bluuebunny/crossref_metadata_2025 huggingface dataset:
Facilitating an L2 Book Club: A Conversation‐Analytic Study of Task Management
Authors: RO EUNSEOK
Published: November 2017

This study employs conversation analysis to examine a facilitator's interactional practices in the post‐expansion phase of students’ presentations in the context of a book club for second language learning. The analysis shows how the facilitator establishes intersubjectivity with regard to the ongoing task and manages students’ task performance. The empirical data suggest that the facilitator's orientation to the task was achieved in 3 important ways: through (a) task resumption (Excerpts 1 and 2), (b) task summary (Excerpts 3 and 4), and (c) task mediation (Excerpts 5–7). As the data presented in this study demonstrate, the facilitator's task orientation practices created opportunities for the students (and herself) to gain more understanding of the presenters’ task answers, which was one of the fundamental pedagogical goals of the book club activity. By providing insights into the way the facilitator managed students’ task performance in this book club context, the study expands our understanding of the intricate maneuvers involved in task interactions. I conclude by addressing the study's pedagogical implications for language teaching.
Using woody flora to define phytogeographic units: analysis of a west–east transect in central Italy
Authors: Latini Marta , Iberite Mauro , Abbate Giovanna
Published: November 2017

To improve the phytogeographic characterization of peninsular Italy, we analysed and compared the spatial distribution of woody flora at both the species and genus level along an approximate 160 km west–east transect within the central peninsula. Sampling sites were selected using a subjective stratified sampling design. A total of 1710 occurrence records, 138 species, and 74 genera from 153 floristic relevés was used. The congruence in species and genera patterns, supported by Mantel and Procrustes tests, confirmed the validity of the higher‐taxon approach to analyse woody flora patterns. Non‐metric multi‐dimensional scaling and Pearson's chi square analysis pointed out that elevation and related bioclimatic factors were the most important drivers of woody species composition. Three well‐defined woody flora types (coastal low‐elevation, inland middle‐elevation, and inland high‐elevation) were identified using partition around medoids clustering. The species‐rich inland middle‐elevation type supports the recently described Transition unit between the Mediterranean and Euro‐Siberian Regions. Contrary to previous assumptions, floristic and chorological differences between the Tyrrhenian and the Adriatic subtypes were detected only in the inland high‐elevation type and not in the coastal low‐elevation type. The adopted methodological approach, based on higher‐taxon approach and on clustering and ordination of floristic relevés, proved to be valuable to detect woody flora distribution patterns and to delineate the phytogeographic characters of a very heterogeneous and biodiverse area.
Oropharyngeal dysphagia profiles in individuals with oculopharyngeal muscular dystrophy
Authors: Tabor L. C. , Plowman E. K. , Romero‐Clark C. , Youssof S.
Published: November 2017

Background

Although dysphagia represents a hallmark manifestation of oculopharyngeal muscular dystrophy (OPMD), limited knowledge exists regarding the underlying nature of oropharyngeal swallowing impairments in this patient population. We aimed to delineate global pharyngeal dysphagia profiles in OPMD and identify the prevalence and physiologic associations of impairments in swallowing safety and efficiency.

Methods

Twenty‐two individuals with OPMD completed a videofluoroscopic swallowing evaluation. Blinded raters completed validated scales of global dysphagia (dynamic imaging grade of swallowing toxicity, DIGEST), efficiency (normalized residue ratio scale, NRRS), and safety (penetration‐aspiration scale, PAS). Degree of laryngeal vestibule closure and aspiration events were described. Descriptives and chi‐squared analyses were conducted with alpha set at P < .05.

Key Results

One hundred and thirty‐four swallowing trials were analyzed. DIGEST scores revealed that 96% (n = 21) of participants demonstrated pharyngeal dysphagia (score >1). Presence of a cricopharyngeal bar was noted in 10 individuals. The predominant swallowing categorization across patients was safe and inefficient (51%) followed by unsafe and inefficient (32%). 77.3% demonstrated vallecular residue (NRRSv>0.07) and 90.1% piriform sinus residue (NRRSp > .20). 33% (n = 54) of swallows were unsafe (PAS>3) with 45 episodes of penetration and 9 episodes of aspiration. Aspiration occurred during the swallow in 100% of identified occurrences. Incomplete epiglottic inversion was associated with airway compromise and postswallow residue (P < .05).

