bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystal Structure of Nitrilase-Like Protein Nit2 from Kluyveromyces lactis
Authors: Jin Chaewon , Jin Hyeonseok , Jeong Byung-Cheon , Cho Dong-Hyung , Chun Hang-Suk , Kim Woo-Keun , Chang Jeong Ho
Published: May 2021

The nitrilase superfamily, including 13 branches, plays various biological functions in signaling molecule synthesis, vitamin metabolism, small-molecule detoxification, and posttranslational modifications. Most of the mammals and yeasts have Nit1 and Nit2 proteins, which belong to the nitrilase-like (Nit) branch of the nitrilase superfamily. Recent studies have suggested that Nit1 is a metabolite repair enzyme, whereas Nit2 shows ω-amidase activity. In addition, Nit1 and Nit2 are suggested as putative tumor suppressors through different ways in mammals. Yeast Nit2 (yNit2) is a homolog of mouse Nit1 based on similarity in sequence. To understand its specific structural features, we determined the crystal structure of Nit2 from Kluyveromyces lactis (KlNit2) at 2.2 Å resolution and compared it with the structure of yeast-, worm-, and mouse-derived Nit2 proteins. Based on our structural analysis, we identified five distinguishable structural features from 28 structural homologs. This study might potentially provide insights into the structural relationships of a broad spectrum of nitrilases.
Crystal Growth of the Quasi-2D Quarternary Compound AgCrP2S6 by Chemical Vapor Transport
Authors: Selter Sebastian , Shemerliuk Yuliia , Büchner Bernd , Aswartham Saicharan
Published: May 2021

We report optimized crystal growth conditions for the quarternary compound AgCrP2S6 by chemical vapor transport. Compositional and structural characterization of the obtained crystals were carried out by means of energy-dispersive X-ray spectroscopy and powder X-ray diffraction. AgCrP2S6 is structurally closely related to the M2P2S6 family, which contains several compounds that are under investigation as 2D magnets. As-grown crystals exhibit a plate-like, layered morphology as well as a hexagonal habitus. AgCrP2S6 crystallizes in monoclinic symmetry in the space group P2/a (No. 13). The successful growth of large high-quality single crystals paves the way for further investigations of low dimensional magnetism and its anisotropies in the future and may further allow for the manufacturing of few-layer (or even monolayer) samples by exfoliation.
Unveiling the Defect Structure of Lithium Niobate with Nuclear Methods
Authors: Kling Andreas , Marques José G.
Published: May 2021

X-ray and neutron diffraction studies succeeded in the 1960s to determine the principal structural properties of congruent lithium niobate. However, the nature of the intrinsic defects related to the non-stoichiometry of this material remained an object of controversial discussion. In addition, the incorporation mechanism for dopants in the crystal lattice, showing a solubility range from about 0.1 mol% for rare earths to 9 mol% for some elements (e.g., Ti and Mg), stayed unresolved. Various different models for the formation of these defect structures were developed and required experimental verification. In this paper, we review the outstanding role of nuclear physics based methods in the process of unveiling the kind of intrinsic defects formed in congruent lithium niobate and the rules governing the incorporation of dopants. Complementary results in the isostructural compound lithium tantalate are reviewed for the case of the ferroelectric-paraelectric phase transition. We focus especially on the use of ion beam analysis under channeling conditions for the direct determination of dopant lattice sites and intrinsic defects and on Perturbed Angular Correlation measurements probing the local environment of dopants in the host lattice yielding independent and complementary information.
Optical Spectroscopy of Li6Y(BO3)3 Single Crystals Doped with Dysprosium
Authors: Tichy-Rács Éva , Romet Ivo , Kovács László , Lengyel Krisztián , Corradi Gábor , Nagirnyi Vitali
Published: May 2021

The energy levels of Dy3+ ions have been determined in lithium yttrium borate (Li6Y(BO3)3) single crystals in a wide spectral range between 3000 and 40,000 cm−1 using optical absorption and luminescence spectroscopy, which also allow for an analysis of the ground state. The crystal field splittings of the 6H15/2 ground state and all excited states up to the 4F7/2 manifold were obtained at a low temperature, based on luminescence (T = 4.2–78 K) and absorption (T = 8–100 K) measurements, respectively. The numbers of experimentally observed Stark sublevels are in agreement with those expected theoretically for Dy3+ ions occupying a single low symmetry (C1) site.
Determination of the Exact Orientation of Single-Crystal X-ray Optics from Its Glitch Spectrum and Modeling of Glitches for an Arbitrary Configuration
Authors: Klimova Nataliya , Yefanov Oleksandr , Snigireva Irina , Snigirev Anatoly
Published: May 2021

X-ray optics made of single-crystal materials are widely used at most of the X-ray sources due to the outstanding properties. The main drawback of such optics—the diffraction losses, also known as glitches of intensity in the energy spectrum of the transmitted/diffracted beam. To be able to handle this negative effect, one needs a reliable way to simulate the glitch spectrum in any configuration. Here, we demonstrate the way of precisely determining the crystallographic orientation and unit cell parameters of optical elements just from a small glitch spectrum with the consequent possibility of simulating glitches for any energy.
The Diversity of Root-Associated Endophytic Fungi from Four Epiphytic Orchids in China
Authors: Wang Tao , Chi Miao , Guo Ling , Liu Donghuan , Yang Yu , Zhang Yu
Published: May 2021

