The increase in the number of resolved genomes has made the traditional taxonomy of species antiquated. With phylogeny-based methods, taxonomies are being updated and refined. Although such methods bridge the gap between phylogeny and taxonomy, phylogeny-based taxonomy currently lacks interactive visualization approaches. Motivated by enriching and increasing the consistency of evolutionary and taxonomic studies alike, we propose Context-Aware Phylogenetic Trees (CAPT) as an interactive web tool to support users in exploration- and validation-based tasks. To complement phylogenetic information with phylogeny-based taxonomy, we offer linking two interactive visualizations which compose two simultaneous views: the phylogenetic tree view and the taxonomic icicle view. Thanks to its space-filling properties, the icicle visualization follows the intuition behind taxonomies where different hierarchical rankings with equal number of child elements can be represented with same-sized rectangular areas. In other words, it provides partitions of different sizes depending on the number of elements they contain. The icicle view integrates seven taxonomic rankings: domain, phylum, class, order, family, genus, and species. CAPT enriches the clades in the phylogenetic tree view with context from the genomic data and supports interactive techniques such as linking and brushing to highlight correspondence between the two views. Four different use cases, extracted from the Genome Taxonomy DataBase, were employed to create four scenarios using our approach. CAPT was successfully used to explore the phylogenetic trees as well as the taxonomic data by providing context and using the interaction techniques. This tool is essential to increase the accuracy of categorization of newly identified species and validate updated taxonomies. The source code and data are freely available at  Common Descent, which describes the notion that the entire species descended from one common ancestor, and as a result, they are all related  to evaluate CAPT. They follow the scope of the GTDB and include the domain categories of Archaea and Bacteria.A sensitivity analysis was carried out to evaluate the performance of CAPT. It consisted of calculating the average time needed to draw the icicle visualization given different numbers of selections excluding or including data preprocessing. On average, ten selected species on a phylogenetic tree required about 1.2 and 3.5 ms when excluding and including data preprocessing, respectively. CAPT was successfully used to explore the phylogenetic trees defined in the use cases as well as the associated taxonomic context. This tool is essential to increase the accuracy of categorization of newly identified species and validate updated taxonomies.The availability of large numbers of complete genomic sequences has influenced the historical practice of taxonomy. The use of morphology and physical characteristics to determine a taxonomic category of species has been repeatedly criticized because genes provide more reliable information than phenotypes for understanding evolutionary relationships. In this section, we present related work on the taxonomic computational methods currently used, taxonomy visualization methods, and hierarchical visualization methods.The identification of a species category and assignment have long relied on morphological and physical traits. Thanks to the genomics era, it is possible today to establish a more reliable understanding of evolutionary relationships and obtain genome-derived or phylogeny-based taxonomies . Driven There are currently two main methods for the taxonomy of species: 16s rRNA gene sequencing and the Average Nucleotide Identity (ANI). The first method examines the relative position of a genome to other species by relying on the 16s rRNA gene . The 16sAlthough current efforts at taxonomic categorization have made serious progress, it should be noted that phylogeny-based taxonomy relies on inferring phylogenies. Indeed, the use of multiple genes to infer species phylogenies is favored. Moreover, it is recognized that a gain in accuracy is sometimes accompanied by the reinforcement of certain systematic biases. This is particularly relevant when incorrect partitions and phylogenies have spuriously high bootstrap support .Due to the diversity of methods and approaches to alternative taxonomic classification, taxonomy is a highly controversial topic. In this context, visualization of taxonomy is essential to facilitate revision work, and as such, should provide both an overview and details of large datasets .Most related work has preferred to present the result of taxonomy analysis using tree-based visualizations, including classification trees and node-link tree diagrams . In the Three major methods address taxonomy visualization: the HIerarchical CLAssification System or HICLAS was introduced to tackle the incompatibility of phylogenetic trees by adopting the logic of classification trees , the taxVisualization facilitates the visual inspection and understanding of a given data . HierarcThe classical node-link tree diagram has been mostly used to represent simple hierarchical structures. As aforementioned, SpaceTree leveraged this classical structure with zooming functionality to improve the user’s focus. However, because of its inefficient use of space, a node-link diagram is not preferred when large data are considered. The authors represented the total number of child nodes that do not fit in the screen by a triangular symbol under the corresponding parent node; its size encoding said total . Many otTree-maps take advantage of the total provided display space by mapping the hierarchical data to a rectangular area . A numbeTo provide a context-aware phylogenetic tree given a set of species, this work requires two data sets. The first includes the species and their distances to the common ancestors to create the phylogenetic tree view. The second data set lists the entire taxonomy of the species to create the icicle view. The materials section details certain criteria and assumptions on which the input data relies and the four different use cases. The former are taken from the Genome Taxonomy DataBase (GTDB). The latter follow the scope of the GTDB and include the domain categories of Archaea and Bacteria.The Genome Taxonomy Database (GTDB) with the release tag 202 is chosen as the source for the input data. It provides an ongoing census of bacterial and archaeal diversity through a phylogenetically consistent, rank normalized, and complete genome-based taxonomy . AlthougThe genomic sequences included in GTDB are mostly extracted from the National Center for Biotechnology Information (NCBI). This genomic dataset includes 254,090 bacterial genomes and 4,316 archaeal genomes. In order to eliminate low-quality genomic sequences, seven criteria are considered : the comKtedonobacter racemifer has 11% contamination. Yet, it still passes the related criterion and is accepted as a legitimate representative of the class Ktedonobacteria in the phylum Chloroflexota.Although these seven criteria can be adjusted for the genomic sequences with high taxonomic or nomenclature importance, low-quality genomes may be preserved due to their significance although they fail one or more criteria. For example, the isolate genome bac120_<r202>.tree. The archaeal reference tree is based on the concatenated alignment of 122 archaeal genes. The available tree is calculated under the Posterior Mean Site Frequency (PMSF) model  model . It encoF) model . The corThe internal nodes and the leaf nodes of these phylogenetic trees are annotated using the GTDB and the genomic accession numbers, respectively . Each troperational species definition that allows automatic assignment of genomes to species. This makes it possible to create species clusters from the huge genomic datasets available. In this regard, whole-genome ANI is accepted as a robust technique commonly applied. It allows the assignment of genomic sequences to representative GTDB genomes. The specific methods and criteria used in this process are briefly explained.Notable achievements of the GTDB include the creation of an First, the genomes are evaluated by considering the aforementioned genomic criteria. Low-quality genomes are removed. The representative genomes are detected and assigned to the named species. In principle, all named species also meet the genomic criteria. The selection of the representative genomes follows one of the six metadata criteria: the type strain genomes of the species, the assembled genomes of NCBI from type material, the NCBI reference or representative genomes, the genomes collected from the type strain of subspecies, the NCBI Metadata and the ANI result between the genomes, or the manual investigation. A noteworthy criterion is the type strain of the species. It is the most used criterion for the selection of representative genomes.Second, the ANI and the Alignment Fraction (AF) are the two methods applied to delineate species clusters. AF represents the percentage of the shared orthologous regions between two genomes. The ANI delineation radius for each representative species is set to 95%. However, if two representative species have an ANI greater than 95%, the defined value is adjusted to up to 97% of the ANI. Species representatives with an ANI greater than 97% are considered synonymous. The non-representative genomes are subsequently assigned to the representative species genomes to form the species clusters. In this regard, if a non-representative genome is within the ANI delineation radius of the nearest representative genome and meets the 65% AF criterion, it is assigned to that representative genome.de novo clusters. To select representative genomes, a greedy clustering algorithm is used and high-quality genomes are chosen as representative. The remaining non-representative genomes are then assigned to representative genomes considering the 65% AF criterion as in the case of named species clusters.Third and