bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Fidelity Numerical Analysis of Per-Rev-Type Inlet Distortion Transfer in Multistage Fans: Part I—Simulations With Selected Blade Rows
Authors: Yao Jixian , Gorrell Steven E. , Wadia Aspi R.
Published: August 2009

Demands for improved performance and operability of advanced propulsion systems require an understanding of the physics of inlet flow distortion transfer and generation and the subsequent engine response. This also includes developing a high-fidelity characterization capability and suitable tools/rules for the design of distortion tolerant engines. This paper describes efforts to establish a high-fidelity prediction capability of distortion transfer and fan response via high-performance computing. The current CFD capability was evaluated with a focus of predicting the transfer of prescribed inlet flow distortions. Numerical simulations, comparison to experimental data, and analysis of two selected three-stage fans are presented. The unsteady RANS code Pturbo demonstrated remarkable agreement with data, accurately capturing both the magnitude and profile of total pressure and total temperature measurements. Part I of the paper describes the establishment of the required numerical simulation procedures. The computational domains are limited to the first three blade rows for the first multistage fan and the last three blade rows for the second fan. The paper presents initial validation and analysis of the total pressure distortion transfer and the total temperature distortion generation. Based on the established ground work of Part I, the entire two multi-stage fans were simulated with inlet distortion at normal operating condition and near stall condition, which is part II of the paper. Part II presents the full range validation against engine test data, and in-depth analysis of distortion transfer and generation mechanisms through out the two fans.
Film-Cooling Effectiveness From Shaped Film Cooling Holes for a Gas Turbine Blade
Authors: Mhetras Shantanu , Han Je-Chin , Rudolph Ron
Published: August 2009

The effect of film cooling holes placed along the span of a fully-cooled high pressure turbine blade in a stationary, linear cascade on film cooling effectiveness is studied using the Pressure Sensitive Paint (PSP) technique. Six rows of compound angled shaped film cooling holes are provided on the pressure side while four such rows are provided on the suction side of the blade. The holes have a laidback and fan-shaped diffusing cross-section. Another three rows of holes are drilled on the leading edge to capture the effect of showerhead film coolant injection. The film cooling hole arrangement simulates a typical film cooled blade design used in stage 1 rotor blades for gas turbines used for power generation. A minimum blowing ratio is defined for each film hole row and tests are performed for 1.0x, 1.33x, 1.67x, 2.0x and 2.67x of this minimum value. Tests are performed for an inlet Mach number of 0.36 with a corresponding exit Mach number of 0.51. The flow remains subsonic in the throat region. The corresponding free stream Reynolds number, based on the axial chord length and the exit velocity, is 1.3 million. Turbulence intensity level at the cascade inlet is 5% with an integral length scale of around 5cm. Results show that varying blowing ratios can have a significant impact on film-cooling effectiveness distribution. Large spanwise variations in effectiveness distributions are also observed. Results also show that the effectiveness magnitudes from superposition of effectiveness data from individual rows are comparable with that from full coverage film cooling.
Spatio-Temporal Characterization of a Conical Swirler Flow Field Under Strong Forcing
Authors: Lacarelle A. , Faustmann T. , Greenblatt D. , Paschereit C. O. , Lehmann O. , Luchtenburg D. M. , Noack B. R.
Published: August 2009

In this study, a spatio-temporal characterization of forced and unforced flows of a conical swirler is done based on Particle Image Velocimetry (PIV) and Laser Doppler Anemometry (LDA). The measurements are performed at a Reynolds number of 33,000 and a swirl number of 0.71. Axisymmetric forcing is applied to approximate the effects of thermoacoustic instabilities on the flow field at the burner inlet and outlet. The actuation frequencies are set at the natural flow frequency (Strouhal number Stf ≈ 0.92) and two higher frequencies (Stf ≈ 1.3 and 1.55) that are not harmonically related. Phase locked and phase averaged measurement are used as a first step to visualize the coherent flow structures. Secondly, Proper Orthogonal Decomposition (POD) is applied to the PIV data to characterize the effect of the actuation on the fluctuating flow. Measurements indicate a typical natural flow instability of helical nature in the unforced case. The associated induced pressure and flow oscillations travel upstream to the swirler inlet where generally fuel is injected. This observation is of critical importance with respect to the stability of the combustion. Harmonic actuation at different frequencies and amplitudes affects the mean-field profile most at the outlet, while the coherent velocity fluctuations are strongly influenced at both inlet and outlet. On one hand, the dominant helical mode is replaced by an axisymmetric vortex ring if the flow is forced at the natural flow frequency. On the other hand, the natural flow frequency prevails at the outlet under forcing at higher frequencies and POD analysis indicates that the helical structure is still present. The presented results give new insight into the flow dynamics of a swirling flow burner under strong forcing.
GT Inlet Air Boosting and Cooling Coupled With Cold Thermal Storage in Combined Cycle Power Plants
Authors: Palestra Nicola , Barigozzi Giovanna , Perdichizzi Antonio
Published: August 2009