Root-associated endophytic fungi (RAF) are found asymptomatically in almost all plant groups. However, little is known about the compositions and potential functions of RAF communities associated with most Orchidaceae species. In this study, the diversity of RAF was examined in four wild epiphytic orchids, Acampe rigida, Doritis pulcherrima, Renanthera coccinea, and Robiquetia succisa, that occur in southern China. A culture-independent method involving Illumina amplicon sequencing, and an in vitro culture method, were used to identify culturable fungi. The RAF community diversity differed among the orchid roots, and some fungal taxa were clearly concentrated in a certain orchid species, with more OTUs being detected. By investigating mycorrhizal associations, the results showed that 28 (about 0.8%) of the 3527 operational taxonomic units (OTUs) could be assigned as OMF, while the OTUs of non-mycorrhizal fungal were about 99.2%. Among the OMFs, Ceratobasidiaceae OTUs were the most abundant with different richness, followed by Thelephoraceae. In addition, five Ceratobasidium sp. strains were isolated from D. pulcherrima, R. succisa, and R. coccinea roots with high separation rates. These culturable Ceratobasidium strains will provide materials for host orchid conservation and for studying the mechanisms underlying mycorrhizal symbiosis.
Identifying User Requirements for an Integrated E-Health Unit for Diabetes Mellitus
Authors: Tzilini Maria , Folinas Dimitris , Kazakos Kyriakos
Published: May 2021

“Continuity of Care” is the main prerequisite for the unhindered movement of people across borders within the European Union (EU). The COntinuity of care in MEtabolic diseases through modern TECHnology (COMETECH) project aims to address the problem of inadequate access to health system services to people who live in isolated communities in Greece and North Macedonia cross-border areas. As the project is almost completed, 4 e-health units—2 in each country—have been established in isolated and deprived communities, aiming at introducing “Continuity of Care” for patients with diabetes in the border region between those countries. The establishment of the e-health units allows affordable access to medical services within Greece-North Macedonia cross-border area. These units (equipped with state-of-the-art medical devices, supported by an advanced software application and medical staff) record data of local people and offer valuable and high-quality medical care services. The records of the EU citizens using the COMETECH services are safely and easily accessible by their physicians. This paper presents the user requirements of e-health units and the medical devices that are set up for the COMETECH Project for helping people with diabetes in the targeted countries.
A Physically Active Status Affects the Circulating Profile of Cancer-Associated miRNAs
Authors: Faraldi Martina , Gerosa Laura , Gomarasca Marta , Sansoni Veronica , Perego Silvia , Ziemann Ewa , Banfi Giuseppe , Lombardi Giovanni
Published: May 2021

Circulating miRNAs are ideal diagnostics and prognostics biomarkers in cancer since altered levels of specific miRNAs have been associated to development/progression of several cancers. Physical activity is a recognized preventive strategy against several cancers, but it may also modify the baseline levels of cancer-associated miRNAs and, hence, may act as a confounding pre-analytical variable. This study aimed at understanding whether physical activity-dependent changes in cancer-associated circulating miRNAs profile could act as a confounding variable. A panel comprising 179 miRNAs was assayed in plasma from 20 highly trained and 10 sedentary men. RT-qPCR data were analyzed with the 2−2ΔΔCT methods and normalized on hsa-miR-320d, as determined by bioinformatics analysis. miRNAs associated with the diagnosis of the most prevalent cancers were considered. Only those miRNAs, relevantly associated with cancers, found ≥2-fold up- or downregulated in highly trained subjects compared to sedentary were disclosed. The results reveal that chronic physical activity determined modifications altering the baseline level of several cancer-associated miRNAs and, hence, their diagnostic and prognostic potential. In conclusion, based on our results, a physically active status emerges as an important pre-analytical variable able to alter the basal level of circulating miRNAs, and these alterations might be considered as potentially misleading the analytical output.
Evaluation of Arterial Spin Labeling MRI—Comparison with 15O-Water PET on an Integrated PET/MR Scanner
Authors: Fahlström Markus , Appel Lieuwe , Kumlien Eva , Danfors Torsten , Engström Mathias , Wikström Johan , Antoni Gunnar , Larsson Elna-Marie , Lubberink Mark
Published: May 2021

