bluuebunny/crossref_metadata_2025 huggingface dataset:
Details of Axial-Compressor Shrouded Stator Cavity Flows
Authors: Wellborn Steven R.
Published: July 2014

Data that reveal the structure and character of the flow in and near the cavities of compressor shrouded stators are reviewed. Results were obtained from low-speed multistage compressor measurements and simulations and generic high-speed cavity simulations. The experimental measurements were acquired with slow and fast response instrumentation. The numerical simulations were collected with two different flow solvers. The data are presented to provide compressor designers some indication of the complexities of the flow within shrouded stator cavities and to provide a datum for further studies on more complex geometries and flow conditions.

The data suggest surprisingly similar flow structures within most cavities including spatial and temporal flow field variations. In general, the flow in the cavities involved fluid moving in the circumferential direction with lower momentum than powerstream fluid. The difference in momentum is adjusted through a shear layer in the radial direction near the powerstream/cavity interface. Circumferential variations in flow properties also exist, the most prominent being caused by the upstream potential influence of the downstream blade. This influence caused the fluid within the cavities near the leading edges of the airfoils to be driven radially inward relative to fluid near mid-pitch. Some data are presented that suggest powerstream secondary flows dictate which fluid particles are ingested in the downstream cavity across the stator pitch. Vortical flow structures, similar to those set up by a driven cavity, dominate the axial variations in flow. The position and structure of these vortical structures are dependent upon the powerstream flow field and the cavity geometry.

Examining some interdependencies between cavity flow parameters concludes discussions of cavity flow field characteristics. A known relation between cavity leakage amount and tangential velocity is reiterated. Cavity rotational speed and stator exit swirl are also shown to influence the cavity tangential velocity. Increasing rotational speed tends to increase the tangential velocity through the cavity. Increasing the stator exit swirl reduces the tangential velocity increase.
Convective Heat Transfer and Aerodynamics in Axial Flow Turbines
Authors: Dunn Michael G.
Published: July 2014

The primary focus of this paper is convective heat transfer in axial flow turbines. Research activity involving heat transfer generally separates into two related areas: predictions and measurements. The problems associated with predicting heat transfer are coupled with turbine aerodynamics because proper prediction of vane and blade surface-pressure distribution is essential for predicting the corresponding heat-transfer distribution. The experimental community has advanced to the point where time-averaged and time-resolved 3-D heat-transfer data for the vanes and blades are obtained routinely by those operating full-stage rotating turbines. However, there are relatively few CFD codes capable of generating 3-D predictions of the heat-transfer distribution, and where these codes have been applied the results suggest that additional work is required.

This paper outlines the progression of work done by the heat transfer community over the last several decades as both the measurements and the predictions have improved to current levels. To properly frame the problem, the paper reviews the influence of turbine aerodynamics on heat transfer predictions. This includes a discussion of time-resolved surface-pressure measurements with predictions and the data involved in forcing function measurements. The ability of existing 2-D and 3-D Navier Stokes codes to predict the proper trends of the time-averaged and unsteady pressure field for full-stage rotating turbines is demonstrated. Most of the codes do a reasonably good job of predicting the surface-pressure data at vane and blade midspan, but not as well near the hub or the tip region for the blade. In addition, the ability of the codes to predict surface-pressure distribution is significantly better than the corresponding heat-transfer distributions.

Heat-transfer codes are validated against measurements of one type or another. Sometimes the measurements are performed using full rotating rigs, and other times a much more simple geometry is used. In either case, it is important to review the measurement techniques currently used. Heat-transfer predictions for engine turbines are very difficult because the boundary conditions are not well known. The conditions at the exit of the combustor are generally not well known and a section of this paper discusses that problem. The majority of the discussion is devoted to external heat transfer with and without cooling, turbulence effects, and internal cooling.

As the design community increases the thrust to weight ratio and the turbine inlet temperature, there remain many turbine-related heat transfer issues. Included are film cooling modeling, definition of combustor exit conditions, understanding of blade tip distress, definition of hot streak migration, component fatigue, loss mechanisms in the low turbine, and many others. Several suggestions are given herein for research and development areas for which there is potentially high payoff to the industry with relatively small risk.
Inlet Fogging of Gas Turbine Engines: Detailed Climatic Analysis of Gas Turbine Evaporative Cooling Potential
Authors: Chaker Mustapha , Meher-Homji Cyrus B. , Mee Thomas , Nicolson Alex
Published: July 2014

Inlet fogging of gas turbine engines has attained considerable popularity due to the ease of installation and the relatively low first cost compared to other inlet cooling methods. With increasing demand for power and with shortages envisioned especially during the peak load times during the summers, there is a need to boost gas turbine power. There is a sizable evaporative cooling potential throughout the world when the climatic data is evaluated based on an analysis of coincident wet bulb and dry bulb information. This data is not readily available to plant users. In this paper, a detailed climatic analysis is made of 122 locations in the US to provide the hours of cooling that can be obtained by direct evaporative cooling. This data will allow gas turbine operators to easily make an assessment of the economics of evaporative cooling. The paper also covers an introduction to direct evaporative cooling and the methodology and data analysis used to derive the cooling potential in different regions of the US. Simulation runs have been made for gas turbine simple cycles using a reference plant based on a GE Frame 7111EA gas turbine at the 122 locations studied in the US to provide a feel for the sensitivity of operation with inlet fogging.
The Navy 500-Hour Test (NFHT) of the Intercooled Recuperated Gas Turbine Engine System (ICR)
Authors: Grala Carl P. , House Edward M.
Published: July 2014

