bluuebunny/crossref_metadata_2025 huggingface dataset:
Practical Aspects of Fatigue Crack Growth in Aero-GTE Applications
Authors: Lenets Youri N.
Published: December 2013

In an attempt to mitigate future accidents and to harmonize the U.S. and European engine certification requirements, the Federal Aviation Administration (FAA) has recently revised engine certification standards related to the design of engine life-limited parts, also called “critical parts” in European regulations. The updated rule introduces new requirements for engine manufacturers to conduct damage tolerance assessment of all rotating structural parts as well as major static structural parts whose primary failure is likely to result in hazardous engine effects.

Several practical aspects of such damage tolerance assessment, centered on the fatigue crack growth (FCG) testing of aero-GTE materials, are considered in the following. They include, but are not limited to the discussion of the appropriate test specimen geometry and conditions to characterize the behavior of relatively small semi-elliptical cracks emanating from highly stressed surface locations, and fundamental features of the test data analysis. Two novel test approaches — compression pre-cracking and focused ion beam notching — are discussed in detail and associated methodologies developed to study slow FCG and small crack anomalies, respectively, are illustrated by examples.
Development of a Generalized LCF-TMF Lifing Model for a Nickel-Base Superalloy
Authors: Buchholz Björn , Gampe Uwe , Beck Tilmann
Published: December 2013

The growing share of power generation from volatile sources such as wind and photovoltaics requires fossil fuel fired power generation units be available and capable of high load flexibility to adjust to the changing capacity of the electrical grid. Additionally, back-up units with quick start capability and energy storage technologies are needed to fill the power shortfall when volatile sources are not available. Gas turbine and combined-cycle gas and steam turbine power plants are able to meet these demands. However, safe component design for improved cycling capability, combined with optimum utilization of material regarding its mechanical properties, requires design procedures and lifing models for the complex loadings resulting from this increased volatility of power demand. Since hot gas path components like turbine blades and vanes are highly stressed by cyclic thermal and mechanical loadings, resulting Thermo-Mechanical Fatigue (TMF), life prediction models such as the classic strain-life Coffin-Manson-Basquin method do not capture the influences of thermal cycling satisfyingly. Advanced TMF prediction models are thus necessary to accurately predict the durability of hot section components.

This paper addresses life prediction of the Nickel-base superalloy René 80 at elevated temperature for various loading conditions. For this purpose, isothermal Low Cycle Fatigue (LCF) and corresponding TMF tests, with various temperature ranges and thermal-mechanical phase shifts, have been performed. On this basis, a systematic approach has been developed which allows assessing the key influences on TMF life. Moreover, a generalized model for fatigue has been derived, which has the potential to predict TMF life on the basis of LCF data. The knowledge gained from the model development allows an improved life prediction and better utilization of the material capabilities. Additionally, the required number of material tests for a general insight in the materials behaviour can be reduced significantly.
Combined Effects of Both Axial Gap and Blade Count Ratio on the Unsteady Forces of a Steam Turbine Stage
Authors: Chen Tie , Patel Kush , Millington Peter
Published: December 2013

Rotating blades of steam turbines are subjected to unsteady forces due to the presence of both wakes and potential field from the upstream stationary blades. These forces are strongly influenced by both axial gap and blade count ratio. The combined effects of these parameters are studied for 120 scenarios covering the normal design space. The calculated unsteady forces are transformed into harmonic components using a Fourier transform. Each harmonic component is correlated to both axial gap and blade count ratio to provide guidance for preliminary blade design. This study uses an in-house non-linear time marching CFD code TF3D-VIB, which adopts a Shape Correction method to manage an arbitrary blade count ratio using a single passage. Consequently it is one-order more efficient than a conventional multiple passage method.
A Novel Concentrated Solar Power System Hybrid Trough and Tower Collectors
Authors: Han Wei , Jin Hongguang , Lin Rumou , Wang Yalong , Su Jianfeng
Published: December 2013

Global warming, fossil fuel shortage, and environment pollution are a growing concern on concentrated solar power (CSP) because of the largest amount of energy resource. Parabolic troughs and power towers are state-of-the-art commercial technologies. The primary drawbacks of current CSP technologies are low thermal efficiency and high investment cost. In the current study, a novel CSP system is proposed. This system integrates a solar parabolic trough power system and a solar tower power system. In this hybrid system the tower collectors with high concentration ratio generate high-temperature heat at 574 °C, and the trough collectors with a relative low concentration ratio generate mid-temperature heat at 390 °C. The mid-temperature heat from trough collectors generates steam up to 370 °C. The steam is then superheated and reheated by the high-temperature heat generated by the tower collectors. Compared with an individual solar trough plant, the temperatures of the primary and reheated steam are increased from individual trough plant’s 370 °C in the individual trough plant to 535 °C in the hybrid system, thus increasing the conversion efficiency from heat to power. Based on the simulation results, the annual thermal efficiency of the hybrid system can reach 15.84%, higher by 1.77 and 2.29 percentage points compared with those of the individual solar trough and tower plants. The electricity generation cost of the new system can be decreased by 7.5% to 12.4% compared with that of the individual trough or tower plants. The results obtained in the present study provide a new approach for utilizing solar energy more efficiently and more economically.
Experimental Investigation on the Forced Response of a Dummy Counter Rotating Turbine Stage With Friction Damping
Authors: Berruti Teresa , Maschio Vanni , Calza Paolo
Published: December 2013

