bluuebunny/crossref_metadata_2025 huggingface dataset:
Unsteady Flow Calculation in a Vibrating Cascade and Aerodynamic Damping Prediction
Authors: Garreau D. , Tephany F.
Published: April 2015

A numerical method has been developed for predicting the aerodynamic damping of the last L.P. stages in a 900 MW steam turbine on a blade to blade surface using a boundary element method. The results obtained on the first flexural mode of the blades for several displacements and for several interblade phase angles show no unstability of the rotor except perhaps for low phase angles. They also prove that quasisteady calculations are relevant for all the cases tested.
A Study of a Turbine-Generator System for Low-Head Hydropower
Authors: Mankbadi R. R. , Mikhail S.
Published: April 2015

A method is outlined for determining the optimum operating conditions of a turbine-generator unit installed across a low-head irrigation structure for electrical power generation. For a given regulator’s characteristic, the unit’s rated power and design parameters are determined such that its cost-benefit ratio is minimum. The economical feasibility of the microhydro plant is studied by comparing its life-time cost to its life-time benefit. The benefit is determined by the cost of the corresponding energy generated through a diesel-driven generator set. The microhydro plant was found to be economically feasible over a wide range of inflation and interest rates.
A Real-Time Monitor for Entrained Particle Loading
Authors: Woodruff Steven D. , Anderson Rodney J.
Published: April 2015

The use of coal and coal-derived fuels in combustion gas turbines is being aggressively pursued. Contaminants in these fuels can lead to various detrimental effects to the turbine including increased pressure drops, altered gas flow patterns, and the potential for surging. An instrument has been developed to provide a real-time measure of the loading of particles entrained in the products of combustion of these fuels. The unit is a self-compensating, two color transmissometer which measures the obscuration of a laser beam due to the scattering of light by particles along the path of the beam. The transmissometer consists of, a HeNe laser (632.8 nm) and a HeCd laser (441.6 nm), detectors, and data acquisition/control electronics. Utilizing windows appropriately placed in the products of combustion stream, the transmissometer has a time resolution of about 1 second and a sensitivity of about 0.1 percent.
Review of Factory Aerodynamic Tests for Verification of Centrifugal Gas Compressor Field Performance Prediction
Authors: Sapiro Leon
Published: April 2015

Centrifugal gas compressors are generally tested in the manufacturing facility, before delivery, to determine the accuracy of the aerodynamic performance prediction made for the field operation. One type of test, which some manufacturers apply to every unit, is conducted in an open loop, with ambient air. The other more elaborate type, which is the result of mutual agreement between manufacturer and user, is conducted in a closed loop in accordance with the ASME Power Test Code No. 10, Class II or III, using inert gases at conditions similar to the ones expected in the field.

This paper discusses the justification and the different approach of each type of test to prove performance prediction, and the limitations which they encounter in practice. Topics include testing procedures used for simulating the field conditions on low- and high-molecular weight hydrocarbon applications, limitations due to the selected inert gas and to the maximum admissible values of rotational speed and temperature, the effect of different stage matching at other-than-field gas, and the approach to redefine the surge point position on test to account for the different compressor sensitivity to piping-induced surge when operating in the field.
Time-Split Inflow Boundary Treatment
Authors: Tong Siu Shing
Published: April 2015

This paper describes a new non-reflective inflow treatment for viscous and inviscid internal flow calculations. The method approximates the multi-dimensional governing equations at the inflow boundary in a series of one-dimensional split equations. This treatment allows the artificial inflow boundary to be brought in just in front of the leading edge, while allowing upstream running waves to penetrate without significant reflection. Calculation examples of two dimensional inviscid internal flows are presented. Extension of the method to three-dimensional problems is also discussed.
Indirect Firing of Gas Turbines by Residual Coal-Water Fuel
Authors: Green Leon
Published: April 2015

Production of low-ash, low-sulfur coal-water fuel (CWF) will yield large quantities of high-ash but still low-sulfur “residual” CWF analogous to the residual fuel oil produced by petroleum refining. Relatively low in cost compared to the premium, low-ash CWF product, “resid” CWF will thus be available for in-plant industrial generation of conventional steam power or process heat. Due to its low sulfur content, however, a higher-value use of such a compliance fuel can be the indirect firing of gas turbines for the more efficient combination of power generation plus subsequent bottoming-cycle use or process heat applications (cogeneration).

To limit NOx emissions, staged combustion will be required. Such operation can be accomplished starting with substoichiometric CWF reaction in “conventional” slurry burners followed by final combustion completed in the bottom region of a deep, intensely-mixed, fludized-bed heat exchanger. By virtue of the highly enhanced heat-transfer characteristics of the strongly-stirred bed of non-reactive particles, the normal limitation of rates of non-pressurized fire-side heat transfer is elevated. The fuel ash particles, milled fine by passage through the bed of refractory heat-transfer particles, are collected in a conventional baghouse. The conceptual design of such a combustion-driven, fluid-bed heat exchanger system fired by high-ash, residual coal-water fuel is outlined and its advantages over a conventional fluid-bed, solid-coal combustor for indirect firing of gas turbines are enumerated.
Investigation of Swirler/Dilution Jet Flow Split on Primary Zone Flow Patterns in a Water Model Can-Type Combustor
Authors: Koutmos P. , McGuirk J. J.
Published: April 2015

