bluuebunny/crossref_metadata_2025 huggingface dataset:
Zircon U–Pb, Molybdenite Re–Os and K‐feldspar 40Ar/39Ar Dating of the Bolong Porphyry Cu–Au Deposit, Tibet, China
Authors: Zhu Xiangping , Li Guangming , Chen Huaan , Ma Dongfang , Huang Hanxiao
Published: March 2015

The Bolong porphyry Cu–Au deposit is a newly discovered deposit in the central Tibetan Plateau, and is ranked as the second largest copper deposit discovered to date in the Bangong‐Nujiang metallogenic belt in China. Three granodiorite porphyry phases occur within the Bolong porphyry Cu–Au deposit. Phyllic alteration is widespread on the surface of the deposit, and potassic alteration occurs at depth, associated with granodiorite porphyries. The copper and gold mineralization is clearly related to the potassic and phyllic alteration. Multiple chronometers were applied to constrain the timing of magmatic–hydrothermal activity at the Bolong deposit. Zircon U–Pb geochronology reveals that the granodiorite porphyry phases were emplaced at ca. 120 Ma. Re–Os data of four molybdenite samples from quartz–molybednite veinlets yielded an isochron age of 119.4 ± 1.3 Ma. The plateau age of hydrothermal K‐feldspar from the potassic alteration zone, analyzed by 40Ar/39Ar dating, is 118.3 ± 0.6 Ma, with a similar reverse isochron age of 118.5 ± 0.7 Ma. Therefore, the magmatic–hydrothermal activity occurred at ca. 120–118 Ma, which is similar in age to the neighboring Duobuza porphyry copper deposit. The period of 120–118 Ma is therefore important for the development of porphyry Cu–Au mineralization in the central Tibetan Plateau, and these porphyry deposits were formed during the final stages of the northward subduction of the Neo‐Tethys Ocean.
The Nature of Ore‐forming Fluids of the Carlin‐type Gold Deposit in Southwest China: A Case from the Zimudang Gold Deposit
Authors: Liu Yin , Hu Kai , Han Shanchu , Sun Zehang
Published: March 2015

The Zimudang gold deposit is a large Carlin‐type gold deposit in the Southwest Guizhou Province, China, with an average Au content of 6.2 g/t. Gold is mainly hosted in the fault zone and surrounding strata of the F1 fault and Permian Longtan Formation, and the ore bodies are strictly controlled by both the faults and strata. Detailed mineralogy and geochemistry studies are conducted to help judge the nature of ore‐forming fluids. The results indicate that the Au is generally rich in the sulfides of both ores and wall rocks in the deposit, and the arsenian pyrite and arsenopyrite are the main gold‐bearing sulfides. Four subtypes of arsenian pyrite are found in the deposit, including the euhedral and subhedral pyrite, framboidal pyrite, pyrite aggregates and pyrite veins. The euhedral and subhedral pyrite, which can take up about 80% of total pyrite grains, is the dominant type. Au distributed unevenly in the euhedral and subhedral pyrite, and the content of the Au in the rim is relatively higher than in the core. Au in the pyrite veins and pyrite aggregates is lower than the euhedral and subhedral pyrite. No Au has been detected in the points of framboidal pyrites in this study. An obvious highly enriched As rim exists in the X‐ray images of euhedral pyrites, implying the ore‐forming fluids may be rich in As. The relationship between Au and As reveals that the Au may host as a solid solution (Au+) and nanoparticles of native gold (Au0) in the sulfides. The high Co/Ni ratio (>1) of sulfides and the enrichment of W in the ores all reflect that the gold‐bearing minerals and ore‐forming process were mainly related to the hydrothermal fluids, but the magmatic and volcanic activities cannot be neglected. The general existence of Au and As in the sulfides of both ores and wall rocks and the REE results suggest that the ore‐forming fluids may mainly be derived from the basin itself. The enrichment of Tl suggests that the ore‐forming fluids may be enriched in Cl. The Ce and Eu show slightly or apparently negative anomalies, which means the ore fluids were probably formed under reducing environment. The Y/Ho ratios of ore samples fluctuate around 28, implying the bicarbonate complexation and fluorine were both involved in the ore‐forming process. Combined with the previous studies and our results, we infer that the ore‐forming fluids enriched Au, As, HS− and halogen (F, Cl) were derived from the mixture of reducing basinal fluids and magmatic or volcanic hydrothermal fluids.
Valganciclovir versus valacyclovir prophylaxis for prevention of cytomegalovirus: an economic perspective
Authors: Kacer M. , Kielberger L. , Bouda M. , Reischig T.
Published: March 2015

Introduction

Valganciclovir (vGCV) and valacyclovir (vACV) are used in cytomegalovirus (CMV) prophylaxis in renal transplant recipients. The aim of this study was to compare the economic impact of both regimens during 1‐year follow‐up.

Methods

A total of 117 renal transplant recipients at risk for CMV were randomized to 3‐month prophylaxis either with vGCV (900 mg/day, n = 60) or vACV (8 g/day, n = 57) and their data used in a pharmacoeconomic analysis. The pharmacoeconomic evaluation involved all direct CMV‐related expenses in the first year after transplantation. Sensitivity analysis was employed to examine the effects of various prices of antiviral drugs and diagnostic procedures on overall CMV‐related costs. Simulation of the more expensive US healthcare perspective was performed, and a scenario involving costs of acute rejection (AR) was examined.

