bluuebunny/crossref_metadata_2025 huggingface dataset:
Accuracy in molecular sexing of martens (Martes americana and Martes caurina) varies among sample types
Authors: CAMPBELL GRANT M. , PAULI JONATHAN N. , THOMAS JOSHUA G. , McCLEAN TERRY
Published: April 2010

We evaluated the accuracy of sex identification using the SRY marker for American marten (Martes americana) and Pacific marten (Martes caurina) using samples collected from commercial trappers and those obtained via noninvasive sampling. We determined that sex identification from Lut‐SRY primers is accurate at >90% for muscle and hair samples collected noninvasively. We found much lower accuracy when using hair samples plucked from trapper‐killed carcasses, errors presumably incurred from contamination from the DNA of trappers, who were entirely male. We also found that the sequence generated from Lut‐SRY primers, originally developed for Eurasian otters (Lutra lutra), differed slightly for martens, and recommend that new primers be developed from the sequences we provide. The SRY marker can be reliably used for sex identification in both species of marten, provided that samples have low probabilities of contamination. Researchers should avoid samples collected from external locations on trapper‐killed carcasses for DNA‐based analyses.
A newly isolated fungal strain used as whole‐cell biocatalyst for biodiesel production from palm oil
Authors: XIAO MAN , MATHEW SINI , OBBARD JEFFREY PHILIP
Published: April 2010

A strain of Aspergillus niger isolated from atmospherically exposed bread and Jatropha curcas seed was utilized as a whole‐cell biocatalyst for palm oil methanolysis to produce fatty acid methyl esters (FAME), or biodiesel. The A. niger strain had a lipase activity of 212.58 mU mL−1 after 144 h incubation at 25 °C with an initial pH value of 6.5, using 7% polypeptone (w/w on basal medium) as the nitrogen source and 3% olive oil (w/w on basal medium) as a carbon source. The A. niger cells spontaneously immobilized within polyurethane biomass support particles (BSPs) during submerged fermentation. Thereafter, the methanolysis of palm oil was achieved via a three‐step addition of methanol in the presence of BSPs‐immobilized with A. niger cells. The influence of water content, reaction temperature and enzyme concentration on reaction rate was investigated. An 8% water content and a temperature of 40 °C in the presence of 30 immobilized BSPs, resulted in an 87% FAME yield after 72 h.
1997 John P. Davis Award: The Impact of Machining Techniques on Centrifugal Compressor Impeller Performance
Authors: Childs P. R. N. , Noronha M. B.
Published: April 2010

A large proportion of modern centrifugal impellers are machined from solid forgings rather than made from cast metal. The CNC milling process offers options to manufacturers to minimize manufacturing costs while also enhancing the performance of the impeller. Efficient manufacturing can result in cutter tool marks and paths and associated roughness remaining on the hub and blade surfaces of impellers as a result of minimizing passes and maximizing the cut. The goal of manufacturers is to allow these marks to be as deep as possible to minimize machining costs, but without any negative effects on performance, and possibly even enhancing it. There are existing modeling methods that predict the influence of roughness on compressor performance using the definition of an equivalent sand grain roughness. The purpose of this study is to relate the performance directly to the tool mark characteristics that are by-products of machining, namely cusp height, cutter path roughness, and orientation of the cutter path relative to the local flow velocity, to review the current modeling techniques for predicting the influence of surface condition on compressor performance and to show the scope for optimization of manufacturing and performance considerations.
Role of Blade Passage Flow Structurs in Axial Compressor Rotating Stall Inception
Authors: Hoying D. A. , Tan C. S. , Vo Huu Duc , Greitzer E. M.
Published: April 2010

The influence of three-dimensional flow structures within a compressor blade passage has been examined computationally to determine their role in rotating stall inception. The computations displayed a short length-scale (or spike) type of stall inception similar to that seen in experiments; to the authors’ knowledge this is the first time such a feature has been simulated. A central feature observed during the rotating stall inception was the tip clearance vortex moving forward of the blade row leading edge. Vortex kinematic arguments are used to provide a physical explanation of this motion as well as to motivate the conditions for its occurrence. The resulting criterion for this type of stall inception (the movement of the tip clearance vortex forward of the leading edge) depends upon local flow phenomena related to the tip clearance with the implication that for this and possibly other stall mechanisms the flow structure within the blade passages must be addressed to explain the stability of an axial compression system that exhibits such short length-scale disturbances.
Investigation of Pre-stall Mode and Pip Inception in High-Speed Compressors Through the Use of Correlation Integral
Authors: Bright Michelle M. , Qammar Helen K. , Wang Leizhen
Published: April 2010