Investigation results of compressor inlet air boosting and cooling, applied to combined cycle power plants, are presented and discussed. Gas turbine performances may be reduced by site altitude and inlet losses due to air ducts and filters. Increasing inlet pressure by fans allows the restoring of gas turbine power output and efficiency at least to ISO reference conditions. Coupling such a system with inlet air cooling may completely suppress the temperature increase given by inlet air compression and the pressure losses through air coils as well; therefore, by this way, a further increase of electric energy production can be achieved. An in-house simulation code, developed for evaluating inlet air cooling system performance by cool thermal storage, has been adapted in order to also simulate off-design behaviour of boosting applied to combined cycle plants. A 127 MW reference power plant, operating in the Italian scenario, has been considered. Inlet pressure increase has been evaluated with and without inlet cooling, and in comparison with inlet cooling solution alone. Both thermodynamic and economical results have been analyzed. A parametric analysis on both system sizing parameters has been carried out. Best solution was found in coupling boosting to inlet cooling system through cool thermal storage; it produced an important increase in electric energy production. Location site influence on investment pay-back proved to be less important compared to the solution with inlet air cooling system alone.
Effects of Inlet Conditions on the Turbine Performance of a Radial Turbine
Authors: Hellstrom Fredrik , Fuchs Laszlo
Published: August 2009

For a turbocharger working under internal combustion engine operating conditions, the flow will be highly pulsatile and the efficiency of the radial turbine will vary during the engine cycle. In addition to effects of the inflow unsteadiness, there is also always a substantial unsteady secondary flow component at the inlet to the turbine depending on the geometry upstream. These secondary motions may consist of swirl, Dean vortices and other cross-sectional velocity components formed in the exhaust manifold. The strength and the direction of the vortices vary in time depending on the unsteady flow in the engine exhaust manifold, the engine speed and the geometry of the manifold itself. The turbulence intensity may also vary during the engine cycle leading to a partially developed turbulent flow field. The effect of the different perturbations on the performance of a radial nozzle-less turbine is assessed and quantified by using Large Eddy Simulations. The turbine wheel is handled using a sliding mesh technique, whereby the turbine wheel, with its grid is rotating, while the turbine house and its grid are kept stationary. The turbine performance has been compared for several inflow conditions. The results show that an inflow-condition without any perturbations gives the highest shaft power output, while a turbulent flow with a strongly swirling motion at the inlet results in the lowest power output. An unexpected result is that a turbulent inflow yields a lower shaft power than a turbulent inflow with a secondary flow formed by a pair of Dean vortices. The flow field for the different cases is investigated to give a better insight into the unsteady flow field and the effects from the different inlet conditions.
Transient Combustion Modeling of an Oscillating Lean Premixed Methane/Air Flame
Authors: Withag Jan A. M. , Kok Jim B. W. , Syed Khawar
Published: August 2009

The main objective of the present study is to demonstrate accurate low frequency transient turbulent combustion modeling. For accurate flame dynamics some improvements were made to the standard TFC combustion model for lean premixed combustion. With use of a 1D laminar flamelet code, predictions have been made for the laminar flame speed and the critical strain rate to improve the TFC (Turbulent Flame Speed Closure) combustion model. The computational fluid dynamics program CFX is used to perform transient simulations. These results were compared with experimental data of Weigand et al [1]. Two different turbulence models have been used for predictions of the turbulent flow.
Efficient Computational Model for Non-Axisymmetric Flow and Heat Transfer in Rotating Cavity
Authors: He L.
Published: August 2009

Existence of large scale unsteady flow structures manifested in contra-rotating vortex pairs has been previously identified in rotor disc cavities. The non-axisymmetric nature with a unknown number of vortices presents a computational challenge as a full 360° circumferential domain will be needed, requiring significant computational resources. A novel circumferential spatial Fourier spectral technique is adopted in the present work to facilitate efficient computational predictions of the non-axisymmetric flows. Given that the flow non-uniformities in the circumferential direction are of large length scales, only a few circumferential Fourier harmonics would be needed, resulting in a drastic reduction in number of circumferential mesh points to be required. The modeling formulations and implementation aspects will be described. Computational examples will be presented to demonstrate the validity and effectiveness of the present modeling approach. The computational results show that the non-axisymmetric flow patterns in terms of the number of vortex pairs are sensitive to small scale external disturbances. It is also indicated that the occurrence of a non-axisymmetric flow might be captured by the present Fourier solution with even one harmonic.
Radial Swirlers and Mixing Tube Assembly Aerodynamics and Performance Parameters Evaluation: Part 2—LDV Measurements at the Mixing Tube Outlet
Authors: Canepa Edward , Di Martino Pasquale , Lengani Davide , Ubaldi Marina , Zunino Pietro
Published: August 2009

