bluuebunny/crossref_metadata_2025 huggingface dataset:
Author Correction: Protecting nursery areas without fisheries management is not enough to conserve the most endangered parrotfish of the Atlantic Ocean
Authors: Roos Natalia C. , Longo Guilherme O. , Pennino Maria Grazia , Francini‑Filho Ronaldo B. , Carvalho Adriana R.
Published: March 2021

An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Brain pathology recapitulates physiology: A network meta-analysis
Authors: Vanasse Thomas J. , Fox Peter T. , Fox P. Mickle , Cauda Franco , Costa Tommaso , Smith Stephen M. , Eickhoff Simon B. , Lancaster Jack L.
Published: March 2021

Network architecture is a brain-organizational motif present across spatial scales from cell assemblies to distributed systems. Structural pathology in some neurodegenerative disorders selectively afflicts a subset of functional networks, motivating the network degeneration hypothesis (NDH). Recent evidence suggests that structural pathology recapitulating physiology may be a general property of neuropsychiatric disorders. To test this possibility, we compared functional and structural network meta-analyses drawing upon the BrainMap database. The functional meta-analysis included results from >7,000 experiments of subjects performing >100 task paradigms; the structural meta-analysis included >2,000 experiments of patients with >40 brain disorders. Structure-function network concordance was high: 68% of networks matched (pFWE < 0.01), confirming the broader scope of NDH. This correspondence persisted across higher model orders. A positive linear association between disease and behavioral entropy (p = 0.0006;R2 = 0.53) suggests nodal stress as a common mechanism. Corroborating this interpretation with independent data, we show that metabolic ‘cost’ significantly differs along this transdiagnostic/multimodal gradient.
Gold nanoparticle integrated artificial nanochannels for label-free detection of peroxynitrite
Authors: Wu Jing , Wang Xing , Ge Lei , Lv Rui , Zhang Fan , Liu Zhihong
Published: March 2021

A label-free method for rapid and highly sensitive detection of ONOO− was proposed by employing ABEI@AuNPs integrated nanochannels. This work paves a new way to develop a versatile platform for the detection of different biological small molecules.
Spontaneous bond dissociation cascades induced by Benclusters (n= 2,4)
Authors: Vos Eva , Corral Inés , Montero-Campillo M. Merced , Mó Otilia , Elguero José , Alkorta Ibon , Yáñez Manuel
Published: March 2021

Be4clusters are very powerful Lewis acids leading to the total dissociation of all the bonds of the Lewis bases interacting with them. The product of the bond dissociation cascade possesses a hyper-coordinated center. Multireference methods are needed to correctly describe these complexes.
Predicting the structure and NMR coupling constant 1J(129Xe–19F) of XeF6 using quantum mechanics methods
Authors: Paschoal Diego F. S. , Dos Santos Hélio F.
Published: March 2021

For predicting the 1J(129Xe–19F) coupling constant, the (XeF6)4 structure must be considered. At BMK/NMR-DKH//BH and HLYP/def2-SVP level, our calculated value of e−308 Hz for 1J(129Xee–19F) presented a relative deivation of only 7% in relation to the experimental value of −331.7 Hz.
Anti-electrostatic hydrogen bonding between anions of ionic liquids: a density functional theory study
Authors: Chen Junwu , Dong Kun , Liu Lei , Zhang Xiangping , Zhang Suojiang
Published: March 2021

Inter-anionic hydrogen bonds in ionic liquids have been found using DFT calculations, and the induction and dispersion forces are found to be the key factors to overcome the strong Coulomb repulsion.
Mapping the morphological identifiers of distinct conformations via the protein translocation current in nanopores
Authors: Zhang Mingkun , Chen Shenbao , Hu Jinrong , Ding Qihan , Li Linda , Lü Shouqin , Long Mian
Published: March 2021

A theoretical method based on molecular dynamics simulations was proposed to resolve the morphological signatures of protein conformations by orientation-modulated principle in nanopore sensing technique.
Correction: Copper(ii) complex of N-truncated amyloid-β peptide bearing a His-2 motif as a potential receptor for phosphate anions
Authors: Tobolska Aleksandra , Wezynfeld Nina E. , Wawrzyniak Urszula E. , Bal Wojciech , Wróblewski Wojciech
Published: March 2021

Correction for ‘Copper(ii) complex of N-truncated amyloid-β peptide bearing a His-2 motif as a potential receptor for phosphate anions’ by Aleksandra Tobolska et al., Dalton Trans., 2021, DOI: 10.1039/d0dt03898a.
Tunable CsPb(Br/Cl)3perovskite nanocrystals and further advancement in designing light emitting fiber membranes
Authors: Abir Sk Shamim Hasan , Gupta Santosh K. , Ibrahim A. , Srivastava Bhupendra B. , Lozano Karen
Published: March 2021