The Intercooled Recuperated Gas Turbine Engine System (ICR) is being developed by the United States Navy (USN) for shipboard application as a prime mover. The major development goal of the program is reduced fuel consumption relative to the LM2500, the current fielded gas turbine prime mover. This paper describes a 500-hour endurance test of the ICR system. The test was conducted at Naval Surface Warfare Center Carderock Division (NSWCCD), Philadelphia, in accordance with USN requirements which mimicked the qualification requirements for the system.

Data to assess the capability of the ICR to pass the qualification test was collected. Overall, the ICR has demonstrated a readiness to commence qualification testing.

The ICR completed the test with a total accumulated operating time of 457 hours and total endurance time of 322 hours. Achievement of the planned 500 endurance hours was precluded by persistent facility waterbrake problems.
An Experimental and Numerical Investigation Into the Mechanisms of Rotating Instability
Authors: März Joachim , Hah Chunill , Neise Wolfgang
Published: July 2014

This paper reports on an experimental and numerical investigation aimed at understanding the mechanisms of rotating instabilities in a low speed axial flow compressor. The phenomena of rotating instabilities in the current compressor were first identified with an experimental study. Then, an unsteady numerical method was applied to confirm the phenomena and to interrogate the physical mechanisms behind them. The experimental study was conducted with high-resolution pressure measurements at different clearances, employing a double phase-averaging technique. The numerical investigation was performed with an unsteady 3-D Navier-Stokes method that solves for the entire blade row. The current study reveals that a vortex structure forms near the leading edge plane. This vortex is the result of interactions among the classical tip-clearance flow, axially reversed endwall flow, and the incoming flow. The vortex travels from the suction side to the pressure side of the passage at roughly half of the rotor speed. The formation and movement of this vortex seem to be the main causes of unsteadiness when rotating instability develops. Due to the nature of this vortex, the classical tip-clearance flow does not spill over into the following blade passage. This behavior of the tip-clearance flow is why the compressor operates in a stable mode even with the rotating instability, unlike traditional rotating stall phenomena.
Materials Selection for High Temperature Metal Recuperators
Authors: Harper Mark A. , Smith Gaylord D. , Maziasz Philip J. , Swindeman Robert W.
Published: July 2014

One method of increasing the efficiency of gas turbines is the use of a heat exchanger to capture energy from the exhaust gas of the system. In particular, prime-surface and plate-fin recuperators are used to simply transfer heat from the turbine exhaust to the air leaving the compressor discharge and entering the combustor. In so doing, less fuel is required to heat the inlet air to the final combustion temperature. Desirable material requirements include a low coefficient of thermal expansion, high thermal conductivity, high temperature strength, adequate environmental resistance and good fabrication characteristics. For most industrial applications the 300 and 400 series stainless steels are currently used for the material of construction. This paper discusses the properties of higher Ni-containing alloys and their possible use as recuperator materials for advanced microturbines currently being developed.
Development of Fault Diagnosis and Failure Prediction Techniques for Small Gas Turbine Engines
Authors: Davison Craig R. , Birk A. M.
Published: July 2014

A computer model of a gas turbine auxiliary power unit was produced to develop techniques for fault diagnosis and prediction of remaining life in small gas turbine engines. Due to the relatively low capital cost of small engines it is important that the techniques have both low capital and operating costs.

Failing engine components were identified with fault maps, and an algorithm was developed for predicting the time to failure, based on the engine’s past operation. Simulating daily engine operation over a maintenance cycle tested the techniques for identification and prediction. The simulation included daily variations in ambient conditions, operating time, load, engine speed and operating environment, to determine the amount of degradation per day. The algorithm successfully adapted to the daily changes and corrected the operating point back to standard conditions to predict the time to failure.
Design, Fabrication, and Testing of a Semi-Closed Cycle Gas Turbine Engine
Authors: Rodgers C.
Published: July 2014

A small semi-closed gas turbine was designed, fabricated, and tested to demonstrate the cycle the cycle feasibility with exhaust gas recirculation. The demonstrator unit comprised a low pressure spool compressor and turbine supercharging a high pressure spool compressor and turbine, whose exhaust passed through a recuperator, and was subsequently split, one half being recirculated to the high pressure spool compressor inlet via an intercooler, and the remaining half expanded across the low pressure spool turbine.

The design and fabrication phases proceeded on schedule but commencement of engine development testing encountered mechanical difficulties. These were eventually resolved and shakedown testing of the demonstrator accomplished prior to final contractual delivery.

The demonstration program was funded under a NASA LeRc contract NAS3-27396.
An Assessment Method of Power Plants Using Genetic Algorithms
Authors: Codeceira Neto Alcides , Pilidis Pericles
Published: July 2014

The performance assessment of power plants is a complex task, which involves many calculations. Increasing the number of plant components with the introduction of new technologies available in the international market, it increases the complexity of performance analysis of power cycles.