The paper shows the results of the experimental activity about the dynamics of a stage of a counter rotating turbine of an open rotor architecture engine. The tests here presented explore the dynamic behavior of a simplified counter-rotating turbine stage. The test results show the dynamic behavior of a counter rotating turbine stage and highlight the importance of the presence of dry friction for vibration damping.
Simulation of Deep Surge in a Turbocharger Compression System
Authors: Dehner Rick , Selamet Ahmet , Keller Philip , Becker Michael
Published: December 2013

Large-amplitude deep surge instabilities are studied in a turbocharger compression system with a one-dimensional engine simulation code. The system consists of an upstream compressor duct open to ambient, a centrifugal compressor, a downstream compressor duct, a large plenum, and a throttle valve exhausting to ambient. As the compressor mass flow rate is reduced below the peak pressure ratio for a given speed, mild surge oscillations occur at the Helmholtz resonance of the system, and a further reduction in flow rate results in deep surge considerably below the Helmholtz resonance. At the boundary with mild surge, the deep surge cycles exhibit, for the particular system considered, a long cycle period containing four distinct flow phases, including quiet (stable), instability growth (mild surge), blowdown (reversal), and recovery. Further reductions in flow rate decrease the deep surge cycle period, eliminate the quiet flow phase, and shorten the duration of the instability growth phase. Simulated oscillations of nondimensional flow rate, pressure, and speed parameters show good agreement with the experimental results available in literature, in terms of deep surge cycle flow phases along with the amplitude and frequency of the resulting fluctuations. The predictions illustrate that the quiet and instability growth phases, exhibited by this compression system, disappear as the plenum volume is substantially reduced.
An Efficient Scheme for Describing Airfoils Using Non-Uniform Rational B-Splines
Authors: Wessels Francois J. L. , Venter G. , Von Backström T. W.
Published: December 2013

In the well developed field of airfoil design there are a number of established schemes for describing airfoils, each with its own limitations and suitability to a particular application. Although less parsimonious, B-splines are often used to find solutions unconstrained by the characteristics of these schemes. They have proven useful to improve on existing designs and are useful in a numerical optimization process. As part of a numerical design project of a small wind turbine, a parametric scheme using Non-Uniform Rational B-Splines (NURBS) offering intuitive control over airfoil shape and unambiguous definitions for chord length and angle of attack is needed. These features are achieved at the lowest number of variables possible to ensure numerical optimization efficiency. Two previously uninvestigated NURBS arrangements are defined and investigated. The quality of the resulting airfoil reproductions are geometrically and aero-dynamically investigated and based on the results, the use of a thickness-camber scheme is motivated.
Uncertainty of Forced Response Numerical Predictions of an Industrial Blisk: Comparison With Experiments
Authors: Mayorca María A. , Vogt Damian M. , Mårtensson Hans , Andersson Clas , Fransson Torsten H.
Published: December 2013

Numerical methods, both Computational Fluid Dynamics (CFD) as well as Finite Elements (FE) methods, are widely used in industry with the purpose of predicting potential fatigue problems early in the design process. However, the uncertainty of such predictions is not clearly identified. The present paper presents the prediction of the vibration response of a rotor blisk part of 1 1/2 transonic compressor stage with comparison with experiments. Different uncertainty sources along the numerical aeromechanical chain are then identified. CFD solvers are employed for the prediction of both blade row interaction forces as well as the aerodynamic damping determination. Mistuning is assessed by the use of Reduced Order Modeling analyses and results compared with tip timing data. The peak amplitude response of a resonance mode of interest is determined for two different inlet conditions and thus the accuracy dependence on the excitation level is discussed. Results show that the largest uncertainties come from the unsteady aerodynamics, in which both aerodynamic damping and forcing estimations are critical. The structural dynamic models seem to capture the vibration response and mistuning effects well. Additionally, the challenges of tip timing data processing for detailed one-to-one validation of the tools are highlighted.
Power Loss in High-Speed Micro Turbomachinery: An Experimental Study
Authors: Walton James F. , Heshmat Hooshang , Tomaszewski Michael
Published: December 2013

In the paper the authors present the results of a study to investigate the windage and foil bearing losses in modern high-speed micro-turbomachinery such as motors, turboexpanders and turbogenerator rotor systems. Areas investigated include clearance between rotor and static structure; surface roughness; and ambient pressure conditions. Comparisons between experiments and theoretical windage loss models show excellent correlation at high speeds. Testing also indicated that some optimum rotor stator gaps are possible to minimize windage loss and that surface roughness can significantly impact windage. It was also shown that for rotor systems with foil bearings, at lower speeds rapid deceleration occurs. This is most likely due to the reduction in film thickness and onset of asperity contact between rotor and bearing surfaces. As expected ambient pressure also impacts windage losses.