Design of blue and green emitting CsPb(Cl/Br)3and their further exploration to develop light emitting fibers with enhanced quantum yield and high color purity.
Controllable synthesis of CoFe2Se4/NiCo2Se4 hybrid nanotubes with heterointerfaces and improved oxygen evolution reaction performance
Authors: Wang Huan , Sun Zhonghua , Zou Xiaoran , Ren Jianhai , Zhang Chun-yang
Published: March 2021

We demonstrate the controllable synthesis of CoFe2Se4/NiCo2Se4 hybrid nanotubes with heterointerfaces and improved oxygen evolution reaction performance.
Conductive electrodes of metallic-organic compound CH3CuS nanowires for all-solid-state flexible supercapacitors
Authors: Wang Xiaodan , Lu Yao , Zhao Haofei , Sun Yinghui , Wang Rongming
Published: March 2021

Flexible and conductive electrodes are one of the most important components for flexible supercapacitor.  Herein, a flexible supercapacitor device based on CH3CuS nanowire electrodes was fabricated.
Correction: In silico decryption of serotonin–receptor binding: local non-covalent interactions and long-range conformational changes
Authors: Mondal Padmabati
Published: March 2021

Correction for ‘In silico decryption of serotonin–receptor binding: local non-covalent interactions and long-range conformational changes’ by Padmabati Mondal et al., RSC Adv., 2020, 10, 37995–38003, DOI: 10.1039/D0RA05559J.
An autophagy-related prognostic signature associated with immune microenvironment features of uveal melanoma
Authors: Zheng Zhuotao , Zhang Lingyue , Tu Zewei , Deng Yan , Yin Xiaolong
Published: March 2021

Autophagy is involved in cancer initiation and progression but its role in uveal melanoma (UM) was rarely investigated. Herein, we built an autophagy-related gene (ARG) risk model of UM patients by univariate Cox regression and least absolute shrinkage and selection operator (Lasso) regression model and filtrated out nine prognostic ARGs in The Cancer Genome Atlas (TCGA) cohort. Survival and Receiver Operating Characteristic (ROC) Curve analysis in the TCGA and other four independent UM cohorts (GSE22138, GSE27831, GSE44295 and GSE84976) proved that the ARG-signature possessed robust and steady prognosis predictive ability. We calculated risk scores for patients included in our study and patients with higher risk scores showed worse clinical outcomes. We found the expressions of the nine ARGs were significantly associated with clinical and molecular features (including risk score) and overall survival (OS) of UM patients. Furthermore, we utilized univariate and multivariate Cox regression analyses to determine the independent prognostic ability of the ARG-signature. Functional enrichment analysis showed the ARG-signature was correlated with several immune-related processes and pathways like T-cell activation and T-cell receptor signaling pathway. Gene set enrichment analysis (GSEA) found tumor hallmarks including angiogenesis, IL6-JAK-STAT3-signaling, reactive oxygen species pathway and oxidative phosphorylation were enriched in high-risk UM patients. Finally, infiltrations of several immune cells and immune-related scores were found significantly associated with the ARG-signature. In conclusion, the ARG-signature might be a strong predictor for evaluating the prognosis and immune infiltration of UM patients.
Efficient secret key generation scheme of physical layer security communication in ubiquitous wireless networks
Authors: Xiong Hailiang , Wang Guangyuan , Ding Jian , Zhu Weihong , Xu Hongji , Hu Changwu , Mai Zhenzhen , Bian Ruochen
Published: March 2021

This paper focuses on high efficiency secret key generation mechanism of physical‐layer communication over fading channels in ubiquitous wireless networks. The secret key rate via traditional physical‐layer approach could be limited when the wireless propagation channels connecting two sensors change slowly. To generate a high‐rate secret key and improve the communication efficiency over quasi‐static block fading channels, a novel multi‐randomness device‐to‐device secret key generation strategy and a cooperative communication mechanism aided by relay nodes are proposed. In the proposed schemes, the legitimate members to send random signals rotationally in every coherent time are set; thus, two legitimate ubiquitous wireless network members, Alice and Bob, can obtain the potential correlated information by exploiting the randomness and the reciprocity of the wireless propagation channels. Considering the reciprocity of wireless channels is variable while the forward channel gain and backward channel gain are correlated in coherent time, a modified secret key generation scheme is proposed via layered coding with theoretical secret key rates derived. The simulation results show that the proposed scheme outperforms traditional approaches with favourable application prospects in ubiquitous wireless communications networks and internet of things.
Towards accurate classification of skin cancer from dermatology images
Authors: Gautam Anjali , Raman Balasubramanian
Published: March 2021