LDA measurements of the three mean velocity components and the corresponding turbulence intensities have been made to provide qualitative and quantitative information on the flow field in a water model of a can type gas turbine combustion chamber. The combustor geometry comprised a swirl driven primary zone, annulus fed rows of primary and secondary jets and an exit contraction. The effect of variation of the flow split between the swirler and the dilution holes on the flow pattern in the primary zone has been investigated in detail. Flow visualisation studies revealed that significant changes occur in this region due to the interaction between the swirling flow and the radially directed primary jets. A large toroidal recirculation was formed and high levels of turbulence energy generated in the core of the combustor at low levels of swirler flow rate. As the swirl level increases the strength of this recirculation was observed to weaken and become less stable. Beyond a critical level, the primary recirculation was pushed off centre and the undesirable feature of a forward velocity on the combustor axis in the primary zone was observed. Despite the dramatic changes brought about in the primary zone the flow pattern downstream of the secondary jets was practically the same for all flow splits due to the strong mixing caused by the two rows of jets.
F-14 Re-Engining With the F110 Engine
Authors: Castells O. T. , Strong J. T.
Published: April 2015

The advantages of re-engining the F-14 aircraft with the F110 engine is presented. The areas of improvement and the engine development philosophy are explained. A summary description of the pertinent engine design features of the F110 are presented. The flight test results on inlet/engine compatability, afterburner operation, airplane performance, and maintainability/reliability/durability are interpreted. Finally, a description of the proposed version of the F110 engine for the F-14 is presented.
3-D Design of Turbine Airfoils
Authors: Hourmouziadis J. , Hübner N.
Published: April 2015

With modern turbines operating at a high level of efficiency, sophisticated design techniques are needed for further improvements. With the aid of computers 3-D aspect like end wall contouring and airfoil stacking can be integrated into the design process. The possibilities presented by the latter to control reaction, loading and secondary flow effects are analyzed and compared with experimental results. The implications for the resulting airfoil geometry are shown and limitations are discussed.
Transient Analysis of Gas Turbine Power Plants, Using the Huntorf Compressed Air Storage Plant as an Example
Authors: Schobeiri T. , Haselbacher H.
Published: April 2015

The design of modern gas turbines requires the predetermination of their dynamic behavior during transients of various kinds. This is especially true for air storage and closed cycle gas turbine plants. The present paper is an introduction to a computatational method which permits an accurate simulation of any gas turbine system. Starting with the conservation equations of aero/thermodynamics, the modular computer program COTRAN was developed, which calculates the transient behavior of individual components as well as of entire gas turbine systems. For example, it contains modules for compressors, turbines, combustion chambers, pipes etc. To demonstrate the effectiveness of COTRAN the shut-down tests of the air storage gas turbine plant Huntorf were simulated and results compared with experimental data. The agreement was found to be very good.
The Burning of Coal-Water Slurry Fuels in a Two-Stage Slagging Combustor
Authors: LeCren R. T. , White D. J.
Published: April 2015

A two-stage coal-water slurry high-pressure gas turbine combustion system employing a primary zone with a hot refractory wall and an internal slag removal system has been designed, built and tested. The molten ash is removed by aerodynamic means using a form of jet impaction, a method that promises to be more effective than the more conventional cyclonic approaches. The overall combustion system is extremely flexible and can be readily configured to operate either with a lean or a rich reaction (primary) zone. In both cases a lean secondary zone is used.

Results showing emission signatures of a number of coal-water slurry fuels operating with the combustor arranged in a rich primary zone configuration are presented. Petroleum based fuels show emission trends that are very similar to those previously published. Coal-water slurry combustion, however, results in emission signatures that cover only a relatively narrow fuel-air ratio range because of the limited combustion stability. NOx emissions have been obtained that meet EPA regulations for stationary gas turbines.
Technical Evaluation of Simplified IGCC Components
Authors: Horner M. W. , Alff R. K. , Corman J. C.
Published: April 2015

Simplified integrated gasification combined cycle (IGCC) power plants offer attractive advantages for improving the performance of coal to electricity systems. This plant configuration, which utilizes a coal gasifier, hot gas cleanup system, and gas turbine combined cycle, has the potential to reduce both capital costs for equipment and fuel costs through improved efficiency. This paper reports the results of fuel supply and gas turbine testing on actual hot low-Btu coal gas.

A pilot-scale advanced fixed-bed gasifier has been modified to supply hot coal gas to a particulate removal cyclone and then to a gas turbine simulator. The hot gas is combusted in a General Electric MS6000 combustor developed for low-Btu gas fuel. The combusted product flows through a MS6000 turbine first-stage nozzle sector. The exhaust gases from the nozzle sector pass over air-cooled cylindrical ash deposition pin specimens and then into a water quench exhaust system.

Extensive instrumentation and sampling provisions are utilized to characterize the fuel gas, the combustion gases, and the ash deposits formed on turbine components. Two regimes of nozzle metal surface temperatures have been investigated by separate testing performed including 500–600 °F with water-cooled and 1500–1650 °F with air-cooled nozzle sectors. Results from the test program have provided key data related to fuel gas cleanup and the tolerance of gas turbine hot gas path parts to the products of combustion from coal-derived fuels.
Production and Development of Secondary Flows and Losses Within a Three Dimensional Turbine Stator Cascade
Authors: Yamamoto A. , Yanagi R.
Published: April 2015

Using five-hole pitot tubes, detailed flow measurements were made before, within and after a low-speed three-dimensional turbine stator blade row to obtain quantitative information on the aerodynamic loss mechanism. Qualitative flow visualization tests and endwall static pressure measurements were also made.

