bluuebunny/crossref_metadata_2025 huggingface dataset:
The Role of Tip Leakage Vortex Breakdown in Compressor Rotor Aerodynamics
Authors: Furukawa M. , Inoue M. , Saiki K. , Yamada K.
Published: March 2010

The breakdown of tip leakage vortex has been investigated on a low-speed axial compressor rotor with moderate blade loading. Effects of the breakdown on the rotor aerodynamics are elucidated by Navier–Stokes flow simulations and visualization techniques for identifying the breakdown. The simulations show that the leakage vortex breakdown occurs inside the rotor at a lower flow rate than the peak pressure rise operating condition. The breakdown is characterized by the existence of the stagnation point followed by a bubblelike recirculation region. The onset of breakdown causes significant changes in the nature of the tip leakage vortex: large expansion of the vortex and disappearance of the streamwise vorticity concentrated in the vortex. The expansion has an extremely large blockage effect extending upstream of the leading edge. The disappearance of the concentrated vorticity results in no rolling-up of the vortex downstream of the rotor and the disappearance of the pressure trough on the casing. The leakage flow field downstream of the rotor is dominated by the outward radial flow, resulting from the contraction of the bubblelike structure of the breakdown region. It is found that the leakage vortex breakdown plays a major role in characteristic of rotor performance at near-stall conditions. As the flow rate is decreased from the peak pressure rise operating condition, the breakdown region grows rapidly in the streamwise, spanwise, and pitchwise directions. The growth of the breakdown causes the blockage and the loss to increase drastically. Then, the interaction of the breakdown region with the blade suction surface gives rise to the three-dimensional separation of the suction surface boundary layer, thus leading to a sudden drop in the total pressure rise across the rotor.
Endwall Blockage in Axial Compressors
Authors: Khalid S. A. , Khalsa A. S. , Waitz I. A. , Tan C. S. , Greitzer E. M. , Cumpsty N. A. , Adamczyk J. J. , Marble F. E.
Published: March 2010

This paper presents a new methodology for quantifying compressor endwall blockage and an approach, using this quantification, for defining the links between design parameters, flow conditions, and the growth of blockage due to tip clearance flow. Numerical simulations, measurements in a low-speed compressor, and measurements in a wind tunnel designed to simulate a compressor clearance flow are used to assess the approach. The analysis thus developed allows predictions of endwall blockage associated with variations in tip clearance, blade stagger angle, inlet boundary layer thickness, loading level, loading profile, solidity, and clearance jet total pressure. The estimates provided by this simplified method capture the trends in blockage with changes in design parameters to within 10 percent. More importantly, however, the method provides physical insight into, and thus guidance for control of, the flow features and phenomena responsible for compressor endwall blockage generation.
Rotating Stall Control in a High-Speed Stage With Inlet Distortion: Part II—Circumferential Distortion
Authors: Spakovszky Z. S. , van Schalkwyk C. M. , Weigl H. J. , Paduano J. D. , Suder K. L. , Bright M. M.
Published: March 2010

This paper presents the first attempt to stabilize rotating stall in a single-stage transonic axial flow compressor with inlet distortion using active feedback control. The experiments were conducted at the NASA Lewis Research Center on a single-stage transonic core compressor inlet stage. An array of 12 jet injectors located upstream of the compressor was used for forced response testing and feedback stabilization. Results for a circumferential total pressure distortion of about one dynamic head and a 120 deg extent (DC(60) = 0.61) are reported in this paper. Part I (Spakovszky et al., 1999) reports results for radial distortion. Control laws were designed using empirical transfer function estimates determined from forced response results. Distortion introduces coupling between the harmonics of circumferential pressure perturbations, requiring multivariable identification and control design techniques. The compressor response displayed a strong first spatial harmonic, dominated by the well-known incompressible Moore–Greitzer mode. Steady axisymmetric injection of 4 percent of the compressor mass flow resulted in a 6.2 percent reduction of stalling mass flow. Constant gain feedback, using unsteady asymmetric injection, yielded a further range extension of 9 percent. A more sophisticated robust H∞ controller allowed a reduction in stalling mass flow of 10.2 percent relative to steady injection, yielding a total reduction in stalling mass flow of 16.4 percent.
Effects of Bulk Flow Pulsations on Film Cooling From Different Length Injection Holes at Different Blowing Ratios
Authors: Seo H. J. , Lee J. S. , Ligrani P. M.
Published: March 2010

Bulk flow pulsations in the form of sinusoidal variations of velocity and static pressure at injectant Strouhal numbers from 0.8 to 10.0 are investigated as they affect film cooling from a single row of simple angle holes. Similar flow variations are produced by potential flow interactions and passing shock waves near turbine surfaces in gas turbine engines. Time-averaged temperature distributions, phase-averaged temperature distributions, adiabatic film cooling effectiveness values, and iso-energetic Stanton numbers show that important alterations to film cooling protection occur as pulsation frequency, coolant Strouhal number, blowing ratio, and nondimensional injection hole length are changed. Overall, the pulsations affect film performance and behavior more significantly both as L/D decreases, and as blowing ratio decreases.
Turbulence Spectra and Length Scales Measured in Film Coolant Flows Emerging From Discrete Holes
Authors: Burd S. W. , Simon T. W.
Published: March 2010