Present work represents the second part of a two parts paper. The complex aerodynamic phenomena, which take place both inside and downstream the swirler–mixing tube assembly, have been studied with different and complementary techniques in order to have a complete characterization of the effect of the geometrical parameters variation on many aspects of the flow. The first part was focused on the aerodynamic analysis of the flow in the swirler exit plane, while this second part is focused on the experimental investigation on the flow inside and downstream the mixing tube. Measurements have been performed on three axial stations. One is placed inside the mixing tube, in order to characterize the flow arriving from the swirler. The other two are placed downstream the mixing tube discharge section in order to identify the main flow features, such as the presence of flow recirculation and consequently the radial extension of the separation bubble. A four beams two colours Laser Doppler Velocimeter (Dantec Fiber Flow), in backward scatter configuration mounted on a three-axis computer-controlled traversing mechanism, was employed for the present study. Results indicate a strong influence of the geometrical parameters on the flowfield in terms of velocity component distributions, turbulence intensity and separation bubble extension. Moreover results from the Laser Doppler Velocimeter measuring campaign allow basically to evaluate three main performance parameters which are the friction loss coefficient, the semi-theoretical swirl number evaluated from the assembly geometry and the measured swirl number, which is calculated in the mixing tube outlet section. The first one is indicative of the angular momentum dissipation, while the other two represent the main parameters which are involved in the vortex breakdown onset and evolution, that in one case is derived from measurements and in the other is partially theoretical.
Development of Numerical Tools for Stator-Rotor Cavities Calculation in Heavy-Duty Gas Turbines
Authors: Bianchini C. , Da Soghe R. , Facchini B. , Innocenti L. , Micio M. , Bozzi L. , Traverso S.
Published: August 2009

In high performance heavy-duty engines, turbine inlet temperature is considerably higher than the melting point of the metals used for turbine components e.g. nozzle guide vanes, turbine rotor blades, platforms and discs, etc. Cooling of those components is therefore essential and is achieved by diverting a few percent of the compressed air from extraction points in the compressor and passing it to the turbine through stationary ducts and over rotating shafts and discs. All those elements form the so-called secondary air system of the gas turbine, whose correct design is hence fundamental for safety, reliability and performance of the engine. Secondary air system analysis is generally performed using one dimensional calculation procedures, based correlations both for pressure losses and heat transfer coefficient evaluations. Such calculation approach, usually used in industry, takes advantages in terms of reduced computational resources. Besides, for those elements of air systems where multidimensional flow effects are not negligible and the flow field structure is highly complex, the one-dimensional–correlative modeling needs to be supported by CFD investigations. Among these elements, rotating cavities need a careful modeling in order to correctly estimate discs temperature and the minimum amount of purge air to prevent hot gas ingestion. Ansaldo Energia is facing the investigation of secondary air system of Vx4.3A gas turbine models also by using numerical tools developed by Dipartimento di Energetica “Sergio Stecco” of University of Florence. They include both a one-dimensional cavity solver and a 3D unstructured finite volume code of compressible Navier-Stokes Equation based on open source C++ Open-Foam libraries for continuum mechanics. The first numerical tool has been widely employed in simplified analysis of stator-rotor cavities and is undergoing to be integrated into a in-house lumped-parameters fluid network solver simulating the entire secondary air system. This paper is aimed at discussing some interesting results from numerical tests performed with the above discussed programs on stator-rotor cavities of a V94.3A2 gas turbine. Such numerical analysis was addressed both for better understanding the flow phenomena in the wheel space regions and for testing and verifying the experimental correlations and the calculation procedure implemented in the one-dimensional program. A detailed comparative analysis between the two different codes will be shown, both in adiabatic and heat transfer conditions.
On the Interpretation of Casing Measurements in Axial Compressors
Authors: Cameron Joshua D. , Morris Scott C. , Barrows Sean T. , Chen Jen-Ping
Published: August 2009

Experimental studies of stall inception in axial compressors typically involve the measurement of basic flow variables (often pressure or velocity) with low spatial resolution. These measurements are used to make inferences about the fluid dynamics of stall. This experimental paradigm has been used by many investigators to great effect over the last several decades. However, several limitations remain which restrict the utility of these types of measurements for developing further insight into stall inception physics. Primary among these limitations is the impracticality of making measurements within the rotating blade passages. This is especially troublesome in light of recent computational studies which indicate that the generation of short length-scale rotating disturbances is related to the rotor tip clearance flow. This study utilized the results of a recent full annulus rotating stall simulation to investigate the relationships between the casing pressure field and less observable flow quantities which are believed to be causally related to the generation of rotating disturbances. The CFD results are assumed to represent the true flow physics within the compressor. To the extent that this approximation is true, these results can be used to interpret the meaning of experimental measurements of basic flow variables. These observations not only provide new insight into the interpretation of the large catalog of experimental stall measurements found in the literature, they also give directives for future measurements and numerical simulations.
System Design of a Novel Combined Cooling, Heat, Power, and Water Microturbine Combined Cycle
Authors: Lear William E. , Ryu ChoonJae , Crittenden John F. , Srinivasan Aditya , Ellis William , Tiffany David R. , Sherif Sherif A. , Meitner Peter L.
Published: August 2009

