bluuebunny/crossref_metadata_2025_split huggingface dataset:
Emergent transition from face-to-face to online learning in a South African University in the context of the Coronavirus pandemic
Authors: Mpungose Cedric B. 
Published: October 2020

AbstractSouth African universities have been forced to transit from face-to-face to online learning (e-learning) as a result of the coronavirus pandemic (COVID-19). However, various challenges hinder disadvantaged students from realising the full potential of e-learning. Therefore, this study’s main objective is to propose alternative pathways to overcome such challenges for students, to enable them to have access to effective e-learning. This study draws on a two-year postdoctoral qualitative research project conducted at a South African university to explore students’ experiences of the transition from face-to-face to e-learning. Twenty-six students completing a curriculum studies programme were purposively and conveniently sampled to generate data using e-reflective activity, Zoom group meetings and a WhatsApp one-on-one semi-structured interview. Findings articulate the digital divide as a hindrance to students realising the full potential of e-learning, yet lecturers still want students to submit assessment tasks and engage with course activities on the Moodle learning management system. With universities using face-to-face learning becoming vulnerable to the COVID-19 pandemic and other challenges which result in a shutdown of university sites, alternatives need to be sought to allow students, particularly disadvantaged students, to realise e-learning.
Alkyl complexes of divalent lanthanides and heavy alkaline earth metals
Authors: Khristolyubov Dmitry O. , Lyubov Dmitry M. , Trifonov Alexander A. 
Published: October 2020

The review presents data on the synthesis, structure, reactivity, and catalytic activity of alkyl derivatives of rare earth metals in the oxidation state +2 (Sm, Eu, Yb) and their analogues containing heavy alkaline earth metals (Ca, Sr, Ba). The synthetic aspects and structural features of this unique class of organometallic compounds, which contain highly reactive M–C bonds, including alkyl, α-silylmethyl, and also benzyl, diphenylmethyl, and triphenylmethyl derivatives are considered.
The bibliography includes 157 references.
Path identity as a source of high-dimensional entanglement
Authors: Kysela Jaroslav , Erhard Manuel , Hochrainer Armin , Krenn Mario , Zeilinger Anton 
Published: October 2020

Significance
Quantum entanglement amounts to an extremely strong link between two distant particles, a link so strong that it eludes any classical description and so unsettling that Albert Einstein described it as “spooky action at a distance.” Today, entanglement is not only a subject of fundamental research, but also a workhorse of emerging quantum technologies. In our current work we experimentally demonstrate a completely different method of entanglement generation. Unlike many traditional methods, where entanglement arises due to conservation of a physical quantity, such as momentum, in our method it is rather a consequence of indistinguishability of several particle-generating processes. This approach, where each process effectively adds one dimension to the entangled state, allows for a high degree of customizability.
Classification of stroke using neural networks in electrical impedance tomography
Authors: Agnelli J P , Çöl A , Lassas M , Murthy R , Santacesaria M , Siltanen S 
Published: October 2020

Abstract
Electrical impedance tomography (EIT) is an emerging non-invasive medical imaging modality. It is based on feeding electrical currents into the patient, measuring the resulting voltages at the skin, and recovering the internal conductivity distribution. The mathematical task of EIT image reconstruction is a nonlinear and ill-posed inverse problem. Therefore any EIT image reconstruction method needs to be regularized, typically resulting in blurred images. One promising application is stroke-EIT, or classification of stroke into either ischemic or hemorrhagic. Ischemic stroke involves a blood clot, preventing blood flow to a part of the brain causing a low-conductivity region. Hemorrhagic stroke means bleeding in the brain causing a high-conductivity region. In both cases the symptoms are identical, so a cost-effective and portable classification device is needed. Typical EIT images are not optimal for stroke-EIT because of blurriness. This paper explores the possibilities of machine learning in improving the classification results. Two paradigms are compared: (a) learning from the EIT data, that is Dirichlet-to-Neumann maps and (b) extracting robust features from data and learning from them. The features of choice are virtual hybrid edge detection (VHED) functions (Greenleaf et al 2018 Anal. PDE
11) that have a geometric interpretation and whose computation from EIT data does not involve calculating a full image of the conductivity. We report the measures of accuracy, sensitivity and specificity of the networks trained with EIT data and VHED functions separately. Computational evidence based on simulated noisy EIT data suggests that the regularized grey-box paradigm (b) leads to significantly better classification results than the black-box paradigm (a).
Electron beam triggered single-atom dynamics in two-dimensional materials
Authors: Zhao Xiaoxu , Loh Kian Ping , Pennycook Stephen J 
Published: October 2020

