bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanics of Pipes Conveying Fluids—Part II: Applications and Fluidelastic Problems
Authors: Ibrahim R. A.
Published: March 2011

This paper is the second part of the two-part review article presenting an overview of mechanics of pipes conveying fluid and related problems such as the fluid-elastic instability under conditions of turbulence in nuclear power plants. In the first part, different types of modeling, dynamic analysis and stability regimes of pipes conveying fluid restrained by elastic or inelastic barriers were described. The dynamic and stability behaviors of pinned-pinned, clamped-clamped, and cantilevered pipes conveying fluid together with curved and articulated pipes were discussed. Other problems such as pipes made of viscoelastic materials and active control of severe pipe vibrations were considered. The first part was closed by conclusions highlighting resolved and nonresolved controversies reported in the literature. The second part will address the problem of fluidelastic instability in single- and two-phase flows and fretting wear in process equipment, such as heat exchangers and steam generators. Connors critical velocity will be discussed as a measure of initiating fluidelastic instability. Vibro-impact of heat exchanger tubes and the random excitation by the cross-flow can produce a progressive damage at the supports through fretting wear or fatigue. Antivibration bar supports used to limit pipe vibrations are described. An assessment of analytical, numerical, and experimental techniques of fretting-wear problem of pipes in heat exchangers will be given. Other topics related to this part include remote impact analysis and parameter identification, pipe damage-induced by pressure elastic waves, the dynamic response and stability of long pipes, marine risers together with pipes aspirating fluid, and carbon nanotubes conveying fluid.
Effects of Multiblocking and Axial Gap Distance on Performance of Partial Admission Turbines: A Numerical Analysis
Authors: Hushmandi Narmin Baagherzadeh , Fransson Torsten H.
Published: March 2011

In this paper, the effects of axial gap distance between the first stage stator and rotor blades and multiblocking on aerodynamics and performance of partial admission turbines are analyzed numerically. The selected test case is a two stage axial steam turbine with low reaction blades operating with compressed air. The multiblocking effect is studied by blocking the inlet annulus of the turbine in a single arc and in two opposing blocked arcs, each having the same admission degree. The effect of axial gap distance between the first stage stator and rotor blades is studied while varying the axial gap by 20% compared with the design gap distance. Finally, full admission turbine is modeled numerically for comparison. Performance of various computational cases showed that the first stage efficiency of the two stage partial admission turbine with double blockage was better than that of the single blockage turbine; however, the extra mixing losses of the double blockage turbine caused the efficiency to deteriorate in the downstream stage. It was shown that the two stage partial admission turbine with smaller axial gap than the design value had better efficiency of the first stage due to lower main flow and leakage flow interactions; however, the efficiency at the second stage decreased faster compared with the other cases. Numerical computations showed that the parameters, which increased the axial force of the first stage rotor wheel for the partial admission turbine, were longer blocked arc, single blocked arc, and reduced axial gap distance between the first stage stator and rotor blades.
Understanding Effects of Wet Compression on Separated Flow Behavior in an Axial Compressor Stage Using CFD Analysis
Authors: Sun Lanxin , Zheng Qun , Li Yijin , Bhargava Rakesh
Published: March 2011

The effects of wet compression on the flow field within a compressor stage, particularly in the presence of the separated flow region, are not fully understood. Numerical simulations of 3D compressible separated flows within a wet compression compressor stage are carried out using a computational fluid dynamics (CFD) program. Numerical computations of flow fields in a compressor cascade with wet compression assume that a separated region exist in the corner of the rotor blade suction surface and hub surface in the case of dry compression. Under different operating conditions and with wet compression, this study presents the changes in the extent of separated region on the flow channel surfaces, compression efficiency, pressure ratio and specific compression work, etc. Also, effects of factors such as droplet size, droplet temperature, and injected water flow rate on the compressor stage performance and flow field within compressor stage passage have been investigated. The results show that wet compression could weaken and eliminate the flow separation and then the efficiency and pressure ratio maintain a high level.
Aerodynamic and
Endwall Film-Cooling Investigations of a Gas Turbine Nozzle Guide Vane Applying
Temperature-Sensitive Paint
Authors: Kunze Martin , Vogeler Konrad , Brown Glenn , Prakash Chander , Landis Kenneth
Published: March 2011

Endwall film-cooling investigations are conducted with a single row of fan-shaped holes in a low-speed, six-bladed linear cascade. The incidence of the inlet flow was changed between −5 deg and 40 deg to achieve higher loading conditions, which results in an intensification of the secondary flow and enhanced interaction with the injected coolant. The investigated profile is based on a near-hub section of the nozzle guide vane of a highly loaded gas turbine. The aerodynamic performance was investigated using pneumatic probes. The film-cooling effectiveness distribution is determined using the temperature-sensitive paint technique. Carbon dioxide was used as coolant to provide elevated density ratios of about 1.4. Although low thermal conductivity material is used for the endwall test plate, the measured temperature fields show influences of 3D-heat conduction inside the test plate. To measure film effectiveness and the heat transfer separately, an adiabatic test surface is needed. Therefore, the effects of heat conduction are modeled using the finite-element-method. With the resulting convective heat flux pattern derived from the computations, the endwall film-cooling measurements are corrected. Furthermore, this approach is applied to evaluate the heat loss inside the holes and the film discharge temperature at the hole exit.
Formation of 10-μm-level patterned organic thin film using microthermal evaporation
Authors: Choi Jun Hee , Zoulkarneev Andrei , Noh Tae Yong , Lee Young Gu , Kim Sun Il , Park Sung Soo , Baik Chan Wook , Choi Byoung Lyong , Kim Miyoung , Yi Gyu-Chul , Kim Jong Min
Published: March 2011