Conclusions & Inferences

These findings highlight the high prevalence of oropharyngeal swallowing impairments in both swallowing efficiency and safety. A high proportion of physiologic impairments in epiglottic inversion and laryngeal vestibule closure were noted that related to functional impairments in swallow safety and inefficiency.
Spatial separation without territoriality in shark communities
Authors: Papastamatiou Yannis P. , Bodey Thomas W. , Friedlander Alan M. , Lowe Christopher G. , Bradley Darcy , Weng Kevin , Priestley Victoria , Caselle Jennifer E.
Published: November 2017

Spatial separation within predator communities can arise via territoriality but also from competitive interactions among and within species. However, linking competitive interactions to predator distribution patterns is difficult and theoretical models predict different habitat selection patterns dependent on habitat quality and how competition manifests itself. While models generally consider competitors to be either equal in ability, or for one phenotype to have a fixed advantage over the other, few studies consider that an animal may only have a competitive advantage in specific habitats. We used  10 years of telemetry data, habitat surveys and behavioral experiments, to show spatial partitioning between and within two species of reef shark (grey reef Carcharhinus amblyrhinchos and blacktip reef sharks C. melanopterus) at an unfished Pacific atoll. Within a species, sharks remained within small ‘sub‐habitats’ with very few movements of individuals between sub‐habitats, which previous models have suggested could be caused by intra‐specific competition. Blacktip reef sharks were more broadly distributed across habitat types but a greater proportion used lagoon and backreef habitats, while grey reef sharks preferred forereef habitats. Grey reef sharks at a nearby atoll where blacktip reef sharks are absent, were distributed more broadly between habitat types than when both species were present. A series of individual‐based models predict that habitat separation would only arise if there are competitive interactions between species that are habitat‐specific, with grey reefs having a competitive advantage on the forereefs and blacktips in the lagoons and backreef. We provide compelling evidence that competition helps drive distribution patterns and spatial separation of a marine predator community, and highlight that competitive advantages may not be constant but rather dependent on habitats.
Benevolent Cruelty: Forced Child Removal, African Refugee Settlers, and the State Mandate of Child Protection
Authors: Ramsay Georgina
Published: November 2017

Practices of state‐mandated forced child removal in Australia have historically served to govern minority cultural groups. Despite an overarching imperative to prevent harm to children, contemporary systems of child welfare continue to impose forms of governance, particularly in regard to resettled refugees. This article focuses on the experiences of women who have been resettled in Australia as refugees from Africa, and who have, upon their resettlement, had their children forcibly removed from their care as a result of concerns over child protection. Examining how forms of governmentality are embedded within these interventions but legitimated by assumptions of benevolence, I show how the child welfare system can impose forms of pastoral power on resettled refugees, in which “care” for children is concentrated within institutions of government authority and, subsequently, oriented through state agendas. I argue that the state mandate of child protection combines governmentality and pastoral power to produce what I term benevolent cruelty, in which the imperative to protect children complicates and contradicts the refuge that is provided to resettled refugees.
Papers That Work: Migration Brokers, State/Market Boundaries, and the Place of Law
Authors: Alpes Maybritt Jill
Published: November 2017

State discourses on smuggling and trafficking are regulatory technologies that seek to institute moral hierarchies between institutions by villanizing third‐party mediators as dangerous criminals. This article instead studies high‐risk migration and illegality through the actions of migration brokers and from the perspective of aspiring migrants in a place of departure. Seeking to overcome the legal/illegal divide by focusing on interactions at socially constructed state/market boundaries, the article asks two questions: What is the role of legality for aspiring migrants? And what role do states play in the emergence of migration brokers? Based on seventeen months of ethnographic fieldwork in Anglophone Cameroon, between 2007 and 2013, and a case study of two migration brokers, the article demonstrates, first, that aspiring migrants evaluate migration brokers and travel documents in terms of their powers and efficiency, and, second, how migration brokers enact state‐like forms and activities.
Controversies, Authority, and the Limits of Participation: Chicago's 49th Ward
Authors: Baiocchi Gianpaolo , Summers Nicole
Published: November 2017

This article analyzes an innovative, and relatively successful, experience in Chicago: its participatory budgeting (PB) process. Treating it as process‐in‐the‐making, we are attentive to moments of uncertainty and controversy over the first year of its development. As a process of direct democracy, PB is profoundly ambiguous: it is, in principle, open to all, but it has no way to adjudicate between different ways of knowing and making claims by technical experts, democratically elected office holders, and newly established neighborhood leaders. Because it is a bottom‐up process that in principle does not privilege certain groups, it generates ambiguity over who gets to speak for and on behalf of the whole. In Chicago, each of these ambiguities generated controversies, which generated political talk that implied utopian alternatives that were then settled in ways that closed off these alternatives, in the end reinforcing the power of experts and revaluing the role of established community leaders against newcomers. We contend that the critical literature on participation should be more attentive to moments of conflict, ambiguity, and closure when the outlines of participatory processes are collectively produced.
Wild Eavesdropping: Observations on Surveillance, Conspiracy, and Truth in East Central Europe
Authors: Larson Jonathan L.
Published: November 2017

A debate on how to use surveillance technology to maintain public security while still respecting civil liberties has seized the Euro‐American public sphere. These deliberations are not new. Their current form has been shaped by a global “war on terrorism,” Edward Snowden's 2013 revelations on the National Security Administration's surveillance, and repeated terrorist attacks in Western Europe. The dominant frame of current discourse has been shaped along axes of public security versus civil liberties, and global terror versus democracy. Other vectors bisect this field. Webcams, security cameras, Internet search history, and records of the patterns to online social networks facilitate the increased monitoring of behavior in the developed world. While much of this surveillance—the array of means for monitoring someone else's behavior—has earned grudging acceptance as inherent to the infrastructure of a modern life, reception of its forms can vary.
Phylogenetic relationships and molecular delimitation of CulicoidesLatreille (Diptera: Ceratopogonidae) species in the Afrotropical region: interest for the subgenus Avaritia
Authors: BAKHOUM M. T. , LABUSCHAGNE K. , HUBER K. , FALL M. , MATHIEU B. , VENTER G. , GARDÈS L. , BALDET T. , BOUYER J. , FALL A. G. , GIMONNEAU G. , GARROS C.
Published: November 2017

