bluuebunny/crossref_metadata_2025 huggingface dataset:
Transfusion‐associated circulatory overload
Authors: Popovsky M. A.
Published: April 2008

Transfusion‐associated circulatory overload (TACO) is cardiogenic pulmonary oedema due to infusion of rapid or large volume blood product. TACO is a frequent, serious, but under‐recognized complication of haemotherapy. Presenting symptoms include dyspnoea, cyanosis, tachycardia and increased blood pressure. Pedal oedema, headache, chest tightness and dry cough are additional manifestations. Chest radiographs reveal pulmonary oedema and cardiomegaly. Vulnerable patients are the very young and persons over 60 years. While rapid infusion or massive transfusion are frequently the precipitating factors, relatively small volumes (1–2 units) are sufficient to trigger the congestive heart failure. Both haeme and non‐haeme fluids account for the positive fluid balance. Fresh‐frozen plasma (FFP) and autologous red blood cells have been implicated as well. Consequences include longer length of intensive care unit and hospital stay. The fatality rate has been reported to be 1–3%, but this may understate the true rate. The incidence has been reported to be 1–8% in orthopaedic surgical populations. In general hospital populations a range of 1 : 708–1 : 4075 red blood cell transfusions is associated with TACO. In the intensive care setting, an incidence of 1 : 356 components has been demonstrated. TACO is frequently confused with transfusion‐related acute lung injury (TRALI). In some cases, TRALI and TACO may co‐exist. A potentially important diagnostic tool is brain natriuretic peptide. Brain natriuretic peptide is elevated in TACO and a post‐transfusion‐to‐pre‐transfusion ratio of 1·5 is indicative of the diagnosis. The test has a sensitivity of 81% and a specificity of 89%. Treatment includes supplementary oxygen, diuretics, placing the patient in a sitting position and therapeutic phlebotomy in 250‐ml increments. While rapid infusion is believed to be a contributing factor, optimal infusion rates for the non‐emergency situation have not been determined. TACO has been observed with flow rates between 0·9 and 48·1 ml/min. Preventive measures include use of evidence‐based transfusion and controlled‐rate infusion. Measures that insure the use of standardized blood components, such as derived through apheresis, are likely to favourably impact the incidence of this complication.
Levels of quality management of blood transfusion services in Europe
Authors: Seidl C. , Brixner V. , Müller‐Kuller T. , Sireis W. , Costello P. , Cermakova Z. , Delaney F. , Douglas A. M. , Nightingale M. , Van Galen J. P. , O’Connell M. , Siegel W. , Sobaga L. , De Wit J. , Seifried E.
Published: April 2008

The European blood legislation has defined several key quality elements to achieve Good Manufacturing Practice (GMP) in the field of blood transfusion. During the recent years, the blood legislation is in the process of implementation throughout its member states. Following the Directive 2002/98/EC, Directive 2005/62/EC has given further requirements for quality‐management systems to be fulfilled by blood establishments. In addition, GMP/Good Laboratory Practice (GLP) and ISO standards are used inter alia by blood establishments. In order to support the implementation of the blood legislation, the European Public Health Work Plan (2005/2007) has cofunded two projects, led by the German Red Cross and supported by the European Blood Alliance, delivering a common European Standard Operating Procedure (SOP) methodology (EU‐Q‐Blood‐SOP) and criteria and standards for the inspection of blood establishments (EUBIS). The EU‐SOP manual will assist blood establishments in preparing for the inspection of their services related to the implementation of quality relevant elements required by the EU Directive 2002/98/EC and its technical annexes. The standards and criteria for inspection of blood establishments will cross‐reference existing quality standards to the directive requirements and define requirements for the structure of quality‐management systems based on the directive 2002/98/EC and its technical annexes. Based on these requirements, inspection standards and criteria are developed to assist in the independent assessment of quality systems established by individual blood establishments. These assessments are done in relation to the requirements defined by the European Union legislation on blood, in order to safeguard the quality of blood and to achieve continuous improvement of its quality throughout Europe.
Dysthymia in male adolescents is associated with increased risk of later hospitalization for psychotic disorders: a historical‐prospective cohort study
Authors: Weiser Mark , Lubin Gad , Caspi Asaf , Rabinowitz Jonathan , Shmushkevitz Mordechai , Yoffe Rinat , Werbeloff Nomi , Halperin Demian , Davidson Michael
Published: April 2008

Aim: Retrospective studies indicate that patients with psychotic disorders and schizophrenia often suffer from depressive symptoms before the onset of psychosis. In a historical‐prospective design, we studied the association between dysthymia in adolescence and later hospitalization for psychotic disorders and schizophrenia.

Methods: The Israeli Draft Board screens the entire, unselected population of 16–17 years old male adolescents for psychiatric disorders. These adolescents were followed for hospitalization for psychotic disorders and schizophrenia using the Israeli National Psychiatric Hospitalization Case Registry. Of 275 705 male adolescents screened, 1267 (0.5%) were hospitalized for psychotic disorders (International Classification of Diseases [ICD]‐10 20.0–29.9), and 757 (0.3%) were hospitalized for schizophrenia (ICD‐10 20.0–20.9) over the next 1–10 years.