To date, very little attention has been devoted to the scales and turbulence energy spectra of coolant exiting from film cooling holes. Length-scale documentation and spectral measurements have primarily been concerned with the free-stream flow with which the coolant interacts. Documentation of scales and energy decomposition of the coolant flow leads to more complete understanding of this important flow and the mechanisms by which it disperses and mixes with the free stream. CFD modeling of the emerging flow can use these data as verification that flow computations are accurate. To address this need, spectral measurements were taken with single-sensor, hot-wire anemometry at the exit plane of film cooling holes. Energy spectral distributions and length scales calculated from these distributions are presented for film cooling holes of different lengths and for coolant supply plenums of different geometries. Measurements are presented on the hole streamwise centerline at the center of the hole, one-half diameter upstream of center, and one-half diameter downstream of center. The data highlight some fundamental differences in energy content, dominant frequencies, and scales with changes in the hole and plenum geometries. Coolant flowing through long holes exhibits smoothly distributed spectra as might be anticipated in fully developed tube flows. Spectra from short-hole flows, however, show dominant frequencies.
Heat Transfer and Flowfield Measurements in the Leading Edge Region of a Stator Vane Endwall
Authors: Kang M. B. , Kohli A. , Thole K. A.
Published: March 2010

The leading edge region of a first-stage stator vane experiences high heat transfer rates, especially near the endwall, making it very important to get a better understanding of the formation of the leading edge vortex. In order to improve numerical predictions of the complex endwall flow, benchmark quality experimental data are required. To this purpose, this study documents the endwall heat transfer and static pressure coefficient distribution of a modern stator vane for two different exit Reynolds numbers (Reex = 6 × 105 and 1.2 × 106). In addition, laser-Doppler velocimeter measurements of all three components of the mean and fluctuating velocities are presented for a plane in the leading edge region. Results indicate that the endwall heat transfer, pressure distribution, and flowfield characteristics change with Reynolds number. The endwall pressure distributions show that lower pressure coefficients occur at higher Reynolds numbers due to secondary flows. The stronger secondary flows cause enhanced heat transfer near the trailing edge of the vane at the higher Reynolds number. On the other hand, the mean velocity, turbulent kinetic energy, and vorticity results indicate that leading edge vortex is stronger and more turbulent at the lower Reynolds number. The Reynolds number also has an effect on the location of the separation point, which moves closer to the stator vane at lower Reynolds numbers.
Fluid Flow in a 180 deg Sharp Turning Duct With Different Divider Thicknesses
Authors: Liou Tong-Miin , Tzeng Yaw-Yng , Chen Chung-Chu
Published: March 2010

The effect of divider thickness on fluid flows in a two-pass smooth square duct with a 180 deg straight-corner turn is an important issue to the turbine blade internal cooling but has not been explored in the past. Laser-Doppler velocimetry measurements are thus presented for such a study at a Reynolds number of 1.2 × 104 and dimensionless divider thicknesses (Wd*) of 0.10, 0.25, 0.50. Results are presented in terms of various mean velocity components in two orthogonal streamwise planes and three cross-sectional planes, the local and regional averaged turbulent kinetic energy and resultant mean velocity distributions, and complemented by the liquid crystal measured heat transfer coefficient contours. The measured velocity data are able reasonably to explain published and present measured heat transfer results. Wd* is found to have profound effects on the flow features inside and immediately after the turn. The turbulence level and uniformity in the region immediately after the turn respectively decrease and increase with increasing Wd*.
Dynamics of Large-Scale Structures for Jets in a Crossflow
Authors: Muldoon F. , Acharya S.
Published: March 2010

Results of a three-dimensional unsteady computational study of a row of jets injected normal to a crossflow are presented with the aim of understanding the dynamics of the large-scale structures in the region near the jet. The jet to crossflow velocity ratio is 0.5. A modified version of the computer program (INS3D), which utilizes the method of artificial compressibility, is used for the computations. Results obtained clearly indicate that the near-field large-scale structures are extremely dynamic in nature, and undergo breakup and reconnection processes. The dynamic near-field structures identified include the counterrotating vortex pair (CVP), the horseshoe vortex, wake vortex, wall vortex, and shear layer vortex. The dynamic features of these vortices are presented in this paper. The CVP is observed to be a convoluted structure interacting with the wall and horseshoe vortices. The shear layer vortices are stripped by the crossflow, and undergo pairing and stretching events in the leeward side of the jet. The wall vortex is reoriented into the upright wake system. Comparison of the predictions with mean velocity measurements is made. Reasonable agreement is observed.
A Prediction Model for Separated-Flow Transition
Authors: Hatman A. , Wang T.
Published: March 2010

