bluuebunny/crossref_metadata_2025 huggingface dataset:
A note on determination of the diffuse-field sensitivity of microphones using the reciprocity technique
Authors: Barrera-Figueroa Salvador , Rasmussen Knud , Jacobsen Finn
Published: September 2008

The diffuse-field response of a microphone is usually obtained by adding a random-incidence correction to the pressure response of the microphone. However, the random-incidence correction is determined from a relative measurement, and its accuracy depends not only on the relative response at all angles of incidence but also on the accuracy of the frequency response at normal incidence. By contrast, this paper is concerned with determining the absolute diffuse-field response of a microphone using the reciprocity technique. To examine this possibility, a reciprocity calibration setup is used for measuring the electrical transfer impedance between a pair of microphones placed in a miniature (2m3) reverberation room. The transfer function between the microphones is measured using fast Fourier transform analysis and pseudorandom noise. The calculation of the diffuse-field sensitivity involves (a) separation of the reverberant response from the total response, (b) determination of the reverberation time, and (c) averaging over space and frequency. The resulting diffuse-field correction is compared with an estimate of the random-incidence correction determined in an anechoic room and with a numerical prediction.
Sound absorption by clamped poroelastic plates
Authors: Aygun H. , Attenborough K.
Published: September 2008

Measurements and predictions have been made of the absorption coefficient and the surface acoustic impedance of poroelastic plates clamped in a large impedance tube and separated from the rigid termination by an air gap. The measured and predicted absorption coefficient and surface impedance spectra exhibit low frequency peaks. The peak frequencies observed in the absorption coefficient are close to those predicted and measured in the deflection spectra of the clamped poroelastic plates. The influences of the rigidity of the clamping conditions and the width of the air gap have been investigated. Both influences are found to be important. Increasing the rigidity of clamping reduces the low frequency absorption peaks compared with those measured for simply supported plates or plates in an intermediate clamping condition. Results for a closed cell foam plate and for two open cell foam plates made from recycled materials are presented. For identical clamping conditions and width of air gap, the results for the different materials differ as a consequence mainly of their different elasticity, thickness, and cell structure.
A single measurement approach for the determination of the normal incidence transmission loss
Authors: Bonfiglio Paolo , Pompoli Francesco
Published: September 2008

Several techniques for the determination of the normal incidence complex transmission coefficient and transmission loss have been proposed in literature. It has been shown that two different measurements have to be carried out for a correct evaluation of the above-mentioned quantities. However, single measurement approaches can be used at the condition that energy contributions are correctly included in the implemented formulation. This paper presents a single measurement approach based on a transfer matrix formulation, taking into account reflection contribution from the end termination and phase shift introduced by the material. The transmission performances of different kinds of layered porous materials are investigated by means of a four microphone technique in a plane wave tube. By using the decomposition technique, incident, reflected, and transmitted contributions are separated and transmission coefficient is easily calculated. Results are discussed and compared with similar techniques and with the two-load method.
Spatial release from masking with noise-vocoded speech
Authors: Freyman Richard L. , Balakrishnan Uma , Helfer Karen S.
Published: September 2008

This study investigated how confusability between target and masking utterances affects the masking release achieved through spatial separation. Important distinguishing characteristics between competing voices were removed by processing speech with six-channel envelope vocoding, which simulates some aspects of listening with a cochlear implant. In the first experiment, vocoded target nonsense sentences were presented against two-talker vocoded maskers in conditions that provide different spatial impressions but not reliable cues that lead to traditional release from masking. Surprisingly, no benefit of spatial separation was found. The absence of spatial release was hypothesized to be the result of the highly positive target-to-masker ratios necessary to understand vocoded speech, which may have been sufficient to reduce confusability. In experiment 2, words excised from the vocoded nonsense sentences were presented against the same vocoded two-talker masker in a four-alternative forced-choice detection paradigm where threshold performance was achieved at negative target-to-masker ratios. Here, the spatial release from masking was more than 20dB. The results suggest the importance of signal-to-noise ratio in the observation of “informational” masking and indicate that careful attention should be paid to this type of masking as implant processing improves and listeners begin to achieve success in poorer listening environments.
Effects of semantic predictability and regional dialect on vowel space reduction
Authors: Clopper Cynthia G. , Pierrehumbert Janet B.
Published: September 2008

This study explored the interaction between semantic predictability and regional dialect variation in an analysis of speech produced by college-aged female talkers from the Northern, Midland, and Southern dialects of American English. Previous research on the effects of semantic predictability has shown that vowels in high semantic predictability contexts are temporally and spectrally reduced compared to vowels in low semantic predictability contexts. In the current study, an analysis of vowel duration confirmed temporal reduction in the high predictability condition. An analysis of vowel formant structure and vowel space dispersion revealed overall spectral reduction for the Southern talkers. For the Northern talkers, more extreme Northern Cities shifting occurred in the high predictability condition than in the low predictability condition. No effects of semantic predictability were observed for the Midland talkers. These findings suggest an interaction between semantic and indexical factors in vowel reduction processes.
Modeling the temporal dynamics of distinctive feature landmark detectors for speech recognition
Authors: Jansen Aren , Niyogi Partha
Published: September 2008