The Power, Water Extraction, and Refrigeration (PoWER) engine has been investigated for several years as a distributed energy system, among other applications, for civilian or military use. Previous literature describing its modeling and experimental demonstration have indicated several benefits, especially when the underlying semi-closed cycle gas turbine is combined with a vapor absorption refrigeration system, the PoWER system described herein. The benefits include increased efficiency, high part-power efficiency, small lapse rate, compactness, less emissions, less air and exhaust flows (which decrease filtration and duct size) and condensation of fresh water. The current paper describes the preliminary design and modeling of a modified version of this system as applied to distributed energy, especially useful in regions which are prone to major grid interruptions due to hurricanes, under-capacity, or terrorism. In such cases, the distributed energy system should support most or all services within an isolated service island, including ice production, so that the influence of the power outage is limited in scope. The current paper describes the rather straightforward system modifications necessary for ice production. The primary focus of the paper is the use of this ice-making capacity to achieve significant load-leveling during the summer utility peak, hence reducing the electrical capacity requirements for the grid as well as load-leveling strategies.
Gas Turbine Power Augmentation: Parametric Study Relating to Fog Droplet Size and Its Influence on Evaporative Efficiency
Authors: Chaker Mustapha , Meher-Homji Cyrus B.
Published: August 2009

Several gas turbine power augmentation techniques are available to counter the detrimental drop in power and thermal efficiency that occur at high ambient temperatures. Inlet fogging and wet compression are two common and relatively simple techniques. This paper addresses the influence and importance of droplet size on evaporative cooling performance and efficiency. Common spray nozzles used for inlet fogging and wet compression are the impaction pin, swirl jet, air assisted, and swirl flash nozzles. The atomization process from these nozzles and their performance depends on the droplet size, size distribution, and spray plume shape. Droplets size varies with nozzle types, configurations, operating conditions, and nozzle manifold location in the gas turbine inlet duct as they are affected by airflow velocity, residence time coalescence effects, evaporation efficiency, and water carryover. The proper selection of nozzle type and location and nozzle distribution are of importance to avoid large droplets and under/over saturated areas which would affect compressor mechanical and aerodynamic efficiency. Analytical and numerical studies are compared to experimental results available from installed systems, and treated in the literature. This paper provides a comprehensive treatment of parameters affecting droplet size and will be of value to gas turbine fog system designers and users.
Effect of Temporal Accuracy on the Numerical Prediction of an Isolated Transonic Rotor at Near Stall Conditions
Authors: Lee Daniel , Orkwis Paul D. , Tsung Fu-Lin , Magnuszewski William , Noll Christopher
Published: August 2009

A numerical investigation of the NASA Rotor 35 transonic compressor rotor at near stall conditions was conducted with an unsteady RANS technique. A series of time-step size and inner iterations were chosen to create a design-of-experiment matrix to study their impact on the unsteady flow field. Solution accuracy is determined by comparisons with LDV, and pressure and temperature profiles. Results obtained showed that for this near stall unsteady flow field unsteady analysis is required. However, an asymptotic relationship does not exist between increased numerical temporal accuracy and improved solution predictions. This paper discusses the physical flow features of a transonic rotor near stall as well as reasons why increased temporal accuracy does not guarantee the solution to asymptotically approach the data.
Film Cooling From a Row of Holes With Both Ends Embedded in Transverse Slots
Authors: Zhang D. H. , Sun L. , Chen Q. Y. , Lin M. , Zeng M. , Wang Q. W.
Published: August 2009

Embedding a row of typical cylindrical holes in a transverse slot can improve the cooling performance. Rectangular slots can increase the cooling effectiveness but is at the cost of decreasing of discharge coefficients. An experiment is conducted to examine the effects of an overlying transverse inclined trench on the film cooling performance of axial holes. Four different trench configurations are tested including the baseline inclined cylindrical holes. The influence of the geometry of the upstream lip of the exit trench and the geometry of the inlet trench on cooling performance is examined. Detailed film cooling effectiveness and heat transfer coefficients are obtained separately using the steady state IR thermography technique. The discharge coefficients are also acquired to evaluate the aerodynamic performance of different hole configurations. The results show that the film cooling holes with both ends embedded in slots can provide higher film cooling effectiveness and lower heat transfer coefficients; it also can provide higher discharge coefficients whilst retaining the mechanical strength of a row of discrete holes. The cooling performance and the aerodynamic performance of the holes with both ends embedded in inclined slots are superior to the holes with only exit trenched. To a certain extent, the configuration of the upstream lip of the exit trench affects the cooling performance of the downstream of the trench. The filleting for the film hole inlet avail the improvement of the cooling effect, but not for the film hole outlet. Comparing film cooling with embedded holes to unembedded holes, the overall heat flux ratio shows that the film holes with both ends embedded in slots and filleting for the film hole inlet can produce the highest heat flux reduction.
A Systematic Comparison and Multi-Objective Optimisation of Humid Power Cycles: Part I—Thermodynamics
Authors: Kavanagh Ronan M. , Parks Geoffrey T.
Published: August 2009

The STIG, HAT and TOPHAT cycles lie at the centre of the debate on which humid power cycle will deliver optimal performance when applied to an aero-derivative gas turbine and, indeed, when such cycles will be implemented. Of these humid cycles, it has been claimed that the TOPHAT cycle has the highest efficiency and specific work, followed closely by the HAT (Humid Air Turbine) and then the STIG (STeam Injected Gas turbine) cycle. In this study, the systems have been simulated using consistent thermodynamic and economic models for the components and working fluid properties, allowing a consistent and non-biased appraisal of these systems. Part 1 of these two papers focusses purely on the thermodynamic performance and the impact of the system parameters on the performance, part 2 will study the economic performance. The three humid power systems and up to ten system parameters are optimised using a multi-objective Tabu Search algorithm, developed in the Cambridge Engineering Design Centre.
Pre-Stall Instability Distribution Over a Transonic Compressor Rotor
Authors: Gannon A. J. , Hobson G. V.
Published: August 2009