Results: Of 275 705 male adolescents screened, 513 (0.2%) were diagnosed as suffering from dysthymia by the Draft Board. Of these adolescents, 10/513 (2.0%) were later hospitalized for psychotic disorders (including schizophrenia, HR = 3.967, 95%CI (confidence intervals): 2.129–7.390), and 4/513 (0.8%) were later hospitalized for schizophrenia (HR = 2.664, 95%CI: 0.997–7.116).

Conclusions: In this population‐based cohort of male adolescents, dysthymia was associated with increased risk for future psychotic disorders. Dysthymia in some adolescents might be a prodromal symptom, while in others it might be a risk factor for later psychosis. Clinicians assessing dysthymic adolescents should be aware that these symptoms might be part of the prodrome.
Positive schizotypy is not associated with speech abnormality
Authors: Weinstein Sara , McKay Rachel , Ngan Elton T.
Published: April 2008

Aim: This study examined whether speech abnormalities typical of formal thought disorder in schizophrenia vary with the degree of positive schizotypy in the healthy population. We hypothesized that participants with high levels of positive schizotypy would show greater abnormality in speech relative to those with low levels of positive schizotypy.

Methods: Participants (n = 107) were prescreened with a positive schizotypy scale. Those meeting criteria for either high (n = 23) or low (n = 27) schizotypy provided speech samples which were assessed with a clinical though disorder rating scale (Thought and Language Index) for the presence of abnormality.

Results: No significant differences were found in positive (P = 0.25) or negative (P = 0.21) speech abnormality between the high and low schizotypy groups.

Conclusion: Although schizotypy is normally distributed in the general population, speech abnormality is not. Thus, the presence of aberrations in speech may predict risk of psychosis. Potential implications for risk assessment are discussed.
Integrating primary care and early intervention in psychosis services: a general practitioner perspective
Authors: Gavin Blanaid , Cullen Walter , Foley Sharon , McWilliams Stephen , Turner Niall , O'Callaghan Eadbhard , Bury Gerard
Published: April 2008

Aims: Earlier detection and treatment of psychosis is associated with improved health outcomes. While the role of specialist services to facilitate early diagnosis and treatment has been extensively described internationally, little data on their impact on general practice has been reported. A new specialist service for psychosis – the ‘Dublin East Treatment and Early Care Team (DETECT)’– has recently been established. This study aimed to describe general practitioners' (GPs) attitudes towards working within the catchment area of an early intervention service.

Methods: A purposive sample of GPs practising in DETECT's catchment area was identified from the Irish Medical Directory and invited to participate in a semi‐structured interview. The sampling parameters were solo/practice and area of practice. Participants were provided with information regarding the new service and a range of educational material. Each interview was reviewed by two researchers who identified dominant themes. The study was approved by the Research Ethics Committee of the Irish College of GPs.

Results: 16 GPs were interviewed. The DETECT early intervention model was identified as reducing the challenges of managing psychosis in primary care including the practical difficulties of accessing psychiatric assessment and the pervasive effect of stigma. Participants viewed communication between primary and specialist care as essential to the success of early intervention services.

Conclusions: General Practice has an important role in early detection of psychosis and accessing timely psychiatric evaluations of suspected psychosis. Increasing awareness among GPs and ensuring the early intervention model is responsive to primary care can support this role.
The radioprotective properties of fungal melanin are a function of its chemical composition, stable radical presence and spatial arrangement
Authors: Dadachova Ekaterina , Bryan Ruth A. , Howell Robertha C. , Schweitzer Andrew D. , Aisen Philip , Nosanchuk Joshua D. , Casadevall Arturo
Published: April 2008

Melanized microorganisms are often found in environments with very high background radiation levels such as in nuclear reactor cooling pools and the destroyed reactor in Chernobyl. These findings and the laboratory observations of the resistance of melanized fungi to ionizing radiation suggest a role for this pigment in radioprotection. We hypothesized that the radioprotective properties of melanin in microorganisms result from a combination of physical shielding and quenching of cytotoxic free radicals. We have investigated the radioprotective properties of melanin by subjecting the human pathogenic fungi Cryptococcus neoformans and Histoplasma capsulatum in their melanized and non‐melanized forms to sublethal and lethal doses of radiation of up to 8 kGy. The contribution of chemical composition, free radical presence, spatial arrangement, and Compton scattering to the radioprotective properties of melanin was investigated by high‐performance liquid chromatography, electron spin resonance, transmission electron microscopy, and autoradiographic techniques. Melanin protected fungi against ionizing radiation and its radioprotective properties were a function of its chemical composition, free radical quenching, and spherical spatial arrangement.
GRADUATE UNEMPLOYMENT IN THE FACE OF SKILLS SHORTAGES: A LABOUR MARKET PARADOX1
Authors: Pauw K. , Oosthuizen M. , Van Der Westhuizen C.
Published: April 2008

