bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of the Degree of Reaction on the Leakage Loss in Steam Turbines
Authors: Yoon Sungho
Published: December 2013

The degree of reaction selected in designing steam turbines is of paramount importance. There has been competition between 50% reaction and impulse turbines over a century. It is therefore important to understand the effect of the degree of reaction on aerodynamic performance. In particular, a change in the degree of reaction affects the leakage flow substantially in both the stationary and rotating blades due to a change in the blade loading. The effect of the degree of reaction on the efficiency loss, due to leakage flows, is systematically investigated in this paper using analytical models.

It is shown that the appropriate way to understand the efficiency loss, due to leakage flows, is to estimate the kinetic energy dissipation rather than the leakage mass flow rate, as demonstrated by Yoon et al. [1]. In order to estimate the efficiency loss due to leakage flows, the well-known Denton model [2] is extended by considering the velocity triangles in a repeating turbine stage. The extended model is compared with experimental data, at different degrees of reaction, and shows good agreement with measurements.

It is shown that a reduction in the degree of reaction, at a fixed flow coefficient and a fixed work coefficient, results in an increase in the efficiency loss across the stationary blade, but a decrease in that across the rotating blade. However, the efficiency loss, across the stationary blade hub, is estimated to be smaller than the efficiency loss across the rotating blade tip. A stationary blade can be better sealed than a rotating blade by applying multiple seals and using a leakage path with a low radius.

The efficiency loss, due to the tip leakage flow, is substantially influenced by the choice of the tip configuration. Shrouded blades show several aerodynamic advantages over unshrouded blades in reducing the tip leakage efficiency loss. Employing multiple seals over the shroud decreases the tip leakage mass flow rate significantly. Moreover, as the degree of reaction approaches zero, the tip leakage mass flow rate over the shroud becomes small, since the axial pressure drop across the rotating blade becomes small. In unshrouded blades, a reduction in the degree of reaction is shown to increase the leakage mass flow rate over the tip, because the circumferential pressure difference between the blade pressure side and blade suction side generally increases when the pitch-to-chord ratio remains unchanged.
Case Study: Metallurgical Analysis of Previously Repaired GE Frame 7FA Stage 1 Turbine Buckets
Authors: Nagy Douglas R. , Kuipers Justin H.
Published: December 2013

A case study is presented in which a destructive metallurgical analysis was performed on three GE Frame 7FA+e stage 1 buckets which had each been repaired using different approaches. The metallurgical condition and extent of the prior repairs are presented for each of the buckets following one additional service interval. The analyses included evaluation of the macroscopic condition, base alloy microstructure, stress rupture properties, internal and external surface coating conditions and the tip integrity.

The first bucket had not been dimensionally restored at the tip during repair (i.e. the tip was still comprised of the original casting). The bucket exhibited moderate oxidation and loss of tip material. Base alloy degradation was observed at the mid airfoil height in the form of coarsening, rounding and agglomeration of the primary gamma prime precipitates. Secondary gamma prime precipitates remained in some of these regions, indicative that the alloy microstructure had not been rejuvenated by full solution treatment during repair. The second bucket had been weld repaired at the tip using a solid solution strengthened weld filler alloy. Following service, the tip exhibited significant oxidation and approximately 6mm of material loss at the mid-chord and trailing edge tip. Within the tip repair material, micro-cracks and creep voids were observed. The base alloy condition appeared similar to the first bucket. The third bucket had been tip weld repaired using a precipitation hardened weld filler alloy and rejuvenated with a full solution treatment. Following service, the bucket exhibited negligible oxidation and material loss at the tip. Overall, microstructural base alloy degradation was found to be minor.
Simulation of 2-Way Fluid Structure Interaction in a 3D Model Combustor
Authors: Shahi Mina , Kok Jim B. W. , Alemela P. R.
Published: December 2013

The liner of a gas turbine combustor is a very flexible structure that is exposed to the pressure oscillations that occur in the combustor. These pressure oscillations can be of very high amplitude due to thermoacoustic instability, when the fluctuations of the rate of heat release and the acoustic pressure waves amplify each other. The liner structure is a dynamic mechanical system that vibrates at its eigenfrequencies and at the frequencies by which it is forced by the pressure oscillations to which it is exposed. On the other hand the liner vibrations force a displacement of the flue gas near the wall in the combustor. The displacement is very small but this acts like a distributed acoustic source which is proportional to the liner wall acceleration. Hence liner and combustor are a coupled elasto-acoustic system. When this is exposed to a limit cycle oscillation the liner may fail due to fatigue.