Cerebral blood flow (CBF) measurements are of high clinical value and can be acquired non-invasively with no radiation exposure using pseudo-continuous arterial spin labeling (ASL). The aim of this study was to evaluate accordance in resting state CBF between ASL (CBFASL) and 15O-water positron emission tomography (PET) (CBFPET) acquired simultaneously on an integrated 3T PET/MR system. The data comprised ASL and dynamic 15O-water PET data with arterial blood sampling of eighteen subjects (eight patients with focal epilepsy and ten healthy controls, age 21 to 61 years). 15O-water PET parametric CBF images were generated using a basis function implementation of the single tissue compartment model. Cortical and subcortical regions were automatically segmented using Freesurfer. Average CBFASL and CBFPET in grey matter were 60 ± 20 and 75 ± 22 mL/100 g/min respectively, with a relatively high correlation (r = 0.78, p < 0.001). Bland-Altman analysis revealed poor agreement (bias = −15 mL/100 g/min, lower and upper limits of agreements = −16 and 45 mL/100 g/min, respectively) with a negative relationship. Accounting for the negative relationship, the width of the limits of agreement could be narrowed from 61 mL/100 g/min to 35 mL/100 g/min using regression-based limits of agreements. Although a high correlation between CBFASL and CBFPET was found, the agreement in absolute CBF values was not sufficient for ASL to be used interchangeably with 15O-water PET.
Detection and Differentiation of SARS-CoV-2, Influenza, and Respiratory Syncytial Viruses by CRISPR
Authors: Zhou Huifen , Tsou Jen-Hui , Chinthalapally Molangur , Liu Hongjie , Jiang Feng
Published: May 2021

SARS-CoV-2, influenza, and respiratory syncytial viruses (RSVs) cause acute respiratory infections with similar symptoms. Since the treatments and outcomes of these infections are different, the early detection and accurate differentiation of the viruses are clinically important for the prevention and treatment of the diseases. We previously demonstrated that clustered regularly interspaced short palindromic repeats (CRISPR) could rapidly and precisely detect SARS-CoV-2. The objective of this study was to develop CRISPR as a test for simultaneously detecting and accurately distinguishing the viruses. The CRISPR assay with an RNA guide against each virus was performed in the reference standards of SARS-CoV-2, influenza A and B, and RSV. The CRISPR assay had a limit of detection of 1–100 copies/µL for specifically detecting SARS-CoV-2, influenza A and B, and RSV without cross-reaction with other respiratory viruses. The validation of the test in nasopharyngeal specimens showed that it had a 90–100% sensitivity and 100% specificity for the detection of SARS-CoV-2, influenza A and B, and RSV. The CRISPR assay could potentially be used for sensitive detection and specific differentiation of the respiratory viruses.
Salivary Biomarkers for Diagnosis and Therapy Monitoring in Patients with Heart Failure. A Systematic Review
Authors: Rammos Aidonis , Bechlioulis Aris , Kalogeras Petros , Tripoliti Evanthia E. , Goletsis Yorgos , Kalivi Anna , Blathra Effrosyni , Salvo Pietro , Trivella M. Giovanna , Lomonaco Tommaso , Fuoco Roger , Bellagambi Francesca , Watson Chris J. , Errachid Abdelhamid , Fotiadis Dimitrios I. , Michalis Lampros K. , Naka Katerina K.
Published: May 2021

The aim of this study was to perform a systematic review on the potential value of saliva biomarkers in the diagnosis, management and prognosis of heart failure (HF). The correlation between saliva and plasma values of these biomarkers was also studied. PubMed was searched to collect relevant literature, i.e., case-control, cross-sectional studies that either compared the values of salivary biomarkers among healthy subjects and HF patients, or investigated their role in risk stratification and prognosis in HF patients. No randomized control trials were included. The search ended on 31st of December 2020. A total of 15 studies met the inclusion criteria. 18 salivary biomarkers were analyzed and the levels of all biomarkers studied were found to be higher in HF patients compared to controls, except for amylase, sodium, and chloride that had smaller saliva concentrations in HF patients. Natriuretic peptides are the most commonly used plasma biomarkers in the management of HF. Their saliva levels show promising results, although the correlation of saliva to plasma values is weakened in higher plasma values. In most of the publications, differences in biomarker levels between HF patients and controls were found to be statistically significant. Due to the small number of patients included, larger studies need to be conducted in order to facilitate the use of saliva biomarkers in clinical practice.
A Reliable Indirect ELISA Protocol for Detection of Human Antibodies Directed to SARS-CoV-2 NP Protein
Authors: Faizo Arwa A. , Alandijany Thamir A. , Abbas Ayman T. , Sohrab Sayed S. , El-Kafrawy Sherif A. , Tolah Ahmed M. , Hassan Ahmed M. , Azhar Esam I.
Published: May 2021

A few months ago, the availability of a reliable and cost-effective testing capacity for COVID-19 was a concern for many countries. With the emergence and circulation of new SARS-CoV-2 variants, another layer of challenge can be added for COVID-19 testing at both molecular and serological levels. This is particularly important for the available tests principally designed to target the S gene/protein where multiple mutations have been reported. Herein, the SARS-CoV-2 NP recombinant protein was utilized to develop a simple and reliable COVID-19 NP human IgG ELISA. The optimized protocol was validated against a micro-neutralization (MN) assay, in-house S-based ELISA, and commercial chemiluminescence immunoassay (CLIA). The developed assay provides 100% sensitivity, 98.9% specificity, 98.9% agreement, and high overall accuracy with an area under curve equal to 0.9998 ± 0.0002 with a 95% confidence interval of 0.99 to 1.00. The optical density values of positive samples significantly correlated with their corresponding MN titers. The assay specifically detects IgG antibodies to the SARS-CoV-2 NP protein and does not cross-detect IgG to the viral S protein. Moreover, it does not cross-react with antibodies related to other coronaviruses (e.g., the Middle East respiratory syndrome coronavirus or human coronavirus HKU1). The availability of this reliable COVID-19 NP IgG ELISA protocol is highly valuable for its diagnostic and epidemiological applications.
Editorial for the Launching of Dynamics
Authors: Volos Christos
Published: May 2021