Skin cancer is the most well‐known disease found in the individuals who are exposed to the Sun's ultra‐violet (UV) radiations. It is identified when skin tissues on the epidermis grow in an uncontrolled manner and appears to be of different colour than the normal skin tissues. This paper focuses on predicting the class of dermascopic images as benign and malignant. A new feature extraction method has been proposed to carry out this work which can extract relevant features from image texture. Local and gradient information from and directions of images has been utilized for feature extraction. After that images are classified using machine learning algorithms by using those extracted features. The efficacy of the proposed feature extraction method has been proved by conducting several experiments on the publicly available image dataset 2016 International Skin Imaging Collaboration (ISIC 2016). The classification results obtained by the method are also compared with state‐of‐the‐art feature extraction methods which show that it performs better than others. The evaluation criteria used to obtain the results are accuracy, true positive rate (TPR) and false positive rate (FPR) where TPR and FPR are used for generating receiver operating characteristic curves.
Two‐dimensional DFT with sliding and hopping windows for edge map generation of road images
Authors: Vishwakarma Amit Kr. , Sukumar N. , Sumathi P.
Published: March 2021

An edge map generation technique based on two‐dimensional discrete Fourier transform with sliding and hopping windows is proposed for road images to detect the lanes and road markings. A 2 2 sliding/hopping window DFT with bin indices () for horizontal edge detection and () for vertical edge detection has been proposed. The 2‐D SDFT/HDFT‐based edge detector has been proved to be more efficient for lane and road marking images in comparison with conventional edge detectors and cellular neural network based edge detectors. In the presence of noise and various signal to noise ratio conditions, the horizontal and vertical edges have been efficiently recovered with good Pratt figure of merit without applying any pre‐processing, noise removal process, and post processing techniques. The PFOM was found to be quite stable with wide threshold range for various noise levels. The consistent performance of the proposed edge detector is proved with MSE and PSNR determination of detected edge images. Moreover, the proposed 2‐D SDFT/HDFT‐based edge detector performs well in developing edge maps for real‐time road videos. The system‐on‐chip implementation of the 2‐D SDFT/HDFT edge detector on Cyclone IV FPGA chip is also carried out for detecting the lane and road markings.
Impact of adding activated bentonite to thermally aged ester‐based TiO2 nanofluids on insulation performance
Authors: Amalanathan A. J. , Harid N. , Griffiths H. , Sarathi R.
Published: March 2021

The authors report the key findings from an experimental study that explored the use of activated bentonite for the reclamation of thermally aged ester‐based transformer nanofluids to improve their insulation performance. Bentonite activated with acid treatment caused an increase in the specific surface area and pore volume of bentonite compared to the bentonite sample before treatment, thus imparting an improved adsorption capability. Physico‐chemical diagnostic studies were carried out to characterise the activated bentonite. The insulation performance of the reclaimed natural ester and nano‐filled ester fluid samples was assessed by measuring the corona inception voltage and breakdown voltage of each fluid sample, apart form measuring the flow electrification current using the spinning disk method. The results revealed that the reclamation process improved the corona inception voltage, dissipation factor and the breakdown voltage of the base ester fluid sample due to attraction of carbon particles to activated bentonite, but no significant variation was observed with nanofluids due to the depletion of the electrical double layer. The flow electrification current of ester and ester nanofluids reduced after treatment with activated bentonite, may be attributed to the interaction between copper and bentonite that alters the double layer formation responsible for the separation of charges.
A survey of IRAS young stellar object candidates
Authors: López Rosario , Riera Angels , Estalella Robert , Gómez Gabriel
Published: March 2021

Context. Jets and outflows are associated with young stellar objects across the stellar mass spectrum, from brown dwarf protostars to massive Ae/Be stars. Frequently the jet morphology is spatially discontinuous because of the temporal variability of the ejection from the driving source. Images covering a wide field of view around the jet-driving source are useful to map the large-scale jet emission and to explore the mass ejection history.

Aims. The aim of our work was to search for large-scale optical Herbig-Haro (HH) objects lying in a wide field around a sample of IRAS sources, which are candidates to trace young stellar objects.

Methods. Deep narrowband images through the Hα and [S II] emission lines, and through an off-line continuum filter, covering a wide (~15′) field around the IRAS targets were acquired. The images in the three filters were analyzed to identify shock-excited line emission (i.e., HH) in contrast to scattered line emission.

Results. New images of a sample of 15 IRAS sources, obtained in a homogeneous way are presented. HH emission was detected in six fields, and the astrometry of the knot features is given. The nature of the extended emission as scattered emission around nine of the IRAS targets is confirmed. For seven IRAS sources with unclear optical counterparts, a more plausible counterpart is proposed. A refined value of the source distance is reported for seven targets. An update of the main data available for each of the sampled fields, including images from public data archives, is also presented.
Effects of molecule force on free vibration for a micro electromagnetic harmonic drive system
Authors: Zhao Dan , Xu Lizhong , Fu Yuming
Published: March 2021

In this paper, a micro electromagnetic harmonic drive system is proposed. Considering Van der Waals force, dynamics equation of the flexible ring for the micro drive system is deduced and resolved. Using the equations, the effects of the molecule force on the natural frequencies and vibration modes of the drive system are investigated. Results show that considering molecule force, natural frequencies of the flexible ring are reduced and its vibration modes are changed. For lower order modes, smaller clearance between the flexible ring and stator, smaller thickness of the flexible ring and larger radius of the flexible ring, the effects of the molecule force on the natural frequencies and vibration modes are more obvious.
The linguistic landscape of the coronavirus crisis in foreign language didactics by using the example of German
Authors: Kuße Holger
Published: March 2021