last, the remaining genomes that cannot be assigned to any named species are arranged into To demonstrate the relevance and performance evaluation of CAPT, four use cases are created. Two cases are taken from each domain: Archaea and Bacteria. By default, CAPT is available for download with all use cases. Data selections are made on the basis of reference trees provided by the GTDB and are further refined by decreasing the number of species considered and their corresponding accession numbers. The use cases include these selections as subsets of the original data to make them tractable. From the Archaea domain, the first couple of use cases comprises the class Methanomicrobia and the phylum Hadarchaeota. From the Bacteria domain, the second comprises the family Actinomycetaceae and the family Schwanellacea. We briefly detail each use case below.Methanomicrobia contains the species that belong to the methanogenic Archaea group. The energy metabolism of these microorganisms consists of consuming carbon dioxide and producing methane. Organisms from this class play an important role in the global carbon cycle .Hadarcheaota is a small phylum that contains organisms from the subsurface ecosystem. The metabolism of these organisms allows them to succeed in such environments thanks to genes involved in the oxidation of carbon monoxide and dihydrogen, with a potential coupling to the reduction of nitrite to ammonia. Earlier named Hadesarchaea , the GDTActinomycetaceae is a family of bacteria classified in the phylum Actinobacteriota (Actinobacteria), which contains organisms from terrestrial or aquatic environments. These include gram-positive bacteria, whose cell wall consists of a thick layer of peptidoglycan .Schwanellaceae is a family of bacteria classified in the phylum Proteobacteria. They comprise gram-negative bacteria, whose cell wall consists of a thin layer of peptidoglycan. Some members of Geobacteriaceae and Schwanellaceae have been considered as part of microbial fuel cells. They include metal-reducing bacteria, some of which have special membrane-bound cytochromes that can transfer electrons .To complement phylogenetic information with phylogeny-based taxonomy, we offer linking two interactive visualizations which compose two simultaneous views: the phylogenetic tree view and the taxonomic icicle view. The proposed Context-Aware Phylogenetic Trees (CAPT) is an interactive web tool that supports users in exploration- and validation-based tasks. This section follows the nested model of visualization as a scaffold to systematically think about the design space. It details the domain, data and task abstractions, workflow, visual and interaction idioms, algorithm, and sensitivity analysis .The domain situation describes the context of a visualization and often includes domain-specific terms. Phylogenetic studies aim to provide a comprehensive understanding of species lineages. That is, to examine the evolution of species or the process of change over time, in which entities diverge from a pre-existing organism (common ancestor). Phylogenetic trees are the most widely used visualization technique for showing evolutionary relationships between species. In these tree structures, the temporal aspect is represented by the use of different branch lengths, where longer times correspond to longer branches. The increase in the amount of genomic data available has affected the practice of taxonomy. In this regard, taxonomic classification has begun to be recovered from phylogeny to ensure consistent categorization. Motivated by the important role that such taxonomy plays in analyzing the evolution of entities through hierarchies, it is essential to provide taxonomic information to phylogenetic trees. This phylogeny-based taxonomy not only contributes to the consistency of biological analyses performed in phylogenetics but also strengthens the hypotheses formulated during the study of the evolution of organisms as well as the categorization of newly emerged species.The data abstraction refers to what is shown to the user. The abstract vocabulary avoids domain-specific terms and refers to a translation process. In this work, two data abstractions are considered for the two views: the phylogenetic tree and the taxonomic icicle.The phylogenetic tree view relies on the input data  and its associated metadata . The data abstraction is a node-link diagram or tree. The leaf nodes of the diagram are represented by text labels for species. The internal nodes represent the common ancestors of the species. The branches represent the estimated evolutionary times for the species.The taxonomic icicle view is based on the main taxonomic ranks: domain, phylum, class, order, family, genus, and species. These ranks correspond to a qualitative variable in which the categories of the variable are not described by numbers but by verbal groupings. Since there is no order between the example categories in a rank, they follow the nominal scale. For example, the taxa Acidobacteria, Firmicutes, and Proteobacteria represent different unordered categories in the phylum rank. However, the defined taxonomic ranks follow a seven-level hierarchical structure. To generalize the domain problem, the taxonomic ranks can be considered as categorical nominal data belonging to the different levels of said hierarchy. Levels of the hierarchy are depicted as adjacent rectangular areas. The categories are located in the relevant area of the icicle view based on the level they belong to. Each area varies depending on the number of elements present in a given grouping. Compared to other visualizations, the icicle visualization is more efficient. For example, when nodes are located at different hierarchical levels, the corresponding rectangular areas of the different hierarchical ranks are not nested within each other, as is the case with a tree map visualization. In addition, the icicle allows size comparisons at each level of a given hierarchy, as opposed to a node-link diagram. Moreover, evaluation studies have shown that while icicle use space less efficiently than sunburst diagrams, the hierarchy is easier to perceive.The task abstraction refers to why the user is looking at the visualization. To support the user in their tasks, different action and target pairs are made possible for both views. The actions include analyzing , searching , and querying .The phylogenetic tree view makes use of the analyzing action to examine how long species took to evolve through time and discover from which common ancestor they did. Presenting a phylogenetic tree with selection functionalities, including a Region Of Interest or an ROI, permits users to derive the taxonomic context for one or more selected species.The taxonomic icicle view makes use of analyzing, searching, and querying. By default, a taxonomic icicle view is created for all the species in a phylogenetic tree view. The user may examine the resulting icicle visualization to discover the area size occupied by different taxa. By relying on the mouse click event, users can search the taxonomic path of a selected taxon. Identifying a taxonomic path of interest is task-dependent. Moreover, since it is possible to download each resulting icicle, users can compare the taxonomic rankings of different taxa or even species.The link and brush functionality binds both views . This supports searching actions to lookup (taxonomic rank and species known) and locate (taxonomic rank unknown but species known) across both views.CAPT follows the rule of thirds to display the two views side-by-side. By default, thirty percent of the page width is reserved for the phylogenetic tree view, while the rest is allocated for the taxonomic icicle view.The user may start by either selecting data from the existing use cases, or uploading a tree file in the Newick format. In the latter case, this assumes that the assembly accession numbers are included in the uploaded tree. This enables automatic labeling of the leaf nodes. For instance, the GTDB relies on these accession numbers to label the phylogenetic reference trees and to differentiate the species in the taxonomy. Then, the user can proceed to select one or more species by using the click-and-drag event to draw a rectangular ROI. Once a selection is made, users may specify the domain of the taxonomy, and then a taxonomic view is created. The latter depends on a match between the selected species and a taxonomic domain. When a match is possible and falls under the GTDB taxonomy data of Archaea and Bacteria, the taxonomic icicle view is rendered. This workflow is visualized as a workflow diagram in The phylogenetic tree view comprises three important parts: tree upload, tree, and area selections.The tree upload consists of uploading a tree file that meets three criteria: 1. the structure of the tree has to be encoded using the Newick format, 2. the species have to be labeled with the assembly accession numbers that the GTDB uses rather than their names, and 3. the file has to follow the UTF-8 text file format encoding. Once the file upload action is complete, the user can create the phylogenetic tree view as seen in The tree selection consists of selecting one of the four integrated use cases . They are extracted from the reference trees of the GTDB. The use cases are ready examples that enable users to examine the utility of CAPT for exploration- and validation-based tasks. Their integration in the user interface is displayed in The area selection provides users with a click-and-drag interaction to draw rectangular shapes over the phylogenetic tree view. It relies on the phylotree JavaScript package . To obtaThe resulting assembly accession numbers are then used to retrieve the species taxonomy and create a taxonomic icicle view.The taxonomic icicle view comprises seven important parts: domain selection, partition, label, color, the tool-tip on mouseover event, the mouse click event in the icicle, and the export of an icicle visualization.Select Domain button from a dropdown menu with two