Phylogenetic relationships of Culicoides species of the Afrotropical region are problematic as different authors disagree on the placement of species into specific subgenera or groups. In this study we sequenced two mitochondrial (COI and 16S rDNA) and two nuclear (CAD and 28S rDNA) gene fragments to reconstruct phylogenetic relationships within the Avaritia, Remmia and Synhelea subgenera and the Milnei, Neavei and Similis groups of Culicoides using both Bayesian inference and maximum‐likelihood approaches. Based on phylogenetic trees, we used the bGMYC (Bayesian General Mixed Yule Coalescent model) and the PTP (Bayesian Poisson Tree Processes) to investigate species boundaries. All species relationships within the studied subgenera and groups were well‐supported by using morphological characters and molecular analyses. The subgenus Avaritia includes (i) all of the species of the Imicola group, as well as the putative new species, C. sp. #22, and we confirmed the monophyly of this group; (ii) the Dasyops group includes C. kanagai and C. sp. #54 Meiswinkel (new species), shown to be monophyletic; (iii) the C. sp. #20 belongs to the Orientalis group; (iv) C. grahamii, C. gulbenkiani and C. kibatiensis. Our results also show that subgenus Remmia is monophyletic. Relationships of species of the Milnei group were well‐supported and demonstrate the monophyly of this group. Borkent's classification for Similis group is confirmed. In addition, C. neavei and C. ovalis (Neavei group) are placed in the subgenus Synhelea.
Control of hemorrhage through the osteotomy gap during tibial plateau leveling osteotomy: 9 cases
Authors: Matres‐Lorenzo Luis , McAlinden Aidan , Bernardé Antoine , Bernard Fabrice
Published: November 2017

Objective

To describe a new technique to control intraoperative hemorrhage during tibial plateau leveling osteotomy (TPLO) and report subsequent short‐term and long‐term complications.

Study Design

Retrospective case series.

Animals

Nine dogs with arterial hemorrhage during TPLO.

Methods

Medical records of dogs with hemorrhage controlled through the osteotomy gap of a TPLO were reviewed at 2 institutions over 8 years. Inclusion criteria included diagnosis of single cranial cruciate ligament rupture, intraoperative arterial hemorrhage during the radial osteotomy controlled with bipolar electrocautery or hemostatic clips placed along the cranial tibial artery through the osteotomy, complete medical records, radiographic follow‐up for at least 8 weeks postoperatively, and completion of long‐term follow‐up questionnaire by the owner.

Results

Dogs were 4.6 ± 1.8 years old and weighed 36.6 ± 9.7 kg. In total, 3 ± 1 hemostatic clips were placed per stifle. Intraoperative hemostasis was achieved in all cases. One of the first dogs received a blood transfusion during the procedure and had a postoperative packed cell volume of 37%. The only complication consisted of fibular fracture, which was noticed on radiographs of 1 dog 8 weeks after TPLO.

Conclusion

Arterial hemorrhage during the radial osteotomy of a TPLO can be controlled by occlusion of the compromised artery through distraction of the osteotomy gap. This technique was not associated with long‐term complications.
Spatial variation in the parasite communities and genomic structure of urban rats in New York City
Authors: Angley L. P. , Combs M. , Firth C. , Frye M. J. , Lipkin W. I. , Richardson J. L. , Munshi‐South J.
Published: November 2017

Brown rats (Rattus norvegicus) are a globally distributed pest. Urban habitats can support large infestations of rats, posing a potential risk to public health from the parasites and pathogens they carry. Despite the potential influence of rodent‐borne zoonotic diseases on human health, it is unclear how urban habitats affect the structure and transmission dynamics of ectoparasite and microbial communities (all referred to as “parasites” hereafter) among rat colonies. In this study, we use ecological data on parasites and genomic sequencing of their rat hosts to examine associations between spatial proximity, genetic relatedness and the parasite communities associated with 133 rats at five sites in sections of New York City with persistent rat infestations. We build on previous work showing that rats in New York carry a wide variety of parasites and report that these communities differ significantly among sites, even across small geographical distances. Ectoparasite community similarity was positively associated with geographical proximity; however, there was no general association between distance and microbial communities of rats. Sites with greater overall parasite diversity also had rats with greater infection levels and parasite species richness. Parasite community similarity among sites was not linked to genetic relatedness of rats, suggesting that these communities are not associated with genetic similarity among host individuals or host dispersal among sites. Discriminant analysis identified site‐specific associations of several parasite species, suggesting that the presence of some species within parasite communities may allow researchers to determine the sites of origin for newly sampled rats. The results of our study help clarify the roles that colony structure and geographical proximity play in determining the ecology ofR. norvegicusas a significant urban reservoir of zoonotic diseases. Our study also highlights the spatial variation present in urban rat parasite communities, indicating that rats across New York City are not reservoirs for a homogenous set of parasites and pathogens. As a result, the epidemiological risks may be similarly heterogeneous for people in urban habitats.
K2P TASK‐2 and KCNQ1–KCNE3 K+ channels are major players contributing to intestinal anion and fluid secretion
Authors: Julio‐Kalajzić Francisca , Villanueva Sandra , Burgos Johanna , Ojeda Margarita , Cid L. Pablo , Jentsch Thomas J. , Sepúlveda Francisco V.
Published: November 2017