Five high-speed compressor configurations are used to identify pre-stall pressure signal activity under clean and distorted inlet conditions, and under steady injection and controlled injection conditions. Through the use of a nonlinear statistic called correlation integral, variations in the compressor dynamics are identified from the pre-stall pressure activity far before variations (modal or pip) are observed visually in the wall static pressure measurements. The correlation integral not only discerns changing dynamics of these compressors prior to stall, but is now used to measure the strength of the tip flow field for these five high-speed compressors. Results show that correlation integral value changes dramatically when the stall inception is modal; and it changes less severely when the stall inception is through pip disturbances. This algorithm can therefore distinguish from the pre-stall pressure traces when a machine is more likely to stall due to pips versus modes. When used in this manner, the correlation integral thus provides a measure of tip flow strength. The algorithm requires no predisposition about the expected behavior of the data in order to detect changing dynamics in the compressor; thus, no pre-filtering is necessary. However, by band-pass filtering the data, one can monitor changing dynamics in the tip flow field for various frequency regimes. An outcome of this is to associate changes in correlation integral value directly with frequency specific events occurring in the compressor, i.e., blade length scale events versus long length scale acoustic events. The correlation integral provides a potential advantage over linear spectral techniques because a single sensor is used for detection and analysis of the instabilities.
The Design of an Improved Endwall Film-Cooling Configuration
Authors: Friedrichs S. , Hodson H. P. , Dawes W. N.
Published: April 2010

The endwall film-cooling cooling configuration investigated by Friedrichs et al. (1996, 1997) had in principle sufficient cooling flow for the endwall, but in practice, the redistribution of this coolant by secondary flows left large endwall areas uncooled. This paper describes the attempt to improve upon this datum cooling configuration by redistributing the available coolant to provide a better coolant coverage on the endwall surface, while keeping the associated aerodynamic losses small. The design of the new, improved cooling configuration was based on the understanding of endwall film-cooling described by Friedrichs et al. (1996, 1997). Computational fluid dynamics were used to predict the basic flow and pressure field without coolant ejection. Using this as a basis, the above-described understanding was used to place cooling holes so that they would provide the necessary cooling coverage at minimal aerodynamic penalty. The simple analytical modeling developed by Friedrichs et al. (1997) was then used to check that the coolant consumption and the increase in aerodynamic loss lay within the limits of the design goal. The improved cooling configuration was tested experimentally in a large-scale, low-speed linear cascade. An analysis of the results shows that the redesign of the cooling configuration has been successful in achieving an improved coolant coverage with lower aerodynamic losses, while using the same amount of coolant as in the datum cooling configuration. The improved cooling configuration has reconfirmed conclusions from Friedrichs et al. (1996, 1997): First, coolant ejection downstream of the three-dimensional separation lines on the endwall does not change the secondary flow structures; second, placement of holes in regions of high static pressure helps reduce the aerodynamic penalties of platform coolant ejection; finally, taking account of secondary flow can improve the design of endwall film-cooling configurations.
Curvature Effects on Discrete-Hole Film Cooling
Authors: Berhe M. K. , Patankar S. V.
Published: April 2010

A numerical study has been conducted to investigate the effects of surface curvature on cooling effectiveness using three-dimensional film cooling geometries that included the mainflow, injection hole, and supply plenum regions. Three surfaces were considered in this study, namely, convex, concave, and flat surfaces. The fully elliptic, three-dimensional Navier–Stokes equations were solved over a body-fitted grid. The effects of streamline curvature were taken into account by using algebraic relations for the turbulent viscosity and the turbulent Prandtl number in a modified k–ε turbulence model. Computations were performed for blowing ratios of 0.5, 1.0, and 1.5 at a density ratio of 2.0. The computed and experimental cooling effectiveness results were compared. For the most part, the cooling effectiveness was predicted quite well. A comparison of the cooling performances over the three surfaces reveals that the effect of streamline curvature on cooling effectiveness is very significant. For the low blowing ratios considered, the convex surface resulted in a higher cooling effectiveness than both the flat and concave surfaces. The flow structures over the three surfaces also exhibited important differences. On the concave surface, the flow involved a stronger vorticity and greater mixing of the coolant jet with the mainstream gases. On the convex surface, the counterrotating vortices were suppressed and the coolant jet pressed to the surface by a strong cross-stream pressure gradient.
Performance Improvement Through Indexing of Turbine Airfoils: Part 1—Experimental Investigation
Authors: Huber F. W. , Johnson P. D. , Sharma O. P. , Staubach J. B. , Gaddis S. W.
Published: April 2010

This paper describes the results of a study to determine the performance improvements achievable by circumferentially indexing successive rows of turbine stator airfoils. An experimental/analytical investigation has been completed that indicates significant stage efficiency increases can be attained through application of this airfoil clocking concept. A series of tests was conducted at the National Aeronautics and Space Administration’s (NASA) Marshall Space Flight Center (MSFC) to experimentally investigate stator wake clocking effects on the performance of the Space Shuttle Main Engine Alternate Fuel Turbopump Turbine Test Article. Extensive time-accurate Computational Fluid Dynamics (CFD) simulations have been completed for the test configurations. The CFD results provide insight into the performance improvement mechanism. Part one of this paper describes details of the test facility, rig geometry, instrumentation, and aerodynamic operating parameters. Results of turbine testing at the aerodynamic design point are presented for six circumferential positions of the first stage stator, along with a description of the initial CFD analyses performed for the test article. It should be noted that first vane positions 1 and 6 produced identical first to second vane indexing. Results obtained from off-design testing of the “best” and “worst” stator clocking positions, and testing over a range of Reynolds numbers are also presented. Part two of this paper describes the numerical simulations performed in support of the experimental test program described in part one. Time-accurate Navier–Stokes flow analyses have been completed for the five different turbine stator positions tested. Details of the computational procedure and results are presented. Analysis results include predictions of instantaneous and time-average midspan airfoil and turbine performance, as well as gas conditions throughout the flow field. An initial understanding of the turbine performance improvement mechanism is described.
Multistage Turbine Simulations With Vortex–Blade Interaction
Authors: Turner M. G.
Published: April 2010