choices: Archaea or Bacteria. The chosen domain name has to correspond to the domain of the examined species within the selected phylogenetic tree view. Upon selecting the wrong domain, a warning popup box is displayed to inform the user. If a domain is incorrectly selected, the user’s selection in the phylogenetic tree is retained without the need to start over.The domain selection is selected using the To create an icicle visualization, the partition layout is applied to the defined size of a Scalable Vector Graphics or SVG file format. The hierarchical layout relies on the D3 JavaScript package . It creaEach rectangular area of the icicle visualization is labeled with its corresponding taxa name. The font and font size are inherited from the phylogenetic tree for a consistent display across views. To increase readability, the species labels are displayed diagonally or rotated at a 45-degree angle; outside the rectangular areas. By following the nomenclature rule, species names include their genus taxon name. Due to the lengthy textual information, the labels of family and genus ranks are displayed vertically or rotated at a 90-degree angle. All other labels are displayed horizontally.The color encodings are chosen based on the seven taxonomic ranks. Hence, the icicle visualization has seven layers. Due to the hierarchical nature of the data, a sequential color palette is preferred. To create it, we relied on the ten simple rules to colorize biological data visualization . The bluThe tool-tip on the mouseover event introduces focus and clarity whenever the user requires further information. The tool-tip includes three attributes: the name, the id, and the size. The id refers to the species. Upon a mouseover event atop a label of a rectangle, the tool-tip is displayed. By default, the tool-tip is displayed on the left of a label. This guarantees that the tool-tip is never outside of the screen bounds if the mouse cursor is close to the screen edge (on the right). The examined species is colored in the complementary orange #B56521 of the blue #2171B5 (domain). To provide phylogenetic and taxonomic context for the examined species, a link and brush functionality connects both views using the color channel. The examined species is colored orange #B56521 simultaneously in the phylogenetic tree and in the taxonomic icicle view, respectively.The mouse click event in the icicle visualization supports search actions . Upon clicking on a rectangular area of the icicle, the icicle visualization is updated and a smaller icicle is rendered, showing the taxon of interest. The mouse click event filters the path of the selected taxon to include all the taxonomic ranks between the highest rank of the domain and the rank of the selection. To return to the initial icicle, before filtering, the user clicks on the same or any other rank of interest in the current icicle. Consistent color encodings are used throughout the icicle navigation; c. f., Export button. This saves an SVG file of the current icicle.Exporting the icicle visualization is possible by clicking on the To provide the context to the phylogenetic tree or a selection comprising a subset of species, an algorithm is implemented to retrieve the taxonomy of the selected species from the associated taxonomic data. This relies on a matching function between the selected species in the phylogenetic tree view and the taxonomy data. The central part of this function is shown below; where one element corresponds to one species.n and m the selected elements size length and the selected domain array size, the inner loop executes m times whenever the outer one performs an iteration. This results in an n*m in total. The time complexity to obtain the taxonomy data of n species from the phylogenetic tree view is O (n*m). Since the required space increases with respect to the array size with n elements, the space complexity is linear O (n). Upon a successful match, this returns the selected species with their seven taxa as separate JavaScript objects. The grouping starts at the species rank and iterates until all ranks have been visited, saving the grouping as a child to the rank above. Further attributes are added for each object: the size and the depth. A before and after example is provided in Indeed, the number of iterations in the inner for loop is independent of the outer one. Given A sensitivity analysis is performed to evaluate the time required to draw the icicle visualization for a different number of selected species; five scenarios or data selections are created. Two experiments are considered. First, the data processing, including the algorithm and the drawing of the icicle visualization. Second, only the drawing of the visualization. For each experiment, the average elapsed time and the standard deviation are calculated for 1,000 runs. This totals 10,000 runs. To examine the computational complexity, regression models are fitted to the results. The data used for the sensitivity analysis is the use case from the Methanomicrobia class. Time measurement is performed using the Performance APIhttps://github.com/ghattab/CAPT. Sample results for the use cases are given below. In addition, the results of the sensitivity analysis and the fitting of the regression model are presented in detail.With the help of interactive techniques such as brushing and linking techniques in side-by-side views, our tool guarantees constant frame rates. CAPT is well suited for exploration and validation-based tasks in phylogeny-based taxonomy. The source code and the four use cases are available at https://capt.mathematik.uni-marburg.de/.The selection of an area in a phylogenetic tree view and the subsequent creation of the taxonomic icicle view was depicted using the class Methanomicrobia in CAPT was benchmarked by evaluating the time required to draw the icicle visualization without and with the implemented algorithm. The sensitivity analysis investigated the time required to draw the icicle visualization for different numbers of species in an ROI. Regression model fitting confirmed the linear relationship between the number of selected nodes or species in the phylogenetic tree view and the time required to draw the icicle visualization in the taxonomic icicle view. Several points are worth discussing. As technological advances push the boundaries of what is possible, future demand aligns with more integrative tools that facilitate multiple views, provide context, and dynamically link technological and conceptual aspects. Indeed, the influence of the increasing amount of genomic data on the practice of biological taxonomy is evident. Although CAPT introduces a practical solution while working in phylogeny-based taxonomy, certain points require further consideration.Future versions of the tool should include certain interaction techniques that enable view-specific enrichment of the phylogenetic tree view. For example, the addition of phylogeny-specific metrics such as the bootstrap value. Moreover, Species names are problematic and a source of continuous discussion in the world of taxonomy. The authors preferred to rely on the genomic accession numbers as they constitute a reliable data attribute. Although more reliable, they constitute a problem for easy interpretability and correspondence to species names. Conceptually, this requires the user to define a focus area to differentiate the represented species in the phylogenetic tree view from the accession numbers. The combination of the ROI and the tool-tip functionalities helps alleviate this problem and decrease the conceptual distance between phylogeny and taxonomy.The provided use cases served as a starting point. Many studies could have benefited from using our tool to support exploration or validation tasks in various contexts. For example, CAPT presupposes phylogenetic tree data with explicit species names and their genomic accession numbers. Indeed, the process of amending a phylogenetic tree with these accession numbers can prove time-consuming. Given a large phylogenetic tree, further efforts are required to develop semi- or fully-automated enrichment approaches.Although various interactive functionalities are implemented for the taxonomic icicle view, further improvements are possible such as fitting the scale of the icicle visualization. Considering user-settable zoom-in functionalities may improve readability and user-based customization. This includes a reset button to revert to a default scale. To parallel the addition of the bootstrap value and the number of individual genes supporting an inferred clade in a phylogenetic tree view, further details may be added in the taxonomic icicle view. For instance, in the tool-tip, the exact ANI and AF results of each species’ genomic sequence may be reported.The icicle visualization is an efficient solution as it enables size comparisons at each level of a given hierarchy. However, when very large phylogenetic tree data is imported, and their taxonomic icicle view is created; an under-resolved icicle visualization results. Indeed, an increase in the number of selected species decreases the number of pixels allocated for the rectangular areas in the icicle at the species layer. The aforementioned zoom-in functionality could prove useful with the currently implemented SVG file format. Moreover, with large phylogenetic trees, labeling the icicle visualization also becomes problematic. This is because the names of the taxa are often quite long. Future possible improvements may involve user-defined regular expressions to simplify a label set.CAPT meets many technological and design requirements. It facilitates the creation and visualization of a phylogeny-based taxonomy and provides taxonomic context. Moreover, CAPT could be used to visually compare the quality of different taxonomies made available by different databases for one phylogeny of interest. Overall, this work provides a tool with state-of-the-art performance and a useful set of functionalities for phylogeny-based taxonomy visualization.


