bluuebunny/crossref_metadata_2025 huggingface dataset:
Impaction Efficiencies of Evaporating Kerosene Droplets on Vee-Gutter Flame Stabilizer
Authors: Qing-Fan Zhang , Zu-Kai Kong , Qi-Hong Zhou
Published: April 2015

Prediction of the impaction efficiency of evaporating kerosense droplets on vee-gutter were carried out by solving numerically the equations describing the flow field passing over a vee-gutter, the droplet evaporation model and the droplet motion. All the results obtained under conditions which are similar to afterburners in aircraft propulsion systems were then summarized by dimensional analysis, yielding an expression for calculating the impaction efficiency. It is shown from the expression that the key factor influencing the impaction efficiency is the initial droplet diameter, i.e., the impaction efficiency is proportional to the power of 1.44 of the initial droplet diameter; The impaction efficiency decreases with increasing ambient temperature and pressure, the distance from the droplet injection section to the vee-gutter and the width of the vee-gutter and increases with the stream velocity. The expression obtained in this paper can be used to estimate approximately the impaction efficiency in afterburners of aircraft propulsion systems.
Stratified Charge Rotary Engine for General Aviation
Authors: Mount Robert E. , Parente Anthony M. , Hady William F.
Published: April 2015

Exciting developments have occurred over the past two years in the technological status and production aspects of Stratified Charge Rotary Engines. A program is currently underway for the development, certification and production of a 400 HP aircraft engine in early 1990. The joint program is being conducted by John Deere’s Rotary Engine Division and AVCO Lycoming Williamsport Division. The engine will offer to the General Aviation community Jet-A fuel capability at substantial cost savings, improved altitude capability and lower fuel consumption over turbine power plants. Application to fixed wing and rotary wing aircraft are planned.

Other stratified charge rotary engine development work in progress involves ground power units, airborne APU’s, shipboard gensets and vehicular engines, supported by Deere production capabilities and DOD interests. Technology enablement efforts by NASA, aimed at highly advanced output and efficiency are in progress leading toward revolutionary engine capability for aircraft and other applications.
Production and Development of Secondary Flows and Losses Within Two Types of Straight Turbine Cascades: Part 1 — A Stator Case
Authors: Yamamoto A.
Published: April 2015

The present study intends to give some experimental information on secondary flows and on the associated total pressure losses occurring within turbine cascades.

Part 1 of the paper describes the mechanism of production and development of the loss caused by secondary flows in a straight stator cascade with a turning angle of about 65°. A full representation of superimposed secondary flow vectors and loss contours is given at serial fourteen traverse planes located throughout the cascade, which shows the mechanism clearly. Distributions of static pressures and of the loss on various planes close to blade surfaces and close to an endwall surface are given to show the loss accumulation process over the surfaces of the cascade passage. Variation of mass-averaged flow angle, velocity and loss through the cascade, and evolution of overall loss from upstream to downstream of the cascade are also given.

Part 2 of the paper describes the mechanism in a straight rotor cascade with a turning angle of about 102°.
More Effective Control for Centrifugal Gas Compressors Operating in Parallel
Authors: Staroselsky Naum , Ladin Lawrence
Published: April 2015

Parallel Operating centrifugal gas compressors are major elements in the chemical industry, in oil production and in natural gas gathering, injection, separation, transmission and LNG production. Large energy savings, reduced repairs and improved automation are possible with more effective solutions for compressor station control.

The authors suggest an improved definition of compressor energy efficiency. They analyze several common approaches to control of parallel compressors and evaluate them in terms of energy efficiency, stability of control, equipment protection and level of automation. An improved system developed by one of the authors will be described theoretically and with an example from field operation.
Effects of Probe Supports on Measurements in Steam Turbines
Authors: Squire L. C.
Published: April 2015

This paper presents the results of an investigation of the interference effects produced within the blade passages due to the support systems used to position probes downstream of the trailing edge in the interblade regions. The support systems studied consist of simple circular rods and it is shown that the presence of these probe stems can have a very large effect on the flow through the blade passage. In all cases the presence of the probe stem reduces the mass flow through the passage directly upstream of the probe with, in some cases, the flow reduction being so great as to eliminate all regions of supersonic flow on the suction surface of the blade. The paper also describes the results of preliminary tests aimed at reducing these effects; further work on this aspect of the study is continuing.
Optimization of Industrial Centrifugal Compressors: Part 6B — Studies in Component Performance — Laboratory Development of Eight Stages From 1972 to 1982
Authors: Japikse David , Osborne Colin
Published: April 2015

Examples of measured performance for various designs are contrasted against the original design goals. Overall performance and test procedures are detailed in Part 6A (1). The results of detailed interstage measurements are presented herein. Diffusion levels within the compressor components are quantified. The critical role of the laboratory in successful product development is illustrated. Manufacturing procedures (castings vs. machining, thick leading edges, rough surfaces, etc.) are shown to significantly influence performance.
A Model for Closing the Inviscid Form of the Average-Passage Equation System
Authors: Adamczyk John J. , Mulac Richard A. , Celestina Mark L.
Published: April 2015