An analysis of the tests revealed that many vortical flows promote loss generation. Within a large part of the cascade, a major loss process could be explained simply as the migration of boundary layer low energy fluids from surrounding walls (endwalls and blade surfaces) to the blade suction surface near the trailing edge. On the other hand, complexity exists after the cascade and in the vortical flows near the trailing edge. The strong trailing shedding vortices affect upstream flow fields within the cascade. Detailed flow surveys within the cascade under the effects of blade tip leakage flows are also included.
A Method to Measure the Fuel Distribution and the Fuel Captured by V–Gutter Flameholder in High Speed Airstream
Authors: Shan-Jian Gu , Mao-Lin Yang , Xiang-Yi Li
Published: April 2015

A method to measure the fuel distribution and the percentage of fuel flow rate captured by a V-gutter flameholder in a high speed airstream has been developed. The effects of configuration and size of the probe and temprature of the sample mixture in the probe on measurement have been investigated. The detailed determination of isokinetic sampling condition is described. The effects of V-gutter geometry on flowfield have been considered. The total experimental error is of the order ±5%.
An Experimental Study of the Mixing by an Acoustically Pulsed Axisymmetrical Air-Jet
Authors: Vermeulen P. J. , Yu Wai Keung
Published: April 2015

The mixing by an acoustically pulsed axisymmetrical air-jet, flowing into the atmosphere, has been studied by means of velocity and temperature profile measurements. The strength of the velocity pulsation imparted to the jet flow and of the associated toroidal vortices were also measured. The entrainment rate was increased by up to two times, with the majority of the extra entrainment occurring over the first five diameters downstream of the jet orifice, where toroidal vortices are formed and attain their greatest strength. The jet response depends on Strouhal number and appears to be optimum at about 0.25. The response starts to saturate at the limit of pulsation strength used.
The Control of NOx and CO Emissions From 7-MW Gas Turbines With Water Injection as Influenced by Ambient Conditions
Authors: Hung W. S. Y. , Agan D. D.
Published: April 2015

Interpretation of federal emissions regulations by a local regulatory agency resulted in the requirement to develop a special water control system for stationary gas turbines to meet stringent NOx and CO emissions limits. Extensive field testing of two 7-MW industrial gas turbines burning natural gas was performed to establish the effects of ambient air temperature, humidity and water injection on NOx and CO emissions. The predictions from a proven NOx model were shown to be within the uncertainty of the field measurements and were used to determine the water flow rates required when burning No. 2 distillate oil. Over the ambient temperature range considered, the analytical model predicted a linear increase in NOx emissions as ambient temperature increases. This was supported by the data gathered and the thermal NOx rate equation. Subsequently, a water injection system was successfully developed to control NOx and CO emissions from the 7-MW dual fuel gas turbine as a function of ambient temperature and turbine load.
Inverse Design Calculations for Transonic Cascades
Authors: Zhengming Wang
Published: April 2015

The computation methods of the inverse problem and several mixed aerodynamic problems for transonic cascades are presented. The calculations are completed directly on the physical plane by the stream function equation. The corresponding boundary conditions of these problems are transfered into the boundary conditions expressed by stream function with the help of the relations of the basic equations. The methods presented have a clear physical concept and use similar manners of iteration for different problems. The calculations of some examples for the transonic inverse problem indicate this method is very effective. An example is given of a shockless supercritical cascade designed successfuly by the transonic inverse code.
Simulation of Subsonic Flow Through a Generic Labyrinth Seal Cavity
Authors: Rhode D. L. , Sobolik S. R.
Published: April 2015

A finite difference computer program has been developed to predict the subsonic compressible flow within a single cavity of a concentric-rotor labyrinth seal. The recent QUICK convective differencing scheme is employed to eliminate false diffusion. Previously unavailable distributions of important flow variables throughout a generic seal cavity are presented. Specifically, the dimensionless results of four seal leakage mass flow rates at given cavity inlet pressure and temperature have been compared and important variations are examined. Also, realistic approximations of flow variable distributions within a labyrinth seal cavity are made from the included figures.
Centrifugal Process Compressors: Radial vs. Tangential Suction Nozzles
Authors: Lüdtke Klaus
Published: April 2015

Experimental investigations were conducted on a radial and a tangential inlet duct to an industrial centrifugal compressor. The tangential nozzle will replace the conventional radial nozzle if a block foundation is used with no pipes allowed on the upper casing half. Models were air tested with and without suction elbows. The tangential duct was tested with various positions of the shaped flow splitter and with variable intake rib angles with the objective to minimize distortions of axial and circumferential velocity profiles and the moment of momentum in the annular eye opening of the impeller. An optimum configuration for the tangential duct was found with smooth profiles and eliminated global vortex at the exit annulus.
Preliminary Results of a Study of the Relationship Between Free Stream Turbulence and Stagnation Region Heat Transfer
Authors: VanFossen G. James , Simoneau Robert J.
Published: April 2015

A study is being conducted at the NASA Lewis Research Center to investigate the mechanism that causes free stream turbulence to increase heat transfer in the stagnation region of turbine vanes and blades. The work is being conducted in a wind tunnel at atmospheric conditions to facilitate measurements of turbulence and heat transfer. The model size is scaled up to simulate Reynolds numbers (based on leading edge diameter) that are to be expected on a turbine blade leading edge. Reynolds numbers from 13 000 to 177 000 were run in the present tests.

