bluuebunny/crossref_metadata_2025 huggingface dataset:
Beyond the pan-genome: current perspectives on the functional and practical outcomes of the distributed genome hypothesis
Authors: Hammond Jocelyn A. , Gordon Emma A. , Socarras Kayla M. , Chang Mell Joshua , Ehrlich Garth D.
Published: November 2020

The principle of monoclonality with regard to bacterial infections was considered immutable prior to 30 years ago. This view, espoused by Koch for acute infections, has proven inadequate regarding chronic infections as persistence requires multiple forms of heterogeneity among the bacterial population. This understanding of bacterial plurality emerged from a synthesis of what-were-then novel technologies in molecular biology and imaging science. These technologies demonstrated that bacteria have complex life cycles, polymicrobial ecologies, and evolve in situ via the horizontal exchange of genic characters. Thus, there is an ongoing generation of diversity during infection that results in far more highly complex microbial communities than previously envisioned. This perspective is based on the fundamental tenet that the bacteria within an infecting population display genotypic diversity, including gene possession differences, which result from horizontal gene transfer mechanisms including transformation, conjugation, and transduction. This understanding is embodied in the concepts of the supragenome/pan-genome and the distributed genome hypothesis (DGH). These paradigms have fostered multiple researches in diverse areas of bacterial ecology including host–bacterial interactions covering the gamut of symbiotic relationships including mutualism, commensalism, and parasitism. With regard to the human host, within each of these symbiotic relationships all bacterial species possess attributes that contribute to colonization and persistence; those species/strains that are pathogenic also encode traits for invasion and metastases. Herein we provide an update on our understanding of bacterial plurality and discuss potential applications in diagnostics, therapeutics, and vaccinology based on perspectives provided by the DGH with regard to the evolution of pathogenicity.
Musicians' Hearing Handicap Index: A New Questionnaire to Assess the Impact of Hearing Impairment in Musicians and Other Music Professionals
Authors: Vardonikolaki Aikaterini , Pavlopoulos Vassilis , Pastiadis Konstantinos , Markatos Nikolaos , Papathanasiou Ilias , Papadelis Georgios , Logiadis Miltos , Bibas Athanasios
Published: November 2020

Purpose

We aimed to develop and validate the Musicians' Hearing Handicap Index (MHHI), a new self-evaluation tool for quantifying occupation-related auditory difficulties in music professionals. Although pure-tone audiometry is often considered the “gold standard” and is usually employed as the main instrument for hearing assessment, it cannot fully describe the impact of hearing dysfunction. The MHHI is an attempt to complement the hearing impairment assessment toolbox and is based on a unique approach to quantify the effects of hearing-related symptoms or hearing loss on the performance of musicians and other music industry professionals.

Method

An initial set of 143 questionnaire items was successively refined through a series of critical appraisals, modifications, and suggestions. This yielded an intermediate questionnaire consisting of 43 items, which was administered to 204 musicians and sound engineers. After exploratory factor analysis, the final form of the MHHI questionnaire was obtained, consisting of 29 items. The questionnaire's test–retest reliability, internal consistency, discriminating power, content validity, criterion validity, and aspects of construct validity and inherent conceptual structure were assessed.

Results

Exploratory factor analysis revealed a combination of four common factors for the 29 validated questionnaire items. They were named “impact on social and working lives,” “difficulties in performance and sound perception,” “communication difficulties,” and “emotional distress.” The MHHI was shown to be a valid and reliable instrument to assess musicians' and sound engineers' occupational difficulties due to hearing impairment and related symptoms.

Conclusion

The ability of the MHHI to discriminate between groups of music professionals with different auditory symptoms or pure-tone audiometry thresholds suggests that auditory symptoms might influence a professional's performance to an extent that cannot be assessed by a pure-tone audiogram.
Autobiographical Memory in Autism Spectrum Disorder, Attention-Deficit/Hyperactivity Disorder, Hearing Loss, and Childhood Trauma: Implications for Social Communication Intervention
Authors: Brien Ashley , Hutchins Tiffany L. , Westby Carol
Published: November 2020

Purpose

Speech-language pathologists (SLPs) work with a variety of populations at risk for poor autobiographical and episodic memory. The purpose of this tutorial is to describe autobiographical memory and how it is affected in children with autism spectrum disorder, attention-deficit/hyperactivity disorder, hearing loss, and childhood trauma, as well as provide clinicians with practical strategies for supporting autobiographical memory in each of these clinical populations.

Method

This tutorial reviews the literature on (a) autobiographical and episodic memory in typical development; (b) its relation to theory of mind, personal narrative skills, and executive functions; (c) elaborative reminiscing in typical development; (d) how autobiographical memory is impaired in children with autism spectrum disorder, attention-deficit/hyperactivity disorder, hearing loss, and childhood trauma; and (e) strategies for supporting autobiographical memory in each clinical population.