In this paper the method and the results will be presented of the partitioned simulation of the coupled acousto-elastic system composed of the liner and the flue gas domain in the combustor. The partitioned simulation uses separate solvers for the flow domain and the structural domain, that operate in a coupled way. In this work 2-way fluid structure interaction is studied for the case of a model combustor for the operating conditions 40–60 kW with equivalence ratio of 0.625. This is done in the framework of the LIMOUSINE project. Computational fluid dynamics analysis is performed to obtain the thermal loading of the combustor liner and finite element analysis renders the temperature, stress distribution and deformation in the liner. The software used is ANSYS workbench V13.0 software, in which the information (pressure and displacement) is also exchanged between fluid and structural domain transiently.
Validation of Linearized Navier-Stokes Based Flutter Prediction Tool: Part 2—Quantification of the Prediction Accuracy on a Turbine Test Case
Authors: Sanz Luengo Antonio , Vogt Damian M. , Schmitt Stefan , Fransson Torsten H.
Published: December 2013

This is the second part of two papers describing the validation of a tool chain for flutter prediction. The first paper provides an overview of the numerical methods and their verification. The second paper presents the detailed validation of the tool chain on the basis of experimental data obtained from measurements of an annular cascade sector comprising 3D twisted turbine blades.

Aeroelastic test data has been acquired in an isolated blade row consisting of seven free-standing low-pressure (LP) turbine blades. The middle blade has been oscillated in controlled manner in three orthogonal modes and at various frequencies while measuring the unsteady blade surface pressure on several blades. The data has been reduced to aerodynamic influence coefficients and finally recombined to travelling wave mode stability curves. By acquiring data at various spanwise positions, a basis for validating three-dimensional effects has been provided.

The validation of the investigated flutter prediction tool has been performed in a detailed manner and on various levels, started from a critical reduced frequency over stability curves to local work coefficients. At the lowest level of condensation, the unsteady blade surface pressures have been compared. Correlation to test data is shown and discussed rigorously at these various levels giving a detailed assessment of the prediction accuracy of the investigated tool.
Model of Performance of Stirling Engines
Authors: Muñoz de Escalona J. M. , Sánchez D. , Chacartegui R. , Sánchez T.
Published: December 2013

This work presents a detailed model of performance of Stirling engines which is expected to be of interest for the Concentrated Solar Power community. In effect, gas turbines of different types have been proposed for small and medium scale solar applications based on their reduced (even inexistent) water consumption and modularity. In the medium to large scale, conventional steam turbine based plants demand high investment costs as well as high operation costs (mostly due to water consumption). In the small-scale it is the Stirling engine which is generally consider as the prime mover of choice due to its high efficiency at moderate temperatures. In this context, this paper describes a detailed model of performance of Stirling engines. The model includes frictional and mechanical losses, heat transfer within the engine and other features like auxiliary power consumption and applies to both on-design and off-design operation. The validation of all these capabilities is also presented in the text. Hence, the model is expected to provide a valuable tool for individuals who need to assess the performance of externally heated piston engines.
Models for Small Crack Growth in LCF at Room Temperature and High Temperature
Authors: Beretta Stefano , Foletti Stefano , Rabbolini Silvio , Bordo Luca E. , Sanguineti Andrea , Traversone Laura
Published: December 2013

The life assessment for a component subjected to high strain concentration in critical regions can be treated as a crack growth estimation starting from the first cycle of the component life together with an appropriate crack growth model. This approach assumes that the presence of small defects or slip bands causes a quick crack nucleation in critical regions where Low Cycle Fatigue (LCF) design is adopted. Such a tool is useful to assess the residual life of a component in the presence of a crack in critical regions where high stress concentrations cause cyclic yielding of the material. The scope of this paper is to discuss the application of existing models to a quenched and tempered structural steel. In particular, a series of experimental tests in the LCF regime at room and at high temperature (up to T = 500°C) have been performed in order to analyze the crack propagation in the presence of plastic deformations. Two types of specimens have been used. Smooth cylindrical specimens have been used to obtain the cyclic stress-strain curve and the Manson-Coffin curve under constant strain amplitude loading. Moreover, in order to observe the initiation and growth of a fatigue crack, additional cylindrical specimens with an artificial defect of 100 or 400 μm depth have been tested. For these specimens, during the interruption of fatigue tests, the crack advancement has been detected using the plastic replica technique with a thin foil of acetate. The experimental results have been examined in terms of crack growth rates and a series of parameters have been used to correlate these data with the external applied load. Two different approaches, i.e. fracture mechanics approach (based on ΔK and ΔJ) and analytical model based on Manson-Coffin law, have been analyzed in order to define a model able to predict the crack growth rate for high constant strain amplitudes. Finally, a new analytical model able to predict the crack growth rates is presented.
Life Prediction for Turbopropulsion Systems Under Dwell Fatigue Conditions
Authors: Chan Kwai S. , Enright Michael P. , Moody Jonathan P. , Hocking Benjamin , Fitch Simeon H. K.
Published: December 2013

The objective of this investigation was to develop an innovative methodology for life and reliability prediction of hot-section components in advanced turbopropulsion systems. A set of three generic time-dependent crack growth models was implemented and integrated into the DARWIN® probabilistic life-prediction code. Using the enhanced risk analysis tool and material constants calibrated to IN 718 data, the effect of time-dependent crack growth on the risk of fracture in turboengine component was demonstrated for a generic rotor design and a realistic mission profile. The results of this investigation confirmed that time-dependent crack growth and cycle-dependent crack growth in IN 718 can be treated by a simple summation of the crack increments over a mission. For the temperatures considered, time-dependent crack growth in IN 718 can be considered as a K-controlled environmentally-induced degradation process. Software implementation of the generic time-dependent crack growth models in DARWIN provides a pathway for potential evaluation of the effects of multiple damage modes on the risk of component fracture at high service temperatures.
Examples of the Use of Optical Spectroscopy to Detect Damage of Thermal Barrier Coatings During Cyclic Oxidation
Authors: Rinaldi Claudia , del Corno Ada , Enrichi Francesco
Published: December 2013

