bluuebunny/crossref_metadata_2025 huggingface dataset:
Automated Classification of Brain Tumors from Magnetic Resonance Imaging Using Deep Learning
Authors: Rasheed Zahid , Ma Yong-Kui , Ullah Inam , Al Shloul Tamara , Tufail Ahsan Bin , Ghadi Yazeed Yasin , Khan Muhammad Zubair , Mohamed Heba G.
Published: April 2023

Brain tumor classification is crucial for medical evaluation in computer-assisted diagnostics (CAD). However, manual diagnosis of brain tumors from magnetic resonance imaging (MRI) can be time-consuming and complex, leading to inaccurate detection and classification. This is mainly because brain tumor identification is a complex procedure that relies on different modules. The advancements in Deep Learning (DL) have assisted in the automated process of medical images and diagnostics for various medical conditions, which benefits the health sector. Convolutional Neural Network (CNN) is one of the most prominent DL methods for visual learning and image classification tasks. This study presents a novel CNN algorithm to classify the brain tumor types of glioma, meningioma, and pituitary. The algorithm was tested on benchmarked data and compared with the existing pre-trained VGG16, VGG19, ResNet50, MobileNetV2, and InceptionV3 algorithms reported in the literature. The experimental results have indicated a high classification accuracy of 98.04%, precision, recall, and f1-score success rate of 98%, respectively. The classification results proved that the most common kinds of brain tumors could be categorized with a high level of accuracy. The presented algorithm has good generalization capability and execution speed that can be helpful in the field of medicine to assist doctors in making prompt and accurate decisions associated with brain tumor diagnosis.
Mechanical Properties of Steel Fiber-Reinforced, Recycled, Concrete-Filled Intersecting Nodes in an Oblique Grid
Authors: Zhao Jun , Wang Feicheng , Zhu Yinhong , Yang Bai
Published: April 2023

The construction of high-rise oblique grid buildings requires a large amount of concrete. To save resources, an oblique grid of intersecting nodes composed of steel outer tubes and steel fiber, recycled concrete inner tubes (OGSFRCIN) has been proposed. ABAQUS is used to study the mechanical properties of the nodes under axial pressure, accounting for the effects of six parameters: the oblique angle, the thickness of the stiffening ring, the thickness of the connecting plate, the concrete strength, the recycled aggregate replacement rate, and the steel fiber content. The results show that the oblique angle, connecting plate thickness, concrete strength, and steel fiber content significantly affect the ultimate bearing capacity of specimens. The reinforcing ring thickness has a significant effect on the evolution of lateral displacement. It is not advisable to use components with a replacement rate of 100% recycled aggregate in engineering practice because of insufficient lateral stiffness and ultimate strength. The specimen’s out-of-plane displacement is tightly restricted when the connecting plate’s thickness is greater than or equal to 10 mm. In practical engineering, the connecting plate and reinforcing ring thickness should not be less than 10 mm, and the recommended steel fiber content is 1.0% to 2.0%. Through the analysis of the mechanical properties of the OGSFRCIN under monotonic axial compression and reciprocating axial tension and compression loads, it can be seen that OGSFRCIN have good mechanical properties and can be applied in engineering practice. Here, the modified formulas for calculating the bearing capacity of OGSFRCIN are put forward.
The Width-Thickness Ratio Limits of Thin-Walled Steel Elements with Complex Edge Stiffeners
Authors: Zhang Junfeng , Gao Shuran , Li Bo , Chu Liusheng , Wang Huan
Published: April 2023

Complex edge stiffeners are widely used because of their superior performance over simple edge stiffeners in limiting flange buckling and improving local stability. However, most of the studies on complex edge stiffeners are qualitative. In this paper, the criterion to judge the stiffening adequacy based on the buckling half-wavelength and buckling coefficient is proposed. It is considered as the criterion that the edge stiffeners’ stiffness is not less than the minimum stiffening stiffness or the half-wavelength of buckling is not more than the width of the flange. The criterion is followed for the minimum limits of the edge stiffener width−thickness ratios; whether the flange buckling occurs before the edge stiffener buckling and the economic implications are the criteria that should be followed for the maximum limits of the edge stiffener width−thickness ratios. Using the finite strip method, the feasibility of the criteria was verified by comparing them with the rules of simple edge stiffeners. The detailed design requirements for the width−thickness ratio limits of thin-walled steel elements with complex edge stiffeners were first given from an extensive parametric analysis. Based on the optimization algorithm, the suggestions and optimum sizes of complex edge stiffeners for thin-walled steel elements are provided, considering the sections’ economy and performance. It is considered that a ratio of 1:1 between the primary and the secondary edge stiffeners’ widths is the best configuration for elements with complex edge stiffeners.
Ultrasound for Breast Cancer Screening in Resource-Limited Settings: Current Practice and Future Directions
Authors: Dan Qing , Zheng Tingting , Liu Li , Sun Desheng , Chen Yun
Published: April 2023