Abstract
Controlling atomic structure and dynamics with single-atom precision is the ultimate goal in nanoscience and nanotechnology. Despite great successes being achieved by scanning tunneling microscopy (STM) over the past a few decades, fundamental limitations, such as ultralow temperature, and low throughput, significantly hinder the fabrication of a large array of atomically defined structures by STM. The advent of aberration correction in scanning transmission electron microscopy (STEM) revolutionized the field of nanomaterials characterization pushing the detection limit down to single-atom sensitivity. The sub-angstrom focused electron beam (e-beam) of STEM is capable of interacting with an individual atom, thereby it is the ideal platform to direct and control matter at the level of a single atom or a small cluster. In this article, we discuss the transfer of energy and momentum from the incident e-beam to atoms and their subsequent potential dynamics under different e-beam conditions in 2D materials, particularly transition metal dichalcogenides (TMDs). Next, we systematically discuss the e-beam triggered structural evolutions of atomic defects, line defects, grain boundaries, and stacking faults in a few representative 2D materials. Their formation mechanisms, kinetic paths, and practical applications are comprehensively discussed. We show that desired structural evolution or atom-by-atom assembly can be precisely manipulated by e-beam irradiation which could introduce intriguing functionalities to 2D materials. In particular, we highlight the recent progress on controlling single Si atom migration in real-time on monolayer graphene along an extended path with high throughput in automated STEM. These results unprecedentedly demonstrate that single-atom dynamics can be realized by an atomically focused e-beam. With the burgeoning of artificial intelligence and big data, we can expect that fully automated microscopes with real-time data analysis and feedback could readily design and fabricate large scale nanostructures with unique functionalities in the near future.
Importance of van der Waals interactions for ab initio studies of topological insulators
Authors: Shirali K , Shelton W A , Vekhter I 
Published: October 2020

Abstract
We investigate the lattice and electronic structures of the bulk and surface of the prototypical layered topological insulators Bi2Se3 and Bi2Te3 using ab initio density functional methods, and systematically compare the results of different methods of including van der Waals (vdW) interactions. We show that the methods utilizing semi-empirical energy corrections yield accurate descriptions of these materials, with the most precise results obtained by properly accounting for the long-range tail of the vdW interactions. The bulk lattice constants, distances between quintuple layers and the Dirac velocity of the topological surface states (TSS) are all in excellent agreement with experiment. In Bi2Te3, hexagonal warping of the energy dispersion leads to complex spin textures of the TSS at moderate energies, while in Bi2Se3 these states remain almost perfectly helical away from the Dirac point, showing appreciable signs of hexagonal warping at much higher energies, above the minimum of the bulk conduction band. Our results establish a framework for unified and systematic self-consistent first principles calculations of topological insulators in bulk, slab and interface geometries, and provides the necessary first step toward ab initio modeling of topological heterostructures.
Inverse problems in geomagnetism: the magnetic anomaly exploration game
Authors: Bastos Rodrigo Oliveira 
Published: October 2020

Abstract
Inspired by the inverse problems related to geomagnetism I propose an exploration game using simple devices to survey magnetic anomalies. The game, in its simplest form, has the objective to find the position and orientation of a single dipole inside a black box, based on measurements of field directions collected with a compass outside the box. The richness of the game resides partially in its set up simplicity and in the complexity that unfolds when dealing with inverse problems related to vector field analysis.
Extinguishment of hot cathode discharges by space-charge and surface magnetic effects
Authors: Yip Chi-Shung , Jin Chenyao , Zhang Wei , Xu Guo Sheng , Hershkowitz Noah , Severn Greg 
Published: October 2020

Abstract
Emission characteristics of a directly heated, rod-shaped LaB6 hot cathode has been studied in a multi-dipole confinement device. It is found that contrary to predictions from the conventional space-charge limited emission theory, emission current is not simply limited to a maximum value but eventually extinguished by space-charge related effects. In addition, directional preference of electron emission towards the positive lead of the applied heating voltage can be visibly observed. Results suggest that thermionically emitted electrons trapped in the virtual cathode are pumped towards the high voltage lead of the applied heating, and that the magnetic effects for filament heating currents exceeding 50 A may be the underlying mechanism of extinguishment; that is, the gyromotion of surface emitted electrons for sufficiently great heating currents may prevent electrons from escaping the virtual cathode. Geometrical effects are also briefly discussed.
Study of the origin of quasi-coherent modes in low-density KSTAR ECH plasmas
Authors: Lee Woochang , Lee Jaehyun , Lee Dong-Jae , Park Hyeon K. 
Published: October 2020