The theoretical rotor windage loss models, their range of applicability and key limitations of those loss models are discussed. While bearing losses are not included in theoretical windage loss models, it was shown that they do need to be considered, especially when developing very high speed motor/generators. Approaches to properly account for the wide array of losses in order to develop high power density power sources are recommended.
Experimental and Numerical Investigation Into the Aerodynamics of a Novel Steam Turbine Valve and its Field Application
Authors: Zanazzi Giorgio , Baumgartner Felix , Rice Timothy , Pengue Fabio , Mokulys Thomas , Ridoutt Colin , Sell Michael
Published: December 2013

Control valves are one of the key steam turbine components that guarantee operational safety in a power plant.

There are two aerodynamic aspects, which are the current focus for the development of Alstom’s valves. One is the reduction of the aerodynamic loss to increase the efficiency of the power plant. The other is operational flexibility, which is increasingly demanded to react faster to load requirements from the electric grid. This is becoming more important as power generation becomes increasingly decentralized, with a growing contribution from renewable energy sources. For this reason, a fast control loop is required for valve operation, which depends on an accurate linearization of the valve characteristic.

In this paper the flow fields in an existing steam control valve have been analysed and subsequently optimized using CFD techniques. The approach specifically designed for drilled strainers is further illustrated. Following the validation of the baseline design with model testing, an improved diffuser has been designed using CFD analysis and the resulting performance benefit has been confirmed with further testing.

The required grid frequency support requires control valve throttling. For this reason, an accurate prediction of the linearization table is extremely important to support the required response time limits. Further numerical work has been carried out with various opening positions of the valve, leading to an improved valve linearization characteristic. It is demonstrated that the numerical prediction of the linearization curve agrees very well with data obtained from operating power plants.
Cast-in-Pair Blade Release Simulation and Comparison to Experiments With a Full Scale Rig
Authors: Cristóbal Erlantz , Moñux Sergio , Cerezo Carlos , Cendón David , Galvez Francisco , Erice Borja
Published: December 2013

This paper deals with the simulation of a Low Pressure Turbine (LPT) blade release and the subsequent impact onto the casing. The blade design is a cast-in-pair novel configuration where two airfoils are attached to a single firtree. This design solution was implemented in the first stage of the Low Pressure Turbine of the TP400-D6 engine using a directionally solidified M247 alloy. Due to the novelty of the design configuration a case containment test was carried out for certification versus CS-E810 EASA airworthiness requirement. The test was full scale reproducing engine-operating temperature and red line rotational speed.

The objective of the present work is the simulation of the blade release failure event including the interaction with the trailing blades and the severe impact onto the casing. The simulation is compared and validated against the results of the full-scale rig.

Material behaviour under impact working condition is characterised through Hopkinson bar tests, ballistic tests and triaxial traction tests. Johnson-Cook constitutive and failure material models are generated for the blade casting, the case forge material and the shroud seal segment. This material model is a temperature and strain-rate dependant flow stress model.

Containment simulation is carried out with LS-DYNA implicit/explicit solver. Simulation work includes meshing and boundary conditions effects on model fidelity. Case damage progression is linked to each of the different airfoil portions as contact occurs. The friction contribution to the case and blades interface and to the case final form is also revised.

In addition, the importance of the trailing blades and the interaction with the released blade is assessed. Interaction effect comprises both the resulting damage between airfoils and the change in primary release trajectory.

Finally, simulation results are compared to the full scale rig results. Case-impacted final geometry and internal energy from simulation are checked against test evidences.
Study on Micro-Turbine Engine’s Characteristics During Windmill Starting Process
Authors: Fu Xin , Wan Zhaoyun , Huang Guoping , Xie Zheng
Published: December 2013

This paper examines the performance characteristics of a certain model of micro-turbine jet engine during windmill starting process, on the basis of numerical simulation and experimentation. First, the rotor’s comprehensive mechanical loss at various rotation rates below idling speed can be generated through the combination of the cold blowing experiments on turbine-less rotor system and the numerical simulation upon compressor under related in-flow Mach numbers. Given the rotor’s comprehensive mechanical loss, cold blowing experiments on the whole micro-turbine jet engine bring out the whole engine’s balance characteristics at various Mach numbers below idling speed, via the numerical simulation upon compressor and turbine. Moreover, based on numerical simulation and experimentation, the influence of propane ignition time and propane pressure upon engine rotation speed and combustion chamber temperature is studied to meet the demand of combustion in the shortest possible time, as well as confirm the minimum required propane. Further experiments show the optimal jet fuel supply time and pattern that bring the micro-turbine jet engine to idling status within the minimum time, and also reveal the minimum windmill starting time at various in-flow Mach numbers, as well as the minimum Mach number for windmill start.
Experimental and Numerical Investigations on a Rotating Centrifugal Compressor
Authors: Almeida Patricio , Gibert Claude , Leblanc Xavier , Ousty Jean-Philippe , Thouverez Fabrice
Published: December 2013

Controlling the dynamic behavior of turbomachines requires an experimental validation phase to ensure their safety. The application of two experimental techniques to measure the modal properties of a rotating centrifugal compressor impeller is described in this paper. The impeller was tested in a vacuum chamber with excitation provided by piezoelectric actuators mounted on the rear side of the impeller disk.