This article reports the fabrication of 10-μm-level stripe patterns on an organic layer using microthermal evaporation. During this process, an organic layer is coated on a glass substrate with a bridge-type microheater array, and then selectively evaporated and deposited to form a fine pattern onto another glass substrate, separated by a micron-scale gap from the microheater array. Using a unique numerical model for microthermal evaporation, thickness profiles of the pattern were calculated and matched to experimental data. Furthermore, high optical qualities of the transferred luminescent pattern layer were confirmed using microphotoluminescence spectroscopy. This microthermal evaporation method confirms the feasibility of fabricating fine organic patterns with scalability to larger sizes.
Formation of silicon nanocrystals embedded in high-κ dielectric HfO2 and their application for charge storage
Authors: Li Weilong , Jia Rui , Chen Chen , Li Haofeng , Liu Xinyu , Yue Huihui , Ding Wuchang , Ye Tianchun , Kasai Seiya , Hashizume Tamotsu , Wu Nanjian , Xu Bingshe
Published: March 2011

Annealing thin films of silicon containing HfO2 films deposited by an electron-beam coevaporation produces silicon nanocrystals embedded in high-κ dielectric HfO2. Such films can be used to fabricate nonvolatile memory devices. By changing the Si content in the precursor HfSixO2 (x=1, 2, 3, or 4) film, the size and density of silicon nanocrystal could be controlled and high-density of silicon nanocrystals could be obtained. Transmission electron microscopy observations showed that the maximum density of silicon nanocrystals was as high as 1.3×1013 cm−2 for HfSi4O2 and the average nanocrystal diameter was 4.3 nm. The metal-oxide semiconductor capacitor memory structure with embedded silicon nanocrystals in HfSi4O2 exhibited the largest memory window, 3.94 V under ±5 V sweep voltage.
Study of molecular beam epitaxially grown InGaAsSbN/GaSb single quantum wells
Authors: Bharatan Sudhakar , Iyer Shanthi , Li Jia , Rawdanowicz Thomas A. , Reynolds Lewis
Published: March 2011

InGaAsSbN quantum wells (QWs) have been investigated for potential light-emitting devices in the midinfrared region. This paper presents the growth and properties of molecular beam epitaxially grown InGaAsSbN single QWs using a variety of characterization techniques. A 10 K photoluminescence emission at 2.27 μm, with a lowest full width at half maxima of 5 meV which shifted to 2.30 μm on in situ annealing, has been observed. The presence of well resolved Pendellosung fringes in high resolution x-ray diffraction and sharp abrupt interfaces in the corresponding transmission electron microscope (TEM) images are indications of the high quality of these QWs. Raman spectroscopy studies reveal the presence of well resolved Raman peaks with higher intensity, along with the presence of sharp second order modes of GaSb, further attesting to the high quality of the QW structures grown. Investigation of the annealed samples using Z-contrast scanning TEM images reveals atomic interdiffusion between the QW and surrounding GaSb layers, increasing the effective thickness of the QW, which explains the redshift upon annealing.
High power 1.25 μm InAs quantum dot vertical external-cavity surface-emitting laser
Authors: Albrecht Alexander R. , Hains Christopher P. , Rotter Thomas J. , Stintz Andreas , Malloy Kevin J. , Balakrishnan Ganesh , Moloney Jerome V.
Published: March 2011

The authors demonstrate InAs quantum dot (QD)-based optically pumped vertical external-cavity surface-emitting lasers grown by molecular beam epitaxy. Active region designs utilizing two different resonant periodic gain (RPG) structures are compared. The first RPG structure is a more traditional design consisting of three QD layers per antinode of the E-field standing wave, repeated four times, for a total of 12 QD layers. The second RPG has a single-QD layer per antinode, repeated 12 times. The single-QD layer per antinode structure allows for both superior strain relief as well as more complete pump absorption and thus results in significantly improved device performance over the traditional multi-QD layer per antinode design. The authors were able to demonstrate over 3 W of output power at room temperature using a thermal grade polycrystalline chemical-vapor deposition diamond heat spreader mounted on the backside of a sample thinned by mechanical polishing.
Electrical and structural properties of ultrathin SiON films on Si prepared by plasma nitridation
Authors: Hourdakis E. , Nassiopoulou A. G. , Parisini A. , Reading M. A. , van den Berg J. A. , Sygellou L. , Ladas S. , Petrik P. , Nutsch A. , Wolf M. , Roeder G.
Published: March 2011

