bluuebunny/crossref_metadata_2025 huggingface dataset:
Bowhead whale (Balaena mysticetus) songs in the Chukchi Sea between October 2007 and May 2008
Authors: Delarue Julien , Laurinolli Marjo , Martin Bruce
Published: December 2009

This paper reports on the acoustic detection of bowhead whale (Balaena mysticetus) songs from the Bering-Chukchi-Beaufort stock, including the first recordings of songs in the fall and early winter. Bowhead whale songs were detected almost continuously in the Chukchi Sea between October 30, 2007 and January 1, 2008 and twice from April 16 to May 5, 2008 during a long-term deployment of five acoustic recorders moored off Point Lay and Wainwright, AK, between October 21, 2007 and August 3, 2008. Two complex and four simple songs were detected. The complex songs consisted of highly stereotyped sequences of four units. The simple songs were primarily made of sequences of two to three moan types whose repetition patterns were constant over short periods but more variable over time. Multiple song types were recorded simultaneously and there is evidence of synchronized song variation over time. The implications of the spatiotemporal distribution of song detection with respect to the migratory and mating behavior of western Arctic bowheads are discussed.
What makes a melody: The perceptual singularity of pitch sequences
Authors: Cousineau Marion , Demany Laurent , Pressnitzer Daniel
Published: December 2009

This study investigated the ability of normal-hearing listeners to process random sequences of tones varying in either pitch or loudness. Same/different judgments were collected for pairs of sequences with a variable length (up to eight elements) and built from only two different elements, which were 200-ms harmonic complex tones. The two possible elements of all sequences had a fixed level of discriminability, corresponding to a d′ value of about 2, irrespective of the auditory dimension (pitch or loudness) along which they differed. This made it possible to assess sequence processing per se, independent of the accuracy of sound encoding. Pitch sequences were found to be processed more effectively than loudness sequences. However, that was the case only when the sequence elements included low-rank harmonics, which could be at least partially resolved in the auditory periphery. The effect of roving and transposition was also investigated. These manipulations reduced overall performance, especially transposition, but an advantage for pitch sequences was still observed. These results suggest that automatic frequency-shift detectors, available for pitch sequences but not loudness sequences, participate in the effective encoding of melodies.
Pinna-rim skin folds narrow the sonar beam in the lesser false vampire bat (Megaderma spasma)
Authors: Wang Xiaobin , Müller Rolf
Published: December 2009

False vampire bats (genus Megaderma) employ active as well as passive biosonars. In the present work, the acoustic impact of a conspicuous feature of the animals’ ear morphology, skin folds of the pinna rim linking the two pinnae at the midline, has been studied using a numerical approach. Automated methods have been devised to measure the largest width of the beam patterns irrespective of beam orientation. A total of six pinna shapes from three individuals have been studied. For all these shapes, it was found that the reception biosonar beams had approximately elliptic cross-sections with the largest beamwidth being on average almost twice as large as the beamwidth in the orthogonal direction. The directions of the largest beamwidths were scattered around the azimuthal dimension. Removal of the skin folds resulted in significant widening of the beams along their widest dimensions with an increase in beamwidth of 9.2° (a 30% change) on average. The strength and repeatability of this effect across individuals suggest the hypothesis that skin folds are functionally relevant to the animals’ biosonar system. It may be a morphological adaptation to biosonar tasks that benefit from a narrow beam such as the detection of faint sounds or precise localization.
The dynamic range of speech, compression, and its effect on the speech reception threshold in stationary and interrupted noise
Authors: Rhebergen Koenraad S. , Versfeld Niek J. , Dreschler Wouter. A.
Published: December 2009

Changes in the speech reception threshold (SRT) after amplitude compression of speech or speech in noise may be due to changes in the dynamic range of the speech signal. However, current models set up to predict the speech intelligibility consider the dynamic range of speech to be fixed regardless of the type of compression. The present paper describes two experiments with normal-hearing subjects to examine the effect of the dynamic range on the SRT in stationary and interrupted noise after wide dynamic range compression. The dynamic range has been varied by compression or expansion of only the speech signal, leaving the masking noise unaltered, or by compression or expansion of the mixed speech-in-noise signal. The results show that compression affects the SRT, both in a positive or a negative direction, not only due to dynamic range but also due to distortion of the speech signal.
Acoustic analysis of primate air sacs and their effect on vocalization
Authors: de Boer Bart
Published: December 2009

This paper presents an analysis of the acoustic impedance of primate air sacs and their interaction with the vocal tract. A lumped element model is derived and it is found that the inertance of the neck and the volume of the air sac are relevant, as well as the mass and stiffness of the walls (depending on the tissue). It is also shown that at low frequencies, radiation from the air sac can be non-negligible, even if the mouth is open. It is furthermore shown that an air sac can add one or two low resonances to the resonances of the oral tract, and that it shifts up the oral tract’s resonances below approximately 2000 Hz, and shifts them closer together. The theory was verified by acoustic measurements and applied to the red howler monkey (Alouatta seniculus) and the siamang (Symphalangus syndactylus). The theory describes the physical models and the siamang calls correctly, but appears incomplete for the howler monkey vocalizations. The relation between air sacs and the evolution of speech is discussed briefly, and it is proposed that an air sac would reduce the ability to produce distinctive speech, but would enhance the impression of size of the vocalizer.
Frequency dependence of average phase shift from human calcaneusin vitro
Authors: Wear Keith A.
Published: December 2009