Conclusions

When adequately prepared, SLPs are uniquely situated to address autobiographical and episodic memory in their work with children, families, and related professionals. This is a long-overdue focus of such great clinical import that justifies its inclusion in the traditional training and preparation of SLPs. Adapting elaborative reminiscing strategies for use with various clinical populations is promising for facilitating healthy EM development and related cognitive functions.
LOFAR observations of radio burst source sizes and scattering in the solar corona
Authors: Murphy Pearse C. , Carley Eoin P. , Ryan Aoife Maria , Zucca Pietro , Gallagher Peter T.
Published: November 2020

Low frequency radio wave scattering and refraction can have a dramatic effect on the observed size and position of radio sources in the solar corona. The scattering and refraction is thought to be due to fluctuations in electron density caused by turbulence. Hence, determining the true radio source size can provide information on the turbulence in coronal plasma. However, the lack of high spatial resolution radio interferometric observations at low frequencies, such as with the LOw Frequency ARray (LOFAR), has made it difficult to determine the true radio source size and level of radio wave scattering. Here we directly fit the visibilities of a LOFAR observation of a Type IIIb radio burst with an elliptical Gaussian to determine its source size and position. This circumvents the need to image the source and then de-convolve LOFAR’s point spread function, which can introduce spurious effects to the source size and shape. For a burst at 34.76 MHz, we find full width at half maximum (FWHM) heights along the major and minor axes to be 18.8′ ± 0.1′ and 10.2′ ± 0.1′, respectively, at a plane of sky heliocentric distance of 1.75 R⊙. Our results suggest that the level of density fluctuations in the solar corona is the main cause of the scattering of radio waves, resulting in large source sizes. However, the magnitude of ε may be smaller than what has been previously derived in observations of radio wave scattering in tied-array images.
The search for extratidal star candidates around Galactic globular clusters NGC 2808, NGC 6266, and NGC 6397 with Gaia DR2 astrometry
Authors: Kundu Richa , Navarrete Camila , Fernández-Trincado José G. , Minniti Dante , Singh Harinder P. , Sbordone Luca , Piatti Andrés E. , Reylé Céline
Published: November 2020

Context. Extratidal stars are stellar bodies that end up outside the tidal radius of a cluster as a result of internal processes or external forces acting upon it. The presence and spatial distribution of these stars can give us insights into the past evolution of a cluster inside our Galaxy.

Aims. Previous works suggest that globular clusters, when explored in detail, show evidence of extratidal stars. We aim to search for possible extratidal stars in the Galactic globular clusters NGC 6397, NGC 2808, and NGC 6266 using the photometry and proper motion measurements from Gaia DR2 database.

Methods. The extratidal stars for the clusters were selected on the basis of: their distance from the cluster center, similarity in their proper motions to the cluster population, and their position on the color-magnitude diagram of the clusters. Each cluster was explored in an annulus disk from the tidal radius up to five times the tidal radii. The significance level of the number of selected extratidal stars was determined on the basis of the distribution of Milky Way stars according to the Besançon Galaxy model and Gaia data. To understand the observed extratidal features, the orbits of the clusters were also determined using GravPot16.

Results. Finally, 120, 126, and 107 extratidal candidate stars were found lying outside the tidal radius of the globular clusters NGC 6397, NGC 2808, and NGC 6266, respectively. 70%, 25.4%, and 72.9% of the extratidal stars found are located outside the Jacobi radius of NGC 6397, NGC 2808, and NGC 6266, respectively. The spatial distribution of the extratidal stars belonging to NGC 6397 appears S-like, extending along the curved leading and trailing arms. NGC 2808 has an overdensity of stars in the trailing part of the cluster and NGC 6266 seems to have overdensities of extratidal stars in its eastern and northern sides.

Conclusions. Proper motions and color-magnitude diagrams can be used to identify extratidal candidate stars around GCs. Nonetheless, depending on how different the kinematics and stellar populations of a cluster are compared to the Milky Way field, the fraction of contamination can be larger. All three clusters are found to have extratidal stars outside their tidal radii. For NGC 6397 and NGC 2808, these stars may be the result of a combined effect of the disc shocks and tidal disruptions. For NGC 6266, the distribution of extratidal stars is symmetrical around it, most likely indicating that the cluster has an extended stellar envelope.
Search for flares and associated CMEs on late-type main-sequence stars in optical SDSS spectra
Authors: Koller Florian , Leitzinger Martin , Temmer Manuela , Odert Petra , Beck Paul G. , Veronig Astrid
Published: November 2020

Aims.This work aims to detect and classify stellar flares and potential stellar coronal mass ejection (CME) signatures in optical spectra provided by the Sloan Digital Sky Survey (SDSS) data release 14. The sample is constrained to all F, G, K, and M main-sequence type stars, resulting in more than 630 000 stars. This work makes use of the individual spectral exposures provided by the SDSS.

Methods.An automatic flare search was performed by detecting significant amplitude changes in theHαandHβspectral lines after a Gaussian profile was fit to the line core. CMEs were searched for by identifying asymmetries in the Balmer lines caused by the Doppler effect of plasma motions in the line of sight.

Results.We identified 281 flares on late-type stars (spectral types K3 – M9). We identified six possible CME candidates showing excess flux in Balmer line wings. Flare energies inHαwere calculated and masses of the CME candidates were estimated. The derivedHαflare energies range from 3 × 1028− 2 × 1033erg. TheHαflare energy increases with earlier types, while the fraction of flaring times increases with later types. Mass estimates for the CME candidates are in the range of 6 × 1016− 6 × 1018g, and the highest projected velocities are ~300−700 km s−1.