Key points

K+ channels are important in intestinal epithelium as they ensure the ionic homeostasis and electrical potential of epithelial cells during anion and fluid secretion.

Intestinal epithelium cAMP‐activated anion secretion depends on the activity of the (also cAMP dependent) KCNQ1–KCNE3 K+ channel, but the secretory process survives after genetic inactivation of the K+ channel in the mouse.

Here we use double mutant mice to investigate which alternative K+ channels come into action to compensate for the absence of KCNQ1–KCNE3 K+ channels.

Our data establish that whilst Ca2+‐activated KCa3.1 channels are not involved, K2P two‐pore domain TASK‐2 K+ channels are major players providing an alternative conductance to sustain the intestinal secretory process.

Work with double mutant mice lacking both TASK‐2 and KCNQ1–KCNE3 channels nevertheless points to yet‐unidentified K+ channels that contribute to the robustness of the cAMP‐activated anion secretion process.

Anion and fluid secretion across the intestinal epithelium, a process altered in cystic fibrosis and secretory diarrhoea, is mediated by cAMP‐activated CFTR Cl− channels and requires the simultaneous activity of basolateral K+ channels to maintain cellular ionic homeostasis and membrane potential. This function is fulfilled by the cAMP‐activated K+ channel formed by the association of pore‐forming KCNQ1 with its obligatory KCNE3 β‐subunit. Studies using mice show sizeable cAMP‐activated intestinal anion secretion in the absence of either KCNQ1 or KCNE3 suggesting that an alternative K+ conductance must compensate for the loss of KCNQ1–KCNE3 activity. We used double mutant mouse and pharmacological approaches to identify such a conductance. Ca2+‐dependent anion secretion can also be supported by Ca2+‐dependent KCa3.1 channels after independent CFTR activation, but cAMP‐dependent anion secretion is not further decreased in the combined absence of KCa3.1 and KCNQ1–KCNE3 K+ channel activity. We show that the K2P K+ channel TASK‐2 is expressed in the epithelium of the small and large intestine. Tetrapentylammonium, a TASK‐2 inhibitor, abolishes anion secretory current remaining in the absence of KCNQ1–KCNE3 activity. A double mutant mouse lacking both KCNQ1–KCNE3 and TASK‐2 showed a much reduced cAMP‐mediated anion secretion compared to that observed in the single KCNQ1–KCNE3 deficient mouse. We conclude that KCNQ1–KCNE3 and TASK‐2 play major roles in the intestinal anion and fluid secretory phenotype. The persistence of an, admittedly reduced, secretory activity in the absence of these two conductances suggests that further additional K+ channel(s) as yet unidentified contribute to the robustness of the intestinal anion secretory process.
Molecular Dynamic Study of Boiling Heat Transfer Over Structured Surfaces
Authors: Mukherjee Saikat , Datta Saikat , Kumar Das Arup
Published: November 2017

A phase change heat transfer from liquid to gas is studied in nanoscopic framework using molecular dynamics. Water on structured Si substrate is observed from molecular viewpoint after employing heat flux at a constant rate. Initially, we observe that water settles down on the substrate occupying the free space within the notch to obtain its static shape maintaining intramolecular configuration based on attractive and repulsive forces in neighboring hydroxyl bonds. Upon applying heat flux, we observe that the molecular vibration increases which repels neighbors to make the packing loose. Molecular dilution initiated at the notch and then proceeds to the rest domain. Progressive loosening of the molecules leads to the formation of vapor bubbles which increase in size with time. The rate of growth of this bubble is studied as a function of surface geometry parameters such as notch height, notch width, notch type, and notch spacing. Present simulations enrich the knowledge of surface characteristics on boiling heat transfer from fundamental principle in the molecular domain.
A Novel Semi-Empirical Correlation for Wall Heat Transfer During Saturated Nucleate Flow Boiling
Authors: Hien Hoang Nhan , Song Chul-Hwa , Chu In-Cheol , Euh Dong-Jin
Published: November 2017