If dispersion in a medium is weak and approximately linear with frequency (over the experimental band of frequencies), then it can be shown that the constant term in a polynomial representation of phase shift as a function of frequency can produce errors in measurements of phase-velocity differences in through-transmission, substitution experiments. A method for suppressing the effects of the constant phase shift in the context of the single-wave-model was tested on measurements from 30 cancellous human calcaneus samples in vitro. Without adjustment for constant phase shifts, the estimated phase velocity at 500 kHz was 1516±6 m/s (mean±standard error), and the estimated dispersion was −24±4 m/s MHz (mean±standard error). With adjustment for constant phase shifts, the estimated mean velocity decreased by 4–9 m/s, and the estimated magnitude of mean dispersion decreased by 50%–100%. The average correlation coefficient between the measured attenuation coefficient and frequency was 0.997±0.0026 (mean±standard deviation), suggesting that the signal for each sample was dominated by one wave. A single-wave, linearly dispersive model conformed to measured complex transfer functions from the 30 cancellous-bone samples with an average root-mean-square error of 1.9%±1.0%.
Eigenmodal resonances of polydisperse bubble systems on a rigid boundary
Authors: Illesinghe Suhith , Ooi Andrew , Manasseh Richard
Published: December 2009

This paper presents theory and experimental data on the resonance frequency of systems consisting of different-sized air bubbles attached to a rigid wall. Effects of the change in resonant frequency with bubble size and distance between the bubbles were studied. It was found that the symmetric mode resonance frequency of the bubble system decreased with increasing r=R02∕R01, where R01 and R02 are the equilibrium radii of bubbles in the system. Both the symmetric and antisymmetric modes of oscillation were detected in the experiments, with the resonant frequency of the symmetric mode dominant at small bubble separation and the frequency of the antisymmetric mode dominant when the bubbles were farther apart. A linear coupled-oscillator theoretical model was used to describe the oscillations of the bubble system, in which the method of images was used to approximate the effects of the wall. It was found that there was fair to good agreement between the predictions of the coupled-oscillator model with the experimental data.
Automatic recognition of fin and blue whale calls for real-time monitoring in the St. Lawrence
Authors: Mouy Xavier , Bahoura Mohammed , Simard Yvan
Published: December 2009

Monitoring blue and fin whales summering in the St. Lawrence Estuary with passive acoustics requires call recognition algorithms that can cope with the heavy shipping noise of the St. Lawrence Seaway and with multipath propagation characteristics that generate overlapping copies of the calls. In this paper, the performance of three time-frequency methods aiming at such automatic detection and classification is tested on more than 2000 calls and compared at several levels of signal-to-noise ratio using typical recordings collected in this area. For all methods, image processing techniques are used to reduce the noise in the spectrogram. The first approach consists in matching the spectrogram with binary time-frequency templates of the calls (coincidence of spectrograms). The second approach is based on the extraction of the frequency contours of the calls and their classification using dynamic time warping (DTW) and the vector quantization (VQ) algorithms. The coincidence of spectrograms was the fastest method and performed better for blue whale A and B calls. VQ detected more 20 Hz fin whale calls but with a higher false alarm rate. DTW and VQ outperformed for the more variable blue whale D calls.
Post-processing of guided wave array data for high resolution pipe inspection
Authors: Velichko Alexander , Wilcox Paul D.
Published: December 2009

This paper describes a method for processing data from a guided wave transducer array on a pipe. The raw data set from such an array contains the full matrix of time-domain signals from each transmitter-receiver combination. It is shown that for certain configurations of an array, the total focusing method can be applied, which allows the array to be focused at every point on a pipe in both transmission and reception. The effect of array configuration parameters on the sensitivity of the proposed method to random and coherent noise is discussed. Experimental results are presented using electromagnetic acoustic transducers for exciting and detecting the S0 Lamb wave mode in a 12-in. diameter steel pipe at 200 kHz excitation frequency. The results show that using the imaging algorithm, a 2-mm (0.08 wavelength) diameter half-thickness hole can be detected.
Design and evaluation of digital signal processing algorithms for acoustic feedback and echo cancellation
Authors: van Waterschoot Toon
Published: December 2009

This thesis deals with several open problems in acoustic echo cancellation and acoustic feedback control. Our main goal has been to develop solutions that provide a high performance and sound quality, and behave in a robust way in realistic conditions. This can be achieved by departing from the traditional ad-hoc methods, and instead deriving theoretically well-founded solutions, based on results from parameter estimation and system identification. In the development of these solutions, the computational efficiency has permanently been taken into account as a design constraint, in that the complexity increase compared to the state-of-the-art solutions should not exceed 50% of the original complexity.Full text available at http://hdl.handle.net/1979/2599
Acoustic measurements of clay-size particles
Authors: Carpenter Wayne O. , Chambers James P. , Wren Daniel G. , Kuhnle Roger A. , Diers Jeffrey A.
Published: December 2009