The authors combined electrical and structural characterizations with analytical and spectroscopic measurements in order to fully analyze oxynitride nanofilms on Si that were produced in a minibatch type plasma nitridation reactor. The authors demonstrate that for the investigated samples the result of nitridation is different in the 2-nm-thick SiO2 films compared to the 5-nm-thick films. In the first case, nitridation results in an increase of the oxide film thickness compared to the non-nitrided film, with a consequent decrease in leakage current and an increase in the electrically measured equivalent oxide thickness (EOT). In contrast, nitridation of the 5-nm-thick SiO2 films leads to a reduction of both the leakage current and EOT. Finally, the authors demonstrate that the applied nitridation process results in the desired nitrogen profile with high nitrogen concentration near the top surface or the middle of the SiON film and low nitrogen concentration near the SiON/Si interface, which leads to a relatively low density of interface states at the SiON/Si interface (∼1011 states/cm2) for nonannealed films.
Low-misfit epilayer analyses using in situ wafer curvature measurements
Authors: France Ryan , Ptak Aaron J.
Published: March 2011

Several benefits of in situ wafer curvature monitoring on simple structures with low misfit are discussed. The misfit of lattice-mismatched layers is measured during pseudomorphic growth, allowing for experiments that test relationships between misfit and growth conditions. As an example, Bi incorporation in GaAs is quantified by varying the substrate temperature throughout growth while using curvature measurements to continuously calculate the composition. Results agree well with x-ray diffraction measurements on individual GaAsBi samples, demonstrating the utility of this technique for the study of incorporation in mismatched systems. Once relaxation begins, the strain and dislocation energetics of low-misfit epilayers are determined from changes in wafer curvature. The authors perform several analyses on GaInAs epilayers with different misfits using an anisotropic thin film approximation. Substantial information on dislocation formation and motion is derived from the wafer curvature. Potential applications of this technique include the study of devices that utilize coherently strained layers and structures that intentionally use dislocations to relieve strain. Wafer curvature is a powerful method for comparing strain evolution in mismatched materials.
Astrocytes Shape Axonal Signaling
Authors: Debanne Dominique , Rama Sylvain
Published: March 2011

The action potential waveform can be altered by astrocyte-mediated activation of neuronal glutamate receptors.
Comparison of Polymyxin B, Tigecycline, Cefepime, and Meropenem MICs for KPC-Producing Klebsiella pneumoniae by Broth Microdilution, Vitek 2, and Etest
Authors: Lat Asma , Clock Sarah A. , Wu Fann , Whittier Susan , Della-Latta Phyllis , Fauntleroy Kathy , Jenkins Stephen G. , Saiman Lisa , Kubin Christine J.
Published: March 2011

We report MIC agreement and error rates between broth microdilution (BMD), Vitek 2, and Etest against 48 clinical KPC-producing
Klebsiella pneumoniae
isolates for polymyxin B, tigecycline, cefepime, and meropenem. Both commercial testing methods were useful for tigecycline testing; Etest provided a conservative estimate of polymyxin B susceptibility. We suggest that laboratories consider the supplemental use of reference BMD or Etest for cefepime and meropenem for susceptibility testing of KPC-producing
K. pneumoniae
, as Vitek 2 did not provide reliable results.
Emergency department injury surveillance and aetiological research: bridging the gap with the two-stage case–control study design
Authors: Hagel Brent E
Published: March 2011

Objective

To provide an overview of the two-stage case–control study design and its potential application to ED injury surveillance data and to apply this approach to published ED data on the relation between brain injury and bicycle helmet use.

Methods

Relevant background is presented on injury aetiology and case–control methodology with extension to the two-stage case–control design in the context of ED injury surveillance. The design is then applied to data from a published case–control study of the relation between brain injury and bicycle helmet use with motor vehicle involvement considered as a potential confounder. Taking into account the additional sampling at the second stage, the adjusted and corrected odds ratio and 95% confidence interval for the brain injury–helmet use relation is presented and compared with the estimate from the entire original dataset. Contexts where the two-stage case–control study design might be most appropriately applied to ED injury surveillance data are suggested.

Results

The adjusted odds ratio for the relation between brain injury and bicycle helmet use based on all data (n=2833) from the original study was 0.34 (95% CI 0.25 to 0.46) compared with an estimate from a two-stage case–control design of 0.35 (95% CI 0.25 to 0.48) using only a fraction of the original subjects (n=480).

Conclusion

Application of the two-stage case–control study design to ED injury surveillance data has the potential to dramatically reduce study time and resource costs with acceptable losses in statistical efficiency.
Mural destabilization after aneurysm treatment with a flow-diverting device: a report of two cases
Authors: Hampton Timothy , Walsh Donal , Tolias Christos , Fiorella David
Published: March 2011

Background

Flow-diverting stents have demonstrated great promise for the treatment of cerebral aneurysms; however, clinical experience with the devices remains very preliminary. We present two cases of spontaneous delayed complications—one fatal aneurysm rupture and one symptomatic increase in aneurysm volume—following the treatment of intradural aneurysms with the Pipeline Embolization Device (PED).

Presentation/intervention

Two patients with unruptured, intradural aneurysms of the carotid artery underwent uneventful treatment with the PED (eV3, Irvine, California, USA). One patient, with a giant aneurysm of the carotid terminus, experienced worsening headache 5 days after the procedure and ultimately collapsed and became unresponsive. CT of the head demonstrated acute subarachnoid and intraventricular hemorrhage. The patient died the following day. A second patient with a large left posterior communicating artery aneurysm presented with progressive memory loss 3 months after PED reconstruction of the carotid artery. Although serial CT angiograms showed progressive thrombosis of the aneurysm to near-complete occlusion, MR of the brain demonstrated marked interval growth of the collective aneurysm–intra-aneurysmal thrombus mass with extensive edema throughout the adjacent left temporal lobe.