Abstract
Gradual or abrupt transitions from a coherent mode to quasi-coherent mode (QCM, a type of trapped electron mode turbulence) are observed in the core region of low-density plasmas in Korea Superconducting Tokamak Advanced Research. The coherent mode is initiated in the vicinity of the q = 1 surface by off-axis electron cyclotron resonant heating (ECH), and gradually or abruptly evolves into the QCM as the collisionality is slowly or rapidly increased through electron density control. When the collisionality further increases above a critical level, the QCM is changed into broadband turbulence, which has been preferentially observed in tokamak plasmas. The observed evolution of the QCMs suggests that (1) QCMs can originate from a coherent mode in ECH applied low-collisionality plasmas and (2) quasi-coherent spectra of QCMs are closely related with the collisionality in a finite range (‘collisional broadening of the wavenumber and frequency’). The coherent mode appears to be a metastable electrostatic mode at the rational surface excited by off-axis ECH.
Effects of symmetry breaking in the viscous pumping of an oscillating plate in the intermediate Reynolds numbers
Authors: Saffaraval Farhad , Goudarzi Navid 
Published: October 2020

Abstract
Pumping fluid is essential to numerous applications across a wide range of scales from viscous dominated to inertia driven flows. Most traditional applications occur within a range where inertia is the dominating factor influencing the pump performance, and hence many practical designs are based on mechanisms that rely on this assumption. As one explores smaller devices, however, the increasing effect of viscosity renders these traditional mechanisms ineffective. In the current work, a bio-inspired pump is constructed from a two-dimensional oscillating solid and flexible plate to study the effect of diminishing inertia within a narrow channel. The goal is to quantify and better understand the role played by a shift from symmetric to asymmetric kinematics of an oscillating rigid or flexible plate in the transition regime between viscous and inertia dominated flows. This is done through both a temporal asymmetry using a rigid plate (e.g. scallop) and a geometric asymmetry using a passive one-way hinged articulation (e.g. jellyfish). One-way flexibility results in a rigid plate during the effective stroke while permitting a simple hinged articulation during the recovery stroke. The waveform used for the temporally asymmetric case consists of a basic triangle waveform which could generate faster effective strokes than recovery strokes. The results of the single-plate tests indicate that increased asymmetry introduced in the triangular wave actuation leads to increased pumping performance and energy consumption. In the case of flexible plates, the results show that a mass-specific pumping efficiency was higher for a higher actuation frequency at the same Reynolds numbers.
Accelerated in vitro recellularization of decellularized porcine pericardium for cardiovascular grafts
Authors: Filova Elena , Steinerova Marie , Travnickova Martina , Knitlova Jarmila , Musilkova Jana , Eckhardt Adam , Hadraba Daniel , Matejka Roman , Prazak Simon , Stepanovska Jana , Kucerova Johanka , Riedel Tomáš , Brynda Eduard , Lodererova Alena , Honsova Eva , Pirk Jan , Konarik Miroslav , Bacakova Lucie 
Published: October 2020

Abstract
An ideal decellularized allogenic or xenogeneic cardiovascular graft should be capable of preventing thrombus formation after implantation. The antithrombogenicity of the graft is ensured by a confluent endothelial cell layer formed on its surface. Later repopulation and remodeling of the scaffold by the patient’s cells should result in the formation of living autologous tissue. In the work presented here, decellularized porcine pericardium scaffolds were modified by growing a fibrin mesh on the surface and inside the scaffolds, and by attaching heparin and human vascular endothelial growth factor (VEGF) to this mesh. Then the scaffolds were seeded with human adipose tissue-derived stem cells (ASCs). While the ASCs grew only on the surface of the decellularized pericardium, the fibrin-modified scaffolds were entirely repopulated in 28 d, and the scaffolds modified with fibrin, heparin and VEGF were already repopulated within 6 d. Label free mass spectrometry revealed fibronectin, collagens, and other extracellular matrix proteins produced by ASCs during recellularization. Thin layers of human umbilical endothelial cells were formed within 4 d after the cells were seeded on the surfaces of the scaffold, which had previously been seeded with ASCs. The results indicate that an artificial tissue prepared by in vitro recellularization and remodeling of decellularized non-autologous pericardium with autologous ASCs seems to be a promising candidate for cardiovascular grafts capable of accelerating in situ endothelialization. ASCs resemble the valve interstitial cells present in heart valves. An advantage of this approach is that ASCs can easily be collected from the patient by liposuction.
Shorter cyclone clusters modulate changes in European wintertime precipitation extremes
Authors: Bevacqua Emanuele , Zappa Giuseppe , Shepherd Theodore G 
Published: October 2020

Abstract
Wintertime extreme precipitation from cyclone clusters, i.e. consecutive cyclones moving across the same region, can lead to flooding and devastating socio-economic impacts in Europe. Previous studies have suggested that the future direction of the changes in these events are uncertain across climate models. By employing an impact-based metric of accumulated precipitation extremes, we show that projections of cyclone clusters are instead broadly robust, i.e. consistent in sign, across models. A novel physical diagnostic shows that accumulated precipitation extremes are projected to grow by only +1.0 %/K on average across Europe, although the mean precipitation per cyclone increases by +4.7 %/K. This results from a decreased number of clustered cyclones, associated with decreased wintertime storminess, the extent of which varies from northern to southern Europe and depends on the future storyline of atmospheric circulation change. Neglecting the changes in the number of clustered cyclones, i.e. assuming that accumulated precipitation extremes would change as the mean precipitation per cyclone, would lead to overestimating the population affected by increased accumulated wintertime precipitation extremes by 130–490 million across Europe.
Changes in building climate zones over China based on high-resolution regional climate projections
Authors: Shi Ying , Wang Guiling 
Published: October 2020