The most common technique used to measure the dynamic behavior of a rotating structure is based on strain gauges and a telemetry system or a slip ring for signal transmission. Nevertheless, in some cases this method is an intrusive technique that could introduce damping and blade mistiming, and it can also be time consuming to prepare. Strain gauge measurement has been compared to measurements performed under the same conditions by Scanning Laser Doppler Vibrometer associated with a derotator optical system, which allows measurement at fixed points on a rotating part.

This work focuses on the study of the dynamic behavior of a centrifugal compressor impeller in view to preparing stator contact interaction tests requiring precise characterization of frequencies and nodal diameters and of the influence of rotation speed and other possible parameters.

The advantages and disadvantages of the two methods used have been assessed for this particular application. A correlation between the experiments and the numerical simulations using the finite element method is provided.
The Texas Cryogenic Oxy-Fuel Cycle (TCO): A Novel Approach to Power Generation With CO2 Options
Authors: Gatewood Jason , Moore Jeff , Nored Marybeth , Brun Klaus , Iyengar Vishwas
Published: December 2013

A novel oxy-fuel based power cycle is presented that combines conventional oxy-fuel cycle technology with novel mixed gaseous compression and liquid pumping of CO2 to produce both useable power and provide transportable CO2 for transportation via pipeline for use in sequestration or enhanced oil recovery (EOR). CO2 emissions reduction is a central focus of climate change initiatives. Therefore, it is desired to have a power plant process cycle that reduces CO2 emissions associated with producing power. Once captured CO2 must be transferred to a sequestration site for long term storage or utilized in EOR operations. Recent research has demonstrated that CO2 is most efficiently transported as a liquid at high pressures via pipelines. A Cryogenic Oxy-Fuel cycle will be presented that captures all CO2 produced during combustion and inherently converts that CO2 to a sequestration-ready state that can be immediately placed into transportation pipelines and stored at the desired sequestration site. The proposed cycle deviates from conventional cycles in that during part of the process the CO2 is in cooled liquid form which allows; 1) Decreased power demand to increase the CO2 pressure because pumping has lower power requirement than compression, 2) The take-off of the CO2 is optimized for pipeline transport and no further compression or expansion is required, and 3) A high overall thermodynamic cycle efficiency can be reached with relatively low firing temperatures in the oxy-burner (around 1000°F). This significantly simplifies the combustor and expander designs required for the process. Additional benefits of the cycle include predicted efficiencies near state of the art IGCC’s, applicability to multiple fuel sources, and cost reduction associated with reduced component sizes utilized in the cycle. This presentation will focus on the overall operational and technological requirements of the novel cycle, a breakdown of the individual components utilized, and simulations demonstrating predicted performance. Technological challenges of implementing a working version of the cycle will be discussed and suggested development required for overcoming the challenges will be presented. This paper will include recent research and development of an oxy-fuel combustor utilized in the cycle as well as implementation of compression and pumping apparatus of recent development.
Influence of Mission Variability on Fracture Risk of Gas Turbine Engine Components
Authors: Enright Michael P. , Moody Jonathan P. , Chandra Ramesh , Pentz Alan C.
Published: December 2013

The need for application of probabilistic methods to fatigue life prediction of gas turbine engine components is being increasingly recognized by the U.S. Military. A physics-based probabilistic approach to risk assessment provides improved accuracy compared to a statistical assessment of failure data because it can be used to (1) predict future risk and (2) assess the influences of both deterministic and random variables that are not included in the failure data. Probabilistic risk and fatigue life prediction of gas turbine engine fracture critical components requires estimates of the applied stress and temperature values throughout the life of the component. These values are highly dependent upon the mission type and may vary from flight to flight within the same mission. Currently, standard missions are specified and used during the engine design process, but the associated stresses can differ significantly from stress values that are based on flight data recorder (FDR) information. For this reason, efforts are made to periodically update the standard missions and to assess the impact on component structural integrity and associated risk of fracture. In this paper, the influence of mission type and variability on fracture risk is illustrated for an actual gas turbine engine disk subjected to a number of different mission loadings. Disk stresses associated with each mission were obtained by scaling finite element model results based on RPM values obtained from engine flight recorder data. The variability in stress values throughout the life of the component was modeled using two different approaches to identify the upper and lower bound value influences on the risk of fracture. The remaining variables were based on default values provided in FAA Advisory Circular (AC) 33.14-1 “Damage Tolerance for High Energy Turbine Engine Rotors”. The risk of fracture was computed using a probabilistic damage tolerance computer code called DARWIN® (Design Assessment of Reliability With Inspection) and compared for each mission type to illustrate the maximum influence of mission type on fracture risk. The results can be used to gain insight regarding the influence of mission type and associated variability on the risk of fracture of realistic engine components.
Design Modification of a Heavy Duty Industrial Gas Turbine Blade for Life Improvement
Authors: Hutchison Chris , Chan Anthony , Stankiewicz Dan
Published: December 2013