A mathematical model is proposed for closing or mathematically completing the system of equations which describes the time-average flow field through the blade passages of multistage turbomachinery. These equations referred to as the average-passage equation system govern a conceptual model which has proven useful in turbomachinery aerodynamic design and analysis. The closure model is developed so as to insure a consistency between these equations and the axisymmetric through-flow equations. The closure model was incorporated into a computer code for use in simulating the flow field about a high-speed counter-rotating propeller and a high-speed fan stage. Results from these simulations are presented.
Study and Experiments of a Small Radial Turbine for Auxiliary Power Units
Authors: Ribaud Y. , Mischel C.
Published: April 2015

The design of a small inward flow turbine with a 3.6 expansion ratio has been undertaken by MICROTURBO, in cooperation with ONERA for calculations and test results analysis.

Initially, the purpose and constraints of this study are underlined. Preliminary calculations have led to the design of the blade shape of the Nozzle Guide Vane and of the rotor. Following this, the results of the quasi-3D-flow computations, performed for the stator and the rotor, are given. Both the cold bench tests on this turbine and the corresponding hot tests on the turboshaft engine enable performances to be checked. The value of the calculations is confirmed when we look at the high total and static adiabatic efficiencies obtained. These good results are encouraging for the future use of this kind of turbomachine.
Analysis and Solution of a Non-Synchronous Vibration Problem in the Last Row Turbine Blade of a Large Industrial Combustion Turbine
Authors: Scalzo A. J. , Allen J. M. , Antos R. J.
Published: April 2015

This paper presents the analysis and corrective action taken to solve a flow induced non-synchronous vibration failure problem encountered in the last stage rotating blade in a large industrial combustion turbine. A description of the fatigue failures and of temporary operation restrictions that precluded further failure is given. The results from a strain gauge telemetry test are presented which show that failure was due to high vibratory stress excursions from fundamental mode vibration, which resulted from broad band buffeting excitations and very low aerodynamic damping at high levels of power and mass flow. From these data, design criteria were developed for designing a retrofittable blade that removed the operating restrictions. Telemetry test results (from the same turbine), which verified the new design, are also briefly presented and discussed. This investigation shows that the design of future high performance exhaust end combustion turbine blading must take into account non-synchronous excitation (buffeting) and the aeroelastic interaction between blade structure and flow, in addition to the synchronous excitations traditionally allowed for in the design process.
Viscous/Inviscid Computations of Transonic Separated Flows Over Solid and Porous Cascades
Authors: Olling Charles R. , Dulikravich George S.
Published: April 2015

A complete viscous-inviscid interaction is performed that reliably computes steady two-dimensional, subsonic and transonic attached and separated flows for cascades of airfoils. A full-potential code was coupled with both a laminar/transition/ turbulent integral boundary-layer/turbulent wake code and the finite-difference boundary-layer code using the semi-inverse methods of Carter and Wigton. The transpiration coupling concept was applied with an option for a porous airfoil with passive and active physical transpiration. Examples are presented which demonstrate that such flows can be calculated with engineering accuracy by these methods. Carter’s update formula gives smoother solutions for a strong shock that Wigton’s update formulas, although Wigton’s formulas are preferred in the early coupling cycles. The computations show that passive physical transpiration can lead to a lower drag coefficient and higher lift coefficient, a weaker shock and elimination of shock-induced separation. The extent of the porous region and permeability factor distribution of the porous region must be chosen carefully if these improvements are to be achieved.
Engine Component Life Prediction Methodology for Conceptual Design Investigations
Authors: Cyrus John D.
Published: April 2015

The increasing emphasis on engine durability requires that an analytical capability be acquired to assess engine component lives during the conceptual/preliminary design phases. A generalized methodology has been developed to provide a fundamental understanding of the impact of engine design decisions, material selections, and a detailed consideration of engine usage for critical gas turbine engine components.
Effects of Tip Clearance on Blade Loading in a Planar Cascade of Turbine Blades
Authors: Sjolander Steen A. , Amrud Kim K.
Published: April 2015

The paper examines in detail the structure of the tip leakage flow and its effect on the blade loading in a large-scale planar cascade of turbine blades. The tip clearance was varied from 0.0 to 2.86% of the blade chord. One of the blades is instrumented with 14 rows of 73 static taps which allowed a very detailed picture of the loading near the tip to be obtained. In addition to the measurements, extensive flow visualization was conducted using both smoke and surface oil flow. A new feature found in the present experiment was the formation of multiple, discrete tip-leakage vortices as the clearance was increased. Their presence is clearly evident from the surface oil flow and they account for the multiple suction peaks found in the blade pressure distributions. Integration of the pressure distributions showed that for larger values of the clearance the blade loading increases as the tip is approached and only begins to decline very near the tip. The increase was found to occur primarily in the axial component of the force.
Development of HIDEC Adaptive Engine Control Systems
Authors: Landy R. J. , Yonke W. A. , Stewart J. F.
Published: April 2015

The NASA Ames-Dryden Flight Research Facility is sponsoring a flight research program designated Highly Integrated Digital Electronic Control (HIDEC), whose purpose is to develop integrated flight-propulsion control modes and evaluate their benefits in flight on the NASA F-15 test aircraft.