Electro-oculography (EOG)-based brain–computer interface (BCI) is a relevant technology influencing physical medicine, daily life, gaming and even the aeronautics field. EOG-based BCI systems record activity related to users’ intention, perception and motor decisions. It converts the bio-physiological signals into commands for external hardware, and it executes the operation expected by the user through the output device. EOG signal is used for identifying and classifying eye movements through active or passive interaction. Both types of interaction have the potential for controlling the output device by performing the user’s communication with the environment. In the aeronautical field, investigations of EOG-BCI systems are being explored as a relevant tool to replace the manual command and as a communicative tool dedicated to accelerating the user’s intention. This paper reviews the last two decades of EOG-based BCI studies and provides a structured design space with a large set of representative papers. Our purpose is to introduce the existing BCI systems based on EOG signals and to inspire the design of new ones. First, we highlight the basic components of EOG-based BCI studies, including EOG signal acquisition, EOG device particularity, extracted features, translation algorithms, and interaction commands. Second, we provide an overview of EOG-based BCI applications in the real and virtual environment along with the aeronautical application. We conclude with a discussion of the actual limits of EOG devices regarding existing systems. Finally, we provide suggestions to gain insight for future design inquiries. Human-computer dialogue has hinged upon input from manual devices  and relies on the visual display—until today. Despite being “ready to deliver the promises” to enhance human–computer interaction for about 20 years now , eye-traA power-efficient alternative to eye tracking is the application of electrodes on the scalp and face surface known as electro-oculography (EOG). The use of the EOG system was one of the first techniques to analyze eye movements , and it This paper presents a non-exhaustive review of studies published between the years 2000 and 2020 that are based on the EOG eye movement’s interaction in human models. This review provides a precious time- and resource-saving guidebook to exploring the EOG interaction tendency for the last two decades, making it relevant of interest for EOG novices as well for specialists. We included 112 English peer-reviewed journal articles and conference papers that met the inclusion criteria and were published in PubMed, the Institute of Electrical and Electronics Engineers (IEEE), or the Association for Computing Machinery (ACM) digital library. The particularity of the used devices, the extracted features, the category of the algorithms and the nature of the interaction (passive or active) of each study have been emphasized in the The eye is an important source of the relevant information associated with the user’s activities and cognitive functions. It can be modeled as an electrical dipole (between the retina and the cornea) that follows eye movements. If we place two electrodes near two eyes’ corners and two electrodes on the top and bottom of one eye, there will be a voltage difference between the vertical and horizontal electrodes, which is known as the EOG signal. When the eyeball moves in the direction of the electrode, the electrical potential increases, and if the eye moves in the other direction, the electrical potential decreases. The EOG signal is a measure of the corneal–retinal potential difference with signal amplitude ranging 15–200 ntal one ,7,8.Interestingly, EOG signals can be obtained using cheap and simple electrodes. Generally, horizontal electrodes are placed on the outer boundary of the eye, while vertical electrodes are placed above and below the eye. The reference electrode is often positioned on the forehead . Other aThere are different EOG devices found across our literature review and which are summarized in the (i)The standard EOG consisted of the placement of two electrodes at the left and right corners of the participant’s eyes to measure the horizontal movement. Two other electrodes were placed up and down of one eye to obtain the vertical movement. A ground electrode was positioned on AFz  and the reference electrode was positioned on the right or left earlobe [(ii)The alternative EOG mounting represented an uncommon position of surface electrodes such as around the ears. Manabe et al.  placed f(iii)The J!NS MEME glasses  employs 3-point stainless steel EOG electrodes on the nose bridge and IMU, battery, and Bluetooth units on the eyeglasses temples. The J!NS MEME are not a common computing interface but rather a sensing device. They stream the data from the sensor to smartphones or laptops via Bluetooth. The sensor data corresponds to vertical and horizontal EOG signal, accelerometer and gyroscope data. The equipment has an operating time of 8 hours. It allows a long duration of real-time streaming of eye and head movements. The J!NS MEME are unobtrusive and look like ordinary glasses.(iv)The customized EOG device category presents the mounted system elaborated by the experimental group according to their objectives. Here we introduce a brief presentation of each customized device included in this review. Vehkaoja et al.  used a pEOG signal is commonly used as a human–computer interface tool to control signals  and playp < 0.0001. To extract EOG features, Pournamdar et al. [Feature extraction methods and analysis of EOG artifacts are one the most important challenges in this field. The study of Aungsakul et al.  evaluater et al.  exploredVidal et al.  developeThe number and quality of the signal extracted features are affected by the degree of freedom of the end effector. For instance, controlling a computer mouse or robotic arm needs 2 to 4 degrees of freedom , while aFeature extraction allows obtaining an optimal subset of elements to classify a selection of collected data according to the criterion functions. Nowadays, an important number of robust and flexible classification algorithms have been developed to recognize and classify the extracted features from EOG signals.n samples before), To classify the EOG signal extracted from the eye movements, several algorithms are often used to identify the eye movements classification including saccades, blinks, fixations, smooth pursuits and artifacts removal. EOG signal data are predominantly detected in low-frequency bands. Generally, the band-pass filter ranging from 0.1 to 30 Hz with a sampling rate of 128 Hz is performed. After that, a moving average filter is used to eliminate the existing noise components. The eye movements classification is based on an algorithm that computes the derivative of the EOG signal. The EOG derivative is measured through the amplitude value of the EOG signal. Two values are needed, one representing the previous value of the amplitude  .An important number of algorithms were designed and employed in several studies to classify eye movement signals. Each decoding algorithm is unique to each BCI and needs to be adaptable to new users, and can self-calibrate. EOG mutual adaptation of “user-to-system and system-to-user” is unique to BCI. The k-nearest neighbors’ algorithm is particularly selected in brain–computer interface investigation for its relevant outcomes. It is one of the simplest and most efficient algorithms for the classification of samples. The procedure requires firstly detecting the k parameter (corresponding to the number of neighbors). After that, the distance of the unknown sample is designed with all known samples. When the samples are categorized according to their distance and value of k, the class that has the majority of nearest samples is chosen as the class of unknown samples (L. Pan 2015). One of the several versions of this algorithm is called random sub-sampling .The Time Delay Neural Network is another dynamic network that classifies EOG signals. The input delay feedforward feedback neural network is a time-delay neural network, and its hidden and output neurons will be copied over the entire time. The delay is computed from top to bottom, so the network has a tapped delay line, which can connect the current signal, the previous signal and the delayed signal to the network weight matrix through the delay time unit . To identify the eye patterns, the Time Delay Neural Network replicated the former activation at each step and updated the outgoing connection with the original unit. These units are coupled to the next layer called the receiving field. The Time Delay Neural Network uses the Levenberg backpropagation training algorithm where the samples are normalized from 0 to 1 with a binary normalization algorithm .Other algorithms contain filtering, feature extraction, training and actual event detection stages to detect eye movements. The minimum redundancy and maximum relevance algorithm allows the number of features to be reduced by selecting the most relevant ones. Clearness Based Feature Selection calculates the distance between the target sample and the center of each category and then compares the class of the nearest center with the class of the objective sample . The eyeThe central role of BCI systems is to transduce the neural signal from the brain into signals understandable by an external piece of hardware. The interface implements direct communication access between the brain and the device to be controlled. The EOG system has the potential to create active or passive user interaction with the environment. The interaction based on EOG is explored in an important number of applications, including eye writing commands , eye movThe nature of the user interaction depends on the target and the field of application including rehabilitation , virtual reality, response to physical stimuli , or identification of brain states . The EOG similar to other BCI systems, allows the user to interact and control different environments and actions, such as computer function , mobility conduction  and daily environmental manipulation . Interestingly, EOG can be explored as a BCI tool for the therapeutic purpose to rehabilitate normal visual sensory system control by generating activity-dependent neural plasticity.Vidal et al.  suggesteKangas et al.  analyzedEOG is being studied as BCI for virtual and augmented reality, particularly in the case of gaming, rehabilitation, or for training and evaluation of motion, image-based decoding ,141. KumIn addition, the importance of the EOG-based HCI for interaction in a virtual reality environment concerns the following points: Firstly, the EOG-based HCI hardware system is effortless and wearable. Then, the EOG-based HCI presents gratifying efficacy. Third, several virtual reality applications might be applied through the EOG-based HCI. A prominent method of virtual reality interaction is gesture tracking which includes two types: optical tracking  and the sensors positioned on the hand  . AlthougIn the aviation field, it is known that errors related to sleepiness and fatigue in the cockpit lead to fatal accidents . Even inOne advantage of EOG-based interaction is that the light conditions have only little effect on the EOG signal, which is principally important for mobile recording such in daily life or even in extreme environments. Contrary to video-based eye-tracking, EOG assessments do not require light to come into the eyes to trigger the electrical potential. EOG measurement can be realized in obscurity or even with closed eyes. Due to this feature, EOG is particularly used for eye movement measurements during normal  and pathAnother potential benefit of EOG for application in aviation domain is the light-weight computational analysis. It is not