Conclusions

Flow-diverting devices have demonstrated tremendous promise for the treatment of complex, unruptured cerebral aneurysms. However, experience with this novel approach to aneurysm treatment is preliminary and the consequences of its application within the cerebrovasculature remain incompletely defined. Mural destabilization resulting in delayed, spontaneous, aneurysm growth and/or rupture may occur in the days to weeks following the application of flow-diverting devices to treat previously unruptured intracranial aneurysms. A better understanding of the incidence and etiology of these complications is essential for this technology to be optimally applied.
Microsurgical and endovascular management of pericallosal aneurysms
Authors: Hui Ferdinand K , Schuette Albert J , Moskowitz Shaye I , Spiotta Alejandro M , Lieber Michael L , Rasmussen Peter A , Dion Jacques E , Barrow Daniel L , Cawley C Michael
Published: March 2011

Background

Pericallosal, or A2 bifurcation, aneurysms are an infrequently encountered cause of subarachnoid hemorrhage (SAH). While the International Subarachnoid Aneurysm Trial showed improved outcomes for patients with any ruptured anterior circulation aneurysm treated with embolization, there was also a higher recurrence rate for embolized aneurysms. Notably, there were relatively few pericallosal aneurysms.

Objective

Specific analysis of pericallosal aneurysms may help guide therapeutic decisions.

Methods

Retrospective analysis of patients who presented with proven saccular pericallosal aneurysms was performed at two institutions from 1999 to 2009. Patients were stratified according to presentation Hunt and Hess grades and modified Fisher scores, treatment modality and outcomes as well as development of vasospasm, hydrocephalus and required treatment.

Results

Eighty-eight patients with pericallosal aneurysms were identified. Sixty-two presented with SAH and 26 in elective fashion, 2 of whom had a prior history of SAH. Fifty-four patients underwent microsurgical repair and 32 endovascular repair. Patients presenting with SAH due to pericallosal aneurysm treated with an endovascular approach were more likely to have a good modified Rankin scale (mRS) (mRS 0–2 vs 3–6) (p=0.028), to make a complete recovery (mRS=0) (p=0.017) and were less likely to die (mRS=6) (p=0.026). Patients with electively treated pericallosal aneurysms did not have statistically significant differences in outcome between surgical and endovascular cohorts. Differences in secondary endpoints did not reach significance.

Conclusion

Patients with ruptured pericallosal aneurysms fare better with endovascular therapy, with better chance of complete recovery. Surgical and endovascular treatments of unruptured pericallosal aneurysms have similar results and outcome.
Synchrony in marine growth among Atlantic salmon (Salmo salar) populations
Authors: Jensen Arne Johan , Fiske Peder , Hansen Lars Petter , Johnsen Bjørn Ove , Mork Kjell Arne , Næsje Tor Fredrik
Published: March 2011

More synchronous growth was observed between close, than more distantly separated populations of Atlantic salmon ( Salmo salar ), during both the first and the second year at sea. The marine growth of seven Norwegian populations, located between 60°N and 70°N, were correlated with sea surface temperatures (SSTs) in the Barents Sea, the Norwegian Sea, and the North Sea, and it was found that growth correlated best with the water temperatures in the area located closest to their home river. Growth was also compared with three broad-scale climate indices (North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation, and subpolar gyre), with the strongest relationship occurring with the NAO index. However, SSTs explained more of the variability than the climatic indices did. Growth increment for the first year, but not the second year, was higher for southern than northern populations, mainly because of later smolt migration to sea in the north, and hence, a shorter growth season. For multi-sea-winter fish, all populations except one had a negative trend in growth with years for both the first and the second year at sea. For the second year at sea, this was most pronounced after the beginning of the 1980s. This is in accordance with the negative trend in pre-fishery abundance of adult salmon during the same period.
Rates and components of carbon turnover in fish muscle: insights from bioenergetics models and a whole-lake 13C addition
Authors: Weidel Brian C. , Carpenter Stephen R. , Kitchell James F. , Vander Zanden M. Jake
Published: March 2011

Stable isotopes are widely employed to describe energy flow in aquatic communities, though interpretation of results can be confounded by the fact that organisms integrate over vastly different time scales. We used results from a 56-day whole-lake 13C addition and a bioenergetic modeling approach to estimate dorsal muscle carbon turnover rates in a natural setting for three sizes of bluegill ( Lepomis macrochirus ), largemouth bass ( Micropterus salmoides ), and yellow perch ( Perca flavescens ). Generally, dynamic δ13C models with a metabolic tissue replacement term were better supported than models predicting isotopic change from growth alone, except when relative growth rates were highest (age 0 bluegill). Across species and size classes, the percentage of carbon change due to tissue replacement was variable (2%–80%) and independent of fish size. The half-life of δ13C in age 0 fishes was similar and ranged from 8 to 18 days. In contrast, adult tissue half-lives were much longer (116–173 days). Based on these and previously published estimates, fish mass (g) was a strong predictor of fish carbon turnover rates, λ: log(λ) = –3.65 – 0.20 log(mass), r2 = 0.71.
Does selective fishing conserve community biodiversity? Predictions from a length-based multispecies model
Authors: Rochet Marie-Joëlle , Collie Jeremy S. , Jennings Simon , Hall Stephen J.
Published: March 2011