Analysts agree that South Africa's unemployment is structural in the sense that the unemployed generally possess lower skills than what is required by the economy. In the context of increasing demand for skilled workers due to technological changes and the need to become globally more competitive, graduates would be expected to find employment without difficulty. However, against expectations unemployment has been increasing among young people with tertiary qualifications since 1995. This paper investigates the nature of this phenomenon. Evidence suggests that learners are inadequately prepared for both tertiary studies and entry into the labour market. Lack of, or inadequate career guidance means that they do not choose fields of study and types of qualifications with good employment prospects. In addition, lack of soft skills and workplace experience mean that employers are reluctant to employ graduates, preferring more experienced people instead.
REVISITING INFORMAL EMPLOYMENT AND SEGMENTATION IN THE SOUTH AFRICAN LABOUR MARKET
Authors: Heintz James , Posel Dorrit
Published: April 2008

This study revisits the definition of informal employment, and it investigates the puzzle of high open unemployment co‐existing with relatively limited informal employment in South Africa. We estimate earnings equations using data from the September 2004 Labour Force Survey and present evidence of persistent earnings differentials not only between formal and informal employment, but also between types of informal employment. These persistent earnings differentials are suggestive of complex segmentation in the South African labour market and challenge the presentation of informal employment as an undifferentiated residual with no barriers to entry or mobility.
HURDLE MODELS OF ALCOHOL AND TOBACCO EXPENDITURE IN SOUTH AFRICAN HOUSEHOLDS1
Authors: Ground Marc , Koch Steven F
Published: April 2008

Estimates of participation or expenditure elasticities depend upon the assumptions made regarding the observation of zero expenditure at the household level. This research examines two single‐hurdle models across two commodities for which nearly two‐thirds of the observations are zero. The research shows that one hurdle model consistently outperforms the other, and does so for intuitively appealing reasons.
What is your diagnosis? Pleural fluid from a neonatal Thoroughbred filly with pneumonia
Authors: Stokol Tracy , Gold Jenifer , Johnson Amy , Ainsworth Dorothy
Published: April 2008

Abstract:A 3‐day‐old filly was presented to the Cornell University Hospital for Animals with an umbilical hematoma and mild aspiration pneumonia. The foal underwent abdominal surgery for resection of the hematoma. Recovery was uneventful, but 3 days after surgery, the foal became progressively tachypneic. Imaging studies revealed bilateral pleural effusion and pleuropneumonia. Cytologic evaluation and bacterial culture of the pleural fluid from both sides of the chest revealed sterile exudates, consisting mostly of neutrophils, with fewer macrophages and lymphocytes. Pleural fluid macrophages contained variable amounts of purple–magenta globular material in their cytoplasm. A lighter colored granular precipitate was also seen throughout the background of the smears. Similar material was identified in a macrophage in a peripheral blood smear prepared 2 days after abdominal surgery. Large amounts of extracellular pink precipitate were also seen in the blood smear and persisted in the blood for 7 days after surgery. A protective lubricant, carboxymethylcellulose, had been instilled into the abdominal cavity during surgery to prevent intra‐abdominal adhesions. The intracytoplasmic pigment within pleural fluid and blood macrophages and the extracellular precipitate in peripheral blood and pleural fluid smears was compatible with carboxymethylcellulose. The material was probably derived hematogenously and was considered an incidental finding. The pleuritis was attributed to exacerbation of the original aspiration pneumonia by the general anesthesia.
Optimal Design of Current Takeoff in Bus Bars for Tubular Solid Oxide Fuel Cells
Authors: DiGiuseppe Gianfranco , Draper Robert
Published: April 2008

The technology of tubular solid oxide fuel cells of cylindrical geometry has advanced enough such that several demonstration units are currently being tested. This paper presents a simple analytical model for the determination of the current density as a function of axial active cell length under idealized conditions. In addition, a current density axial profile under generator conditions obtained from modeling work is used and compared to the simpler approach. The resulting current density axial profiles are then used to design current takeoff in bus bars where the losses in the power leads are minimized. The result is an optimal scenario where bus bars can be considered to be surfaces that do not significantly affect the natural current density of the solid oxide fuel cell.
Diesel Steam Reforming for PEM Fuel Cells
Authors: Mengel Christian , Konrad Martin , Wruck Roland , Lucka Klaus , Köhne Heinrich
Published: April 2008