Conclusions.The low detection rate of CMEs we obtained agrees with previous studies, suggesting that for late-type main-sequence stars the CME occurrence rate that can be detected with optical spectroscopy is low.
Probing dark energy with tomographic weak-lensing aperture mass statistics
Authors: Martinet Nicolas , Harnois-Déraps Joachim , Jullo Eric , Schneider Peter
Published: November 2020

We forecast and optimize the cosmological power of various weak-lensing aperture mass (Map) map statistics for future cosmic shear surveys, including peaks, voids, and the full distribution of pixels (1DMap). These alternative methods probe the non-Gaussian regime of the matter distribution, adding complementary cosmological information to the classical two-point estimators. Based on the SLICS and cosmo-SLICSN-body simulations, we buildEuclid-like mocks to explore theS8 − Ωm − w0parameter space. We develop a new tomographic formalism that exploits the cross-information between redshift slices (cross-Map) in addition to the information from individual slices (auto-Map) probed in the standard approach. Our auto-Mapforecast precision is in good agreement with the recent literature on weak-lensing peak statistics and is improved by ∼50% when including cross-Map. It is further boosted by the use of 1DMapthat outperforms all other estimators, including the shear two-point correlation function (γ-2PCF). When considering all tomographic terms, our uncertainty range on the structure growth parameterS8is enhanced by ∼45% (almost twice better) when combining 1DMapand theγ-2PCF compared to theγ-2PCF alone. We additionally measure the first combined forecasts on the dark energy equation of statew0, finding a factor of three reduction in the statistical error compared to theγ-2PCF alone. This demonstrates that the complementary cosmological information explored by non-GaussianMapmap statistics not only offers the potential to improve the constraints on the recentσ8–Ωmtension, but also constitutes an avenue to understanding the accelerated expansion of our Universe.
Shape effects on aerodynamic loading of heliostats
Authors: Merarda Hakim , Aksas Mounir , Andrianne Thomas
Published: November 2020

The effect of the shape of the mirror of a heliostat is studied through wind tunnel tests in uniform smooth and turbulent flow conditions. Three shapes are investigated: square (reference case), octagonal and circular geometries. The forces and moments are measured on reduced scale models of heliostats in low, medium and strong turbulence wind conditions in a uniform wind profile. The turbulence intensity of the flow is adjusted in the wind tunnel test section by the adjunction of passive grids upstream the model. The experimental results are presented for several elevation and azimuth angles. The results showed that: in smooth flow conditions, the geometry of the mirror has very limited effect on the mean force coefficient, while impacting the fluctuating part of the aerodynamic loads. In turbulence flow conditions, the circular mirror/panel is advantageous for the aerodynamic design of the elevation drive and mirror support structure.
Analysis of internal cracks in high carbon casting bloom induced by soft reduction process and its improvement using numerical simulations and industrial experiments
Authors: Zong Nanfu , Huang Jian , Liu Jun , Ma Sida , Jing Tao
Published: November 2020

To comprehensively investigate and improve the internal cracks in high carbon casting bloom induced by the soft reduction process, a three-dimensional mechanical model was developed to calculate the cracking zone, centre solid fraction and the strain states in as-cast bloom. In the present work, the specific relationship between cracking zone area, centre solid fraction and maximum equivalent strain in cracking zone has been established under a number of withdrawal machines. A two-stage sequential soft reduction method was carried out for high carbon bearing steel, which aims to provide theoretical basis for improving the internal quality and effectively decrease the risk of internal cracks. According to the experimental results, the internal cracks were effectively alleviated and center shrinkage cavities were nearly eliminated by optimum designed experiments. Along the bloom central part, the proportion of length where the segregation rate is between 0.95 and 1 has been increased from 16.7% to 91%, and the fluctuation of carbon distribution in the center line of as-cast bloom was decreased to obtain the high homogeneity of the internal structure. In addition, grade of banded carbide in the hot-rolled wire decreased accordingly from 2.5 to 1.67.
Degradation behaviors of coke under complex solution loss conditions
Authors: Zhang Jun , Yu Dongsheng , Guo Rui , Lin Jiaxiong
Published: November 2020

Solution loss reaction of coke provides reducing agent for ironmaking, which is an important chemical reaction in blast furnace. The coke itself is also degraded by the loss of carbon. In this paper, the degradation behavior of coke under complex conditions including alkali metal enrichment, simulated blast furnace temperature and atmosphere was studied. The pore size and pore wall thickness distribution of coke were measured by a microscope to characterize the structure of coke. The gasification reaction rate of coke matrix was measured by a thermogravimetric analyzer to characterize the matrix reactivity of coke. The results show that a coke has high CRI and low CSR, but it has high matrix reactivity and thick pore wall, which may lead higher strength after solution loss under alkali metal enrichment and simulated blast furnace atmosphere and heating conditions.
Radiologische Diagnostik der Nasenhaupt- und Nasennebenhöhlen
Authors: Nelles Christian , Zopfs David , Neuschmelting Hannah
Published: November 2020

Die diagnostische und periinterventionelle Schnittbildgebung der Nasenhaupt- und Nasennebenhöhlen ist heute aus dem Alltag der HNO-Heilkunde nicht mehr wegzudenken. Zu den Aufgaben des Radiologen gehört es, Verdachtsdiagnosen zu bestätigen, Pathologien ätiologisch einzuordnen und deren Ausdehnung exakt zu bestimmen sowie die sinunasale Anatomie und Normvarianten zur Operationsplanung zu beschreiben. CT und MRT ergänzen sich dabei.
Ophthalmology Program Director Perspectives of Scoring Step 1 Pass/Fail
Authors: Hamdan Saif A. , Makhoul Alan T. , Drolet Brian C. , Lindsey Jennifer L. , Law Janice C.
Published: November 2020

Background Scoring for the United States Medical Licensing Examination (USMLE) Step 1 was recently announced to be reported as binary as early as 2022. The general perception among program directors (PDs) in all specialties has largely been negative, but the perspective within ophthalmology remains uncharacterized.