Abstract
Based on the up-to-date observations and five sets of high-resolution climate projections under RCP4.5 over East Asia using a regional climate model, this study defines building climate zones over China and assesses their past and future changes according to an established climate classification scheme. The five-model ensemble captures the observed general distribution of climate zones, with a distinct latitudinal pattern over the densely populated eastern China, a subarctic zone in the western mountains including the Tibetan Plateau and a cool dry zone in the Tarim and Turpan basins; large disparities are found in northwestern China due to warm and dry biases. Observational data identifies a recent northward shift of most climate zones in eastern China and a shrinking of the subarctic climate zones over the Tibetan Plateau, which caused a building climate zone change for 18% of the country’s land area. As the warming continues in the future, the five-model ensemble projects additional climate zone changes influencing 43% and 55% of the country by mid- and late-century, respectively. In addition, the total area of the subarctic zone is projected to decrease from 16.6% of the country in present-day climate to 9.2% and 7.4% in the mid- and late-century, respectively, and that of the hot or very-hot climate zone is projected to expand from 4.2% to 9.1% and 11.3%, respectively. These changes should be taken into consideration in long-term development planning related to urbanization, energy efficiency, and environmental sustainability.
Basis decompositions and a Mathematica package for modular graph forms
Authors: Gerken Jan E 
Published: October 2020

AbstractModular graph forms (MGFs) are a class of non-holomorphic modular forms which naturally appear in the low-energy expansion of closed-string genus-one amplitudes and have generated considerable interest from pure mathematicians. MGFs satisfy numerous non-trivial algebraic- and differential relations which have been studied extensively in the literature and lead to significant simplifications. In this paper, we systematically combine these relations to obtain basis decompositions of all two- and three-point MGFs of total modular weightw+w̄⩽12, starting from just two well-known identities for banana graphs. Furthermore, we study previously known relations in the integral representation of MGFs, leading to a new understanding of holomorphic subgraph reduction as Fay identities of Kronecker–Eisenstein series and opening the door toward decomposing divergent graphs. We provide a computer implementation for the manipulation of MGFs in the form of theMathematicapackageModularGraphFormswhich includes the basis decompositions obtained.
Communication Support Tool With Data Glove Concept For People With Hearing Disability Using Kansai Engineering Method
Authors: Syahriza  , Zuhri S , Adilah M 
Published: October 2020

Abstract
The difficulty of communication that faced by the deaf and mute people make them complicated in doing activity like normal people. Sign language as a communication tool that has been formed at this time has not yet been able to connect communication with the community yet. It is only able to bridge communication among those fellow deaf and mute people. Therefore a tool which is able to translate sign language used by people with disabilities is needed. Thetool which able to translate sign language wascreated by Data Glove concept in design which can translate the word visually. Using the assistance of the Semantic Differential questionnaire, we can get the emotion level from user based on 12 Kansei words. The response in emotion form which is expresssed by users is one of theelements of the Kansei Engineering Method. Thus product adjustment to Kansei engineering is advisable and society.
A Study of Place Attachment to Mosques as an Evacuation Shelter Building
Authors: Vivita L , Husaini  , Anggraini R , Dewi C 
Published: October 2020

Abstract
The city of Banda Aceh has a geological location that is prone to earthquakes and tsunamis. In 2004, the tsunami damaged the city structure, and many victims died. When the tsunami struck the area, a mosque was used as an evacuation building. Its scatter existence in residential areas made it easy to reach, but several mosques could not be used as an evacuation building. The purpose of this study was to explore the function of mosques as tsunami evacuation building through place attachment studies using qualitative methods and depth interviews to identify public attachment factors. To measure place attachment, this research used three variables, i.e. socio-demographic, environmental experience, and familiarity with the place. This study also used the space forming variables, which include meaning, function, and form to see the public attachment to a mosque as an evacuation shelter building. The results showed that place attachment to a mosque was influenced by its meaning as a sacred place. The majority of people in Banda Aceh are Muslim and have Islamic cultural backgrounds. People’s routine activities form strong bonds to a mosque. Acehnese culture to glorify guests is reflected in mosque building design by exploring open walls, ease of accessibility, and spread presence in residential areas. These cultural characteristics strengthen the opportunity to make mosques as tsunami evacuation shelter buildings in Banda Aceh.