based on complex video and image processing. Therefore, EOG-based interaction can be commonly used in a laboratory environment , as wellAlthough EOG-based BCI systems have made important advances in exploring eye movement signals for interactions, the methods show some complications with an important number of applied operations. A limitation of the conventional EOG-based BCI paradigm is that the operators may be willing to adjust the eye movements for few seconds by fixing the gaze at an accurate position. When compared with video-based tracking, EOG has the limitation to be based on the around-eyes electrodes that are attached to the skin. EOG signal generates a simple waveform, a linear correlation with eye movement and it produces a considerable signal-to-noise ratio. Furthermore, EOG delivers worse spatial point of gaze tracking accuracy so it is more suitable for relative eye movements’ analysis. EOG signals are also susceptible to artifacts and drifting, mainly when recorded with a mobile system. Similar to other physiological signals, EOG signals are often corrupted by noise from the electrical activity of the body, electrodes, residential power lines, measuring circuits and other interference physiological sources. In addition, similar to EEG, EOG suffers from poor spatial resolution such can be obtained from other neuroimaging techniques. Contrary to eye-tracking systems using videos based on infrared cameras, the EOG-based BCI systems do not use complementary systems. However, the EOG requires the operator’s voluntary movement of eyeballs. Therefore, it is complicated for participants with oculomotor impairments to guide their eyeballs during a basic psychological paradigm such as the orientation of their attention in the direction of a sound source. Finally, EOG data, such as general data processing, deserves specific care before being analysed. As an initial step, data cleaning must be applied with a signal detrending. To do so, a bandwidth filtering can be applied. This will remove high frequency noise but also the continuous component of the signal. Since EOG signal have low voltage amplitude, they are very sensitive to external electrical context. For this reason, extra filtering is usually recommenced with the standard electrical frequency wave removal (50 or 60 Hz). Next, artefacts such as blinks, or parts of the signal that cannot be analysed have to be removed. For instance, when the user speaks, the activation of the jaw muscles spoils the signals and generally resulting into altered collected data. Other data processing stages may be required depending of the recording context and we only give here the most general ones.The use of the EOG signal is emerging as one of the most successfully explored bioelectric signals in the BCI domain, and this review showed an increasing interest over the last 5 years. We included 112 relevant studies after the screening of PubMed, ACM DL and IEEE Xplore databases. We presented the results as an overview table according to four design space dimensions: used device, features extracted from the signal, algorithm used for features computation and designed signal-based interaction. We also compared the trends in studies’ distribution per 5-year period. The results showed that the most used electrode placement is the standard scheme, but there is a recent increasing interest in using an off-the-shelf product that allows using EOG technology without wires or sticky electrodes setup. The majority of studies use blinks and saccades as features without any particular trend over the last years. The most popular detection algorithms are the linear ones due to their ease of use for real-time applications. The results of the designed interaction show that while early studies investigated the general passive activity recognition application, recent studies tended to design EOG-based keyboard-like interactions. Eventually, the most popular interaction is for actions of confirmation, selection and pointing.We also presented the EOG based on BCI applications in the real and virtual environments along with the aeronautical application. Finally, we exposed the limits of the EOG devices regarding existing systems and user perspectives regarding BCI technology. We conclude that almost all the designed EOG systems are highly promising in terms of performance and do not require heavy signal processing and complex pattern recognition algorithms such as those used with other systems as EEG. Nevertheless, most of the EOG-based BCI systems are still based more on theoretical rather than practical models and are suffering from the lack of concrete practice, particularly mobile EOG. Mobile EOG-based BCI systems are considered a relatively new research topic. An important number of investigations should be carried out to explore innovative protocols with mobile interaction control. An efficient system should constantly strive to improve speed and accuracy to eliminate the operator’s frustration and to enable a stable performance level. In addition, the new-generation models may continually take into consideration the user experience, which may reduce the physical and mental stress.


Across two experiments, native Greek speakers are found to prefer for each anticausative verb either non-active or active voice morphological marking, in the presence or absence of explicit contextual information. It is also shown experimentally that native speakers prefer an interpretation that involves a specific cause for all anticausatives, especially when the existence of such a cause is favored by the contextual setting. Our empirical findings are consistent with the view that the Voice Phrase that is realized as non-active voice morphology in Greek anticausatives is expletive. From a theoretical perspective, we analyze the expletiveness of this Voice projection as the result of semantic redundancy: the Voice head of Greek anticausatives combines with a  EspeciaIn the framework of On the other hand, active voice marking (2a) may correspond to two different structures: (i) the projection of an active VoiceP that does project a specifier and appears in transitive construals (4), or (ii) the absence of a VoiceP altogether, in the case of unaccusatives for instance (5).Regarding specifically anticausative verbs, via the optionality of the projection of a (non-active) VoiceP.Under the morphology-syntax mapping adopted by The question is readily raised whether the three morphological and/or syntactic classes of anticausative verbs are also mapped onto different meanings. Concretely put, do anticausatives of one class receive a systematically different interpretation from anticausatives of the other classes? And in the same vein, what is the interpretation of voice in Greek anticausatives? There are two ways to address these questions: either by comparing the meaning of Class A and Class B verbs (projection of a VoiceP in a verb X vs. non-projection of VoiceP in a verb Y), or by comparing Class C anticausative minimal pairs .endelos ‘completely’, while their non-actively marked counterparts are not:Researchers interested in the topic have mostly followed the latter alternative. gremistike in (9b)] can convey either partial or complete change of state, while the ones bearing active voice morphology receive only partial-change interpretation [hence the ill-formedness of (9a)].The authors take the contrast to suggest that morphologically non-active Class C verbs  and the inferred absence of such an initiator for the same change of state.On the other hand, our participants provided high saliency ratings in those cases where the information contributed by the interpretation and the context matched: cause interpretations under overt cause contexts and no cause interpretations under non-overt cause contexts. Crucially, the preference for the no cause interpretation in non-overt cause contexts was significantly lower than the preference for the cause interpretation in overt cause contexts. This result cannot be explained under the assumption that the speakers’ saliency ratings were exclusively based on the interaction between context and interpretation. Instead, it can be accounted for if a causative semantics for both active and non-active Greek anticausatives, independently argued for in the literature , is adopUnder the view that the saliency ratings represented in Summing up the discussion so far, our experimental findings can be compressed into the three empirical generalizations that follow: (i) Class C of Greek anticausatives is not productive; the majority of alternating verbs falls either into Class A or Class B. (ii) The speakers’ preference for active or non-active voice marking on Greek anticausatives does not depend on the presence of some explicitly stated external initiator in the contextual setting. (iii) Native Greek speakers prefer to semantically compute/accommodate a cause when interpreting anticausative events , especially whenever the provided context and interpretation match.The question raised next is how these generalizations relate to the theory of Greek anticausatives. In this sense, we next examine what they tell us about the hypothesis made in the literature  accordinOur empirical generalizations (i) and (ii) suggest that the so-called Class C is not an appropriate contrast field on which to pursue some specific meaning ascription to the voice of Greek anticausatives. Researchers attempting to do that have compared the actively and the non-actively marked anticausative variant of the same verb in different syntactic or interpretative contexts. However, we got evidence that speakers most usually prefer clearly one of the two variants. We further found that, even if they accepted both, context cannot affect or determine the choice between one variant or the other.It seems, then, that Greek grammar gives speakers two options in forming an anticausative: either to mark the verb with active voice morphology or to mark it with non-active voice morphology. Whether an alternating verb falls in the scope of the former or the latter grammatical rule appears to be something that needs to be learnt by those acquiring/learning the language see also .16 The vWe should note that the experimental results related to our control items can also be viewed as evidence pointing to the expletiveness direction. We remind the reader that our controls, in both experiments, involved 10 pairs of synonymous anticausative verbs, each pair consisting of one Class A verb, that was marked with non-active voice morphology, and one Class B verb, that was morphologically marked as active. When comparing the ratings given to the members of each pair (see the Results section 2.3.1.1), this synonymy was experimentally supported for 7 out of the 10 pairs tested. The very existence of synonymy across the morphologically distinct anticausative Classes A and B points toward the view that anticausative Voice does not affect the truth-conditional meaning of the sentences in which the verb appears and, thus, the expletive status of anticausative Voice are strengthened by our findings.In a recent study on expletiveness across several functional categories, vPs, as represented in (19b); those that are marked with non-active voice morphology further project a non-active VoiceP lacking a specifier above vP, as shown in (20b).Let us adopt for our discussion the main aspects of the syntactic account by vP level in both actively and non-actively marked anticausatives, the interpretation is one of a causative event, because v has a causative flavor. Crucially, this is in accordance with our experimental finding that, regardless of voice morphology, speakers interpret/accommodate a cause for anticausatives  , where 〈v, not by unspecified information attributed to the verbal root  The so-called Class C of Greek anticausative verbs is not productive; for the majority of alternating verbs, speakers have a clear preference for either the anticausative variant that bears active voice morphology (Class B) or the variant that displays non-active voice morphology (Class A). (ii) The speakers’ preference for either form of the anticausative verb is not significantly affected or determined by the presence/absence of a linguistically phrased external initiator bringing about the described change of state. (iii) Regardless of voice morphology, speakers tend to interpret/accommodate a cause when faced with anticausative event descriptions, provided that the information surrounding the event description is not contradictory  and the Generalitat de Catalunya (2021SGR00787).The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