Objective This article characterizes ophthalmology residency PDs' perspectives regarding the impact of pass/fail USMLE Step 1 scoring on the residency application process.

Methods A validated 19-item anonymous survey was electronically distributed to 111 PDs of Accreditation Council for Graduate Medical Education-accredited ophthalmology training programs.

Results Fifty-six PDs (50.5%) completed the survey. The median age of respondents was 48 years and the majority were male (71.4%); the average tenure as PD was 7.1 years. Only 6 (10.7%) PDs reported the change of the USMLE Step 1 to pass/fail was a good idea. Most PDs (92.9%) indicated that this will make it more difficult to objectively compare applicants, and many (69.6%) did not agree that the change would improve medical student well-being. The majority (82.1%) indicated that there will be an increased emphasis on Step 2 Clinical Knowledge (CK) scores, and many (70.4%) felt that medical school reputation will be more important in application decisions.

Conclusion Most ophthalmology PDs who responded to the survey do not support binary Step 1 scoring. Many raised concerns regarding shifted overemphasis on Step 2 CK, uncertain impact on student well-being, and potential to disadvantage certain groups of medical students including international medical graduates. These concerns highlight the need for reform in the ophthalmology application process.
Dorsal Root Entry Zone Lesioning: Systematic Review
Authors: Galafassi Giovanna Zambo , Aguiar Paulo Henrique Pires , Takahashi André Akira , Pagura Jorge Roberto
Published: November 2020

Introduction Dorsal root entry zone (DREZ) leasioning (DREZ-otomy) is considered an effective treatment for chronic pain due to spinal cord injuries, brachial and lumbosacral plexus injuries, postherpetic neuralgia, spasticity, and other conditions. The objective of the technique is to cause a selective destruction of the afferent pain fibers located in the dorsal region of the spinal cord.

Objective To identify and review the effectiveness and the main aspects related to DREZ-otomy, as well as the etiologies that can be treated with it.

Methods The PubMed, MEDLINE and LILACS databases were used as bases for this systematic review, having the impact factor as the selection criteria. The 23 selected publications, totalizing 1,099 patients, were organized in a table for systematic analysis.

Results Satisfactory pain control was observed in 70.1% of the cases, with the best results being found in patients with brachial/lumbosacral plexus injury (70.8%) and the worst, in patients with trigeminal pain (40% to 67%).

Discussion Most of the published articles observed excellent results in the control of chronic pain, especially in cases of plexus injuries. Complications are rare, and can be minimized with the use of new technologies for intraoperative monitoring and imaging.

Conclusion DREZ-otomy can be considered a great alternative for the treatment of chronic pain, especially in patients who do not tolerate the side effects of the medications used in the clinical management or have refractory pain.
Endonasal Endoscopic Pituitary Adenoma Resection in light of the COVID-19 Pandemic: A Technical Report
Authors: Barbosa Danilo Talacimon , Oberman Dan Zimelewicz , Moreira Alick Durão , Borges Luisa , Gonçalves Felipe , Cabral Gustavo Sereno Porto , Barros Rafael Rego , Vaitsman Rafael , Sodré Rodrigo , Kleskoski João , Maia Orlando , Correa Jorge Luis Amorim
Published: November 2020

Introduction The endoscopic endonasal transsphenoidal approach (EETA) is routinely used to treat sellar and suprasellar tumors. It provides safe and direct access to tumors in these locations, with wide visualization of anatomical landmarks and great surgical results. With the COVID-19 pandemic, despite the high risk of transmission involved, various surgical procedures cannot be postponed due to their emergency.

Case Report A 62-year-old female presented in the previous two months with headaches, followed by bilateral severe visual loss. In 2016, she was submitted to subtotal resection of a non-secretory macroadenoma. Because of the progressive visual deficits, the EETA was used to the resect the pituitary adenoma.

Technical Note We developed a low-cost adaptation to the surgical fields, covering the patient's head and superior trunk with a regular surgical microscope bag with a tiny slit to enable the endoscope and surgical instruments to enter the nose, thus protecting the personnel in the operating room from the aerosolization of particles. This makes surgery safer for the surgical team and for the patient.

Conclusion In view of the lack of literature on this subject, except for some reports of experiences from some services around the world, we describe the way we have adjusted the EETA in the context of the COVID-19 pandemic.
Computed Tomographic Measurement of Trochlear Depth in Three Breeds of Brachycephalic Dog
Authors: Matchwick Alexandra , Bridges Janis P. , Mielke Benjamin , Pead Matthew J. , Phillips Andrew , Meeson Richard L.
Published: November 2020

Objective The aim of this study was to determine the trochlear sulcus depth of three common brachycephalic breeds at risk of medial patellar luxation.

Study Design Retrospective blinded clinical study using a previously validated ratio (T/P) of maximal trochlear sulcus depth (T) and maximal patellar craniocaudal thickness (P) measured on computed tomography, to assess trochlear sulcus depth in Pugs, French Bulldogs and English Bulldogs without clinical patellar luxation. The effect of breed on T/P was assessed using one-way linear regression models.