Results

Overall CMV‐related costs were significantly lower in the vACV arm; median United States dollars (USD) 3473 (3108–3745) vs. USD 5810 (4409–6757; P < 0.001) per patient, respectively. Our data showed that the critical determinant of the major disparity between the prophylactic regimens was the prophylaxis price. Median cost of prophylaxis in the vACV group was USD 1729 (1527–2173) compared to USD 3968 (2683–4857) in the vGCV group (P < 0.001). In sensitivity analysis of the overall CMV‐related costs, the least and the most expensive pharmacotherapy and diagnostic scenarios were used; nevertheless, the vACV arm remained markedly less expensive. Simulation considering the higher physician/nurse and hospitalization fees of the US healthcare system and the scenario including expenditure associated with AR episodes also favored vACV.

Conclusion

VACV prophylaxis for CMV is associated with a significant 44% lower cost than vGCV at the first year after renal transplantation.
Measurements of Secondary Flows and Turbulence in a Turbine Cascade Passage
Authors: Zunino Pietro , Ubaldi Marina , Satta Antonio
Published: March 2015

The results of an experimental investigation on secondary flows in a linear cascade of turbine rotor blades are presented. To gain information on the turbulence related to the secondary flow development in turbine cascades, measurements have been carried out at eight normal sections in the passage and at a plane downstream of the trailing edge, using a constant temperature hot wire anemometer and a total pressure probe.

A high level of turbulent kinetic energy and turbulent shear stresses has been found to be associated with the passage vortex. This result confirms that secondary loss generation in cascades is related to the production of turbulent kinetic energy in the vortex flow and to its viscous dissipation.
Blade Temperature Measurements of Model V84.2 100 MW/60 Hz Gas Turbine
Authors: Schulenberg T. , Bals H.
Published: March 2015

Numerous experimental investigations have been performed with a model V84.2 100 MW / 60 Hz gas turbine up to peak load conditions. The paper presents an overview of the most interesting experiments.

In detail, pyrometric measurements of the first stage turbine blade are described and discussed. Surface temperature distributions are presented in the form of contour plots, and a comparison with theoretical predictions is shown exemplarily. Moreover, the effect of turbulence promoters on the cooling channel side walls is demonstrated.
The Performance Estimation of Transonic Turbine at Design and Off-Design Conditions
Authors: Manchu Ge
Published: March 2015

A performance estimation method has been developed for the transonic turbine. This method can be used for the calculation of gasdynamic parameters of turbines at design and off-design conditions. In this paper a group of simultaneous equations including the S2 stream surface equation, the simplified flow correlation between blade and blade, the loss equations and the deviation angle correlation are solved (Wu, 1950, 1950, 1965; Marsh, 1966; Smith 1973; Novak and Hearsey, 1977.) Solving these equations, the turbine performance can be obtained.

The essential difference in treating the sub-critical, critial and super-critical flow conditions is researched. The correlation between entropy and losses is deduced in this paper. For the choking flow calculation, a unified approach to solve these equations is developed. On the basis of the above research, the false choking condition will not occur and convergence will be reached rapidly with this method.

A computer program was then compiled with this method and has been used for the performance calculation of transonic turbines at design and off-design conditions.

Several examples have been calculated. Satisfactory results are obtained and the reduced flow rate, efficiency and expansion ratio are fairly consistent with the experimental results. The difference between the computational results and experimental data is within 1% near the design condition.
The Refrigerated Gas and Vapor Turbine Cycle
Authors: Anderson J. Hilbert , Laucks F. M.
Published: March 2015

As electrical energy consumption has continued to rise in the United States, and producers of electricity search for power plants requiring less installation time, the gas turbine has emerged as a significant contributor to our nation’s energy needs. Despite a thermal efficiency disadvantage as compared to a conventional steam power plant, it has nevertheless played an increasingly larger role in the production of electrical power. A scheme is here presented whereby the output of a given gas turbine can be increased by more than 60% and its efficiency increased by 30%, thus making it more competitive efficiency-wise with the conventional steam power plant.
New Cycles for Methanol-Fuelled Gas Turbines
Authors: Klaeyle M. M. S. , Laurent R. , Nandjee F.
Published: March 2015

Assuming that methanol is employed as fuel, the heat released from the gas turbine discharges can be used to cause an endothermic catalytic reaction: CH3 OH + H2 O + heat → 0,5 CO + 0,5 CO2 + 2,5 H2 + 0,5 H2 O; this produces a gaseous fuel, the lower heaving value of which exceeds that of methanol by 18%. Combining both steam reforming of methanol and steam injection in the combustor by using the maximum heat available in the exhaust gases, very interesting cycle characteristics can be achieved (more than 50% efficiency (LHV basis), same capital cost per kW as simple cycle gas turbine (9000E engine), low emissions of NOx and SO2). Reheating the gas during the expansion will improve the efficiency by 2–3 points allowing an increase in power output without increasing the capital cost per kW. At the end of the century, these types of cycles could be applied to all the new, non-nuclear power plants in the French energy system. The annual cumulative duration of such generators will not be greater than 2000 hours.
Computation of Full-Coverage Film-Cooled Airfoil Temperatures by Two Methods and Comparison With High Heat Flux Data
Authors: Gladden H. J. , Yeh F. C. , Austin P. J.
Published: March 2015