Breast cancer (BC) is the most prevalent cancer among women globally. Cancer screening can reduce mortality and improve women’s health. In developed countries, mammography (MAM) has been primarily utilized for population-based BC screening for several decades. However, it is usually unavailable in low-resource settings due to the lack of equipment, personnel, and time necessary to conduct and interpret the examinations. Ultrasound (US) with high detection sensitivity for women of younger ages and with dense breasts has become a supplement to MAM for breast examination. Some guidelines suggest using US as the primary screening tool in certain settings where MAM is unavailable and infeasible, but global recommendations have not yet reached a unanimous consensus. With the development of smart devices and artificial intelligence (AI) in medical imaging, clinical applications and preclinical studies have shown the potential of US combined with AI in BC screening. Nevertheless, there are few comprehensive reviews focused on the role of US in screening BC in underserved conditions, especially in technological, economical, and global perspectives. This work presents the benefits, limitations, advances, and future directions of BC screening with technology-assisted and resource-appropriate strategies, which may be helpful to implement screening initiatives in resource-limited countries.
Contribution of Epstein–Barr Virus Lytic Proteins to Cancer Hallmarks and Implications from Other Oncoviruses
Authors: Dorothea Mike , Xie Jia , Yiu Stephanie Pei Tung , Chiang Alan Kwok Shing
Published: April 2023

Epstein–Barr virus (EBV) is a prevalent human gamma-herpesvirus that infects the majority of the adult population worldwide and is associated with several lymphoid and epithelial malignancies. EBV displays a biphasic life cycle, namely, latent and lytic replication cycles, expressing a diversity of viral proteins. Among the EBV proteins being expressed during both latent and lytic cycles, the oncogenic roles of EBV lytic proteins are largely uncharacterized. In this review, the established contributions of EBV lytic proteins in tumorigenesis are summarized according to the cancer hallmarks displayed. We further postulate the oncogenic properties of several EBV lytic proteins by comparing the evolutionary conserved oncogenic mechanisms in other herpesviruses and oncoviruses.
Enzymatic Synthesis of Ascorbic Acid-Ketone Body Hybrids
Authors: Venturi Valentina , Lerin Lindomar Alberto , Presini Francesco , Giovannini Pier Paolo , Catani Martina , Buratti Alessandro , Marchetti Nicola , Dilliraj Latha Nagamani , Aprile Simona
Published: April 2023

Molecular hybrids obtained by connecting two or more bioactive molecules through a metabolizable linker are used as multi-target drugs for the therapy of multifactorial diseases. Ascorbic acid, as well as the ketone bodies acetoacetate and (R)-3-hydroxybutyrate, are bioactive molecules that have common fields of application in the treatment and prevention of neurodegenerative diseases and cardiac injuries as well. In spite of this, the preparation of ascorbic acid ketone body hybrids is uncovered by the literature. Herein, we report the lipase-catalyzed condensation of methyl acetoacetate with ascorbic acid, which affords the 6-O-acetoacetyl ascorbic acid in quantitative yield. The same approach, employing the methyl (R)-3-hydroxybutyrate in place of the methyl acetoacetate, allows the preparation of the 6-O-(R)-3-hydroxybutyryl ascorbic acid in 57% yield. A better result (90% overall yield) is achieved through the lipase-catalyzed coupling of ascorbic acid with methyl (R)-3-O-methoxymethyl-3-hydroxybutyrate followed by the cleavage of the MOM protecting group. The two novel products are fully characterized and additional information on the antioxidant activity of the new products is also given.
Fatty Acid Excess Dysregulates CARF to Initiate the Development of Hepatic Steatosis
Authors: Hasan Kamrul M. , Parveen Meher , Pena Alondra , Bautista Francisco , Rivera Juan Carlos , Huerta Roxana Ramirez , Martinez Erica , Espinoza-Derout Jorge , Sinha-Hikim Amiya P. , Friedman Theodore C.
Published: April 2023

CARF (CDKN2AIP) regulates cellular fate in response to various stresses. However, its role in metabolic stress is unknown. We found that fatty livers from mice exhibit low CARF expression. Similarly, overloaded palmitate inhibited CARF expression in HepG2 cells, suggesting that excess fat-induced stress downregulates hepatic CARF. In agreement with this, silencing and overexpressing CARF resulted in higher and lower fat accumulation in HepG2 cells, respectively. Furthermore, CARF overexpression lowered the ectopic palmitate accumulation in HepG2 cells. We were interested in understanding the role of hepatic CARF and underlying mechanisms in the development of NAFLD. Mechanistically, transcriptome analysis revealed that endoplasmic reticulum (ER) stress and oxidative stress pathway genes significantly altered in the absence of CARF. IRE1α, GRP78, and CHOP, markers of ER stress, were increased, and the treatment with TUDCA, an ER stress inhibitor, attenuated fat accumulation in CARF-deficient cells. Moreover, silencing CARF caused a reduction of GPX3 and TRXND3, leading to oxidative stress and apoptotic cell death. Intriguingly, CARF overexpression in HFD-fed mice significantly decreased hepatic steatosis. Furthermore, overexpression of CARF ameliorated the aberrant ER function and oxidative stress caused by fat accumulation. Our results further demonstrated that overexpression of CARF alleviates HFD-induced insulin resistance assessed with ITT and GTT assay. Altogether, we conclude that excess fat-induced reduction of CARF dysregulates ER functions and lipid metabolism leading to hepatic steatosis.
Impaired Mitochondrial Function in T-Lymphocytes as a Result of Exposure to HIV and ART
Authors: Blagov Alexander V. , Sukhorukov Vasily N. , Guo Shuzhen , Zhang Dongwei , Popov Mikhail A. , Orekhov Alexander N.
Published: April 2023