Knowledge of sediment concentration is important in the study of streams and rivers. The work presented explores using high frequency (20 MHz) acoustic signal attenuation to measure the concentration of fine sediment particles (0.2–5.0 μm) in a fluvial environment. A small laboratory tank with a pitch-catch transducer configuration measured a 35 dB change in signal level over a wide range of kaolinite and bentonite concentrations (1–14 g/l) over a range of distances (180–357 mm). The data suggest that a fixed distance of 180 mm between the transducers will be capable of measuring the entire range of concentrations.
On the use of leaky modes in open waveguides for the sound propagation modeling in street canyons
Authors: Pelat Adrien , Félix Simon , Pagneux Vincent
Published: December 2009

An urban, U-shaped, street canyon being considered as an open waveguide in which the sound may propagate, one is interested in a multimodal approach to describe the sound propagation within. The key point in such a multimodal formalism is the choice of the basis of local transversal modes on which the acoustic field is decomposed. For a classical waveguide, with a simple and bounded cross-section, a complete orthogonal basis can be analytically obtained. The case of an open waveguide is more difficult, since no such a basis can be exhibited. However, an open resonator, as displays, for example, the U-shaped cross-section of a street, presents resonant modes with complex eigenfrequencies, owing to radiative losses. This work first presents how to numerically obtain these modes. Results of the transverse problem are also compared with solutions obtained by the finite element method with perfectly mathed layers. Then, examples are treated to show how these leaky modes can be used as a basis for the modal decomposition of the sound field in a street canyon.
Time domain normal mode analysis of underwater acoustic wave propagation for a single layered acoustic channel in two dimensional Cartesian coordinates
Authors: Özkan Sertlek Hüseyin
Published: December 2009

A new analytical time domain Normal Mode solution in a single layer acoustic waveguide in Cartesian coordinates is presented in the thesis. The method is based on the separation of variables technique for the two dimensional time domain wave equation. After separation, Sturm-Liouville type ordinary differential equation for depth dependency and inhomogeneous Klein-Gordon type partial differential equation for time and range dependency are obtained. Whenever the ordinary differential equation is solved in a classical manner with the application of Dirichlet boundary condition on the upper and lower boundaries of the waveguide, Inhomogeneous Klein-Gordon type partial differential equation is solved by using the Green function technique in time domain. Then the exact solution satisfying the causality principle is constructed for the acoustic pressure. The main advantage of the proposed causal solution is not necessary to use the Fourier Transformation to obtain time domain response of arbitrary acoustical source signals having the monochromatic and Gaussian pulse type time dependency in the waveguide. The excellent agreement for the comparisons of the range dependent transmission losses is observed between the proposed solution and the KRAKEN program.
The influence of structural-acoustic coupling on the dynamic behaviour of a one- dimensional vibro-acoustic system
Authors: Kim Gihwan
Published: December 2009

The aim of this thesis is to investigate the structural-acoustic coupling effects on the dynamic behavior of a vibro-acoustic system under passive/active control. The simplest model of a vibro-acoustic system one can consider is a one-dimensional acoustic cavity driven by a single-degree-of-freedom (SDOF) structure. This simple model is used to demonstrate the physical characteristics of the coupling phenomenon. This simple analytical model can provide various degrees of structural-acoustic coupling, which are dependent upon (i) the structural-acoustic stiffness ratio, (ii) structural-acoustic natural frequency ratio, (iii) structural damping, and (iv) acoustic damping. In this case, although the geometric coupling factor is not included because the SDOF structure has a single mode, 80 percent of the factors that determine the degree of coupling can be accounted for by the simple analytical model. The coupling mechanism, in the simple vibro-acoustic system, is investigated using the mobility-impedance approach. In order to provide the threshold of the degree of coupling, a coupling factor is calculated in terms of non-dimensional structural-acoustic parameters. Vibro-acoustic responses are represented by the acoustic potential energy in the cavity and the kinetic energy of the structure coupled to the acoustic cavity.Full text available at http://eprints.soton.ac.uk/65676/
Estimation of antioxidative properties of tea leaves by abrasive stripping electrochemistry using paraffin-impregnated graphite electrode
Authors: Komorsky-Lovrić Šebojka , Novak Ivana
Published: December 2009

Electrooxidation potentials of powdered green and black teas were determined by abrasive stripping voltammetry. A circular surface of paraffin-impregnated graphite rod was contaminated with tea microparticles and used as a chemically prepared working electrode in square-wave voltammetric experiments. The responses are ascribed to electrooxidation of flavanols in teas. Low oxidation potentials of some green teas were observed. An advantage of the proposed method is that no extraction of electroactive components is necessary.
Adsorption of tert-butyl alcohol at the Hg|aqueous perchlorate interface in the presence of tetramethylthiourea
Authors: Gugała-Fekner Dorota , Fekner Zygmunt , Nieszporek Jolanta , Sieńko Dorota , Saba Jadwiga
Published: December 2009