The Adaptive Engine Control System (ADECS I) is one phase of the HIDEC program. ADECS I involves uptrimming the P&W Engine Model Derivative (EMD) PW1128 engines to operate at higher engine pressure ratios (EPR) and produce more thrust. In a follow-on phase, called ADECS II, a constant thrust mode will be developed which will significantly reduce turbine operating temperatures and improve thrust specific fuel consumption.

A Performance Seeking Control mode is scheduled to be developed. This mode features an onboard model of the engine that will be updated to reflect actual engine performance, accounting for deterioration and manufacturing differences. The onboard engine model, together with inlet and nozzle models, are used to determine optimum control settings for the engine, inlet, and nozzle that will maximize thrust at power settings of intermediate and above and minimize fuel flow at cruise.

The HIDEC program phases are described in this paper with particular emphasis on the ADECS I system and its expected performance benefits. The ADECS II and Performance Seeking Control concepts and the plans for implementing these modes in a flight demonstration test aircraft are also described. The potential pay-offs for these HIDEC modes as well as other integrated control modes are also discussed.
Optimum Design Technique for Rotating Wheels
Authors: Hattori Toshio , Ohnishi Hiroo , Taneda Motoharu
Published: April 2015

Compressor rotors and turbine rotors are subject to centrifugal and thermal loads. These loads increase proportionally with tip speed, pressure ratio and gas temperature. On the other hand, the rotor weight must be lessened to improve rotor dynamics and restrict bearing load. Thus, an optimum design technique is required, which offers the lighest possible wheel shape under the stress limit restriction.

This paper introduces an optimum design system developed for turbo machinery rotors, and discusses several application results. The sequential linear programming method is used in the optimizing process, and centrifugal and thermal stress analyses of variable thickness rotating wheels are performed using Donath’s method. This system’s validity is confirmed by application to uniform strength rotating disk problems and comparison with analytical results. This optimum design program is then applied to the design of axial flow compressor wheels.
Seamless Fiber Metal Abradables: A New Concept in Engine Seals
Authors: Beaton M. S. , Tolokan R. P.
Published: April 2015

Fiber metal abradable seals are used for clearance control in gas turbine engines. Abradable seals accommodate rubs between the rotating system and the engine housing. Abradable seals also block the passage of air around the rotating system. Conventional seals are fabricated in flat sheet and formed into ring shape, with a seam in the ring axis direction. Seamless seals are fabricated in ring form with no seam. For conventional fiber metal seals, the seal material properties are adjusted to best suit the requirements of particular applications. The seamless metal fiber seals offer improved knife edge abradability and air flow blockage performance compared to the conventional materials. The seamless seals respond to knife edge rub interaction in the same manner as conventional seals of 10 to 20% lower density. The seamless seal blocks air flow with approximately twice the effectiveness of conventional seals. Seamless seals are comparable in cost to conventional seals.
Impact of Higher Freeze Point Fuels on Naval Aircraft Operations
Authors: Kamin R. A. , McConnell P. M.
Published: April 2015

Refinery process studies have indicated that the relaxation of the JP-5 freeze point specification is a viable means of increasing jet fuel availability. The Naval Air Propulsion Center is investigating the impact of higher freeze point fuels on naval aircraft operations. Six fuels, with freeze points ranging from −55°F to +10°F, were tested in two instrumented external fuel tanks. Thirty hours of flight test and one hundred hours of wind tunnel test data have been accumulated. This information is being used in conjunction with laboratory and bench scale test data to support the development of a three dimensional computer code. This code will predict fuel cool down and hold-up (unpumpable frozen fuel) for any fuel tank geometry during a mission. Initial results indicate that the current JP-5 freeze point specification of −51°F is conservative and could be safely relaxed.
The Application of a Unique Flow Modeling Technique to Complex Combustion Systems
Authors: Waslo J. , Hasegawa T. , Hilt M. B.
Published: April 2015

This paper describes the application of a unique three-dimensional water flow modeling technique to the study of complex fluid flow patterns within an advanced gas turbine combustor. The visualization technique uses light scattering, coupled with realtime image processing, to determine flow fields. Additional image processing is used to make concentration measurements within the combustor.
Enclosed Swirl Flames: Interaction Between Swirlers in Lean Primary Zones
Authors: Ahmad N. T. , Andrews G. E.
Published: April 2015

Three axial vane swirlers were investigated in a simulated sector of an annular combustor. The influence of co and counter rotating swirl on combustion emissions and flame stability are studied with kerosene as the fuel and inlet temperatures up to 800K. Comparison is made with one of the swirlers in a single swirler can combustor. The results show that the influence of the relative swirl direction does not influence the flame stability but does influence the combustion efficiency and NOx emissions. However, both systems are superior to a single swirler can combustor.
Simulation of the Heat Transfer in a Gas Turbine Combustor Fueled With Coal-Water Mixture: Part 2 — Model Predictions and Experimental Data
Authors: Farag Ihab H. , Vaillancourt Joseph L.
Published: April 2015

Data was obtained from the combustion of coal derived fuels in a 30 inch diameter, 4 foot long bench scale atmospheric unit fueled with CWF. The data is presented and compared with model predictions of ash, temperature, and mole fraction distributions.