This paper elaborates on a computational model for speech recognition that is inspired by several interrelated strands of research in phonology, acoustic phonetics, speech perception, and neuroscience. The goals are twofold: (i) to explore frameworks for recognition that may provide a viable alternative to the current hidden Markov model (HMM) based speech recognition systems and (ii) to provide a computational platform that will facilitate engaging, quantifying, and testing various theories in the scientific traditions in phonetics, psychology, and neuroscience. This motivation leads to an approach that constructs a hierarchically structured point process representation based on distinctive feature landmark detectors and probabilistically integrates the firing patterns of these detectors to decode a phonological sequence. The accuracy of a broad class recognizer based on this framework is competitive with equivalent HMM-based systems. Various avenues for future development of the presented methodology are outlined.
Structural acoustics of good and bad violins
Authors: Bissinger George
Published: September 2008

Modal-acoustic radiation measurements on 17 “bad-to-excellent” quality-rated violins—including three-dimensional modal analyses of Titian and Willemotte Stradivari and Plowden Guarneri del Gesu violins to investigate extensional as well as flexural motions—were examined for quality-related trends, generally by contrasting the properties of “excellent” and “bad” violins. All violins tested showed the same five “signature” modes below 600Hz, with no obvious quality trends for mode frequencies or total damping. Bad–excellent comparisons of band-/modal-averaged damping (total, radiation and internal), mobility, radiativity, directivity, fraction-of-vibrational-energy radiated, effective critical frequency, and radiativity profiles up to 4kHz generally showed no significant difference; the only “robust” quality differentiator was the ∼280Hz, Helmholtz-type A0 cavity mode radiativity where excellent violins were significantly higher. Radiation and total damping of two old Italian violins appeared slightly higher than those for bad violins below 2kHz, partly due to lower effective critical frequency and partly because of slightly lower mass. Stradivari violins showed the highest and lowest directivity of all instruments tested. The Titian and Plowden top plate flexural/extensional mobility ratios appeared correlated with their directivity. Extensional motion in the “bridge island” between f holes peaked near 2.4kHz, coinciding with the BH peak and a bridge/bridge-island impedance ratio minimum.
Perceptual context effects of speech and nonspeech sounds: The role of auditory categories
Authors: Aravamudhan Radhika , Lotto Andrew J. , Hawks John W.
Published: September 2008

Williams [(1986). “Role of dynamic information in the perception of coarticulated vowels,” Ph.D. thesis, University of Connecticut, Standford, CT] demonstrated that nonspeech contexts had no influence on pitch judgments of nonspeech targets, whereas context effects were obtained when instructed to perceive the sounds as speech. On the other hand, Holt et al. [(2000). “Neighboring spectral content influences vowel identification,” J. Acoust. Soc. Am. 108, 710–722] showed that nonspeech contexts were sufficient to elicit context effects in speech targets. The current study was to test a hypothesis that could explain the varying effectiveness of nonspeech contexts: Context effects are obtained only when there are well-established perceptual categories for the target stimuli. Experiment 1 examined context effects in speech and nonspeech signals using four series of stimuli: steady-state vowels that perceptually spanned from /ʊ/-/ɪ/ in isolation and in the context of /w/ (with no steady-state portion) and two nonspeech sine-wave series that mimicked the acoustics of the speech series. In agreement with previous work context effects were obtained for speech contexts and targets but not for nonspeech analogs. Experiment 2 tested predictions of the hypothesis by testing for nonspeech context effects after the listeners had been trained to categorize the sounds. Following training, context-dependent categorization was obtained for nonspeech stimuli in the training group. These results are presented within a general perceptual-cognitive framework for speech perception research.
Linguistic experience and audio-visual perception of non-native fricatives
Authors: Wang Yue , Behne Dawn M. , Jiang Haisheng
Published: September 2008

This study examined the effects of linguistic experience on audio-visual (AV) perception of non-native (L2) speech. Canadian English natives and Mandarin Chinese natives differing in degree of English exposure [long and short length of residence (LOR) in Canada] were presented with English fricatives of three visually distinct places of articulation: interdentals nonexistent in Mandarin and labiodentals and alveolars common in both languages. Stimuli were presented in quiet and in a café-noise background in four ways: audio only (A), visual only (V), congruent AV (AVc), and incongruent AV (AVi). Identification results showed that overall performance was better in the AVc than in the A or V condition and better in quiet than in café noise. While the Mandarin long LOR group approximated the native English patterns, the short LOR group showed poorer interdental identification, more reliance on visual information, and greater AV-fusion with the AVi materials, indicating the failure of L2 visual speech category formation with the short LOR non-natives and the positive effects of linguistic experience with the long LOR non-natives. These results point to an integrated network in AV speech processing as a function of linguistic background and provide evidence to extend auditory-based L2 speech learning theories to the visual domain.
Reconstruction of material properties profiles in one-dimensional macroscopically inhomogeneous rigid frame porous media in the frequency domain
Authors: De Ryck L. , Lauriks W. , Leclaire P. , Groby J. P. , Wirgin A. , Depollier C.
Published: September 2008