Different applications for the decentralized stationary or mobile power supply require the usage of liquid hydrocarbons such as fuel oil, diesel, or gas oil in fuel cell systems. Reducing the sulfur content of conventional liquid fuels such as diesel or gasoline below 10ppm, the usage of these fuels in fuel cell applications becomes increasingly promising. The first process step represents thereby the reforming, which can be carried out in different ways. One of the commonly favored gas process technologies is the steam reforming process, which is state of the art for natural gas applications. Using a proton exchange membrane (PEM) fuel cell requires a complex gas cleanup system. Using a pressurized steam reforming process offers a significant reduction of the whole system size by efficiently compressing the liquid educts. Complete PEM systems with steam reformers tend to have a higher efficiency than, for example, systems using the autothermal reforming process. Advanced diesel steam reformers for industrialization still have to be developed and improved. The Oel-Wärme-Institut gGmbH has successfully carried out research on steam reforming with variations of important parameters using a sulfur free reference fuel and desulfurized diesel. During the experiments, several parameters such as steam to carbon ratio, reformer inlet temperatures, catalysts, and fuels were varied. While running the process, a continuous product gas measurement was taken. The reformer is equipped with several thermocouples. Three of them are moveable to measure the temperature profile of the catalyst. The experiments show that product gas concentrations reach a nearly equilibrium concentration with reformer inlet temperatures ϑ>700°C of a reference fuel∕steam mixture. Hydrogen concentrations over 70% were feasible. Constant inlet temperatures of ϑ=850°C and a variation of the steam to carbon ratio only have a noticeable effect on the water gas shift equilibrium. After all experiments, carbon deposits were found in the steam reformer system and under some circumstances on the catalysts. Experiments with operating times of more than 20h were performed at a steam to carbon ratio of 4.5. The application of continuously desulfurized diesel fuel indicates a degradation of the catalyst after a few hours. For the overall system design of PEM fuel cell applications, an operation mode at a reduced steam to carbon ratio has to be developed.
Numerical Determination of Two-Phase Material Parameters of a Gas Diffusion Layer Using Tomography Images
Authors: Becker Jürgen , Schulz Volker , Wiegmann Andreas
Published: April 2008

In this paper, we give a complete description of the process of determining two-phase material parameters for a gas diffusion layer: Starting from a 3D tomography image of the gas diffusion layer the distribution of gas and water phases is determined using the pore morphology method. Using these 3D phase distributions, we are able to determine permeability, diffusivity, and heat conductivity as a function of the saturation of the porous medium with comparatively low numerical costs. Using a reduced model for the compression of the gas diffusion layer, the influence of the compression on the parameter values is studied.
Parametric Sensitivity Analysis of Fast Load Changes of a Dynamic MCFC Model
Authors: Sternberg K. , Chudej K. , Pesch H. J. , Rund A.
Published: April 2008

Molten carbonate fuel cells are well suited for stationary power production and heat supply. In order to enhance service lifetime, hot spots, respectively, high temperature gradients inside the fuel cell have to be avoided. In conflict with that, there is the desire to achieve faster load changes while temperature gradients stay small. For the first time, optimal fast load changes have been computed numerically, including a parametric sensitivity analysis, based on a mathematical model of Heidebrecht. The mathematical model allows for the calculation of the dynamical behavior of molar fractions, molar flow densities, temperatures in gas phases, temperature in solid phase, cell voltage, and current density distribution. The dimensionless model is based on the description of physical phenomena. The numerical procedure is based on a method of line approach via spatial discretization and the solution of the resulting very large scale optimal control problem by a nonlinear programming approach.
Fabrication and Characterization of Anode-Supported Planar Solid Oxide Fuel Cell Manufactured by a Tape Casting Process
Authors: Song Jung-Hoon , Sammes Nigel M. , Park Sun-Il , Boo Seongjae , Kim Ho-Sung , Moon Hwan , Hyun Sang-Hoon
Published: April 2008

A planar anode-supported electrolyte was fabricated using a tape casting method that involved a single step cofiring process. A standard NiO∕8YSZ cermet anode, 8mol% YSZ electrolyte, and a lanthanum strontium manganite cathode were used for the solid oxide fuel cell unit cell. A pressurized cofiring technique allows the creation of a thin layer of dense electrolyte about 10μm without warpage. The open circuit voltage of the unit cell indicated negligible fuel leakage through the electrolyte film due to the dense and crack-free electrolyte layer. An electrochemical test of the unit cell showed a maximum power density up to 0.173W∕cm2 at 900°C. Approximated electrochemical properties, e.g., activation energy, Ohmic resistance, and exchange current density, indicated that the cell performance was significantly influenced by the electrode properties of the unit cell.
The Effect of Compressor Rotor Tip Crops on Turboshaft Engine Performance
Authors: Frith P. C.
Published: April 2008

The results from an experimental study into the effect of compressor rotor tip clearance changes on the steady-state performance and stability margins of a free-power turbine turboshaft engine are presented and discussed. This work was directed at the development of methods to diagnose engine condition from gas path measurements. It was found that the normal production suite of engine instrumentation was able to measure the deterioration in engine performance due to the implanted compressor degradation and the resultant deviations in the measured parameters from their respective nominal baselines do provide useful indicators of engine condition.
Tools for Diagnosing Case Deflections and Alignment on a Power Utility Combustion Turbine
Authors: Simmons H. R. , Smalley A. J. , Frischmuth R. W. , Lapini G. , Robinson G.
Published: April 2008

This paper discusses development, installation, and analysis of instrumentation systems for reliably measuring casing, thermal distortion, and alignment deviation on a large combustion turbine in power utility service. A variety of redundant measurement systems were installed to document casing distortion during the cooldown period after firing. The operating principles of each measurement system are described and presented with the rationale developed for installing and locating sensors. A vertical deflection sensor used for casing bow and bearing misalignment measurement is highlighted in the paper to illustrate its potential for use in other investigations. Additional sensors used include an array of shaft proximity probes, blade tip proximity probes, thermocouples, and axial growth probes. A measurement system for casing ovalization was developed using LVDTs mounted from a thermally stabilized ring. An automated data acquisition system was developed and installed to facilitate the recording of turbine cool-down events over the complete operating season without the need for constant on-site attention. Preliminary results define the turbine cylinder bow and ovalization response during the cool-down event following normal unit operation and correlated casing distortions with thermal gradients.
Fatigue Life Estimation Procedure for a Turbine Blade Under Transient Loads
Authors: Vyas N. S. , Rao J. S.
Published: April 2008