Two methods were used to calculate the heat flux to full-coverage film cooled airfoils and, subsequently, the airfoil wall temperatures. The calculated wall temperatures were compared to measured temperatures obtained in the Hot Section Facility operating at real engine conditions. Gas temperatures and pressures up to 1900 K and 18 atm with a Reynolds number up to 1.9 million were investigated. Heat flux was calculated by the convective heat transfer coefficient adiabatic wall method and by the superposition method which incorporates the film injection effects in the heat transfer coefficient. The results of the comparison indicate the first method can predict the experimental data reasonably well. However, superposition overpredicted the heat flux to the airfoil without a significant modification of the turbulent Prandtl number. The results of this research suggests that additional research is required to model the physics of full-coverage film cooling where there is significant temperature/density differences between the gas and coolant.
Gas Turbine Exhaust Systems: Design Considerations
Authors: Morris Roy A.
Published: March 2015

The users of Gas Turbine powered equipment are very careful to ensure that they achieve their objectives in terms of power output and overall efficiency, but other important aspects of the system may be underspecified, and cause the user serviceability and maintenance problems during the systems planned operating life.

One important area, crucial to reliable operation of the Gas Turbine, is the power turbine exhaust system. If particular care is not taken on the part of the user in specifying this component, he is likely to be provided with the minimum standard of equipment from the supplier.

This paper highlights some of the areas that should be considered during the preparation of specifications, and in the evaluation of proposals. Specific problems of exhaust design will be addressed to assist the user to identify and question possible problem areas.

The paper concludes that for minimal additional input during the initial stages of a project, long term cost savings could be made and that the overall system would be more reliable.
Performance and Reliability Improvements for Heavy Duty Gas Turbines
Authors: Johnston J. R. (Bob)
Published: March 2015

Many significant advances in technology have been applied to new unit production in the past 15 years. These technology improvements can be applied to field units to achieve increased performance, life, and/or reliability.

Several types of improvement are now available for compressors, combustion systems, hot gas path turbine parts, and turbine controls. This paper provides a summary of performance improvements available for General Electric gas turbines MS3002, MS5001, MS5002, MS6001, MS7001, and MS9001 and tabulations of performance for each improvement. Also provided are detailed descriptions of control modernization designs available for improving the operating reliability of field units.
Laser Anemometry Techniques for Turbine Applications
Authors: Wernet Mark P. , Oberle Lawrence G.
Published: March 2015

Laser anemometry offers a nonintrusive means for obtaining flow field information. Our current research efforts at NASA Lewis Research Center are focused on instrumenting a warm turbine facility with a laser anemometer system. In an effort to determine the laser anemometer system best qualified for the warm turbine environment, we compared the performance of a conventional laser fringe anemometer and a two spot time-of-flight system with a new, modified time-of-flight system, called a Four Spot laser anemometer. The comparison measurements were made in highly turbulent flows near walls. The Four Spot anemometer uses elliptical spots to increase the flow acceptance angle to be comparable to that of a Laser Fringe Anemometer. Also, the Four Spot uses an optical code that vastly simplifies the pulse detection processor. The results of the comparison measurements will exemplify which laser anemometer system is best suited to the hostile environment typically encountered in warm rotating turbomachinery.
High Performance Gearing for Modern Naval Gas Turbine Propulsion Systems
Authors: Kerpestein J. B.
Published: March 2015

This paper reviews present day technology in the field of gearing for modern naval propulsion systems. It gives the Royal Schelde views on some aspects of gearing concept design and discusses gearing noise, being a most important aspect of the naval ship noise signature. The paper describes design features of a number of naval gear transmissions for gasturbine and diesel engine driven surface vessels, such as the Canadian Patrol Frigate Gear Transmission System and the Royal Netherlands Navy M-class frigate gearing.

Some future trends and the probability of more stringent requirements concerning underwater noise are discussed.
HIDEC Adaptive Engine Control System Flight Evaluation Results
Authors: Yonke W. A. , Landy R. J. , Stewart J. F.
Published: March 2015

An integrated flight propulsion control mode called Adaptive Engine Control System (ADECS) has been developed and flight demonstrated on an F-15 test aircraft in the Highly Integrated Digital Electronic Control (HIDEC) Program, sponsored by the NASA Ames/Dryden Flight Research Center. The ADECS system provides additional engine thrust by increasing engine pressure ratio (EPR) at intermediate and afterburning power. The amount of EPR uptrim is modulated based on a unique predictor scheme for angle-of-attack and sideslip angle thus ensuring adequate fan stall margin for the engine. These predicted angles are derived from fight control and inertial navigation information.

The ADECS mode demonstrated substantial improvements in aircraft and engine performance in the flight evaluation program, even with only one engine incorporating EPR uptrim. Highlights were a 16% rate of climb increase, a 14% reduction in time to climb, and a 15% reduction in time to accelerate. Significant EPR uptrim capability was demonstrated with angles-of-attack up to 20 degrees.
An Option for High Power in Space
Authors: Boyle R. V. , Riple J. C.
Published: March 2015

The stated objective of the Strategic Defense Initiative (SDI) introduces needs for space-based electric power ranging up to hundreds of megawatts (MWe). The SDI Organization is calling for the development of new and innovative concepts to meet these needs.