Spanwise averaged heat transfer measurements with high and low turbulence have been made with “rough” and smooth surface stagnation regions. Results of these measurements show that the boundary layer remains laminar in character even in the presence of free stream turbulence at the Reynolds numbers tested. If roughness is added the boundary layer becomes transitional as evidenced by the heat transfer increase with increasing distance from the stagnation line.

Hot wire measurements near the stagnation region downstream of an array of parallel wires has shown that vorticity in the form of mean velocity gradients is amplified as flow approaches the stagnation region. Circumferential traverses of a hot wire probe very near the surface of the cylinder have shown the fluctuating component of velocity changes in character depending on free stream turbulence and Reynolds number.

Finally smoke wire flow visualization and liquid crystal surface heat transfer visualization have been combined to show that, in the wake of an array of parallel wires, heat transfer is a minimum in the wire wakes where the fluctuating component of velocity (local turbulence) was the highest. Heat transfer was found to be the highest between pairs of vortices where the induced velocity is toward the cylinder surface.
Surface Degradation of Ductile Metal in Elevated Temperature Gas-Particle Streams
Authors: Levy Alan , Man Yong-Fa
Published: April 2015

The mechanisms and rates of erosion and combined erosion-corrosion of 9CrlMo steel and 310SS at elevated temperatures were investigated to better understand the behavior of piping steels in fluidized bed combustor environments. Tests were performed in a partially inert gas atmosphere to study erosion behavior and in an air atmosphere to study combined erosion-corrosion behavior. It was determined that the erosion rate remained constant or decreased with temperature in nitrogen until a temperature was reached at which the tensile strength v.s. temperature curve of the alloy markedly changed its negative slope. Above this temperature the erosion rate increased rapidly with temperature.

In an erosion-corrosion environment corrosion was the dominant mechanism at all test conditions. At higher temperatures and velocities the material loss mechanism changed from low loss rate chipping of the scale to high loss rate periodic spalling. The continuous scale formed on 9CrlMo steel in air appeared to protect the metal surface, decreasing its loss rate in α=30° tests compared to that of 310SS tested at the same conditions in nitrogen where a continuous scale did not form.
Erosion Testing of High Temperature Corrosion Protection Coatings
Authors: Toriz F. C. , Wolverson J. , Gupta Suresh
Published: April 2015

This study was undertaken to test and quantify the erosion protection available from coatings normally used for corrosion protection in the hot section of gas turbine engines. Erosion data was obtained for MAR-M002, pack Aluminum, Platinum Aluminum, and several overlay MCrAlY coatings for target temperatures between 850° and 1080°C (1500–2000°F). Particle velocities were around 305m/sec (1000 ft/sec) and impingement angles were between 30°-90°. Quartz and fly ash particles were used. The data indicates a significant life improvement by the use of these coatings, which in turn is proportional to the coating thickness.
A Study Concerning Performance Characteristics of Centrifugal Compressors
Authors: Mizuki Shimpei , Imai Hikaru
Published: April 2015

A method for estimations of performance characteristics of centrifugal compressors was examined by comparing the estimated results with those by experiments. Lots of empirical and semi-empirical factors which were introduced to the losses within compressor channels in the estimations, and the experimental results for the compressors with a wide variety of configurations, operating conditions and design techniques were investigated. After the extensive comparisons, the most appropriate combinations of the factors for the present method were given.

By employing this method, the major factors which are directly related to the performance characteristics were computed and the relationships among them were discussed. Thus, the ratio of the relative velocity at the impeller exit to that at the inlet, the non-dimensional relative velocity at the impeller inlet and that at the exit were obtained as the parameters of the slip factor, the flow coefficient and the specific speed.
Improved performance of GaN-based light emitting diodes with nanopatterned sapphire substrates fabricated by wet chemical etching
Authors: Geng Chong , Yan Qingfeng , Dong Peng , Shan Liang , Du Chengxiao , Wei Tongbo , Hao Zhibiao
Published: April 2015

The authors present a facile approach to the fabrication of nanopatterned sapphire substrates (NPSS) with concave pyramid structure by a wet etching method. The silica wet-etching mask on the sapphire substrate was prepared by using a colloidal monolayer templating strategy. NPSS with two different periods were prepared by employing 660 and 900 nm polystyrene colloidal spheres. Light emitting diode (LED) structure was epitaxially grown on the NPSS by the metal-organic chemical vapor deposition method. Both structural and optoelectronic properties of LEDs grown on flat sapphire substrate and NPSS were demonstrated and compared in detail. The calculations based on x-ray rocking curves revealed that the threading dislocation densities (TDDs) were decreased and the crystalline quality of epitaxial GaN film was improved when NPSS was used. Furthermore, the decrease in the edge TDDs was more prominent than that in the screw TDDs, which could be explained by the dislocation annihilation mechanism. The LEDs grown on 660- and 900-nm-NPSS exhibited 48% and 56% enhancement in light output power compared to that of a conventional LED on a flat sapphire substrate, arising from the nanoscale patterns in the sapphire which allowed more light to reflect from sapphire substrate onto the top direction.
Theoretical investigation of the design and performance of a dual energy (kV and MV) radiotherapy imager
Authors: Liu Langechuan , Antonuk Larry E. , El‐Mohri Youcef , Zhao Qihua , Jiang Hao
Published: April 2015