Mitochondrial dysfunction is a described phenomenon for a number of chronic and infectious diseases. At the same time, the question remains open: is this condition a consequence or a cause of the progression of the disease? In this review, we consider the role of the development of mitochondrial dysfunction in the progression of HIV (human immunodeficiency viruses) infection and the onset of AIDS (acquired immunodeficiency syndrome), as well as the direct impact of HIV on mitochondria. In addition, we will touch upon such an important issue as the effect of ART (Antiretroviral Therapy) drugs on mitochondria, since ART is currently the only effective way to curb the progression of HIV in infected patients, and because the identification of potential side effects can help to more consciously approach the development of new drugs in the treatment of HIV infection.
Nanocomposite Au/Si Cantilevers for Tip-Enhanced Raman Scattering (TERS) Sensors
Authors: Slekiene Nora , Snitka Valentinas
Published: April 2023

In this study, we proposed and tested different procedures for the preparation of Au/Si cantilevers for Tip-enhanced Raman spectroscopy (TERS). The preparation of Au/Si TERS sensors was based on three methods: chemical (electroless) deposition, thermal evaporation of Au on the tip of commercially available cantilevers in a vacuum, and electrochemical etching of Au microwires. We fabricated and tested four types of TERS probes, and then used these probes for TERS measurements using graphene oxide (GO) as the target analyte. The probe tips were characterized using scanning electron microscopy (SEM). This article presents a comparative analysis of the fabrication methods, quality of the obtained probe tips, and enhancement factors (EFs) for the four types of TERS cantilevers (probes) produced by chemical deposition, sputtering, and electrochemical methods.
Antimonene-Modified Screen-Printed Carbon Nanofibers Electrode for Enhanced Electroanalytical Response of Metal Ions
Authors: Tapia María , Pérez-Ràfols Clara , Oliveira Filipa , Gusmão Rui , Serrano Núria , Sofer Zdeněk , Díaz-Cruz José
Published: April 2023

A two-dimensional (2D) Sb-modified screen-printed carbon nanofibers electrode (2D Sbexf-SPCNFE) was developed to improve the stripping voltammetric determination of Cd(II) and Pb(II), taking advantage of the synergistic effect between the two nanomaterials. The surface morphology of the 2D Sbexf-SPCNFE was investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Raman spectroscopy. The analytical performance of 2D Sbexf-SPCNFE was compared to those presented by screen-printed carbon electrodes modified with 2D Sbexf (2D Sbexf-SPCE) and the corresponding bare electrodes: screen-printed carbon nanofibers electrode (SPCNFEbare) and screen-printed carbon electrode (SPCEbare). After optimizing the experimental conditions, the 2D Sbexf-SPCNFE exhibited much better analytical parameters compared to the other assessed sensors. Analysis in 0.01 mol L−1 HCl (pH = 2) using 2D Sbexf-SPCNFE showed excellent linear behavior in the concentration range of 2.9 to 85.0 µg L−1 and 0.3 to 82.0 µg L−1 for Cd(II) and Pb(II), respectively. The limits of detection after 240 s deposition time for Cd(II) and Pb(II) were 0.9 and 0.1 µg L−1, and sensitivities between 1.5 and 3 times higher than those displayed by SPCEbare, SPCNFEbare, and 2D Sbexf-SPCE were obtained. Finally, the 2D Sbexf-SPCNFE was successfully applied to the determination of Cd(II) and Pb(II) traces in a certified estuarine water sample.
Association of Sociodemographic Factors and Maternal Educational Attainment with Child Development among Families Living below the Poverty Line in the State of Ceará, Northeastern Brazil
Authors: Rocha Hermano A. L. , Machado Márcia M. T. , Santana Onélia M. M. L. de , Rocha Sabrina G. M. O. , Aquino Camila M. de , Gomes Laécia G. A. , Albuquerque Lucas de S. , Soares Maria D. de A. , Leite Álvaro J. M. , Correia Luciano L. , Sudfeld Christopher R.
Published: April 2023

Maternal educational attainment has been identified as relevant to several child health and development outcomes. This study aimed to evaluate the association of sociodemographic and maternal education factors with child development in families living below the poverty line. A cross-sectional study was conducted through telephone contact from May to July 2021 in Ceará, a state in Northeastern Brazil. The study population comprised families with children up to six years of age participating in the cash transfer program “Mais infância”. The families selected to participate in this program must have a monthly per capita income of less than US$16.50. The Ages and Stages Questionnaire version 3 was applied to assess the children’s development status. The mothers reported maternal educational attainment as the highest grade and or degree obtained. The final weighted and adjusted model showed that maternal schooling was associated with the risk of delay in all domains except for the fine motor domain. The risk of delay in at least one domain was 2.5-fold higher in mothers with a lower level of schooling (95% CI: 1.6–3.9). The findings of this study suggest that mothers with higher educational attainment have children with better child development outcomes.
Impact of High Concentrations of Cellulose Fibers on the Morphology, Durability and Protective Properties of Wood Paint
Authors: Calovi Massimo , Rossi Stefano
Published: April 2023