The present study formulates an improved approach for analyzing separated-flow transition that differentiates between the transition process in boundary layers that are laminar at separation and those that are already transitional at separation. The paper introduces new parameters that are necessary in classifying separated-flow transition modes and in accounting for the concomitant evolution of transition in separated shear layer and the average effect of periodic separation bubble build-up and vortex shedding. At least three separated-flow transition modes are positively distinguished: (a) transitional separation, with the transition starting upstream of the separation point and developing mostly as natural transition, (b) laminar separation/short bubble mode, with the onset of transition induced downstream of the separation point by inflexional instability and with a quick transition completion, and (c) laminar separation/long bubble mode, with the onset of transition also induced downstream of the separation point by inflexional instability, and with the transition completion delayed. Passing from one mode to another takes place continuously through a succession of intermediate stages. The location of maximum bubble elevation has been proved to be the controlling parameter for the separated flow behavior. It was found that, downstream of the separation point, the experimental data expressed in terms of distance Reynolds number Rex can be correlated better than momentum or displacement thickness Reynolds number. For each mode of separated-flow transition, the onset of transition, the transition length, and separated flow general characteristic are determined. This prediction model is developed mainly on low free-stream turbulence flat plate data and limited airfoil data. Extension to airfoils and high turbulence environment requires additional study.
Bioprinting Endothelial Cells With Alginate for 3D Tissue Constructs
Authors: Khalil Saif , Sun Wei
Published: March 2010

Advanced solid freeform fabrication (SFF) techniques have been an interest for constructing tissue engineered polymeric scaffolds because of its repeatability and capability of high accuracy in fabrication resolution at the scaffold macro- and microscales. Among many important scaffold applications, hydrogel scaffolds have been utilized in tissue engineering as a technique to confide the desired proliferation of seeded cells in vitro and in vivo into its architecturally porous three-dimensional structures. Such fabrication techniques not only enable the reconstruction of scaffolds with accurate anatomical architectures but also enable the ability to incorporate bioactive species such as growth factors, proteins, and living cells. This paper presents a bioprinting system designed for the freeform fabrication of porous alginate scaffolds with encapsulated endothelial cells. The bioprinting fabrication system includes a multinozzle deposition system that utilizes SFF techniques and a computer-aided modeling system capable of creating heterogeneous tissue scaffolds. The manufacturing process is biologically compatible and is capable of functioning at room temperature and relatively low pressures to reduce the fluidic shear forces that could deteriorate biologically active species. The deposition system resolution is 10 μm in the three orthogonal directions XYZ and has minimum velocity of 100 μm/s. The ideal concentrations of sodium alginate and calcium chloride were investigated to determine a viable bioprinting process. The results indicated that the suitable fabrication parameters were 1.5% (w/v) sodium alginate and 0.5% (w/v) calcium chloride. Degradation studies via mechanical testing showed a decrease in the elastic modulus by 35% after 3 weeks. Cell viability studies were conducted on the cell encapsulated scaffolds for validating the bioprinting process and determining cell viability of 83%. This work exhibits the potential use of accurate cell placement for engineering complex tissue regeneration using computer-aided design systems.
A Computationally Efficient Formal Optimization of Regional Myocardial Contractility in a Sheep With Left Ventricular Aneurysm
Authors: Sun Kay , Stander Nielen , Jhun Choon-Sik , Zhang Zhihong , Suzuki Takamaro , Wang Guan-Ying , Saeed Maythem , Wallace Arthur W. , Tseng Elaine E. , Baker Anthony J. , Saloner David , Einstein Daniel R. , Ratcliffe Mark B. , Guccione Julius M.
Published: March 2010

A noninvasive method for estimating regional myocardial contractility in vivo would be of great value in the design and evaluation of new surgical and medical strategies to treat and/or prevent infarction-induced heart failure. As a first step toward developing such a method, an explicit finite element (FE) model-based formal optimization of regional myocardial contractility in a sheep with left ventricular (LV) aneurysm was performed using tagged magnetic resonance (MR) images and cardiac catheterization pressures. From the tagged MR images, three-dimensional (3D) myocardial strains, LV volumes, and geometry for the animal-specific 3D FE model of the LV were calculated, while the LV pressures provided physiological loading conditions. Active material parameters (Tmax_B and Tmax_R) in the noninfarcted myocardium adjacent to the aneurysm (borderzone) and in the myocardium remote from the aneurysm were estimated by minimizing the errors between FE model-predicted and measured systolic strains and LV volumes using the successive response surface method for optimization. The significant depression in optimized Tmax_B relative to Tmax_R was confirmed by direct ex vivo force measurements from skinned fiber preparations. The optimized values of Tmax_B and Tmax_R were not overly sensitive to the passive material parameters specified. The computation time of less than 5 h associated with our proposed method for estimating regional myocardial contractility in vivo makes it a potentially very useful clinical tool.
Ultrafast Laser Micromachining of Latex for Balloon Angioplasty
Authors: Ramanathan Diwakar , Molian Pal
Published: March 2010

Latex balloons used in percutaneous transluminal coronary angioplasty are micromachined by mechanical, electrical, and optical methods. However, the cleanliness, straightness, and thermal damage obtained in these methods must be improved in order to minimize the adhesion of a balloon on the catheter tube. In this work, a femtosecond pulsed laser was used to micromachine 1.5 mm diameter latex tubes. The focused beam coupled with argon shield gas substantially improved the quality of cuts and holes acceptable by the Food and Drug Administration. Ultrafast laser by virtue of nonthermal ablation enabled the best quality in machined profiles.
An Active Foot-Ankle Prosthesis With Biomechanical Energy Regeneration
Authors: Hitt Joseph K. , Sugar Thomas G. , Holgate Matthew , Bellman Ryan
Published: March 2010