The coronavirus crisis has changed not only the practice of language teaching in higher education, but also the languages themselves; the crisis is strongly reflected in language. This can be seen in neologisms, new word formations and in the linguistic landscape in general. All these phenomena should be creatively included in foreign language didactics. Using examples from German the paper deals with several tasks and exercises concerning the language of the corona crises, i.e. word formation, word play, forms of politeness and the communication of values.
Case-based teaching research of media management course
Authors: Zhang Yan , Li Heping
Published: March 2021

The Harvard case has made a profound contribution to business education around the world. The course of Media Management is about business. In order to improve its teaching efficiency, Media Management adopted case-based teaching, and integrates the question and answer teaching and the story teaching in the case-based teaching. It conducted a full course description in advance in the first two weeks of the term, introduced core concepts of media management, and then assigned research tasks for Chinese and foreign media enterprises. In the mid-stage, background,factual knowledge and conceptual knowledge were explained, related stories were integrated and case teaching and question-and-answer teaching were used to make the classroom more interesting and practical. In the mid-stage, We conducted comparative teaching for two majors, each of which has two parallel classes, One is in the presence of case-based teaching, and the other is in the traditional teaching. Results showed that case-based teaching could significantly improve students’ academic performance. And the results also demonstrated that traditional teaching could improve students’ academic performance moderately. Students in group shared their research reports at the end of the term. Students’ group research report also enriched teachers' follow-up teaching resources.
Cognitive dialogue as a factor of enhancing the quality of education in the conditions of international cooperation in the sphere of higher education
Authors: Mukhametzyanova Larisa
Published: March 2021

The relevance of the article is caused due to the need to define the role of a cognitive paradigm for enhancing the quality of higher education in the conditions of international cooperation contributing to the development of the subjects’ of educational process possessing the human-forming, semantic priorities. The purpose of article is to reveal the human-forming individual reserves and mechanisms of cognitive dialogue between the teacher and the students on the basis of social-cognitive approach as the theoretical-methodological strategy determining and developing humanistic semantic formations and personality’s value transformations. The article reveals the principles of social-cognitive approach: human-conformity and harmonious proportionality, and the rules for their realization; cognitive instruments of democratization and humanization of education are described on the basis of cognitive dialogue between the teacher and the students as an informative exchange of rational and emotional information. The author defines the importance of emotional intelligence as a link between development of humanistic meanings, value understanding, understanding and regulation of the subjects’ of education cognition and emotions in cognitive dialogue affecting success of their socio-cultural interaction. The developmental stages of dialogical self-knowledge in the course of cognitive dialogue are defined in the integral unity of logical and emotional, and value coordinates based on the material of art works. The article is intended for University-teachers and researchers in the field of international cooperation in the sphere of education.
Current Approaches to Teaching Reading
Authors: Sofronova Irina
Published: March 2021

The paper considers reading for comprehension and developing reading culture, showing how reading habits are constantly changing with new technologies dominating our life. Learning English being the focus of attention, the author comments on the way reading contributes to language acquisition and language learning. А particular reference is given to types of reading, reading for comprehension being the essence of any. The author reviews reading strategies, stressing the necessity of introducing them to the students. The author analyses some of the language courses and gives examples of work on reading skills at the lessons of English using both the above courses and the ones developed by the teachers of the Ural State University of Economics.
Educators’ and students’ perceptions of online distance education before and amid COVID-19: Key concerns and challenges
Authors: Markova Tatiana
Published: March 2021

This paper aims to present Russian educators’ and students’ perceptions of online education before and during the pandemic. The author analyses the primary research data collected by the team of USUE authors via quantitate research methods, and secondary research data. Based on the empirical sociological data the author identifies the key challenges facing educators’ community – negative attitudes to online teaching and learning, lack of digital pedagogy skills and ineffective interaction practices. It is concluded that in the emergency situation teachers overall managed to fit rapid curriculum transformations. Yet, university leadership and educators should come up with solutions how to address the identified challenges in online distance teaching. These solutions can involve conducting in-depth research into digital pedagogy, disseminating knowledge about the specifics of online interactions and running professional development programs for the university teachers to enhance their performance in courses delivered online.
Linguistic Education and Economics: Way to Synergy
Authors: Zolotareva Natalia
Published: March 2021

The article is devoted to the problem of integrating linguistic studies into education for potential economists. This article aims to mark some important problematical items necessary to realize the reformation of higher philological education and to formulate a number of key statements that could help in future.it deals with the problem of understanding interdisciplinary as a popular important direction in higher education in universities of Russia.
MBA programs and their perspectives on the regional level in Russian Federation
Authors: Stikhina Irina
Published: March 2021