The electrosorption behavior of tert-butyl alcohol at the mercury|aqueous NaClO4– tetramethylthiourea was determined by a double layer differential capacity measurement. Adsorption of tert-butyl alcohol was analyzed using the constants obtained from the modified Flory–Huggins and virial isotherm. An increase in the relative surface excess for tert- butyl alcohol with increasing NaClO4 concentration in the range from 0.1 to 1.0 M was confirmed. The observed effect may be the result of the weakest repulsive interaction between adsorbed tert-butyl alcohol molecules in 1.0 M NaClO4 with 0.05 M tetramethylthiourea.
Extrapolating strong ground motion of the Silakhor earthquake (ML 6.1), Iran, using the empirical Green's function (EGF) approach based on a genetic algorithm
Authors: Nicknam Ahmad , Abbasnia Reza , Eslamian Yasser , Bozorgnasab Mohsen
Published: December 2009

The main objectives of this article are to develop a technique to find source models that allow one to replicate observed strong ground motion records and to extrapolate strong ground motion synthesis to locations where strong motion was not recorded. A technique including the well known empirical Green’s function (EGF) approach along with a genetic algorithm is used, which allows the optimization of differences between the synthesized and observed ground shakings. The technique used is performed by comparing the elastic response spectra of observed seismograms at two stations with those of simulated data using the EGF method incorporating recorded aftershocks taken at each station. Moreover, a genetic algorithm approach is used to reduce differences between the simulated and recorded data in the form of elastic response spectra by changing the input parameters in the admissible ranges. To validate the proposed approach the three components of strong motion recorded at other stations were synthesized incorporating the input parameters obtained at previous stations. A comparatively good match of the simulated and recorded response spectra confirms the ability of the proposed technique to generate synthetic seismograms with suitable elastic response spectra.
Depositional setting, fossil flora, and paleoenvironment of the Early Eocene Falkland site, Okanagan Highlands, British Columbia
Authors: Smith Robin Y. , Basinger James F. , Greenwood David R.
Published: December 2009

The fossil flora and depositional setting of the Early Eocene Falkland site in the southern interior of British Columbia, Canada, is reported in detail for the first time, using a census sampling approach. The Falkland site is part of the series of Okanagan Highlands fossil localities in British Columbia and Washington State that represent relatively cool upland environments within the context of the greenhouse world of the Early Eocene, providing microthermal (mean annual temperature (MAT) < 13 °C) climatic conditions for the establishment of cool-adapted plants geographically adjacent to subtropical elements from lowland floras. Plant community composition of the Falkland flora is most similar to the Republic (Washington) and McAbee (British Columbia) floras based on high Sørenson similarity coefficients, together forming a southern cluster of Okanagan Highlands sites. The site is a lacustrine deposit that formed in a volcanically active landscape. Paleoclimate reconstructions based on leaf physiognomy characterize the site as microthermal (MAT 8.9 ± 2.0 °C by leaf margin analysis or 11.9 ± 2.0 °C by climate leaf analysis multivariate program (CLAMP)), mesic (mean annual precipitation (MAP) 114 [Formula: see text]cm/year), and equable (cold month mean temperature (CMMT) 3.0 ± 2.0 °C). Paleoelevation of the site is estimated to be similar to or slightly higher than modern levels (>1.3 km) during the Early Eocene. The Falkland locality adds new data to the temporal, latitudinal, and altitudinal gradients of the Okanagan Highlands series, reflecting the regional landscape of northwestern North America during the warmest period of the Cenozoic.
Magmatic affinity of modern and ancient subalkaline volcanic rocks determined from trace-element discriminant diagrams
Authors: Ross Pierre-Simon , Bédard Jean H.
Published: December 2009

When dealing with ancient subalkaline volcanic rocks, the alkali – total iron – magnesium (AFM) diagram is of limited use in assigning a tholeiitic versus calc-alkaline affinity because these elements are often mobile during alteration and metamorphism. Classification diagrams using immobile trace elements are preferable but need to be tested and optimized on unaltered rocks. To this end, a geochemical database containing over a thousand, presumed unaltered, subalkaline volcanic samples from young oceanic arcs was assembled. The data were classified using both major and trace-element approaches, and the results were compared. If the calc-alkaline and tholeiitic fields on the AFM diagram are used to define magmatic affinity, then the commonly used Zr versus Y, La versus Yb, and Th versus Yb discriminant diagrams misclassify 39%, 24%, and 28% of samples, respectively. After optimization (using a number of criteria), all three trace-element classification diagrams produce results that are generally consistent with the AFM diagram. The optimized diagrams only misclassify 7%, 11%, and 12% of the samples, respectively. A new Th/Yb versus Zr/Y diagram has a better overall performance than any single ratio diagram and may prove helpful in assigning magmatic affinities to volcanic rocks in ancient successions.
Groundwater recharge trends in CanadaGeological Survey of Canada Contribution 20090009.
Authors: Rivard Christine , Vigneault Harold , Piggott Andrew R. , Larocque Marie , Anctil François
Published: December 2009