An investigation of the behavior of a transonic compressor rotor when operating close to stall is presented. The specific area of interest is the behavior and location of low-frequency instabilities when operating close to stall. When running close to stall compressors begin to exhibit non-periodic flow between the blade passages even when appearing to be operating in a stable steady-state condition. These frequencies are not geometrically fixed to the rotor and typically appear at 0.3–0.8 of the rotor speed. The presence of these low-frequency instabilities are known and detection are reasonably commonplace, however attempts to quantify the location and strength of these instabilities as stall is approached have proved difficult. In the test rotor probes were positioned in the case-wall upstream, downstream and over the rotor blade tips. Simultaneous data from all the probes was taken at successive steady-state settings each operating closer to stall. The simultaneous data is presented to show the development and distribution of the instabilities over the rotor as stall was approached. Initially the instabilities appeared within the rotor row and extended downstream. At operation closer to stall they protruded upstream and downstream. The greatest amplitude of the instabilities was within the blade row in the complex flow region that contained the tip-vortex interacting with the shock and the shock impinging on the blade suction surface. In the current rotor the data shows that the instabilities were present during steady-state operation when stall was approached even when stall was not imminent. In addition they do not behave in a linear manner as stall was approached.
Feasibility Study of Low Grade Heat Recovery Rankine Cycle Using Ozone-Neutral Refrigerant
Authors: Husband W. Wayne , Beyene Asfaw
Published: August 2009

The paper addresses the feasibility of ozone-neutral low grade heat recovery to produce power. The low grade heat source can either be industrial exhaust or solar radiation. Using a scroll expander as a basis for testing, theoretical models yielded a thermal efficiency of 11%, utilizing a non-toxic and non-hazardous working fluid. This project spanned research and development of a system from the comparison of several working fluids, modeling of a theoretical 10 kW unit, the sizing and selection of appropriate system components, and the development of project management tools, in support of its real world development. A cost benefit analysis of the theoretical system shows that solar heat recovery with ozone-neutral refrigerant is a viable option for power generation, at about 1/3 the cost of a comparable photovoltaic system.
Urban minority youth swimming (in)ability in the United States and associated demographic characteristics: toward a drowning prevention plan
Authors: Irwin C C , Irwin R L , Ryan T D , Drayer J
Published: August 2009

Objective:

To examine swimming ability and variables associated with swimming for US inner-city, minority children. Empirical research on minority children’s swimming ability is non-existent, and drowning rates for this population are high.

Design:

Cross-sectional survey research. Descriptive statistics were produced. Multiple regression was applied using significant demographic variables by swimming ability.

Setting:

Six US cities were chosen (Chicago, Illinois; Houston, Texas; Memphis, Tennessee; Miami, Florida; Oakland, California; Philadelphia, Pennsylvania). Young Men’s Christian Association (YMCA) facilities were used to solicit subjects.

Subjects:

A large sample (n = 1680) was gathered, which targeted poor, minority children. Parents of children aged 4–11 years and adolescents (12–17 years) completed surveys that research team members or trained YMCA staff supervised during non-swimming YMCA programmes.

Results:

African–American respondents reported a 57.5% “at risk” (unable to swim or uncomfortable in deep end of pool) swimming ability. Hispanic/Latino children confirmed a 56.2% “at risk” level as compared with 30.9% for white subjects. Age, sex, child’s lunch programme, parental education and race variables were all significantly (p<0.05) related to swimming ability. Regression analysis revealed that all demographic variables fell into a significant model (p<0.001) as predictor variables.

Conclusions:

Poor minority children, specifically African–American and Hispanic/Latino, are at a significant disadvantage concerning swimming ability. Female subjects were notably more “at risk” regarding their swimming ability than male subjects. Age, race and socioeconomic factors (lunch programme and parental education) were significantly associated with children who have low swimming ability.
Prevention factors for suicide ideation among abused pre/early adolescent youths
Authors: Logan J E
Published: August 2009

Suicide ideation is a problem among youths who have been previously abused. This study assesses whether three factors (ie, feeling connected to school, having parents who reward good behaviour, and feeling able to cope with peer conflict) are negatively associated with suicidal ideation for 2598 pre/early adolescents with various levels of prior abuse. For the entire youth population, those who reported all three factors were less than half as likely to have suicidal thoughts as those who did not report any of these factors (10.8% vs 30.3%, p<0.05). This pattern was similar and significant for youths who experienced peer abuse (10.2% vs 35.0%, p<0.05) and youths who experienced both early child abuse and peer abuse (21.6% vs 54.8%, p<0.05). Comprehensive programmes that improve school connectedness, parent–child relationships and coping skills to avoid violent peer conflicts might help decrease suicide ideation among youths, particularly those who have been previously abused.
Differential risk of employment in more physically demanding jobs among a recent cohort of immigrants to Canada
Authors: Smith P M , Chen C , Mustard C
Published: August 2009

Objective:

To examine the proportion of a recent cohort of immigrants to Canada who were working in jobs that were more physically demanding than those in which they worked before migration to Canada.