This study challenges the widely held view that improved fisheries selectivity would always help to maintain marine biodiversity. Using a length-based multi-species model, we investigate the effects of selective versus nonselective fishing on fish communities. Both size and species selectivity are examined, and fishing effects on biodiversity are measured with three indices: (i) evenness, (ii) the number of collapsed species, and (iii) an index of size diversity. The model is parameterized for the Georges Bank and North Sea fish communities. The results suggest that there is no “optimal” size selectivity to maintain biodiversity: the effects of each exploitation pattern depend on the selectivity of the gear (i.e., the shape of the selection curve) relative to the available sizes. Catching a narrow range of species almost always reduced evenness and species richness more than taking the same catch from a broader range of species. In summary, neither selective nor nonselective fishing can be said to be generally preferable for conserving biodiversity; the outcome depends on the particular species composition and size structure of the community. Advice intended to inform management will need to be based on clear definitions of biodiversity, and unambiguous management objectives for biodiversity and the fishery.
Detecting and forecasting complex nonlinear dynamics in spatially structured catch-per-unit-effort time series for North Pacific albacore (Thunnus alalunga)
Authors: Glaser Sarah M. , Ye Hao , Maunder Mark , MacCall Alec , Fogarty Michael , Sugihara George
Published: March 2011

The presence of complex, nonlinear dynamics in fish populations, and uncertainty in the structure (functional form) of those dynamics, pose challenges to the accuracy of forecasts produced by traditional stock assessment models. We describe two nonlinear forecasting models that test for the hallmarks of complex behavior, avoid problems of structural uncertainty, and produce good forecasts of catch-per-unit-effort (CPUE) time series in both standardized and nominal (unprocessed) form. We analyze a spatially extensive, 40-year-long data set of annual CPUE time series of North Pacific albacore ( Thunnus alalunga ) from 1° × 1° cells from the eastern North Pacific Ocean. The use of spatially structured data in compositing techniques improves out-of-sample forecasts of CPUE and overcomes difficulties commonly encountered when using short, incomplete time series. These CPUE series display low-dimensional, nonlinear structure and significant predictability. Such characteristics have important implications for industry efficiency in terms of future planning and can inform formal stock assessments used for the management of fisheries.
Dynamics of two sailfin sandfish (Arctoscopus japonicus) stocks in the Sea of Japan, and their management
Authors: Watanabe Kyuji , Sakuramoto Kazumi , Sugiyama Hideki , Suzuki Naoki
Published: March 2011

The dynamics of the northern and western Sea of Japan sailfin sandfish ( Arctoscopus japonicus ) stocks (NSJ and WSJ, respectively) varied simultaneously until the mid-1970s but differently thereafter. To identify the mechanisms underlying these dynamics, we evaluated the impact of environment and harvesting on NSJ by developing a recruitment model and simulating NSJ dynamics. The model was constructed based on egg production, density effect, and water temperatures in winter and spring, which correlated significantly and positively with the estimated surface mixed-layer depth. Winter water temperatures and egg production were variables common to the two stocks. Our results suggest that simultaneous dynamics resulted from similarities in variations in winter water temperatures for each stock and the difference in dynamics resulted from NSJ depletion caused by overfishing. We suggest management strategies to prevent NSJ depletion caused by unfavorable environmental conditions and overfishing, as well as to allow improved biomass recovery while taking advantage of favorable environmental conditions, and avoid further exploitation of previously depleted NSJ.
Modeling the response time of diatom assemblages to simulated water quality improvement and degradation in running waters
Authors: Lacoursière Sophie , Lavoie Isabelle , Rodríguez Marco A. , Campeau Stéphane
Published: March 2011

The objective of this study was to measure and model the response time of the Eastern Canadian Diatom Index (IDEC: Indice Diatomées de l’Est du Canada), a diatom-based index of biological integrity, following substrate translocation from altered sites (nutrient-enriched) to pristine sites and vice-versa. The frequency of sampling, duration (time after substrate translocation), and variety of site conditions in the present study provide strong evidence for an accelerated response of diatoms to a degradation reflecting eutrophication (within a week in certain cases) and a slower path to recovery (up to 4 weeks). Diatom response varied as a function of trophic status; oligotrophic rivers responded rapidly to a degradation, and mesotrophic or eutrophic rivers responded more slowly to an amelioration of the conditions. Variation in response time as a function of trophic status seemed to be partly linked to the diversity and complexity of the assemblages. The less diverse assemblages observed in oligotrophic waters were highly sensitive to nutrient enrichment, whereas the more diverse assemblages sampled in mesotrophic–eutrophic rivers were less sensitive to nutrient fluctuations, and major variations in nutrient concentrations took a longer time to induce a change in index values.
Historical abundance of Puget Sound steelhead, Oncorhynchus mykiss, estimated from catch record data
Authors: Gayeski N. , McMillan B. , Trotter P.
Published: March 2011