Most of the existing empirical correlations for wall heat transfer during flow boiling show a limited predictability stemming mainly from so-called the suppression and enhancement factors, which are introduced to describe the boiling heat transfer hypothetically by a combination of nucleate pool boiling and single-phase forced convection. There is no physical basis strongly supporting the determination of these factors. This study, to avoid such limitations, presents a distinctive approach to the modeling of wall boiling heat transfer utilizing the physical concept of wall heat flux partitioning. A new correlation of local boiling heat transfer coefficient is composed of primary heat transfer mechanisms of transient conduction and forced convection. Heat transfer areas of these mechanisms replace the suppression and enhancement factors in the new correlation and are determined empirically by dimensionless analysis. Based on an experimental database of 3187 points collected for saturated boiling of various working fluids flowing inside channels of different configurations, the new correlation is obtained and compared with existing correlations widely used. The evaluation highlights much better predictability of the present correlation. While the other correlations show relatively large scattering with over 30% deviation from the experimental data, the newly proposed correlation shows an excellent agreement with a deviation of less than 10%. The good predictability would be from the well-structured physical basis and make the new correlation promising in practical boiling heat transfer analysis.
Nucleation mechanism during WS2 plasma enhanced atomic layer deposition on amorphous Al2O3 and sapphire substrates
Authors: Groven Benjamin , Mehta Ankit Nalin , Bender Hugo , Smets Quentin , Meersschaut Johan , Franquet Alexis , Conard Thierry , Nuytten Thomas , Verdonck Patrick , Vandervorst Wilfried , Heyns Marc , Radu Iuliana , Caymax Matty , Delabie Annelies
Published: November 2017

The structure, crystallinity, and properties of as-deposited two-dimensional (2D) transition metal dichalcogenides are determined by nucleation mechanisms in the deposition process. 2D materials grown by atomic layer deposition (ALD) in the absence of a template are polycrystalline or amorphous. Little is known about their nucleation mechanisms. Therefore, the nucleation behavior of WS2 during plasma enhanced ALD from WF6, H2 plasma, and H2S at 300 °C is investigated on amorphous ALD Al2O3 starting surface and on monocrystalline, bulk sapphire. Preferential interaction of the precursors with the Al2O3 starting surface promotes fast closure of the WS2 layer. The WS2 layers are fully continuous at WS2 content corresponding to only 1.2 WS2 monolayers. On amorphous Al2O3, (0002) textured and polycrystalline WS2 layers form with grain size of 5 to 20 nm due to high nucleation density (∼1014 nuclei/cm2). The WS2 growth mode changes from 2D (layer-by-layer) growth on the initial Al2O3 surface to three-dimensional (Volmer–Weber) growth after WS2 layer closure. Further growth proceeds from both WS2 basal planes in register with the underlying WS2 grain, and from or over grain boundaries of the underlying WS2 layer with different in-plane orientation. In contrast, on monocrystalline sapphire, WS2 crystal grains can locally align along a preferred in-plane orientation. Epitaxial seeding occurs locally albeit a large portion of crystals remain randomly oriented, presumably due to the low deposition temperature. The WS2 sheet resistance is 168 MΩ μm, suggesting that charge transport in the WS2 layers is limited by grain boundaries.
Graphene as plasma-compatible blocking layer material for area-selective atomic layer deposition: A feasibility study for III-nitrides
Authors: Deminskyi Petro , Haider Ali , Kovalska Evgeniya , Biyikli Necmi
Published: November 2017

Plasma-assisted atomic layer deposition (PA-ALD) is a promising method for low-temperature growth of III-nitride materials. However, selective film deposition using PA-ALD is challenging mainly due to the plasma-incompatibility of conventional deactivation/blocking layers including self-assembled monolayers and polymers. The main motivation behind this work is to explore alternative plasma-resistant blocking layer materials. Toward this goal, single/multilayered graphene (SLG/MLG) sheets were investigated as potential growth-blocking layers for III-nitride grown via PA-ALD. Prior to PA-ALD growth experiments, partially graphene-covered Si(100) samples were exposed to N2/H2 and N2-only plasma cycles to evaluate the plasma resistance of SLG and MLG. While SLG degraded fairly quickly showing signs of completely etched areas and rough surface morphology, MLG surface displayed certain degree of plasma-resistance. Based on this result, III-nitride PA-ALD experiments were carried out on MLG-patterned Si(100) samples. Crystalline III-nitride film deposition was observed on both Si(100) and graphene surfaces, confirming the rather ineffective nucleation blocking property of graphene surface against PA-ALD process. However, as graphene layers feature relatively weak van der Waals bonds at the substrate/graphene interface as well as between the multilayer graphene interfaces, conventional lift-off process was sufficient to remove the deposited excessive nitride films. InN and AlN-coated samples were ultrasonicated, and blocked/unblocked surfaces were characterized using scanning electron microscopy, x-ray photoelectron spectroscopy, and spectroscopic ellipsometer. While ∼50 nm thick films were measured in the open Si(100) areas, graphene-coated sample portions exhibited limited material growth in the range of 5–15 nm. Although not completely, the MLG surface has considerably blocked the PA-ALD growth process resulting in a usable thickness difference, enabling growth selectivity with postgrowth etch process. An Ar-based physical dry etching recipe was utilized to completely etch the unwanted nitride films from graphene coated area, while about 30 and 40 nm thick InN and AlN films remained on the nonblocked parts of the samples, respectively. As a result, selective deposition of PA-ALD grown AlN and InN has been achieved via graphene-assisted lift-off technique along with subsequent dry-etch process, achieving a maximum growth selectivity of ∼40 nm. With further process recipe optimization and integrating with a suitable patterning technique, the demonstrated graphene-assisted lift-off technique might offer an alternative feasible pathway toward area-selective deposition of III-nitrides and other plasma-necessitating materials.
Incorporating evanescent modes and flow losses into reference impedances in acoustic Thévenin calibration
Authors: Nørgaard Kren Rahbek , Fernandez-Grande Efren , Laugesen Søren
Published: November 2017