A computer model was developed to simulate the heat transfer processes taking place in a gas turbine combustor (GTC) burning a coal water fuel (CWF). It is to predict the species and temperature distribution, the heat flux patterns, and the contribution of both convection and radiation to the total heat transfer rate. This model was verified in part 1 of this paper.
Hot Corrosion Resistance of Chromium Modified Platinum-Aluminide Coating
Authors: Dust M. W. , Deb P. , Boone D. H. , Shankar S.
Published: April 2015

The addition of elements such as Cr or Pt to the diffusion aluminide coatings has been reported to provide increased protectivity under hot corrosion and oxidation environments. Although the structure and corresponding corrosion resistance of Cr or Pt modified aluminides are reasonably understood there is, however, little information available on the combined additions of Cr and Pt or the processing sequences involved. The effects of both Cr and Pt additions to aluminide coatings on the IN-100 nickel-base superalloy substrate under low temperature (700°C) hot corrosion conditions have been studied. In this investigation, it was found that the structure of the Cr modified platinum-aluminide coatings is most dependent on the sequence of modifying element addition which affects the surface composition and resulting LTHC resistance. The optimum Cr-Pt coating is obtained by the Cr-Pt-Al deposition sequence which results in a continuous single PtAl2 phase layer backed up with a high level of Cr at the surface.
Aircraft/Engine Integration for an Advanced Fighter Considering Mission Specifics
Authors: Rauh G. , Anders W.
Published: April 2015

In this paper propulsion system integration is considered for an advanced twin engined, high performance agile air to air fighter aircraft in view of its requirements for extreme flight conditions and maneuvers.

The propulsion system mainly consists of air inlets, engines and nozzle/afterbody systems.

The air inlet, a propulsion subsystem within the aircraft manufacturers responsibility, is physically well integrated with the aircraft flight control system, processing hardware being part of it.

The engine itself, as the most complex propulsion subsystem and not within the aircraft manufacturers responsibility, is to have very simple and clearly defined interfaces with the aircraft. Its integration must therefore be on this basis i.e. functional.

A central utility data bus allows for easy communication between the engine control system and all relevant aircraft systems through a single point interface in normal operation.

This improved communication allows for better performance, operation and handling of the engine.

A special feature of the propulsion system is the vectoring nozzle system with thrust deflection for maneuvers at high angles of attack beyond maximum lift. This system is also integrated with the flight control system.
User Interface Description of a Gas Turbine Control System
Authors: Sreetharan M. , Fistere J.
Published: April 2015

Human factors must be given primary consideration in the design of today’s control systems. It is essential to take into account the characteristics of the human operator, the plant control requirements and the inherent characteristics of the control system.

This paper discusses the objectives of the control interface development task for a turbomachinery microprocessor based control system. It discusses the design issues raised during development, the choices made in the early structuring of the system and selected implementation details that affect the operator interface.

Subjects discussed include:

• Overall Philosophy and Console Arrangement

• Pushbutton vs Keyboard Functions

• Video Display Philosophy and Organization

• Ladder-Diagram Graphic Symbols

• Keyboard Command Philosophy and Structure

• Diagnostic Features and Maintainability
GATOR-GARD: The Process, Coatings, and Turbomachinery Applications
Authors: Lewis Thomas F.
Published: April 2015

The GATOR-GARD® process uses a high temperature, high velocity, ionized gas to deposit metal or ceramic particles on substrate materials. The high particle velocities and their extremely short dwell time at high temperature produces dense, well bonded coatings with unique structures which can be tailored for maximum resistance to wear, erosion and impact.

The selective usage of metal and ceramic thermal sprayed coatings on turbomachinery components for repair or original equipment protection is a cost effective solution to today’s high maintenance costs. GATOR-GARD coatings are used to protect new components from sliding, fretting, and erosive wear from the compressor to the turbine exhaust fairings, at metal temperatures from ambient to more than 1040 degrees C (1900 F). When used for repair of worn components, these coatings improve the life many times over the original equipment.
Trends in Design and Development of Mechanical Drive Power Turbines
Authors: Wilson Jay M.
Published: April 2015

The power turbines that are used with aero-derivative gas generators have been upgraded in response to performance improvements in these gas generators. The manner in which power turbine designs have evolved to cope with higher temperatures and greater work extraction levels is explained. The test program for the latest design is described and typical performance and mechanical development results are presented.
Development of Injection Molded Rotors for Gas Turbine Applications
Authors: Ohnsorg R. , Teneyck M. , Sweeting T.
Published: April 2015

Development of sintered alpha silicon carbide (SASC) gas turbine rotors commenced in 1979 and is being continued through 1986 under the AGT-100 (Advanced Gas Turbine) program where the Allison Gas Turbine Division (AGTD) of General Motors is the prime contractor. Injection molding of a solid one piece rotor was the chosen fabrication technique.