Design:

Longitudinal cohort of immigrants to Canada with occupational position measured before and 2 and 4 years after arrival in Canada.

Subjects:

Respondents to Statistics Canada’s Longitudinal Survey of Immigrants to Canada (LSIC). The LSIC surveyed a representative sample of immigrants, aged 15 and older, who arrived in Canada between November 2000 and December 2001. For the purpose of this study, the sample was restricted to respondents who had worked before immigrating and were working when re-interviewed 2 (n = 4331) or 4 (n = 4238) years after arrival in Canada.

Main outcome:

Employment in an occupation with higher physical demands than that employed in before arrival in Canada.

Results:

Respondents with less proficiency at speaking English and family class or refugee applicants were the most likely to be employed in occupations with higher physical demands both 2 and 4 years after arrival in Canada.

Conclusions:

Employment in a more physically demanding occupation may pose particular risks of workplace injury. In this sample of immigrants to Canada, respondents with poorer English skills and refugees (factors that may increase this risk) were more likely to be employed in more physically demanding occupations. Greater attention to the prevention of workplace injuries among particular groups of new immigrants to Canada is required.
Recent trends in television tip over-related injuries among children aged 0–9 years
Authors: Murray K J , Griffin R , Rue L W , McGwin G
Published: August 2009

Objective:

To describe recent trends in television tip over-related injuries among children aged 0–9 years, and to compare injury rates with sales of newer digital televisions.

Methods:

Digital television sales data were obtained from marketing data provided by the Television Bureau of Advertising. Data regarding television tip over-related injuries among children aged 0–9 years were obtained from the 1998–2007 National Electronic Injury Surveillance System. A Wald χ2test, estimated from logistic analysis, was used to determine whether the distribution of injury types differed by age group. Pearson’s correlation was used to estimate the association between digital television sales and television tip over-related injuries.

Results:

An estimated 42 122 (95% CI 35 199 to 49 122) injuries from television tip-overs were treated in US emergency departments from 1998 to 2007. The injury rate was highest for children aged 1–4 years (18.6/100 000). A majority of injuries (63.9%) involved the head and neck for children under 1 year of age, while a higher proportion of injuries among children aged 1–4 involved the hip and lower extremity (42.9% and 31.0%, respectively), and shoulder and upper extremity (16.8%) for children aged 5–9. A strong, positive correlation was observed between television sales and annual injury rates (r = 0.89, p<0.001).

Conclusion:

Estimates of injury rates were similar to previously reported estimates, particularly for the increased proportion of head and neck injuries among very young children. While digital television sales were strongly correlated with increased injury rates, the lack of information regarding the type of television involved prevents inference regarding causation.
Density-Dependent Maturation, Growth, and Female Dominance in Lake Superior Lake Herring (Coregonus artedii)
Authors: Bowen Stephen H. , D'angelo Donna J. , Arnold Stephen H. , Keniry Michael J. , Albrecht Ronald J.
Published: August 2009

Density-related changes in age at maturation, sex ratio of recruits, growth, and fecundity at very low density result in spawning populations which comprise many older females and few young males and in which egg production per lake herring (Coregonus artedii) is increased by a factor of five. Age of maturation is delayed at low density for females, but not for males. Thus, males dominate the youngest age classes but females become increasingly more abundant from age 2 + through age 6 +. A model of lake herring population structure showed that although delayed maturation accounts for many characteristics of depressed populations, it does not explain overall population femaleness. The model was used to evaluate effects of differential adult mortality, recruitment failure, and changes in the sex ratio of recruits, and only the latter provided an adequate explanation for overall femaleness. Despite the apparently compensatory nature of these responses, the slow and unsteady recovery of depressed Lake Superior populations during the last two decades indicates that one or more additional factors play important roles in determination of year class strength.
Enzymic comparisons of the inorganic sulfur metabolism in autotrophic and heterotrophic Thiobacillus ferrooxidans
Authors: Tuovinen Olli H. , Kelley Bruce C. , Nicholas D. J. Donald
Published: August 2009

Activities of enzymes which mediate the oxidation of thiosulfate to sulfate and the assimilation of sulfate to sulfide were assayed in various cell-free fractions of Thiobacillus ferrooxidans grown autotrophically on either ferrous iron or thiosulfate or heterotrophically on glucose. There was no activity of the thiosulfate-oxidizing enzyme in extracts of bacteria grown with ferrous iron. Comparable activities for ATP-sulfurylase (EC 2.7.7.4), ADP-sulfurylase (EC 2.7.7.5), and adenylate kinase (EC 2.7.4.3) were found in the bacteria grown autotrophically with either Fe2+ or S2O32− or heterotrophically with glucose.
Disruption of Glial Function Regulates the Effects of Electro-Acupuncture atTsusanlion Gastric Activity in Rats
Authors: Wang Sheng-Zhi , Liu Xiao-Dong , Huang Yu-Xin , Ma Qing-Jiu , Wang Jing-Jie
Published: August 2009