This paper proposes an alternative approach to acoustic Thévenin calibration of an ear probe. An existing methodology derives the Thévenin-equivalent source parameters from the measured probe pressures in a number of short waveguides by solving an overdetermined system of equations. This existing methodology is affected by errors caused by evanescent modes when the waveguide model lengths are estimated. These errors introduce a parallel acoustic compliance into the source parameters. The proposed methodology takes into account evanescent modes and flow losses in the transition between the probe tube and waveguides during calibration. This is achieved by positioning the probe tube, without an ear tip, flush with the input plane in waveguides of well-defined dimensions and utilizing the physical rather than estimated lengths to calculate the analytical waveguide models. Terms that model evanescent modes and flow losses are added to the plane-wave impedance and adjusted to minimize the calibration error. It is shown that this method can reduce the calibration error across a wide frequency range and remove the parallel compliance from the source parameters. This approach leads to an independence of the source parameters on the calibration waveguide radius, though subsequent impedance measurements are still affected by evanescent modes.
Measurement of acoustic properties for passive-material samples using multichannel inverse filter
Authors: Li Jianlong , Ma Xiaochen , Li Suxuan , Xiao Fu
Published: November 2017

The measurement of acoustic properties for passive-material samples is strongly interfered by reverberations in a limited space. A multichannel inverse filter (MIF) can achieve spatio-temporal focusing by retransmitting the optimal signal estimated from multichannel impulse responses of the transmitter channel and the underwater acoustic channel. To decrease the influence of reverberations on measurements and improve the measurement precision, a MIF is employed to measure the echo reduction and insertion loss, respectively. The method is demonstrated by simulations and experiments, which were performed in a cylindrical tank to measure the two acoustic parameters for a steel plate sample.
Southern stops: Phonation type differences in Mississippi
Authors: Herd Wendy
Published: November 2017

While the voicing contrast between American English word-initial stops is often described as relatively uniform across speakers (e.g., voiced segments are produced with short positive VOTs while voiceless segments are produced with long positive VOTs), considerable sociophonetic variation exists. The current study investigates variation in the VOT of voiced and voiceless word-initial stops in pot, bot, tot, dot, cot, gotproduced in isolation and in carrier sentences. Participants included 40 native English speakers from Mississippi grouped according to their self-identified gender and ethnicity. As previously reported, African American speakers produced significantly more voiced stops with negative VOTs and more fully voiced closures preceding voiced stops than Caucasian American speakers. While speakers did not differ in their production of voiceless VOT when words were read in isolation, African American speakers maintained closure voicing preceding voiceless stops far more often than Caucasian American speakers. No gender differences were found. These data suggest this voicing variation is due to robust dialectal differences. The possibility that speakers who exhibit more prevoicing and more fully voiced closures are prolonging closure voicing through laryngeal lowering or nasal venting is explored through the examination of pitch and intensity trajectories within the closure and within the following vowel.
Phonological and auditory context effects in the perception of synthetic liquid-plus-stop clusters
Authors: Nearey Terrance M. , Tucker Benjamin V.
Published: November 2017

In experiments with English synthetic stops in the /VCCV/ disyllables /arga, alga, arda, alda/, listeners give more /-da/ responses after /ar-/ syllables [see, e.g., A. Lotto and K. Kluender, Percept. Psychophys. 60, 602–619 (1998)]. The importance of general auditory contrast compared to more specific phonetic mechanisms is a key issue in the literature. In three experiments that used factorially crossed F3 continua for both the liquid /r-l/ and for the stop /g-d/, we recorded responses to all four disyllables (4 alternative forced choice). Experiments 1 and 2 both showed that categorizing the liquid as /r/ biases stop responses toward /d/. However, Experiment 1, which involved a 4-step extreme-/r/ to extreme-/l/ continuum, showed effects consistent with auditory contrast of the F3 values across the stop. Experiment 2 focused on the ambiguous region of the /l-r/ continuum [sampled in 7 steps]. While a clear effect of the [-rd-] phonological bias remained, there was little reliable evidence of contrast effects in F3 across the stop gap. Here, we report analyses of a new larger (n > 60) Experiment 3 with more stimuli (70 compared to less than 50 each) that subsumes the ranges of the previous two experiments. We evaluate the hypothesis (among others) that the auditory-contrast-like effect is confined largely to stimuli with relatively low F3 at the offset of the /VC-/ syllable.
Asymmetric discrimination of phonetically incongruent audio-visual vowels
Authors: Masapollo Matthew , Polka Linda , Morgan James , Franklin Lauren , Ménard Lucie
Published: November 2017