This article considers the availability of business schools and MBA programs on the Russian educational market and, in particular, in one of the federal subjects of Russian Federation, Sverdlovsk oblast. The market of MBA programs is reviewed on federal and regional levels and possible further way of development is suggested. In order to reach this goal, the ratings of business schools in Russia, information about them are analyzed and the general trends are defined. The survey confirms the lack of regional MBA programs on the market. Possible advantages of the availability and perspectives of programs with the regional focus are described. Partnerships between regional universities of economics and recognized foreign business schools are presented as the option for further development of MBA programs on the regional level. The Ural State University of Economics is given as an example.
Socio-psychological problems of the transition of university teachers to distance employment during the Covid19 pandemic
Authors: Pesha Anastasiya , Kamarova Tatyana
Published: March 2021

The challenges of higher education that the world faced during the pandemic led to an emergency temporary transfer of faculty to a distance learning format. The article reveals the results of the analysis of socio-psychological problems that university teachers faced during the transition to remote employment. The work is based on a content analysis of previous studies of the issue, as well as data from a formalized online survey of faculty members of universities. The formalized survey was attended by 169 representatives of the teaching staff of universities in 10 cities of Russia. The article presents the main opportunities and disadvantages of remote employment and distance learning in higher education from the point of view of teachers. As a result of the study, the authors formulated the key opportunities and disadvantages of distance employment and identified the key social and psychological problems that require attention when organizing the activities of teachers. The labor market is changing, the requirements for the competencies of university professors are changing, it is necessary to systematically, strategically introduce changes by the administration when switching to a remote work format with a focus on the social and psychological well-being of employees.
Iridium(III)-Catalyzed C−H Functionalization of Triarylphosphine Oxides with Diazo Dicarbonyl Compounds: Synthesis of α-Aryl 1,3-Dicarbonyl Derivatives
Authors: Yang Shang-Dong , Lou Qin-Xin , Li Jing-Yu
Published: March 2021

A novel (pentamethylcyclopenta-1,3-dienyl)iridium(III)-catalyzed direct C–H functionalization of triarylphosphine oxides with diazo dicarbonyl compounds through carbene insertion has been developed. This strategy provides a simple and efficient route to the construction of α-arylated 1,3-dicarbonyl compounds, which are important building blocks in pharmaceutical chemistry.
What is robotics made of? The interdisciplinary politics of robotics research
Authors: Michalec Ola , O’Donovan Cian , Sobhani Mehdi
Published: March 2021

Under framings of grand challenges, robotics has been proposed as a solution to a wide range of societal issues such as road safety, ageing society, economic productivity and climate change. However, what exactly is robotics research? From its inception, robotics has been an inherently interdisciplinary field, bringing together diverse domains such as engineering, cognitive science, computer science and, more recently, knowledge from social sciences and humanities. Previous research on interdisciplinarity shows that this mode of knowledge production is often driven by societal concerns and political choices. The politics of who gets to make these choices and on what terms is the focus of empirical research in this paper. Using a novel mixed-method approach combining bibliometrics, desk-based analysis and fieldwork, this article builds a narrative of interdisciplinarity at the UK’s largest public robotics lab, the Bristol Robotics Laboratory. This paper argues for the recognition of the plural ways of knowing interdisciplinarity. From citation analysis, through tracing of the emerging fields and disciplines, to, finally, the investigation of researchers’ experiences; each method contributes a distinct and complementary outlook on “what robotics is made of”. While bibliometrics allows visualising prominent disciplines and keywords, document analysis reveals influential and missing stakeholders. Meanwhile, fieldwork explores the logics underpinning robotics and identifies the capabilities necessary to perform the research. In doing so, the paper synthesises plural ways of locating politics in interdisciplinary research and provides recommendations for enabling “structural preparedness for interdisciplinarity”.
Predicting organizational performance from motivation in Oromia Seed Enterprise Bale branch
Authors: Jobira Askalech Feyisa , Mohammed Abdulnasir Abdulmelike
Published: March 2021

Motivation is one of the most researched yet crucial topics in academia from various perspectives. Despite this, researches show mixed results about the effect of extrinsic motivation on intrinsic motivation and organizational performance. Studies in Ethiopia also lack causal analysis and theoretical underpinning that made contributions from academia very little. Hence, this research is important to assess the effect of extrinsic motivation on intrinsic motivation and organizational performance from a cognitive evaluation theory perspective. The researchers adopted an explanatory research design with a quantitative approach. The entire 119 employees of the Oromia Seed Enterprise, Bale branch were included in the study to collect primary data through a close-ended questionnaire. The collected data was processed by SPSS software version 20. The relationship analysis was addressed by correlation and binary logistic regression analysis. Seen from extrinsic and intrinsic motivation aspects, the findings of the study showed that Oromia Seed Enterprise had a moderate level of organizational performance and a moderate level of employees’ motivation. The correlation analysis result indicated that employees’ extrinsic and intrinsic motivation had a positive relationship with organizational performance. The binary logistic regression analysis also indicated that extrinsic and intrinsic motivation had a positive and significant influence on organizational performance. However, the interaction effect of intrinsic and extrinsic motivation on organizational performance was not significant, implying the absence of influence when both intrinsic and extrinsic motivations happen at the same time. Finally, the study results have a theoretical contribution for compensating the lack of actual experience in the Ethiopian organization’s context. Equally, the understanding of the moderated relationship among the study variables may encourage Oromia Seed Enterprise and its managers to develop a practical motivation system, which entertains the complex interaction of motivation variables to improve organizational performance. In addition, studies of this nature can inform policymakers to strengthen an incentive system as well as other motivation veins in the Ethiopian public organizations.
Sound energy harvesting by leveraging a 3D-printed phononic crystal lens
Authors: Allam Ahmed , Sabra Karim , Erturk Alper
Published: March 2021