According to recent evidence, acupuncture at Tsusanli (ST 36) can regulate gastric activity. And this regulation mainly depends upon neural basis or structure and may probably relate to the central neurons in the dorsal vagal complex. However, whether the glias of the dorsal vagal complex participate in the regulation of gastric activity, when electro-acupuncture (EA) at Tsusanli, still remains to be interpreted. In this study, we observed the effect of EA at Tsusanli (ST 36) on regulation of gastric activity. Propentofylline (PPF), a glial metabolic inhibitor, was used to inhibit the function of glial cells. EA at Tsusanli showed that the expressions of glial fibrillary acidic protein (GFAP) and OX42 increased significantly compared to that of the control group, and gastric electric change was obvious, with significantly higher frequency and wave amplitude compared to the control group. The expressions of GFAP and OX42 were decreased markedly when pretreated with PPF group than without PPF pretreatment group. Compared to the Tsusanli group and the control group, the changes of electro gastric graph (EGG) were significantly decreased in PPF pretreatment group. On the other hand, we observed the changes of spontaneous electro-activity of the DVC (dorsal vagal complex) in our previous experiment.

The results indicated that EA at Tsusanli could activate glial cells in the dorsal vagal complex and regulate gastric activity. PPF blocked the function of glia, thus the effect of EA at Tsusanli on gastric activity was weakened. Our study suggested that this electro-acupuncture regulation of gastric activity was possibly related with glia of the dorsal vagal complex.
Effects of Extracts fromPaederia scandens(LOUR.)MERRILL(Rubiaceae) on MSU Crystal-Induced Rats Gouty Arthritis
Authors: Ma Ying , Zhou Lan-Lan , Yan Hai-Yan , Liu Mei
Published: August 2009

The effects of extract of Paederia scandens (LOUR.) MERRILL (Rubiaceae) (EPS), a Chinese traditional herbal medicine, on inflammatory and immune responses and their mechanisms in MSU crystals-induced (GA) rats were studied. GA rats were established. Ankle joint volume of rats was measured by volume meter; the level of TNF-α and IL-1β was determined by radioimmunoassay. mRNA expressions of TNF-α and IL-1β in synovial tissue of GA rats were analyzed by RT-PCR, and the expression of NF-κB was detected by immunohistochemistry. The administration of EPS (2.25, 4.5 g/kg, ig 9 days) inhibited the inflammatory response in GA rats. The mRNA expressions of TNF-α and IL-1β were also significantly suppressed in synovial tissue. In addition, EPS (2.25, 4.5 g/kg, ig 9 days) inhibited the expression of TNF-α and IL-1β and the biological activity of NF-κB. These results suggested that EPS possesses antiinflammatory effects by modulating pro-inflammatory mediators' production in synovial tissue and inactivating NF-κB pathway transmembrane signal transduction which plays a crucial role in the pathogenesis of this disease.
In vitro Activity of Impatiens balsamina L. Against Multiple Antibiotic-Resistant Helicobacter pylori
Authors: Wang Yuan-Chuen , Wu Deng-Chang , Liao Jyun-Ji , Wu Cheng-Hsun , Li Wan-Yu , Weng Bi-Chuang
Published: August 2009

Impatiens balsamina L. has been used as indigenous medicine in Asia for the treatment of rheumatism, fractures, and fingernail inflammation. In this study, anti-H. pylori activity of I. balsamina L. was investigated. The MICs, MBCs, time-kill assay, and effect of environmental pH for the plant extracts were determined. The test H. pylori strains have resistance to clarithromycin (CLR), metronidazole (MTZ), and levofloxacin (LVX). From our results, all part (root/stem/leaf, seed, and pod) extracts of I. balsamina L. exhibited bactericidal H. pylori activity. Specifically, the pod extract had significantly lower MICs and MBCs (1.25–2.5 and 1.25–5.0 μg/ml, respectively). Of the five pod-extraction solvents, both ethyl acetate and acetone were the most efficient for the anti-H. pylori compounds of the pod extraction. The dose-dependency of the pod extract's bactericidal activity was H. pylori strain-dependent. Bactericidal H. pylori activity of the pod extract was not affected by the environmental pH (2–8). In summary, the acetone and ethyl acetate pod extracts of I. balsamina L. exhibited very strong anti-H. pylori activity. This activity exceeded that of MTZ and approximated to that of AMX.
Antioxidant and Antiproliferative Activities of Crossostephium chinensis (L.) Makino
Authors: Chang Tien-Ning , Huang Guan-Jhong , Ho Yu-Lin , Huang Shyh-Shyun , Chang Heng-Yuan , Chang Yuan-Shiun
Published: August 2009