The average passage approach of Adamczyk et al. (1990) has been used to simulate the multistage environment of the General Electric E3 low-pressure turbine. Four configurations have been analyzed and compared to test data. These include the nozzle only, the first stage, the first stage and a half, and the first two stages. A high casing slope on the first-stage nozzle causes the secondary flow vortex to separate off the casing and enter the downstream rotor. The detrimental effect on performance due to this vortex interaction has been predicted by the above approach, whereas isolated blade row calculations cannot simulate this interaction. The unsteady analysis developed by Chen et al. (1994) has also been run to understand the unsteady flow field in the first-stage rotor and compare with the average passage model and test data. Comparisons of both the steady and unsteady analyses with data are generally good, although in the region near the casing of the shrouded rotors, the predicted loss is lower than that shown by the data.
Simulating the Multistage Environment for Single-Stage Compressor Experiments
Authors: Place J. M. M. , Howard M. A. , Cumpsty N. A.
Published: April 2010

The performance of a single-stage low-speed compressor has been measured both before and after the introduction of certain features of the multistage flow environment. The aim is to make the single-stage rig more appropriate for developing design rules for multistage compressors. End-wall blockage was generated by teeth on the hub and casing upstream of the rotor. A grid fitted upstream produced free-stream turbulence at rotor inlet typical of multistage machines and raised stage efficiency by 1.8 percent at the design point. The potential field that would be generated by blade rows downstream of an embedded stage was replicated by introducing a pressure loss screen at stage exit. This reduced the stator hub corner separation and increased the rotor pressure rise at flow rates below design, changing the shape of the pressure-rise characteristic markedly. These results highlight the importance of features of the flow environment that are often omitted from single-stage experiments and offer improved understanding of stage aerodynamics.
Film Cooling With Compound Angle Holes: Adiabatic Effectiveness
Authors: Schmidt D. L. , Sen B. , Bogard D. G.
Published: April 2010

Film cooling effectiveness was studied experimentally in a flat plate test facility with zero pressure gradient using a single row of inclined holes, which injected high-density, cryogenically cooled air. Round holes and holes with a diffusing expanded exit were directed laterally away from the free-stream direction with a compound angle of 60 deg. Comparisons were made with a baseline case of round holes aligned with the free stream. The effects of doubling the hole spacing to six hole diameters for each geometry were also examined. Experiments were performed at a density ratio of 1.6 with a range of blowing ratios from 0.5 to 2.5 and momentum flux ratios from 0.16 to 3.9. Lateral distributions of adiabatic effectiveness results were determined at streamwise distances from 3 D to 15 D downstream of the injection holes. All hole geometries had similar maximum spatially averaged effectiveness at a low momentum flux ratio of I = 0.25, but the round and expanded exit holes with compound angle had significantly greater effectiveness at larger momentum flux ratios. The compound angle holes with expanded exits had a much improved lateral distribution of coolant near the hole for all momentum flux ratios.
Control-Oriented Nonlinear Modeling and Temperature Control for Solid Oxide Fuel Cell
Authors: Huo Hai-Bo , Wu Yan-Xiang , Liu Yu-Qing , Gan Shi-Hong , Kuang Xing-Hong
Published: April 2010

In this paper, a variable structure controller for temperature control of the solid oxide fuel cell (SOFC) is proposed. The performance and availability of the SOFC are greatly dependent on its operating temperature. For high efficiency and low degradation of the fuel cell due to thermal cycling, the fuel cell temperature should remain fairly constant during operation. To meet the demands of developing valid control strategies, a control-oriented multi-input multi-output nonlinear thermal model of the SOFC is first developed in this paper. Then, by combining the technique of input-output linearization with variable structure control (VSC) theory, a VSC controller for temperature control is proposed. Simulation results demonstrate the correctness of the proposed control-oriented nonlinear thermal model, while the excellence of the VSC controller for temperature control in the presence of external disturbance is proved.
Local Voltage Degradations (Drying and Flooding) Analysis Through 3D Stack Thermal Modeling
Authors: Ramousse J. , Adzakpa K. P. , Dubé Y. , Agbossou K. , Fournier M. , Poulin A. , Dostie M.
Published: April 2010