Purpose:

In modern radiotherapy treatment rooms, megavoltage (MV) portal imaging and kilovoltage (kV) cone‐beam CT (CBCT) imaging are performed using various active matrix flat‐panel imager (AMFPI) designs. To expand the clinical utility of MV and kV imaging, MV AMFPIs incorporating thick, segmented scintillators and, separately, kV imaging using a beam's eye view geometry have been investigated by a number of groups. Motivated by these previous studies, it is of interest to explore to what extent it is possible to preserve the benefits of kV and MV imaging using a single AMFPI design, given the considerably different x ray energy spectra used for kV and MV imaging. In this paper, considerations for the design of such a dual energy imager are explored through examination of the performance of a variety of hypothetical AMFPIs based on x ray converters employing segmented scintillators.

Methods:

Contrast, noise, and contrast‐to‐noise ratio performances were characterized through simulation modeling of CBCT imaging, while modulation transfer function, Swank factor, and signal performance were characterized through simulation modeling of planar imaging. The simulations were based on a previously reported hybrid modeling technique (accounting for both radiation and optical effects), augmented through modeling of electronic additive noise. All designs employed BGO scintillator material with thicknesses ranging from 0.25 to 4 cm and element‐to‐element pitches ranging from 0.508 to 1.016 mm. A series of studies were performed under both kV and MV imaging conditions to determine the most advantageous imager configuration (involving front or rear x ray illumination and use of a mirror or black reflector), converter design (pitch and thickness), and operating mode (pitch‐binning combination).

Results:

Under the assumptions of the present study, the most advantageous imager design was found to employ rear illumination of the converter in combination with a black reflector, incorporate a BGO converter with a 0.508 mm pitch and a 2 cm thickness, and operate at full resolution for kV imaging and 2 × 2 binning mode for MV imaging. Such a dual energy imager design should provide soft tissue visualization at low, clinically practical doses under MV conditions, while helping to preserve the high spatial resolution and high contrast offered by kV imaging.

Conclusions:

The authors’ theoretical investigation suggests that a dual energy imager capable of largely preserving the desirable characteristics of both kV and MV imaging is feasible. Such an imager, when coupled to a dual energy radiation source, could facilitate simplification of current treatment room imaging systems (as well as their associated quality assurance), and facilitate more precise integration of kV and MV imaging information by virtue of reduced geometric uncertainties.
Sitting Time, Physical Activity, and Cardiorespiratory Fitness: Cooper Center Longitudinal Study Cohort
Authors: Barlow Carolyn E. , Shuval Kerem , Balasubramanian Bijal A. , Kendzor Darla E. , Gabriel Kelley Pettee
Published: April 2015

Background:

Prolonged sitting time is associated with numerous health outcomes; however, the role of cardiorespiratory fitness (CRF) in these relationships is largely unexplored. The cross-sectional association between reported sitting time and measured CRF was examined in a large study of healthy men and women.

Methods:

The analytic sample included 4658 men and 1737 women enrolled in the Cooper Center Longitudinal Study. Unadjusted and adjusted multivariable linear regression models were constructed to examine the association between sitting time and CRF, stratified by sex and meeting (or not) meeting physical activity (PA) guidelines.

Results:

In men, CRF was not associated with sitting time after adjustment for potential confounders. In contrast, for women, after adjustment there was a significant association between increased sitting time and lower CRF (P for trend <.001). When stratified by meeting or not meeting PA guidelines, there was no association between sitting time and CRF in men. In women, this relationship was statistically significant regardless of PA category (both P for trend < .05).

Conclusions:

These results suggest that the association between sitting time and CRF varies by sex. Further, meeting PA guidelines does not appear to modify this relation in either sex.
Structural Equation Modeling Supports a Moderating Role of Personality in the Relationship Between Physical Activity and Mental Health in College Women
Authors: Wilson Kathryn E. , Das Bhibha M. , Evans Ellen M. , Dishman Rodney K.
Published: April 2015

Background:

A positive association between physical activity and mental health is well established, particularly for lower symptoms of depression and anxiety among active adults. However, it is unclear whether the association is influenced by personality, which might moderate or otherwise explain the association. In addition, past studies have not confirmed the association using an objective measure of physical activity.

Objective:

Our objective was to examine whether Extraversion and Neuroticism influence the association between mental health and physical activity measured by convergent self-reports and an accelerometer.

Methods:

Structural equation modeling was used to test competing models of the relationships between personality, physical activity, and mental health in a sample of female undergraduates.

Results:

In bivariate analysis, mental health was negatively related to Neuroticism and positively related to Extraversion, self-reported physical activity (which was related only to Extraversion, positively), and objective physical activity (which was related only to Neuroticism, negatively). In structural equation modeling, a 3-way interaction indicated that objective physical activity and mental health were unrelated in extraverts, but related positively in neurotic-introverts and negatively in stable-introverts.

Conclusions:

Higher levels of physical activity were associated with better mental health only in neurotic-introverts, who are at higher risk for mental health problems.
Impact of Policies on Physical Activity and Screen Time Practices in 50 Child-Care Centers in North Carolina
Authors: Erinosho Temitope , Hales Derek , Vaughn Amber , Mazzucca Stephanie , Ward Dianne S.
Published: April 2015

Background:

This study assessed physical activity and screen time policies in child-care centers and their associations with physical activity and screen time practices and preschool children’s (3–5 years old) physical activity.