Results The mean T/P was affected by breed (p < 0.001). There was significant difference between Pugs (0.45) and French Bulldogs (0.38) and between Pugs and English Bulldogs (0.4). There was no significant difference between Pugs and previously published data for non-brachycephalic and mixed breed dogs (0.46) (p = 0.39). Mean T/P was significantly reduced in the brachycephalic dog breeds combined compared with the previously published data (p < 0.001).

Conclusion The trochlear sulcus varies by breed and was more shallow in French and English Bulldogs than Pugs, hence a shallow sulcus may be a breed-driven characteristic. The three breeds assessed are at risk of patellar luxation but sulcus depth did not directly correlate with previously published risk factors—the contribution of sulcus depth to the aetiopathogenesis of patellar luxation remains unclear. Trochlear recession to achieve patellar coverage of 50% may be excessive considering maximal breed normal depth.
The physical fundamentals of the electrical conductivity in nanotube-based composites
Authors: Balberg Isaac
Published: November 2020

In this article, we show that the classical theories of percolation, continuum percolation, and effective medium theory can account for all the features of electrical conductivity dependence on the content of the fibrous filler in composites in which the conducting particles are nanotubes, nanofibers, and nanowires. We show this by applying the corresponding concepts of the percolation nodes–links–blobs model, the excluded volume and the effective local conductance. In particular, in contrast with ad hoc or empirical evaluations of others, our analysis accounts simultaneously and quantitatively for the variety of values of the percolation thresholds, the electrical conductivity exponent, and the conductivity prefactor in all those systems. Our approach, therefore, provides a well-based theoretical physical framework for a comprehensive understanding of the electrical conductivity in those composites.
Spectroscopic near-infrared photodetectors enabled by strong light–matter coupling in (6,5) single-walled carbon nanotubes
Authors: Mischok Andreas , Lüttgens Jan , Berger Felix , Hillebrandt Sabina , Tenopala-Carmona Francisco , Kwon Seonil , Murawski Caroline , Siegmund Bernhard , Zaumseil Jana , Gather Malte C.
Published: November 2020

Strong light–matter coupling leads to the formation of mixed exciton–polariton states, allowing for a rigorous manipulation of the absorption and emission of excitonic materials. Here, we demonstrate the realization of this promising concept in organic photodetectors. By hybridizing the E11 exciton of semiconducting (6,5) single-walled carbon nanotubes (SWNTs) with near-infrared cavity photons, we create spectrally tunable polariton states within a photodiode. In turn, we are able to red-shift the detection peak that coincides with the lower polariton band. Our photodiodes comprise a metal cavity to mediate strong coupling between light and SWNTs and utilize P3HT and PC70BM as the electron donor and acceptor, respectively. The diodes are formed either via mixing of SWNTs, P3HT, and PC70BM to create a bulk heterojunction or by sequential processing of layers to form flat heterojunctions. The resulting near-infrared sensors show tunable, efficient exciton harvesting in an application-relevant wavelength range between 1000 nm and 1300 nm, with optical simulations showing a possible extension beyond 1500 nm.
A compact low-frequency sound-absorbing metasurface constructed by resonator with embedded spiral neck
Authors: Guo Jingwen , Zhang Xin , Fang Yi , Jiang Ziyan
Published: November 2020

This Letter reports an acoustic metasurface for low-frequency sound absorption with a compact size in both vertical and lateral directions, which is constructed by a series of Helmholtz resonators with spiral extended necks. Analytical, numerical, and experimental results show that the metasurface with a thickness of 13.5 mm possesses total sound absorption at 320 Hz under normal incidence. The thickness of the prototype is only about 1/80th of the operating wavelength (λ). What is more, the side length of the basic unit (25 mm) is also on the deep-subwavelength scale (λ/43). To widen the narrow effective absorption bandwidth of the uniform absorber, the strategy of parallel arrangement of different elements is employed. A wideband absorber consisting of four inhomogeneous units is optimally designed to maximize the averaged absorption coefficient in a prescribed frequency range of [360, 410] Hz. The experimental results show that the absorber with a thickness of 13.5 mm exhibits high absorption (the averaged absorption coefficient is about 0.9) in the desired frequency range. The features of effective low-frequency sound absorption, compact dimension, and high absorption with a tunable bandwidth make the proposed acoustic metasurface promising for various applications in noise control engineering.
日语母语者汉语是非疑问句语调习得研究
Authors: Xiao Yao , Liu Yi
Published: November 2020

抽象

本实验通过考察日本学习者汉语陈述句和疑问句语调的产出和感知，分析学习者疑问句语调习得情况，并结合其母语疑问句语调特点分析偏误产生原因，总结其习得难点，为实际教学提供参考。学习者在音高上线、下线、调域、句末音高等方面均与母语者存在较大差异，总的来说，其语调感知能力先于产出能力的发展。
汉语女性第三人称指代词 “她”字的发展、使用和教学
Authors: Chiang Mien-hwa , Yang Lei
Published: November 2020