Fatigue analysis and consequent life prediction of turbomachine blading requires the stress load history of the blade. A blade designed for safe operation at particular constant rotor speeds may, however, incur damaging stresses during start-up and shut-down operations. During such operations the blade experiences momentary resonant stresses while passing through the criticals, which may lie in the speed range through which the rotor is accelerated. Fatigue due to these transient influences may accumulate to lead to failure. In this paper a technique for fatigue damage assessment during variable-speed operations is presented. Transient resonant stresses for a blade with nonlinear damping have been determined using a numerical procedure. A fatigue damage assessment procedure is described. The fatigue failure surface is generated on the S-N-mean stress axes and Miner’s Rule is employed to estimate the accumulation of fatigue.
A Novel High-Temperature Ejector-Topping Power Cycle
Authors: Freedman B. Z. , Lior N.
Published: April 2008

A novel, patented topping power cycle is described that takes its energy from a very high-temperature heat source and in which the temperature of the heat sink is still high enough to operate another, conventional power cycle. The top temperature heat source is used to evaporate a low saturation pressure liquid, which serves as the driving fluid for compressing the secondary fluid in an ejector. Due to the inherently simple construction of ejectors, they are well suited for operation at temperatures higher than those that can be used with gas turbines. The gases exiting from the ejector transfer heat to the lower temperature cycle, and are separated by condensing the primary fluid. The secondary gas is then used to drive a turbine. For a system using sodium as the primary fluid and helium as the secondary fluid, and using a bottoming Rankine steam cycle, the overall thermal efficiency can be at least 11 percent better than that of conventional steam Rankine cycles.
Structural Evaluation and Testing of Swept Compressor Rotor
Authors: Aksoy S. , Mitlin B. , Borowy H.
Published: April 2008

This paper summarizes specific critical issues encountered in the structural analysis of a swept first-stage compressor blade of a gas turbine engine and the results of the test to evaluate the accuracy of the modeling and surface stress prediction procedure. The surface stresses of a three-dimensional structure were obtained using membrane elements attached to the surface of solid elements. Steady stress measurements were then made during accelerations and decelerations to and from design speed. The test was conducted in an evacuated spin rig. The measurements were used to evaluate the validity of the stress prediction from finite element analysis.
A High-Speed Capacitance-Based System for Gaging Turbomachinery Blading Radius During the Tip Grind Process
Authors: Sheard A. G. , Westerman G. C. , Killeen B. , Fitzpatrick M.
Published: April 2008

During the manufacture and overhaul of gas turbines, it is necessary to ensure that all blades in a stage are of an equal and known length to minimize the loss in performance that arises as a consequence of the clearance between rotor tip and engine casing. Modern compressor and turbine blades are generally loose fitting in their root fixings and only adopt their true working position when running. In this paper, a new technique for measuring the rotor radius over individual blades is described. The measurement technique utilizes a capacitance-based clearance measurement system, which enables rotor radius to be measured over each blade while spinning fast enough to ensure that the blades are centrifugally loaded into their true working position. The measurement technique is described, as is the system utilized to calibrate and reduce output into engineering units. The mechanical design of the “measurement head” is presented and the CNC lathe to which it interfaces described. Finally, the results of an experimental program, utilizing a fully bladed compressor disk undertaken to ascertain system performance, are presented.
The Modular High-Temperature Gas-Cooled Reactor: A Cost/Risk Competitive Nuclear Option
Authors: Gotschall H. L.
Published: April 2008

The business risks of nuclear plant ownership are identified as a constraint on the expanded use of nuclear power. Such risks stem from the exacting demands placed on owner/operator organizations of current plants to demonstrate ongoing compliance with safety regulations and the resulting high costs for operation and maintenance. This paper describes the Modular High-Temperature Gas-Cooled Reactor (MHTGR) design, competitive economics, and approach to reducing the business risks of nuclear plant ownership.
Thermal Barrier Coatings on Turbine Blades by Plasma Spraying With Improved Cooling
Authors: Cosack T. , Pawlowski L. , Schneiderbanger S. , Sturlese S.
Published: April 2008

Turbine blades were coated with a thermal barrier coating system consisting of an MCrAlY bond coat about 100 μm thick deposited by Low-Pressure Plasma Spraying (LPPS) and a 300 μm thick ZrO2-7 wt. % Y2O3 top coat. The latter was manufactured by both Atmosphere and Temperature Controlled Spraying (ATCS) and Air Plasma Spraying (APS) using internal air cooling through the cooling holes of the turbine blades. Coated blades were submitted to thermal cycling tests in a burner rig with hot gas temperature of 1485°C. In the case of ATCS coated blades the number of cycles until the first spallation at the leading edge of the blade was between 350 and 2400. The number of cycles of the thermal barrier coatings sprayed with internal cooling was between 1200 and 1800. Furnace cycling tests were also carried out with ATCS coated blades at temperatures of 1100 and 1200°C. The results of thermal cycle tests and the investigations of the microstructure are discussed.
Infrared Signature Suppression for Marine Gas Turbines: Comparison of Sea Trial and Model Test Results for the DRES Ball IRSS System
Authors: Birk A. M. , VanDam D.
Published: April 2008