Compound development in connection with the appropriate binder removal process suitable for a wide variety of wall thicknesses were critical steps early in the program. Various molding conditions and injection procedures were evaluated to obtain acceptable rotors. Non-destructive evaluation (NDE) methods as well as destructive measures were used to evaluate molded, baked, and sintered rotors. These results and related processing studies will be discussed in detail.

Current rotors fabricated with the improved procedures show increased molding yield and a lower variability in strength. Rotors have been proof tested to 95,000 rpm (110% of design speed) which is equivalent to about 600 m/s tip speed.
The Extension of Gas Turbine Power Plants to Combined Cycle Power Stations
Authors: Schemenau Wolfgang , Häuser Ulrich
Published: April 2015

In industrial countries as well as in developing countries there is a continuous growth of electricity consumption. The normal way to meet these requirements is the stepwise extension of electricity producing plants. In countries where clean fuel is available at acceptable prices the advantages of combined cycle plants in terms of efficiency and of smooth meeting the requirements can be used.

The following essay concentrates on the influences of design criterias and ambient conditions on efficiency, output and plant cost for the type of CCP which is most frequently excecuted. As a result of an optimization an executed plant is described also with regard to lay out, required space and erection time.
Computational Engine Structural Analysis
Authors: Chamis C. C. , Johns R. H.
Published: April 2015

A significant research activity at the NASA Lewis Research Center is the computational simulation of complex multidisciplinary engine structural problems. This simulation is performed using computational engine structural analysis (CESA) which consists of integrated multidisciplinary computer codes in conjunction with computer post-processing for “problem-specific” application. A variety of the computational simulations of specific cases are described in some detail in this paper. These case studies include (1) aeroelastic behavior of bladed rotors, (2) high velocity impact of fan blades, (3) blade-loss transient response, (4) rotor/stator/squeeze-film/bearing interaction, (5) blade-fragment/rotor-burst containment, and (6) structural behavior of advanced swept turboprops. These representative case studies were selected to demonstrate the breadth of the problems analyzed and the role of the computer including post-processing and graphical display of voluminous output data.
Nondestructive Techniques for Characterizing Mechanical Properties of Structural Materials — An Overview
Authors: Vary Alex , Klima Stanley J.
Published: April 2015

An overview of nondestructive evaluation (NDE) is presented to indicate the availability and application potentials of techniques for quantitative characterization the mechanical properties of structural materials. The purpose of this brief survey is to review NDE techniques that go beyond the usual emphasis on flaw detection and characterization. This survey covers current and emerging NDE techniques that can verify and monitor entrinsic properties (e.g., tensile, shear, and yield strengths; fracture toughness, hardness; ductility; elastic moduli) and underlying microstructural and morphological factors. Most of the techniques described are, at present, neither widely applied nor widely accepted in commerce and industry because they are still emerging from the laboratory. The limitations of the techniques may be overcome by advances in applications research and instrumentation technology and perhaps by accommodations for their use in the design of structural parts.
An Explicit Inverse Design Formulation for Compressible Flow
Authors: Wilson D. E.
Published: April 2015

A new singular integral equation method has been developed for solving the full nonlinear potential flow about an arbitrary body. The method bears some resemblance to conventional integral methods, however it is inherently different in that the surface geometry is contained explicitly in the resulting integral equations. Several analytical results are exploited to reduce the two-dimensional integral equations to a one-dimensional problem on the body surface. The integral equation is inverted so that the airfoil geometry is given as an explicit function of the velocity field. The resulting one-dimensional integral equations are solved numerically and the results are compared with existing theoretical methods for both analysis and inverse design problems.
Subsonic/Transonic Stall Flutter Investigation of an Advanced Low Pressure Compressor
Authors: El-Aini Y. M. , Bankhead H. R. , Meece C. E.
Published: April 2015

The subsonic/transonic stall flutter characteristics of the Pratt & Whitney PW1120 Low Pressure Compressor (LPC), recently have been defined through fan rig tests and a full-scale engine test. Flutter data analyses, based on both empirical and analytical methods, have shown excellent correlations between test results and predictions. While the LPC was demonstrated to be flutter-free over its entire flight envelope, the study indicates the need for continued research in transonic unsteady aerodynamics, particularly, the effects of passage shocks and large leading edge incidence.
Paddling Force Profiles at Different Stroke Rates in Elite Sprint Kayaking
Authors: Gomes Beatriz B. , Ramos Nuno V. , Conceição Filipe A.V. , Sanders Ross H. , Vaz Mário A.P. , Vilas-Boas João Paulo
Published: April 2015