We used reported commercial catch data and historical information regarding unreported catches to estimate the abundance of winter steelhead, Oncorhynchus mykiss , in Puget Sound rivers in 1895, the year in which the peak commercial catch of steelhead occurred. We employed a Bayesian analysis to address the uncertainties associated with the estimation process and report abundance estimates for four large northern Puget Sound rivers and for the remaining aggregate of rivers and streams in Puget Sound. The central 90% of the posterior distribution of total abundance ranged from 485 000 to 930 000, with a mode of 622 000. Compared with the 25-year average abundance for all of Puget Sound of 22 000 for the 1980–2004 period, our results show that current abundance is likely only 1%–4% of what it was prior to the turn of the 20th century. Loss of freshwater habitat alone can account for this reduction in abundance only if there was an extraordinary decline in productivity. Our estimates of historical abundance should better inform the development of recovery goals for Puget Sound steelhead.
A comparison of polymorphism of genetic markers and population sample sizes required for mixed-stock analysis of sockeye salmon (Oncorhynchus nerka) in British Columbia
Authors: Beacham Terry D. , McIntosh B. , Wallace C. G.
Published: March 2011

We evaluated two questions: (i) do microsatellites require larger population baseline sample sizes than single nucleotide polymorphisms (SNPs) to allow the accuracy provided by the microsatellites in genetic stock identification (GSI) applications to be expressed, and (ii) do less genetically distinct populations require larger population baseline sample sizes than more distinct populations to improve population-specific accuracy in GSI applications? Forty-six SNP loci were surveyed in 40 populations of sockeye salmon ( Oncorhynchus nerka ) over 16 regions from southern and central British Columbia and were split into two groups: the top 23 SNPs evaluated for stock identification for British Columbia sockeye salmon and the poorest 23 nuclear SNPs. Fourteen microsatellites were surveyed and split into two groups, with loci from the top 7 loci for stock identification accuracy assembled in one group, and the remaining 7 microsatellites assigned to a second group. SNPs and microsatellites with lower stock identification power required larger population sample sizes to allow expression of stock identification potential. To achieve the same level of population-specific accuracy, SNPs required fewer individuals to be sampled in a population than did microsatellites. Less genetically distinct populations required larger population sample sizes to achieve a given level of accuracy in estimated stock compositions.
Reduced recruitment performance in natural populations of anadromous salmonids associated with hatchery-reared fish
Authors: Chilcote M. W. , Goodson K. W. , Falcy M. R.
Published: March 2011

We found a negative relationship between the reproductive performance in natural, anadromous populations of steelhead trout ( Oncorhynchus mykiss ), coho salmon ( O. kisutch ), and Chinook salmon ( O. tshawytscha ), and the proportion of hatchery fish in the spawning population. We used intrinsic productivity as estimated from fitting a variety of recruitment models to abundance data for each population as our indicator of reproductive performance. The magnitude of this negative relationship is such that we predict the recruitment performance for a population composed entirely of hatchery fish would be 0.128 of that for a population composed entirely of wild fish. The effect of hatchery fish on reproductive performance was the same among all three species. Further, the impact of hatchery fish from “wild type” hatchery broodstocks was no less adverse than hatchery fish from traditional, domesticated broodstocks. We also found no support for the hypothesis that a population's reproductive performance was affected by the length of exposure to hatchery fish. In most cases, measures that minimize the interactions between wild and hatchery fish will be the best long-term conservation strategy for wild populations.
Olfactory-mediated stream-finding behavior of migratory adult sea lamprey (Petromyzon marinus)
Authors: Vrieze Lance A. , Bergstedt Roger A. , Sorensen Peter W.
Published: March 2011

Stream-finding behavior of adult sea lamprey ( Petromyzon marinus ), an anadromous fish that relies on pheromones to locate spawning streams, was documented in the vicinity of an important spawning river in the Great Lakes. Untreated and anosmic migrating sea lampreys were implanted with acoustic transmitters and then released outside the Ocqueoc River. Lampreys swam only at night and then actively. When outside of the river plume, lampreys pursued relatively straight bearings parallel to the shoreline while making frequent vertical excursions. In contrast, when within the plume, lampreys made large turns and exhibited a weak bias towards the river mouth, which one-third of them entered. The behavior of anosmic lampreys resembled that of untreated lampreys outside of the plume, except they pursued a more northerly compass bearing. To locate streams, sea lampreys appear to employ a three-phase odor-mediated strategy that involves an initial search along shorelines while casting vertically, followed by river-water-induced turning that brings them close to the river’s mouth, which they then enter using rheotaxis. This novel strategy differs from that of salmonids and appears to offer this poor swimmer adaptive flexibility and suggests ways that pheromonal odors might be used to manage this invasive species.
RECOGNITION OF POSTAL CODES FROM FINGERSPELLING VIDEO SEQUENCE
Authors: SURAJ M. G. , GURU D. S. , MANJUNATH S.
Published: March 2011

In this paper, we present a methodology for recognizing fingerspelling signs in videos. A novel approach of user specific appearance model is proposed for improved recognition performance over the classical appearance based model. Fingerspelt postal index number (PIN) code signs in a video are recognized by identifying the signs in the individual frames of a video. Decomposition of a video into frames results in a large number of frames even for a video of short duration. Each frame is processed to get only the hand frame. This results in a series of hand frames corresponding to each video frame. The obtained series of hand frames consists of frames that are very similar to the neighboring frames and hence are redundant. Therefore, only a few hand frames can be selected and used for recognizing the PIN code signed by a signer. We propose two methods for the selection of images from a video sequence. The methods give a basis for selection of images and have been thoroughly tested to show their benefit in terms of appropriate selection of images and reduction in number of images when compared to arbitrary selection of images.
TACKLING THE PROBLEM OF INVARIANT TEXTURE RETRIEVAL USING MULTIPLE STRATEGIES
Authors: ABBADENI NOUREDDINE , ALHICHRI HAIKEL S. , ELMASRY ALAA B.
Published: March 2011