Sea Trials have recently been underway for Canada’s new City Class Patrol Frigate (CPF). These trials provided the first opportunity to measure the performance of the new DRES Ball Infrared Signature Suppression (IRSS) system installed on a ship. Prior to these trials 1/4-scale hot flow model test and computer simulation performance results were available. The CPF DRES Ball IRSS systems are installed on the exhaust uptakes of the GE LM2500 main gas turbines. The DRES Ball provides both metal surface cooling for all view angles and plume cooling. The DRES Ball significantly reduces the IR signature of the LM2500 exhaust. This paper presents a comparison between the 1/4-scale hot flow model test results with the full-scale sea trial results. Performance variables included in the comparison are: metal surface temperatures, back pressure, plume temperature distribution, and surface static pressures. Because of the confidential nature of the DRES Ball system performance, all classified data have been nondimensionalized so that only relative comparisons can be made between the full-scale and 1/4-scale data. The results show that the full-scale system performs better than the 1/4-scale model because of Reynolds number effects. The plume temperature, surface temperatures, and back pressure were all lower (better) than in the 1/4-scale model tests. One of the original concerns with the installation was that relative wind would degrade the performance of the DRES Ball onboard a ship. The wind effect was found to be benign during the trials.
Selection Criteria for Plain and Segmented Finned Tubes for Heat Recovery Systems
Authors: Reid D. R. , Taborek J.
Published: April 2008

Heat recovery heat exchangers with gas as one of the streams depend on the use of finned tubes to compensate for the inherently low gas heat transfer coefficient. Standard frequency welded “plain” fins were generally used in the past, until the high-frequency resistance welding technology permitted a cost-effective manufacture of “segmented” fins. The main advantage of this fin design (Fig. 1) is that it permits higher heat flux and hence smaller, lighter weight units for most operating conditions. While the criteria that dictate optimum design, such as compactness, weight, and cost per unit area favor the segmented fin design, a few other considerations such as fouling, ease of cleaning, and availability of dependable design methods have to be considered. This paper analyzes the performance parameters that affect the selection of either fin type.
Accuracy and Efficiency Assessments for a Weak Statement CFD Algorithm for High-Speed Aerodynamics
Authors: Iannelli G. S. , Baker A. J.
Published: April 2008

A bilinear finite element, implicit Runge-Kutta space-time discretization has been established for an aerodynamics weak statement CFD algorithm. The algorithm admits real-gas effect simulation, for reliable hypersonic flow characterization, via an equilibrium reacting air model. The terminal algebraic system is solved using an efficient block-tridiagonal quasi-Newton linear algebra procedure that employs tensor matrix product factorizations within a lexicographic mesh-sweeping protocol. A block solution-adaptive remeshing, for totally arbitrary convex elements, is also utilized to facilitate accurate shock and/or boundary layer flow resolution. Numerical validations are presented for representative benchmark supersonic-hypersonic aerodynamics problem statements.
Nondestructive Eddy Current Evaluation of Anisotropic Conductivities of Silicon Carbide Reinforced Aluminum Metal-Matrix Composite Extrusions
Authors: Liaw P. K. , Pitchumani R. , Hsu D. K. , Jeong H. , Yao S. C.
Published: April 2008

Nondestructive eddy current methods were used to evaluate the electrical conductivity behavior of silicon-carbide particulate (SiCp) reinforced aluminum (Al) metal-matrix composite extrusions. The composites investigated included 2124, 6061, and 7091 Al base alloys reinforced by SiCp. The composite extrusions exhibited anisotropic conductivities with the maximum conductivity occurring along the extrusion plane. Microstructural characterization showed that the observed anisotropic conductivities could result from the preferred orientation distribution of SiCp. A theoretical model was formulated to quantify the influence of composite constituents (SiCp, intermetallics, and Al base alloy) on the anisotropic conductivities of the composites. The theoretical predictions of conductivities were found to be in good agreement with the experimental results.
An Optimum Balance Weight Search Algorithm
Authors: Austrow J. C.
Published: April 2008

A mathematical description for an optimum balance weight search algorithm for single-plane multipoint balance is presented. The algorithm uses influence coefficients, either measured or known beforehand, and measured complex vibration data to determine an optimum balance correction weight. The solution minimizes the maximum residual vibration. The algorithm allows user-defined balance weights to be analyzed and evaluated. A test case is presented showing actual results and comparison with a least-squares solution algorithm. An efficient multiplane influence coefficient calculation scheme is also presented.
Fluid-Thermoacoustic Vibration of a Gas Turbine Recuperator Tubular Heat Exchanger System
Authors: Eisinger F. L.
Published: April 2008