The present paper describes a process for optimising a conventional gas turbine combined cycle power plant. In this paper the method of assessing thermal power plants takes into account the exergy method and carries out along with optimisation of the whole plant based on maximising overall plant exergetic efficiency and minimising energy loss rejected to the atmosphere. The performance assessment of power plants using the exergy method considers the overall plant exergetic efficiency and the exergy destruction in the various components of the plant. The exergy method highlights irreversibility within the plant components, and it is of particular interest in this investigation.

Due to the large number of equations with many variables taking part in the whole calculation and also considering constraints imposed to some variables, a genetic algorithm is recommended as the optimisation tool for the assessment method. Genetic Algorithms are adaptive methods which may be used to solve search and optimisation problems. They are based on the genetic processes of biological organisms. Over many generations, natural populations evolve according to the principles of natural selection and “survival of the fittest”, first clearly stated by Charles Darwin in his book “The Origin of Species”. Genetic algorithms do not require complicate mathematical calculations like the evaluation of derivatives necessary to be considered in conventional optimisation techniques.
Experimental Self-Sensing Results for a Magnetic Bearing
Authors: Montie Dominick T. , Maslen Eric H.
Published: July 2014

Experimental results are presented for a self-sensing magnetic bearing system operated in both the linear and saturation regions. When the magnetic actuator operates exclusively in the linear region, a simple, inexpensive analog estimation technique is implemented. When operating conditions are expected to drive the bearing into magnetic saturation, a digital-analog hybrid estimator is introduced. It follows that expected operating conditions of the magnetic bearing system determine the necessary complexity of the position estimator. Further, the performance of the analog hardware plays a critical role in the operation of the estimator from the perspective of signal gain and phase. Such hardware issues, as they relate to estimator performance, are discussed. Recommendations for improved estimator performance in conjunction with reduced estimator cost and complexity follow.
Modernization of a Turbine Engine Test Facility Utilizing a Real-Time Facility Model and Simulation
Authors: Montgomery Peter A. , Burdette Rick , Wilhite Larry , Salita Steve
Published: July 2014

Arnold Engineering Development Center (AEDC) recently began modernizing its turbine engine test facilities as part of its Test Operations Modernization & Integration Project (TOMIP). This new approach is designed to reduce downtime of the facility with the help of a real-time facility model and simulation. The challenge is to apply control system improvements, achieve control room consolidation, and provide operator training for complex test facilities without negatively impacting ongoing test projects. The TOMIP approach has been to target specific subsystems among all the AEDC test cells, rather than focusing on all the subsystems of a specific set of test cells. This makes it possible to minimize downtime and maximize cost savings. For each targeted subsystem, requirements are identified and hardware and software solutions are designed. These solutions are then validated through the use of models and simulations in a development/training area using identical hardware and software. Upon completion of this validation, the hardware is installed in the field and connected to the existing hardware for a complete checkout of the system. This paper discusses the first application in the field of the TOMIP approach with the modernization of specific subsystems for a turbine engine test facility. The real-time model and simulation utilized, the interface systems, and the communication architecture of the overall system are described. The lessons learned through this successful approach, and the potential savings through reduced facility downtime are discussed as well.
The Implementation of Spray Forming for High Temperature Casing Applications
Authors: Partridge Alan , Henderson Michael B. , Cole David G. , Andrews Paul
Published: July 2014

Many current gas turbine casings are manufactured using conventional wrought processing routes. Although well established this approach often requires numerous and complex processing steps. This can result in relatively long component lead times and high part costs. In an attempt to reduce lead times and cost the production of parts using the spray-forming process is under consideration.

In the spray forming process the material is deposited from the molten state to produce a near net shape ring. The deposited ring is then subject to hot isostatic pressing (HIP) and/or ring rolling to consolidate the material and expand the ring to the required size. The material thus produced is usually relatively fine grained and can have a different balance of properties compared to conventionally processed alloys. However, the major advantage is that cost reductions can be achieved through the elimination of many process steps. In the current work a high temperature nickel alloy, RS5, has been produced as a spray formed ring. The influence of HIP and ring rolling have been investigated and a detailed microstructure-mechanical property assessment of the material has been carried out. The results of this work will be reported and the implications of the work on cost and manufacturing issues will be discussed.
Application of Phase-Lagged Boundary Conditions to Rotor/Stator Interaction
Authors: Burgos Manuel Antonio , Corral Roque
Published: July 2014

The phase-lagged boundary condition concept is briefly reviewed, both for its classical application to vibrating blades and rotor/stator interaction. A simple conceptual model for rotor/stator interaction, compatible with the phase lagged boundary conditions is proposed. Careful comparisons between single-passage and full annulus inviscid simulations have been made to validate the method and demonstrate that potential differences between both approaches are associated to slight changes in the scheme due to the phase-shifted periodic boundary conditions. Finally the Erdos and Shape Correction methods are compared.
Computerized Noise Emission Simulation for a Multiunit Gas Compressor Station
Authors: Resch Roderich , Pointner Luwig
Published: July 2014