Masapollo, Polka, and Ménard (2017) recently reported a robust directional asymmetry in visual vowel perception: perceivers discriminated a change from an English /u/ viseme to a French /u/ viseme significantly better than a change in the reverse direction. This asymmetry parallels a frequent pattern in auditory vowel perception that points to a universal bias favoring “focal” vowels, whose distal articulatory gestures result in the convergence of adjacent formant frequencies. In the present study, we investigated how the integration of acoustic and visual speech cues influences these directional effects in bimodal vowel perception. In AX discrimination tests in which acoustic and visual cues were phonetically-incongruent, subjects showed an asymmetry, comparable to that found with unimodal stimuli, when there was an acoustic change in focalization, with visual focalization held constant. These findings indicate that acoustic cues are capable of inducing an asymmetry even when there is no cross-modal correspondence between the acoustic and visual channels. We are currently examining whether a similar asymmetry also emerges when there is a visual change in focalization, with acoustic focalization held constant. By comparing different types of audio-visual incongruence, we will be able to examine whether one sensory channel has more perceptual potency than the other.
Filtered and unfiltered sentences produce different spectral context effects in vowel categorization
Authors: Stilp Christian , Assgari Ashley
Published: November 2017

Speech perception is heavily influenced by surrounding sounds. When spectral properties differ between earlier (context) and later (target) sounds, this can produce spectral contrast effects (SCEs) that bias categorization of later sounds. For example, when context sounds have a low F1 bias, listeners report more high F1 responses to the target vowel, and vice versa. SCEs have been demonstrated using a variety of approaches, but most often the context was a single sentence filtered two ways (e.g., low F1 bias, high F1 bias) to introduce spectral properties that biased speech categorization. This maximizes acoustic control over stimulus materials, but vastly understates the acoustic variability of speech. Here, vowel categorization was examined following context sentences that naturally possessed desired spectral properties without any filtering. Sentences with inherent low-F1 or high-F1 peaks in their long-term spectra were presented before a target vowel (/ɪ/-/ɛ/). Filtered sentences with equivalent spectral peaks were included as controls. Across several experiments, as spectral peak magnitudes in filtered and unfiltered contexts increased, SCE magnitudes increased linearly. However, unfiltered sentences produced smaller and more variable SCEs than filtered sentences. Results raise important questions about how closely laboratory studies of speech perception model processes in everyday listening.
Exploiting natural surface noise and ships as sources of opportunity for passive bottom reflection-loss estimation
Authors: Muzi Lanfranco , Siderius Martin
Published: November 2017

The marine ambient-noise field, including natural and anthropogenic sources, can be exploited to estimate the bottom reflection coefficient and the associated loss, which is an important contributor to the total transmission loss in shallow water scenarios. The physical nature of the natural surface-noise field is such that the bottom reflection coefficient can be estimated passively by beamforming on a vertical line array, if there are no localized sources near the array and the noise level generated by waves and wind is adequate. Recently, an algorithm for processing the noise generated by a single ship moving over a wide range of steering angles has been shown to extend the technique to this source of opportunity, even when the natural noise level is too low to produce any measurable loss. In this study, simulation and data from recent experimental campaigns (from arrays moored to the bottom or mounted on an autonomous underwater vehicle) are used to illustrate the technique, and investigate in particular both the effect on the performance of low natural noise levels, and the possibility of using more than one ship as source of opportunity.
Headwaves in ocean acoustic interferometry
Authors: Siderius Martin , Li Jie , Gerstoft Peter
Published: November 2017

In ocean acoustic interferometry, signals measured on two or more receivers are cross-correlated to produces an estimate of the Green's function between these receivers. A “virtual refracted” wave is an early arrival in the time-domain Green's function estimate. This virtual refracted wave is a phenomenon that has been widely reported on in the seismic interferometry literature. This early arrival of energy is also referred to as spurious energy or non-physical arrivals. Although this can be interpreted as a virtual wave it can be a result of the physically propagating headwave. The headwave travels in the seabed and re-radiates into the water column and therefore has important information content such as the seabed sound speed. In seismic interferometry, active sources and horizontal arrays are used but the virtual refracted headwave phenomenon is also observable on vertical arrays and with passive measurements of ocean noise. The signal processing used is a generalization of passive fathometer processing which applies beamforming (including adaptive methods) to the array data. Modeling and experimental data will be presented to show the headwave can be observed and used to estimate the seabed sound speed. The generalized passive fathometer signal processing is compared to the seismic interferometry processing.
Using observations of commercial shipping from horizontal arrays deployed close to a shipping lane to map seabed properties
Authors: Hursky Paul
Published: November 2017