Temperature is a key parameter of fuel cell efficiency. In air cooled fuel cell stacks, large temperature disparities are observed. This temperature distribution has a significant influence on cell behavior in the stack, resulting in voltage disparities. The aim of this study, thus, is to correlate the temperature distribution in the stack to local voltage degradations, such as membrane drying and electrodes flooding. Indeed, the temperature has a strong impact on the water distribution in the cells because the saturation pressure is thermo-dependent. As a result, the hottest cells are prone to drying, whereas the coolest cells tend to be flooded, depending on the operating conditions. Measurements show that while drying, cell voltages decrease slowly and continuously until complete shutdown of the cells, whereas flooding results in quick voltage drops. Under drying conditions, voltage can be improved by increasing the inlet gas humidity or decrease in the stoichiometric ratio. In the case of flooding cells, purging the stack or reducing the inlet gas humidity is necessary to avoid complete shutdown of the cells. Consequently, small cell temperature variations through the stack can be responsible for large voltage variations from one cell to another. The cooling device must thus be optimized to reduce stack temperature nonuniformity.
Electroless Deposition and Characterization of PtxRu1−x Catalysts on Pt/C Nanoparticles for Methanol Oxidation
Authors: Mustain William E. , Kim Hyea , Narayanan Vijai , Osborn Tyler , Kohl Paul A.
Published: April 2010

The electroless deposition of PtxRu1−x catalysts using hydrazine dihydrochloride or formic acid as the reducing agent in a modified Leaman bath was investigated. The effect of potential on the PtxRu1−x composition was investigated by potentiostatically depositing PtxRu1−x thin films on gold from acidic chloride electrolytes at potentials between −0.46 V and 0.34 V (versus normal hydrogen electrode). The physical characteristics and elemental composition of the deposits were determined. An empirical model for the deposition process was developed, taking into account reactant concentration, temperature, and surface potential. The model accurately characterized the deposit composition over a wide Pt/Ru range. The surface potential was estimated to be 0.15 V during electroless deposition using formic acid as the reducing agent based on the empirical model. Deviations from the model were found when hydrazine was used as the reducing agent due to the formation of solution phase ruthenium complexes with hydrazine.
A Finite Volume SOFC Model for Coal-Based Integrated Gasification Fuel Cell Systems Analysis
Authors: Li Mu , Powers James D. , Brouwer Jacob
Published: April 2010

Integrated gasification fuel cell (IGFC) systems combining coal gasification and solid oxide fuel cells (SOFC) are promising for highly efficient and environmentally friendly utilization of coal for power production. Most IGFC system analyses performed to-date have used nondimensional thermodynamic SOFC models that do not resolve the intrinsic constraints of SOFC operation. In this work a quasi-two-dimensional (2D) finite volume model for planar SOFC is developed and verified using literature data. Special attention is paid to making the model capable of supporting recent SOFC technology improvements, including the use of anode-supported configurations, metallic interconnects, and reduced polarization losses. Activation polarization parameters previously used for high temperature electrolyte-supported SOFC result in cell performance that is much poorer than that observed for modern intermediate temperature anode-supported configurations; thus, a sensitivity analysis was conducted to identify appropriate parameters for modern SOFC modeling. Model results are shown for SOFC operation on humidified H2 and CH4 containing syngas, under coflow and counterflow configurations; detailed internal profiles of species mole fractions, temperature, current density, and electrochemical performance are obtained. The effects of performance, fuel composition, and flow configuration of SOFC performance and thermal profiles are evaluated, and the implications of these results for system design and analysis are discussed. The model can be implemented not only as a stand-alone SOFC analysis tool, but also a subroutine that can communicate and cooperate with chemical flow sheet software seamlessly for convenient IGFC system analysis.
Evaluation of the Performance Characteristics of a Direct Methanol Fuel Cell With Multifuels
Authors: Mohan Sujith , Bade Shrestha S. O.
Published: April 2010

Direct methanol fuel cells are one of the alternate power sources for the field of power electronics because of their high energy density. The benefits of a fuel cell toward the environment can be greatly improved if the fuel used for its application comes from renewable sources. In this study, the performance of a direct methanol fuel cell was investigated under five different methanol concentrations. The effect of methanol concentration on the cell operating temperature is studied. Impedance spectroscopy was conducted to measure the ohmic, activation, and mass transport losses for all concentrations. The cell performance was evaluated using methane and ethanol fuels and this was compared with methanol operation.
An articulated embolomere skeleton (Amphibia: Anthracosauria) from the Lower Pennsylvanian (Bashkirian) of Nova Scotia
Authors: Holmes Robert B. , Carroll Robert L.
Published: April 2010

Recently discovered skeletal material greatly expands our knowledge of the embolomeres from the Early Pennsylvanian locality of Joggins, Nova Scotia. These specimens are probably attributable to Calligenethlon watsoni Steen that has been described previously from this locality, but despite their articulated condition and relative completeness, this assignment is equivocal. Inclusion of the most complete specimen, NSM 994 GF 1.1, in a previous phylogenetic analysis of the Embolomeri results in a sistergroup relationship between NSM 994 GF 1.1 and Anthracosaurus . However, none of the 16 synapomorphies supporting this relationship are unique to these two taxa, but rather all occur in one or more of the other taxa in the analysis. This indicates extensive homoplasy within embolomeres and emphasizes the difficulties inherent in resolving embolomere interrelationships. The dirth of unequivocal synapomorphies is probably also reflects the conservative nature and basal status of embolomeres within the initial Palaeozoic tetrapod radiation.
An Ordovician “Lost City” — venting serpentinite and life oases on Iapetus seafloor
Authors: Lavoie Denis , Chi Guoxiang
Published: April 2010