This paper describes a computer program simulation of the impact of noise emissions of Austrian’s largest gas compressor plant. The case history covers a multi-source compressor plant containing LM 2500 and frame 3 gas turbines as well as the noise emissions of gas-air coolers and dehydration equipment. The paper outlines further how potentials of noise reduction can be identified and how the noise impact of future projects can be simulated with the help of a computerized model.
Creep and Thermomechanical Fatigue Modelling of Single Crystal Superalloy Turbine Blades
Authors: Henderson M. B. , Ward T. J. , Harrison G. F. , Hughes M.
Published: July 2014

Gas turbine engine rotor blades are being manufactured increasingly from nickel-based single crystal superalloys. Intended for use in the hottest sections of the turbine, these alloys are capable of providing large increases in component endurance and reliability, as well as engine performance due to increased turbine entry temperature levels. To ensure full utilisation and calculation of safe component life times, accurate modelling of the non-linear deformation suffered during typical duty cycles is needed. The Mechanical Sciences Sector at DERA, Farnborough has developed an anisotropic creep analysis and modelling capability specifically targeted at simulating the high temperature creep and thermomechanical fatigue behaviour of superalloy single crystal specimens and turbine blades under complex loading and non-isothermal conditions. The model has been incorporated into a user material subroutine (UMAT) for use with the ABAQUS finite element programme, within which the inelastic strain is considered to be a combination of the instantaneous plastic strains, time-dependent creep strains and thermal strains. A recent collaborative programme between Alstom Power (UK) and DERA has applied this model to generate predictions for the anisotropic creep and thermomechanical fatigue behaviour of a number of specimen and blade designs.
Fat Cells Gain New Identities
Authors: Nascimento Emmani B. M. , Boon Mariëtte R. , Lichtenbelt Wouter D. van Marken
Published: July 2014

ASC-1, PAT2, and P2RX5 are newly identified cell-surface proteins that may distinguish brown/beige from white adipocytes in mouse and human adipose tissue (Ussar
et al
., this issue).
Host-Directed Antimicrobial Drugs with Broad-Spectrum Efficacy against Intracellular Bacterial Pathogens
Authors: Czyż Daniel M. , Potluri Lakshmi-Prasad , Jain-Gupta Neeta , Riley Sean P. , Martinez Juan J. , Steck Theodore L. , Crosson Sean , Shuman Howard A. , Gabay Joëlle E.
Published: July 2014

We sought a new approach to treating infections by intracellular bacteria, namely, by altering host cell functions that support their growth. We screened a library of 640 Food and Drug Administration (FDA)-approved compounds for agents that render THP-1 cells resistant to infection by four intracellular pathogens. We identified numerous drugs that are not antibiotics but were highly effective in inhibiting intracellular bacterial growth with limited toxicity to host cells. These compounds are likely to target three kinds of host functions: (i) G protein-coupled receptors, (ii) intracellular calcium signals, and (iii) membrane cholesterol distribution. The compounds that targeted G protein receptor signaling and calcium fluxes broadly inhibited
Coxiella burnetii
,
Legionella pneumophila
,
Brucella abortus
, and
Rickettsia conorii
, while those directed against cholesterol traffic strongly attenuated the intracellular growth of
C. burnetii
and
L. pneumophila
. These pathways probably support intracellular pathogen growth so that drugs that perturb them may be therapeutic candidates. Combining host- and pathogen-directed treatments is a strategy to decrease the emergence of drug-resistant intracellular bacterial pathogens.

IMPORTANCE
Although antibiotic treatment is often successful, it is becoming clear that alternatives to conventional pathogen-directed therapy must be developed in the face of increasing antibiotic resistance. Moreover, the costs and timing associated with the development of novel antimicrobials make repurposed FDA-approved drugs attractive host-targeted therapeutics. This paper describes a novel approach of identifying such host-targeted therapeutics against intracellular bacterial pathogens. We identified several FDA-approved drugs that inhibit the growth of intracellular bacteria, thereby implicating host intracellular pathways presumably utilized by bacteria during infection.
The Emergence of Bacterial “Hopeful Monsters”
Authors: Croucher Nicholas J. , Klugman Keith P.
Published: July 2014

The global spread of antibiotic-resistant bacteria has largely been driven by the dissemination of successful lineages. A particularly important example is sequence type (ST) 258 of
Klebsiella pneumoniae
, a common cause of health care-associated infections. Representatives of this lineage carry a variable array of plasmid-borne resistance genes, typically including a carbapenemase effective against the full range of clinically important β-lactams. In their recent
mBio
article, Chen et al. [
mBio
5(3):e01355-14] described how ST258 emerged through “hybridization” between two other strains, with a second recombination resulting in the diversification of a key antigen. This commentary describes the findings in the context of other examples where saltational evolution has resulted in the sudden emergence of important pathogenic bacteria.
‘Split posterior tooth’: conservative clinical re-attachment
Authors: Abraham Sathish , Chacko Lisa Neelathil
Published: July 2014