A unique, robust, robotic transtibial prosthesis with regenerative kinetics was successfully built and a 6-month human subject trial was conducted on one male below-the-knee amputee under linear walking conditions. This paper presents the quasistatic system modeling, DC motor and transmission modeling and analyses, design methodology, and model verification. It also outlines an approach to the design and development of a robotic transtibial prosthesis. The test data will show that the true power and energy requirement predicted in the modeling and analyses is in good agreement with the measured data, verifying that the approach satisfactorily captures the physical system. The modeling and analyses in this paper describes a process to determine an optimal combination of motors, springs, gearboxes, and rotary to linear transmissions to significantly minimize the power and energy consumption. This kinetic minimization allows the downsizing of the actuation system and the battery required for daily use to a self-portable level.
Creation of a mixed poly(ethylene glycol) tethered-chain surface for preventing the nonspecific adsorption of proteins and peptides
Authors: Uchida Katsumi , Hoshino Yuki , Tamura Atsushi , Yoshimoto Keitaro , Kojima Shuji , Yamashita Keichiro , Yamanaka Ichiro , Otsuka Hidenori , Kataoka Kazunori , Nagasaki Yukio
Published: March 2010

Using a heterotelechelic poly(ethylene glycol) (PEG) possessing a mercapto group at one end and an acetal group at the other end (acetal-PEG-SH), the authors constructed a reactive PEG tethered-chain surface on a surface plasmon sensor (SPR) gold chip for biosensing with high sensitivity. Nonspecific bovine serum albumin adsorption on the PEG tethered-chain surface was significantly influenced by the density of the PEG chain, and was almost completely suppressed by increasing the PEG density through the repetitive treatment of the chip surface with acetal-PEG-SH. The PEG density was increased even more by adding an underbrushed layer made of shorter-PEG-SH-chain molecules (2 kDa, hereafter 2k) to the surface made of longer-PEG-SH-chain molecules (5 kDa, hereafter 5k). SPR measurement then gave an estimate of the adsorption of a series of proteins with varying sizes and isoelectric points on the PEG chain surface having an underbrushed layer (PEG5k/2k surface). As compared to other SPR surfaces, viz., a commercial carboxymethyl dextran and conventional PEG5k tethered-chain surface without an underbrushed layer, the mixed PEG5k/2k surface showed almost complete inhibition of the nonspecific adsorption not only of high-molecular-weight proteins but also of low-molecular-weight peptides.
Selective immobilization of biomolecules onto an activated polymeric adlayer
Authors: Lee Bong Soo , Park Sangjin , Lee Kyung-Bok , Jon Sangyong , Choi Insung S.
Published: March 2010

The authors report a facile method for the selective immobilization of biomolecules onto a gold surface that was preactivated by a polymeric adlayer. The polymeric adlayer was designed to perform triple functions: high resistance to nonspecific protein adsorption, efficient surface anchoring, and subsequent covalent attachment of biomolecules. For this purpose, a random copolymer, poly(PEGMA-r-NAS), was synthesized by radical polymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMA) and N-acryloxysuccinimide (NAS). In the first step, the polymeric adlayer was formed onto amine-terminated self-assembled monolayers (SAMs) on gold through covalent bond formation between reactive N-hydroxysuccinimide (NHS) ester of the copolymer and the amine of the SAMs. In the second step, amine-bearing biotin as a model biomolecule was covalently attached onto the polymeric adlayer that still contained unreacted NHS esters. The degrees of the binding sensitivity for a target protein and the nonspecific binding for four model proteins on the biotinylated polymeric adlayer were examined by surface plasmon resonance spectroscopy. Finally, the specific immobilization of rhodamin (TRITC)-conjugated streptavidin on the biotinylated polymeric adlayer was achieved by a simple microcontact printing technique, resulting in well-defined patterns of the protein.
Short wavelength band edge thermometry during molecular beam epitaxial growth of GaN on SiC substrates and detected adatom self-heating effects
Authors: Hoke W. E. , Barlett D. , Kennedy T. D. , Wissman B. , Mosca J. J.
Published: March 2010

Band edge thermometry was used to measure the temperature of 4H SiC substrates, band gap of 3.25 eV, during heat-up followed by molecular beam epitaxial growth of GaN structures. The surface of the rotating wafer was illuminated with a white light source which provided sufficient scattered signal for SiC substrate temperature measurements of single side polished substrates and unmetallized double side polished substrates. Substrate temperatures above 400 °C could be measured with good signal-to-noise ratio. At 750 °C the precision was ±1 °C despite the small temperature dependence of the SiC band gap. A complete spectral interference oscillation was observed for a layer thickness of 800 Å. The scattered intensity was found to be dependent on whether gallium- or nitrogen-rich growth conditions were used. During conventional gallium-rich GaN growth on unmetallized, double sided polished substrates, the thermometer detected an increase in wafer temperature due to the presence of surface gallium. A similar adatom self-heating effect was observed with indium.
Angular distribution of atoms emitted from a SrZrO3 target by laser ablation under different laser fluences and oxygen pressures
Authors: Konomi I. , Motohiro T. , Azuma H. , Asaoka T. , Nakazato T. , Sato E. , Shimizu T. , Fujioka S. , Sarukura N. , Nishimura H.
Published: March 2010