Methods:

Data were from 50 child-care centers in North Carolina. Center directors reported on the presence/absence of written policies. Trained research assistants observed physical activity and screen time practices in at least 1 preschool classroom across 3 to 4 days. Children (N = 544) wore accelerometers to provide an objective measure of physical activity.

Results:

Physical activity and screen time policies varied across centers. Observational data showed 82.7 min/d of active play opportunities were provided to children. Screen time provided did not exceed 30 min/d/child at 98% of centers. Accelerometer data showed children spent 38 min/d in moderate-to-vigorous physical activity and 206 min/d in sedentary activity. Policies about staff supervision of media use were negatively associated with screen time (P < .05). Contrary to expectation, policies about physical activity were associated with less time in physical activity.

Conclusions:

Clear strategies are needed for translating physical activity policies to practice. Further research is needed to evaluate the quality of physical activity policies, their impact on practice, and ease of operationalization.
T lymphocyte regulation by mevalonate metabolism
Authors: Thurnher Martin , Gruenbacher Georg
Published: April 2015

Metabolites of the mevalonate pathway provide energy, modify critical molecules, and even act as agonists for T cells.
Science Signaling
Podcast: 31 March 2015
Authors: Parsons Ramon , Mense Sarah M. , VanHook Annalisa M.
Published: April 2015

Mutations in
PREX2
overcome tumor suppression by PTEN.
Endocannabinoids inhibit Hedgehog signaling
Authors: Ferrarelli Leslie K.
Published: April 2015

Neuromodulatory lipids called endocannabinoids are natural antagonists of the Hedgehog pathway protein Smoothened.
A transcription factor Sox it to bacterial DNA
Authors: Foley John F.
Published: April 2015

The transcription factor Sox2 acts as a pattern recognition receptor for cytosolic bacterial DNA in neutrophils.
G-CSF mobilizes CD34
+
regulatory monocytes that inhibit graft-versus-host disease
Authors: D’Aveni Maud , Rossignol Julien , Coman Tereza , Sivakumaran Shivajanani , Henderson Stephen , Manzo Teresa , Santos e Sousa Pedro , Bruneau Julie , Fouquet Guillemette , Zavala Flora , Alegria-Prévot Olinda , Garfa-Traoré Meriem , Suarez Felipe , Trebeden-Nègre Hélène , Mohty Mohamad , Bennett Clare L. , Chakraverty Ronjon , Hermine Olivier , Rubio Marie-Thérèse
Published: April 2015

G-SCF–mobilized CD34
+
monocytes inhibit graft-versus-host disease by the production of nitric oxide and the induction of regulatory T cells.
An EphB-Abl signaling pathway is associated with intestinal tumor initiation and growth
Authors: Kundu Parag , Genander Maria , Strååt Klas , Classon Johanna , Ridgway Rachel A. , Tan Ee Hong , Björk Jan , Martling Anna , van Es Johan , Sansom Owen J. , Clevers Hans , Pettersson Sven , Frisén Jonas
Published: April 2015

The cAbl kinase inhibitor imatinib reduces intestinal tumor initiation and growth.
Developing vaccines for an aging population
Authors: Black Steven , De Gregorio Ennio , Rappuoli Rino
Published: April 2015

The next steps in vaccine development include improving vaccine efficiency and fully leveraging new vaccines.
Single-cell genotyping demonstrates complex clonal diversity in acute myeloid leukemia
Authors: Paguirigan Amy L. , Smith Jordan , Meshinchi Soheil , Carroll Martin , Maley Carlo , Radich Jerald P.
Published: April 2015

The targeted genotyping of single acute myeloid leukemia cells is technically feasible, identifies the zygosities of concurrent mutations, and suggests that sequencing of bulk populations may underestimate clonal complexity.
Score: N = 1/Tricuspid regurgitation = 0
Authors: Kolandaivelu Kumaran
Published: April 2015

Compassionate use of a percutaneous mitral valve repair technology to treat tricuspid regurgitation yielded the first human transcatheter tricuspid valve repair.
Niche guidance of hematopoietic differentiation
Authors: Lathia Justin D.
Published: April 2015

The generation of hematopoietic progenitor cells from pluripotent stem cells is enhanced by niche cells and factors.
Antibodies complement malaria
Authors: Round June L.
Published: April 2015

Antibodies that recruit complement are important for protection and clearance of malaria parasites, with implications for vaccine development.
Reduced Viral Fitness and Lack of Cross-Class Resistance with Integrase Strand Transfer Inhibitor and Nucleoside Reverse Transcriptase Inhibitor Resistance Mutations
Authors: Andreatta Kristen N. , Goodman Derrick D. , Miller Michael D. , White Kirsten L.
Published: April 2015