Trauma is the prime causative factor for fracture of teeth/dentition. Many procedural management options are followed successfully in relation to the anterior teeth. However, most posterior cases where the tooth is fractured have only limited options to pursue to save the tooth. Fractured teeth, whether they are vital/non-vital, are predominantly managed with surgical options. This paper discusses a conservative approach to reattaching a split posterior tooth. A split tooth situation is mostly an absolute indication for extraction, but the clinician may go in for extensive surgical procedures if he/she wishes to save it. The reattachment of the tooth can be successfully done and it can be put to function. This paper discusses how a split posterior tooth can be treated successfully, although depending on multiple factors. A full crown cemented after successful reattachment and root canal therapy would provide sufficient support in order for the tooth to heal.
Remote sensing of the environment with small unmanned aircraft systems (UASs), part 2: scientific and commercial applications
Authors: Whitehead Ken , Hugenholtz Chris H. , Myshak Stephen , Brown Owen , LeClair Adam , Tamminga Aaron , Barchyn Thomas E. , Moorman Brian , Eaton Brett
Published: July 2014

Small unmanned aircraft systems (UASs) are often suited to applications where the cost, resolution, and (or) operational inflexibility of conventional remote sensing platforms is limiting. Remote sensing with small UASs is still relatively new, and there is limited understanding of how the data are acquired and used for scientific purposes and decision making. This paper provides practical guidance about the opportunities and limitations of small UAS-based remote sensing by highlighting a small sample of scientific and commercial case studies. Case studies span four themes: (i) mapping, which includes case studies to measure aggregate stockpile volumes and map river habitat; (ii) feature detection, which includes case studies on grassland image classification and detection of agricultural crop infection; (iii) wildlife and animal enumeration, with case studies describing the detection of fish concentrations during a major salmon spawning event, and cattle enumeration at a concentrated animal feeding operation; (iv) landscape dynamics with a case study of arctic glacier change. Collectively, these case studies only represent a fraction of possible remote sensing applications using small UASs, but they provide insight into potential challenges and outcomes, and help clarify the opportunities and limitations that UAS technology offers for remote sensing of the environment.
Observer-Based Synchronization of Chaotic Systems with Both Parameter Uncertainties and Channel Noise
Authors: Jiang Xiu , Yang Junqi , Zhu Fanglai , Xu Liyun
Published: July 2014

This paper considers observer-based chaos synchronization and chaos-based secure communication problems for a class of uncertain chaotic systems with both parameter uncertainties and channel noise. First, by introducing an augmented vector, the original system is transformed into a new system which has no channel noise. Second, based on the concept of relative degree, an auxiliary drive signal vector is constructed so that the observer matching condition is satisfied. Third, a reduced-order observer is designed to estimate the states of the new augmented system. Then, a high-order high-gain sliding mode observer is considered to estimate the auxiliary drive signals and their derivatives exactly in a finite time. After this, the combination of the reduced-order observer and the high-order high-gain sliding mode observer is used as the receiver in the secure communication mechanism. And a kind of secure information recovery method is developed. Finally, a four-dimensional hyperchaos system is used as the simulation example to illustrate the effectiveness of the proposed methods.
Topological Sequence Entropy and Chaos
Authors: Liu Xin , Wang Huoyun , Fu Heman
Published: July 2014

A dynamical system is called a null system, if the topological sequence entropy along any strictly increasing sequence of non-negative integers is 0. Given 0 ≤ p ≤ q ≤ 1, a dynamical system is [Formula: see text] chaotic, if there is an uncountable subset in which any two different points have trajectory approaching time set with lower density p and upper density q. It shows that, for any 0 ≤ p < q ≤ 1 or p = q = 0 or p = q = 1, a dynamical system which is null and [Formula: see text] chaotic can be realized.
Derivation of the Amplitude Equation for Reaction–Diffusion Systems via Computer-Aided Multiple-Scale Expansion
Authors: Wang Kaier , Steyn-Ross Moira L. , Steyn-Ross D. Alistair , Wilson Marcus T.
Published: July 2014

The amplitude equation describes a reduced form of a reaction–diffusion system, yet still retains its essential dynamical features. By approximating the analytic solution, the amplitude equation allows the examination of mode instability when the system is near a bifurcation point. Multiple-scale expansion (MSE) offers a straightforward way to systematically derive the amplitude equations. The method expresses the single independent variable as an asymptotic power series consisting of newly introduced independent variables with differing time and space scales. The amplitude equations are then formulated under the solvability conditions which remove secular terms. To our knowledge, there is little information in the research literature that explains how the exhaustive workflow of MSE is applied to a reaction–diffusion system. In this paper, detailed mathematical operations underpinning the MSE are elucidated, and the practical ways of encoding these operations using MAPLE are discussed. A semi-automated MSE computer algorithm Amp_solving is presented for deriving the amplitude equations in this research. Amp_solving has been applied to the classical Brusselator model for the derivation of amplitude equations when the system is in the vicinity of a Turing codimension-1 and a Turing–Hopf codimension-2 bifurcation points. Full open-source Amp_solving codes for the derivation are comprehensively demonstrated and available to the public domain.
Local Bifurcations of Electric Distribution Networks with Renewable Energy
Authors: Sheng Hao , Chiang Hsiao-Dong , Jiang Yan-Feng
Published: July 2014