This work aims to reveal the effect of a high amount of cellulose fibers on the durability and protective behavior of a bio-based wood paint. The influence of the filler on the morphology of the coatings was investigated by scanning electron microscopy observations, while the durability of the paint was evaluated by exposing the samples to UV-B radiation and continuous thermal shocks. Infrared spectroscopy analysis, colorimetric inspections, adhesion tests and scanning electron microscope observations were employed to assess the role of the high concentrations of fillers in affecting the resilience of the acrylic matrix. Moreover, the impact of the filler on the barrier performance of the coatings was estimated using a liquid resistance test and a water uptake test. Finally, the mechanical properties of hardness and abrasion resistance of the layers were evaluated by means of the Buchholz Hardness Indentation test and the Scrub test. Ultimately, this study demonstrates the pros and cons of using large amounts of cellulose fibers as filler in wood paint: the work warns against the excessive use of these fibers, which need a threshold limit so as not to significantly change the coating’s structure and thereby weaken its protective properties.
A Comprehensive Decision Framework for Selecting Distribution Center Locations: A Hybrid Improved Fuzzy SWARA and Fuzzy CRADIS Approach
Authors: Puška Adis , Štilić Anđelka , Stević Željko
Published: April 2023

The focus of this study is on the significance of location in establishing distribution centers. The key question when selecting a location is regarding which location would contribute the most to the growth of a company’s business through the establishment of distribution centers. To answer this question, we conducted research in the Brčko District of BiH in order to determine the best location for a distribution center using expert decision-making based on linguistic values. In order to use these values when selecting locations, a fuzzy set was formed using the IMF SWARA (Improved Fuzzy Stepwise Weight Assessment Ratio Analysis) and fuzzy CRADIS (Compromise Ranking of Alternatives from Distance to the Ideal Solution) methods. The IMF SWARA method was utilized to determine the weights of the criteria, and the fuzzy CRADIS method was employed to rank the locations based on expert ratings. The location for the construction of distribution centers at Bodarište was rated the worst, while the McGowern Base location was rated the best. Based on these findings, the research question was answered, and it was demonstrated that fuzzy methods could be utilized in the selection of distribution center locations. Hence, we recommend that future research be performed on the application of fuzzy methods in the expert selection of potential sites for distribution centers.
Influence of Oxide Dispersions (Al2O3, TiO2, and Y2O3) in CrFeCuMnNi High-Entropy Alloy on Microstructural Changes and Corrosion Resistance
Authors: Sivasankaran Subbarayan , Sherif El-Sayed M. , Ammar Hany R. , Alaboodi Abdulaziz S. , Mekky Abdel-baset H.
Published: April 2023

This study investigates the influence of 3 vol.% Al2O3, 3 vol.% TiO2, and 3 vol.% Y2O3 in the CrFeCuMnNi equimolar high-entropy alloy on its microstructural changes and corrosion resistance. These oxide-dispersed high-entropy composites (ODS-HECs) were synthesized via high-energy ball milling (50 h) followed by uniaxial hot-compaction (550 MPa, 45 min), medium-frequency sintering (1100 °C, 20 min), and hot forging (50 MPa). The microstructures of the developed composites produced a stable FCC phase, a small amount of ordered BCC-B2 structure, Fe2O3, and corresponding dispersed oxide phases. The corrosion of the developed high-entropy composites was tested in 3.5% NaCl solution using several electrochemical techniques. The results revealed that the corrosion rate (RCorr) decreased with the incorporation of oxide particles. Among the investigated samples and based on the electrochemical impedance spectroscopy results, CrFeCuMnNi-3 vol.% TiO2 ODS-HECs were seen to possess the highest value of corrosion resistance (RP). The change in the chronoamperometric current with time indicated that the CrFeCuMnNi alloy suffered pitting corrosion which decreased when Al2O3 was added, forming a CrFeCuMnNi-3 vol.% Al2O3 sample. In contrast, the incorporation of a 3 vol.% Y2O3, and 3 vol. TiO2, prevents pitting.
Linear/Nonlinear Optical Characteristics of ZnO-Doped PVA/PVP Polymeric Films for Electronic and Optical Limiting Applications
Authors: Zyoud Samer H. , AlAbdulaal Thekrayat H. , Almoadi Ali , Alqahtani Mohammed S. , Harraz Farid A. , Al-Assiri Mohammad S. , Yahia Ibrahim S. , Zahran Heba Y. , Mohammed Mervat I. , Abdel-wahab Mohamed Sh.
Published: April 2023