Angular distributions of atoms emitted by laser ablation of perovskite-type oxide SrZrO3 have been investigated using electron probe microanalysis with wavelength-dispersive spectroscopy and charge-coupled device photography with an interference filter. Each constituent element has been analyzed as a two-modal distribution composed of a broad cosm θ distribution and a narrow cosn θ distribution. The exponent n characterizes the component of laser ablation while the exponent m characterizes that of thermal evaporation, where a larger n or m means a narrower angular distribution. In vacuum, O (n=6) showed a broader distribution than those of Sr (n=16) and Zr (n=17), and Sr+ exhibited a spatial distribution similar to that of Sr. As the laser fluence was increased from 1.1 to 4.4 J/cm2, the angular distribution of Sr became narrower. In the laser fluence range of 1.1–4.4 J/cm2, broadening of the angular distribution of Sr was observed only at the fluence of 1.1 J/cm2 under the oxygen pressure of 10 Pa. Monte Carlo simulations were performed to estimate approximately the energy of emitted atoms, focusing on the broadening of the angular distribution under the oxygen pressure of 10 Pa. The energies of emitted atoms were estimated to be 1–20 eV for the laser fluence of 1.1 J/cm2, and more than 100 eV for 2.2 and 4.4 J/cm2.
Fabrication and electron field-emission properties of titanium oxide nanowire on glass substrate
Authors: Wakaya F. , Miki M. , Fukuyama C. , Murakami K. , Abo S. , Takai M.
Published: March 2010

Titanium-oxide nanowires, whose diameter and length were in the order of 10 nm and 1 μm, respectively, were successfully fabricated directly on a glass substrate. The fabrication process adopted is very simple, in which the sputter-coated titanium film was immersed into NaOH solution at 80 °C and annealed at 500 °C in vacuum. Field-emission current from the titanium-oxide nanowires synthesized on a glass substrate was first observed, whose turn-on field was approximately 4 V/μm.
Enhanced retained dose uniformity in NiTi spinal correction rod treated by three-dimensional mesh-assisted nitrogen plasma immersion ion implantation
Authors: Lu Q. Y. , Hu T. , Kwok Dixon T. K. , Chu Paul K.
Published: March 2010

Owing to the nonconformal plasma sheath in plasma immersion ion implantation of a rod sample, the retained dose can vary significantly. The authors propose to improve the implant uniformity by introducing a metal mesh. The depth profiles obtained with and without the mesh are compared and the implantation temperature at various locations is evaluated indirectly by differential scanning calorimeter. Our results reveal that by using the metal mesh, the retained dose uniformity along the length is greatly improved and the effects of the implantation temperature on the localized mechanical properties of the implanted NiTi shape memory alloy rod are nearly negligible.
Estimating detection probabilities of tagged fish migrating past fixed receiver stations using only local information
Authors: Melnychuk Michael C. , Walters Carl J.
Published: March 2010

We developed a method to predict the probability of detecting acoustic tags crossing a receiver station using only detection information at that station. This method is suitable for acoustic or radio telemetry studies in which individually tagged animals migrate past fixed stations (where a station may consist of one or more receivers). It is based on fitting attenuation models to sequences of detections and missed transmissions of individually coded tags in fish migrating past stations of the Pacific Ocean Shelf Tracking Project (POST). We used estimated attenuation model parameters from detected fish at each station to predict the number of fish that crossed the station undetected, which in turn was used to calculate the local detection probability. This estimator was correlated (r = 0.54–0.81 in river and coastal habitats) with mark–recapture estimates of detection probability (pmr) that use nonlocal detection information at stations further along migration routes. This local detection probability estimate can be used as a covariate of pmr in mark–recapture models and can predict approximate values of pmr at final detection stations where pmr is not estimable because of the lack of recaptures further along migration routes.
Thermal dynamics of ovarian maturation in Atlantic cod (Gadus morhua)
Authors: Kjesbu Olav Sigurd , Righton David , Krüger-Johnsen Maria , Thorsen Anders , Michalsen Kathrine , Fonn Merete , Witthames Peter R.
Published: March 2010

The timing and success of spawning in marine fish are of fundamental importance to population persistence and distribution and, for commercial species, sustainability. Their physiological processes of reproduction are regulated, in part, by water temperature, and therefore changes in marine climate may have dramatic effects on spawning performance. Using adult Atlantic cod ( Gadus morhua ) as a case study, we examined the links between water temperature, body size, vitellogenesis, and spawning time by conducting extensive laboratory and field studies. Our experiments documented that vitellogenesis generally starts at autumnal equinox and that oocyte growth and investment are greater in cod held at warmer temperatures. Furthermore, spawning occurred earlier when oocyte growth was more rapid. Large females spawned earlier than smaller females at warmer temperatures, but this effect vanished at colder temperatures. The experimental results were confirmed by measurements of oocyte growth collected from wild-caught cod in northern (Barents Sea) and southern (Irish Sea and North Sea) populations. The established, general model of oocyte maturation was consistent with published egg production curves of cod from these waters, considering relevant in situ temperatures recorded by individual data-storage tags on cod. These findings have considerable relevance for future studies of fish recruitment in relation to climate change.
A comparison of pre-industrial and present-day changes in Bosmina and Daphnia size structure from soft-water Ontario lakes
Authors: Korosi Jennifer B. , Paterson Andrew M. , DeSellas Anna M. , Smol John P.
Published: March 2010