Recent years have witnessed a growing trend towards the development and deployment of distributed generation (DG). It is shown that electric distribution networks with DGs can encounter two types of local bifurcations: saddle-node bifurcation and structure-induced bifurcation. The structure-induced bifurcation occurs when a transition between two structures of the distribution network takes place due to limited amount of reactive power supports from renewable energies. The saddle-node bifurcation occurs when the underlying distribution network reaches the limit of its delivery capability. The consequence of structure-induced bifurcation is an immediate instability induced by reactive power limits of renewable energy. It is numerically shown that both types of local bifurcations can occur at both small distribution networks and large-scale distribution networks with DGs. Physical explanations of these two local bifurcations are provided. Studies of local bifurcations in distribution networks provide insights regarding how to design controls to enhance distribution networks with DGs.
Befriending Askey–Wilson polynomials
Authors: Szabłowski Paweł J.
Published: July 2014

We recall five families of polynomials constituting a part of the so-called Askey–Wilson scheme. We do this to expose properties of the Askey–Wilson (AW) polynomials that constitute the last, most complicated element of this scheme. In doing so we express AW density as a product of the density that makes q-Hermite polynomials orthogonal times a product of four characteristic function of q-Hermite polynomials (2.9) just pawing the way to a generalization of AW integral. Our main results concentrate mostly on the complex parameters case forming conjugate pairs. We present new fascinating symmetries between the variables and some newly defined (by the appropriate conjugate pair) parameters. In particular in (3.12) we generalize substantially famous Poisson–Mehler expansion formula (3.16) in which q-Hermite polynomials are replaced by Al-Salam–Chihara polynomials. Further we express Askey–Wilson polynomials as linear combinations of Al-Salam–Chihara (ASC) polynomials. As a by-product we get useful identities involving ASC polynomials. Finally by certain re-scaling of variables and parameters we reach AW polynomials and AW densities that have clear probabilistic interpretation.
ARE REAL OPTIONS "REAL"? ISOLATING UNCERTAINTY FROM RISK IN REAL OPTIONS ANALYSIS
Authors: SO LEH-CHYAN
Published: July 2014

This paper derives an adjusted Black–Scholes pricing formula. In separating risk and uncertainty using the robust control technique, we find that both uncertainty and risk raise management's subjective evaluation of real options. We suggest a simple method to filter the risk of the project and to acquire a more reliable value of real options without the influence of uncertainty. In addition, we propose that an investment opportunity may be postponed inappropriately, as under uncertainty the exercise of investment may be delayed by the project manager. To our knowledge, any similar quantitative methods have not hitherto been mentioned in terms of isolating uncertainty from risk in real options analysis that we consider here.
Transiciones a la Vida Adulta en Países en Desarrollo
Authors: Juárez Fatima , Gayet Cecilia
Published: July 2014

El estudio sobre las transiciones a la vida adulta que realizan los jóvenes en países en desarrollo amerita una revisión por los nuevos acontecimientos que afectan los distintos ámbitos de la vida. Los cambios recientes en los mercados laborales con altas tasas de desocupación, las nuevas vulnerabilidades de la salud, las modificaciones en las preferencias sobre las formas de unión, en un marco de situaciones de pobreza, manifiestan un mundo con menos certidumbres que deriva en nuevas maneras de experimentar el paso a la adultez. El objetivo del artículo es realizar una revisión de la literatura reciente sobre la interacción entre escolaridad y mundo del trabajo, sexualidad y formación familiar, estado de salud, y expresión política y ciudadanía de los adolescentes y jóvenes de paíes en desarrollo. Se ha encontrado que existe una gran diversificación de trayectorias y las transiciones ocurren en diferentes edades y modalidades en una misma sociedad.
FOXO1 activates glutamine synthetase gene in mouse skeletal muscles through a region downstream of 3′-UTR: possible contribution to ammonia detoxification
Authors: Kamei Yasutomi , Hattori Maki , Hatazawa Yukino , Kasahara Tomomi , Kanou Masanobu , Kanai Sayaka , Yuan Xunmei , Suganami Takayoshi , Lamers Wouter H. , Kitamura Tadahiro , Ogawa Yoshihiro
Published: July 2014

Skeletal muscle is a reservoir of energy in the form of protein, which is degraded under catabolic conditions, resulting in the formation of amino acids and ammonia as a byproduct. The expression of FOXO1, a forkhead-type transcription factor, increases during starvation and exercise. In agreement, transgenic FOXO1-Tg mice that overexpress FOXO1 in skeletal muscle exhibit muscle atrophy. The aim of this study was to examine the role of FOXO1 in amino acid metabolism. The mRNA and protein expressions of glutamine synthetase (GS) were increased in skeletal muscle of FOXO1-Tg mice. Fasting induced FOXO1 and GS expression in wild-type mice but hardly increased GS expression in muscle-specific FOXO1 knockout (FOXO1-KO) mice. Activation of FOXO1 also increased GS mRNA and protein expression in C2C12myoblasts. Using a transient transfection reporter assay, we observed that FOXO1 activated the GS reporter construct. Mutation of a putative FOXO1-binding consensus sequence in the downstream genomic region of GS decreased basal and FOXO1-dependent reporter activity significantly. A chromatin immunoprecipitation assay showed that FOXO1 was recruited to the 3′ region of GS in C2C12myoblasts. These results suggest that FOXO1 directly upregulates GS expression. GS is considered to mediate ammonia clearance in skeletal muscle. In agreement, an intravenous ammonia challenge increased blood ammonia concentrations to a twofold higher level in FOXO1-KO than in wild-type mice, demonstrating that the capacity for ammonia disposal correlated inversely with the expression of GS in muscle. These data indicate that FOXO1 plays a role in amino acid metabolism during protein degradation in skeletal muscle.
Testosterone alters iron metabolism and stimulates red blood cell production independently of dihydrotestosterone
Authors: Beggs Luke A. , Yarrow Joshua F. , Conover Christine F. , Meuleman John R. , Beck Darren T. , Morrow Matthew , Zou Baiming , Shuster Jonathan J. , Borst Stephen E.
Published: July 2014