ZnO-doped Polyvinyl alcohol/polyvinyl pyrrolidone (PVA/PVP) polymeric films were prepared in this study through an easy and inexpensive solution-casting method. The scope of the study was based on the structural, dielectric, and optical parameters, as well as on the optical limiting effects of the ZnO-doped polymer blend (PB) as nanocomposite films. The X-ray diffraction (XRD) analysis indicated that the synthesized nanocomposites were semicrystalline. The calculated crystalline size of the polymeric semicrystalline peak decreased as ZnO increased or enhanced the blend polymer. Fourier’s transformer infrared (FT-IR) study confirmed a substantial dispersion of ZnO nanoparticles in a polymeric PVA/PVP matrix. The optical absorption properties suggested focusing on the surface plasmonic peak (SPR). The refractive index values ranged from 1.718 for the pure PB ZnO0 sample in the Hossam, Ibrahim, and Heba model to 3.036 for the PB ZnO5 film from the Anani model. Nonlinear optical parameters (χ((3)), and n(2)) were calculated and analyzed for the PB ZnO nanocomposite films under investigation. The maximum value for χ((1)) was 0.550, while for χ((3)), its susceptibility value was 155.85 × 10−13 esu, and for the nonlinear refractive index (n((2)), it was 20.87 × 10−11 esu. A gradual decrease was revealed in the optical limiting sources, as a high content of ZnO was induced in the blend PVA/PVP polymer. Due to their unique properties, these materials can be used in electronic and optoelectronic devices.
Palaeobiodiversity of Knyszyn Forest (NE Poland) Mires Based on the Late Glacial and Holocene Histories of Vascular Plant Species
Authors: Drzymulska Danuta
Published: April 2023

Peat and lacustrine sediments are a valuable source of knowledge about past biodiversity. Plant macrofossil remains were identified in sediments of mires in northeastern Poland’s Knyszyn Forest. Among them, the remains of species currently absent in this area, such as Potamogeton pusillus, P. friesii, P. filiformis, Myriophyllum alterniflorum, and Cladium mariscus, have been found. In addition, the history of Betula humilis and its possible correlations with another species of bush birch—Betula nana—were of interest. Radiocarbon dating allowed the presence of the studied species to be placed within a time frame, and it was thus established that aquatic species existed in the area under study during the Late Glacial and the turn of the Holocene. Cladium mariscus occurred during the Greenlandian and Meghalayan stages of the Holocene and then became intolerant of habitat changes that occurred. The coexistence of two species of birch known to exist since the Late Glacial was interrupted in the Northgrippian. B. nana, then disappeared from the area, and B. humilis continued to occur as it was more resistant to the changing environmental conditions. It must be emphasized, however, that these conclusions were made possible by the researchers’ access to undisturbed deposits. The mires present in the area of study remain in good condition, providing important and relevant materials for palaeoecological research.
Towards Sustainable European Agriculture? Assessing the EU’s Progress in Limiting the Negative Ecological Effects of Agriculture on Aquatic Environments
Authors: Helepciuc Florența-Elena , Todor Arpad , Bîrsan Constantin-Ciprian , Mitoi Monica-Elena
Published: April 2023

The degradation of terrestrial and aquatic environments has significant adverse effects on biodiversity and environmental sustainability. The ever-increasing population and constant economic growth strain various ecosystems’ resistance and resilience. An important factor that negatively influences terrestrial and aquatic ecosystems is the use of products used in crop management. In this article, we analyze the pesticide-related European Directives and the Nationals Action Plans (NAP) regarding the sustainable use of pesticides and other documents evaluating the NAPs implementation. We assess the first and second-generation NAPs of nine EU Member States (MS)’ to evaluate if we can identify a significant shift in managing the adverse effects of pesticide use on aquatic environments. Furthermore, we evaluate the degree to which these NAPs are synergic with the EU’s strategic approach to soil protection, aquatic environments, and biodiversity.
Amphibians of Rwanda: Diversity, Community Features, and Conservation Status
Authors: Dehling J. Maximilian , Sinsch Ulrich
Published: April 2023

The diversity and distribution of the amphibians in Rwanda was critically reviewed to provide a reliable species inventory for informed conservation management. The checklist of the amphibian species of Rwanda is based on results of our own fieldwork, historical records compiled from the literature, and examination of voucher specimens in museum collections. A total of 62 species are recorded, and 22 further species listed in field guides and open-access data bases are discussed, identified as erroneous records, and consequently not included in the country list. We provide diagnostic characters of external morphology and the advertisement call for each validated species, and a short synopsis of geographic distribution, altitudinal range, occurrence in the provinces of Rwanda, and habitat preference. We provide keys to all genera, and all taxonomically described species based on morphological characters and additional keys based on features of the advertisement calls. We discuss features of amphibian communities including local community structure and delimitation of altitudinal metacommunities. Based on the IUCN red list assessment and our field surveys, we propose for the first time a national red list of amphibians in Rwanda.
Coronary Syndromes and High-Altitude Exposure—A Comprehensive Review
Authors: Macovei Liviu , Macovei Carmen Mirela , Macovei Dragos Cristian
Published: April 2023

The aim of this review is to identify a preventive strategy in order to minimize the risk of adverse events in patients with coronary syndromes and acute exposure to high-altitude. For this purpose we searched the electronic database of PubMed, EMBASE, and Web of Science for studies published in the last 30 years in this field. The conclusions of this review are: patients with stable coronary artery disease on optimal treatment and in a good physical condition can tolerate traveling to high altitude up to 3500 m; on the other hand, patients with unstable angina or recent myocardial infarction no older than 6 months should take less interest in hiking or any activity involving high altitude. Air-traveling is contraindicated for patients with myocardial infarction within previous 2 weeks, angioplasty or intracoronary stent placement within previous 2 weeks, and unstable angina or coronary artery bypass grafting within previous 3 weeks. The main trigger for sudden cardiac death is the lack of gradual acclimatization to high-altitude and to the exercise activity, and the most important risk factor is prior myocardial infarction.
Students Satisfaction with Online Higher Education during the COVID-19 Pandemic
Authors: Arsenijević Jasmina , Belousova Alla , Tushnova Yulia
Published: April 2023