This paper describes some examples of the use of two optical spectroscopy techniques to study thermal barrier coating (TBC) degradation preceeding failure. The first part describes photoluminescence piezospectroscopy (PLPS) results obtained on a series of specimens with EB-PVD TBC and Pt -aluminised bond coats. The monotonic decrease of the alumina compressive stress level with ageing and thermal cycling confirms that TGO compressive stress levels can be used as residual life indicators in this type of coating. The automatic mapping system implemented by RSE (Ricerca sul Sistema Energetico) provides precise and reliable results about the level of damage at the BC/TBC interface, well before failure; mapping provides data regarding the precise positions where the first macroscopic detachment (a few millimeters wide) occurs. As PLPS is not applicable to thermal-sprayed APS TBCs, the second part of the paper describes some examples of the contribution that Raman spectroscopy can provide to detect phase changes due to degradation preceeding failure of the TBCs. Possible problems relating to the presence of undesired RE elements in the ceramic layer due to strong fluorescence are also described; solutions are proposed. Finally, examples of how innovative confocal microRaman produces maps evidencing areas where high temperature exposure and thermal cycling-produced phase transformation of the Yttria partially stabilised Zirconia from tetragonal to monoclinic (which typically occurs during cracking processes preceeding final TBC failure) are provided.
Numerical Modeling of Fluid-Induced Rotordynamic Forces in Seals With Large Aspect Ratio
Authors: Untaroiu Alexandrina , Untaroiu Costin D. , Wood Houston G. , Allaire Paul E.
Published: December 2013

Traditional annular seal models are based on bulk flow theory. While these methods are computationally efficient and can predict dynamic properties fairly well for short seals, they lack accuracy in cases of seals with complex geometry or with large aspect ratios (above 1.0). In this paper, the linearized rotordynamic coefficients for a seal with large aspect ratio are calculated by means of a three dimensional CFD analysis performed to predict the fluid-induced forces acting on the rotor. For comparison, the dynamic coefficients were also calculated using two other codes: one developed on the bulk flow method and one based on finite difference method. These two sets of dynamic coefficients were compared with those obtained from CFD. Results show a reasonable correlation for the direct stiffness estimates, with largest value predicted by CFD. In terms of cross-coupled stiffness, which is known to be directly related to cross-coupled forces that contribute to rotor instability, the CFD predicts also the highest value; however a much larger discrepancy can be observed for this term (73% higher than value predicted by finite difference method and 79% higher than bulk flow code prediction). Similar large differences in predictions one can see in the estimates for damping and direct mass coefficients, where highest values are predicted by the bulk flow method. These large variations in damping and mass coefficients, and most importantly the large difference in the cross-coupled stiffness predictions, may be attributed to the large difference in seal geometry (i.e. the large aspect ratio AR>1.0 of this seal model vs. the short seal configuration the bulk flow code is usually calibrated for, using an empirical friction factor).
Dynamic Characterization of Tilting Pad Journal Bearings From Component and System Level Testing
Authors: Delgado Adolfo , Librashi Mirko , Vannini Giuseppe
Published: December 2013

The dynamic response of a direct lube, 5-pad, rocker-back pivot tilting pad bearing is characterized in a controlled motion (component level) test rig, and in a spin bunker (full system level) using a dummy rotor mounted on two identical bearings. In the component level test, the force coefficients (stiffness, damping, mass) are identified from pseudorandom excitations using a 2-DOF model. N-DOF system including the pad motions has been shown to yield frequency dependent coefficients that warrant the use of asynchronous coefficients for stability analysis in centrifugal compressors. However, experimental results showed that the real part of the dynamic stiffness is well represented as a constant stiffness and mass coefficients while the imaginary part yields a constant damping coefficient (i.e. frequency independent).

In the system level test, a dedicated dummy rotor (representative of a high speed centrifugal compressor rotor) is excited by a magnetic shaker throughout a frequency range covering the rotor modes of interest while spinning at constant speed. From the rotor harmonic response the damping of each mode is extracted using a curve-fitting method based on a 1-DOF model for a given set of speeds.