Nowadays, the subject of studying system dynamics behavior has become very important in many branches of technology [...]
Intuitionistic Fuzzy TOPSIS as a Method for Assessing Socioeconomic Phenomena on the Basis of Survey Data
Authors: Roszkowska Ewa , Kusterka-Jefmańska Marta , Jefmański Bartłomiej
Published: May 2021

In the assessment of most complex socioeconomic phenomena with the use of multicriteria methods, continuous data are used, the source of which are most often public statistics. However, there are complex phenomena such as quality of life and quality of services in the assessment, for which questionnaire surveys and ordinal measurement scales are used. In this case, the use of classic multicriteria methods is very difficult, taking into account the way of presenting this type of data by official statistics, as well as their permissible transformations and arithmetic operations. Therefore, the main purpose of this study was the presentation of a novel framework which can be applied for assessing socioeconomic phenomena on the basis of survey data. It was assumed that the object assessments may contain positive or negative opinions and an element of uncertainty expressed in the form a “no”, “difficult to say”, or “no opinion” answers. For this reason, the intuitionistic fuzzy TOPSIS (IF-TOPSIS) method is proposed. To demonstrate the potential of this solution, the results of measuring the subjective quality of life of the inhabitants of 83 cities in EU countries, EFTA countries, the UK, the Western Balkans, and Turkey are presented. For most cities, a high level of subjective quality of life was observed using the proposed approach. The highest level of quality of life was observed in Zurich, whereas the lowest was observed in Palermo.
Joint Green Marketing Decision-Making of Green Supply Chain Considering Power Structure and Corporate Social Responsibility
Authors: Huang Jialiang , Wang Xiaoxia , Luo Yuxi , Yu Liying , Zhang Ziyuan
Published: May 2021

In order to explore the impact of a manufacturer’s or retailer’s undertaking corporate social responsibility (CSR) and different power structures on their joint green marketing decisions and profits in the green supply chain, this paper establishes green supply chain optimization models under six different decision-making scenarios according to two different CSR bearers and three different power structures. Based on the main assumptions of a linear product demand function and CSR measured by consumer surplus, this paper solves the equilibrium solutions of the manufacturer and the retailer through game theory. The results show that: First, the difference in the degree of CSR undertaken by manufacturers and retailers leads to a difference in the ranking of optimal strategies of both parties under the three power structures. Second, under the same power structure, compared with undertaking CSR by oneself, when the other party undertakes CSR, the level of the product’s green degree, the level of green promotion, the party’s own profit, and the profit of the other party are all higher. Third, regardless of the power structure, manufacturers and retailers undertaking CSR is conducive to improving the level of product greenness, increasing green promotion, lowering the retail price, increasing consumers’ willingness to buy green products, and ultimately helping to increase the profits of manufacturers and retailers.
Unsupervised Exemplar-Domain Aware Image-to-Image Translation
Authors: Fu Yuanbin , Ma Jiayi , Guo Xiaojie
Published: May 2021

Image-to-image translation is used to convert an image of a certain style to another of the target style with the original content preserved. A desired translator should be capable of generating diverse results in a controllable many-to-many fashion. To this end, we design a novel deep translator, namely exemplar-domain aware image-to-image translator (EDIT for short). From a logical perspective, the translator needs to perform two main functions, i.e., feature extraction and style transfer. With consideration of logical network partition, the generator of our EDIT comprises of a part of blocks configured by shared parameters, and the rest by varied parameters exported by an exemplar-domain aware parameter network, for explicitly imitating the functionalities of extraction and mapping. The principle behind this is that, for images from multiple domains, the content features can be obtained by an extractor, while (re-)stylization is achieved by mapping the extracted features specifically to different purposes (domains and exemplars). In addition, a discriminator is equipped during the training phase to guarantee the output satisfying the distribution of the target domain. Our EDIT can flexibly and effectively work on multiple domains and arbitrary exemplars in a unified neat model. We conduct experiments to show the efficacy of our design, and reveal its advances over other state-of-the-art methods both quantitatively and qualitatively.
Augmenting Paraphrase Generation with Syntax Information Using Graph Convolutional Networks
Authors: Chi Xiaoqiang , Xiang Yang
Published: May 2021

Paraphrase generation is an important yet challenging task in natural language processing. Neural network-based approaches have achieved remarkable success in sequence-to-sequence learning. Previous paraphrase generation work generally ignores syntactic information regardless of its availability, with the assumption that neural nets could learn such linguistic knowledge implicitly. In this work, we make an endeavor to probe into the efficacy of explicit syntactic information for the task of paraphrase generation. Syntactic information can appear in the form of dependency trees, which could be easily acquired from off-the-shelf syntactic parsers. Such tree structures could be conveniently encoded via graph convolutional networks to obtain more meaningful sentence representations, which could improve generated paraphrases. Through extensive experiments on four paraphrase datasets with different sizes and genres, we demonstrate the utility of syntactic information in neural paraphrase generation under the framework of sequence-to-sequence modeling. Specifically, our graph convolutional network-enhanced models consistently outperform their syntax-agnostic counterparts using multiple evaluation metrics.
Computational Modeling of Boundary Layer Flashback in a Swirling Stratified Flame Using a LES-Based Non-Adiabatic Tabulated Chemistry Approach
Authors: Jiang Xudong , Tang Yihao , Liu Zhaohui , Raman Venkat
Published: May 2021