The present paper deals with the inverse scattering problem involving macroscopically inhomogeneous rigid frame porous media. It consists of the recovery, from acoustic measurements, of the profiles of spatially varying material parameters by means of an optimization approach. The resolution is based on the modeling of acoustic wave propagation in macroscopically inhomogeneous rigid frame porous materials, which was recently derived from the generalized Biot’s theory. In practice, the inverse problem is solved by minimizing an objective function defined in the least-square sense by the comparison of the calculated reflection (and transmission) coefficient(s) with the measured or synthetic one(s), affected or not by additive Gaussian noise. From an initial guess, the profiles of the x-dependent material parameters are reconstructed iteratively with the help of a standard conjugate gradient method. The convergence rate of the latter and the accuracy of the reconstructions are improved by the availability of an analytical gradient.
Transmission loss measurements and geoacoustic sensitivity modeling at 1.2kHz
Authors: Pecknold Sean P. , Masui Kiyoshi W. , Hines Paul C.
Published: September 2008

The Shallow Water Experiment 2006 was conducted off the coast of New Jersey in the summer of 2006. Defence Research and Development Canada—Atlantic performed a series of experiments designed to validate the use of rapid environmental assessment tools and methods to improve active sonar performance predictions. The sensitivity of acoustic propagation to a varying or uncertain environment is determined by examining the relative change of acoustic pressure caused by environmental variability, using the method described recently [Dosso et al., J. Acoust. Soc. Am. 121, 42 (2007)]. The variability of the modeled environmental parameters is based on measured and estimated oceanographic and geoacoustic properties. The resulting sensitivity is compared to measured transmission loss data at 1.2kHz.
Educational ultrasound nondestructive testing laboratory
Authors: Genis Vladimir , Zagorski Michael
Published: September 2008

The ultrasound nondestructive evaluation (NDE) of materials course was developed for applied engineering technology students at Drexel University’s Goodwin College of Professional Studies. This three-credit, hands-on laboratory course consists of two parts: the first part with an emphasis on the foundations of NDE, and the second part during which ultrasound NDE techniques are utilized in the evaluation of parts and materials. NDE applications are presented and applied through real-life problems, including calibration and use of the latest ultrasonic testing instrumentation. The students learn engineering and physical principles of measurements of sound velocity in different materials, attenuation coefficients, material thickness, and location and dimensions of discontinuities in various materials, such as holes, cracks, and flaws. The work in the laboratory enhances the fundamentals taught during classroom sessions. This course will ultimately result in improvements in the educational process [“The greater expectations,” national panel report, http://www.greaterexpectations.org (last viewed February, 2008); R. M. Felder and R. Brent “The intellectual development of Science and Engineering Students. Part 2: Teaching to promote growth,” J. Eng. Educ. 93, 279–291 (2004)] since industry is becoming increasingly reliant on the effective application of NDE technology and the demand on NDE specialists is increasing. NDE curriculum was designed to fulfill levels I and II NDE in theory and training requirements, according to American Society for Nondestructive Testing, OH, Recommended Practice No. SNT-TC-1A (2006).
Temporal coherence of mode arrivals
Authors: DeFerrari Harry A. , Lynch James F. , Newhall Arthur
Published: September 2008

Temporal coherencies are compared for individual pulse arrivals of 100 and 800Hz centered broadband signals propagating through identical shallow channels during periods of low and high internal wave energy. All 100Hz modes are clean, distinct in time, and remarkably coherent (tcoh>1h). A near continuum of modes is observed for the 800Hz signal with much shorter coherence times. Higher order modes are less coherent. Internal wave scattering appears to dominate the 100Hz signals, whereas bottom scattering also randomizes the 800Hz signal. Observations are consistent with similar measurements for this and other sites for intermediate frequencies.
Intravitreal bevacizumab (Avastin) for myopic choroidal neovascularisation: 1-year results of a prospective pilot study
Authors: Chan W-M , Lai T Y Y , Liu D T L , Lam D S C
Published: September 2008

Aim:

The aim of the study was to examine the 1-year results of intravitreal bevacizumab for myopic choroidal neovascularisation (CNV).

Methods:

Twenty-nine eyes of 29 patients with myopic CNV were prospectively recruited to receive three initial monthly intravitreal bevacizumab injections. Three additional monthly injections were performed in eyes with persistent or recurrent CNV after 3 months.

Results:

The mean spherical equivalent refractive error was −10.0 D. Sixteen eyes had previous photodynamic therapy (PDT) and 13 eyes had no prior PDT. All patients completed follow-up at 1 year. Following the initial three bevacizumab injections, 27 (93.1%) eyes had angiographic closure and two (6.9%) required further treatment. Two additional patients required re-treatment for CNV recurrence between 6 and 9 months. The mean baseline logarithm of the minimum angle of resolution (logMAR best-corrected visual acuity) was 0.62 (20/83), which improved to 0.38 (20/48) at 12 months (p<0.001). The mean visual improvement was 2.4 lines and 21 (72.4%) eyes had improvement of ⩾2 lines. Optical coherence tomography showed significant reduction in central foveal thickness following treatment. Eyes without previous PDT were more likely to gain ⩾2 lines after treatment than eyes that had previous PDT (p = 0.010).