Options for multi-megawatt and multi-hundred megawatt space power generating systems are presented in this paper. These options are based upon the gas turbine, one of the most mature and time-proven technologies available. Size- and mass-reduction studies utilizing innovative designs and new materials are conducted for the gas turbine. Two significantly different power levels with two thermal sources, nuclear and chemical combustion, are addressed.
Direct Coal-Fueled Combustion Turbines
Authors: Wenglarz Richard A.
Published: March 2015

Technology requirements for direct coal-fueled turbine systems are discussed. Combustion, emissions, and turbine life considerations are emphasized. Compact, short residence time combustors must provide acceptable combustion efficiencies and emissions using the coal fuels. The turbine flow path exposed to the products of combustion (POC) from those combustors must achieve acceptable deposition, erosion, and corrosion (DEC) lifetimes. Initial combustion and POC requirements are reviewed based on past experience and the results of a recent program to evaluate combustion, emissions, and DEC from a subscale turbine combustor.
Retrofit of a Modern Control System on an Early Design Gas Turbine
Authors: Nikkels H. , Little D.
Published: March 2015

The control systems on many older combustion turbines are often directly responsible for poor first-start reliability, low availability and high forced-outage rates. Indirectly, they may be the cause of mechanical and metallurgical problems. Dealing with aging control systems is a common experience for most turbine users and sometimes results in the premature retirement of equipment. The retrofit of a modern control system offers many advantages to the turbine user if it can be accomplished in an economic and timely manner.

The significant logistics, engineering, installation and commercial aspects of installing a modern control system on a 24-year old combustion turbine are described in this paper. The unit was restored to service with the new control system in early 1986, and the project was considered a success.
Momentum Exchanges and Energy Transfers in Cross Flow Fans
Authors: Mazur Joseph , Singh Trilochan
Published: March 2015

An experimental investigation of the flow in a cross flow fan at three operating conditions is reported. Velocity and pressure maps for the flow field are presented along with a determination of the momentum exchanges and energy transfers between the blading and the flow field regions.
Thermodynamic Study of an Indirect Fired Air Turbine Cogeneration System With Regeneration
Authors: Huang Francis F. , Naumowicz Tim
Published: March 2015

A previous study of an indirect fired air turbine cogeneration system has been extended to include the concept of regeneration. The effect of regenerator effectiveness and full regeneration as well as partial regeneration on system performance parameters (such as fuel utilization efficiency, power-to-heat ratio and second-law efficiency) are examined. An important conclusion of this study is that a regenerative gas turbine cogeneration system is capable of producing large power-to-heat ratios for various process conditions requiring the use of only moderate compressor compression ratio and moderately effective regenerators. It appears that this is an attractive system which could compete in a market that is currently dominated by internal combustion engines when a viable fludized bed air heater is available.
A High Performance PFB System for Utility Application
Authors: Berman Paul A. , Hynds Jeffrey A.
Published: March 2015

In the traditional pressurized fluid bed (PFB) power system, the PFB is located in the highest pressure portion of the power cycle, Figure 1. This results in the smallest volume flow through the PFB, but also requires the combustion products to flow through the entire expansion train. This is not expected to be a major problem when the PFB temperature is limited to 1600°F for effective sulfur capture and to avoid alkali vapors in the products of combustion. However, when topping combustion is added ahead of the turbine so as to reach state-of-the-art turbine inlet temperatures, a major risk for turbine corrosion and fouling develops.
Boosting Steam Plant Thermal Efficiency and Power Output Through the Addition of Gas Turbines
Authors: Linnemeijer M. J. J. , van Buijtenen J. P. , van Loon A. U.
Published: March 2015

This paper describes the conversion of existing conventional steam power plants into combined cycle plants.

A number of Dutch utility companies are currently performing or planning this conversion on their gas-fired power stations, mainly in order to conserve fuel.

Modifications of boiler and steam cycle, necessary for the new concept, are presented in general terms, together with a detailed description of one of the projects.
Forecasting “Wooden Round” Reliability During Preliminary Design
Authors: Weaks H.
Published: March 2015

The USAF’s R&M 2000 policy emphasizes the integration of reliability and maintainability considerations into a system’s preliminary design phase. This emphasis leads to unique requirements for turbine engines, including those of “wooden rounds” such as a HARPOON type missiles. In particular, it requires the development of tools for assessing the impact of design iterations on the reliability of “wooden round” weapon systems. Such tools must account for design iterations impact on storage, captive carry and launch reliability. A Markov approach is described in this paper, which provides an ability to track the reliability of a fleet of missiles/engines on a period by period basis, allowing one to assess when scheduled maintenance is appropriate and what components require such maintenance. Thus, inputs for Life Cycle Costing are generated, as well as the ability to determine tradeoffs between R&M and performance.
Design Concept and Performance of a Multistage Integrally Geared Centrifugal Compressor Series for Maximum Efficiencies and Operating Ranges
Authors: Simon H.
Published: March 2015

By its very design principle, the multistage integrally geared centrifugal compressor offers a number of advantages over other compressor concepts. They lead to distinctly higher machine efficiencies and wider operating ranges.
Aspects of Gas Turbine Noise Control in the Vicinity of Residential Areas
Authors: Fleischer Friedrich
Published: March 2015

This paper deals with problems of noise control involving gas turbine plants, particularly where they are installed near residential areas already subject to noise nuisance.