When operating under lean fuel–air conditions, flame flashback is an operational safety issue in stationary gas turbines. In particular, with the increased use of hydrogen, the propagation of the flame through the boundary layers into the mixing section becomes feasible. Typically, these mixing regions are not designed to hold a high-temperature flame and can lead to catastrophic failure of the gas turbine. Flame flashback along the boundary layers is a competition between chemical reactions in a turbulent flow, where fuel and air are incompletely mixed, and heat loss to the wall that promotes flame quenching. The focus of this work is to develop a comprehensive simulation approach to model boundary layer flashback, accounting for fuel–air stratification and wall heat loss. A large eddy simulation (LES) based framework is used, along with a tabulation-based combustion model. Different approaches to tabulation and the effect of wall heat loss are studied. An experimental flashback configuration is used to understand the predictive accuracy of the models. It is shown that diffusion-flame-based tabulation methods are better suited due to the flashback occurring in relatively low-strain and lean fuel–air mixtures. Further, the flashback is promoted by the formation of features such as flame tongues, which induce negative velocity separated boundary layer flow that promotes upstream flame motion. The wall heat loss alters the strength of these separated flows, which in turn affects the flashback propensity. Comparisons with experimental data for both non-reacting cases that quantify fuel–air mixing and reacting flashback cases are used to demonstrate predictive accuracy.
Dynamics of Human Capital Development in Economic Development Cycles
Authors: Gruzina Yulia , Firsova Irina , Strielkowski Wadim
Published: May 2021

Our paper focuses on the dynamics of development of human capital in economic development cycles (as described, for example, in the works of Becker or Barro). In the course of this research, we created an econometric model based on the modified Mankiw‒Romer‒Weil equation of the Cobb‒Douglas function which takes into account the factor of convergence/divergence and differentiation due to changes in the size of territories, population, volume of economies, and other parameters of the studied states and societies. The applied Theil index makes it possible (since it can be used as a “transition key”) to compare the dynamic time series of human capital development in the early industrial and post-industrial, knowledge, as well as the information cycles of economic development. Drawing on the historical experience of four industrial revolutions, our paper finds that, contrary to popular belief, which considers early industrialization to be a largely unfettered process and human capital development to be a by-product, the Industrial Revolutions actually contributed to the formation of human capital by fostering new technologies and opening up opportunities for personal development for a large number of people, as well as creating a large numbers of new jobs and significantly increasing productivity and wages. Our approach makes it possible to calculate the development of human capital for each cycle of economic development according to separate formulas and then compare them in one dynamic series. Our results might be relevant for stakeholders and policy-makers in the countries largely relying upon the export of their natural resources who might want to attempt changing their dependency and to invest in the formation of a knowledge-based economy based on the high-quality human capital.
Exploration of the Factors that Influence the Implementation of Environmental Management Systems—The Case of Slovakia
Authors: Petrová Eva , Štofa Tomáš , Šoltés Michal
Published: May 2021

Considering internationally accepted voluntary standards of an environmental management system (EMS) as tools that can help businesses meet the agenda for sustainable development and environmental wellbeing, this study aims to examine selected firm characteristics and financial performance that are potentially related to decisions of business entities in the matter of voluntary EMS implementation. We conduct empirical research based on logistic regression to study Slovak firms that are or are not certified according to ISO 14001 and EMAS standards. Our results suggest that there are several factors potentially determining the positive company choice to adopt voluntary EMS. We have confirmed the positive effect of firm size and research and development, however, we were not able to confirm the effects of foreign ownership and profitability effects. In the case of indebtedness, we have found a stronger negative effect of long-term debt. Our results also suggest a positive effect of owning a website, where companies can share information about their certificates. On the other side, especially younger companies tend to be interested in voluntary EMS.
The Relationship between the Company’s Value and the Tone of the Risk-Related Narratives: The Case of Portugal
Authors: Oliveira Michele Gendelsky de , Azevedo Graça , Oliveira Jonas
Published: May 2021

The present study aims to identify the impact of the tone of risk reporting narratives on company market value. The paper uses a sample of 34 Portuguese non-finance companies with shares traded at the Euronext Lisbon stock exchange market. The paper conducts an automated content analysis of the risk reporting narratives included in the risk and risk management sections of the annual reports for 2018 by using the software DICTION 7 (Digitext, Inc., Austin, TX, USA) to retrieve the speech tone. Main findings indicate that the tone category “activity” is associated negatively with the company’s market value. This result shows that investors misprice risk information that incorporates traces of overconfidence, narcissistic self-confidence and heroic leadership. The present study extends prior literature by analyzing the economic incentives of the tone of risk reporting narratives, not yet studied. Findings are both relevant to investors to support their decision-making processes and managers to strategically manage their risk communication tactics and benefit from the advantages emanated from them. Limitations related to the research setting do not undermine the generalization of findings because the automated algorithm provided by DICTION assures the content analysis’s reliability. The sample used corresponds to the population of the Portuguese non-finance listed companies.
How Do Five- to Six-Year-Old Children Interpret a Burning Candle?
Authors: Sesto Vanessa , García-Rodeja Isabel
Published: May 2021