Understanding the long-term controls on cladoceran size structure has important implications for aquatic ecosystems. Although there has been considerable interest in zooplankton size trends for Canadian Shield lakes, data are not available for zooplankton size structure prior to the period of anthropogenic disturbances. Here, we present pre- and post-impact size data for the common pelagic cladocerans Bosmina and Daphnia for 44 well-studied Shield lakes in south-central Ontario (Canada). We show that Daphnia were larger and that the length of Bosmina body appendages (mucrones and antennules) was longer in pre-industrial times than they are today. The reduction in Bosmina appendage length we observed may suggest a reduction in copepod predation pressure since pre-industrial times. Reduced maximum body size in Daphnia is a predicted response to a warming climate in north temperate lakes; however, we suggest that alternate explanations, specifically acidification and subsequent recovery following emission reductions, should also be explored as the primary drivers of Daphnia size changes in this lake set. Overall, our results highlight the importance of pre-impact data for understanding the long-term controls on cladoceran body size from pre-1850 to present.
Cold-season nitrous oxide dynamics in a drained boreal peatland differ depending on land-use practice
Authors: Maljanen Marja , Hytönen Jyrki , Martikainen Pertti J.
Published: March 2010

Drained peat soils are important sources of greenhouse gases such as nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2). These gases are produced in soil and they can be emitted year-round. We measured N2O and CH4 flux rates and total respiration (RTOT) over a year from a drained peatland with one subsite as a grass field and another forested. The field acted annually as a small source (0.36 ± 0.73 kg C·ha–1) and the forest as a sink (–1.93 ± 0.50 kg C·ha–1) for CH4. Mean annual RTOT rates were 660 and 297 mg·m–2·h–1 in the field and in the forest, respectively. Annual N2O emission rates were 34.8 ± 2.4 kg N·ha–1 from the field and 25.5 ± 5.5 kg N·ha–1 from the forest. More than 80% of the annual N2O emissions took place during winter. In the field, high emissions were detected during thawing in April when N2O accumulated in soil during the winter was released. In the forest, N2O emissions peaked when the top soil was freezing in January and accumulation of N2O in soil was less than in the field. The timing of the episodic high N2O emissions thus differed depending on the land use.
Early vegetation control for the regeneration of a single-cohort, intimate mixture of white spruce and trembling aspen on upland boreal sites
Authors: Pitt Douglas G. , Comeau Philip G. , Parker William C. , MacIsaac Daniel , McPherson Scott , Hoepting Michael K. , Stinson Al , Mihajlovich Milo
Published: March 2010

In Canada’s boreal forest region, there is increasing demand for practical regeneration strategies that will recreate mixed stands of white spruce ( Picea glauca (Moench) Voss) and trembling aspen ( Populus tremuloides Michx.). In 2002, we implemented an experiment in both west-central Alberta and northeastern Ontario to better understand the effects of herbaceous and woody vegetation control on crop tree survival and growth, within the context of prescription development for the regeneration of a single-cohort, intimate mixture of spruce and aspen. After five growing seasons, good spruce growth, health, and survival were observed with 2 m radial treatments consisting of herbaceous and woody (i.e., complete) vegetation control centred on trees planted at 5 m spacing. These spruce were 4%–64% taller and 68%–178% larger in stem diameter than untended trees, leading to 167%–1166% gains in stem volume, and were at least equivalent to the same stock grown at 2.5 m spacing and provided with complete, continuous relief from competition. Removing only the woody vegetation within treated radii stimulated herbaceous competition, resulting in reduced survival and growth of spruce and reduced height of surrounding aspen. Early results suggest that spot treatments that provide 2–4 years of relief from herbaceous and woody competition may offer a practical strategy for growing spruce with aspen.
COMPLETE VECTOR FIELDS ON ℂ2 WHOSE UNDERLYING FOLIATION IS POLYNOMIAL
Authors: BUSTINDUY ALVARO
Published: March 2010

We extend the classification of complete polynomial vector fields in two complex variables given by Brunella to cover the case of holomorphic (non-polynomial) vector fields whose underlying foliation is still polynomial.
CALCULATION OF THE RAMAN FREQUENCIES AS A FUNCTION OF TEMPERATURE IN PHASE III OF NH4I
Authors: KAVRUK D. , YURTSEVEN H.
Published: March 2010

We study here the temperature dependence of the Raman frequencies for the overtone 2ν6 of the librational mode ν6 in phase III of NH 4 I . By using the experimental infrared frequencies of the 2ν6 mode, we predict the Raman frequencies of this overtone 2ν6 mode as a function of temperature at atmospheric pressure in phase III of NH 4 I . Our calculations indicate that the Raman frequencies of 2ν6 exhibit anomalous behavior at around 110 K (P = 0) in phase III of NH 4 I , as observed experimentally.
ON THE NUMBER OF IRREDUCIBLE COMPONENTS OF THE REPRESENTATION VARIETY OF A FAMILY OF ONE-RELATOR GROUPS
Authors: MARTÍN-MORALES JORGE , OLLER-MARCÉN ANTONIO M.
Published: March 2010

Let us consider the group G = 〈x, y | xm = yn〉 with m and n nonzero integers. The set R(G) of representations of G over SL(2, ℂ) is a four-dimensional algebraic variety which is an invariant of G. In this paper the number of irreducible components of R(G) together with their dimensions are computed. We also study the set of metabelian representations of this family of groups. Finally, the behavior of the projection t : R(G) → X(G), where X(G) is the character variety of the group, and some combinatorial aspects of R(G) are investigated.
MAXIMAL SUBGROUPS OF A SYLOW p-SUBGROUP AND p-NILPOTENCY OF FINITE GROUPS
Authors: XU YONG , LI XIANHUA
Published: March 2010