Conclusions:

The 1-year outcomes confirmed the results of previous short-term studies that intravitreal bevacizumab is effective for myopic CNV, with a high proportion of patients sustaining visual gain after treatment.
Running in new and worn shoes: a comparison of three types of cushioning footwear
Authors: Kong P W , Candelaria N G , Smith D R
Published: September 2008

Objectives:

In this study, the effect of shoe degradation on running biomechanics by comparing the kinetics and kinematics of running in new and worn shoes was investigated. Three types of footwear using different cushioning technologies were compared.

Design:

Longitudinal study.

Setting:

Pre- and post-tests on overground running at 4.5 m s−1on a 20-m laboratory runway; performance measured using a force platform and a motion capture system.

Participants:

24 runners (14 men and 10 women)

Interventions:

200 miles of road running in the same pair of shoes. Within-group factor: shoe condition (new/worn); between-group factor: footwear type (air/gel/spring).

Main outcome measurements:

Stance time was calculated from force data. External loads were measured by maximum vertical force and loading rate. Kinematic changes were indicated by sagittal plane angles of the torso, hip, knee and ankle at critical events during the stance phase.

Results:

Stance time increased (p = 0.035) in worn shoes. The torso displayed less maximum forward lean (p<0.001) and less forward lean at toe-off (p<0.001), while the ankle displayed reduced maximum dorsiflexion (p = 0.013) and increased plantar flexion at toe-off (p<0.001) in worn shoes. No changes in the hip and knee angles. No between-group difference among the three footwear groups or condition by type interaction was found in any measured variables.

Conclusions:

As shoe cushioning capability decreases, runners modify their patterns to maintain constant external loads. The adaptation strategies to shoe degradation were unaffected by different cushioning technologies, suggesting runners should choose shoes for reasons other than cushioning technology.
Ultrasonographic evaluation of splenic enlargement in athletes with acute infectious mononucleosis
Authors: Hosey R G , Kriss V , Uhl T L , DiFiori J , Hecht S , Wen D Y
Published: September 2008

Objective:

To quantitatively assess the degree and rate of splenic enlargement and the time required for regression of splenic enlargement in collegiate athletes diagnosed with acute infectious mononucleosis (IM).

Design:

Prospective cohort study.

Setting:

Academic Medical Center(s) outpatient sports medicine clinic.

Study participants:

Volunteer Division I University athletes.

Interventions:

A limited abdominal ultrasound was performed on each participant by a licensed and experienced ultrasonographer. Splenic measurements were taken to assess maximum splenic length. Athletes who were subsequently diagnosed with infectious mononucleosis (clinical illness and a positive monospot) underwent serial splenic ultrasounds and physical exams (weekly) until resolution of clinical symptoms and splenic enlargement (as determined by ultrasound measurements).

Main outcome measures:

Per cent enlargement of spleen size (length) from baseline. Time (in days) from onset of clinical illness to maximum splenic length. Time (in days) required for resolution of splenic enlargement.

Results:

20 subjects were diagnosed with acute IM during a 5 year time period. Maximum splenic length increased a mean of 33.6% (SD 19.9%) from baseline values. Peak splenic enlargement was reached a mean of 12.3 (SD 5.1) days from onset of clinical illness. A linear model demonstrated that spleen size decreases approximately 1% per day after reaching peak splenic enlargement.

Conclusions:

The majority of athletes with IM experience a moderate degree of splenomegaly. Peak splenic enlargement occurs within 2 weeks from the time of symptom onset in most cases, but may extend to 3.5 weeks. The rate of splenic enlargement appears to be predictable for an individual who develops IM. Ultrasonographic data further show that splenomegaly associated with acute IM infection resolves within 4–6 weeks of symptom onset in the majority of cases.
Species traits influence the genetic consequences of river fragmentation on two co-occurring redhorse (Moxostoma) species
Authors: Reid Scott M. , Wilson Chris C. , Carl Leon M. , Zorn Troy G.
Published: September 2008

We used microsatellite DNA markers to test whether fragmentation of the Trent River (Ontario, Canada) has reduced genetic diversity and increased genetic differentiation among populations of river redhorse ( Moxostoma carinatum ) and shorthead redhorse (Moxostoma macrolepidotum). Allelic richness of both species was significantly greater along the free-flowing Muskegon River (Michigan, USA) than along the fragmented Trent River. Contrary to expectations, there was no evidence of a fragment length effect on genetic diversity, recent population bottlenecks, or increased relatedness among individuals in fragmented populations. High levels of linkage disequilibrium indicate extinction–recolonization population dynamics along the Trent River. For both species, pairwise FSTtests identified weak but statistically significant population differentiation. In the Trent River, differentiation was significantly greater for river redhorse than for shorthead redhorse and, for both species, greater than in the Muskegon River. Moderate fragmentation effects likely reflect the permeability of the dam-lock system to redhorse movement. Differences between species indicate that as a result of smaller effective population sizes, habitat specialists and species at the periphery of their geographic range are more sensitive to river fragmentation.
Dispersal limitation and climate-related environmental gradients structure microcrustacean composition in freshwater lakes, Ellesmere Island, Canada
Authors: Strecker Angela L. , Milne Rebecca , Arnott Shelley E.
Published: September 2008