We investigate the harvesting of sound waves by exploiting a 3D-printed gradient-index phononic crystal lens. The concept is demonstrated numerically and experimentally for focusing audio frequency range acoustic waves in air to enhance sound energy harvesting. A finite-element model is developed to design the unit cell dispersion properties and to construct the 3D lens for wave field simulations. Numerical simulations are presented to confirm the focusing of incident plane waves and to study the sensitivity of the refractive index profile to the direction of wave propagation. The theoretical predictions are validated experimentally using a scanning microphone setup under speaker excitation, and a very good agreement is observed between the experimental and numerical wave fields. A circular piezoelectric unimorph harvester is placed at the focal position of the lens, and its performance is characterized with a resistor sweep in the absence and presence of the lens, resulting in more than an order of magnitude enhancement in the harvested power with the lens. The 3D-printed lens presented here substantially enhances the intensity of sound energy via focusing, yielding micro-Watt level power output, which can find applications for wireless sensors and other low-power electronic components.
Near-field modulation of single photon emitter with a plasmonic probe
Authors: Wu Yunkun , Liu Xiaojing , Qi Xiaozhuo , Lu Liu , Guo Guoping , Guo Guangcan , Ren Xifeng
Published: March 2021

Single solid-state quantum dots have significant potential as bright single-photon sources for scalable photonic quantum information technologies. Engineering their radiative relaxation properties is of significant importance for their practical applications. In this study, we demonstrate a cavity-free, broadband approach for modulating and collecting the fluorescence of a single-photon emitter using a fiber taper–silver nanowire plasmonic probe. When the plasmonic probe is located above a single colloidal quantum dot at approximately 20 nm, the photon-emitter interaction increased rapidly and a significant decrease, by an average factor of 3.38, in the lifetime of the quantum dot was observed. The fluorescence signal of the quantum dots was collected by the hybrid probe, with significantly higher efficiency than that of the traditional metal-coated near-field probe. The results of the numerical simulation were in good agreement with the experimental results. The proposed near-field modulation method can be applied to other single-photon sources and proved to be a flexible method for manipulating the luminescence of systems based on single-photon emitters.
Effect of surface temperature on quantum dynamics of H2 on Cu(111) using a chemically accurate potential energy surface
Authors: Dutta Joy , Mandal Souvik , Adhikari Satrajit , Spiering Paul , Meyer Jörg , Somers Mark F.
Published: March 2021

The effect of surface atom vibrations on H2 scattering from a Cu(111) surface at different temperatures is being investigated for hydrogen molecules in their rovibrational ground state (v = 0, j = 0). We assume weakly correlated interactions between molecular degrees of freedom and surface modes through a Hartree product type wavefunction. While constructing the six-dimensional effective Hamiltonian, we employ (a) a chemically accurate potential energy surface according to the static corrugation model [M. Wijzenbroek and M. F. Somers, J. Chem. Phys. 137, 054703 (2012)]; (b) normal mode frequencies and displacement vectors calculated with different surface atom interaction potentials within a cluster approximation; and (c) initial state distributions for the vibrational modes according to Bose–Einstein probability factors. We carry out 6D quantum dynamics with the so-constructed effective Hamiltonian and analyze sticking and state-to-state scattering probabilities. The surface atom vibrations affect the chemisorption dynamics. The results show physically meaningful trends for both reaction and scattering probabilities compared to experimental and other theoretical results.
Analytic theory for field emission driven microscale gas breakdown for a pin-to-plate geometry
Authors: Loveless Amanda M. , Breen Lorin I. , Garner Allen L.
Published: March 2021