Several horizontal arrays were deployed on the seabed off the coast of Florida, outside Port Everglades. This is a busy site for cruise and container ships, commercial shipping obligated to transmit Automatic Identification System (AIS) information, indicating own latlongs, as well as other parameters of their identity and motion. Acoustic data from these arrays and AIS transmissions were recorded for several days, capturing many passing ships that could then be used as sources at known locations for inversion of seabed properties. One of the arrays had geophones sensing three orthogonal vector components of particle velocity, as well as omni-directional pressure. This area is known to have a distressingly range-dependent seabed, making it difficult to successfully perform matched field processing, for example. We will present our processing of this data, including adaptive beamforming of the geophone data and methods that exploit beam migration patterns (in angle and time difference of arrival) to help isolate multipath arrivals, which are mapped via back-propagating rays to specific grazing angles and locations on the sea floor to provide measurements of bottom loss. The complete set of such observations from ship tracks at multiple frequencies, are incorporated into an inversion for seabed properties.
Using vessel noise from a single hydrophone to estimate environmental properties
Authors: Warner Graham A. , Dosso Stan E. , Hannay David E.
Published: November 2017

This paper estimates seabed and water-column properties of a shallow-water site in the Chukchi Sea using vessel noise recorded on a single ocean-bottom hydrophone. A shallow-hazards seismic survey vessel transited with a fixed heading, passing within 200 m of the hydrophone. Sound pressure levels as a function of frequency and range are inverted using a trans-dimensional (trans-D) Bayesian approach to estimate range-independent environmental properties (sound-speed profile, water depth, and seabed geoacoustic properties). The trans-D inversion allows the data to determine the most appropriate environmental model parameterization in terms of the number of sound-speed profile nodes and subbottom layers. The inversion also estimates the vessel source levels, source depth, hydrophone height above the seabed, a range-correction factor, and error statistics, and provides uncertainty estimates for all model parameters and parameterizations. The sound-speed profile is found to be in good agreement with a measured profile, and the upper sediment-layer sound speed agrees with estimates from separate inversions of airgun and bowhead whale modal dispersion data. This method could be applied to monitor sound-speed profile changes over long time scales, e.g., using Automatic Identification System position data for vessels in a shipping lane.
Acoustic interrogation of objects using signals from rotorcrafts
Authors: Goldman Geoffrey H.
Published: November 2017

Rotorcraft generate acoustic waveforms that are repeatable, loud, and contains a large number of harmonics. They are a good source for generating step frequency-like waveforms that propagate over long distances and can easily be moved to interrogate new locations. One potential application of this source is a monostatic synthetic aperture sodar (SAS). A simple simulation was performed using back projection to generate SAS imagery. The movement of the helicopter generates the synthetic aperture, the signals generated by the main and tail rotors produce the waveform, and microphones mounted on the helicopter receive the reflected sound waves. The measured acoustic signals needs to be motion-compensated and focused, similar to the processing in synthetic aperture radar. A signal bandwidth of 170 Hz will generate an acoustic image with a downrange resolution (c/2B) of approximately 1 meter, and a 100 meter aperture will generate an acoustic image with a crossrange resolution (λ/d) of approximately 2 degrees for a center frequency of 100 Hz. Issues such as turbulence, saturation from self-noise, waveform estimation, acoustic reflectance of targets, range ambiguity, and wind need to be included in future simulations to obtain more realistic results.
Modeling annual variations in high-frequency scattering from sea ice
Authors: Lyons Anthony P.
Published: November 2017

As sea ice evolves naturally through its different growth and decay structures, so too does it manifest important changes in physical properties affecting its acoustic response. Variations in the porosity, permeability, and roughness of the ice lead to changes in scattered and reflected acoustic energy as well as the degree of attenuation. Knowledge of the long-term variations of high-frequency under-ice scattering over annual formation and melting cycles is essentially non-existent as only a limited number of measurements have been performed. Owing to this lack of data, fundamental questions remain as to the dominant mechanisms influencing the under-ice scattering process at any given time. In this work, we will show modeling results for high-frequency acoustic scattering from different types of sea ice as it forms and melts, highlighting the relative influence of various ice parameters on mean scattered levels and the dependence of these levels on frequency and grazing angle. Results yield insight into controlling factors and lead to recommendations for planned long-term measurements from moored instruments.
Acoustic characterization of Penn State’s recording studio above and below the Schroeder frequency
Authors: Kinzie Andrew D. , Russell Daniel A.
Published: November 2017

In most performance spaces, rooms are large enough that most of the audible frequency range falls above the Schroeder frequency, whereas smaller spaces have a significant audible range below the Schroeder frequency. The goal of this study was to characterize the acoustic performance of the control room and live room of Penn State’s recording studio. Both rooms have important roles to play in the operation of a studio which depend on their acoustic character. COMSOL models for each room were created to understand the modal behavior below the Schroeder frequency and measured modes were visualized from frequency response measurement points in one plane at a one foot spacing. For frequencies above the Schroeder frequency, an ODEON model was created and validated against measured impulse responses, where metrics such as T60 and EDT have been considered. By comparing the computer simulations to the measurements, one is able to make recommendations for improvements and provide audio engineers with insight on how they can adapt to the room and refine their craft.