Groundwater plays a major role in social and economic development and in human and ecosystem health. However, little is known about the potential impacts of climate change on this resource in Canada, namely if groundwater recharge is increasing or decreasing over time. This paper focuses on trend statistical analysis of historical series of baseflow and groundwater levels and their field significance as indicators of recharge. Monitoring wells are mainly located in the southern half of western Canada, where few gauging stations either are available or provide significant trends. Both data sets are thus complementary. Results show that most available groundwater level series have significant trends (80%), whereas most available baseflow series have not (3%–33%). However, groundwater level series usually show smaller slope magnitudes than baseflow series. Mixed trends are often observed across Canada for a given variable, period, or series length, although some regions can have marked trends. For instance, values below the 55°N latitude, and especially values in Atlantic Canada, show mostly downward trends (decreasing recharge). Values north of the 55° parallel often show upward trends. All groundwater level results are field significant at the 10% level, versus only 35% for baseflow results, but they show mixed results. Baseflow values show a majority of downward trends for annual values and the summer period for 40- and 50-year series, thus showing field significance, whereas mixed results are observed for 30-year series and the spring, fall, and winter seasons.
Estimating thresholds to optimal harvest rate for long-lived, low-fecundity sharks accounting for selectivity and density dependence in recruitment
Authors: Forrest Robyn E. , Walters Carl J.
Published: December 2009

Deepwater dogsharks (Order Squaliformes) are thought to be particularly vulnerable to overfishing due to life history strategies that place them at the lower end of the shark productivity spectrum. Sharks frequently have relatively low value in multispecies fisheries, where management is usually aimed at maintaining harvest of more valuable and productive teleosts. This results in low priority being given to data collection for sharks and hampers identification of appropriate harvest strategies. Here an age-structured model with maximum sustainable harvest rate (UMSY) as leading productivity parameter is systematically applied to show that for certain growth and reproductive schedules that apply to some sharks, the range of possible values that can be taken by UMSYcan become very small. The model was applied to 12 Australian dogshark species and was used to show that UMSYis highly constrained under some selectivity schedules. Results were consistent with estimates of the intrinsic rate of growth obtained using a demographic model, suggesting that there may be more certainty about UMSYthan expected for many shark species, given uncertainty in recruitment parameters. The approach could be used to inform policy for some sharks and may be useful in the development of informative Bayesian priors for assessment models.
Estimating fish abundance from acoustic surveys: calculating variance due to acoustic backscatter and length distribution error
Authors: Zwolinski Juan , Fernandes Paul G. , Marques Vítor , Stratoudakis Yorgos
Published: December 2009

Estimation of fish abundance from acoustic surveys requires the estimation of total acoustic backscatter of the target species in the sampled region. Although the arithmetic mean of acoustic backscatter is an unbiased estimator of the mean backscatter for regular or random sampling designs, under the presence of spatial structure, its use leads to a loss of information and the estimation of its variance is not trivial. Here, we tackle these shortcomings by building a spatial model of acoustic backscatter using spline-based generalized additive models (GAMs). GAMs were used to provide local and global estimates of acoustic backscatter, and their precision was calculated by statistical simulations of the models’ parameters. For a series of surveys performed off the western and southern Iberian Peninsula, GAM estimates were unbiased and more precise than the arithmetic mean estimates. Simulations of the acoustic backscatter fields were combined with resampling of the trawls to provide confidence intervals for fish numbers and biomass. The relative standard errors of the estimates were within 13% and 46% (average 22%) for numbers and within 12% and 35% (average 19%) for biomass. Acoustic sampling error was the major contributor to the overall variance.
Development of successful fish passage structures for downstream migrants requires knowledge of their behavioural response to accelerating flow
Authors: Enders Eva C. , Gessel Michael H. , Williams John G.
Published: December 2009

Fish have evolved intrinsic flight responses, allowing pre-emptive avoidance of potentially threatening situations. To direct downstream migrant fish away from deleterious conditions at dams and other barriers, mechanical devices such as travelling screens and fish bypass systems are often installed. However, field observations suggest that if these structures create areas of rapidly accelerating flow, they do not effectively guide the fish. We studied the avoidance behaviour of actively migrating fall Chinook salmon ( Oncorhynchus tshawytscha ) smolts in controlled experiments of low-, medium-, and high-flow accelerations. We measured the response velocity (VR) and the velocity gradient (VG) over body length. Although VRvaried significantly with flow conditions and increased with increasing water temperature, the median VG at the instant at which smolts displayed an avoidance response was similar over the range of accelerating flows tested. Results from this study present the first quantitative information about the avoidance behaviour of fish to flow acceleration and should provide data needed to help engineers and biologists develop effective systems to alleviate anthropogenically altered flow regimes. Furthermore, the devised experimental setup provides a valuable means to test the effects of accelerating flow on any downstream migrant fish species.
The impact of regime shifts on the performance of management strategies for the Gulf of Alaska walleye pollock (Theragra chalcogramma) fishery
Authors: A’mar Z. Teresa , Punt André E. , Dorn Martin W.
Published: December 2009