Dramatic environmental change is expected in the Arctic, yet little is known about the occurrence and community composition of microcrustaceans in Arctic lakes and how this will be influenced by future environmental change. We sampled and calculated relative abundances of microcrustacean species in 54 lakes on Ellesmere Island, Canada. New species records on Ellesmere Island included Daphnia umbra , Tachidius discipes , and Artemeopsis stefanssoni . Daphnia middendorffiana/tenebrosa was the most common taxon and often dominated microcrustacean assemblages, likely a result of its pigmentation, which offers resistance to ultraviolet radiation. Species richness was positively associated with nutrients, dissolved organic carbon (DOC), temperature, calcium, and conductivity and negatively affected by elevation. In contrast to most findings in temperate systems, we detected a negative relationship between species richness and surface area. Community composition was influenced by DOC, nutrients, and elevation but was also related to spatial variables, suggesting that spatial gradients in environmental conditions and dispersal are important drivers of differences among sites. Arctic ecosystems are expected to change rapidly in the coming years because of climate change and ozone thinning, and we expect that associated changes in DOC, temperature, and nutrients will affect microcrustacean species richness and distribution throughout the landscape.
A diver survey design to estimate absolute density, biomass, and spatial distribution of abalone
Authors: McGarvey Richard , Mayfield Stephen , Byth Karen , Saunders Thor , Chick Rowan , Foureur Brian , Feenstra John E. , Preece Peter , Jones Alan
Published: September 2008

Abalone surveys worldwide measure relative stock abundance. However, important advantages accrue if diver surveys measure absolute numbers or biomass per square metre. Principally, absolute biomass permits quota setting from a single survey using a decision table. Although relative abundance surveys have permanently fixed sampling protocols and locations, absolute abundance survey designs can be improved with technology over time. Furthermore, surveys can be directed to areas of principal management focus, and absolute survey population numbers by length with confidence intervals provide informative model input. We propose and test a transect survey design to estimate and map absolute density and biomass of abalone or other sedentary invertebrates. Divers count and measure all abalone within 1 m of a 100 m, boat-deployed leaded rope line. Semi-systematic transect locations provide spatially representative sampling inside bounded survey regions and geostatistical data for contour maps of abalone density and mean size. The effectiveness of the design for estimating change in population size under harvesting and for locating areas of fishable density was tested by a fish-down experiment, using surveys run before and after commercial harvest. The leaded-line survey design estimates of population change and spatial distribution showed agreement with the fish-down experimental harvest.
Salmonid or nonsalmonid lakes: predicting the fate of northern boreal fish communities with hierarchical filters relating to a keystone piscivore
Authors: Spens Johan , Ball John P.
Published: September 2008

We determine if lacustrine salmonids show large-scale patterns of coexistence with the keystone predator northern pike ( Esox lucius ) and test an approach to predict fish communities using coexistence rules set in the context of three hierarchical filters that a species must pass to be present. The mutually exclusive species distribution patterns that we detected among 1029 lakes were repeatedly verified from results of whole-lake interventions with rotenone and introductions. Essentially, pike did not coexist with self-sustaining salmonid populations in lakes. High connectivity to pike (derived from maps) largely predicts the absence of lacustrine salmonids. Our analysis strongly suggests that pike prevented self-sustaining populations of brown trout ( Salmo trutta ), Arctic char ( Salvelinus alpinus ), and brook trout ( Salvelinus fontinalis ) in lakes. High connectivity to pike resulted in nonsalmonid lake fish communities, most often including both European perch ( Perca fluviatilis ) and roach ( Rutilus rutilus ). Our analysis suggests that if pike were not present in many boreal lakes where they now dwell, salmonid fish assemblages would prevail, a sharp contrast from the present pike-driven homogenized state with mainly nonsalmonid fish communities.
Habitat quality enhances spatial variation in the self-thinning patterns of stream-resident brown trout (Salmo trutta)
Authors: Lobón-Cerviá Javier
Published: September 2008

This study explored the extent to which variation in habitat factors related to growth and density influence self-thinning patterns in stream-living brown trout ( Salmo trutta ). Analysis of 110 cohorts at 12 sites of four contrasting streams revealed density–mass relationships in two phases. Density of survivors decreased little during the first half of their lifetime. A second phase commenced as individuals attained a threshold mass upon which density declined linearly with increased mass. The slopes of the second phase were greater than predicted by space and food demands. Among sites, these slopes were related to threshold densities at the beginning of the second phase. In turn, elevations, threshold densities, and slopes depicted concave trajectories against site depth, whereas threshold masses increased linearly. Apparently, cohorts remain below the carrying capacity during the first half of their lifetime and self-thin during the second half. Space-limited habitats impose site-specific carrying capacities and site-specific self-thinning coefficients, suggesting a common mechanism underlying self-thinning and an unanticipated, emerging property: two-phase patterns with far more variation in self-thinning coefficients. Variability in growth and density exhibited by brown trout and other salmonids across regions suggests that two-phase patterns may occur broadly, and self-thinning coefficients may vary widely.
Acoustically derived fine-scale behaviors of juvenile Chinook salmon (Oncorhynchus tshawytscha) associated with intertidal benthic habitats in an estuary
Authors: Semmens Brice Xavier
Published: September 2008