The COVID-19 pandemic has highlighted the vulnerability of countries worldwide and their abilities to cope with the fast-paced demands of the research and medical community. A key to promoting ethical decision-making frameworks is by calibrating the sustainability at regional, national, and global levels to incorporate coordinated reforms. We performed a sustained ethical analysis and critically reviewed evidence addressing country-level responses to practices during the COVID-19 pandemic using PubMed (MEDLINE), Scopus, and CINAHL. The World Health Organization’s ethical framework proposed for the entire population during the pandemic was applied to thematically delineate findings under equality, best outcomes (utility), prioritizing the worst off, and prioritizing those tasked with helping others. The findings demarcate ethical concerns about the validity of drug and vaccine trials in developing and developed countries, hints of unjust healthcare organizational policies, lack of equal allocation of pertinent resources, miscalculated allocation of resources to essential workers and stratified populations. The COVID-19 pandemic exposed the vulnerability of countries globally and their ability to cope with the ensuing responses fast-paced demands of the research and medical community.The contextual considerations are perspective given different principles and values are determining ethical considerations. COVID-19 vaccines, once ready for public use, given to high-risk populations such as health care workers, and the elderly are justified. However, the allocation of a scarce protective resource may be distributed randomly within a high-risk subgroup if the assumption supports equal benefits within the predetermined sub-group. The ethical considerations for a case-by-case basis in the use of another limited protective resource might differ such as the use of ventilators in the COVID-19 pandemic. Practical applications of ethical analysis and recommendations by the BC COVID-19 Ethical Decision-Making Framework (EDMF): Interim guidance is tied in sustainable responses at regional, national, and global scales to incorporate coordinated reforms.To address the gaps in the literature, a systematic-sustained ethical analysis was deemed appropriate to synthesize and integrate relevant literature with a lack of comprehensive understanding of the research questions. The review aimed to recognize the extent, burden, and gaps in the existing literature to guide future research and practices. The following keywords were used: COVID AND ethic*. We included any study addressing ethics during COVID-19, and did not omit studies if they were qualitative. Studies published in PubMed (MEDLINE), Scopus, and CINAHL full text from January 1, 2020, until December 31, 2020, were included. Articles focused on public health and ethical frameworks for analysis were considered relevant for our review with special consideration given to literature catering to low and middle-income countries. The framework proposed by the World Health Organization is tied in with those who require priority access to scarce resources amid the pandemic.In principle, every person’s interest concerning healthcare services or resource allocation is pertinent during the COVID-19 or any other disease outbreak, unless there are reasons to justify a differential prioritization of existing or potential resources. Equality may be the most suited guide to allocating scarce resources among populations or individuals who may have the same benefit from the given resource. For example, ventilators among those patients who have similar clinical indications for yielding benefit.The principle is used to reason with the allocation of resources based on their capacity and to maximize the most benefit while reducing the harm. For example, resources may be used to save more lives at that time-point. This may be the most appropriate guide to allocating resources to recipients that will have different benefits among different individuals. For example, ventilators will be expected to derive maximum benefit among patients who are relatively healthier as opposed to those that are more than likely to outweigh all benefits.The principle has ambivalent views. In our review, we will attempt to justify the allocation of resources to those that have the highest medical need or those who are the highest risk. It is an appropriate guide to allocate resources and protect those at risk. For example, the provision of personal protective equipment (PPE) for healthcare workers or those who most require the provision of drugs given a short supply for those who require them most urgently.The principle is used to ensure that resources are allocated to those that have certain talents or skills and who have talents to save others, or because resources are owed to them due to them participating in helping others. This is the most imperative principle to guide the allocation of resources to first responders or health care workers.The review analyzed the ethical concerns and challenges identified in the literature to identify the ethical practices pertinent to the COVID-19 response. A search of academic literature was conducted to address the following questions:(1) How have countries incorporated ethical practices in their COVID-19 pandemic response?(2) What is to be learned for the COVID-19 pandemic as well as future epidemics and pandemics?Three databases including PubMed, Scopus, and CINAHL full text were searched with a total of 2,124 results. We identified 15 papers for review including around less than half (n=7) studies reported on the country-specific ethical practices concerning the validity of conducting drug and vaccine trials in developing countries, and government-wide ethically just policies . Over haTo our understanding this is the first study to analyse ethical practices in a sustained and analytical manner during the era of COVID-19, particularly with implications for Pakistan. Studies show ethical concerns about the validity of drug and vaccine trials in developing and developed countries, hints of unjust healthcare organizational policies, the lack of equal allocation of pertinent resources, miscalculated allocation of resources to essential workers and stratified populations.The role of governments in managing the pandemic is critical. Guidelines for the ethical practice of healthcare need to evolve as facts about COVID-19 progression and spread unfold. Consejo de Salubridad General (CSG) of the Government of Mexico posted two versions of guidelines regarding the allocation of health resources. Both versions promoted the distribution of resources based on equity i.e. free from the influence of race, religion, political affiliation, social value, nationality, gender, or race. The first version used age-based criterion derived from the “complete lives” principle based on justice law to triage patients. The criterion was highly criticized as physiological age is not equivalent to chronological age and it undermines the principle of “equal worth of life”. Therefore, the guidelines were revised to include “luck of draw” (by chance) to triage patients with an exception of priority given to healthcare workers involved in the management of COVID-19.An additional challenge to Pakistani doctors and the public is presented by the practice of non-validated telehealth models for patient care. The safety and efficacy of telehealth models have not been established which could lead to a major ethical risk for the healthcare practice based on mitigating damage to patients. The non-validated model increases the risk of litigation for doctors by patients which may result in excessive legal trials leading to decreased efficacy of healthcare and increased economic burden leading to low utilization of resources towards the pandemic. To address the problem, the Italian Government Cabinet reduced the litigation of doctors to “fraud cases” only to meet the demand for extraordinary emergencies. The law implies that healthcare professionals may not be held accountable for involuntary violation of guidelines for COVID-19 emergencies but is expected to follow guidelines in concrete situations. It may allow the continuance of patient care while maximizing the current use of resources towards emergencies rather than litigation charges.Surveillance is an important part of the Covid-19 response to governing the increasing cases. The Indian government established a surveillance program, Aarogya Setu  which uses mobile location for contact tracing. The surveillance method traces contacts via the location data on the phone of the confirmed COVID-19 case and informs contacts in the proximity of the phone.Given the ethical implications of COVID-19, it is important to create valid policies to ensure equitable resource distribution, which requires transparency of information among governing bodies and the public.11The WHO’s policy, “Health for All’’ is adopted by most countries. The Covid-19 pandemic has revealed the loopholes in the ethical practice based on equities e.g. Medicare in Australia does not cover the marginalized refugees and immigrants. In the USA, minorities showed higher rates of COVID-19 infection e.g. African Americans accounted for 50% of all COVID-19 cases in Chicago.To better prepare for pandemics in the future relevant professional bodies in Pakistan representing specialties should prepare guidelines to aid in the management of everything patients to resources. These include guidelines for health care professionals and the individual level and national bodies, unions, and particularly pharmaceuticals due to their influence on health care in high-income countries. Particularly, Pakistan will need guidelines that address challenges that are unique to them and these include far less equipment, staffing shortages, and the probable reality of being the last group to receive vaccines. The pandemic has taught the Pakistani population that a lack of harmony and a non-uniform approach may lead to distrust from patients as multiple treatment paradigms. It is pertinent to promote a single reliable source to provide information to the public.This sustained ethical analysis and systematic review suggests that although far from over, the pandemic has created deep divides in the Pakistani and international societies. The COVID-19 pandemic continues to provide crucial lessons that we must pay heed to if we are to grow a crisis with overarching effect systems and structure. While pandemics tend to burden health care services, they have prompted clinicians to shift from ’patient-centered’ ethics to ’public health’ ethics, the later a concept that few first-world and Pakistani health care professionals are familiar with.AS and ZS conceived, designed, did the data collection, writing and editing of manuscript.MA and HA did the data collection, manuscript writing, and editing of the manuscript.ZS is the guarantor and is accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately reported.