Cracking at the trailing edge of a heavy duty industrial gas turbine blade has been observed on a number of serviced parts. The cracking usually occurs within 1.0″ of the platform. The trailing edge (TE) cracks have been found to propagate through the airfoil, leading to airfoil separation and severe engine damage. Liburdi Turbine Services has undertaken an independent metallurgical and stress analysis of the blade to determine the cause of the cracking. This paper covers the stress and low cycle fatigue (LCF) analysis of a platform undercut modification designed to mitigate crack initiation and thus increase part life. A finite element model of the blade was developed. Thermal loading was applied from a conjugate heat and mass transfer analysis between the blade, gas path flow and internal cooling flow. Base load conditions were used at turbine inlet temperature 2482°F. Results showed that the peak stress was present in the TE cooling slot corner, and was large enough to cause local yielding and LCF. The geometry of the modification was shown to strongly influence stress in the TE airfoil region and in the undercut region. Thus a balance was found to provide sufficiently low stresses in both regions and still be practical for machining. The modification was found to decrease stress in the TE cooling slot by a factor of 0.71 relative to that of the current OEM design, and increase life by 1.79 times. A viable modification has been demonstrated to extend blade life by reducing local stress and thus mitigating crack initiation at the airfoil TE.
Improving the Reliability of TF50, TF40, ETF40B FADEC
Authors: Crowe David , Crom Elden
Published: December 2013

The successful Naval use of the TF50 and TF40 variants as high horsepower power plants has demonstrated a high degree of utility. Engineering analysis has shown that aspects of their design could be improved to increase reliability and increase platform availability while reducing the cost of ownership. As each year passes, electronic systems that can be housed in the current form factor improve in both reliability and capability. With that in mind, TES have developed a field replaceable, foot print and pin compatible upgrade to the existing FADEC (Full Authority Digital Electronic Control). The upgraded unit has all of the capabilities of the old unit with many enhancements. The enhancements include: full rate diagnostics with user controlled viewers, modular design, removal of maintenance prone components, improved statistical analysis, and the ability to extend data collection. The result of these enhancements will not only improve FADEC reliability but will also allow improved engine prognostics and health monitoring.
Fatigue Strength and Metal Condition in the Context of Gas Turbine Buckets Life Extension
Authors: Ivanov Sergey A. , Rybnikov Alexander I.
Published: December 2013

Criteria for remaining life estimation and methods for enhancing fatigue resistance of heavy-duty gas turbine bucket metal are based on the analysis of changes in the structure and properties of metal after long-term operation. High-cycle fatigue (HCF) resistance is shown to be a decisive characteristic in the residual life estimation of turbine buckets after operation over 100,000 hours. The tests of the buckets from cast and wrought nickel-based alloys after long-term operation demonstrated decreasing of fatigue strength by up to 25%. The metal structure in operation undergoes notable deterioration mainly in phase redistribution. The size and configuration of metal phases are changing also. It caused the changes in metal properties. The decrease of the bucket fatigue strength correlates with the decrease of metal ductility.

The reconditioning heat treatment resulted in restoring mechanical properties of metal. The fatigue resistance also increased nearly to the initial level.

The influence of operational factors on bucket fatigue strength deterioration has been established. The mechanical damages on bucket airfoil may decrease the fatigue resistance. We found the correlation of endurance limit and damages depth.

The procedures for metal properties recovering and buckets service life substantial extension have been developed. It has resulted in the extension of the buckets service life by up to 50% over the assigned life in gas turbines operated by Gazprom.
Vaginally Delivered Tenofovir Disoproxil Fumarate Provides Greater Protection than Tenofovir against Genital Herpes in a Murine Model of Efficacy and Safety
Authors: Nixon Briana , Jandl Thomas , Teller Ryan S. , Taneva Ekaterina , Wang Yanhua , Nagaraja Umadevi , Kiser Patrick F. , Herold Betsy C.
Published: December 2013

Increased susceptibility to genital herpes in medroxyprogesterone-treated mice may provide a surrogate of increased HIV risk and a preclinical biomarker of topical preexposure prophylaxis safety. We evaluated tenofovir disoproxil fumarate (TDF) in this murine model because an intravaginal ring eluting this drug is being advanced into clinical trials. To avoid the complications of surgically inserting a ring, hydroxyethylcellulose (HEC)-stable formulations of TDF were prepared. One week of twice-daily 0.3% TDF gel was well tolerated and did not result in any increase in HSV-2 susceptibility but protected mice from herpes simplex virus 2 (HSV-2) disease compared to mice treated with the HEC placebo gel. No significant increase in inflammatory cytokines or chemokines in vaginal washes or change in cytokine, chemokine, or mitochondrial gene expression in RNA extracted from genital tract tissue was detected. To further evaluate efficacy, mice were treated with gel once daily beginning 12 h prior to high-dose HSV-2 challenge or 2 h before and after viral challenge (BAT24 dosing). The 0.3% TDF gel provided significant protection compared to the HEC gel following either daily (in 9/10 versus 1/10 mice,
P
< 0.01) or BAT24 (in 14/20 versus 4/20 mice,
P
< 0.01) dosing. In contrast, 1% tenofovir (TFV) gel protected only 4/10 mice treated with either regimen. Significant protection was also observed with daily 0.03% TDF compared to HEC. Protection was associated with greater murine cellular permeability of radiolabeled TDF than of TFV. Together, these findings suggest that TDF is safe, may provide substantially greater protection against HSV than TFV, and support the further clinical development of a TDF ring.
Reversible Cysteine Protease Inhibitors Show Promise for a Chagas Disease Cure
Authors: Ndao Momar , Beaulieu Christian , Black W. Cameron , Isabel Elise , Vasquez-Camargo Fabio , Nath-Chowdhury Milli , Massé Frédéric , Mellon Christophe , Methot Nathalie , Nicoll-Griffith Deborah A.
Published: December 2013