Highly brecciated carbonate-rich serpentinites (or ophicalcites) of Early Ordovician age in the Dunnage Zone of Quebec are host to fracture-fill, high-temperature (80–230 °C) carbonate cements. Away from, or crosscut by the fractures, centimetre- to decimetre-thick crusts made up of massive to laminated micrite, peloidal layers and threads are associated with low-temperature botryoidal calcite cements. The peloidal masses are characterized by a clotted texture that is reminiscent of interpreted fossilized Ordovician microbial communities. The ophicalcite contains carbonate botryoids, morphology commonly found at shallow reefal margins but also at modern cold CH4 seeps and recently documented at hot CH4 vents from serpentinite, such as the modern Lost City hydrothermal field in the Atlantic Ocean. The δ18OVPDB ratios of the calcite botryoids and peloidal layers indicate formation and (or) precipitation out of cold Ordovician deep-marine waters. To the contrary of botryoids at cold methane seeps, the botryoids associated with the modern and Ordovician hot vents do not show the negative δ13CVPDB ratios indicative of microbial isotopic fractionation. Therefore, any microbial-derived HCO3– has been overwhelmed by the isotopically heavier marine-derived carbon during the open-system diagenesis. Carbonate-rich serpentinites should be carefully revisited in the search for evidence of microbial life in the Precambrian, as the negative δ13CVPDB ratios used as fingerprints of biological activity are not always reliable.
A note on the relationship between estimates of heritability and type-B genetic correlation
Authors: Lu Pengxin
Published: April 2010

This note verifies the applicability of an approach derived from Adams et al. (W.T. Adams, T.L. White, G.R. Hodge, and G.L. Powell. 1994. Silvae Genet. 43: 357–366) that used the ratio of unbiased to biased heritability estimates (denoted by Rh) to approximate type-B genetic correlation (rB) estimates. Both theoretical evidence and empirical evidence suggest that the estimate of the ratio of unbiased to biased heritability is often a good approximation of the estimate of type-B genetic correlation under the assumption of homogeneous heritability among sites. Given the large sampling errors and often unstable estimates of rB, the approach concerned may provide an alternative to existing methods for estimating type-B genetic correlation.
Phenolic metabolites in the resistance of northern forest trees to pathogens — past experiences and future prospects
Authors: Witzell Johanna , Martín Juan A.
Published: April 2010

Phenolic metabolites are frequently implicated in chemical defense mechanisms against pathogens in woody plants. However, tree breeding programmes for resistance to pathogens and practical tree-protection applications based on these compounds seem to be scarce. To identify gaps in our current knowledge of this subject, we explored some of the recent literature on the involvement of phenolic metabolites in the resistance of northern forest trees (Pinus, Picea, Betula, Populus, and Salix spp.) to pathogens. Although it is evident that the phenolic metabolism of trees is often activated by pathogen attacks, few studies have convincingly established that this induction is due to a specific defense response that is capable of stopping the invading pathogen. The role of constitutive phenolics in the resistance of trees to pathogens has also remained unclear. In future studies, the importance of phenolics in oxidative stress, cell homeostasis and tolerance, and the spatial and temporal localization of phenolics in relation to invading pathogens should be more carefully acknowledged. Possibilities for future studies using advanced methods (e.g., metabolic profiling, confocal laser scanning microscopy, and use of modified tree genotypes) are discussed.
Balanced forest tree improvement can be enhanced by selecting among many parents but maintaining balance among grandparents
Authors: Lindgren Dag , Danusevičius Darius , Rosvall Ola
Published: April 2010

A model for a balanced tree breeding program that considers genetic gain and cost was used to assess the benefits of increasing the breeding population to allow for a component of among-parent selection while maintaining an equal contribution among grandparents, rather than relaying on within-family selection with an equal parental representation. The scenario used in this study had characteristics similar to those of the phenotypic selection strategy for Scots pine ( Pinus sylvestris L.) in Sweden. The results showed that investments in a greater number of parents and families to allow for among-parent selection resulted in a markedly higher genetic gain. The among-parent selection component increased the genetic gain by as much as 70% in a scenario with a high budget and no family creation costs and by as much as 20% in a scenario with a low budget and high family creation costs.
Demographic and behavioural response of woodland caribou to forest harvesting
Authors: Courtois Réhaume , Gingras André , Fortin Daniel , Sebbane Aïssa , Rochette Bruno , Breton Laurier
Published: April 2010