Noise control measures for existing industrial or power-generating plant are often designed to achieve an overall immitted noise level only marginally below the legal maximum.

Considerably enhanced measures are thus required for additional plant. However, the noise from a gas turbine plant has numerous individual sources and it is shown that a differentiated approach is required. Generally, progressive reductions in noise levels involve disproportionately greater increases in expenditure on appropriate measures.

Stringent environmental protection requirements necessitate cost-intensive solutions.
Gas Turbine Components Determining Repairability and Innovations to Refurbish Parts
Authors: Natole Ron
Published: March 2015

This paper deals with the repairability of hot gas path (turbine section), combustion, and compressor section (cold end) components in large (non-aeroderivative) industrial and utility gas turbines (4500 to 100,000KW). We will discuss; USA demographics, overhaul cycle recommendations, types of damage and part deterioration, more complete inspections repairability based on alloys and applications, and innovations for refurbishment.
A Time Marching Method for Calculating S2 Stream Surface Viscous Flow in a Single Rotor Compressor
Authors: Nai-Xing Chen , Li-Hong Dai
Published: March 2015

In this paper, a time marching method using a hopscotch algorithm and a stream-surface-fitted co-ordinate system for calculating steady viscous flow on the S2 stream surface is presented. It is convenient to express the Navier-Stokes equations by the non-orthogonal curvilinear co-ordinate system directly on the S2 stream surface because the blade force term which exists in the governing equations written on the meridional plane, disappears. Numerical results for the CAS single rotor research compressor of Institute of Engineering Thermophysics are compared with invisid calculation and experiment. It is shown that the computational results are agreed with experiment well.
Sealing of a Shrouded Rotor-Stator System With Pre-Swirl Coolant
Authors: El-Oun Z. B. , Neller P. H. , Turner A. B.
Published: March 2015

This paper describes an experimental study of a modelled gas turbine rotor-stator system using both pre-swirled blade coolant and radially outward flowing disc coolant. A double mitred rim seal was used together with, for some tests, an inner seal below the pre-swirl nozzles and blade feed holes in the rotor which were situated at the same radius. Some flow visualization results are presented together with measurements of pressure distribution, internal flow distribution and the minimum seal flow necessary to prevent ‘mainstream’ gas ingress into the wheelspace. The experiments are described for a range of rotational speeds up to Reθ = 1.8 × 106 for various combinations of pre-swirl flow, disc coolant flow and ‘blade’ coolant flow. The pre-swirled coolant flow is shown to have little effect on the pressure distribution below the pre-swirl nozzles but a gas concentration sampling technique showed that considerable contamination of the pre-swirled coolant by the frictionally heated disc coolant can occur. A clear pressure inversion effect was observed when coolant was provided by the pre-swirl nozzles only, whereby the pressure under the rim seal increased with increasing rotational speed. Except for the lowest flow rates, blade coolant flow is shown to increase the sealing flow requirement, but to a very much reduced extent when disc coolant flow is used simultaneously. A non-linear relationship between minimum sealing flow and Reθ is produced when the blade cooling system is in operation.
Mechanical Strength Characterization of Sintered Silicon Nitride Containing Oxide Additives
Authors: Govila R. K.
Published: March 2015

The flexural strength of a commercially available sintered silicon nitride (NGK-SN73) material containing various oxide additives (ceria, magnesia, zirconia and SrO) was determined in 4-point bending as a function of temperature (20 to 1200 C) in an air environment. Significantly, high strength (790 MPa) is maintained from room temperature to 800 C. At 900 C. and above, flexural strength decreased sharply. The sudden decrease in strength at temperatures of 900 and 1000 C is believed due to softening of the residual glass phase present in the material, and led to the presence of sub-critical crack growth. The extent of sub-critical crack growth and large viscous flow increased with increasing temperature (1100–1200 C) and led to degradation of material’s strength. In addition, the material was susceptible to oxidation at these temperatures as displayed by discoloration (dark gray to white) of the specimens.

Extensive flexural stress rupture testing was carried out in the temperature range 800 to 1000 C in order to determine (i) the material’s susceptibility for low temperature oxidation instability, (ii) the presence of sub-critical crack growth at low temperatures (700 to 800 C) and high temperatures (900 to 1000 C) and (iii) to identify allowable stress levels for limited time (≤ 100 h) without showing degradation of materials strength (failure, creep or oxidation).

Detailed fractographic evidence is presented to illustrate the type of strength controlling flaws present in the material at 20 C and above, and to reveal the presence of sub-critical crack growth displayed by the material in the temperature range 800 to 1000 C under stres-rupture mode.
Numerical Solution of Three-Dimensional Turbulent Flows for Modern Gas Turbine Components
Authors: Hah C. , Leylek J. H.
Published: March 2015

This paper describes the development and assessment of a computer code for three-dimensional compressible turbulent flows in modern gas turbine components. The code is based on a high-order upwinding relaxation scheme with fully conservative control volume. A three-dimensional Reynolds-averaged Navier-Stokes equation is solved with a two-equation turbulence model that has a low Reynolds number modification near the solid wall.

