers Craig
Published: February 2018

Superinfection exclusion is a common phenomenon whereby a single cell is unable to be infected by two types of the same pathogen. Superinfection exclusion has been described for various viruses, including vaccinia virus, measles virus, hepatitis C virus, influenza A virus, and human immunodeficiency virus. Additionally, the mechanism of exclusion has been observed at various steps of the viral life cycle, including attachment, entry, viral genomic replication, transcription, and exocytosis. Human papillomavirus (HPV) is the causative agent of cervical cancer. Recent epidemiological studies indicate that up to 50% women who are HPV positive (HPV
+
) are infected with more than one HPV type. However, no mechanism of superinfection exclusion has ever been identified for HPV. Here, we show that superinfection exclusion exists during a HPV coinfection and that it occurs on the cell surface during the attachment/entry phase of the viral life cycle. Additionally, we are able to show that the minor capsid protein L2 plays a role in this exclusion. This study shows, for the first time, that superinfection exclusion occurs during HPV coinfections and describes a potential molecular mechanism through which it occurs.

IMPORTANCE
Superinfection exclusion is a phenomenon whereby one cell is unable to be infected by multiple related pathogens. This phenomenon has been described for many viruses and has been shown to occur at various points in the viral life cycle. HPV is the causative agent of cervical cancer and is involved in other anogenital and oropharyngeal cancers. Recent epidemiological research has shown that up to 50% of HPV-positive individuals harbor more than one type of HPV. We investigated the interaction between two high-risk HPV types, HPV16 and HPV18, during a coinfection. We present data showing that HPV16 is able to block or exclude HPV18 on the cell surface during a coinfection. This exclusion is due in part to differences in the HPV minor capsid protein L2. This report provides, for the first time, evidence of superinfection exclusion for HPV and leads to a better understanding of the complex interactions between multiple HPV types during coinfections.
Peripheral T-cell lymphoma mimicking classic Hodgkin’s lymphoma in a patient presenting with fevers of unknown origin
Authors: Butler Caitlin , Skelton William Paul , Patel Arpan , Mahtta Dhruv , Zhuang Yi , Cherabuddi Kartik , Shah Kairav , Markham Merry
Published: February 2018

A 52-year-old man presented to our hospital for further workup of fever of unknown origin after an extensive workup at an outside hospital had failed to reveal a diagnosis. At the outside hospital, he underwent excisional biopsy of the left supraclavicular lymph node, which showed non-necrotising granulomatous changes, and a bone marrow biopsy which showed a normocellular marrow. He was discharged without a diagnosis with recommendations to present to a tertiary hospital. During his admission, his hospital course was complicated by new direct hyperbilirubinaemia and eosinophilia, prompting liver and skin biopsies which showed CD30+ and CD3+ cells. He subsequently underwent left axillary lymph node biopsy, which was reported as ‘classic Hodgkin’s lymphoma’. With worsening lab values and T cells noted on liver and skin biopsies, excisional lymph node biopsy was sent to the National Institute of Health, where it was confirmed patient had peripheral T cell lymphoma.
Progressive change in peripapillary atrophy in myopic glaucomatous eyes
Authors: Song Min Kyung , Sung Kyung Rim , Shin Joong Won , Kwon Junki , Lee Ji Yun , Park Ji Min
Published: February 2018

Aim

To evaluate the progressive change in peripapillary atrophy (PPA) according to its shape and to explore the relationship between PPA progression and glaucoma worsening in myopic eyes.

Methods

A total of 159 eyes of 159 patients with myopic (axial length (AXL) >24 mm) glaucoma (mean follow-up 4.4 years, 35 eyes with minimal PPA, 40 concentric-type PPA eyes (>270° around the optic disc) and 84 eccentric-type PPA eyes (<270°)) were included. Sequential stereoscopic colour optic disc photographs were evaluated to qualitatively determine PPA progression. Factors associated with PPA progression were explored by Cox proportional hazard modelling in each PPA group.

Results

Patients with concentric PPA were older than patients with eccentric PPA (54.1±11.7 vs 44.1±11.7 years; P<0.001), and AXL was longer in the eccentric group than in the other groups (25.54±1.68 vs 25.28±1.53 vs 26.41±1.29 mm; P<0.001). Twenty-six eyes (65%) in the concentric group and 36 eyes (42.9%) in the eccentric group showed PPA progression. Older age (hazard ratio (HR) 1.059, P=0.008), worse baseline visual field mean deviation (HR 0.857, P=0.009) and greater baseline PPA area (HR 1.000, P=0.012) were associated with PPA progression in the concentric type. Glaucoma progression (HR 3.690, P=0.002) and longer AXL (HR 1.521, P=0.002) were associated with PPA progression in the eccentric type.

Conclusions

Relationship between glaucoma worsening and PPA progression was strongest in myopic glaucomatous eyes with eccentric type PPA.
Sociodemographic differences in symptom severity and duration among women referred to secondary care for menorrhagia in England and Wales: a cohort study from the National Heavy Menstrual Bleeding Audit
Authors: Kiran Amit , Geary Rebecca Sally , Gurol-Urganci Ipek , Cromwell David A , Bansi-Matharu Loveleen , Shakespeare Judy , Mahmood Tahir , van der Meulen Jan
Published: February 2018

Objective

To examine symptom severity and duration at time of referral to secondary care for heavy menstrual bleeding (HMB) by socioeconomic deprivation, age and ethnicity

Design

Cohort analysis of data from the National HMB Audit linked to Hospital Episode Statistics data.

Setting

English and Welsh National Health Services (secondary care): February 2011 to January 2012.

Participants

15 325 women aged 18–60 years in England and Wales who had a new referral for HMB to a gynaecology outpatient department

Methods

Multivariable linear regression to calculate adjusted differences in mean symptom severity and quality of life scores at first outpatient visit. Multivariable logistic regression to calculate adjusted ORs. Adjustment for body mass index, parity and comorbidities.

Primary outcome measures

Mean symptom severity score (0=best, 100=worst), mean condition-specific quality of life score (0=worst, 100=best) and symptom duration (≥1 year).

Results

Women were on average 42 years old and 12% reported minority ethnic backgrounds. Mean symptom severity and condition-specific quality of life scores were 61.8 and 34.7. Almost three-quarters of women (74%) reported having had symptoms for ≥1 year. Women from more deprived areas had more severe symptoms at their first outpatient visit (difference −6.1; 95% CI−7.2 to −4.9, between least and most deprived quintiles) and worse condition-specific quality of life (difference 6.3; 95% CI 5.1 to 7.5). Symptom severity declined with age while quality of life improved.

Conclusions

Women living in more deprived areas reported more severe HMB symptoms and poorer quality of life at the start of treatment in secondary care. Providers should examine referral practices to explore if these differences reflect women’s health-seeking behaviour or how providers decide whether or not to refer.