Testosterone (T) stimulates erythropoiesis and regulates iron homeostasis. However, it remains unknown whether the (type II) 5α-reduction of T to dihydrotestosterone (DHT) mediates these androgenic effects, as it does in some other tissues. Our purpose was to determine whether inhibition of type II 5α-reductase (via finasteride) alters red blood cell (RBC) production and serum markers of iron homeostasis subsequent to testosterone-enanthate (TE) administration in older hypogonadal men. Sixty men aged ≥60 yr with serum T <300 ng/dl or bioavailable T <70 ng/dl received treatment with TE (125 mg/wk) vs. vehicle paired with finasteride (5 mg/day) vs. placebo using a 2 × 2 factorial design. Over the course of 12 mo, TE increased RBC count 9%, hematocrit 4%, and hemoglobin 8% while suppressing serum hepcidin 57% ( P < 0.001 for all measurements). Most of the aforementioned changes occurred in the first 3 mo of treatment, and finasteride coadministration did not significantly alter any of these effects. TE also reduced serum ferritin 32% ( P = 0.002) within 3 mo of treatment initiation without altering iron, transferrin, or transferrin saturation. We conclude that TE stimulates erythropoiesis and alters iron homeostasis independently of the type II 5α-reductase enzyme. These results demonstrate that elevated DHT is not required for androgen-mediated erythropoiesis or for alterations in iron homeostasis that would appear to support iron incorporation into RBCs.
TLR7 Promotes Tumor Progression, Chemotherapy Resistance, and Poor Clinical Outcomes in Non–Small Cell Lung Cancer
Authors: Chatterjee Saradiya , Crozet Lucile , Damotte Diane , Iribarren Kristina , Schramm Catherine , Alifano Marco , Lupo Audrey , Cherfils-Vicini Julien , Goc Jeremy , Katsahian Sandrine , Younes Mohammad , Dieu-Nosjean Marie Caroline , Fridman Wolf Herman , Sautès-Fridman Catherine , Cremer Isabelle
Published: July 2014

Toll-like receptors (TLR) recognize pathogen molecules and danger-associated signals that stimulate inflammatory processes. TLRs have been studied mainly in antigen-presenting cells, where they exert important immune regulatory functions, but they are also expressed by epithelial tumor cells, where they have been implicated in tumor progression. In this study, we demonstrate that the injection of TLR7 agonist in NOD/SCID mice, in C57BL/6 wild-type, and TLR7-deficient mice grafted with lung adenocarcinoma tumor cells leads to increased tumor progression and chemotherapeutic resistance. In patients with non–small cell lung cancer, expression analyses revealed that high TLR7 expression was strongly associated with resistance to neoadjuvant chemotherapy and poor clinical outcomes. Our findings delineate a crucial role for TLR7 in lung cancer physiopathology. Cancer Res; 74(18); 5008–18. ©2014 AACR.
Molecular Pathways: Not a Simple Tube—The Many Functions of Blood Vessels
Authors: Orr Brent A. , Eberhart Charles G.
Published: July 2014

Although the ability of blood vessels to carry fluid and cells through neoplastic tissue is clearly important, other functions of vascular elements that drive tumor growth and progression are increasingly being recognized. Vessels can provide physical support and help regulate the stromal microenvironment within tumors, form niches for tumor-associated stem cells, serve as avenues for local tumor spread, and promote relative immune privilege. Understanding the molecular drivers of these phenotypes will be critical if we are to therapeutically target their protumorigenic effects. The potential for neoplastic cells to transdifferentiate into vascular and perivascular elements also needs to be better understood, as it has the potential to complicate such therapies. In this review, we provide a brief overview of these less conventional vascular functions in tumors. Clin Cancer Res; 21(1); 18–23. ©2014 AACR.
Successful Management of Twin Anemia/Polycythemia Sequence by Syngeneic Partial Exchange Transfusion
Authors: Yarci Erbu , Alyamac Dizdar Evrim , Oncel Mehmet Yekta , Kose Cetinkaya Aslihan , Derme Turan , Canpolat Fuat Emre , Oguz Serife Suna , Dilmen Ugur
Published: July 2014