We present in this paper an approach based on multiple strategies to tackle the problem of invariance in the framework of texture-based image retrieval. This approach, rather than to consider invariance at the representation level, considers it at the query level. We use two models to represent the visual content of textures, namely, the autoregressive model and a perceptual model based on a set of perceptual features. The perceptual model is used with two viewpoints: the original image's viewpoint and the autocovariance function viewpoint. After a brief presentation and discussion of these multiple representation models/viewpoints, we present the invariant texture retrieval algorithm. This algorithm considers results fusion (merging) at two different levels: (1) the first level consists in merging results returned by different models/viewpoints (representations) for the same query in one results list using a linear results fusion model; (2) the second level consists in merging each fused list of different queries into a unique fused list using a round robin fusion scheme. Experimental retrieval results and benchmarking based on the precision/recall measures applied on a large image database show interesting results.
MULTI-APPROACH SATELLITE IMAGES FUSION BASED ON BLIND SOURCES SEPARATION
Authors: BOULILA WADII , FARAH IMED RIADH
Published: March 2011

The development of satellite image acquisition tools helped improving the extraction of information about natural scenes. In the proposed approach, we try to minimize imperfections accompanying the image interpretation process and to maximize useful information extracted from these images through the use of blind source separation (BSS) and fusion methods. In order to extract maximum information from multi-sensor images, we propose to use three algorithms of BSS that are FAST- ICA2D, JADE2D, and SOBI2D. Then by employing various fusion methods such as the probability, possibility, and evidence methods we can minimize both imprecision and uncertainty. In this paper, we propose a hybrid approach based on five main steps. The first step is to apply the three BSS algorithms to the satellites images; it results in obtaining a set of image sources representing each a facet of the land cover. A second step is to choose the image having the maximum of kurtosis and negentropy. After the BSS evaluation, we proceed to the training step using neural networks. The goal of this step is to provide learning regions which are useful for the fusion step. The next step consists in choosing the best adapted fusion method for the selected source images through a case-based reasoning (CBR) module. If the CBR module does not contain a case similar to the one we are seeking, we proceed to apply the three fusion methods. The evaluation of fusion methods is a necessary step for the learning process of our CBR.
RATIONAL POINTS ON SOME HYPER- AND SUPERELLIPTIC CURVES
Authors: BREMNER ANDREW , ULAS MACIEJ
Published: March 2011

We construct families of certain hyper- and superelliptic curves that contain a (small) number of rational points. This leads to lower bounds for the ranks of Jacobians of certain high genus curves.
RÉDEI FIELDS AND DYADIC EXTENSIONS
Authors: BRINK DAVID
Published: March 2011

For an arbitrary non-square discriminant D, the Rédei fieldΓ0(D) is introduced as an extension of [Formula: see text] analogous to the genus field and connected with the Rédei–Reichardt Theorem. It is shown how to compute Rédei fields, and this is used to find socles of dyadic extensions of K for negative D. Finally, a theorem and two conjectures are presented relating the fields [Formula: see text] and [Formula: see text] for an odd prime p.
A WEIGHTED WEYL LAW FOR THE MODULAR SURFACE
Authors: LI XIAOQING
Published: March 2011

In this paper, we will prove a Weyl law for the modular surface weighted by the first Fourier coefficient of the Maass cusp forms. Our error term corresponds to the best known error term in the Weyl law and improves a previous result of Kuznetsov.
THE FRACTIONAL GALOIS IDEAL FOR ARBITRARY ORDER OF VANISHING
Authors: BUCKINGHAM PAUL
Published: March 2011

We propose a candidate, which we call the fractional Galois ideal after Snaith's fractional ideal, for replacing the classical Stickelberger ideal associated to an abelian extension of number fields. The Stickelberger ideal can be seen as gathering information about those L-functions of the extension which are non-zero at the special point s = 0, and was conjectured by Brumer to give annihilators of class-groups viewed as Galois modules. An earlier version of the fractional Galois ideal extended the Stickelberger ideal to include L-functions with a simple zero at s = 0, and was shown by the present author to provide class-group annihilators not existing in the Stickelberger ideal. The version presented in this paper deals with L-functions of arbitrary order of vanishing at s = 0, and we give evidence using results of Popescu and Rubin that it is closely related to the Fitting ideal of the class-group, a canonical ideal of annihilators.

Finally, we prove an equality involving Stark elements and class-groups originally due to Büyükboduk, but under a slightly different assumption, the advantage being that we need none of the Kolyvagin system machinery used in the original proof.
MEMORY EFFICIENT HYPERELLIPTIC CURVE POINT COUNTING
Authors: HUBRECHTS HENDRIK
Published: March 2011

In recent algorithms that use deformation in order to compute the number of points on varieties over a finite field, certain differential equations of matrices over p-adic fields emerge. We present a novel strategy to solve this kind of equations in a memory efficient way. The main application is an algorithm requiring quasi-cubic time and only quadratic memory in the parameter n, that solves the following problem: for E a hyperelliptic curve of genus g over a finite field of extension degree n and small characteristic, compute its zeta function. This improves substantially upon Kedlaya's result which has the same quasi-cubic time asymptotic, but requires also cubic memory size.
LOSS DETERMINATION METHODOLOGY FOR A PIEZOELECTRIC CERAMIC: NEW PHENOMENOLOGICAL THEORY AND EXPERIMENTAL PROPOSALS
Authors: UCHINO KENJI , ZHUANG YUAN , URAL SEYIT O.
Published: March 2011