Climate variability affects marine ecosystems. The mechanisms relating low-frequency environmental fluctuations (regime shifts) and their impacts on marine populations are not well established for most species, but there is an expectation that the accuracy of scientific advice provided to fisheries management would be improved if management strategies incorporated the effects of regime shifts on stocks. Management strategy evaluation is used to examine the impact of regime shifts in average recruitment on the performance of management strategies for the fishery for walleye pollock, Theragra chalcogramma , in the Gulf of Alaska. The current and four alternative management strategies are evaluated. The alternatives include management strategies with different definitions of the average recruitment used when calculating management reference points, e.g., a 25-year sliding-window method and a “dynamic B0” method. The current management strategy, which ignores the possibility of future regime shifts, kept the spawning biomass higher relative to the target level than the other management strategies and had the lowest risk of fishing mortality exceeding the overfishing limit. The sliding-window management strategy achieved the highest catches and the lowest interannual variation in catch, although at the cost of a higher risk of the fishing mortality exceeding the overfishing limit.
Quantification of species selectivity by using separating devices at different locations in two whitefish demersal trawls
Authors: Holst René , Ferro Richard S.T. , Krag Ludvig Ahm , Kynoch Robert J. , Madsen Niels
Published: December 2009

This paper presents a quantitative approach to the study of fish behaviour in trawls with the aim of maintaining the catching efficiency of target species and reducing discards of unwanted bycatch. Differences in vertical distributions of species during passage through a trawl are used to sort the catch into separate compartments prior to size selection. It is demonstrated that behavioural differences may be utilized in separating species prior to size selection. Comparisons indicate that these patterns are consistent over replicate trials. Unlike cod (Gadus morhua), haddock (Melanogrammus aeglefinus), saithe (Pollachius virens), and whiting (Merlangius merlangus) do not change their vertical preference longitudinally in the trawl.
Spatiotemporal dynamics of the Atlantic salmon (Salmo salar) Greenland fishery inferred from mixed-stock analysis
Authors: Gauthier-Ouellet Marika , Dionne Mélanie , Caron François , King Tim L. , Bernatchez Louis
Published: December 2009

Mixed-stock fisheries refer to the exploitation of admixed fish stocks coming from different origins. We identified the North American origin of 2835 Atlantic salmon ( Salmo salar ) in the Greenland mixed-stock fishery during 11 years (1995–2006) at three localities using 13 microsatellites. The study included 52 baseline populations representing nine genetically distinct regional groups. The contribution of each group ranged from <1% (Maine) to 40% (Southern Québec). Decreasing temporal contributions were observed for Southern Québec (–22.0%) and New Brunswick (–17.4%), whereas an increasing contribution for Labrador (+14.9%) was observed during the time course of the study. The estimated regional contribution to the Greenland fishery was significantly correlated to the number of multi-sea-winter salmon regionally produced in 2002 (r = 0.79) and 2004 (r = 0.92). No difference in contribution was found between the three Greenland sampling localities. Ungava and Southern Québec regions showed the highest mortality estimates caused by the fishery, ranging from 12.10% to 18.08%, for both years tested. No regional group was overrepresented in landings compared with their respective productivity. Yet, management precautions should still be taken as the fishery strongly selects large females, which could have evolutionary impacts on populations over the long term.
Fecundity, atresia, and spawning strategies of Atlantic herring (Clupea harengus)
Authors: Damme Cindy J.G. van , Dickey-Collas Mark , Rijnsdorp Adriaan D. , Kjesbu Olav S.
Published: December 2009

Atlantic herring ( Clupea harengus ) have contrasting spawning strategies, with apparently genetically similar fish “choosing” different spawning seasons, different egg sizes, and different spawning areas. In the North Sea, both autumn- and winter-spawning herring share the same summer feeding area but have different spawning areas. Females of both spawning types start their oocyte development in April–May. Oocyte development is influenced by the body energy content; during the maturation cycle, fecundity is down-regulated through atresia in relation to the actual body condition. Hence, fecundity estimates must account for the relative time of sampling. The down-regulation over the whole maturation period is approximately 20% in autumn- and 50% in winter-spawning herring. The development of the oocytes is the same for both spawning strategies until autumn when autumn spawners spawn a larger number of small eggs. In winter spawners, oocyte development and down-regulation of fecundity continues, resulting in larger eggs and lower number spawned. In theory, autumn and winter spawners could therefore switch spawning strategies, indicating a high level of reproductive plasticity.
Temperature effect on dielectric behavior of an industrial porcelain-type ceramic
Authors: Hachicha O. , Ghorbel N. , Kallel A. , Fakhfakh Z.
Published: December 2009