Low-frequency acoustic vibration of a vertical gas turbine recuperator during cold start-up is described. The vibration was identified as fluid-thermoacoustic instability driven by a modified Sondhauss tube-like thermoacoustic phenomenon. The problem and its underlying theoretical basis are described. A design guideline for prevention of instability and alternative solutions for the elimination of the vibration are given.
Balancing of Rotors Supported on Bearings Having Nonlinear Stiffness Characteristics
Authors: Turpin A. , Sharan A. M.
Published: April 2008

In real-life applications, multi-disk-rotor systems are supported on bearings with nonlinear flexibility. The balancing of such systems at high speeds is a challenging task. This work presents a method of balancing such systems. The dynamic equations of motion for a nonlinear system are derived first using the influence coefficient method and then Lagrangian equations. An equivalent linear system is found using the optimization principles. Finally, the correct balance weights for the nonlinear system are obtained based on the equivalent linear system. The results thus obtained establish the utility of such a method of balancing nonlinear systems.
Analysis of the Injection Process in Direct Injected Natural Gas Engines: Part I—Study of Unconfined and In-Cylinder Plume Behavior
Authors: Jennings M. J. , Jeske F. R.
Published: April 2008

A study of natural gas (NG) direct injection (DI) processes has been performed using multidimensional computational fluid dynamics analysis. The purpose was to improve the understanding of mixing in DI NG engines. Calculations of injection into a constant-volume chamber were performed to document unconfined plume behavior. A full three-dimensional calculation of injection into a medium heavy-duty diesel engine cylinder was also performed to study plume behavior in engine geometries. The structure of the NG plume is characterized by a core of unmixed fuel confined to the near-field of the jet. This core contains the bulk of the unmixed fuel and is mixed by the turbulence generated by the jet shear layer. The NG plume development in the engine is dominated by combustion chamber surface interactions. A Coanda effect causes plume attachment to the cylinder head, which has a detrimental impact on mixing. Unconfined plume calculations with different nozzle hole sizes demonstrate that smaller nozzle holes are more effective at mixing the fuel and air.
Analysis of the Injection Process in Direct Injected Natural Gas Engines: Part II—Effects of Injector and Combustion Chamber Design
Authors: Jennings M. J. , Jeske F. R.
Published: April 2008

A study of natural gas (NG) direct injection (DI) processes in engines has been performed using multidimensional computational fluid dynamics analysis. The purpose was to investigate the effects of key engine design parameters on the mixing in DI NG engines. Full three-dimensional calculations of injection into a medium heavy-duty diesel engine cylinder were performed. Perturbations on a baseline engine configuration were considered. In spite of single plume axisymmetric injection calculations that show mixing improves as nozzle hole size is reduced: plume merging caused by having too many nozzle holes has a severe negative impact on mixing; and increasing the number of injector holes strengthens plume deflection toward the cylinder head, which also adversely affects mixing. The optimal number of holes for a quiescent engine was found to be that which produces the largest number of separate NG plumes. Increasing the nozzle angle to reduce plume deflection can adversely affect mixing due to reduced jet radial penetration. Increasing the injector tip height is an effective approach to eliminating plume deflection and improving mixing. Extremely high-velocity squish flows, with penetration to the center of the piston bowl, are necessary to have a significant impact on mixing. Possible improvements in mixing can be realized by relieving the center of the piston bowl in typical “Mexican hat” bowl designs. CFD analysis can effectively be used to optimize combustion chamber geometry by fitting the geometry to computed plume shapes.
Numerical Analysis Versus Experimental Investigation of a Distributor-Type Diesel Fuel-Injection System
Authors: Catania A. E. , Dongiovanni C. , Mittica A. , Badami M. , Lovisolo F.
Published: April 2008

A production distributor-type fuel-injection system for diesel engines has been extensively investigated via computer-assisted simulation and experimentation. The investigation was mainly aimed at assessing and validating a sophisticated computational model of the system, developed with specific attention given to the pump and to some important aspects concerning the injection pressure simulation, such as the dynamic effects of the injector needle lift, the flow unsteadiness, and compressibility effects on the nozzle-hole discharge coefficient. The pump delivery assembly was provided with a valve of the reflux type. This presented a flat in the collar, forming a return-flow restriction with the seat, and had no retraction piston. A single-spring injector, with a reduced sac volume, was fitted to the system. The numerical analysis of transient flow phenomena linked to the mechanical unit dynamics, including possible cavitation occurrence in the system, was performed using an implicit finite-difference algorithm, previously set up for in-line injection equipment. Particular care was exercised in modeling the distributor pump so as to match the dynamics of the delivery-valve assembly to the pressure wave propagation in the distributor and its outlets. The so-called minor losses were also taken into account and it was ascertained that sudden expansion and contraction losses were significant for the type of pump examined. The experimental investigation was performed on a test bench at practical pump speeds. Pressures were measured in the pumping chamber, at two different pipe locations, and upstream to the needle seat opening passage. This last measurement was taken in order to evaluate the nozzle-hole flow coefficient with the support of the simulation, using experimental values of the needle lift, injection rate, and injected fuel quantity as known variables. The numerical and experimental results were compared and discussed, showing the validity of the model. The injection pressure time history and the influence of the delivery return-flow restriction on the system performance were numerically examined.
High Levels of Zidovudine (AZT) and Its Intracellular Phosphate Metabolites in AZT- and AZT-Lamivudine-Treated Newborns of Human Immunodeficiency Virus-Infected Mothers
Authors: Durand-Gasselin Lucie , Pruvost Alain , Dehée Axelle , Vaudre Genevieve , Tabone Marie-Dominique , Grassi Jacques , Leverger Guy , Garbarg-Chenon Antoine , Bénech Henri , Dollfus Catherine
Published: April 2008