The code is applied to the study of compressible flow inside turbine blade rows of modern gas turbines. Measured data and calculations are carefully compared for the production and convection of aerodynamic loss to evaluate the code as an advanced design technique. The predicted aerodynamic performance is further compared with predictions based on current design techniques.
Computation of Incompressible Flow in Turbomachines Using the Primitive Variable Formulation
Authors: Chen J. H. , Abdallah S.
Published: March 2015

The primitive variable approach is adapted here for the solution of incompressible flow in turbomachines using non-staggered grids. In this approach, a pressure Poisson equation with Neumann boundary conditions is solved in lieu of the continuity equation. Solutions for the Poisson equation exist only if a compatibility condition is satisfied. This condition is not automatically satisfied on non-staggered grids. Failure to satisfy the compatibility condition results in non-convergent solutions. A consistent finite difference method which satisfies this condition using a non-staggered grid in general curvilinear coordinates is developed. Numerical solutions are obtained for the pressure equation using the successive over-relaxation method. The velocity field is computed from the momentum equations by explicitly marching in time. The computed solutions are compared with the available numerical results for both inviscid and viscous laminar flows in cascades.
Semiautomatic segmentation of atherosclerotic carotid artery wall volume using 3D ultrasound imaging
Authors: Hossain Md. Murad , AlMuhanna Khalid , Zhao Limin , Lal Brajesh K. , Sikdar Siddhartha
Published: March 2015

Purpose:

Rupture of atherosclerotic plaques in the carotid artery has been implicated in 20% of strokes. 3D ultrasound (US) imaging is emerging as an attractive method to quantify plaque burden and track changes in plaque longitudinally over time. However, plaque segmentation from US images is challenging because of poor boundary contrast and shadowing. The objective of this study is to develop and evaluate a semiautomatic segmentation algorithm with a novel stopping criterion for segmenting outer wall boundary (OWB) and lumen intima boundary (LIB) of common, internal, and external carotid artery from 3D US images for quantifying the vessel wall volume (VWV).

Methods:

3D US image volumes were acquired from ten subjects with asymptomatic carotid stenoses. Volumes were acquired using a mechanically scanned linear probe, and the reconstructed volume consisted of 21 slices acquired at an interslice distance of 1 mm. The authors used distance regularized level set method with edge‐based energy, region‐based energy, smoothness energy, and a novel stopping criterion to segment the LIB and OWB of carotid artery. The algorithm was initialized by six user‐selected points on the LIB and OWB in seven 2D cross‐sectional slices in each volume. An ellipse fitting and a stopping boundary‐based energy is proposed to smooth the OWB contour and to stop leaking of the evolving contour, respectively. The algorithm was compared against ground truth boundaries generated from manual segmentations. The dice similarity coefficient (DSC), Hausdorff distance (HD), and modified HD (MHD) were used as error metrics.

Results:

The authors’ proposed stopping boundary energy‐based stopping criterion was compared with percentage change of area and change of the MHD between evolving contours at successive iterations stopping criteria. The performance of the proposed algorithm was better than other two stopping criteria and yielded mean of LIBDSC = 88.78%, OWBDSC = 94.81%, LIBMHD = 0.26 mm, OWBMHD = 0.25 mm, LIBHD = 0.74 mm, and OWBHD = 0.80 mm. The Bland–Altman plot and correlation coefficient (r = 0.99) indicated a high agreement between ground truth and algorithm‐generated boundaries. The coefficient of variation (COV) and minimum detectable change of the VWV are 5.2% and 57.2 mm3 (5.18% of mean VWV), calculated from repeated measurements of the VWV by algorithm. The mean absolute distance between corresponding points of the algorithm‐generated and the ground truth boundaries was 0.25 mm.

Conclusions:

The authors have developed a semiautomatic segmentation algorithm for measuring the VWV of the carotid artery using 3D US images with reduced operator interaction and computational time and higher reproducibility using a commercially available 3D US transducer. Their method is a step forward toward routine longitudinal monitoring of 3D plaque progression.
Natural and sexual selection act on different axes of variation in avian plumage color
Authors: Dunn Peter O. , Armenta Jessica K. , Whittingham Linda A.
Published: March 2015

Sexual selection has acted on sexual differences in bird plumage color, while natural selection has acted on the color of both sexes.
Silver(I) as a widely applicable, homogeneous catalyst for aerobic oxidation of aldehydes toward carboxylic acids in water—“silver mirror”: From stoichiometric to catalytic
Authors: Liu Mingxin , Wang Haining , Zeng Huiying , Li Chao-Jun
Published: March 2015

A universal method for oxidation of aldehyde conducted by using atmospheric oxygen in water.
Amphibian Symbiotic Bacteria Do Not Show a Universal Ability To Inhibit Growth of the Global Panzootic Lineage of Batrachochytrium dendrobatidis
Authors: Antwis Rachael E. , Preziosi Richard F. , Harrison Xavier A. , Garner Trenton W. J.
Published: March 2015