The dummy rotor test provides reference values for system logarithmic decrement and further validates the component level test results. The logarithmic decrement prediction using identified bearing force coefficients are in good agreement with the experimental results. In addition, using for prediction identified coefficients in a classical K-C-M or synchronous K-C form yields similar results (within 15%). This indicates that for the given bearing geometry (clearance, offset and size) and operating conditions, synchronously reduced force coefficients are adequate for stability analysis. Comparison of the identified force coefficients with results from commercially available code yielded reasonable agreement on direct coefficients while some discrepancies are highlighted on the cross-coupled coefficients.
The Rolls-Royce MT30 Compact Package Design
Authors: Whatmough Damian , Birtwistle Tim
Published: December 2013

The new Rolls-Royce MT30 package offers a powerful and lightweight package that is suitable for installation in both commercial and naval vessels. The MT30 can deliver 40MW into either a mechanical water jet or propeller driven application and to a generator in an electrically driven Ship. It can be installed in many sizes of ships capable of operating worldwide.

This paper will discuss the compact MT30 package in the context of all ship applications currently in-use and for future use across the full range of power and propulsion systems. It will highlight the design drivers for the product including power output, operational environment, certification and MT30 and package maintenance.
Stiffening Effect of Motor Core Webs for Torsional Rotordynamics
Authors: Kulhanek Chris D. , James Stephen M. , Hollingsworth Justin R.
Published: December 2013

Longitudinal webs or spider bars are often placed mid-span of a motor shaft and are primarily used to support the windings or rotor laminations while allowing sufficient space for cooling air flow. When subject to a torque, the radial webs experience a loading configuration that includes bending and torsion while the base shaft experiences pure torsion. A webbed cross-section has a higher torsional stiffness as compared to the torsional stiffness of just the circular portion of the shaft section. This influences the torsional critical speeds and can become important for torsional systems that operate with minimal separation margins from resonance frequencies. This work presents various approaches to calculate the stiffening effect. The approaches include empirical and analytical methods described by Nestorides and API 684. An additional method uses a solid model of the motor core and a commercial Finite Element Analysis (FEA) solver to predict steady-state deflection under a torsional load. This in turn allows for a torsional stiffness calculation. Motor core configurations with various shaft diameters, number of spider bars, and spider bar geometries are considered. Good agreement is shown between the FEA results and the Griffith and Taylor method described by Nestorides. The other methods considered, including the calculation method described in API 684, show generally poor agreement with the FEA torsional stiffness results for the webbed shaft geometries studied.
Identification of Bearing Stiffness and Damping Coefficients Using Phase-Plane Diagrams
Authors: Jáuregui Juan C. , San Andrés Luis , De Santiago Oscar
Published: December 2013

The reliable identification of dynamic parameters in mechanical systems remains a big challenge, in particular for nonlinear systems. There is not a single mathematical model encompassing the universe of most systems. From a practical point of view, the identification of system parameters depends on the measurement data as well as on the reference model.

This paper presents a novel method for identifying the dynamic parameters of a gas bearing, whose force coefficients are strong functions of frequency. The method is based on the analysis of the phase diagram with the model assuming a mass-damper-spring system with time-dependent force coefficients. The phase diagram could be implemented electronically for on line monitoring and ready fault detection.
Detection of Unsteady Flow in a Kaplan Hydraulic Turbine Using Machine Mechanical Model and Rotor Measured Vibrations
Authors: Pennacchi Paolo , Vania Andrea , Chatterton Steven , Tanzi Ezio
Published: December 2013

Hydraulic stability is one of the key problems during the design stage of hydraulic turbines. Despite of modern computational tools that help to define dangerous operating conditions and optimize runner design, hydraulic instabilities may fortuitously arise during the turbine life, as a consequence of variable and different operating conditions at which a hydraulic turbine can be subject.

In general, the presence of unsteady flow reveals itself in two different ways: at small flow rate, the swirling flow in the draft tube conical inlet occupies a large portion of the inlet and causes a strong helical vortex rope; at large flow rate conditions the unsteady flow starts midway and causes a breakdownlike vortex bubble, followed by weak helical waves.

In any case, hydraulic instability causes mechanical effects on the runner, on the whole turbine and on the draft tube, which may eventually produce severe damages on the turbine unit and whose most evident symptoms are vibrations. This notwithstanding, condition monitoring systems seldom are installed on this purpose in hydraulic power plants and no examples are reported in literature about the use of model-based methods to detect hydraulic instability onset.

In this paper, by taking the advantage of a testing campaign performed during the commissioning of a 23 MW Kaplan hydraulic turbine unit, a rotordynamic model-based method is proposed. The turbine was equipped by proximity and vibration velocity probes, that allowed measuring lateral and axial vibrations of the shaft-line, under many different operating conditions, including also some off-design ones. The turbine mechanical model, realized by means of finite beam elements and considering lateral and axial degrees of freedom, is used to predict turbine unit response to the unsteady flow. Mechanical system response is then compared to the measured one and the possibility to detect instability onset, especially in real-time, is discussed.
Development of an Experimental Setup for Double Rotor HAWT Investigation
Authors: Al-Abadi Ali , Ertunç Özgür , Epple Philipp , Koerbel Wolfram , Delgado Antonio
Published: December 2013