The digital educational environment is not new in the modern world, but in the context of the COVID-19 pandemic, the transition to online learning has become necessary and fast. This offered the possibility to study various characteristics of objects and subjects in the digital educational environment. During the pandemic, universities worldwide were forced to switch to online learning, creating a global educational experiment with results to be comprehended and theoretically reflected upon. The significance of this scientific reflection is important for understanding the characteristics and factors that influence student satisfaction with online learning, as well as for anticipating possible ways to improve its effectiveness. This research aimed to study the characteristics of satisfaction with online learning during the COVID-19 pandemic in connection with the elements of the Community of Inquiry (CoI) online learning model. The study involved 808 students (M = 22.5, SD = 2.4 (53.3% men)) from 6 countries (Serbia—30.8%, Bosnia and Herzegovina—8.5%, Croatia—8.9%, Romania—21.8%, Russia—25.2%, Slovenija—4.7%). A total of 808 students responded to a questionnaire measuring the levels of cognitive, social, and teaching presence in distance learning. Satisfaction with online learning has been shown to positively correlate with cognitive, social and teaching presence, and overall CoI presence. The results of the Kruskal-Wallis test showed that satisfaction with online learning does not differ among students with different levels of academic performance; however, the subjective assessment of the element of social presence “Tools and platforms for online learning allow students to work with each other” is significantly higher among students with low academic performance. Satisfaction with online learning and the elements of the CoI model is different in study groups with varying degrees of online learning presence, as well as different in students whose training included different elements of online learning. The conclusions obtained in this study will make it possible to organize the digital educational environment more effectively by managing the elements of the CoI model.
Unsupervised Forgery Detection of Documents: A Network-Inspired Approach
Authors: Al-Ameri Mohammed Abdulbasit Ali , Mahmood Basim , Ciylan Bünyamin , Amged Alaa
Published: April 2023

The area of forgery detection of documents is considered an active field of research in digital forensics. One of the most common issues that investigators struggle with is circled around the selection of the approach in terms of accuracy, complexity, cost, and ease of use. The literature includes many approaches that are based on either image processing techniques or spectrums analysis. However, most of the available approaches have issues related to complexity and accuracy. This article suggests an unsupervised forgery detection framework that utilizes the correlations among the spectrums of documents’ matters in generating a weighted network for the tested documents. The network, then, is clustered using several unsupervised clustering algorithms. The detection rate is measured according to the number of network clusters. Based on the obtained results, our approach provides high accuracy using the Louvain clustering algorithms, while the use of the updated version of the DBSAN was more successful when testing many documents at the same time. Additionally, the suggested framework is considered simple to implement and does not require professional knowledge to use.
Federated Learning for Medical Imaging Segmentation via Dynamic Aggregation on Non-IID Data Silos
Authors: Yang Liuyan , He Juanjuan , Fu Yue , Luo Zilin
Published: April 2023

A large number of mobile devices, smart wearable devices, and medical and health sensors continue to generate massive amounts of data, making edge devices’ data explode and making it possible to implement data-driven artificial intelligence. However, the “data silos” and other issues still exist and need to be solved. Fortunately, federated learning (FL) can deal with “data silos” in the medical field, facilitating collaborative learning across multiple institutions without sharing local data and avoiding user concerns about data privacy. However, it encounters two main challenges in the medical field. One is statistical heterogeneity, also known as non-IID (non-independent and identically distributed) data, i.e., data being non-IID between clients, which leads to model drift. The second is limited labeling because labels are hard to obtain due to the high cost and expertise requirement. Most existing federated learning algorithms only allow for supervised training settings. In this work, we proposed a novel federated learning framework, MixFedGAN, to tackle the above issues in federated networks with dynamic aggregation and knowledge distillation. A dynamic aggregation scheme was designed to reduce the impact of current low-performing clients and improve stability. Knowledge distillation was introduced into the local generator model with a new distillation regularization loss function to prevent essential parameters of the global generator model from significantly changing. In addition, we considered two scenarios under this framework: complete annotated data and limited labeled data. An experimental analysis on four heterogeneous COVID-19 infection segmentation datasets and three heterogeneous prostate MRI segmentation datasets verified the effectiveness of the proposed federated learning method.
Comparison of Standalone and Hybrid Machine Learning Models for Prediction of Critical Heat Flux in Vertical Tubes
Authors: Khalid Rehan Zubair , Ullah Atta , Khan Asifullah , Khan Afrasyab , Inayat Mansoor Hameed
Published: April 2023