In this paper, we prove the p-nilpotency of a finite group G with the assumption that some subgroups of a Sylow subgroup are semi CAP-or c-supplemented subgroups. We get some interesting new results.
SOME FIELD THEORETIC PROPERTIES AND AN APPLICATION CONCERNING TRANSCENDENTAL NUMBERS
Authors: JENSEN CHRISTIAN U. , MARQUES DIEGO
Published: March 2010

For a proper subfield K of [Formula: see text] we show the existence of an algebraic number α such that no power αn, n ≥ 1, lies in K. As an application it is shown that these numbers, multiplied by convenient Gaussian numbers, can be written in the form P(T)Q(T) for some transcendental numbers T where P and Q are arbitrarily prescribed nonconstant rational functions over [Formula: see text].
PARTIAL ACTIONS OF ORDERED GROUPOIDS ON RINGS
Authors: BAGIO DIRCEU , FLORES DAIANA , PAQUES ANTONIO
Published: March 2010

In this paper, we introduce the notion of a partial action of an ordered groupoid on a ring and we construct the corresponding partial skew groupoid ring. We present sufficient conditions under which the partial skew groupoid ring is either associative or unital. Also, we show that there is a one-to-one correspondence between partial actions of an ordered groupoid G on a ring R, in which the domain of each partial bijection is an ideal, and meet-preserving global actions of the Birget–Rhodes expansion G BR of G on R. Using this correspondence, we prove that the partial skew groupoid ring is a homomorphic image of the skew groupoid ring constructed through the Birget–Rhodes expansion.
HOW TO SHARPEN A TRIDIAGONAL PAIR
Authors: ITO TATSURO , TERWILLIGER PAUL
Published: March 2010

Let 𝔽 denote a field and let V denote a vector space over 𝔽 with finite positive dimension. We consider a pair of linear transformations A : V → V and A* : V → V that satisfy the following conditions: (i) each of A, A* is diagonalizable; (ii) there exists an ordering [Formula: see text] of the eigenspaces of A such that A* Vi ⊆ Vi-1 + Vi + Vi+1 for 0 ≤ i ≤ d, where V-1 = 0 and Vd+1 = 0; (iii) there exists an ordering [Formula: see text] of the eigenspaces of A* such that [Formula: see text] for 0 ≤ i ≤ δ, where [Formula: see text] and [Formula: see text]; (iv) there is no subspace W of V such that AW ⊆ W, A* W ⊆ W, W ≠ 0, W ≠ V. We call such a pair a tridiagonal pair on V. It is known that d = δ, and for 0 ≤ i ≤ d the dimensions of Vi, [Formula: see text], Vd-i, [Formula: see text] coincide. Denote this common dimension by ρi and call A, A*sharp whenever ρ0 = 1. Let T denote the 𝔽-subalgebra of End 𝔽(V) generated by A, A*. We show: (i) the center Z(T) is a field whose dimension over 𝔽 is ρ0; (ii) the field Z(T) is isomorphic to each of E0TE0, EdTEd, [Formula: see text], [Formula: see text], where Ei (resp. [Formula: see text]) is the primitive idempotent of A (resp. A*) associated with Vi (resp. [Formula: see text]); (iii) with respect to the Z(T)-vector space V the pair A, A* is a sharp tridiagonal pair.
A NEW MODULARITY FOR DETECTING ONE-TO-MANY CORRESPONDENCE OF COMMUNITIES IN BIPARTITE NETWORKS
Authors: MURATA TSUYOSHI , IKEYA TOMOYUKI
Published: March 2010

Real-world relations are often represented as bipartite networks, such as paper-author networks and event-attendee networks. Extracting dense subnetworks (communities) from bipartite networks and evaluating their qualities are practically important research topics. As the attempts for evaluating divisions of bipartite networks, Guimera and Barber propose bipartite modularities. This paper discusses the properties of these bipartite modularities and proposes another bipartite modularity that allows one-to-many correspondence of communities of different vertex types.
HIRZEBRUCH CLASSES AND MOTIVIC CHERN CLASSES FOR SINGULAR SPACES
Authors: BRASSELET JEAN-PAUL , SCHÜRMANN JÖRG , YOKURA SHOJI
Published: March 2010

In this paper we study some new theories of characteristic homology classes of singular complex algebraic (or compactifiable analytic) spaces.

We introduce a motivic Chern class transformationmCy: K0( var /X) → G0(X) ⊗ ℤ[y], which generalizes the total λ-class λy(T*X) of the cotangent bundle to singular spaces. Here K0( var /X) is the relative Grothendieck group of complex algebraic varieties over X as introduced and studied by Looijenga and Bittner in relation to motivic integration, and G0(X) is the Grothendieck group of coherent sheaves of [Formula: see text]-modules. A first construction of mCyis based on resolution of singularities and a suitable "blow-up" relation, following the work of Du Bois, Guillén, Navarro Aznar, Looijenga and Bittner. A second more functorial construction of mCyis based on some results from the theory of algebraic mixed Hodge modules due to M. Saito.