In sprint kayaking the role that paddling technique plays in optimizing paddle forces and resultant kayak kinematics is still unclear. The aim of this study was to analyze the magnitude and shape of the paddle force–time curve at different stroke rates, and their implications for kayak performance. Ten elite kayak paddlers (5 males and 5 females) were analyzed while performing 2000-m on-water trials, at 4 different paces (60, 80, and 100 strokes per minute, and race pace). The paddle and kayak were instrumented with strain gauges and accelerometers, respectively. For both sexes, the force–time curves were characterized at training pace by having a bell shape and at race pace by a first small peak, followed by a small decrease in force and then followed by a main plateau. The force profile, represented by the mean force/peak force ratio, became more rectangular with increasing stroke rate (F[3,40] = 7.87, P < .01). To obtain a rectangular shape to maximize performance, kayak paddlers should seek a stronger water phase with a rapid increase in force immediately after blade entry, and a quick exit before the force dropping far below the maximum force. This pattern should be sought when training at race pace and in competition.
The Effect of Thigh Marker Placement on Knee Valgus Angles in Vertical Drop Jumps and Sidestep Cutting
Authors: Mok Kam-Ming , Kristianslund Eirik Klami , Krosshaug Tron
Published: April 2015

Knee valgus angles measured in sidestep cutting and vertical drop jumps are key variables in research on anterior cruciate ligament (ACL) injury causation. These variables are also used to quantify knee neuromuscular control and ACL injury risk. The aims of the current study were to (1) quantify the differences in the calculated knee valgus angles between 6 different thigh marker clusters, (2) investigate the trial ranking based on their knee valgus angles, and (3) investigate the influence of marker clusters on the cross-talk effect. Elite female handball and football players (n = 41) performed sidestep cutting and vertical drop jumping motions. We found systematic differences up to almost 15° of peak valgus between the marker sets in the drop jump test. The Spearman’s rank correlation coefficient varied from .505 to .974 among the 6 marker sets. In addition, the cross-talk effect varied considerably between the marker clusters. The results of the current study indicate that the choice of thigh marker cluster can have a substantial impact on the magnitude of knee valgus angle, as well as the trial ranking. A standardized thigh marker cluster, including nonanatomical landmark, is needed to minimize the variation of the measurement.
Sex Differences During an Overhead Squat Assessment
Authors: Mauntel Timothy C. , Post Eric G. , Padua Darin A. , Bell David R.
Published: April 2015

A disparity exists between the rates of male and female lower extremity injuries. One factor that may contribute to this disparity is high-risk biomechanical patterns that are commonly displayed by females. It is unknown what biomechanical differences exist between males and females during an overhead squat. This study compared lower extremity biomechanics during an overhead squat and ranges of motion between males and females. An electromagnetic motion tracking system interfaced with a force platform was used to quantify peak lower extremity kinematics and kinetics during the descent phase of each squat. Range of motion measurements were assessed with a standard goniometer. Differences between male and female kinematics, kinetics, and ranges of motion were identified with t tests. Males displayed greater peak knee valgus angle, peak hip flexion angle, peak vertical ground reaction forces, and peak hip extension moments. Males also displayed less active ankle dorsiflexion with the knee extended and hip internal and external rotation than females. No other differences were observed. The biomechanical differences between males and females during the overhead squat may result from differences in lower extremity ranges of motion. Therefore, sex-specific injury prevention programs should be developed to improve biomechanics and ranges of motion.
Key Factors Influencing Implementation of Falls Prevention Exercise Programs in the Community
Authors: Day Lesley , Trotter Margaret J. , Donaldson Alex , Hill Keith D. , Finch Caroline F.
Published: April 2015

The study aim was to evaluate the implementation of group- and home-based exercise falls prevention programs delivered through community health agencies to community-dwelling older people. Interviews with program staff were guided by the Diffusion of Innovations theory. Highly consistent themes emerged for the two types of programs. Both had high overall compatibility, high relative advantage, good observability and high inherent trialability—all factors known to strengthen implementation. The level of complexity and low financial compatibility emerged as the strongest potential inhibitors to program implementation in the context examined. The two main factors contributing to complexity were the need to challenge balance safely across a broad range of capability, and practical considerations associated with program delivery.A range of strategies to provide more technical support for exercise program leaders to tailor balance challenge for exercise program leaders may enhance implementation of falls prevention exercise programs.
Large thermal Hall conductivity of neutral spin excitations in a frustrated quantum magnet
Authors: Hirschberger Max , Krizan Jason W. , Cava R. J. , Ong N. P.
Published: April 2015

Probing the nature of an exotic magnet

To minimize their energy, materials with magnetic interactions tend to become ordered at low temperatures. However, if the magnetism is frustrated (for example, if the geometry of the crystal lattice gets in the way of minimizing the energy), the material may not reach an ordered state even at very low temperatures. Hirschberger
et al.
studied the excitations of such a system—the pyrochlore compound Tb
2
Ti
2
O
7
—using thermal transport measurements. Thermal conductivity at very low temperatures resembled that of a disordered metal; a puzzling finding in an electrically insulating transparent material.