提要

第三人称指代词的基本功能是替代一个实体专用名词，避免表述的累赘重复。在1919年新文化运动之前，汉语中的“他”一直是一个中性第三人称指代词，既可指代男性,也可指代女性, 还可指代一切其他事物。汉语女性第三人称指代词的 “她”
直到二十世纪早期才出现。在现代社会中，“她”
字笔画简单，运用易教易学，但是为人所忽略的是由人字旁的“他”到女字旁的“她”紧密联系着近代中国社会和语言的变化。本文旨在结合文化史、语言学和语言认知来描述女性第三人称指代词在书面语、口语中的发展。通过讨论中国早期作品中关于女性人物的叙述，分析新文化运动后“她”字的产生、确立和使用，作者认为在现代汉语中，“她”字的存在，不仅可以避免专用名词的累赘重复，还能够降低第三人称代词在文本中回指关系的模糊性。然而，在汉语教学中，由于汉语省略主语和中性“他”在近现代汉语指代范围不清的特点，汉语学习者时不时在阅读和写作中有第三人称指代对象模糊现象。因此，汉语老师需要在教学实践中帮助学生特别厘清“他”与“她”的指代关系。
Africa–EU relations and natural resource governance: understanding African agency in historical and contemporary perspective
Authors: Money Duncan , Frøland Hans Otto , Gwatiwa Tshepo
Published: November 2020

This article examines the changing forms of African agency in the context of contestations over natural resource governance with the European Union. The authors argue that EU policy is motivated by material self-interest but that it has not been able to successfully implement these policies. The way these policies have been challenged by African states has changed, however. The authors argue that a crucial context for this is the failure of the New International Economic Order in the 1970s. The failure of these initiatives helps to explain why the impetus for natural resource governance continues to come from outside the African continent.
On the value of the Immirzi parameter and the horizon entropy
Authors: Pigozzo Cássio , Bacelar Flora S , Carneiro Saulo
Published: November 2020

In loop quantum gravity (LQG) the quantisation of general relativity leads to precise predictions for the eigenvalues of geometrical observables like volume and area, up to the value of the only free parameter of the theory, the Barbero–Immirzi (BI) parameter. With the help of the eigenvalues equation for the area operator, LQG successfully derives the Bekenstein–Hawking entropy of large black holes with isolated horizons, fixing at this limit the BI parameter as γ ≈ 0.274. In the present paper we show some evidence that a black hole with angular momentum ℏ and Planck mass is an eigenstate of the area operator provided that

γ
=

3

/
6
≈
1.05
×
0.274

. As the black hole is extremal, there is no Hawking radiation and the horizon is isolated. We also suggest that such a black hole can be formed in the head-on scattering of two parallel standard model neutrinos in the mass state m
2 (assuming m
1 = 0). Furthermore, we use the obtained BI parameter to numerically compute the entropy of isolated horizons with areas ranging up to

250

l

P

2

, by counting the number of micro-states associated to a given area. The resulting entropy has a leading term

S
≈
0.25

A

, in agreement to the Bekenstein–Hawking entropy. As the identification of the above eigenstate rests on the matching between classical areas and quantum area eigenvalues, we also present, on the basis of an effective quantum model for the Schwarzschild black hole recently proposed by Ashtekar, Olmedo and Singh, an expression for the quantum corrected area of isolated horizons, valid for any black hole mass. Quantum corrections are shown to be negligible for a Planck mass black hole, of order 10−3 relative to the classical area.
Reply to Comment on ‘Forces on hockey players: vectors, work, energy and angular momentum’
Authors: Nässén Nina , Nässén Hans-Åke , Eriksson Urban , Pendrill Ann-Marie
Published: November 2020

Bracko has commented on our paper ‘forces on hockey players: vectors, work, energy and angular momentum’and refers to extensive studies on skaters using traditional techniques. We note that results based on one skating technique, such as a correlation between stride rate and speed, cannot be immediately applied to a different technique.
Forced precession of a gyroscope and its application to Laithwaite’s engine
Authors: Provatidis Christopher G
Published: November 2020

The forced precession of a symmetrical gyroscope is studied for the particular case in which the axle of a flywheel is pivoted by a hinge joint and follows a horizontal circular path of a given radius. The aforementioned setup appears in the so-called Laithwaite engine, the detailed mechanics of which are still an enigma. Instead of applying Lagrangian equations, Newton’s second law is applied to the rotating gyroscope with respect to its center of mass. Three novel Euler equations are developed that are much longer than those found in textbooks. In this mechanical system, which is characterized by one degree of freedom, the main nonlinear governing equation is identified and then MATLAB code is developed to obtain and visualize the numerical solution. Under particular conditions that ensure small oscillations of the gyroscope’s axle (a maximum oscillation of eight degrees in the lean angle) near the horizontal plane through the pivot, a linearization is performed and is successfully compared with the aforementioned nonlinear numerical solution. The computer program facilitates the understanding and calculation of physical quantities such as the internal forces and moments, support forces and power transmission from the drive motor. In particular, it is shown that, for a hinge joint, the period of oscillation differs from that of a rotating pivot, which is crucial to the debate about whether such an engine may produce a net thrust, or not. A relevant paradox is resolved.
Oversmoothing Tikhonov regularization in Banach spaces
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Authors: Chen De-Han , Hofmann Bernd , Yousept Irwin
Published: November 2020

This paper develops a Tikhonov regularization theory for nonlinear ill-posed operator equations in Banach spaces. As the main challenge, we consider the so-called oversmoothing state in the sense that the Tikhonov penalization is not able to capture the true solution regularity and leads to the infinite penalty value in the solution. We establish a vast extension of the Hilbertian convergence theory through the use of invertible sectorial operators from the holomorphic functional calculus and the prominent theory of interpolation scales in Banach spaces. Applications of the proposed theory involving ℓ
1, Bessel potential spaces, and Besov spaces are discussed.
Theoretical study of the control of absorption, transparency, and amplification in a microwave- and RF-driven four-level (Δ + ∇)-type closed-contour interaction system
Authors: Das Aparajita , Saha Jayanta K , Hossain Md Mabud
Published: November 2020