The most common pattern of emergent resistance in the phase III clinical trials of coformulated elvitegravir (EVG)-cobicistat (COBI)-emtricitabine (FTC)-tenofovir disoproxil fumarate (TDF) was the EVG resistance substitution E92Q in integrase (IN) with the FTC resistance substitution M184V in reverse transcriptase (RT), with or without the tenofovir (TFV) resistance substitution K65R. In this study, the effect of these IN and RT substitutions alone and in combination in the same genome on susceptibility to antiretroviral inhibitors and viral replication fitness was characterized. Single resistance substitutions (E92Q in IN [IN-E92Q], M184V in RT [RT-M184V], and K65R in RT [RT-K65R]) specifically affected susceptibility to the corresponding inhibitor classes, with no cross-class resistance observed. The IN-E92Q mutant displayed reduced susceptibility to EVG (50-fold), which was not impacted by the addition of RT-M184V or RT-K65R/M184V. Viruses containing RT-M184V had high-level resistance to FTC (>1,000-fold) that was not affected by the addition of IN-E92Q or RT-K65R. During pairwise growth competitions, each substitution contributed to decreased viral fitness, with the RT-K65R/M184V + IN-E92Q triple mutant being the least fit in the absence of drug. In the presence of drug concentrations approaching physiologic levels, however, drug resistance offset the replication defects, resulting in single mutants outcompeting the wild type with one drug present, and double and triple mutants outcompeting single mutants with two drugs present. Taken together, these results suggest that the reduced replication fitness and phenotypic resistance associated with RT and IN resistance substitutions are independent and additive. In the presence of multiple drugs, viral growth is favored for viruses with multiple substitutions, despite the presence of fitness defects.
Encoded Library Technology Screening of Hepatitis C Virus NS4B Yields a Small-Molecule Compound Series with
In Vitro
Replicon Activity
Authors: Arico-Muendel Christopher , Zhu Zhengrong , Dickson Hamilton , Parks Derek , Keicher Jesse , Deng Jianghe , Aquilani Leah , Coppo Frank , Graybill Todd , Lind Kenneth , Peat Andrew , Thomson Michael
Published: April 2015

To identify novel antivirals to the hepatitis C virus (HCV) NS4B protein, we utilized encoded library technology (ELT), which enables purified proteins not amenable to standard biochemical screening methods to be tested against large combinatorial libraries in a short period of time. We tested NS4B against several DNA-encoded combinatorial libraries (DEL) and identified a single DEL feature that was subsequently progressed to off-DNA synthesis. The most active of the initial synthesized compounds had 50% inhibitory concentrations (IC
50
s) of 50 to 130 nM in a NS4B radioligand binding assay and 300 to 500 nM in an HCV replicon assay. Chemical optimization yielded compounds with potencies as low as 20 nM in an HCV genotype 1b replicon assay, 500 nM against genotype 1a, and 5 μM against genotype 2a. Through testing against other genotypes and genotype 2a-1b chimeric replicons and from resistance passage using the genotype 1b replicon, we confirmed that these compounds were acting on the proposed first transmembrane region of NS4B. A single sequence change (F98L) was identified as responsible for resistance, and it was thought to largely explain the relative lack of potency of this series against genotype 2a. Unlike other published series that appear to interact with this region, we did not observe sensitivity to amino acid substitutions at positions 94 and 105. The discovery of this novel compound series highlights ELT as a valuable approach for identifying direct-acting antivirals to nonenzymatic targets.
Prospective Multicenter Study of Carbapenemase-Producing Enterobacteriaceae from 83 Hospitals in Spain Reveals High
In Vitro
Susceptibility to Colistin and Meropenem
Authors: Oteo Jesús , Ortega Adriana , Bartolomé Rosa , Bou Germán , Conejo Carmen , Fernández-Martínez Marta , González-López Juan José , Martínez-García Laura , Martínez-Martínez Luis , Merino María , Miró Elisenda , Mora Marta , Navarro Ferran , Oliver Antonio , Pascual Álvaro , Rodríguez-Baño Jesús , Ruiz-Carrascoso Guillermo , Ruiz-Garbajosa Patricia , Zamorano Laura , Bautista Verónica , Pérez-Vázquez María , Campos José
Published: April 2015

The aim of this study was to determine the impact of carbapenemase-producing
Enterobacteriaceae
(CPE) in Spain in 2013 by describing the prevalence, dissemination, and geographic distribution of CPE clones, and their population structure and antibiotic susceptibility. From February 2013 to May 2013, 83 hospitals (about 40,000 hospital beds) prospectively collected nonduplicate
Enterobacteriaceae
using the screening cutoff recommended by EUCAST. Carbapenemase characterization was performed by phenotypic methods and confirmed by PCR and sequencing. Multilocus sequencing types (MLST) were determined for
Klebsiella pneumoniae
and
Escherichia coli
. A total of 702
Enterobacteriaceae
isolates met the inclusion criteria; 379 (54%) were CPE. OXA-48 (71.5%) and VIM-1 (25.3%) were the most frequent carbapenemases, and
K. pneumoniae
(74.4%),
Enterobacter cloacae
(10.3%), and
E. coli
(8.4%) were the species most affected. Susceptibility to colistin, amikacin, and meropenem was 95.5%, 81.3%, and 74.7%, respectively. The most prevalent sequence types (STs) were ST11 and ST405 for
K. pneumoniae
and ST131 for
E. coli
. Forty-five (54.1%) of the hospitals had at least one CPE case. For
K. pneumoniae
, ST11/OXA-48, ST15/OXA-48, ST405/OXA-48, and ST11/VIM-1 were detected in two or more Spanish provinces. ST11 isolates carried four carbapenemases (VIM-1, OXA-48, KPC-2, and OXA-245), but ST405 isolates carried OXA-48 only. A wide interregional spread of CPE in Spain was observed, mainly due to a few successful clones of OXA-48-producing
K. pneumoniae
(e.g., ST11 and ST405). The dissemination of OXA-48-producing
E. coli
is a new finding of public health concern. According to the susceptibilities determined
in vitro
, most of the CPE (94.5%) had three or more options for antibiotic treatment.
Polymorphic Variation in Susceptibility and Metabolism of Triclosan-Resistant Mutants of Escherichia coli and Klebsiella pneumoniae Clinical Strains Obtained after Exposure to Biocides and Antibiotics
Authors: Curiao Tânia , Marchi Emmanuela , Viti Carlo , Oggioni Marco R. , Baquero Fernando , Martinez José Luis , Coque Teresa M.
Published: April 2015