Science
, this issue p.
106
Restricted epigenetic inheritance of H3K9 methylation
Authors: Audergon Pauline N. C. B. , Catania Sandra , Kagansky Alexander , Tong Pin , Shukla Manu , Pidoux Alison L. , Allshire Robin C.
Published: April 2015

Inheritance of a covalent histone modification

Genomic DNA is the repository of all genetic information and is packaged into chromatin. Chromatin is also a repository of regulatory information in the form of covalent marks added to the histones that package the DNA. These marks can determine tissue- and organ-specific gene expression patterns, which must be transmitted to daughter cells to maintain their identity. Ragunathan
et al.
and Audergon
et al.
show that in fission yeast, a chromatin mark, like genetic information, can be inherited across many cell generations. The mark can be inherited independently of DNA sequence, DNA methylation, or RNA interference. Thus, histone marks constitute true epigenetic information.

Science
, this issue
10.1126/science.1258699
; see also p.
132
Production of trilobite Rydberg molecule dimers with kilo-Debye permanent electric dipole moments
Authors: Booth D. , Rittenhouse S. T. , Yang J. , Sadeghpour H. R. , Shaffer J. P.
Published: April 2015

Making a molecular fossil lookalike

Atoms are generally compact objects. However, if one of the electrons orbiting the nucleus is given an extra boost of energy so that it's barely still attached, you get a much larger Rydberg atom. Booth
et al.
created an even more exotic species: a giant molecule consisting of a regular cesium atom bound within a Rydberg atom of the same element. The molecules are named “trilobites” because their electronic density visually resembles fossils of these extinct marine creatures.

Science
, this issue p.
99
A child-killing toxin emerges from shadows
Authors: Pulla Priyanka
Published: April 2015

Scientists link mystery deaths in India to consumption of lychees.
‘The Blob’ invades Pacific, flummoxing climate experts
Authors: Kintisch Eli
Published: April 2015

Persistent mass of warm water is reshuffling ocean currents, marine ecosystems, and inland weather.
Hoax-detecting software spots fake papers
Authors: Bohannon John
Published: April 2015

Springer jumps into sham submissions arms race.
As Ebola wanes, trials jockey for patients
Authors: Kupferschmidt Kai
Published: April 2015

Researchers debate ending some trials to allow others to go forward.
Deepwater Horizon
: After the oil
Authors: Cornwall Warren
Published: April 2015

Five years on, the world's largest accidental marine spill has left subtle scars on the Gulf of Mexico.
The structure of the human mitochondrial ribosome
Authors: Amunts Alexey , Brown Alan , Toots Jaan , Scheres Sjors H. W. , Ramakrishnan V.
Published: April 2015

The whole mitoribosome at high resolution

Mitochondria are thought to be the descendents of a prokaryotic cell that took up residence in a protoeukaryotic cell. Mitochondria retain a few genes involved in oxidative phosphorylation. To translate these genes, mitochondria contain highly divergent mitochondrial ribosomes, or mitoribosomes. Amunts
et al.
determined the high-resolution structures of complete mammalian mitoribosomes using cryoelectron microscopy. Mitoribosomes include an unusual mRNA binding channel. The findings elucidate how aminoglycoside antibiotics can inadvertently inhibit mitoribosomes and how mutations in mitoribosomes can lead to disease.

Science
, this issue p.
95
MicroRNA control of protein expression noise
Authors: Schmiedel Jörn M. , Klemm Sandy L. , Zheng Yannan , Sahay Apratim , Blüthgen Nils , Marks Debora S. , van Oudenaarden Alexander
Published: April 2015

Expressing variability under miRNA control

MicroRNAs (miRNAs) repress gene expression by inhibiting translation and increasing mRNA degradation. Schmiedel
et al.
used single-cell reporter experiments and mathematical modeling to show that miRNAs can reduce not just expression but the expression variability of target genes (see the Perspective by Hoffman and Pilpel). Combinatorial targeting principles ensured reduced variability for most miRNA gene targets. Thus, miRNAs may provide safeguards for the precision of gene expression during development or cellular homeostasis.

Science
, this issue p.
128
; see also p.
41
Observing the unexpected enhances infants’ learning and exploration
Authors: Stahl Aimee E. , Feigenson Lisa
Published: April 2015

Learning when and what to learn

Infants use “unexpectedness” as a cue for learning. Stahl and Feigenson studied how babies reacted when objects behaved in surprising ways (see the Perspective by Schulz). Babies who saw apparently solid and weighty objects moving through a wall or past the edge of a table without falling looked intently at them. When given the opportunity to explore these peculiar objects, they did so by banging them on the floor—as if to test their solidity—or dropping them—as if to test their weightiness.

Science
, this issue p.
91
; see also p.
42
Dense dislocation arrays embedded in grain boundaries for high-performance bulk thermoelectrics
Authors: Kim Sang Il , Lee Kyu Hyoung , Mun Hyeon A , Kim Hyun Sik , Hwang Sung Woo , Roh Jong Wook , Yang Dae Jin , Shin Weon Ho , Li Xiang Shu , Lee Young Hee , Snyder G. Jeffrey , Kim Sung Wng
Published: April 2015

Squeezing out efficient thermoelectrics

Thermoelectric materials hold the promise of converting waste heat into electricity. The challenge is to develop high-efficiency materials that are not too expensive. Kim
et al.
suggest a pathway for developing inexpensive thermoelectrics. They show a dramatic improvement of efficiency in bismuth telluride samples by quickly squeezing out excess liquid during compaction. This method introduces grain boundary dislocations in a way that avoids degrading electrical conductivity, which makes a better thermoelectric material. With the potential for scale-up and application to cheaper materials, this discovery presents an attractive path forward for thermoelectrics.