This paper describes a theoretical study of the optical responses of an atomic medium to the probe field in a four-level (Δ + ∇)-type closed-contour interaction system driven by two pump laser fields (P1, P2), one probe laser field (Pr) and two microwave or radio frequency (RF) coupling fields (L, U). Here, L and U are considered to connect the forbidden electric dipole transitions, i.e. two hyperfine ground states of the Δ subsystem and two hyperfine excited states of the ∇ subsystem, respectively. Since each subsystem is a closed-loop system, relative phases are thought to be present between the optical fields (pump and probe fields), and the microwave or RF fields. The manipulation of the quantum coherence of the system by the strengths of coupling fields along with the relative phases is demonstrated in terms of the changes occurring in the absorption of the probe field by the medium. The probe absorption and dispersion profiles are extracted by numerically solving the optical Bloch equations for the system under steady-state conditions. In this study, we start by illuminating the system with the probe only, and then, by applying the pump fields and the coupling fields one by one, the changes in the absorptive and dispersive probe line profiles are investigated for two distinct cases that depend on the relative strengths of the pump fields, e.g. when P2 is stronger than P1 and vice versa. Furthermore, the individual effects of the strengths and phases of the coupling fields on the probe absorption, transparency and amplification are also explored for both cases. All the changes that appear in the probe signal as a result of the application of different fields are explained by the modified interaction fields or the corresponding effective Rabi frequencies obtained from the partial dressed-state analysis.
Exploration of the high-order harmonic generation from periodic potentials by Bohmian trajectories
Authors: Pan Xue-Fei , Li Bo , Qi Tong , Zhang Jun , Liu Xue-Shen
Published: November 2020

The recombination processes of the electrons in solid are illustrated by solving the time-dependent Schrödinger equation. The results show that the Bohmian trajectories and the time evolution of the electronic probability density agrees very well, which demonstrates that we can use the Bohmian trajectories to investigate the recombination processes of the electrons in solid. We select the region where the probability density of the electron reached the strongest and the weakest as the initial position of the calculated Bohmian trajectories, one can see that the Bohmian trajectories have similar structures. In addition, our results show that the emission time of the solid high-order harmonic generation (HHG) spectra from the time-frequency distribution agrees well with the time that the Bohmian trajectories change direction. By regulating the phase of the electric field, the electrons can move farther, which will result in the broad cutoff of the HHG. We have also demonstrated that the similar structure of the Bohmian trajectories of the solid with a defect for different initial positions disappears due to the broken periodic structure, which further illustrates that the motion processes of the electrons in solid depend on the structure of the solid.
Voltage tunable low damping YIG/PMN-PT multiferroic heterostructure for low-power RF/microwave devices
Authors: Zhao Yanan , Li Yaojin , Zhu Shukai , Chen Chen , Yao Mouteng , Zhao Yifan , Hu Zhongqiang , Peng Bing , Liu Ming , Zhou Ziyao
Published: November 2020

Voltage-tunable RF/microwave devices attract great attention due to their low power consumption; however, they still suffer from the fundamental dilemma between large tunability and low insertion loss. In this paper, yttrium iron garnet (YIG) polycrystalline thin films with low microwave loss (<3 × 10−4) were directly deposited on mica substrates via a van der Waals force and then transferred onto PMN-PT substrates. The in-plane magnetic anisotropy of YIG was tuned by the in-plane biaxial stress of PMN-PT, and an improved voltage tunability (175 MHz) of in-plane FMR fr
was obtained due to the removal of the substrate clamping effect. Moreover, our samples still represent good frequency stability (4–12 GHz) during the tuning process. It is of significance for exploiting novel, portable, low-loss RF/microwave devices in the future.
Microstructural dependence of residual stress in reactively sputtered epitaxial GaN films
Authors: Monish M , Major S S
Published: November 2020

Epitaxial GaN films were grown on c-sapphire by rf magnetron reactive sputtering of GaAs at different partial pressures of nitrogen in Ar–N2 sputtering atmosphere. High-resolution x-ray diffraction and φ-scans reveal the mosaic growth of c-axis oriented, wurtzite GaN films. The c and a parameters were independently determined to obtain the corresponding in-plane and out-of-plane strain components. Raman measurements confirmed the in-plane strain behavior. The surface morphology and elemental composition of films were studied by atomic force microscopy and secondary ion mass spectroscopy, respectively. High-resolution ω-2θ, ω, and in-plane φ-rocking curve scans were used to obtain micro-strain, screw and edge dislocation densities, respectively. The films grown at 30%–100% N2 reveal dominance of edge (∼1012 cm−2) over screw (∼1010 cm−2) dislocations, with both approaching similar densities at lower N2 percentages. The strain data has been analyzed to separate the hydrostatic and biaxial contributions and their dependences on N2 percentage. The film grown at 100% N2 displays large hydrostatic strain and micro-strain due to the presence of excess/interstitial nitrogen. The hydrostatic strain and micro-strain decrease substantially with initial decrease of N2 percentage, but increase slightly in the films grown below 30% N2, primarily due to the incorporation of Ar. The films grown below 75% N2 display growth-related intrinsic tensile stress, originating from crystallite coalescence. The stress reversal from tensile to compressive, seen in the films grown at higher N2 percentages is primarily attributed to the incorporation of excess/interstitial nitrogen into grain boundaries and the tensile side of edge dislocations. The decrease of intrinsic tensile stress in the films grown below 30% N2 is attributed to the incorporation of Ar and their voided structure.
Coupled mechanisms of the keyhole, energy transfer and compositional change associated with the variable polarity plasma arc process
Authors: Wu Dongsheng , Tashiro Shinichi , Hua Xueming , Tanaka Manabu
Published: November 2020