Many studies have been conducted in recent years on the explanations given by preschool-age children about different natural phenomena. Nonetheless, very few studies have actually focused on the important domain of matter and its transformations. Specifically, the field of chemical reactions remains unexplored. This qualitative study aims to investigate the explanations of twenty-two 5- to 6-year-old children about combustion, while at the same time evaluating the effect of prior experience with science activities on their interpretations. For this study, the following experiment was proposed: burning a candle inside an inverted vessel. The following data collection tools were used: a Predict-Observe-Explain (POE) strategy and audio and video recordings. The children’s explanations were analysed using classification frameworks, which had been developed in previous studies. The results of this study suggest that young children tend to provide naturalistic explanations about combustion. This finding is an indicator that young children are able to construct mental representations within this conceptual domain. Likewise, the results indicate that children who are used to engaging in inquiry-based activities may be more likely to establish a relationship with previous learning experiences to interpret other natural phenomena.
RETRACTED: Kinematic of the Position and Orientation Synchronization of the Posture of a n DoF Upper-Limb Exoskeleton with a Virtual Object in an Immersive Virtual Reality Environment
Authors: Huamanchahua Deyby , Vargas-Martinez Adriana , Ramirez-Mendoza Ricardo
Published: May 2021

Exoskeletons are an external structural mechanism with joints and links that work in tandem with the user, which increases, reinforces, or restores human performance. Virtual Reality can be used to produce environments, in which the intensity of practice and feedback on performance can be manipulated to provide tailored motor training. Will it be possible to combine both technologies and have them synchronized to reach better performance? This paper consists of the kinematics analysis for the position and orientation synchronization between an n DoF upper-limb exoskeleton pose and a projected object in an immersive virtual reality environment using a VR headset. To achieve this goal, the exoskeletal mechanism is analyzed using Euler angles and the Pieper technique to obtain the equations that lead to its orientation, forward, and inverse kinematic models. This paper extends the author’s previous work by using an early stage upper-limb exoskeleton prototype for the synchronization process.
Remote Laboratory for Online Engineering Education: The RLAB-UOC-FPGA Case Study
Authors: Monzo Carlos , Cobo Germán , Morán José Antonio , Santamaría Eugènia , García-Solórzano David
Published: May 2021

Practical experiments are essential for engineering studies. Regarding the acquisition of practical and professional competences in a completely online scenario, the use of technology that allows students to carry out practical experiments is important. This paper presents a remote laboratory designed and developed by the Open University of Catalonia (RLAB-UOC), which allows engineering students studying online to carry out practical experiments anywhere and anytime with real electronic and communications equipment. The features of the remote laboratory and students’ satisfaction with its use are analyzed in real subjects across six semesters using a self-administered questionnaire in an FPGA-based case study. The results for the FPGA-based case study present the perception and satisfaction of students using the proposed remote laboratory in the acquisition of subject competences and content.
Robust Circuit and System Design for General-Purpose Computational Resistive Memories
Authors: Pinto Felipe , Vourkas Ioannis
Published: May 2021

Resistive switching devices (memristors) constitute a promising device technology that has emerged for the development of future energy-efficient general-purpose computational memories. Research has been done both at device and circuit level for the realization of primitive logic operations with memristors. Likewise, important efforts are placed on the development of logic synthesis algorithms for resistive RAM (ReRAM)-based computing. However, system-level design of computational memories has not been given significant consideration, and developing arithmetic logic unit (ALU) functionality entirely using ReRAM-based word-wise arithmetic operations remains a challenging task. In this context, we present our results in circuit- and system-level design, towards implementing a ReRAM-based general-purpose computational memory with ALU functionality. We built upon the 1T1R crossbar topology and adopted a logic design style in which all computations are equivalent to modified memory read operations for higher reliability, performed either in a word-wise or bit-wise manner, owing to an enhanced peripheral circuitry. Moreover, we present the concept of a segmented ReRAM architecture with functional and topological features that benefit flexibility of data movement and improve latency of multi-level (sequential) in-memory computations. Robust system functionality is validated via LTspice circuit simulations for an n-bit word-wise binary adder, showing promising performance features compared to other state-of-the-art implementations.
A High Efficiency Low Noise RF-to-DC Converter Employing Gm-Boosting Envelope Detector and Offset Canceled Latch Comparator
Authors: Pham Thithuy , Kim Dongmin , Jeong Seohyeong , Lee Junghyup , Im Donggu
Published: May 2021