An experimental set-up was designed and constructed to study the performance of single and double rotor Horizontal Axis Wind Turbines (HAWT) configurations. Different tip speed ratios (TSR) were tested under varying wind loadings. The experimental study was carried out in order to investigate the HAWT performance and thereby increase its aerodynamics efficiency. Another setup was built to measure the torque rotational speed characteristic of the generator. The double rotor configuration was chosen intentionally to study the efficiency improvements when the second downstream rotor extracts the kinetic energy dismissed by the upstream rotor. The study showed that the power coefficient can be indeed increased about 50% with a double rotor HAWT configuration, and the power gained from a counter rotating rotor is higher than that of a co-rotating rotor owing to the effect of the wake of the upstream rotor. In addition, a theoretical analysis of wake effect of the upstream rotor on the downstream rotor including the effect of the distance between the two rotors on the total power coefficient was made and investigated experimentally in order to estimate the optimum distance between the two rotors.
Model Verification and Validation Concepts for a Probabilistic Fracture Assessment Model to Predict Cracking of Knife Edge Seals in the Space Shuttle Main Engine High Pressure Oxidizer
Authors: Pai Shantaram S. , Riha David S.
Published: December 2013

Physics-based models are routinely used to predict the performance of engineered systems to make decisions such as when to retire system components, how to extend the life of an aging system, or if a new design will be safe or available. Model verification and validation (V&V) is a process to establish credibility in model predictions. Ideally, carefully controlled validation experiments will be designed and performed to validate models or submodels. In reality, time and cost constraints limit experiments and even model development. This paper describes elements of model V&V during the development and application of a probabilistic fracture assessment model to predict cracking in space shuttle main engine high-pressure oxidizer turbopump knife-edge seals.

The objective of this effort was to assess the probability of initiating and growing a crack to a specified failure length in specific flight units for different usage and inspection scenarios. The probabilistic fracture assessment model developed in this investigation combined a series of submodels describing the usage, temperature history, flutter tendencies, tooth stresses and numbers of cycles, fatigue cracking, nondestructive inspection, and finally the probability of failure. The analysis accounted for unit-to-unit variations in temperature, flutter limit state, flutter stress magnitude, and fatigue life properties. The investigation focused on the calculation of relative risk rather than absolute risk between the usage scenarios. Verification predictions were first performed for three units with known usage and cracking histories to establish credibility in the model predictions. Then, numerous predictions were performed for an assortment of operating units that had flown recently or that were projected for future flights. Calculations were performed using two NASA-developed software tools: NESSUS® for the probabilistic analysis, and NASGRO® for the fracture mechanics analysis. The goal of these predictions was to provide additional information to guide decisions on the potential of reusing existing and installed units prior to the new design certification.
Controlling Long-Term Signaling: Receptor Dynamics Determine Attenuation and Refractory Behavior of the TGF-β Pathway
Authors: Vizán Pedro , Miller Daniel S. J. , Gori Ilaria , Das Debipriya , Schmierer Bernhard , Hill Caroline S.
Published: December 2013

Ligand binding, but not receptor activity, results in desensitization and long-term dampening of cellular responsiveness to TGF-β.
Hedgehog View to a Kill
Authors: Hurtley Stella M.
Published: December 2013

T cell receptor stimulation activates Hedgehog signaling to arm cytotoxic T cells with the labile actin needed for killing.
Not Too Much, Not Too Little
Authors: Hines Pamela J.
Published: December 2013

A microRNA expressed in adult neurons affects movement by modulating neuronal signaling networks and excitability.
Vaginal Epithelial Cell-Derived S100 Alarmins Induced by Candida albicans via Pattern Recognition Receptor Interactions Are Sufficient but Not Necessary for the Acute Neutrophil Response during Experimental Vaginal Candidiasis
Authors: Yano Junko , Palmer Glen E. , Eberle Karen E. , Peters Brian M. , Vogl Thomas , McKenzie Andrew N. , Fidel Paul L.
Published: December 2013

Vulvovaginal candidiasis (VVC), caused byCandida albicans, affects women worldwide. Animal and clinical studies suggest that the immunopathogenic inflammatory condition of VVC is initiated by S100 alarmins in response toC. albicans, which stimulate polymorphonuclear neutrophil (PMN) migration to the vagina. The purpose of this study was to extend previousin vitrodata and determine the requirement for the alarmin S100A8 in the PMN response and to evaluate pattern recognition receptors (PRRs) that initiate the response. For the former, PMN migration was evaluatedin vitroorin vivoin the presence or absence of S100 alarmins initiated by several approaches. For the latter, vaginal epithelial cells were evaluated for PRR expression andC. albicans-induced S100A8 and S100A9 mRNAs, followed by evaluation of the PMN response in inoculated PRR-deficient mice. Results revealed that, consistent with previously reportedin vitrodata, eukaryote-derived S100A8, but not prokaryote-derived recombinant S100A8, induced significant PMN chemotaxisin vivo. Conversely, a lack of biologically active S100A8 alarmin, achieved by antibody neutralization or by using S100A9−/−mice, had no effect on the PMN responsein vivo. In PRR analyses, whereas Toll-like receptor 4 (TLR4)- and SIGNR1-deficient vaginal epithelial cells showed a dramatic reduction inC. albicans-induced S100A8/S100A9 mRNAsin vitro, inoculated mice deficient in these PRRs showed PMN migration similar to that in wild-type controls. These results suggest that S100A8 alarmin is sufficient, but not necessary, to induce PMN migration during VVC and that the vaginal PMN response toC. albicansinvolves PRRs in addition to SIGNR1 and TLR4, or other induction pathways.
G Proteins Gαi1/3Are Critical Targets for Bordetella pertussis Toxin-Induced Vasoactive Amine Sensitization
Authors: Diehl Sean A. , McElvany Benjamin , Noubade Rajkumar , Seeberger Nathan , Harding Brock , Spach Karen , Teuscher Cory
Published: December 2013