Microbiomes associated with multicellular organisms influence the disease susceptibility of hosts. The potential exists for such bacteria to protect wildlife from infectious diseases, particularly in the case of the globally distributed and highly virulent fungal pathogen
Batrachochytrium dendrobatidis
of the global panzootic lineage (
B. dendrobatidis
GPL), responsible for mass extinctions and population declines of amphibians.
B. dendrobatidis
GPL exhibits wide genotypic and virulence variation, and the ability of candidate probiotics to restrict growth across
B. dendrobatidis
isolates has not previously been considered. Here we show that only a small proportion of candidate probiotics exhibited broad-spectrum inhibition across
B. dendrobatidis
GPL isolates. Moreover, some bacterial genera showed significantly greater inhibition than others, but overall, genus and species were not particularly reliable predictors of inhibitory capabilities. These findings indicate that bacterial consortia are likely to offer a more stable and effective approach to probiotics, particularly if related bacteria are selected from genera with greater antimicrobial capabilities. Together these results highlight a complex interaction between pathogens and host-associated symbiotic bacteria that will require consideration in the development of bacterial probiotics for wildlife conservation. Future efforts to construct protective microbiomes should incorporate bacteria that exhibit broad-spectrum inhibition of
B. dendrobatidis
GPL isolates.
Immunogenicity in Swine of Orally Administered Recombinant Lactobacillus plantarum Expressing Classical Swine Fever Virus E2 Protein in Conjunction with Thymosin α-1 as an Adjuvant
Authors: Xu Yi-Gang , Guan Xue-Ting , Liu Zhong-Mei , Tian Chang-Yong , Cui Li-Chun
Published: March 2015

Classical swine fever, caused by classical swine fever virus (CSFV), is a highly contagious disease that results in enormous economic losses in pig industries. The E2 protein is one of the main structural proteins of CSFV and is capable of inducing CSFV-neutralizing antibodies and cytotoxic T lymphocyte (CTL) activities
in vivo
. Thymosin α-1 (Tα1), an immune-modifier peptide, plays a very important role in the cellular immune response. In this study, genetically engineered
Lactobacillus plantarum
bacteria expressing CSFV E2 protein alone (
L. plantarum
/pYG-E2) and in combination with Tα1 (
L. plantarum
/pYG-E2-Tα1) were developed, and the immunogenicity of each as an oral vaccine to induce protective immunity against CSFV in pigs was evaluated. The results showed that recombinant
L. plantarum
/pYG-E2 and
L. plantarum
/pYG-E2-Tα1 were both able to effectively induce protective immune responses in pigs against CSFV infection by eliciting immunoglobulin A (IgA)-based mucosal, immunoglobulin G (IgG)-based humoral, and CTL-based cellular immune responses via oral vaccination. Significant differences (
P
< 0.05) in the levels of immune responses were observed between
L. plantarum
/pYG-E2-Tα1 and
L. plantarum
/pYG-E2, suggesting a better immunogenicity of
L. plantarum
/pYG-E2-Tα1 as a result of the Tα1 molecular adjuvant that can enhance immune responsiveness and augment specific lymphocyte functions. Our data suggest that the recombinant
Lactobacillus
microecological agent expressing CSFV E2 protein combined with Tα1 as an adjuvant provides a promising strategy for vaccine development against CSFV.
Vernalophrys algivore gen. nov., sp. nov. (Rhizaria: Cercozoa: Vampyrellida), a New Algal Predator Isolated from Outdoor Mass Culture of Scenedesmus dimorphus
Authors: Gong Yingchun , Patterson David J. , Li Yunguang , Hu Zixuan , Sommerfeld Milton , Chen Yongsheng , Hu Qiang
Published: March 2015

Microbial contamination is the main cause of loss of biomass yield in microalgal cultures, especially under outdoor environmental conditions. Little is known about the identities of microbial contaminants in outdoor mass algal cultures. In this study, a new genus and species of vampyrellid amoeba,
Vernalophrys algivore
, is described from cultures of
Scenedesmus
dimorphus
in open raceway ponds and outdoor flat-panel photobioreactors. This vampyrellid amoeba was a significant grazer of
Scenedesmus
and was frequently associated with a very rapid decline in algal numbers. We report on the morphology, subcellular structure, feeding behavior, molecular phylogeny, and life cycle. The new amoeba resembles
Leptophrys
in the shape of trophozoites and pseudopodia and in the mechanism of feeding (mainly by engulfment). It possesses two distinctive regions in helix E10_1 (nucleotides 117 to 119, CAA) and E23_1 (nucleotides 522 and 523, AG) of the 18S rRNA gene. It did not form a monophyletic group with
Leptophrys
in molecular phylogenetic trees. We establish a new genus,
Vernalophrys
, with the type species
Vernalophrys algivore
. The occurrence, impact of the amoeba on mass culture of
S. dimorphus
, and means to reduce vampyrellid amoeba contamination in
Scenedesmus
cultures are addressed. The information obtained from this study will be useful for developing an early warning system and control measures for preventing or treating this contaminant in microalgal mass cultures.
Polyphenolic Extract from Maple Syrup Potentiates Antibiotic Susceptibility and Reduces Biofilm Formation of Pathogenic Bacteria
Authors: Maisuria Vimal B. , Hosseinidoust Zeinab , Tufenkji Nathalie
Published: March 2015