We define a natural transformation Ty*: K0( var /X) → H*(X) ⊗ ℚ[y] commuting with proper pushdown, which generalizes the corresponding Hirzebruch characteristic. Ty*is a homology class version of the motivic measure corresponding to a suitable specialization of the well-known Hodge polynomial. This transformation unifies the Chern class transformation of MacPherson and Schwartz (for y = -1), the Todd class transformation in the singular Riemann-Roch theorem of Baum–Fulton–MacPherson (for y = 0) and the L-class transformation of Cappell-Shaneson (for y = 1).

We also explain the relation among the "stringy version" of our characteristic classes, the elliptic class of Borisov–Libgober and the stringy Chern classes of Aluffi and De Fernex–Lupercio–Nevins–Uribe.

All our results can be extended to varieties over a base field k of characteristic 0.
ON CLOSED SETS IN HILBERT SPACE WITH CONVEX PROJECTIONS UNDER SOMEWHERE DENSE SETS OF DIRECTIONS
Authors: BAROV STOYU , DIJKSTRA JAN J.
Published: March 2010

Let k be a fixed natural number. In an earlier paper the authors show that if C is a closed and nonconvex set in the Hilbert space ℓ2 such that the closures of the projections onto allk-hyperplanes (planes with codimension k) are convex and proper, then C must contain a closed copy of ℓ2. Here this theorem is strengthened significantly by making the much weaker assumption that the set of projection directions is somewhere dense. To show the sharpness of the main theorem we construct "minimal imitations" of closed convex sets in ℓ2. In addition, we show that closed convex sets with an empty geometric interior cannot be imitated by other closed sets.
A LOCAL OPTIMAL DIASTOLIC INEQUALITY ON THE TWO-SPHERE
Authors: BALACHEFF FLORENT
Published: March 2010

We prove a local optimal inequality on the two-sphere between the area and the diastole — defined by a minimax process on the one-cycle space — in a neighborhood of the singular metric made of two equilateral triangles glued along their boundaries.
Physical changes of porous Hungarian limestones related to silicic acid ester consolidant treatments
Authors: Pápay Z. , Török Á.
Published: March 2010

Porous limestones are widely used in the monuments of Hungary, and are often treated using stone consolidants on site during restoration works. Two types of porous Miocene limestones from Sóskút were treated with dilute and concentrated silicic acid ester under laboratory conditions. The aim of the experiments was to assess the performance of the consolidants of different concentrations on fine- and medium-grained limestones, and to detect physical changes caused by consolidation. The pore-size distribution and fabric of the limestones were also different with initial porosities of 37 and 23%, respectively. In the open pores only a few per cent (3.2–5.2%) of silica gel was precipitated even under vacuum saturation. The loss of porosity was higher when concentrated consolidant was used. The decrease in porosity was found not to be proportional to the changes in strength. Indeed, the dilute consolidant caused a greater increase in strength than the concentrated one. The increase of tensile strength was higher for the less porous medium-grained limestone than for the fine-grained one. The differences in strength between non-consolidated and treated specimens were also detectable using ultrasonic pulse velocities. The tests have shown that the efficacy of silica acid ester treatments in terms of strength is less influenced by the concentration of the consolidant, but rather its ability to reach the micropores of porous limestones.
Limestone on the ‘Don Pedro I’ facade in the Real Alcázar compound, Seville, Spain
Authors: Vazquez-Calvo C. , Varas M. J. , De Buergo M. Alvarez , Fort R.
Published: March 2010

This paper discusses the research conducted prior to restoring the ‘Don Pedro I’ facade on the Real Alcázar or royal palace at Seville, Spain. The different types of stone on the facade were located and characterized, and their state of decay mapped. Although other materials (brick, rendering, ceramics, marble) are present on the facade, its main elements are made from two types of limestone:palomeraandtosca, each in a different state of conservation and exhibiting distinct behaviour. Colour parameters, real and bulk densities, compactness, open porosity, water saturation coefficient and total porosity were determined to characterize the two varieties. In addition, ultrasonic techniques were used to map the various levels of decay on the facade, stone by stone, for future interventions. The findings show that owing to its petrographical and petrophysical properties,palomerastone is of a lower quality thantoscastone, and has undergone more intense deterioration.
The church of Santa Engrácia (the National Pantheon, Lisbon, Portugal): building campaigns, conservation works, stones and pathologies
Authors: Figueiredo C. , Aires-Barros L. , Neto M. J.
Published: March 2010

A study of the different building campaigns, restoration works, pathologies and stones used through time in the Church of Santa Engrácia (Portuguese National Pantheon) is presented. The changing fortunes of the monument make it a useful case study in terms of building stone use and decay. This bold baroque project, begun in the seventeenth century, remained without a roof until the 1960s. At that time the leader of the conservative regime of Estado Novo (‘New State’), António de Oliveira Salazar, decided to complete the building as a national pantheon to provide a memorial to some of the personalities of Portuguese history. A complementary approach between the geosciences and history of art identified the ancient and more recent quarries, and the main stone types, used during its different building campaigns and restoration/conservation works. The local stone variety ‘lioz’, extracted in the area around Lisbon, was the main type used. An overview of the current knowledge of the chemical, physical and mechanical characteristics of these stones is now available. Besides new data on the typology, causes and processes of the major weathering forms observed inside and outside the building, the building campaigns and restoration works are also presented.