Pertussis toxin (PTX) is an AB5-type exotoxin produced by the bacteriumBordetella pertussis, the causative agent of whooping cough.In vivointoxication with PTX elicits a variety of immunologic and inflammatory responses, including vasoactive amine sensitization (VAAS) to histamine (HA), serotonin (5-HT), and bradykinin (BDK). Previously, by using a forward genetic approach, we identified the HA H1receptor (Hrh1/H1R) as the gene in mice that controls differential susceptibility toB. pertussisPTX-induced HA sensitization (Bphs). Here we show, by using inbred strains of mice, F1hybrids, and segregating populations, that, unlike Bphs, PTX-induced 5-HT sensitivity (Bpss) and BDK sensitivity (Bpbs) are recessive traits and are separately controlled by multiple loci unlinked to 5-HT and BDK receptors, respectively. Furthermore, we found that PTX sensitizes mice to HA independently of Toll-like receptor 4, a purported receptor for PTX, and that the VAAS properties of PTX are not dependent upon endothelial caveolae or endothelial nitric oxide synthase. Finally, by using mice deficient in individual Gαi/oG-protein subunits, we demonstrate that Gαi1and Gαi3are the criticalin vivotargets of ADP-ribosylation underlying VAAS elicited by PTX exposure.
Making Connections: Service-Learning in Introductory Cell and Molecular Biology
Authors: Begley Gail S.
Published: December 2013

This report describes service-learning in a first-year majors biology course in which students serve throughout the semester with community partners for an average of 25 hours/student. All of the partnerships are based on providing engaging hands-on biology activities for youth in underserved urban areas surrounding the campus. Students in the course have designed new lessons and activities, supported biology labs, mentored younger students, and facilitated afterschool science clubs. Throughout the course, integration between the students’ service experience in the community and their learning in the course is emphasized. This is accomplished in multiple ways including class discussion, group activities, feedback from the instructor and teaching assistant, and weekly blogs. A three-year average of anonymous university-wide course evaluations suggested that students in this service-learning course considered their biology course to be highly rigorous. In both blogs and anonymous surveys students reported that their service and its integration with the course not only advanced their professional skills and sense of community engagement, but also enhanced their learning in biology.
Broad Spectrum Bioluminescence: Shine On!Review of:	Bioluminescence: Living lights, lights for living,	1st ed.;	WilsonThérèseWoodland HastingsJ.; (	2013).	Harvard Press,	Cambridge, MA.	185 pages.
Authors: Mixter Phil
Published: December 2013

Review of:
Bioluminescence: Living lights, lights for living, 1st ed.;
Thérèse Wilson and J. Woodland Hastings; (2013). Harvard Press, Cambridge, MA. 185 pages.
A Historical Perspective on Commerce and the Spread of DiseaseReview of:	Contagion: How Commerce Has Spread Disease;	HarrisonMark; (	2012).	Yale University Press,	New Haven, CT. Hardcover,	376 pages.
Authors: Govindan Brinda
Published: December 2013

Review of:
Contagion: How Commerce Has Spread Disease;
Mark Harrison; (2012). Yale University Press, New Haven, CT. Hardcover, 376 pages.
A Textbook to Help Students Think Like MicrobiologistsReview of:	Microbiology,	1st ed.;	WessnerDavid R.DupontChristineCharlesTrevor C.; (	2013).	John Wiley & Sons, Inc.,	Hoboken, New Jersey.	960 pages.
Authors: Etchberger Lianna
Published: December 2013

Review of:
Microbiology, 1st ed.;
David R. Wessner, Christine Dupont, and Trevor C. Charles; (2013). John Wiley & Sons, Inc., Hoboken, New Jersey. 960 pages.
From the Editor-in-Chief: Scope Expansion and New Editor-in-Chief for 2014
Authors: Woolverton Christopher J.
Published: December 2013

JMBE
Editor-in-Chief Christopher Woolverton reflects on all that the Journal has accomplished in the last five years and announces two exciting changes for 2014 and beyond: an expansion of the Journal’s scope and a change in leadership.
Pseudomelanosis duodeni in a postrenal transplant patient
Authors: Schuerle Theresa , Aoun Elie , Clarke Kofi
Published: December 2013