Phenolic compounds are believed to be promising candidates as complementary therapeutics. Maple syrup, prepared by concentrating the sap from the North American maple tree, is a rich source of natural and process-derived phenolic compounds. In this work, we report the antimicrobial activity of a phenolic-rich maple syrup extract (PRMSE). PRMSE exhibited antimicrobial activity as well as strong synergistic interaction with selected antibiotics against Gram-negative clinical strains of
Escherichia coli
,
Proteus mirabilis
, and
Pseudomonas aeruginosa
. Among the phenolic constituents of PRMSE, catechol exhibited strong synergy with antibiotics as well as with other phenolic components of PRMSE against bacterial growth. At sublethal concentrations, PRMSE and catechol efficiently reduced biofilm formation and increased the susceptibility of bacterial biofilms to antibiotics. In an effort to elucidate the mechanism for the observed synergy with antibiotics, PRMSE was found to increase outer membrane permeability of all bacterial strains and effectively inhibit efflux pump activity. Furthermore, transcriptome analysis revealed that PRMSE significantly repressed multiple-drug resistance genes as well as genes associated with motility, adhesion, biofilm formation, and virulence. Overall, this study provides a proof of concept and starting point for investigating the molecular mechanism of the reported increase in bacterial antibiotic susceptibility in the presence of PRMSE.
Genome Sequence and Transcriptome Analysis of Meat-Spoilage-Associated Lactic Acid Bacterium Lactococcus piscium MKFS47
Authors: Andreevskaya Margarita , Johansson Per , Laine Pia , Smolander Olli-Pekka , Sonck Matti , Rahkila Riitta , Jääskeläinen Elina , Paulin Lars , Auvinen Petri , Björkroth Johanna
Published: March 2015

Lactococcus piscium
is a psychrotrophic lactic acid bacterium and is known to be one of the predominant species within spoilage microbial communities in cold-stored packaged foods, particularly in meat products. Its presence in such products has been associated with the formation of buttery and sour off-odors. Nevertheless, the spoilage potential of
L. piscium
varies dramatically depending on the strain and growth conditions. Additional knowledge about the genome is required to explain such variation, understand its phylogeny, and study gene functions. Here, we present the complete and annotated genomic sequence of
L. piscium
MKFS47, combined with a time course analysis of the glucose catabolism-based transcriptome. In addition, a comparative analysis of gene contents was done for
L. piscium
MKFS47 and 29 other lactococci, revealing three distinct clades within the genus. The genome of
L. piscium
MKFS47 consists of one chromosome, carrying 2,289 genes, and two plasmids. A wide range of carbohydrates was predicted to be fermented, and growth on glycerol was observed. Both carbohydrate and glycerol catabolic pathways were significantly upregulated in the course of time as a result of glucose exhaustion. At the same time, differential expression of the pyruvate utilization pathways, implicated in the formation of spoilage substances, switched the metabolism toward a heterofermentative mode. In agreement with data from previous inoculation studies,
L. piscium
MKFS47 was identified as an efficient producer of buttery-odor compounds under aerobic conditions. Finally, genes and pathways that may contribute to increased survival in meat environments were considered.
The N-Terminal GH10 Domain of a Multimodular Protein from Caldicellulosiruptor bescii Is a Versatile Xylanase/β-Glucanase That Can Degrade Crystalline Cellulose
Authors: Xue Xianli , Wang Rong , Tu Tao , Shi Pengjun , Ma Rui , Luo Huiying , Yao Bin , Su Xiaoyun
Published: March 2015

The genome of the thermophilic bacterium
Caldicellulosiruptor bescii
encodes three multimodular enzymes with identical C-terminal domain organizations containing two consecutive CBM3b modules and one glycoside hydrolase (GH) family 48 (GH48) catalytic module. However, the three proteins differ much in their N termini. Among these proteins, CelA (or
C. bescii
Cel9A [CbCel9A]/Cel48A) with a GH9/CBM3c binary partner in the N terminus has been shown to use a novel strategy to degrade crystalline cellulose, which leads to its outstanding cellulose-cleaving activity. Here we show that
C. bescii
Xyn10C (CbXyn10C), the N-terminal GH10 domain from CbXyn10C/Cel48B, can also degrade crystalline cellulose, in addition to heterogeneous xylans and barley β-glucan. The data from substrate competition assays, mutational studies, molecular modeling, and docking point analyses point to the existence of only one catalytic center in the bifunctional xylanase/β-glucanase. The specific activities of the recombinant CbXyn10C on Avicel and filter paper were comparable to those of GH9/CBM3c of the robust CelA expressed in
Escherichia coli
. Appending one or two cellulose-binding CBM3bs enhanced the activities of CbXyn10C in degrading crystalline celluloses, which were again comparable to those of the GH9/CBM3c-CBM3b-CBM3b truncation mutant of CelA. Since CbXyn10C/Cel48B and CelA have similar domain organizations and high sequence homology, the endocellulase activity observed in CbXyn10C leads us to speculate that CbXyn10C/Cel48B may use the same strategy that CelA uses to hydrolyze crystalline cellulose, thus helping the excellent crystalline cellulose degrader
C. bescii
acquire energy from the environment. In addition, we also demonstrate that CbXyn10C may be an interesting candidate enzyme for biotechnology due to its versatility in hydrolyzing multiple substrates with different glycosidic linkages.