The cysteine protease cruzipain is essential for the viability, infectivity, and virulence of
Trypanosoma cruzi
, the causative agent of Chagas disease. Thus, inhibitors of cruzipain are considered promising anti-
T. cruzi
chemotherapeutic agents. Reversible cruzipain inhibitors containing a nitrile “warhead” were prepared and demonstrated 50% inhibitory concentrations (IC
50
s) as potent as 1 nM in baculovirus-generated cruzipain enzyme assays. In epimastigote and intracellular amastigote
in vitro
assays, the most potent compounds demonstrated antiparasitic behavior in the 5 to 10 μM IC
50
range; however, trypomastigote production from the amastigote form was ∼90 to 95% inhibited at 2 μM. Two key compounds, Cz007 and Cz008, with IC
50
s of 1.1 and 1.8 nM, respectively, against the recombinant enzyme were tested in a murine model of acute
T. cruzi
infection, with oral dosing in chow for 28 days at doses from 3 to 50 mg/kg of body weight. At 3 mg/kg of Cz007 and 3 mg/kg of Cz008, the blood parasitemia areas under the concentration-time curves were 16% and 25% of the untreated group, respectively. At sacrifice, 24 days after immunosuppression with cyclophosphamide, parasite presence in blood, heart, and esophagus was evaluated. Based on negative quantitative PCR results in all three tissues, cure rates in surviving animals were 90% for Cz007 at 3 mg/kg, 78% for Cz008 at 3 mg/kg, and 71% for benznidazole, the control compound, at 50 mg/kg.
Vaccinated C57BL/6 Mice Develop Protective and Memory T Cell Responses to Coccidioides posadasii Infection in the Absence of Interleukin-10
Authors: Hung Chiung-Yu , Castro-Lopez Natalia , Cole Garry T.
Published: December 2013

High concentrations of lung tissue-associated interleukin-10 (IL-10), an anti-inflammatory and immunosuppressive cytokine, correlate with susceptibility of mice toCoccidioidesspp. infection. In this study, we found that macrophages, dendritic cells, neutrophils, and both CD8+and CD4+T cells recruited toCoccidioides posadasii-infected lungs of nonvaccinated and vaccinated mice contributed to the production of IL-10. The major IL-10-producing leukocytes were CD8+T cells, neutrophils, and macrophages in lungs of nonvaccinated mice, while both Foxp3+and Foxp3−subsets of IL-10+CD4+T cells were significantly elevated in vaccinated mice. Profiles of the recruited leukocytes in lungs revealed that only CD4+T cells were significantly increased inIL-10−/−knockout mice compared to their wild-type counterparts. Furthermore,ex vivorecall assays showed that CD4+T cells isolated from vaccinatedIL-10−/−mice compared to vaccinated wild-type mice produced significantly higher amounts of IL-2, gamma interferon (IFN-γ), IL-4, IL-6, and IL-17A in the presence of a coccidioidal antigen, indicating that IL-10 suppresses Th1, Th2, and Th17 immunity toCoccidioidesinfection. Analysis of absolute numbers of CD44+CD62L−CD4+T effector memory T cells (TEM) and IFN-γ- and IL-17A-producing CD4+T cells in the lungs ofCoccidioides-infected mice correlated with better fungal clearance in nonvaccinatedIL-10−/−mice than in nonvaccinated wild-type mice. Our results suggest that IL-10 suppresses CD4+T-cell immunity in nonvaccinated mice duringCoccidioidesinfection but does not impede the development of a memory response nor exacerbate immunopathology of vaccinated mice over at least a 4-month period after the last immunization.
Cover Your Cough! A Short and Simple Activity to Demonstrate the Antimicrobial Effect of Desiccation
Authors: Easterwood Jennifer Cook
Published: December 2013