Pseudomelanosis duodeniis a rare entity characterised by dark pigmented intracellular granules seen within macrophages that lie within the lamina propria of the duodenal villi. There is no known treatment, and the clinical significance and long-term sequelae of this entity are unclear. We present a case ofpseudomelanosis duodeniin a 54-year-old woman who presented with a 1-month history of nausea, vomiting and non-bloody diarrhoea. The medical history was significant for diabetes mellitus type 2, end-stage renal disease status postkidney transplant, hypertension, anaemia of chronic disease and hypothyroidism. A gastroduodenal endoscopy revealed pigmented dark lesions in the duodenal mucosa. Biopsies from the second part of the duodenum and duodenal bulb showed pigmented macrophages in the lamina propria. The findings were consistent with duodenal melanosis. In spite of renal transplant with normalisation of renal function, the duodenal melanosis persists, which raises questions on the role of renal impairment in this entity.
Assessing the health-related outcomes and correlates of active transportation in children and youth
Authors: Larouche Richard
Published: December 2013

Active school transport (AST; e.g., the use of nonmotorized modes such as walking and cycling to travel to/from school) is an inexpensive, accessible and environmentally friendly source of physical activity (PA). This dissertation addresses 2 overarching objectives: (i) to measure the relationships of AST with PA and health-related outcomes; and (ii) to examine the correlates of AST immediately before and after the transition from primary to secondary school (the “school transition”). First, a systematic review revealed increasing evidence showing that AST is associated with greater daily PA levels, and that cycling to/from school is associated with higher cardiovascular fitness. Cycling for transportation (not only for school trips) was also associated with lower values for total cholesterol and total cholesterol/high-density lipoprotein-cholesterol ratio in the nationally representative 2007–2009 Canadian Health Measures Survey. Moreover, the present dissertation provides preliminary evidence suggesting that AST may help attenuate the decline in PA across the school transition. However, the relationship between AST and body composition indicators remains unclear. With respect to the correlates of AST, distance was the strongest barrier to AST at both time points, but several road safety concerns and the perception of having too much stuff to carry were also associated with engagement in motorized travel. At follow-up, AST was more common in children whose parents owned less than 2 cars. In contrast, children were more likely to engage in AST if their parents reported that they chose to live in their current neighbourhood so that their children could walk or bike to school. The associations of neighbourhood walkability (as measured with the Walk Score application ( www.walkscore.com )) with AST and PA were generally stronger after the school transition. While AST may improve health among children and youth, an ecological approach targeting multiple levels of influence will likely be needed to alleviate current barriers to AST.
DIGITAL DOUBLE BARRIER OPTIONS: SEVERAL BARRIER PERIODS AND STRUCTURE FLOORS
Authors: ALTAY SÜHAN , GERHOLD STEFAN , HAIDINGER RAINER , HIRHAGER KARIN
Published: December 2013

We determine the price of digital double barrier options with an arbitrary number of barrier periods in the Black–Scholes model. This means that the barriers are active during some time intervals, but are switched off in between. As an application, we calculate the value of a structure floor for structured notes whose individual coupons are digital double barrier options. This value can also be approximated by the price of a corridor put.
Static analysis and optimization of semantic web queries
Authors: Letelier Andrés , Pérez Jorge , Pichler Reinhard , Skritek Sebastian
Published: December 2013

Static analysis is a fundamental task in query optimization. In this article we study static analysis and optimization techniques for SPARQL, which is the standard language for querying Semantic Web data. Of particular interest for us is the
optionality
feature in SPARQL. It is crucial in Semantic Web data management, where data sources are inherently incomplete and the user is usually interested in partial answers to queries. This feature is one of the most complicated constructors in SPARQL and also the one that makes this language depart from classical query languages such as relational conjunctive queries. We focus on the class of well-designed SPARQL queries, which has been proposed in the literature as a fragment of the language with good properties regarding query evaluation. We first propose a tree representation for SPARQL queries, called pattern trees, which captures the class of well-designed SPARQL graph patterns. Among other results, we propose several rules that can be used to transform pattern trees into a simple normal form, and study equivalence and containment. We also study the evaluation and enumeration problems for this class of queries.
Evaluation of a Hybrid Approach for Efficient Provenance Storage
Authors: Xie Yulai , Muniswamy-Reddy Kiran-Kumar , Feng Dan , Li Yan , Long Darrell D. E.
Published: December 2013

Provenance is the metadata that describes the history of objects. Provenance provides new functionality in a variety of areas, including experimental documentation, debugging, search, and security. As a result, a number of groups have built systems to capture provenance. Most of these systems focus on provenance collection, a few systems focus on building applications that use the provenance, but all of these systems ignore an important aspect: efficient long-term storage of provenance.