Newborns from human immunodeficiency virus-infected mothers are given antiretroviral prophylaxis against mother-to-child transmission, including predominantly nucleoside reverse transcriptase inhibitors. Pharmacological monitoring of these drugs in newborns has so far been limited to plasma and cord blood. In this study, samples from newborns (up to 45 days old) treated with zidovudine (AZT) alone (n= 29) or in combination with lamivudine (3TC) (n= 20) were analyzed for both intracellular concentrations of phosphate metabolites in peripheral blood mononuclear cells and levels of parent drugs in plasma. Plasma AZT and intracellular AZT-monophosphate and AZT-triphosphate (TP) concentrations were significantly higher during the first 15 days of life (199 versus 52.7 ng/ml [P< 0.0001], 732 versus 282 fmol/106cells [P< 0.0001], and 170 versus 65.1 fmol/106cells [P< 0.0001], respectively) and then became comparable to those of adults. No difference in intracellular AZT metabolite concentrations was found when AZT- and AZT-3TC-treated groups were compared. Plasma 3TC levels (lower limit of quantification [LLOQ], 1,157 ng/ml; median, 412.5 ng/ml) were not associated with the newborn's age, gender, or weight. Intracellular 3TC-TP concentrations (LLOQ, 40.4 pmol/106cells; median, 18.9 pmol/106cells) determined for newborns receiving the AZT-3TC combination were associated with neither the age nor weight of the newborns. Concentrations in females were significantly higher (1.8-fold [P= 0.0415]) than those in males. Unexpectedly, newborns on AZT monotherapy whose mothers' treatment included 3TC displayed residual plasma 3TC and intracellular 3TC-TP levels up to 1 week after birth.
Mutagenesis in the α3α4 GyrA Helix and in the Toprim Domain of GyrB Refines the Contribution of
Mycobacterium tuberculosis
DNA Gyrase to Intrinsic Resistance to Quinolones
Authors: Matrat Stéphanie , Aubry Alexandra , Mayer Claudine , Jarlier Vincent , Cambau Emmanuelle
Published: April 2008

The replacement of M74 in GyrA, A83 in GyrA, and R447 in GyrB of
Mycobacterium tuberculosis
gyrase by their
Escherichia coli
homologs resulted in active enzymes as quinolone susceptible as the
E. coli
gyrase. This demonstrates that the primary structure of gyrase determines intrinsic quinolone resistance and was supported by a three-dimensional model of N-terminal GyrA.
Characterization of the Ers Regulon of
Enterococcus faecalis
Authors: Riboulet-Bisson Eliette , Sanguinetti Maurizio , Budin-Verneuil Aurélie , Auffray Yanick , Hartke Axel , Giard Jean-Christophe
Published: April 2008

Ers has been qualified as the PrfA-like transcriptional regulator of
Enterococcus faecalis
. In a previous study we reported that Ers is important for the survival within macrophages of this opportunist pathogenic bacterium. In the present work we have used proteomic and microarray expression profiling of
E. faecalis
JH2-2 and an
ers
-deleted mutant (Δ
ers
mutant) strains to define the Ers regulon. In addition to EF_0082 (encoding a putative facilitator family transporter), already known to be under Ers regulation, three genes or operons displayed a significant decrease (confirmed by reverse transcription quantitative PCR) in expression in the Δ
ers
mutant. The first locus corresponds to three genes:
arcA
,
arcB
, and
arcC1
(
arcABC
). These genes are members of the ADI operon, encoding enzymes of the arginine deiminase system. The second is the EF_1459 gene, which encodes a hypothetical protein and is located within a putative phage genetic element. Lastly, Ef_3319 is annotated as the alpha subunit of the citrate lyase encoded by
citF. citF
is a member of a putative 12-gene operon involved in citrate catabolism. Moreover, the promoter sequence, similar to the “PrfA box” and found in the promoter regions of
ers
and EF_0082, has been shown to be included in the DNA segment recognized by Ers. Phenotypic analysis of the Δ
ers
mutant strain revealed a growth defect when cultured with arginine or citrate as the energy source; this was not seen for the wild type. As expected, similar results were obtained with mutants in which
arcA
and
citF
were inactivated. In addition, in the mouse peritonitis model of virulence, the Δ
ers
mutant appeared significantly less lethal than the JH2-2 wild-type strain. Taken together, these results indicate that the regulator Ers has a pleiotropic effect, especially in the cellular metabolism and virulence of
E. faecalis
.