For a better understanding of the physical mechanisms involved in insulators submitted to electron irradiation inside a scanning electron microscope, it is important to investigate charge trapping and detrapping. The commonly used technique to deduce the trapping ability and the motion process of electric charges is based on two complementary experimental methods: the scanning electron microscope mirror effect (SEMME) and the induced current measurement (ICM). In this paper, our study is devoted to the influence of temperature on the behavior of porcelain materials during electron injection time. To evaluate the geometry of the trapped charge distribution, a detailed analysis using the mirror image formation and its evolution is developed.
Analytical evidence of commuting resonance energy in correlated disorder trimer GaAs-AlxGa1–xAs superlattices
Authors: Djelti R. , Bentata S. , Aziz Z. , Besbes A.
Published: December 2009

Using the exact Airy function formalism and the transfer-matrix technique, we have numerically investigated the effect of structural and topological correlated disorder, introduced by triplet, on the miniband structure of the GaAs/AlxGa1–xAs superlattices. These systems exhibit a miniband of extended states, around a critical energy, lying to the typical structure of the trimer cell. The states close to this resonant energy consist of weakly localized states, while in band tails i.e., for negligible transmission, the states are strongly localized. This is evidence of the suppression of localization in the RTB superlattices. The extended states due to the basic cell (triple barrier) remain for correlated structural and topological disorder. However, the commuting extended state exists only in the correlated structural disorder, where the periodicity of the system is preserved. Commuting resonance energy is theoretically demonstrated in this paper, and the obtained values are in good agreement with the existing numerical results.
Effects of level density in the cross sections of (α, xn), (α, pxn), (α, 2pxn) and (α, αxn) reactions in 197Au, 181Ta, natIn and 93Nb and pre-equilibrium analysis
Authors: Singh N. L. , Mukherjee S.
Published: December 2009

Excitation functions are measured for α-particle-induced reactions on 197Au, 181Ta, natIn, and 93Nb in the energy region 18 to 60 MeV using the activation method and γ-ray spectrometry. The experimental results are compared with semiclassical model codes, STAPRE, ALICE-91, and COMPLET. These models take into account compound nuclei as well as pre-equilibrium emissions. The angular momentum removal effects have also been included in the COMPLET code. The Monte Carlo simulation code PACE4 is also employed for the calculations of equilibrium cross sections. In the case of neutron emission channels, both the model codes give fairly good agreement. The COMPLET code on the other hand, explains the α-particle emission channels in a more convincing manner.
Fluctuation on a Schwarzschild black hole
Authors: Liu Xianming , Liu Wenbiao
Published: December 2009

When a relativistic perturbation is given to the horizon of a Schwarzschild black hole, a new supersurface near the horizon will be obtained. Using the gravitational anomaly method proposed by Robinson and Wilczek, Hawking radiation from this new supersurface is calculated. It is found that the first law of thermodynamics can also be constructed successfully on this supersurface. The expressions of the characteristic position and temperature are very similar to the previous results for the event horizon of a Vaidya black hole. Comparing with the Vaidya black hole, we conclude that Hawking radiation and the thermodynamics of a Vaidya black hole should be indeed constructed at the apparent horizon instead of the event horizon.
Cointegrating relationship and the degree of market integration among the North American softwood lumber product markets
Authors: Shahi Chander K. , Kant Shashi
Published: December 2009

Studies in spatial market integration of the North American softwood lumber products have mostly focused on the question of whether prices in distinct market locations are cointegrated or not. However, the informational deficiencies in market integration studies were fulfilled in this analysis by examining a continuum of the degree of market integration rather than using the dichotomous approach whereby markets are deemed either integrated or not. Firstly, the methodology of permanent–transitory decomposition in a multivariate vector error correction model was used to estimate the cointegrating relationship of the North American markets for three categories of softwood lumber products: Spruce–Pine–Fir (SPF), Douglas fir (DF), and Hemlock fir (HF). Secondly, a consistent ranking of the degree of market integration was constructed by estimating the reaction time for prices to return back to the steady-state equilibrium, using generalized impulse response functions and persistence profiles. Our results indicate that the long-run price equilibrium relationship for all SPF and HF products is driven by both the production (in Canada) and consumption (in USA) sides of the markets, whereas that for DF products is driven by the consumption (USA) side only. Generally, the degree of market integration for HF products is lower than that for SPF products and higher than that for DF products.
Effects of gap size and surrounding trees on light patterns and aspen branch growth in the western boreal forest
Authors: Ye Fang , Comeau Philip G.
Published: December 2009

Vertical and horizontal patterns of light within gaps and expansion of trees into gaps were examined in young stands dominated by trembling aspen ( Populus tremuloides Michx.) in northeastern British Columbia and northwestern Alberta. Lateral growth of branches of aspen edge trees averaged 15.2 cm/year and was similar to crown expansion rates reported for edge trees in eastern North America. Branches growing into gaps were significantly longer than those growing away from gaps and are likely to lead to gap shrinkage and reductions in light within gaps. However, height growth of edge trees was not significantly different from that of trees within the surrounding stands. Models describing relationships between diffuse transmittance and locations within gaps and surrounding stand height were developed in this paper. Sky view angle (SVA) was found to be effective for predicting transmittance to different locations within gaps. When SVA values exceed 1.2 (at the B.C. sites), white spruce ( Picea glauca (Moench) Voss) will receive <40% of full sunlight, which is less than optimal for spruce height growth.
Early establishment of conifer recruits in the northern Rocky Mountains as a function of postfire duff depth
Authors: Hesketh M. , Greene D. F. , Pounden E.
Published: December 2009