Given the presumed importance of benthic and epibenthic estuarine habitats in Chinook salmon ( Oncorhynchus tshawytscha ) smolt growth and survival, resource managers would be well served by an improved understanding of how smolts use such habitats. A cabled acoustic positioning system was used to precisely track (<1 m resolution) the movement of seventeen 0-aged hatchery-reared fall Chinook smolts in a large (~4000 m2) enclosure over a period of 10 days in Willapa Bay, Washington, USA. A hierarchical Bayesian state–space model of movement was subsequently developed to associate the behaviors of tagged salmon with characteristics of benthic habitat in the enclosure. Model results indicated that smolts had a strong preference for remaining in native eelgrass ( Zostera marina ). Conversely, no such preference existed for other structured benthic habitats such as oyster ( Crassostrea gigas ) beds, non-native eelgrass ( Zostera japonica ), and non-native smooth cordgrass ( Spartina alterniflora ). There was a positive relationship between individual survivorship in the enclosure and the strength of behavioral preference for native eelgrass, suggesting that predator avoidance may be the evolutionary mechanism driving behavioral responses of smolts to benthic habitats.
Dominant height growth equations including site attributes in the generalized algebraic difference approach
Authors: Bravo-Oviedo Andrés , Tomé Margarida , Bravo Felipe , Montero Gregorio , del Río Miren
Published: September 2008

We present a new dynamic dominant height growth model based on Cieszewski’s generalized algebraic difference approach (GADA) advanced dynamic site equation strengthened by the use of explicit climate and soil variables (i.e., H = f(H0,T0, T, site conditions)). The results suggest that the inclusion of climatic variables would improve the applicability of the inter-regional model in regions in which climate and soil type lead to intra-regional variability. The new model reduces the bias present in a previous dynamic model that did not include climatic attributes and improves the model efficiency across the different age classes. Climate has a multiplicative effect on dominant tree growth in the early development stages (<20 years) and an additive effect in older stands.
Do higher financial returns lead to better environmental performance in North America’s forest products sector?
Authors: Yamaguchi Jesse , van Kooten G. Cornelis
Published: September 2008

This study examines the relation between corporate environmental performance and corporate financial (economic) performance in North America’s forest products industry to determine whether there is a firm-level environmental Kuznets curve (EKC). An unbalanced panel of firm-level observations is constructed using data from PricewaterhouseCoopers, the US Environmental Protection Agency, and Environment Canada. The analysis focuses on methanol and formaldehyde emissions because these are the only pollutants for which consistent firm-level data are available in forestry. We find strong evidence of a firm-level EKC. The evidence is considerably weaker if endogeneity related to the effect of past pollution on current pollution or endogeneity resulting from a possible circular relationship between rate of return and pollution is taken into account, although the available time horizon is too short to conclude that endogeneity is a problem. Even so, there remains evidence of a negative relationship between financial performance and environmental performance for formaldehyde.
Pre- and post-European settlement fire history of red pine dominated forest ecosystems of Seney National Wildlife Refuge, Upper Michigan
Authors: Drobyshev Igor , Goebel P. Charles , Hix David M. , Corace R. Gregory , Semko-Duncan Marie E.
Published: September 2008

To understand the dynamics of fire in red pine ( Pinus resinosa Ait.) forest ecosystems that once dominated areas of the northern Lake States, we dendrochronologically reconstructed the fire regime prior to European settlement (pre-1860), after European settlement (1860–1935), and postrefuge establishment (post-1935) for different portions (wilderness and nonwilderness) and landforms (sand ridges and outwash channels) of the Seney National Wildlife Refuge (SNWR) in eastern Upper Michigan. Using data from 50 sites, we found that the cumulative number of fires showed a slow rate of accumulation from the 1700s to 1859, a steeper pattern suggesting higher fire occurrence from 1860 to 1935, and a return to fewer fires after 1935. Prior to European settlement, the fire cycle (FC) of sand ridge landforms interspersed within a poorly drained lacustrine plain in the Seney Wilderness Area was 91–144 years. This was longer than on glacial outwash channel landforms (53 years) and on sand ridge landforms interspersed within lacustrine plains located outside of the wilderness (47 years). The FC was also shorter (30 years) during this period and has subsequently increased (149–1090 years) after SNWR establishment. Differences in fire regimes among landform types were minor relative to the temporal variation in fire regimes among the three time periods.
Decomposition of stumps 10 years after partial and complete harvesting in a southern boreal forest in Finland
Authors: Shorohova Ekaterina , Kapitsa Ekaterina , Vanha-Majamaa Ilkka
Published: September 2008