We investigated whether woodland caribou ( Rangifer tarandus caribou ) would remain in a 2772 km2 area in eastern Quebec where the forest management plan included the preservation of large forest blocks (35–182 km2) linked with >400 m wide corridors and where cuts were amalgamated in large zones. To evaluate changes in caribou abundance and habitat selection, we conducted five aerial surveys and followed by telemetry 13 to 22 female caribou each year, from March 1998 to March 2005. Caribou numbers declined by 59% between 1999 and 2001 but gradually recovered to initial abundance. Female survival increased from 73.3% in 1999 to 87.3%–93.4% in 2004 and 2005. Caribou selected protected blocks, used corridors in proportion to their availability, and avoided logged areas. They preferred closed conifer stands without terrestrial lichens and open conifer stands with or without terrestrial lichens throughout the study. Open habitats (clearcuts and burns), regenerating sites, mixed and deciduous stands, and water bodies were avoided. The main zones used by caribou gradually shifted towards the southwest of the study area, likely as a result of disturbance and habitat loss due to logging of mature conifers in the east. We conclude that caribou numbers were maintained within the managed area as a result of the presence of protected blocks and uncut continuous forest.
Effect of thinning on relationships between three measures of wood stiffness in Pinus radiata: standing trees vs. logs vs. short clear specimens
Authors: Raymond Carolyn A. , Joe Bill , Anderson Dean W. , Watt Duncan J.
Published: April 2010

The effect of thinning on the relationship of wood quality traits measured on standing trees (dynamic modulus of elasticity (MOE) and outerwood density) and traits measured on logs or short clear specimens was determined using data collected from radiata pine ( Pinus radiata D. Don) trees growing in 22 unthinned and 16 thinned plots of harvest age trees in New South Wales, Australia. Stiffness showed a linear decrease along the stem. Trees growing on thinned sites were, on average, 3% lower in stiffness at each height in the stem. MOE measured on short clear specimens was moderately related to standing tree MOE (R2 = 0.62) and outerwood density (R2 = 0.56) but less well related to MOE of the adjacent log (R2 = 0.30). Standing tree MOE was a better predictor of whole stem MOE for the thinned sites (R2 = 0.60) than for the unthinned sites (R2 = 0.31). Stiffness and density appear to follow different patterns of variation and results for density may not be extrapolated to stiffness. Outerwood density was a very poor predictor of mean whole stem stiffness (R2 = 0.14). Overall, the acoustic tool, TreeTap, was a better predictor of whole stem stiffness than outerwood density, particularly for the thinned sites.
Identifying roots of northern hardwood species: patterns with diameter and depth
Authors: Yanai Ruth D. , Fisk Melany C. , Fahey Timothy J. , Cleavitt Natalie L. , Park Byung B.
Published: April 2010

Forest canopies are often stratified by species; little is known about the depth distribution of tree roots in mixed stands because they are not readily identified by species. We used diagnostic characteristics of wood anatomy and gross morphology to distinguish roots by species and applied these methods to test for differences in the rooting depth of sugar maple ( Acer saccharum Marsh.), American beech ( Fagus grandifolia Ehrh.), and yellow birch ( Betula alleghaniensis Britt.) in two northern hardwood forests. We also distinguished hobblebush ( Viburnum lantanoides Michx.) and white ash ( Fraxinus americana L.) roots. Analysis of plastid DNA fragment lengths confirmed that 90% of the roots were correctly identified. The vertical distribution of fine roots of these species differed by 2–4 cm in the median root depth (P = 0.03). There was a significant difference in the distribution of roots by size class, with fine roots (0–2 mm) being more concentrated near the soil surface than coarser roots (2–5 mm; P = 0.004). The two sites differed by <2 cm in median rooting depths (P = 0.02). The visual identification of roots for the main tree species in the northern hardwood forest allows species-specific questions to be posed for belowground processes.
Intense forest wildfire sharply reduces mineral soil C and N: the first direct evidence
Authors: Bormann Bernard T. , Homann Peter S. , Darbyshire Robyn L. , Morrissette Brett A.
Published: April 2010

Direct evidence of the effects of intense wildfire on forest soil is rare because reliable prefire data are lacking. By chance, an established large-scale experiment was partially burned in the 2002 Biscuit fire in southwestern Oregon. About 200 grid points were sampled across seven burned and seven unburned stands before and after the fire. Fire-related soil changes — including losses of soil organic and inorganic matter — were so large that they became complicated to measure. The 51 Mg·ha–1 of loose rocks on the soil surface after fire suggests erosion of 127 Mg·ha–1 of fine mineral soil, some of which likely left in the fire plume. After accounting for structural changes and erosion with a comparable-layers approach, combined losses from the O horizon and mineral soil totaled 23 Mg C·ha–1 and 690 kg N·ha–1, of which 60% (C) and 57% (N) were lost from mineral horizons. Applying a fixed-depth calculation — commonly used in previous fire studies — that disregards structural changes and erosion led to underestimates of loss of nearly 50% for C and 25% for N. Although recent debate has centered on the effects of postwildfire forest management on wood, wildlife habitat, and fuels, this study indicates that more consideration should be given to the possible release of greenhouse gases and reduction of future forest productivity and CO2 uptake.
HOW FAR IS AN ELEMENT FROM BEING PRIME?
Authors: ANDERSON DAVID F. , CHAPMAN SCOTT T.
Published: April 2010

Let D be an integral domain. We investigate two invariants ω(D, x) and ω(D) which measure how far an x ∈ D is from being prime and how far an atomic integral domain D is from being a UFD, respectively. We give a new characterization of number fields with class number two. We also study asymptotic versions of these two invariants.
CLASSIFICATION OF SUBALGEBRAS OF THE CAYLEY ALGEBRA OVER A FINITE FIELD
Authors: GRISHKOV ALEXANDER N. , GIULIANI MARIA DE LOURDES MERLINI , ZAVARNITSINE ANDREI V.
Published: April 2010