A three-dimensional numerical model that coupled the arc, keyhole and weld pool was developed to investigate the keyhole behavior and energy transfer of an aluminum alloy in a variable polarity plasma arc welding process. The convective pattern in the weld pool was measured using an advanced x-ray transmission system. The elemental distribution of the bead was determined using an electron-probe microanalyzer. The coupled mechanisms of the keyhole, energy transfer, and compositional change were revealed. With a keyhole, both the arc energy loss and energy input increase, while the total energy transported from the arc to the weld pool decreases a bit, so the arc energy efficiency decreases. The heat flux at the keyhole is low and decentralized, resulting in low keyhole temperature; thus, the loss of elements with low boiling points due to evaporation can be ignored. Elements can be sufficiently mixed and distributed uniformly throughout the bead.
Alternative formulation of the induced surface and curvature tensions approach
Authors: Bugaev Kyrill A
Published: November 2020

We develop a novel method to analyze the excluded volume of the multicomponent mixtures of classical hard spheres in the grand canonical ensemble. The method is based on the Laplace–Fourier transform technique and allows one to account for the fluctuations of the particle number density for the induced surface and curvature tensions equation of state. As a result one can go beyond the Van der Waals (VdW) approximation by obtaining the suppression of the induced surface and curvature tensions coefficients at moderate and high packing fractions. In contrast to the standard induced surface and curvature tensions equation of state the suppression of these coefficients is not the exponential, but a power-like one. The obtained alternative equation of state is further generalized to account for higher virial coefficients. This result is straightforwardly generalized to the case of quantum statistics.
Understanding charged vesicle suspensions as Wigner glasses: dynamical aspects
Authors: Porpora G , Rusciano F , Guida V , Greco F , Pastore R
Published: November 2020

Suspensions of charged vesicles in water with added salt are widespread in nature and industrial production. Here we investigate, via Brownian dynamics simulations, a model that grasps the key features of these systems, with bidisperse colloidal beads interacting via a hard-core and an electrostatic double layer potential. Our goal is to focus on a set of interaction parameters that is not generic but measured in recent experiments, and relevant for a class of consumer products, such as liquid fabric softeners. On increasing the volume fraction in a range relevant to real formulation, we show that the dynamics become progressively slower and heterogeneous, displaying the typical signatures of an approaching glass transition. On lowering the salt concentration, which corresponds to increasing the strength and range of the electrostatic repulsion, the emergence of glassy dynamics becomes significantly steeper, and, remarkably, occurs at volume fractions well below the hard-sphere glass transition. The volume fraction dependence of the structural relaxation time at different salt concentration is well described through a functional law inspired by a recently proposed model (Krausser et al 2015 Proc. Natl Acad. Sci. USA
112 13762). According to our results, the investigated system may be thought of as a Wigner glass, i.e. a low-density glassy state stabilized by long-range repulsive interactions. Overall, our study suggests that glassy dynamics plays an important role in controlling the stability of these suspensions.
Damping via the hyperfine interaction of a spin-rotation mode in a two-dimensional strongly magnetized electron plasma
Authors: Dickmann S
Published: November 2020

We address damping of a Goldstone spin-rotation mode emerging in a quantum Hall ferromagnet due to laser pulse excitation. Recent experimental data show that the attenuation mechanism, dephasing of the observed Kerr precession, is apparently related not only to spatial fluctuations of the electron Landé factor in the quantum well, but to a hyperfine interaction with nuclei, because local magnetization of GaAs nuclei should also experience spatial fluctuations. The motion of the macroscopic spin-rotation state is studied microscopically by solving a non-stationary Schrödinger equation. Comparison with the previously studied channel of transverse spin relaxation (attenuation of Kerr oscillations) shows that relaxation via nuclei involves a longer quadratic stage of time-dependance of the transverse spin, and, accordingly, an elongated transition to a linear stage, so that a linear time-dependance may not be revealed.
Collective excitations in spin-polarized bilayer graphene
Authors: Van Men Nguyen , Khanh Nguyen Quoc , Kim Phuong Dong Thi
Published: November 2020

We calculate the plasmon frequency ω and damping rate γ of plasma oscillations in a spin-polarized BLG system. Using the long wavelength approximation for dynamical dielectric function, we obtain an analytical expression for plasmon frequency showing that degree of spin polarization P has negligible effect on the long wavelength plasmon frequency. Numerical calculations demonstrate that the plasmon frequency increases (decreases) noticeably (slightly) with the increase in spin polarization in large (small) wave-vector q region. We also find that the damping rate and the shape of γ as a function of q depend strongly on P. The increase in carrier density decreases significantly both plasmon frequency and damping rate independently of the spin polarization. The numerically calculated critical wave vector, at which the plasmon dispersion curve hits the edge of electron–hole continuum, decreases with P and can be used to experimentally determine the degree of spin polarization.