This work presents a high efficiency RF-to-DC conversion circuit composed of an LC-CL balun-based Gm-boosting envelope detector, a low noise baseband amplifier, and an offset canceled latch comparator. It was designed to have high sensitivity with low power consumption for wake-up receiver (WuRx) applications. The proposed envelope detector is based on a fully integrated inductively degenerated common-source amplifier with a series gate inductor. The LC-CL balun circuit is merged with the core of the envelope detector by sharing the on-chip gate and source inductors. The proposed technique doubles the transconductance of the input transistor of the envelope detector without any extra power consumption because the gate and source voltage on the input transistor operates in a differential mode. This results in a higher RF-to-DC conversion gain. In order to improve the sensitivity of the wake-up radio, the DC offset of the latch comparator circuit is canceled by controlling the body bias voltage of a pair of differential input transistors through a binary-weighted current source cell. In addition, the hysteresis characteristic is implemented in order to avoid unstable operation by the large noise at the compared signal. The hysteresis window is programmable by changing the channel width of the latch transistor. The low noise baseband amplifier amplifies the output signal of the envelope detector and transfers it into the comparator circuit with low noise. For the 2.4 GHz WuRx, the proposed envelope detector with no external matching components shows the simulated conversion gain of about 16.79 V/V when the input power is around the sensitivity of −60 dBm, and this is 1.7 times higher than that of the conventional envelope detector with the same current and load. The proposed RF-to-DC conversion circuit (WuRx) achieves a sensitivity of about −65.4 dBm based on 45% to 55% duty, dissipating a power of 22 μW from a 1.2 V supply voltage.
The Performance Assessment of Six Global Horizontal Irradiance Clear Sky Models in Six Climatological Regions in South Africa
Authors: Mabasa Brighton , Lysko Meena D. , Tazvinga Henerica , Zwane Nosipho , Moloi Sabata J.
Published: May 2021

This study assesses the performance of six global horizontal irradiance (GHI) clear sky models, namely: Bird, Simple Solis, McClear, Ineichen–Perez, Haurwitz and Berger–Duffie. The assessment is performed by comparing 1-min model outputs to corresponding clear sky reference 1-min Baseline Surface Radiation Network quality controlled GHI data from 13 South African Weather Services radiometric stations. The data used in the study range from 2013 to 2019. The 13 reference stations are across the six macro climatological regions of South Africa. The aim of the study is to identify the overall best performing clear sky model for estimating minute GHI in South Africa. Clear sky days are detected using ERA5 reanalysis hourly data and the application of an additional 1-min automated detection algorithm. Metadata for the models’ inputs were sourced from station measurements, satellite platform observations, reanalysis and some were modelled. Statistical metrics relative Mean Bias Error (rMBE), relative Root Mean Square Error (rRMSE) and the coefficient of determination (R2) are used to categorize model performance. The results show that each of the models performed differently across the 13 stations and in different climatic regions. The Bird model was overall the best in all regions, with an rMBE of 1.87%, rRMSE of 4.11% and R2 of 0.998. The Bird model can therefore be used with quantitative confidence as a basis for solar energy applications when all the required model inputs are available.
Numerical Investigation into the Natural Convection of Cryogenic Supercritical Helium in a Spherical Enclosure
Authors: Qiu Yinan , Zhai Hua , Zheng Yao , Lei Gang , Wang Tianxiang , Wang Li , Shu Shuiming
Published: May 2021

As an ideal pressurized gas, helium, especially supercritical helium, has been widely used in the pressurization system of various launch vehicles and spacecraft. This work mainly focuses on the natural convection of cryogenic supercritical helium in a spherical enclosure. Firstly, a three-dimensional numerical model is established and verified with experimental data. Then, the effects of inflation pressure and heating power on the flow and heat transfer characteristics are simulated. At the same time, the relationship between the Rayleigh number and Nusselt number is studied in detail. Finally, an improved natural convection heat transfer correlation modified by introducing the density ratio is obtained. The results show that the increase of the inflation pressure in the cavity is helpful to enhance the natural convection heat transfer of the cryogenic supercritical helium, and the temperature distribution in the cavity tends to be more uniform when the inflation pressure in the cavity increases. As to the improved natural convection heat transfer correlation, the average error between the simulation results and the calculated values is approximately 8%, which can better describe the natural convection heat transfer of cryogenic supercritical helium in the spherical enclosure.
Sensitivity Analysis of OTEC-CC-MX-1 kWe Plant Prototype
Authors: Tobal-Cupul Jessica Guadalupe , Cerezo-Acevedo Estela , Arriola-Gil Yair Yosias , Gomez-Garcia Hector Fernando , Romero-Medina Victor Manuel
Published: May 2021

The Mexican Caribbean Sea has potential zones for Ocean Thermal Energy Conversion (OTEC) implementation. Universidad del Caribe and Instituto de Ciencias del Mar y Limnologia, with the support of the Mexican Centre of Innovation in Ocean Energy, designed and constructed a prototype OTEC plant (OTEC-CC-MX-1 kWe), which is the first initiative in Mexico for exploitation of this type of renewable energy. This paper presents a sensitivity analysis whose objective was to know, before carrying out the experimental tests, the behavior of OTEC-CC-MX-1 kWe regarding temperature differences, as well as the non-possible operating conditions, which allows us to assess possible modifications in the prototype installation. An algorithm was developed to obtain the inlet and outlet temperatures of the water and working fluid in the heat exchangers using the monthly surface and deep-water temperature data from the Hybrid Coordinate Ocean Model and Geographically Weighted Regression Temperature Model for the Mexican Caribbean Sea. With these temperatures, the following were analyzed: fluctuation of thermal efficiency, mass flows of R-152a and water and power production. By analyzing the results, we verified maximum and minimum mass flows of water and R-152a to produce 1 kWe during a typical year in the Mexican Caribbean Sea and the conditions when the production of electricity is not possible for OTEC-CC-MX-1 kWe.
Evaluation of the Effect of Anti-Corrosion Coatings on the Thermal Resistance of Ground Heat Exchangers for Shallow Geothermal Applications
Authors: Cadelano Gianluca , Bortolin Alessandro , Ferrarini Giovanni , Bison Paolo , Dalla Santa Giorgia , Di Sipio Eloisa , Bernardi Adriana , Galgaro Antonio
Published: May 2021