Many undergraduate microbiology laboratory manuals include exercises demonstrating the antimicrobial effects of physical agents, such as UV light and heat, and chemical agents, such as disinfectants and antibiotics (3, 4). There is, however, a lack of exercises examining the effects of desiccation on bacterial growth and survival. This particular form of antimicrobial control is especially relevant today with an increased emphasis on coughing and sneezing into one’s sleeve or a tissue, where microbes will not contaminate hands and will eventually desiccate and die (2). Desiccation can have bacteriostatic or bactericidal effects depending on the species, the material on which the organism has desiccated, and the length of time. The absence of water can damage many cellular components, including enzymes, nucleic acids, and cell membranes (1). However, many prokaryotes have some degree of resistance to desiccation, with Escherichia coli surviving around 24 hours and Bacillus species surviving upwards of 300 years, though these numbers can vary due to a number of confounding factors (5). Some of these factors include the method by which desiccation occurred, whether desiccation occurred in a natural or laboratory situation, and the species itself (5). To address the effects of desiccation on bacterial growth and survival, a short, simple exercise was developed. By inoculating various materials with bacterial cultures and allowing them to air-dry for 24 hours, students can visualize the effects of desiccation by analyzing the growth, or lack thereof, when organisms are transferred to nutrient agar plates. This exercise has been used in a health professions microbiology course as well as a microbiology course for biology and biochemistry majors. It is short enough to be conducted during a standard lecture period or during a longer laboratory period in conjunction with other experiments demonstrating the effectiveness of physical agents on microbial growth
Connecting Music, Art, and Science for Increased Creativity and Topic Engagement
Authors: McNealy Tamara L.
Published: December 2013

‘Attention spans have shortened,’ is a common phrase often used in reference to today’s college students. As faculty and instructors, we need to address this issue through the utilization of innovative and creative techniques that aid in making our subjects accessible to our students. Connecting a serious topic such as microbiology with a ‘fun’ activity can increase student engagement and learning. Ideas to maintain student attention on a subject include providing information in 15- to 20-minute blocks, giving one- to two-minute assignments, and providing an active learning activity at least once per hour. But what if we could also increase their engagement with science by connecting it to things they already think of outside of class, and, in addition, make science thinking interdisciplinary? I have recently introduced exercises that connect music and art to various microbiology topics in my class. The creative processes in art and science have much in common. Albert Einstein recognized that both science and art delve into the mysterious by stating, “The most beautiful thing we can experience is the mysterious. It is the source of all true art and all science” (1). Connecting these subjects in the minds of our students will help them realize the importance of technology, industry, and progress in science and simultaneously emphasize the importance of art, music, and the humanities. The tools presented here will encourage students to connect new science information through the music and art they already know and, therefore, provide increased engagement and retention of the new knowledge. These techniques used in a microbiology class increased the amount of time spent thinking about new information, increased engagement with the information being presented, and encouraged critical thinking of microbiology topics. These tools were used in an upper level microbiology course, but the techniques can be easily incorporated into any course. The first tool uses music to (1) provide aural clues connected to specific pathogens; (2) encourage the student to interpret the song and identify ideas of the song with characteristics of the pathogen; and (3) allow the student to explore their own musical interests and connect that back to the topic pathogen. The second tool uses art to allow the student to (1) realize the intersection of art with science and (2) encourage critical thinking skills to conceptualize microbiology concepts from a unique perspective.
More Clinical Concepts and Less Content: A Different Approach to PathophysiologyReview of:	Pathophysiology: A Clinical Approach;	BraunCarie A.AndersonCindy M.; (	2011).	Wolters Kluwer Health, Lippincott Williams & Wilkins,	Philadelphia, PA.	526 pages.
Authors: Mauro Laura J.
Published: December 2013

Review of:
Pathophysiology: A Clinical Approach;
Carie A. Braun and Cindy M. Anderson; (2011). Wolters Kluwer Health, Lippincott Williams & Wilkins, Philadelphia, PA. 526 pages.
Acupuncture in De Quervain—s Disease: A Treatment Proposal
Authors: da Silva João Bosco Guerreiro , Batigália Fernando
Published: December 2013

De Quervain's disease is a painful stenosing tenosynovitis of the first dorsal compartment of the hand affecting the tendons of the abductor pollicis longus and extensor pollicis brevis, caused mainly by overuse. Conventional treatments include rest, immobilisation, oral anti-inflammatory drugs, corticosteroid injection and even surgery, but none of these is established as clearly effective. Acupuncture is rarely mentioned and the points suggested are rather general—regional, tender and ah shi points. Tendinopathy is almost always associated with problems in the relevant muscles and this paper calls attention to the correct identification and needling of the affected muscles, in order to increase the specificity of acupuncture treatment.
Should suspected cervical spinal cord injuries be immobilised? A systematic review protocol
Authors: Oteir Ala'a O , Jennings Paul A , Smith Karen , Stoelwinder Johannes
Published: December 2013

Background

Cervical spinal cord injuries may result in life-threatening situations and long-term disability. Prehospital spinal immobilisation is the standard of care for patients with potential spinal cord injury (SCI). It aims to prepare patients for transport, achieve neutral spinal alignment, and reduce movement and secondary injuries in potentially unstable spines. However, there is a lack of evidence on its clinical benefits and its overall effect on patient outcomes.

Objectives

To identify the reported outcomes following immobilisation of suspected cervical SCI, to compare the effects of spinal immobilisation versus no immobilisation on the reported outcomes, and to provide recommendations for prehospital cervical immobilisation.