Decreasing electronics size necessitates better characterization of electron emission at the micro- and nanoscales for applications including microplasmas, micro- and nanoelectromechanical systems, and directed energy. While Paschen's law (PL) has historically predicted breakdown voltage based on the Townsend avalanche, field emission must be incorporated for gap sizes below ∼15 μm. Extensive studies have modified PL to explicitly include field emission for planar geometries; however, many practical experiments use pin-to-plate geometries. We modify a previous theory coupling PL and field emission to account for pin-to-plate geometries by replacing the field enhancement factor, which has been used primarily as a fitting parameter, with the appropriate vacuum electric field. This requires explicitly accounting for the spatial dependence of ionization and non-uniform space charge in Poisson's equation. We derive a breakdown equation of the form previously obtained for planar geometry [Venkattraman and Alexeenko, Phys. Plasmas 19, 123515 (2012)] that agrees well with experimental data with the work function as the fitting parameter. The work function was consistently lower (∼2 eV) than anticipated (∼4.5 eV) but was generally fairly consistent (∼ ± 7%). We then derived closed form solutions in the limit of low ionization, corresponding to the field emission regime, and recovered an analytic solution for a parallel plate geometry in the limit of small gap distance that differed from prior analytic results because of the explicit consideration of spatial dependence in charge density. This theory may ultimately be applied to other nonplanar geometries by applying the appropriate equation for the vacuum electric field.
Origin of large magnetostriction in palladium cobalt and palladium nickel alloys: Strong pseudo-dipole interactions between palladium–cobalt and palladium–nickel atomic pairs
Authors: Harumoto Takashi , Shi Ji , Nakamura Yoshio , Takahashi Akira
Published: March 2021

The origin of the large magnetostriction in palladium cobalt and palladium nickel alloys was investigated. Density functional theory calculations based on the Korringa–Kohn–Rostoker Green function method with the coherent potential approximation revealed that alloying with palladium results in increased magnetization of cobalt and nickel atoms. Also, anomalous magnetization of palladium atoms occurs simultaneously. Employing calculated spin and orbital angular momenta of the atoms, magnetostriction was discussed based on the two-spin model for disordered alloys. Under the assumption that the pseudo-dipole interaction is proportional to the orbital and total angular momenta, the experimental magnetostriction curves can be reproduced. The estimated contributions of each atomic pair to magnetostriction revealed that the large magnetostriction at the palladium-rich side originates from the strong pseudo-dipole interactions between 4d and 3d transition metal atoms, namely, palladium–cobalt and palladium–nickel atomic pairs.
Quantifying the effect of extensional rheology on the retention of agricultural sprays
Authors: Xu Minghuan , Li Xiran , Riseman Andrew , Frostad John M.
Published: March 2021

In pesticide and fertilizer applications, retention of spray droplets after they reach the target surface can be limited by droplets splashing, rebounding, or rolling off of the surface. In this study, a novel approach is presented for quantifying the retention efficiency. This approach enables testing of the influence of polymer additives for enhancing the retention efficiency of both real and model agricultural sprays. The results demonstrate that increasing the extensional rheology of the spray solution can increase the retention efficiency by up to 20% and in some cases achieve a total efficiency greater than 95%. The results are consistent on both synthetic surfaces and plant surfaces and suggest that for a particular polymer and surface, the extensional relaxation time alone is sufficient to predict the retention efficiency.
Factors correlating to enhanced surface diffusion in metallic glasses
Authors: Annamareddy Ajay , Li Yuhui , Yu Lian , Voyles Paul M. , Morgan Dane
Published: March 2021

The enhancement of surface diffusion (DS) over the bulk (DV) in metallic glasses (MGs) is well documented and likely to strongly influence the properties of glasses grown by vapor deposition. Here, we use classical molecular dynamics (MD) simulations to identify different factors influencing the enhancement of surface diffusion in MGs. MGs have a simple atomic structure and belong to the category of moderately fragile glasses that undergo pronounced slowdown of bulk dynamics with cooling close to the glass transition temperature (Tg). We observe that DS exhibits a much more moderate slowdown compared to DV when approaching Tg, and DS/DV at Tg varies by two orders of magnitude among the MGs investigated. We demonstrate that both the surface energy and the fraction of missing bonds for surface atoms show good correlation to DS/DV, implying that the loss of nearest neighbors at the surface directly translates into higher mobility, unlike the behavior of network-bonded and hydrogen-bonded organic glasses. Fragility, a measure of the slowdown of bulk dynamics close to Tg, also correlates to DS/DV, with more fragile systems having larger surface enhancement of mobility. The deviations observed in the fragility–DS/DV relationship are shown to be correlated to the extent of segregation or depletion of the mobile element at the surface. Finally, we explore the relationship between the diffusion pre-exponential factor (D0) and the activation energy (Q) and compare it to a ln(D0)–Q correlation previously established for bulk glasses, demonstrating similar correlations from MD as in the experiments and that the surface and bulk have very similar ln(D0)–Q correlations.
THz intersubband electroluminescence from n-type Ge/SiGe quantum cascade structures
Authors: Stark David , Mirza Muhammad , Persichetti Luca , Montanari Michele , Markmann Sergej , Beck Mattias , Grange Thomas , Birner Stefan , Virgilio Michele , Ciano Chiara , Ortolani Michele , Corley Cedric , Capellini Giovanni , Di Gaspare Luciana , De Seta Monica , Paul Douglas J. , Faist Jérôme , Scalari Giacomo
Published: March 2021