The key factor to the miniaturization of piezoelectric devices is power density, which is limited by the heat generation or loss mechanisms. There are three loss components in general in piezoelectric vibrators/resonators, i.e., dielectric, elastic and piezoelectric losses. The mechanical quality factor, determined by these three factors, is the Figure Of Merit (FOM) in the sense of loss or heat generation. In this paper, we introduce a new loss phenomenology and innovative measuring methods based on the theory. First, quality factors at resonance and antiresonance for the k31, k33, ktand k15vibration modes are derived theoretically, and the methodology for determining loss factors in various orientations (i.e., loss anisotropy) is provided. For simplicity, we focus on materials with ∞ mm (equivalent to 6 mm) crystal symmetry for deriving the loss factors of a polycrystalline ceramic, and 14 different loss factors among 20 in total can be obtained from the measurements. Second, we propose the experimental methods for measuring both mechanical quality factors QAand QBat the resonance and antiresonance modes: a continuous admittance/impedance spectrum measuring method (traditional with temperature rise) and a burst mode (to circumvent the temperature effect).
APPROACHES FOR A RELIABLE COMPOSITIONAL ANALYSIS OF ALKALINE-BASED LEAD-FREE PEROVSKITE CERAMICS USING MICROANALYTICAL METHODS
Authors: BENČAN ANDREJA , TCHERNYCHOVA ELENA , ŠTURM SAŠO , SAMARDŽIJA ZORAN , MALIČ BARBARA , KOSEC MARIJA
Published: March 2011

The article describes the approaches for a reliable, quantitative compositional analysis of lead-free perovskite ceramics in powder and bulk forms that contain volatile alkaline compounds. The combination of scanning electron microscopy (SEM) and transmission electron microcopy (TEM) with electron-probe analytical techniques, such as energy-dispersive X-ray spectroscopy (EDS), wavelength-dispersive X-ray spectroscopy (WDS) and electron-energy-loss spectroscopy (EELS) makes it possible to determine the true chemical composition, from precursor powders to synthesized ceramics or single crystals. The microscale (SEM) and nanoscale (TEM) analytical methods also give an insight into the local variations of the chemical composition.
SYNTHESIS OF LEAD FREE SODIUM BISMUTH TITANATE (NBT) CERAMIC BY CONVENTIONAL AND MICROWAVE SINTERING METHODS
Authors: RAMANA M. VENKATA , KIRAN S. ROOPAS , RAMAMANOHAR REDDY N. , SIVA KUMAR K. V. , MURTHY V. R. K. , MURTY B. S.
Published: March 2011

Dielectric studies were carried out on a lead free Sodium Bismuth Titanate, NBT, ( Na 0.5 Bi 0.5 TiO 3) composition. The material was synthesized by conventional ceramic method (CS) and microwave sintering (MS). The presence of single phase has been confirmed by X-ray diffraction and scanning electron microscopy of NBT ceramic. The later technique (MS) resulted in material with high density, dielectric properties and improved microstructure. The transition temperature was observed slightly higher for microwave sintered (MS) material. Longitudinal modulus measurements are very sensitive property to identify the phase transitions in ceramics. Longitudinal modulus (L) measurements were also employed on these samples in the frequency 136 kHz and can be studied in the wide temperature range 30°C to 400°C. The elastic behavior (L) showed a break at two temperatures (~200°C and 350°C) in both the conventional and microwave sintered ceramics. In NBT ceramics, permittivity anomalies are connected to modulus anomalies. The results are correlated with the dielectric measurements. This behavior explained in the light of structural phase transitions in the ferroelectric ceramics.
HIGH PIEZOELECTRIC PERFORMANCE AND RELEVANT PHYSICAL MECHANISM OF CuO-MODIFIED Ba(Ti0.96Sn0.04)O3 CERAMICS
Authors: ZHANG JIALIANG , ZHANG ZONG , SHAO SHOUFU , ZHENG PENG , WANG CHUNLEI
Published: March 2011

Ba ( Ti 0.96 Sn 0.04) O 3 and CuO -modified Ba ( Ti 0.96 Sn 0.04) O 3 ceramics were prepared by the solid state reaction technique. Their piezoelectric properties were investigated and compared with those of the recently obtained high-d33 BaTiO 3 ceramic. It has been found that simply substituting Ti 4+ with Sn 4+ worsens severely the piezoelectric properties whereas a combined usage of CuO additive greatly improves the overall piezoelectric performance. CuO -modified Ba ( Ti 0.96 Sn 0.04) O 3 ceramic shows excellent piezoelectric properties of d33 = 390 pC/N , k p = 0.49 and k33 = 0.67 at room temperature. Furthermore, it possesses weak temperature dependences of electromechanical coefficients between -20°C and 55°C and a good thermal aging stability down to a low experimental temperature limit of -50°C and up to 90°C. Detailed analysis suggests that its high piezoelectric performance should be largely ascribed to the ideal microstructure of high relative density and small grains and the corresponding domain configurations.