Design/methods

A search of the literature will be conducted using relevant online databases. This will include all types of human studies that were published in English from the earliest record available to the first week of October 2013. One author will conduct the search and two independent authors will screen the titles and the abstracts identified by the search and critically appraise the selected papers. A third author will be available to resolve any disagreement. The findings will be reported according to Preferred Reporting Items for Systematic Reviews (PRISMA) guidelines. Critical appraisal as well as the level and the strength of evidence will follow the National Health and Medical Research Council (NHMRC) guidelines.

Discussion

Evidence-based practices should be pursued to further improve the prehospital care for suspected cervical SCI. This systematic review will contribute to the body of knowledge regarding the spinal immobilisation effects on the SCI patient's outcomes.
COSMOLOGICAL DYNAMICS OF MODIFIED GRAVITY WITH A NONMINIMAL CURVATURE-MATTER COUPLING
Authors: AZIZI TAHEREH , YARAIE EMAD
Published: December 2013

We perform a phase space analysis of a nonminimally coupled modified gravity theory with the Lagrangian density of the form [Formula: see text], where f1(R) and f2(R) are arbitrary functions of the curvature scalar R and [Formula: see text] is the matter Lagrangian density. We apply the dynamical system approach to this scenario in two particular models. In the first model we assume f1(R) = 2R with a general form for f2(R) and set favorable values for effective equation of state parameter which is related to the several epochs of the cosmic evolution and study the critical points and their stability in each cosmic eras. In the second case, we allow the f1(R) to be an arbitrary function of R and set f2(R) = 2R. We find the late-time attractor solution for the model and show that this model has a late-time accelerating epoch and an acceptable matter era.
Validating XML documents in the streaming model with external memory
Authors: Konrad Christian , Magniez Frédéric
Published: December 2013

We study the problem of validating XML documents of size
N
against general DTDs in the context of streaming algorithms. The starting point of this work is a well-known space lower bound. There are XML documents and DTDs for which
p
-pass streaming algorithms require Ω(
N
/
p
) space. We show that when allowing access to external memory, there is a deterministic streaming algorithm that solves this problem with memory space O(log
2
N
), a constant number of auxiliary read/write streams, and O(log
N
) total number of passes on the XML document and auxiliary streams. An important intermediate step of this algorithm is the computation of the First-Child-Next-Sibling (FCNS) encoding of the initial XML document in a streaming fashion. We study this problem independently, and we also provide memory-efficient streaming algorithms for decoding an XML document given in its FCNS encoding. Furthermore, validating XML documents encoding binary trees against any DTD in the usual streaming model without external memory can be done with sublinear memory. There is a one-pass algorithm using O(√
N
log
N
) space, and a bidirectional two-pass algorithm using O(log
2
N
) space which perform this task.
Gauss-seidel correction algorithm
Authors: Ko Ren-Song , Lin Po-Liang , Chiang Pei-Yu
Published: December 2013

A Gauss-Seidel correction (GSC) routing algorithm for wireless sensor networks is presented in which packets are transmitted with additional information which can be exchanged among nodes to correct the current routing paths and achieve load balancing. The problem considered here is single-class routing to one/multiple sinks with lifetime maximization as the objective. The formulation to correct the routing paths is not heuristic and takes its theoretical basis from a macroscopic model, that is, based on a set of partial differential equations iteratively solved by the Gauss-Seidel method. We then theoretically investigate the convergence of GSC. Furthermore, an initial value estimation algorithm is presented to alleviate the long-path problem during the delivery of the first several packets, thus accelerating the convergence of GSC. Simulation results show that GSC effectively achieves load balancing, particularly for regions of interest with holes.
An adaptive sensor sleeping solution based on sleeping multipath routing and duty-cycled MAC protocols
Authors: Yang Ou , Heinzelman Wendi
Published: December 2013

Various applications of wireless sensor networks require multihop data transmission over error-prone wireless links, hence multipath routing can be used to meet the application's reliability requirement. On the other hand, wireless sensors are usually battery powered, and thus it is very important to save energy in order to prolong the network lifetime. In this article, we propose (1) Sleeping Multipath Routing, which can trade off reliability and network lifetime by dynamically activating an optimal number of paths to support the application's reliability requirement and putting the rest of the sensors to sleep, and (2) an adaptive sensor sleeping solution, which includes Sleeping Multipath Routing, a duty-cycled MAC protocol, and cross-layer coordination to further prolong the network lifetime by putting sensors to sleep at both the routing and the MAC layers. Our proposed Sleeping Multipath Routing and adaptive sensor sleeping solution can be implemented on any multipath routing protocol that discovers multiple disjoint paths between two nodes, and any duty-cycled MAC protocol that has fixed cycle length. We show an example of implementing our adaptive sensor sleeping solution using Directed Diffusion and S-MAC. Simulation results show that our proposed adaptive sensor sleeping solution outperforms single-layer sensor sleeping with a longer network lifetime with required reliability support. Moreover, our proposed adaptive sensor sleeping solution can significantly prolong the network lifetime when the application's reliability requirement varies over time, or when the number of alive nodes in the network changes over time.