Twin anemia/polycythemia sequence (TAPS) is characterized by large intertwin hemoglobin (Hb) differences without signs of twin oligopolyhydramnios. The spontaneous form complicates approximately 3-5% of monochorionic twin pregnancies. TAPS placentas are characterized by the presence of only very few and small unidirectional arteriovenous anastomoses, which allow a slow transfusion of blood from the donor to the recipient, gradually leading to highly discordant Hb levels. Neonatal morbidity in TAPS appears to be mainly limited to hematological problems at birth. Donor twins may be severely anemic and require blood transfusions, whereas recipient twins may be severely polycythemic and require partial exchange transfusion (PET). We herein report monochorionic twins with TAPS: the anemic twin was transfused with the blood concomitantly obtained from the polycythemic co-twin during PET. To our knowledge this is the first therapeutic approach using a recipient twin's whole blood as a donor source instead of a foreign blood donor. In this case, we have approached this recently (un)known form of chronic fetofetal transfusion from a different aspect. In our opinion, this will lead to new postnatal therapeutic approaches for optimal TAPS management.
Bilateral Hypertensive Retinopathy Complicated with Retinal Neovascularization: Panretinal Photocoagulation or Intravitreal Anti-VEGF Treatment
Authors: Georgiadis Odysseas , Kabanarou Stamatina A. , Batsos Georgios , Feretis Elias , Xirou Tina
Published: July 2014

Purpose: To present the case of a patient with bilateral hypertensive retinopathy complicated with retinal neovascularization who received anti-VEGF intravitreal injection in one eye and panretinal photocoagulation (PRP) in the fellow eye. Methods: A 33-year-old male patient presented with gradual visual loss in both eyes for the last 5 months. At that time, he was examined by an ophthalmologist and occlusive retinopathy due to malignant systematic hypertension was diagnosed. He was put on antihypertensive treatment but no ophthalmic treatment was undertaken. At presentation, 5 months later, best-corrected visual acuity (BCVA) was 0.1 in the right eye (RE) and 0.9 in the left eye (LE). Fundus examination was compatible with hypertensive retinopathy complicated with retinal neovascularization. Fluorescein angiography (FFA) revealed macular ischemia mainly in the RE and large areas of peripheral retinal ischemia and neovascularization with vascular leakage in both eyes. The patient was treated with two anti-VEGF (ranibizumab) injections with 2 months interval in the RE and PRP laser in the LE. Results: Follow-up examination after 12 months showed mild improvement in BCVA, and FFA documented regression of retinal neovascularization in both eyes. Conclusion: Hypertensive retinopathy can be rarely complicated with retinal neovascularization. Treatment with PRP can be undertaken. In our case, the use of an intravitreal anti-VEGF agent seemed to halt its progression satisfactorily.
Pemetrexed for Ovarian Cancer: A Systematic Review of the Published Literature and a Consecutive Series of Patients Treated in a Nonclinical Trial Setting
Authors: Egloff Heidi , Jatoi Aminah
Published: July 2014

Objective: To gain a better understanding of the role of pemetrexed in ovarian cancer patients, we conducted a systematic review of the published literature and evaluated a consecutive, single-institution series of non-study pemetrexed-treated patients. Methods/Results: Thirteen published articles met this study's eligibility criteria, providing a total of 376 unique and evaluable ovarian cancer patients. This systematic review demonstrated tumor response rates with pemetrexed-based chemotherapy from 9 to 84%; the agent appeared to be well tolerated. Similarly, 13 consecutive patients with ovarian, fallopian tube, or primary peritoneal cancer were treated with pemetrexed at the Mayo Clinic, Rochester, Minn., USA, from 2004 through 2013. The median number of previous chemotherapy regimens was 4; most patients received single-agent pemetrexed (n = 9). Patients received a median of 2 cycles of pemetrexed-based chemotherapy; 1 patient received 10 cycles (7 months' worth) with treatment ongoing at the time of this report. The median survival from the start of pemetrexed was 4.8 months (95% confidence interval 1.2, 15 months). Two patients manifested a 50% drop in Ca-125 levels. Again, pemetrexed was relatively well tolerated. Conclusion: Pemetrexed has antineoplastic activity in patients with ovarian cancer - even among those who have been heavily pretreated - and therefore merits further study.
Atypical Manifestation of Conjunctival Epithelial Inclusion Cyst: A Case Report
Authors: Kim Dong Hyun , Khwarg Sang In , Oh Joo Youn
Published: July 2014

Purpose: To report a case of primary conjunctival epithelial inclusion cyst with atypical manifestation. Methods: A 66-year-old woman presented with a yellowish, subconjunctival mass extending from the corneal limbus to the medial canthus in the left eye. Clinical, radiological and histological assays were performed. Results: The mass was well-delineated, and the overlying conjunctiva was normal. An enhanced axial orbit computed tomography scan showed a 7.7 × 3.6 mm, well-demarcated, convex-shaped enhanced mass. Neither a connection to the orbital area nor extrusion of intraconal fat was observed. Histological examination revealed that the lesion was a cystic mass that was lined by nonkeratinized, stratified squamous epithelium, and filled with mucous materials and cellular debris. The histologic diagnosis was consistent with conjunctival epithelial inclusion cyst. Conclusion: A careful examination using clinical, radiologic and histological studies is essential for the differential diagnosis of subconjunctival mass.