Science
, this issue p.
109
Cancer and the microbiota
Authors: Garrett Wendy S.
Published: April 2015

A host’s microbiota may increase, diminish, or have no effect at all on cancer susceptibility. Assigning causal roles in cancer to specific microbes and microbiotas, unraveling host-microbiota interactions with environmental factors in carcinogenesis, and exploiting such knowledge for cancer diagnosis and treatment are areas of intensive interest. This Review considers how microbes and the microbiota may amplify or mitigate carcinogenesis, responsiveness to cancer therapeutics, and cancer-associated complications.
Evidence for Human Norovirus Infection of Dogs in the United Kingdom
Authors: Caddy Sarah L. , de Rougemont Alexis , Emmott Edward , El-Attar Laila , Mitchell Judy A. , Hollinshead Michael , Belliot Gael , Brownlie Joe , Le Pendu Jacques , Goodfellow Ian
Published: April 2015

Human noroviruses (HuNoVs) are a major cause of viral gastroenteritis, with an estimated 3 million cases per year in the United Kingdom. HuNoVs have recently been isolated from pet dogs in Europe (M. Summa, C.-H. von Bonsdorff, and L. Maunula, J Clin Virol 53:244–247, 2012,
http://dx.doi.org/10.1016/j.jcv.2011.12.014
), raising concerns about potential zoonotic infections. With 31% of United Kingdom households owning a dog, this could prove to be an important transmission route. To examine this risk, canine tissues were studied for their ability to bind to HuNoV
in vitro
. In addition, canine stool samples were analyzed for the presence of viral nucleic acid, and canine serum samples were tested for the presence of anti-HuNoV antibodies. The results showed that seven different genotypes of HuNoV virus-like particles (VLPs) can bind to canine gastrointestinal tissue, suggesting that infection is at least theoretically possible. Although HuNoV RNA was not identified in stool samples from 248 dogs, serological evidence of previous exposure to HuNoV was obtained in 43/325 canine serum samples. Remarkably, canine seroprevalence for different HuNoV genotypes mirrored the seroprevalence in the human population. Though entry and replication within cells have not been demonstrated, the canine serological data indicate that dogs produce an immune response to HuNoV, implying productive infection. In conclusion, this study reveals zoonotic implications for HuNoV, and to elucidate the significance of this finding, further epidemiological and molecular investigations will be essential.
Equine Herpesvirus 1 Multiply Inserted Transmembrane Protein pUL43 Cooperates with pUL56 in Downregulation of Cell Surface Major Histocompatibility Complex Class I
Authors: Huang Teng , Ma Guanggang , Osterrieder Nikolaus
Published: April 2015

Herpesviruses have evolved an array of strategies to counteract antigen presentation by major histocompatibility complex class I (MHC-I). Previously, we identified pUL56 of equine herpesvirus 1 (EHV-1) as one major determinant of the downregulation of cell surface MHC-I (G. Ma, S. Feineis, N. Osterrieder, and G. R. Van de Walle, J. Virol. 86:3554–3563, 2012,
http://dx.doi.org/10.1128/JVI.06994-11
; T. Huang, M. J. Lehmann, A. Said, G. Ma, and N. Osterrieder, J. Virol. 88:12802–12815, 2014,
http://dx.doi.org/10.1128/JVI.02079-14
). Since pUL56 was able to exert its function only in the context of virus infection, we hypothesized that pUL56 cooperates with another viral protein. Here, we generated and screened a series of EHV-1 single-gene deletion mutants and found that the pUL43 orthologue was required for downregulation of cell surface MHC-I expression at the same time of infection as when pUL56 exerts its function. We demonstrate that the absence of pUL43 was not deleterious to virus growth and that expression of pUL43 was detectable from 2 h postinfection (p.i.) but decreased after 8 h p.i. due to lysosomal degradation. pUL43 localized within Golgi vesicles and required a unique hydrophilic N-terminal domain to function properly. Finally, coexpression of pUL43 and pUL56 in transfected cells reduced the cell surface expression of MHC-I. This process was dependent on PPxY motifs present in pUL56, suggesting that late domains are required for pUL43- and pUL56-dependent sorting of MHC class I for lysosomal degradation.

IMPORTANCE
We describe here that the poorly characterized herpesviral protein pUL43 is involved in downregulation of cell surface MHC-I. pUL43 is an early protein and degraded in lysosomes. pUL43 resides in the Golgi vesicles and needs an intact N terminus to induce MHC-I downregulation in infected cells. Importantly, pUL43 and pUL56 cooperate to reduce MHC-I expression on the surface of transfected cells. Our results suggest a model for MHC-I downregulation in which late domains in pUL56 are required for the rerouting of vesicles containing MHC-I, pUL56, and pUL43 to the lysosomal compartment.