Well-combusted duff (<3 cm depth) is generally considered the best seedbed for small-seeded species on upland sites, but we ask here, What is the optimal, postfire residual duff thickness? We hypothesize that a duff thickness equal to (but not greater than) the length of the germinant will offer the best conditions, because at this thickness, the duff layer will not prohibit radicle penetration into the mineral soil, and yet it will serve as a water-conserving mulch. Data from a recent fire in the Rocky mountains of British Columbia were used to show that for three species of Pinus and Picea, (1) duff depths <3 cm were far more clement substrates than thicker duff, and (2) there was a peak in relative survivorship at about 1–2 cm, somewhat shallower than the typical hypocotyl length for these species. Additional data sets from studies previously conducted at boreal and northern cordilleran sites in Alberta, Saskatchewan, Yukon, and Quebec (a combined 21 fires) bolstered these results.
Recent woody invasion of wetlands on the Kenai Peninsula Lowlands, south-central Alaska: a major regime shift after 18 000 years of wet Sphagnum–sedge peat recruitment
Authors: Berg Edward E. , Hillman Kacy McDonnell , Dial Roman , DeRuwe Allana
Published: December 2009

We document accelerating invasion of woody vegetation into wetlands on the western Kenai Peninsula lowlands. Historical aerial photography for 11 wetland sites showed that herbaceous area shrank 6.2%/decade from 1951 to 1968, and 11.1%/decade from 1968 to 1996. Corresponding rates for converting herbaceous area to shrubland were 11.5% and 13.7%/decade, respectively, and, for converting nonforest to forest, were 7.8% and 8.3%/decade, respectively. Black spruce ( Picea mariana (Mill.) BSP) forests on three wetland perimeters established since the Little Ice Age concluded in the 1850s. Dwarf birch shrubs at three wetland sites showed median apparent tree-ring age of 13 years, indicating recent shrub colonization at these sites. Peat cores at 24 wetland sites (basal peat ages 1840 – 18 740 calibrated years before present) indicated that these peatlands originated as wet Sphagnum –sedge fens with very little woody vegetation. Local meteorological records show a 55% decline in available water since 1968, of which one-third is due to higher summer temperatures and increased evapotranspiration and two-thirds is due to lower annual precipitation. These results suggest that wet Sphagnum–sedge fens initiating since the end of the Wisconsin glaciation began to dry in the 1850s and that this drying has greatly accelerated since the 1970s.
Analysis of fine rooting below skid trails using linear and generalized additive models
Authors: Schäffer Jürgen , von Wilpert Klaus , Kublin Edgar
Published: December 2009

Soil compaction caused by forest machinery changes the basic conditions for root propagation below skid trails. In consequence, lower fine-root densities have to be expected under wheel tracks compared with other skid trail strata that experience no direct traffic. Explorative data analysis of fine-root densities below a skid trail revealed that the fundamental assumptions for linear modelling were violated. Using a generalized linear model following a Poisson distribution with a log link function for the predictor variables together with an exponential covariance function to cope with spatial autocorrelation, the formal model criteria were met. In contrast to the linear models, generalized additive models provide flexible surface estimators that enable us to model continuous response surfaces. In addition, generalized additive models allow for the calculation of confidence intervals for the estimated density surface and for the use of inferential statistics, such as comparisons between depth gradients of fine rooting at distinct transect locations or depth layers. These model characteristics improve the possibility to recognize differences and to evaluate fine-root disturbances below skid trails without integrating uncertain strata information. They also enhance the options for determining the duration of time that is necessary to restore the rooting capacity on formerly compacted soils.
Radial growth response of white oak to climate in eastern North America
Authors: LeBlanc David C. , Terrell Mark A.
Published: December 2009

Predicting forest responses to climate change requires an understanding of the cause–effect relationships linking climate to tree growth. Dendroecological analyses across sites that span climate gradients provide one means of characterizing such relationships. Dendroecological analyses for white oak ( Quercus alba L.) at 149 sites spanning the species range in eastern North America identified spatially replicated growth–climate associations. Early growing season site water balance variables for the year of annual ring formation had the strongest, most spatially replicated associations with growth. There was little evidence of phenological variation of these associations related to the latitudinal temperature gradient. Most spatial variation in growth–climate associations was along an east-to-west precipitation gradient. Radial growth was most strongly correlated with site water balance at sites in the northwest quadrant of the range, characterized by continental climate and high interannual variability in precipitation. There was little evidence that dormant season temperature affects white oak growth, even at the northern range limit. Correlations with dormant season precipitation were common in the northwest part of the range, where winter soil water recharge may be more variable. Spatial replication was a useful criterion for distinguishing growth–climate correlations that reflect cause–effect relationships.