We studied the decomposition of cut stumps of Norway spruce ( Picea abies (L.) Karst.), Scots pine ( Pinus sylvestris L.), and birches ( Betula pubescens Ehrh. and Betula pendula Roth.) 10 years after clear felling, low level retention felling, gap felling, and selection felling. Bulk density of wood, mass per surface area of bark, and mass of wood and bark for entire stumps were estimated. Using a single exponential model, annual decomposition rate constants (k) were calculated as 0.071, 0.052, and 0.041 ·year–1 for birch, spruce, and pine, respectively. The k values for wood decreased in the same order. For bark, the order was different: spruce bark decomposed slower than pine bark. Fragmentation accelerated mass loss. Pine and birch bark decomposed faster than pine and birch wood, whereas spruce showed the opposite tendency. The wood density and bark mass did not depend on retention levels. Diameter of stumps did not explain variation in decomposition either. The high importance of stumps for biodiversity, carbon, and nutrient cycling requires refinements to decomposition rate constants. Thus, further research based on new empirical data and meta-analysis of published data is needed to reveal factors influencing the decomposition process in situ.
Implications of selection history on genetic architecture of growth, form, and wood-quality traits in Pinus radiata
Authors: Kumar S. , Burdon R. D. , Stovold G. T. , Gea L. D.
Published: September 2008

Clonal trials of Pinus radiata D. Don (radiata pine), representing two populations (or breeds), one selected for growth and form (GF) and the other selected for high wood density as well as growth and form (HD), were replicated on two low-altitude New Zealand sites: Tarawera (pumice soil, 38°08′S) and Woodhill (coastal dune, 36°42′S). The GF material comprised 33 pair-crosses (19 parents) × 10 clones, and the HD material comprised 19 single-pair crosses (35 parents) × 10 clones, with six ramets per clone per site. Diameter (DBH), two tree-form variables, and needle retention (NRA) were assessed 8 years after planting, and wood density (DEN), acoustic velocity, and collapse were assessed 9 years after planting. The site differences were generally expressed more strongly in the GF population. Estimated genetic parameters were mostly similar for the two breeds, except that genotypic correlation between DBH and DEN was apparently zero in the HD population. Estimated broad-sense heritabilities (H2) were generally markedly higher than narrow-sense heritability estimates (h2), except with DEN. Estimated between-site type-B clonal genotypic correlations were generally high (>0.8) for wood properties. Overall, DBH showed adverse genetic correlations with wood properties. The Elite/Breed strategy appeared to be helpful in combating adverse genetic correlations.
Soil water content and emergence time control seedling establishment in three co-occurring Mediterranean oak species
Authors: Urbieta Itziar R. , Pérez-Ramos Ignacio M. , Zavala Miguel A. , Marañón Teodoro , Kobe Richard K.
Published: September 2008

Tree species can differ in their responses to resource availability during the critical phase of establishment, which could influence forest dynamics. In Mediterranean forests, most of the attention has focused on the effects of shade and summer drought on seedling survival, but little is known about the effect of autumn to spring rains on earlier stages of recruitment. A sowing experiment was set up along natural light and water gradients with three co-occurring oak species ( Quercus suber L. (cork oak), Quercus canariensis Willd. (Algerian oak), and Quercus pyrenaica Willd. (Pyrenean oak)) that show limited natural regeneration in southern Spain. Recruitment stages were monitored for 1 year. Models of seed germination, seedling emergence, and seedling survival as well as of overall recruitment patterns were developed as functions of light, soil moisture, and soil compaction. The influence of intraspecific variation in seed mass and emergence time were also tested. Excess soil water levels during the winter reduced germination and emergence and lengthened time to emergence (in waterlogged open areas), which in turn decreased seedling survival during the dry season. Seedlings from larger seeds were more likely to germinate and emerge. The results suggest that temporal and spatial variability of soil water content, mediated by emergence time and seed size, play a crucial role in the regeneration dynamics of Mediterranean oak forests.
Four centuries of soil carbon and nitrogen change after stand-replacing fire in a forest landscape in the western Cascade Range of Oregon
Authors: Giesen T. W. , Perakis S. S. , Cromack K.
Published: September 2008

Episodic stand-replacing wildfire is a significant disturbance in mesic and moist Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) forests of the Pacific Northwest. We studied 24 forest stands with known fire histories in the western Cascade Range in Oregon to evaluate long-term impacts of stand-replacing wildfire on carbon (C) and nitrogen (N) pools and dynamics within the forest floor (FF, Oe and Oa horizons) and the mineral soil (0–10 cm). Twelve of our stands burned approximately 150 years ago (“young”), and the other 12 burned approximately 550 years ago (“old”). Forest floor mean C and N pools were significantly greater in old stands than young stands (N pools: 1823 ± 132 kg·ha–1vs. 1450 ± 98 kg·ha–1; C pools: 62 980 ± 5403 kg·ha–1vs. 49 032 ± 2965 kg·ha–1, mean ± SE) as a result of significant differences in FF mass. Forest floor C and N concentrations and C/N ratios did not differ by time since fire, yet potential N mineralization rates were significantly higher in FF of old sites. Old and young mineral soils did not differ significantly in pools, concentrations, C/N ratios, or cycling rates. Our results suggest that C and N are sequestered in FF of Pacific Northwest Douglas-fir forests over long (∼400 year) intervals, but that shorter fire return intervals may prevent that accumulation.
A NEW COMPACTNESS RESULT FOR ELECTROMAGNETIC WAVES: APPLICATION TO THE TRANSMISSION PROBLEM BETWEEN DIELECTRICS AND METAMATERIALS
Authors: BONNET-BEN DHIA A.-S. , CIARLET P. , ZWÖLF C. M.
Published: September 2008