Critical heat flux (CHF) is an essential parameter that plays a significant role in ensuring the safety and economic efficiency of nuclear power facilities. It imposes design and operational restrictions on nuclear power plants due to safety concerns. Therefore, accurate prediction of CHF using a hybrid framework can assist researchers in optimizing system performance, mitigating risk of equipment failure, and enhancing safety measures. Despite the existence of numerous prediction methods, there remains a lack of agreement regarding the underlying mechanism that gives rise to CHF. Hence, developing a precise and reliable CHF model is a crucial and challenging task. In this study, we proposed a hybrid model based on an artificial neural network (ANN) to improve the prediction accuracy of CHF. Our model leverages the available knowledge from a lookup table (LUT) and then employs ANN to further reduce the gap between actual and predicted outcomes. To develop and assess the accuracy of our model, we compiled a dataset of around 5877 data points from various sources in the literature. This dataset encompasses a diverse range of operating parameters for two-phase flow in vertical tubes. The results of this study demonstrate that the proposed hybrid model performs better than standalone machine learning models such as ANN, random forest, support vector machine, and data-driven lookup tables, with a relative root-mean-square error (rRMSE) of only 9.3%. We also evaluated the performance of the proposed hybrid model using holdout and cross-validation techniques, which demonstrated its robustness. Moreover, the proposed approach offers valuable insights into the significance of various input parameters in predicting CHF. Our proposed system can be utilized as a real-time monitoring tool for predicting extreme conditions in nuclear reactors, ensuring their safe and efficient operation.
Escope: An Energy Efficiency Simulator for Internet Data Centers
Authors: Liu Jun , Yan Longchuan , Yan Chengxu , Qiu Yeliang , Jiang Congfeng , Li Yang , Li Yan , Cérin Christophe
Published: April 2023

Contemporary megawatt-scale data centers have emerged to meet the increasing demand for online cloud services and big data analytics. However, in such large-scale data centers, servers of different generations are installed gradually year by year, making the data center heterogeneous in computing capability and energy efficiency. Furthermore, due to different processor architectures, complex and diverse load dynamic changing, business coupling, and other reasons, operators pay great attention to processor hardware power consumption and server aggregation energy efficiency. Therefore, the simulation and analysis of the energy efficiency characteristics of data center servers under different processor architectures can help operators understand the energy efficiency characteristics of data centers and make the optimal task scheduling strategy. This is very beneficial for improving the energy efficiency of the production system and the entire data center. The Escope simulator designed in this study can simulate the online quantity (placement strategy) of different types of servers in the data center and the optimal operating range of the servers. The purpose of this is to analyze the energy efficiency characteristics of all servers in the data center and provide data center operators with the energy efficiency and energy proportionality characteristics of different servers, improve server utilization, and perform reasonable scheduling. Through the simulation experiment of Escope, it can be proved that running the server at the highest energy efficiency point or running the server under full load cannot improve the energy efficiency of the entire data center. The simulation algorithm provided by Escope can select the optimal set of servers and their corresponding utilization. Escope can set up a variety of simulation strategies, and data center operators can simulate data center energy efficiency according to their own needs. Escope can also calculate the power cost savings of introducing new servers in the data center, which provides an essential reference for operators to purchase servers and design data centers.
Effects of Liquid Density on the Gas-Liquid Interaction of the Ionic Liquid Compressor for Hydrogen Storage
Authors: Guo Yi , Wang Qi , Geng Maofei , Peng Xueyuan , Feng Jianmei
Published: April 2023

As a new and promising compression technology for hydrogen gas, the ionic liquid compressor inherits the advantages of the ionic liquid and the hydraulic system. The liquid density is one of the key parameters influencing the fluid flow field, the sloshing of the bulk liquid, and the movement of droplets generated during the compressor operation. An appropriate selection of the liquid density is important for the compressor design, which would improve the thermodynamic performance of the compressor. However, the density of the ionic liquid varied significantly depending on the specific combination of the cation and anions. This paper proposed the methodology to select the optimal liquid density used in the ionic liquid compressor for hydrogen storage. The gas-liquid interaction in the compression chamber is analysed through numerical simulations under varied liquid density values. Results found that the increase in the liquid density promoted the detachment of the ionic liquid from the cylinder cover during the suction procedure and the contact of the bulk liquid on the compressor cover when the gas is compressed in the cylinder during the compression procedure. Both the droplet size and the dimension of the derived gas vortex decreased when the liquid density increased. The lowest mass transfer of hydrogen through the outlet was obtained at the density of 1150 kg/m3. The density of the ionic liquid from 1300 to 1450 kg/m3 is suggested to the hydrogen compressor, taking into account the transient two-phase flow characteristics, the mass transfer, and the total turbulent kinetic energy.
Analytical Modeling, Analysis and Diagnosis of External Rotor PMSM with Stator Winding Unbalance Fault
Authors: Belkhadir Ahmed , Pusca Remus , Belkhayat Driss , Romary Raphaël , Zidani Youssef
Published: April 2023