We classify all unital subalgebras of the Cayley algebra 𝕆(q) over the finite field Fq, q = pn. We obtain the number of subalgebras of each type and prove that all isomorphic subalgebras are conjugate with respect to the automorphism group of 𝕆(q). We also determine the structure of the Moufang loops associated with each subalgebra of 𝕆(q).
A COMPLEX VARIABLE MESHLESS MANIFOLD METHOD FOR FRACTURE PROBLEMS
Authors: GAO HONGFEN , CHENG YUMIN
Published: April 2010

Based on the complex variable moving least-squares (CVMLS) approximation and the finite cover theory, the complex variable meshless manifold method (CVMMM) for fracture problems is presented in this paper. The CVMMM employs two cover systems which are the mathematical cover system and the physical cover system. The shape function in the CVMMM is derived with the CVMLS approximation and the finite cover theory. The finite cover theory is used to model cracks which lead to interior discontinuous displacements. At the tip of a crack of a problem, we use the analytical solution near the tip of a crack to extend the trial function of the CVMMM, then the corresponding approximation function is obtained. From the minimum potential energy principle, the corresponding formulae of the CVMMM for fracture problems are presented. Some numerical examples are presented to demonstrate the method in this paper.
DEVELOPMENT OF 3D NUMERICAL MANIFOLD METHOD
Authors: HE LEI , MA GUOWEI
Published: April 2010

The numerical manifold method (NMM) is a combination of the finite element method (FEM) and discontinuous deformation analysis (DDA) method. It provides a robust numerical solution to a solid medium with dense discontinuities. This paper extends NMM to the three-dimensional domain based on the 2D fundamentals. The general framework of the 3D NMM is introduced, including the cover geometry patterns (GP) with division structure from hexahedron to tetrahedron, and general formulations based on the virtual work principle. The block cutting process to generate discrete blocks are discussed through the topological structure description of blocks, and the operation rule of blocks is explained. The proposed 3D block generation algorithm allows for any arbitrary discrete structure or block system. Three numerical examples are presented to demonstrate that the developed 3D numerical manifold code is effective and applicable to 3D continuum solids. Further developments aim to incorporate contact models to simulate complicated discrete block system.
A NOVEL GENERAL FORMULATION FOR SINGULAR STRESS FIELD USING THE ES-FEM METHOD FOR THE ANALYSIS OF MIXED-MODE CRACKS
Authors: LIU G. R. , NOURBAKHSHNIA N. , CHEN L. , ZHANG Y. W.
Published: April 2010

This paper presents a general formulation for simulating the singular stress field at the vicinity of the crack-tip for linear fracture mechanics problems, based on the edge-based smoothed finite element method (ES-FEM) settings. This novel "singular ES-FEM" makes use of the unique feature offered by the ES-FEM that only the assumed displacement values (not the derivatives) are required to compute the stiffness matrix of the discretized system. The present singular ES-FEM method uses a basic mesh of linear triangular elements and a layer of novel "five-noded crack-tip elements" sharing the crack-tip node. The five-noded crack-tip element has one additional node on each of the edges connected to the crack-tip, and the locations of the "edge-node" can be arbitrary. A number of examples are analyzed and the results demonstrate that the present singular ES-FEM is generally softer and much more accurate than the existing FEM. The stress intensity factors obtained using the singular ES-FEM are very stable for different area-integration paths designed around the crack-tip. The present singular ES-FEM is found an excellent alternative to the standard FEM for fracture problems.
An improved analysis of the lossy difference aggregator
Authors: Finucane Hilary , Mitzenmacher Michael
Published: April 2010

We provide a detailed analysis of the Lossy Difference Aggregator, a recently developed data structure for measuring latency in a router environment where packet losses can occur. Our analysis provides stronger performance bounds than those given originally, and leads us to a model for how to optimize the parameters for the data structure when the loss rate is not known in advance by using competitive analysis.
Dummynet revisited
Authors: Carbone Marta , Rizzo Luigi
Published: April 2010

Dummynet is a widely used link emulator, developed long ago to run experiments in user-configurable network environments. Since its original design, our system has been extended in various ways, and has become very popular in the research community due to its features and to the ability to emulate even moderately complex network setups on unmodified operating systems.

We have recently made a number of extensions to the emulator, including loadable packet schedulers, support for better MAC layer modeling, the inclusion in PlanetLab, and development of Linux and Windows versions in addition to the native FreeBSD and OS X ones.

The goal of this paper is to present in detail the current features of Dummynet, compare it with other emulation solutions, and discuss what operating conditions should be considered and what kind of accuracy to expect when using an emulation system.
Fighting online click-fraud using bluff ads
Authors: Haddadi Hamed
Published: April 2010

Online advertising is currently the richest source of revenue for many Internet giants. The increased number of online businesses, specialized websites and modern profiling techniques have all contributed to an explosion of the income of ad brokers from online advertising. The single biggest threat to this growth, is however, click-fraud. Trained botnets and individuals are hired by click-fraud specialists in order to maximize the revenue of certain users from the ads they publish on their websites, or to launch an attack between competing businesses.