We consider the time-harmonic Maxwell equations, involving wave transmission between media with opposite sign dielectric and/or magnetic coefficients. We prove that, in the case of sign-shifting dielectric coefficients, the space of electric fields is compactly embedded in L2. We build a three-field variational formulation equivalent to Maxwell system for sign-shifting magnetic coefficients and show that, under some suitable conditions, the formulation fits into the coercive plus compact framework.
MULTIFRACTIONAL PROPERTIES OF STOCK INDICES DECOMPOSED BY FILTERING THEIR POINTWISE HÖLDER REGULARITY
Authors: BIANCHI S. , PIANESE A.
Published: September 2008

We propose a decomposition of financial time series into Gaussian subsequences characterized by a constant Hölder exponent. In (multi)fractal models this condition is equivalent to the subsequences themselves being stationarity. For the different subsequences, we study the scaling of the variance and the bias that is generated when the Hölder exponent is re-estimated using traditional estimators. The results achieved by both analyses are shown to be strongly consistent with the assumption that the price process can be modeled by the multifractional Brownian motion, a nonstationary process whose Hölder regularity changes from point to point.
BOUNDS ON OPTION PRICES IN POINT PROCESS DIFFUSION MODELS
Authors: BRETON JEAN-CHRISTOPHE , PRIVAULT NICOLAS
Published: September 2008

We obtain lower and upper bounds on option prices in one-dimensional jump-diffusion markets with point process components. Our proofs rely in general on the classical Kolmogorov equation argument and on the propagation of convexity property for Markov semigroups, but the bounds on intensities and jump sizes formulated in our hypotheses are different from the ones already found in the literature (Finance and Stochastics4(2) (2000) 209–222; 10(2) (2006) 229–249).
PRICING AND HEDGING OF PORTFOLIO CREDIT DERIVATIVES WITH INTERACTING DEFAULT INTENSITIES
Authors: FREY RÜDIGER , BACKHAUS JOCHEN
Published: September 2008

We consider reduced-form models for portfolio credit risk with interacting default intensities. In this class of models default intensities are modeled as functions of time and of the default state of the entire portfolio, so that phenomena such as default contagion or counterparty risk can be modeled explicitly. In the present paper this class of models is analyzed by Markov process techniques. We study in detail the pricing and the hedging of portfolio-related credit derivatives such as basket default swaps and collaterized debt obligations (CDOs) and discuss the calibration to market data.
Advances in Quantifying Air-Sea Gas Exchange and Environmental Forcing
Authors: Wanninkhof Rik , Asher William E. , Ho David T. , Sweeney Colm , McGillis Wade R.
Published: September 2008

The past decade has seen a substantial amount of research on air-sea gas exchange and its environmental controls. These studies have significantly advanced the understanding of processes that control gas transfer, led to higher quality field measurements, and improved estimates of the flux of climate-relevant gases between the ocean and atmosphere. This review discusses the fundamental principles of air-sea gas transfer and recent developments in gas transfer theory, parameterizations, and measurement techniques in the context of the exchange of carbon dioxide. However, much of this discussion is applicable to any sparingly soluble, non-reactive gas. We show how the use of global variables of environmental forcing that have recently become available and gas exchange relationships that incorporate the main forcing factors will lead to improved estimates of global and regional air-sea gas fluxes based on better fundamental physical, chemical, and biological foundations.
Ser9 phosphorylation of mitochondrial GSK-3β is a primary mechanism of cardiomyocyte protection by erythropoietin against oxidant-induced apoptosis
Authors: Ohori Katsuhiko , Miura Tetsuji , Tanno Masaya , Miki Takayuki , Sato Takahiro , Ishikawa Satoko , Horio Yoshiyuki , Shimamoto Kazuaki
Published: September 2008

The aim of this study was to determine the role of GSK-3β in cardiomyocyte protection afforded by erythropoietin (EPO) against oxidant stress-induced apoptosis. Treatment with EPO (10 units/ml) induced Ser473 phosphorylation of Akt and Ser9 phosphorylation of GSK-3β and significantly reduced the proportion of apoptotic H9c2 cardiomyocytes after exposure to H2O2 from 38.3 ± 2.7% to 26.0 ± 2.9%. This protection was not detected in cells transfected with constitutively active GSK-3β (S9A), which lacks Ser9 for inhibitory phosphorylation. The antiapoptotic effect of EPO was mimicked completely by GSK-3β knockdown using small interfering RNA and partly by the transfection with kinase-deficient GSK-3β (K85R). The level of colocalization of intracellular GSK-3β with mitochondria assessed by enhanced green fluorescent protein-tagged GSK-3β or immunocytochemistry was not altered by EPO treatment. However, EPO increased the level of Ser9-phospho-GSK-3β colocalized with mitochondria by 50% in a phosphatidylinositol 3-kinase-dependent manner. Mitochondrial translocation of Bcl-2-associated X protein (BAX) after exposure to H2O2 was inhibited by EPO pretreatment and by GSK-3β knockdown. These results suggest that the suppression of GSK-3β activity by Akt-mediated Ser9 phosphorylation in the mitochondria affords cardiomyocytes tolerance against oxidant-induced apoptosis, possibly by inhibiting the access of BAX to the mitochondria.