This paper presents a numerical analysis of blood flow in a diseased vessel within the presence of an external magnetic field. The blood flow was considered to be incompressible and fully developed, in that the non-Newtonian nature of the fluid was characterised as a generalised power law model for shear-thinning, Newtonian, and shear-thickening fluids. The impact of a transverse directed external magnetic field on blood flow through a stenosed bifurcated artery was investigated. The arterial geometry was considered as a bifurcated channel with overlapping shaped stenosis. The problem was treated mathematically using the Galerkin Least-Squares (GLS) method. The implementation of this numerical method managed to overcome the numerical instability faced by the classical Galerkin technique when adopted to a highly viscous flow. The benefit of GLS in circumventing the Ladyzhenskaya-Babuška-Brezzi (LBB) condition was utilized by evaluating both the velocity and pressure components at corner nodes of a unstructured triangular element. The non-linearity that emerged from the convective terms was then treated using the Newton-Raphson method, while the numerical integrals were computed using a Gaussian quadrature rule with six quadrature points. The findings obtained from this study were then compared with available results from the literature as well as Comsol multiphysics software to verify the accuracy and validity of the numerical algorithms. It was found that the application of magnetic field was able to overcome flow reversal by 39% for a shear-thinning fluid, 26% for a Newtonian fluid, and 27% for a shear-thickening fluid. The negative pressure and steep wall shear stress which occurs at the extremities of an overlapping stenosis throat were diminished by rise in magnetic intensity. This prevented thrombosis occurrence and produced a uniform calm flow. Cardiovascular diseases have been reported as one of the primary causes of death among humans worldwide by the World Health Organisation (WHO). Due to this, the genesis, diagnosis, and prognosis of this type of vascular disease has become a favoured subject of scientific research all around the world. Atherosclerotic lesion is an arterial disease that is believed to be responsible for cardiovascular system failure . The plaSince blood is a biofluid that is electrical conductive due to the suspension of red blood cells consisting of haemoglobin, which is a form of iron oxide, at a very high concentrations , numerouThe MHD principle can be applied to reduce, block, or speed up blood flow in human blood vessels. Thus, it is convenient as a treatment plan for certain cardiovascular diseases, like haemorrhages and hypertension that accelerate blood flow . The proThe rheological behaviour of blood being considered a non-Newtonian model makes this study more realistic. This is because, within low shear regions, red blood cells are usually found clumped together, forming large particles (rouleaux) , causingBased on the aforementioned research, there is a quite limited number of the studies on bifurcated arteries despite their physical condition, which consists of junctions, curvatures, and branches that are the most common site for atherosclerotic lesion development. The region along the edge of the daughter artery, as well as downstream of the stenotic region, has a high potential to be distracted by flow disturbances in the form of flow reversal and stagnation . The finTo the best of the author’s knowledge, there has been no study on the MHD flow of non-Newtonian blood generalised through the power law model in a bifurcated artery with an arterial constriction at the mother artery in the shape of overlapping in the literature. Hence, in this study, we are interested in the mathematical modelling of the generalised power law fluid model for blood flow through a stenosed bifurcated artery under the action of an externally applied uniform magnetic field. In our previous work , MHD effB0 that was applied in the axial direction. Hence, the governing equations for such flow conserved mass and momentum as follows:ρ is the blood density, x-momentum equation. This term represents the Lorentz force per unit volume, which arises due to the fluid’s electrical conductivity, σ. The parameter B0 indicates magnetic flux intensity, which is applied perpendicularly to the direction of fluid flow. As mentioned before, in this study, we considered the use of the generalised power law model, which is a form of Generalized Newtonian Liquid (GNL) that allows viscosity to vary with shear rate to represent the rheological behaviour of blood flow. According to  stands for the stiffness matrices comprised of the advective and diffusive matrices as well as the incompressibility constraints, and {F} denotes the force vector. To provide clarity the Newton-Raphson method execution was used to solve the two-dimensional, incompressible, steady, and laminar flow of blood subjected to the magnetohydrodynamic effects in the form of U = , respectively. The components for the vector R(U) were later detailed as follows:From Eqs rding to , 41. As ously in  through F12 and F21, which represent the surface integrals of the force vector that is induced naturally from Green’s theorem. These expressions are made of combinations of hydrostatic boundary stress and the total boundary stress  is acquired in the last iteration where the limit as stated in Step (vi) is fulfilled, the iteration will stop. The solution obtained for several important variables such as the wall shear stress, wall pressure, and velocity are visualized graphically. Wall shear stress is the friction that produces a tangential force exerted by the blood flowing across the vessel wall, which is calculated as:As the solution of Numerical validation was performed to validate that the source code developed using Matlab software was properly programmed according to the GLS algorithm. The developed source code was verified through a result comparison of Xenos and Tzirtzilakis  who treaρ = 1050kgm−3 and m = μ = 0.0035kgm−1s−1. For validation purposes, the system of equations governing fluid flow in Comsol Multiphysics and Matlab software were prescribed with boundary conditions for the stated computational domain following the one implemented in [First, a mesh dependency test was performed to ensure the results obtained would have meshed independence. To compute the solutions, the following parameters were used, such that Re = 400, ented in . The flox = 0). As depicted in The results generated from several domain elements were then plotted as shown in u-velocity and location with the one computed in this study. The results were within a satisfactory range, indicating close agreement. Slight differences might have occurred due to differences in mesh sizes, flow unsteadiness, and the use of different methods. On the other hand, the values for pressure drop obtained in this study were found to be in excellent agreement with those reported in [By using the selected meshing, the results obtained for maximum velocity with location and pressure drop are displayed in orted in  as well The results for velocity contours and streamline patterns were also demonstrated for validation. As can be seen from Overall, from the performed numerical validation, the applicability of the developed algorithms was proven. Thus, it was reliable for solving the problems involved in this particular study, which are further discussed in the next section.This research demonstrates a numerical solution for purely viscous blood flow through a bifurcated artery with overlapping shaped stenosis subjected to an external magnetic field. A thorough quantitative analysis of Galerkin least-squares formulation on the stenosed bifurcated artery flow phenomenon was investigated, where the parameters used were adopted from , 37 as:x = 1) was computed using a different domain element numbers, which were 7787, 10352, 13998, 17090, and 28196 as visualised in the present figure. A mesh independence test was conducted to determine the most efficient meshing for computing whole solutions. The results in τ = 0.0001. The results published for this test were computed for a Newtonian flow (n = 1) of blood through a stenosed bifurcated artery with a stenosis height of τm = 0.4a using Reynolds number Re = 300.To confirm that the computed results are independent on the mesh parameters, a mesh independence test was conducted as in the preceding section on the domain of interest, with several mesh numbers as illustrated in n = 1.2 and n = 0.639, respectively. At n = 1, the blood rheology was treated as a Newtonian fluid with a constant fluid viscosity, μ throughout the vessel.As can be seen from x = 1.5) with 40% severity are depicted for Re = 300. The axial velocity profiles for shear-thinning, Newtonian, and shear-thickening fluids exhibited the highest peak velocity in the lowest magnetic field intensity where M was considered to be 4. As the MHD effect with higher intensities of M = 8 were applied to fluid flow, a small drop in the dimensionless axial velocities at the centre of an artery was observed in all fluids. In contrast, with increases in magnetic field intensity, velocity near the arterial wall increased, preventing the formation of flow reversal for all fluids. The shape of the profile attained by the shear-thickening fluid was more parabolic and more restricted towards the negative flow than its shear-thinning and Newtonian fluid counterparts. The shape of the profile attained by the Newtonian flow (n = 1) serves as a transition from the flat shape obtained by the shear-thinning fluid (n = 0.639) to a more parabolic shape shown by the shear-thickening fluid (n = 1.2).As shown in M = 0 to M = 4. All of the curves skewed to the right after passing through a negative flow area that formed in the post-stenotic region of the outer arterial wall. With increased magnetic field intensity, the flow at the daughter branch decelerated appreciably. Misra and Shit [The effects of the Hartmann number on the flow velocity at the daughter branch was studied using different fluid characterisations as