The materials and the technology used to build the ground heat exchangers significantly affect the heat transfer performance of a geothermal system, in addition to the local geological and hydrogeological context. Among expense items such as the coupled heat pumps and the applied drilling technology, the heat exchangers play a key role in the shallow geothermal market. For this reason, they are usually made with plastic. Metal tubes are not widely used because of corrosion issues, which can compromise the reliability of the system over time. According to best practices, metal is an unfavorable choice if the pipes are not made of corrosion resistant alloys, such as stainless steel, but the overall performance is strongly related to the heat transfer efficiency. In this study, laser-flash technique is applied on carbon steel samples with anti-corrosion coatings and on corrosion resistant materials (stainless steel grades used for pipes), thus, allowing the comparison of their thermophysical properties. These properties are used to evaluate each solution in terms of thermal resistance. This study demonstrates that there are no particular corrosion resistant steel pipe configurations that are thermally favorable over others in a critical way.
A Novel Hybrid GWO-LS Estimator for Harmonic Estimation Problem in Time Varying Noisy Environment
Authors: Abdullah Muhammad , Malik Tahir N. , Ahmed Ali , Nadeem Muhammad F. , Khan Irfan A. , Bo Rui
Published: May 2021

The power quality of the Electrical Power System (EPS) is greatly affected by electrical harmonics. Hence, accurate and proper estimation of electrical harmonics is essential to design appropriate filters for mitigation of harmonics and their associated effects on the power quality of EPS. This paper presents a novel statistical (Least Square) and meta-heuristic (Grey wolf optimizer) based hybrid technique for accurate detection and estimation of electrical harmonics with minimum computational time. The non-linear part (phase and frequency) of harmonics is estimated using GWO, while the linear part (amplitude) is estimated using the LS method. Furthermore, harmonics having transients are also estimated using proposed harmonic estimators. The effectiveness of the proposed harmonic estimator is evaluated using various case studies. Comparing the proposed approach with other harmonic estimation techniques demonstrates that it has a minimum mean square error with less complexity and better computational efficiency.
Nanomaterials in Protection of Buildings and Infrastructure Elements in Highly Aggressive Marine Environments
Authors: del Campo Jose Maria , Negro Vicente
Published: May 2021

The 2030 Agenda and Sustainable Development Goals (SDG) are both an engineering challenge and an opportunity. Clean energy (SDG 7), sustainable cities and communities (SDG 11), and climate action (SDG 13) represent an effort to manage, plan, and develop our buildings and infrastructure. The purpose of this study is to contribute to this challenge by analysing nanomaterials in marine environment structures, both urban and maritime. To do this, we have analyzed different regulations of concrete properties in various countries, defining the characteristics of the cement, coating, water/cement rating, and chloride effect; the difference in durability based on conventional reinforcements and nanomaterials; and use on highly sensitive elements, buildings in marine environments, rubble mound structures, crown walls, and gravity-based foundations for wind power facilities. Division into overhead, underwater, or splash zones entails the use of epoxy resins or silica fume matrices in percentages far below ten percent. Using the most exposed and unfavorable structures, conclusions of application to buildings are established based on the recommendations in maritime engineering most exposed to the actions of the waves. The study concludes with recommendations regarding the durability, increased lifespan, and use of new materials in infrastructure elements in highly adverse marine environments.
Application of 3D Scanning, Computer Simulations and Virtual Reality in the Redesigning Process of Selected Areas of Underground Transportation Routes in Coal Mining Industry
Authors: Rozmus Magdalena , Tokarczyk Jarosław , Michalak Dariusz , Dudek Marek , Szewerda Kamil , Rotkegel Marek , Lamot Aleš , Rošer Janez
Published: May 2021

Nowadays designing of selected areas of mines underground workings can be effectively improved by the application of computer techniques: 3D scanning, computer simulations and Virtual Reality. This, in fact, would result in the more reliable design process, significantly reduced designing costs and efforts, and improvement of the mines staff’s safety. This scientific paper presents a method developed for redesigning of selected areas of mines underground workings in which auxiliary transport is carried out. The method combines 3D laser scanning technique with computer simulations carried out in a CAD/MBS system, in order to determine the location of potential collisions of the transported loads with the arch yielding support and the equipment. The obtained results, visualized using Virtual Reality, will form input data in the process of designing the selected area of the mines underground workings. Finally, an example of the application of the described method during transportation of big-size load is given.