Exposure to biocides may result in cross-resistance to other antimicrobials. Changes in biocide and antibiotic susceptibilities, metabolism, and fitness costs were studied here in biocide-selected
Escherichia coli
and
Klebsiella pneumoniae
mutants.
E. coli
and
K. pneumoniae
mutants with various degrees of triclosan susceptibility were obtained after exposure to triclosan (TRI), benzalkonium chloride (BKC), chlorhexidine (CHX) or sodium hypochlorite (SHC), and ampicillin or ciprofloxacin. Alterations in antimicrobial susceptibility and metabolism in mutants were tested using Phenotype MicroArrays. The expression of AcrAB pump and global regulators (SoxR, MarA, and RamA) was measured by quantitative reverse transcription-PCR (qRT-PCR), and the central part of the
fabI
gene was sequenced. The fitness costs of resistance were assessed by a comparison of relative growth rates. Triclosan-resistant (TRI
r
) and triclosan-hypersusceptible (TRI
hs
) mutants of
E. coli
and
K. pneumoniae
were obtained after selection with biocides and/or antibiotics.
E. coli
TRI
r
mutants, including those with mutations in the
fabI
gene or in the expression of
acrB
,
acrF
, and
marA
, exhibited changes in susceptibility to TRI, CHX, and antibiotics. TRI
r
mutants for which the TRI MIC was high presented improved metabolism of carboxylic acids, amino acids, and carbohydrates. In TRI
r
mutants, resistance to one antimicrobial provoked hypersusceptibility to another one(s). TRI
r
mutants had fitness costs, particularly
marA
-overexpressing (
E. coli
) or
ramA
-overexpressing (
K. pneumoniae
) mutants. TRI, BKC, and CIP exposure frequently yielded TRI
r
mutants exhibiting alterations in AraC-like global regulators (MarA, SoxR, and RamA), AcrAB-TolC, and/or FabI, and influencing antimicrobial susceptibility, fitness, and metabolism. These various phenotypes suggest a trade-off of different selective processes shaping the evolution toward antibiotic/biocide resistance and influencing other adaptive traits.
Small-Plasmid-Mediated Antibiotic Resistance Is Enhanced by Increases in Plasmid Copy Number and Bacterial Fitness
Authors: San Millan Alvaro , Santos-Lopez Alfonso , Ortega-Huedo Rafael , Bernabe-Balas Cristina , Kennedy Sean P. , Gonzalez-Zorn Bruno
Published: April 2015

Plasmids play a key role in the horizontal spread of antibiotic resistance determinants among bacterial pathogens. When an antibiotic resistance plasmid arrives in a new bacterial host, it produces a fitness cost, causing a competitive disadvantage for the plasmid-bearing bacterium in the absence of antibiotics. On the other hand, in the presence of antibiotics, the plasmid promotes the survival of the clone. The adaptations experienced by plasmid and bacterium in the presence of antibiotics during the first generations of coexistence will be crucial for the progress of the infection and the maintenance of plasmid-mediated resistance once the treatment is over. Here we developed a model system using the human pathogen
Haemophilus influenzae
carrying the small plasmid pB1000 conferring resistance to β-lactam antibiotics to investigate host and plasmid adaptations in the course of a simulated ampicillin therapy. Our results proved that plasmid-bearing clones compensated for the fitness disadvantage during the first 100 generations of plasmid-host adaptation. In addition, ampicillin treatment was associated with an increase in pB1000 copy number. The augmentation in both bacterial fitness and plasmid copy number gave rise to
H. influenzae
populations with higher ampicillin resistance levels. In conclusion, we show here that the modulations in bacterial fitness and plasmid copy number help a plasmid-bearing bacterium to adapt during antibiotic therapy, promoting both the survival of the host and the spread of the plasmid.
Identification of Multiresistance Gene
cfr
in Methicillin-Resistant Staphylococcus aureus from Pigs: Plasmid Location and Integration into a Staphylococcal Cassette Chromosome
mec
Complex
Authors: Li Dexi , Wu Congming , Wang Yang , Fan Run , Schwarz Stefan , Zhang Suxia
Published: April 2015

The multiresistance gene
cfr
was found in 8/231 porcine methicillin-resistant
Staphylococcus aureus
isolates. They were characterized by multilocus sequence typing,
spa
typing,
dru
typing, and staphylococcal cassette chromosome
mec
(SCC
mec
) typing as ST627-t002-dt12w-IVb, ST6-t304-dt12w-IVb, ST9-t899-dt12w-IVb, ST9-t899-dt12ae-IVb, or ST63-t899-dt12v-IVb. Different
cfr
gene regions were detected on plasmids of ca. 35 kb in seven isolates. For the first time, an IS
Enfa4-cfr
-IS
256
fragment was found to be inserted upstream of the
ccr
genes in a chromosomal SCC
mec
IVb element of the remaining isolate.