illustrated in and Shit  found thand Shit . Besidesand Shit . The preM = 0 and 8. As magnetic field intensity was raised to M = 8, flow reversal decreased. The increase in magnetic field intensity did not significantly change the maximum values for the axial velocity profiles at the centre of this region. Somehow, a significant relationship between magnetic field intensity and axial velocity for the three fluid types was observed at the vicinity of the arterial wall. The application of magnetic fields managed to extensively overcome the formation of flow reversal in the vicinity of the arterial wall. The fluid flow at the centre of the vessel has slightly reduced for the three fluids as magnetic field intensity increased.The relation between the severity of stenosis and magnetic field intensity for different fluids was later clarified by the curves representing the axial velocity profiles across the second throat of stenosis shown in M = 0, 4, and 8. All the curves showed a similar pattern from the arterial’s inlet until the offset of the stenosis, in with the shear-thickening fluid showed higher pressure values than its counterparts. The wall pressure in M = 0 and 4. As a magnetic intensity slightly higher than M = 8 was applied, the fluctuated blood pressure of the shear-thinning fluid was overcome, in that it retained the pressure profile of its counterparts. The lowest wall pressure values for shear-thickening and Newtonian fluid were found at the offset of the overlapping stenosis, indicated by negative values for M = 0, 4, and 8. The shear-thinning fluid exhibited negative values at its lowest peak, which formed at the curvature junction before entering the daughter branch wall for M = 0 and 4. The negative pressure values exerted on the wall, especially the one formed at the stenotic region, might have caused the artery to collapse due to insufficient pressure to support the opening of the arterial lumen.The study of pressure loss is crucial since it can be an indication of adequate blood supply to the organs. Hence, as shown in Similar to Figs Shear stress was the second force component exerted on the wall, which was exhibited by a tangential stress from blood viscosity. The friction between the blood and the vessel wall created a velocity gradient (shear rate) that varied along the arterial wall. The variations in strain rate times the molecular fluid viscidity as calculated in Accurate estimations of wall shear stress distribution are significant for atherosclerosis risk predictions. From the estimated values for this haemodynamic factor, the influence of blood flow through a diseased vessel on endothelial cells can be understood. For instance, low wall shear stress values are the favoured site of atherosclerotic plaque development, while the high shear stress regions that developed in the extremities of the stenosis throat may contribute to platelet activation, which may destroy the vessel wall and contribute to the formation of intimal thickening . High shM = 8 and 12, respectively. With increased magnetic field strengths, a substantial reduction of recirculation zones was noticed, with the largest vortexes being formed at low magnetic field intensities (M = 8). Also, from the comparison between the recirculation zones exhibited by shear-thinning, Newtonian, and shear-thickening fluids at constant magnetic field intensity, it can be seen that the shear-thinning fluid formed longer eddies than its counterparts. The shortest eddies were developed by the shear-thickening fluid with the Newtonian fluid developing eddies with intermediate lengths between the shear-thinning and shear-thickening fluids. This is because the shear-thinning fluid was less viscous at the low shear rate region, thus having a greater velocity, causing the fluid layers to be less attached to the arterial walls. At much higher magnetic intensities (M = 12), it was noticed that the vortex emerging downstream of the stenotic region was significantly reduced in size for the three fluids, producing a uniform calm flow that reduced the risk of thrombosis along the stenotic region.The accumulation of plaque reduced the arterial passage area, complicating the transport of blood across this area through the formation of flow reversal and recirculation zones downstream of the stenosis. In view of this, the nature of streamlines in the presence of a magnetic field at Re = 300 was visualized with velocity contours in Figs Based on the velocity contour, an accelerated flow of blood was developed along the occluded region. It can be clearly observed from the contour colours that the shear-thinning fluid exhibited a larger flow with lower velocity downstream of the stenotic region in the vicinity of the arterial wall compared to the Newtonian and shear-thickening fluids, indicating the occurrence of flow stagnation in that region. Besides, with increased magnetic intensities, each fluid flow at the daughter branches decreased. The drop in blood flow to the daughter branches can lead to an insufficient supply of blood to organs and tissues, which may contribute to worsening individual health. The flow disturbance that predominantly developed at the downstream region of the stenosis on the other hand activated the coagulation system, which resulted in the production of a fibrin-rich tail of thrombus .n according to various blood flow natures of n = 0.639 for shear-thinning fluid, n = 1 for Newtonian fluid, and n = 1.2 for shear-thickening fluid, the effects of different fluids characterisations through a bifurcated artery on blood behaviour was thoroughly examined. This study is particularly applicable to a situation where the arterial lumen of the blood vessel is deposited with plaque, which in this study was modelled as overlapping stenosis. The nonlinear governing equations were solved numerically with the help of the Newton-Raphson method. The results presented from this work show important information regarding the complex behaviour of blood in situations, where the physical parameters M, n, Re and τm play a prominent role in haemodynamic flow subjected to the application of a uniform magnetic field in the transverse direction. The findings from this study on non-Newtonian fluid theory will help in understanding the haemodynamic factors that influence the rheological behaviour of blood flows. The computed results may also provide information on flow disturbances that might develop due to stenosis. This investigation is beneficial for medical practitioners in analysing the impact of magnetic fields on patients during magnetic therapy. This study is also beneficial for the design of future medical devices that utilise magnetic fields. The key findings of the study are based on numerical results reported in the preceding sections:In this study, a numerical simulation of magnetohydrodynamic blood flow through a stenosed bifurcated artery was successfully conducted using the Galerkin least-squares method. By representing the generalised power law index, The rise in Hartmann number will cause the velocity of fluids to decelerate, irrespective of different fluid natures. The axial velocity, which decreases at the centre and increases near the vessel wall will restrict the occurrence of flow reversal. MHD effects are proven to significantly affect the flow velocity at regions with no constriction, rather than regions that possesses a constriction.The rise in Hartmann number and generalised power law index leads to significant drops in pressure. Also, increasing magnetic intensity will improve the negative pressures exerted on walls downstream of the stenotic region, as well as at the constricted region itself for the three fluids.M = 8 to M = 12. The shear-thinning fluid exhibited a larger recirculation area in comparison to the Newtonian and shear-thickening fluids.Recirculation areas were reduced with increases in the Hartmann number, indicated by the percentage reduction in recirculation regions of about 39% for a shear-thinning fluid, 26% for a Newtonian fluid, and 27% for a shear-thickening fluid as magnetic intensity was enhanced from M = 0 to M = 4 contributed to a drop in average flows velocity at the daughter artery by 0.0449, 0.0081 and 0.0011 for the shear-thinning, Newtonian, and shear-thickening fluids, respectively. Whereas, the average velocity for the shear-thinning, Newtonian, and shear-thickening fluids at the second throat of overlapping stenosis located at the parent artery were decreased by 0.0025, 0.0017 and 0.0012, respectively, as M was increased from 0 to 4.The flow disturbances that occurred mostly along the downstream region from the stenosis did have a significant impact on the transport of blood into the daughter branches since fluid velocity dropped appreciably at the daughter branch in comparison to the mother artery. It is worth noting that the enhancement of magnetic intensity from The great wall shear stress in the extremities of an overlapping stenosis throat were reduced with increased magnetic field intensities. The wall shear stress recorded for the shear-thinning fluid was greater than the shear-thickening and Newtonian fluids at all spatial locations except for the downstream region of stenosis prior to the daughter branch. Due to this, this shear-thinning fluid possesses a higher risk of platelets activation, which may induce thrombosis and lead to the worsened or total blockage of blood flow.This matter highlights the importance of using the power law index in blood flow studies to describe various non-Newtonian natures corresponding to the rheological behaviour of blood under diseased conditions. In addition, the consideration of arterial bifurcation as the computational domain in this study was essential since this site is prone to atherosclerosis. The results in this study from the use of the GLS method offers an alternative to the usual FEM in solving shear flow through a complex domain, which have failed to be solved using the standard Galerkin FEM. This method enhances the convergence of solutions without affecting their consistency by introducing a stabilization parameter that is mesh-dependent.