In this note we wish to raise the awareness of the networking research community on potential research areas within the online advertising field. As an example strategy, we present Bluff ads; a class of ads that join forces in order to increase the effort level for click-fraud spammers. Bluff ads are either targeted ads, with irrelevant display text, or highly relevant display text, with irrelevant targeting information. They act as a litmus test for the legitimacy of the individual clicking on the ads. Together with standard threshold-based methods, fake ads help to decrease click-fraud levels.
Dynamic route recomputation considered harmful
Authors: Caesar Matthew , Casado Martin , Koponen Teemu , Rexford Jennifer , Shenker Scott
Published: April 2010

This paper advocates a different approach to reduce routing convergence--side-stepping the problem by avoiding it in the first place! Rather than recomputing paths after temporary topology changes, we argue for a separation of timescale between offline computation of multiple diverse paths and online spreading of load over these paths. We believe decoupling failure recovery from path computation leads to networks that are inherently more efficient, more scalable, and easier to manage.
Evolvable network architectures
Authors: Dovrolis Constantine , Streelman J. Todd
Published: April 2010

There is significant research interest recently to understand the evolution of the current Internet, as well as to design clean-slate Future Internet architectures. Clearly, even when network architectures are designed from scratch, they have to evolve as their environment (i.e., technological constraints, service requirements, applications, economic conditions, etc) always changes. A key question then is: what makes a network architecture evolvable? What determines the ability of a network architecture to evolve as its environment changes? In this paper, we review some relevant ideas about evolvability from the biological literature. We examine the role of robustness and modularity in evolution, and their relation with evolvability. We also discuss evolutionary kernels and punctuated equilibria, two important concepts that may be relevant to the so-called ossification of the core Internet protocols. Finally, we examine optimality, a design objective that is often of primary interest in engineering but that does not seem to be abundant in biology.
Developing Moral Agency through Narrative
Authors: Pasupathi Monisha , Wainryb Cecilia
Published: April 2010

This paper poses the following question: When, in spite of knowing that it is wrong, people go on to hurt others, what does this mean for the development of moral agency? We begin by defining moral agency and briefly sketching relations between moral agency and other concepts. We then outline what three extant literatures suggest about this question: social domain theory, moral intuitionist theories, and theories of moral identity development. Building on these literatures, but moving beyond them, we propose that experiences of harming others are catalysts for the development of what we term moral agency. In the remainder of the paper, we outline a model for how moral agency develops that draws on research about the narrative development of self. We close by outlining some of the critical directions for future work that are suggested by our approach.
Prevalence and Etiology of Hearing Loss in Primary and Middle School Students in the Hubei Province of China
Authors: Fu Siqing , Chen Guanming , Dong Jiashu , Zhang Ling
Published: April 2010

The purpose of this study was to investigate the prevalence and etiology of hearing loss in primary and middle school students in the Hubei province of China. During a 2-year period, 504348 students were examined by a speech audiometry test, and 813 deaf students were detected. Among the 813 deaf students, 232 cases were diagnosed with congenital deafness and 560 cases had acquired deafness, among which 276 cases had aminoglycoside-antibiotic-induced deafness. The severity of deafness could be further ascertained in 804 other students, with 402 profound, 363 severe, 21 moderate and 18 mild deafness cases. The age at deafness onset of most students was under 3 years. The prevalence of congenital and acquired deafness was 0.046% (232/504348) and 0.111% (560/504348), respectively, much lower than previously reported in other regions of China. Furthermore, the genetic factor was identified as one of the principal causes of deafness by pedigree analysis.
Clinical Efficacy of Highly Purified hMG versus Recombinant FSH in IVF/ICSI Cycles: A Meta-Analysis
Authors: Jee Byung Chul , Suh Chang Suk , Kim Yong Beom , Kim Seok Hyun , Moon Shin Yong
Published: April 2010

Background/Aims: To compare the effectiveness of highly purified hMG (Menopur) with recombinant FSH (Gonal-F) in IVF/ICSI patients who underwent ovarian hyperstimulation with pituitary suppression. Methods: A literature search of the National Library of Medicine and the National Institutes of Health (PubMed), Medline and Cochrane Controlled Trials Register was performed using the key words ‘highly purified hMG’ and ‘recombinant FSH.’ Only prospective randomized controlled trials were included when they compared IVF/ICSI outcomes after administration of Menopur versus Gonal-F. Five studies met the inclusion criteria and were reviewed. The primary outcome measure was ongoing pregnancy/live birth. Results: Ongoing pregnancy rate per started cycle (RR: 1.10, 95% CI: 0.96–1.26) or per embryo transfer (RR: 1.13, 95% CI: 0.99–1.29), as well as live birth rate per embryo transfer (RR: 1.14, 95% CI: 0.98–1.33), is similar between the Menopur and the Gonal-F group. Conclusion: The combined data presented in this meta-analysis do not support a clinical superiority of Gonal-F over Menopur.