Crossostephium chinensis (L.) (CC) Makino is a common traditional Chinese medicinal plant used to dehumidify and cure rheumatism and arthralgia. The water and methanol extracts of C. chinensis (CCW and CCM) were evaluated for their antioxidant and antiproliferative activities. The antioxidant activities of CC were evaluated by using ABTS radical scavenging, DPPH radical scavenging, nitric oxide scavenging and superoxide scavenging methods. Iron chelating activity, lipid peroxidation, total polyphenol contents, total flavonoid contents and total flavonol contents were also detected. In all the tested models, both CCW and CCM showed their ability to scavenge the free radicals in a does-dependent manner. CCW had higher antioxidant and antiproliferative activities than CCM. In LC-MS-MS analysis, the chromatograms of CCW with good antioxidant activities were established. Rutin might be an important bioactive compound in CCW. The antiproliferative activities of CCW and CCM were also studied in vitro by using human hepatoma HepG2 cells. CCW exhibited good antiproliferative activity. These results indicated that CCW might be used as a potential source of natural antioxidants and as an anti-tumor agent.
Antioxidant and Antiradical Activities of Wu Ling Shen in a Cell Free System
Authors: Ko Huey-Jiun , Song Airong , Lai Min-Nan , Ng Lean-Teik
Published: August 2009

The present study aimed to investigate the antioxidant and antiradical activities of Wu Ling Shen, a popular medicinal fungus (Xylaria nigripes) used in traditional Chinese medicine preparations. Two different X. nigripes materials, the cultivated X. nigripes mycelia (XN) and a commercial X. nigripes product (XNP), were used to prepare the aqueous (XN-H vs. XNP-H) and ethanol (XN-E vs. XNP-E) extracts for this study. Polyphenol and total polysaccharide contents of these extracts were also examined. Results showed that extracts of XN possessed stronger antioxidant and antiradical activities than XNP in all tested model systems. However, all extracts exhibited a weak activity in metal chelation and reducing power. Total antioxidant activity of XN extracts (IC50 6.20 μg/ml for XN-H and 5.41 μg/ml for XN-E), but not XNP extracts (IC50 128.13 μg/ml for XNP-H and 96.16 μg/ml for XNP-E), was more potent than Trolox (IC50 19.64 μg/ml) and vitamin C (IC50 26.39 μg/ml). XN-E (IC50 5.12 μg/ml) and XNP-E (IC50 8.89 μg/ml) possessed a relatively similar potency as that of positive controls (IC50 6.94 μg/ml for Trolox and 4.25 μg/ml for vitamin C) in the superoxide radical scavenging activity. Although the DPPH radical scavenging of XN extracts was weaker than that of Trolox and vitamin C, it was about eight times more potent than that of XNP extracts. In ABTS assay, both XN and XNP extracts exhibited a moderate ABTS radical scavenging activity. Among the different extracts, XN-E showed the highest total flavonoid (32.69 mg/g) and phenol (59.75 mg/g) contents, while XNP-H (7.50% w/w) had the highest level in total polysaccharide content. These results conclude that XN-E possesses the most potent antioxidant and antiradical activities, and that these activities could be derived from its high polyphenol content, but not the level of polysaccharides.
AN INFERENCE-ENABLED ACCESS CONTROL MODEL FOR RDF ONTOLOGY
Authors: JING YIXIN , JEONG DONGWON , BAIK DOO-KWON
Published: August 2009

Although RDF ontologies are expressed based on XML syntax, existing methods to protect XML documents are not suitable for securing RDF ontologies. The graph style and inference feature of RDF ontologies demands new methods for access control. Driven by this goal, this paper proposes a query-oriented model for RDF ontology access control. The model adopts the concept of ontology view to rewrite user queries. In our approach, ontology views define accessible ontology concepts and instances a user can visit, and enables a controlled inference capability for the user. The design of the views guarantees that the views are free of conflict. Based on that, the paper describes algorithms for rewriting queries according to different views, and provides a system architecture along with an implemented prototype. In the evaluation, the system exhibits a promising result in terms of effectiveness and soundness.
Viruses of Plant Pathogenic Fungi
Authors: Ghabrial Said A. , Suzuki Nobuhiro
Published: August 2009

Mycoviruses are widespread in all major groups of plant pathogenic fungi. They are transmitted intracellularly during cell division, sporogenesis, and cell fusion, but apparently lack an extracellular route for infection. Their natural host ranges are limited to individuals within the same or closely related vegetative compatibility groups. Recent advances, however, allowed the establishment of experimental host ranges for a few mycoviruses. Although the majority of known mycoviruses have dsRNA genomes that are packaged in isometric particles, an increasing number of usually unencapsidated mycoviruses with positive-strand RNA genomes have been reported. We discuss selected mycoviruses that cause debilitating diseases and/or reduce the virulence of their phytopathogenic fungal hosts. Such fungal-virus systems are valuable for the development of novel biocontol strategies and for gaining an insight into the molecular basis of fungal virulence. The availability of viral and host genome sequences and of transformation and transfection protocols for some plant pathogenic fungi will contribute to progress in fungal virology.
Do Neural Cells Communicate with Endothelial Cells via Secretory Exosomes and Microvesicles?
Authors: Smalheiser Neil R.
Published: August 2009

Neurons, glial, cells, and brain tumor cells tissues release small vesicles (secretory exosomes and microvesicles), which may represent a novel mechanism by which neuronal activity could influence angiogenesis within the embryonic and mature brain. If CNS-derived vesicles can enter the bloodstream as well, they may communicate with endothelial cells in the peripheral circulation and with cells concerned with immune surveillance.