Multiple factors and consequences may lead to a stator winding fault in an external rotor permanent magnet synchronous motor that can unleash a complete system shutdown and impair performance and motor reliability. This type of fault causes disturbances in operation if it is not recognized and detected in time, since it might lead to catastrophic consequences. In particular, an external rotor permanent magnet synchronous motor has disadvantages in terms of fault tolerance. Consequently, the distribution of the air-gap flux density will no longer be uniform, producing fault harmonics. However, a crucial step of diagnosis and controlling the system condition is to develop an accurate model of the machine with a lack of turns in the stator winding. This paper presents an analytical model of the stator winding unbalance fault represented by lack of turns. Here, mathematical approaches are used by introducing a stator winding parameter for the analytical modeling of the faulty machine. This model can be employed to determine the various quantities of the machine under different fault levels, including the magnetomotive force, the flux density in the air-gap, the flux generated by the stator winding, the stator inductances, and the electromagnetic torque. On this basis, a corresponding link between the fault level and its signature is established. The feasibility and efficiency of the analytical approach are validated by finite element analysis and experimental implementation.
The Nexus between Agriculture, Water, Energy and Environmental Degradation in Central Asia—Empirical Evidence Using Panel Data Models
Authors: Saidmamatov Olimjon , Tetreault Nicolas , Bekjanov Dilmurad , Khodjaniyazov Elbek , Ibadullaev Ergash , Sobirov Yuldoshboy , Adrianto Lugas Raka
Published: April 2023

The primary aspiration of this paper is to learn about the effects of economic growth, energy consumption, agriculture and irrigation water consumption and agriculture productivity on environmental pollution in five countries of Central Asia. The data cover the period from 1992 to 2020 by applying panel data models, namely the Panel FMOLS, Panel DOLS and Panel ARDL-PMG approaches. The results indicate that there is a positive long-term impact of economic growth, water productivity, energy consumption and electricity production on CO2 emissions while agriculture value added and trade openness have a negative and statistically significant influence on CO2 emissions in Central Asia. Country specific short-run coefficients from Panel ARDL reveal that energy consumption is the main driver for rise in the level of CO2 emissions in the countries under the study. Indeed, country level analysis generates unique nexus correlation among agriculture, energy and environmental degradation in each country of Central Asia.
Reduction in CO2 Emissions with Bivalent Heat Pump Systems
Authors: Buday Tamás , Buday-Bódi Erika
Published: April 2023

Utilizing heat pumps has varied benefits, including decreasing the proportion of fossil fuels in the energy mix and reducing CO2 emissions compared with other heating modes. However, this effect greatly depends on the type of external energy and the type of the applied heat pump system. In our study, two different types of heat pumps, three different modes of operation, three different types of auxiliary energy, and three different CO2 emission values from electricity generation were selected to calculate the CO2 emissions related to heating a theoretical house and calculate the CO2 emissions reduction compared with gas firing. According to the calculations, a wide range of CO2 emission reductions can be achieved, from scenarios where there is no reduction to scenarios where the reduction is 94.7% in monovalent mode. When operating in a bivalent mode, the values are less favorable, and several systems show no reduction, particularly when operating in an alternate mode at a bivalent temperature of 2 °C. However, the reduction in fossil CO2 emissions can be kept at a high value (up to 56.7% with Hungary’s electricity mix) in a bivalent system by using biomass as a resource of auxiliary energy and geothermal heat pumps, which is very similar to the CO2 emission reduction in monovalent systems (54.1%).
Effects of Exogenous ALA on Leaf Photosynthesis, Photosynthate Transport, and Sugar Accumulation in Prunus persica L.
Authors: Liang Ruolin , Wang Liangju , Wang Xinqing , Zhang Jianting , Gan Xing
Published: April 2023

Peaches/nectarines (Prunus persica L.) are widely cultivated worldwide. As with other species, the sugar content is the most important trait for fruit quality, especially for precocious cultivars. Most fruits need to improve their sugar content in order to be more profitable under fierce market competition. 5-Aminolevulinic acid (ALA), a naturally occurring δ-amino acid, has been shown to improve leaf photosynthesis and fruit quality, especially sugar content. However, the mechanisms are not clear. The objective of this study is to determine the effects of exogenous ALA on leaf photosynthesis, assimilate transport, and sugar accumulation during fruit development. We used the field-cultivated precocious nectarine ‘Zhongyoutao 4’ and potted cultivated peach ‘Zhongai 33’ as materials, whereas in the second experiment, we used 14C radiolabeling to trace 14C fixation in leaves, transport in branches, and distribution in different organs. The results showed that ALA significantly enhanced the photosynthetic gas exchange capacity, and the effects were maintained for at least one month. The results of the 14C radiolabel experiment showed that ALA enhanced 14C fixation in leaves, promoted the transport to fruits, and reduced the allocation rate of young leaves. This suggests that ALA enlarges “source” volume and strengthens “sink” competition; therefore, assimilate translocation to fruits is promoted. It was observed that sucrose contributed the main saccharide for peach fruit quality at maturity, which might not be converted from glucose or fructose but from starch degradation. ALA improved starch accumulation in the young fruits as well as degradation during maturity. The RT-qPCR showed that the expression of most genes involved in sugar metabolism did not correlate or even negatively correlate with fruit sucrose content. However, the expressions of SWEET1/6/7/8/15/16/17 were highly correlated with the sucrose content, and exogenous ALA treatment up-regulated the gene expression at fruit maturity, suggesting they might play an important role in fruit sugar accumulation. These results provide important theoretical support for ALA application in fruit quality improvement, as well as a regulatory mechanism study on sugar accumulation in fruits.