In this article, we first analyze the provenance collected from multiple workloads and characterize the properties of provenance with respect to long-term storage. We then propose a hybrid scheme that takes advantage of the graph structure of provenance data and the inherent duplication in provenance data. Our evaluation indicates that our hybrid scheme, a combination of Web graph compression (adapted for provenance) and dictionary encoding, provides the best trade-off in terms of compression ratio, compression time, and query performance when compared to other compression schemes.
On energy-efficient trap coverage in wireless sensor networks
Authors: Chen Jiming , Li Junkun , He Shibo , He Tian , Gu Yu , Sun Youxian
Published: December 2013

In wireless sensor networks (WSNs), trap coverage has recently been proposed to trade off between the availability of sensor nodes and sensing performance. It offers an efficient framework to tackle the challenge of limited resources in large-scale sensor networks. Currently, existing works only studied the theoretical foundation of how to decide the deployment density of sensors to ensure the desired degree of trap coverage. However, practical issues, such as how to efficiently schedule sensor node to guarantee trap coverage under an arbitrary deployment, are still left untouched. In this article, we formally formulate the
Minimum Weight Trap Cover Problem
and prove it is an NP-hard problem. To solve the problem, we introduce a bounded approximation algorithm, called
Trap Cover Optimization
(TCO) to schedule the activation of sensors while satisfying specified trap coverage requirement. We design
Localized Trap Coverage Protocol
as the localized implementation of TCO. The performance of Minimum Weight Trap Coverage we find is proved to be at most
O
(ρ) times of the optimal solution, where ρ is the density of sensor nodes in the region. To evaluate our design, we perform extensive simulations to demonstrate the effectiveness of our proposed algorithm and show that our algorithm achieves at least 14% better energy efficiency than the state-of-the-art solution.
CTP
Authors: Gnawali Omprakash , Fonseca Rodrigo , Jamieson Kyle , Kazandjieva Maria , Moss David , Levis Philip
Published: December 2013

We describe CTP, a collection routing protocol for wireless sensor networks. CTP uses three techniques to provide efficient, robust, and reliable routing in highly dynamic network conditions. CTP's link estimator accurately estimates link qualities by using feedback from both the data and control planes, using information from multiple layers through narrow, platform-independent interfaces. Second, CTP uses the Trickle algorithm to time the control traffic, sending few beacons in stable topologies yet quickly adapting to changes. Finally, CTP actively probes the topology with data traffic, quickly discovering and fixing routing failures. Through experiments on 13 different testbeds, encompassing seven platforms, six link layers, and multiple densities and frequencies, and detailed observations of a long-running sensor network application that uses CTP, we study how these three techniques contribute to CTP's overall performance.
DepSky
Authors: Bessani Alysson , Correia Miguel , Quaresma Bruno , André Fernando , Sousa Paulo
Published: December 2013

The increasing popularity of cloud storage services has lead companies that handle critical data to think about using these services for their storage needs. Medical record databases, large biomedical datasets, historical information about power systems and financial data are some examples of critical data that could be moved to the cloud. However, the reliability and security of data stored in the cloud still remain major concerns. In this work we present DepSky, a system that improves the availability, integrity, and confidentiality of information stored in the cloud through the encryption, encoding, and replication of the data on diverse clouds that form a cloud-of-clouds. We deployed our system using four commercial clouds and used PlanetLab to run clients accessing the service from different countries. We observed that our protocols improved the perceived availability, and in most cases, the access latency, when compared with cloud providers individually. Moreover, the monetary costs of using DepSky in this scenario is at most twice the cost of using a single cloud, which is optimal and seems to be a reasonable cost, given the benefits.
A system-level infrastructure for multidimensional MP-SoC design space co-exploration
Authors: Jia Zai Jian , Bautista Tomás , Núñez Antonio , Pimentel Andy D. , Thompson Mark
Published: December 2013

In this article, we present a flexible and extensible system-level MP-SoC design space exploration (DSE) infrastructure, called NASA. This highly modular framework uses well-defined interfaces to easily integrate different system-level simulation tools as well as different combinations of search strategies in a simple plug-and-play fashion. Moreover, NASA deploys a so-called dimension-oriented DSE approach, allowing designers to configure the appropriate number of, well-tuned and possibly different, search algorithms to simultaneously co-explore the various design space dimensions. As a result, NASA provides a flexible and re-usable framework for the systematic exploration of the multidimensional MP-SoC design space, starting from a set of relatively simple user specifications. To demonstrate the capabilities of the NASA framework and to illustrate its distinct aspects, we also present several DSE experiments in which, for example, we compare NASA configurations using a single search algorithm for all design space dimensions to configurations using a separate search algorithm per dimension. These proof-of-concept experiments indicate that the latter multidimensional co-exploration can find better design points and evaluates a higher diversity of design alternatives as compared to the more traditional approach of using a single search algorithm for all dimensions.
An analytical model for on-chip interconnects in multimedia embedded systems
Authors: Wu Yulei , Min Geyong , Zhu Dakai , Yang Laurence T.
Published: December 2013

The traffic pattern has significant impact on the performance of network-on-chip. Many recent studies have shown that multimedia applications can be supported in on-chip interconnects. Driven by the motivation of evaluating on-chip interconnects in multimedia embedded systems, a new analytical model is proposed to investigate the performance of the fat-tree based on-chip interconnection network under bursty multimedia traffic and nonuniform message destinations. Extensive simulation experiments are conducted to validate the accuracy of the model, which is then adopted as a cost-efficient tool to investigate the effects of bursty multimedia traffic with nonuniform destinations on the network performance.