We report electroluminescence originating from L-valley transitions in n-type Ge/Si0.15Ge0.85 quantum cascade structures centered at 3.4 and 4.9 THz with a line broadening of Δf/f≈0.2. Three strain-compensated heterostructures, grown on a Si substrate by ultrahigh vacuum chemical vapor deposition, have been investigated. The design is based on a single quantum well active region employing a vertical optical transition, and the observed spectral features are well described by non-equilibrium Green's function calculations. The presence of two peaks highlights a suboptimal injection in the upper state of the radiative transition. Comparison of the electroluminescence spectra with a similar GaAs/AlGaAs structure yields one order of magnitude lower emission efficiency.
Analytical derivatives of the individual state energies in ensemble density functional theory. II. Implementation on graphical processing units (GPUs)
Authors: Liu Fang , Filatov Michael , Martínez Todd J.
Published: March 2021

Conical intersections control excited state reactivity, and thus, elucidating and predicting their geometric and energetic characteristics are crucial for understanding photochemistry. Locating these intersections requires accurate and efficient electronic structure methods. Unfortunately, the most accurate methods (e.g., multireference perturbation theories such as XMS-CASPT2) are computationally challenging for large molecules. The state-interaction state-averaged restricted ensemble referenced Kohn–Sham (SI-SA-REKS) method is a computationally efficient alternative. The application of SI-SA-REKS to photochemistry was previously hampered by a lack of analytical nuclear gradients and nonadiabatic coupling matrix elements. We have recently derived analytical energy derivatives for the SI-SA-REKS method and implemented the method effectively on graphical processing units. We demonstrate that our implementation gives the correct conical intersection topography and energetics for several examples. Furthermore, our implementation of SI-SA-REKS is computationally efficient, with observed sub-quadratic scaling as a function of molecular size. This demonstrates the promise of SI-SA-REKS for excited state dynamics of large molecular systems.
Associated molecular liquids at the graphene monolayer interface
Authors: Goujon Florent , Ghoufi Aziz , Malfreyt Patrice
Published: March 2021

We report molecular simulations of the interaction between a graphene sheet and different liquids such as water, ethanol, and ethylene glycol. We describe the structural arrangements at the graphene interface in terms of density profiles, number of hydrogen bonds (HBs), and local structuration in neighboring layers close to the surface. We establish the formation of a two-dimensional HB network in the layer closest to the graphene. We also calculate the interfacial tension of liquids with a graphene monolayer and its profile along the direction normal to the graphene to rationalize and quantify the strengthening of the intermolecular interactions in the liquid due to the presence of the surface.
Temporal multilayer structures for designing higher-order transfer functions using time-varying metamaterials
Authors: Ramaccia D. , Alù A. , Toscano A. , Bilotti F.
Published: March 2021

Temporal metamaterials are artificial materials whose electromagnetic properties change over time. In analogy with spatial media and metamaterials, where their properties change smoothly or abruptly over space, temporal metamaterials can exhibit a smooth variation over time, realizing a temporal non-homogeneous medium, or a stepwise transition, and the temporal version of dielectric slabs or multilayer structures. In this Letter, we focus our attention on temporal multilayer structures, and we propose the synthesis of higher-order transfer functions by modeling the wave propagation through a generalized temporal multilayer structure, consisting of a cascade over time of different media. The tailoring of the scattering response of the temporal structure as a function of frequency is presented, deriving the corresponding scattering coefficients for a properly designed set of medium properties, i.e., permittivity and permeability, and application time, in analogy with what is typically done in optical and electromagnetic spatial multilayered structures. This allows us to design novel electromagnetic and optical devices with higher-order transfer functions by exploiting the temporal dimension instead of the spatial one.
Robustness improvement for cyber physical system based on an optimization model of interdependent constraints
Authors: Tu Haicheng , Xia Yongxiang , Zhang Xi , Shen Hui-liang
Published: March 2021

With the rapid development of information technology, traditional infrastructure networks have evolved into cyber physical systems (CPSs). However, this evolution has brought along with it cyber failures, in addition to physical failures, which can affect the safe and stable operation of the whole system. In light of this, in this paper, we propose an interdependence-constrained optimization model to improve the robustness of the cyber physical system. The proposed model includes not only the realistic physical law but also the interdependence between the physical network and the cyber network. However, this model is highly nonlinear and cannot be solved directly. Therefore, we transform the model into a bi-level mixed integer linear programming problem, which can be easily and effectively solved in polynomial time. We conduct the simulation based on standard Institute of Electrical and Electronics Engineers test cases and study the impact of the disaster level and coupling strength on the robustness of the whole system. The simulation results show that our proposed model can effectively improve the robustness of the cyber physical system. Moreover, we compare the performance of the power supply in different CPSs, which have different network structures of the cyber network. Our work can provide useful instructions for system operators to improve the robustness of CPSs after extreme events happen in them.