Studying the impact of COVID-19 on the European Air Transportation Network

The European Air Transportation Network was significantly impacted by the COVID-19 pandemic, resulting in an unprecedented loss of flight connections. Utilizing a combination of graph representation learning and time series analysis, this paper studies the evolution of both the global connectivity as well as the structure of the European Air Transportation Network from January 2020 to December 2022. Specifically, it finds strong differences in recovery rates for flights across six different market segments. In terms of network structure, the study finds that structural roles that are present in the pre-covid network have seen a loss in performance over the course of the pandemic, but have recovered to pre-covid levels. Using regional changes in structural roles, this study identifies Italy as the region with the strongest increase and the United Kingdom as the region with the strongest decrease in structural role, finding substantial differences in recovery rates per market segment. Lastly, this study pays special attention on the effect of the Russia-Ukrainian war on the European Air Transportation Network. © 2023 IEEE.

Concern for Self-Health During the COVID-19 Pandemic in Canada: How to Tell an Intersectional Story Using Quantitative Data?

Rooted in Black feminism, intersectionality theory entered critical legal studies and travelled to public health and beyond. This chapter demonstrates one of many ways to apply intersectionality theory using a descriptive intercategorical approach to quantitative data. In so doing, I attempt to tell an intersectional story to make visible the intersectional inequalities for Canadians' concerns for self-health during the first wave of COVID-19 pandemic. For pedagogical purposes, I share a subset of Statistics Canada's COVID-19 Impacts Survey 2020 dataset of 239,143 participants and Stata code to encourage students to practice estimating intersectional outcomes and ask questions to explicate health inequalities. Although interrogating the systems of power is critical, this project does not statistically analyse but draws on the literature to discuss how interacting power structures might shape intersectional peoples' experiences. In addition, the analysed dataset is not representative of the Canadian population. Nonetheless, it might be helpful to showcase a case study on introductory-level quantitative intersectionality research. I hope, despite these limitations, this case study and the pedagogical tools will contribute to greater access to intersectionality research, generating a cadre of intersectionality data translators in public health. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

Women, Work and the COVID-19 Pandemic: Paving the Path Forward

This paper focuses on the pandemic's impact on women's participation in the economy. The author outlines the various barriers to the full and equal participation of women in the Indian economy such as the gender division of labour which requires women to shoulder the burden of unpaid domestic work, the occupational segregation of the labour market, gender-blind development policies, regressive social norms and patriarchal attitudes. The challenge facing women only increased with the pandemic which led to large numbers of women dropping out of the workforce. The author suggests that in the immediate future the State has a crucial role in redressing this injustice. In the longer term, she calls for rethinking the dominant models of development that pursue economic growth and rise in GDP as the panacea for all problems. Such models have given rise to the rampant exploitation of labour, among whom women are the most vulnerable. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023.

VRFlex: Towards the Design of a Virtual Reality Hyflex Class Model

Social distancing requirements urged by the COVID-19 pandemic along with high transportation cost reduced inperson meetings significantly in recent times. In consequence, many people are seeking for virtual reality (VR) to feel a similar experiences of visiting and enjoying places that are unaccessible. VR has immense success in domains, such as automotive industry, healthcare, tourism, entertainment, sports etc. It is observed that traditional online synchronous and asynchronous class structure is not quite effective in engaging students in class participation and discussion. Therefore, we introduce a novel VRbased class structure that will simulate the classroom environment for students participating a class virtually. We equipped the classroom with several internet of things (IoT) devices that collects information from the classroom, analyze those information, and determine some interesting information to display for the students participating the class virtually. We design a classroom prototype and validate the prototype with simulation. The result of the simulation shows that such a VR-based classroom model is feasible and can introduce in classrooms. © 2023 IEEE.

IMPLICATIONS OF POTENTIAL NEW REGULATORY MEASURES TO ADDRESS AVIATION EMISSIONS

This work is an analysis of the implications of the potential new regulatory policies being recently proposed in the European Union, in particular the mandatory blending of SAF (on top of the already existing CORSIA or ETS), to address aviation emissions from a technical, operational and economic perspective. As a continuation of previous work from the Department of Aerospace Systems, Air Transport and Airports from the ETSIAE (Universidad Politécnica de Madrid), the air traffic structure of the European Union in 2019 has been analysed based on publicly available data from EUROCONTROL and EUROSTAT. The output has been used as the reference scenario for the implementation of the mandatory blending of SAF, expected to take over at the beginning of 2025, since it is expected that by then, air traffic will reach the pre-COVID levels. The results show that all the policy options considered so far have uneven impact among the different stakeholders and that before deciding going forward with any of the presented options, extra work needs to be done to overcome the different challenges that would potentially arise. © 2022 ICAS. All Rights Reserved.

Modular Processes and Facilities Enable Flexible Vaccine Manufacturing

The COVID-19 pandemic has accelerated the need for modular designs to rapidly expand vaccine production capacity. Speed to market An established benefit of modular facilities is that they are constructed off-site and then delivered to the site where they will be put into use. CRB's SlateXpace was introduced in September 2020 as a "suitebased" modular facility design for cell and gene therapy. Modular systems enable the manufacturer to produce regionally on the required scale and thus to react flexibly to the current situation and local requirements," says Kappeler.

STRENGTHS AND TRANSFORMABILITY OF HEALTHCARE STRUCTURES IN CAMPANIA

In Italy the Covid-19 pandemic has revealed infrastructural and operational fragilities of the healthcare system, as well as a profound need for building modernization and upgrade as it emerges from the planned investments of the PNRR too. The Campania Region confirms the national trend in terms of consistency and age of the healthcare real estate, in some cases of artistic and cultural interest, which is underused and thus susceptible to possible regeneration. The paper aims at defining a decision support tool to track dimensional and typological parameters of the analyzed buildings and at defining a priority scale of possible enhancement and upgrade interventions. The methodology has three phases: mapping the real estate;defining a potentiality index which links building and urban characteristics to possible transformations;defining a transformability index to describe the predisposition of buildings to undergo interventions. From the cross-reading of the obtained indexes the decision maker can define the best strategy and perspective for a well informed and sustainable regeneration plan. © 2022, Luciano Editore. All rights reserved.

Identification of host factors that bind to the 5 ' end of the MERS-CoV RNA genome

Plain language summaryMERS-CoV is a virus that causes a severe illness in the nose, mouth and throat of humans. It is a zoonotic virus, which means that it can spread from animals to humans. MERS-CoV was first found in Saudi Arabia in 2012 and continues to pose a threat to public health. Interactions between the virus and human cells and proteins are important to establishing infection. Understanding these interactions is important for the development of drugs to treat viral infections. Here, we have identified some proteins that interact with MERS-CoV. Tweetable A proteomic approach for the identification of cellular proteins that interact with the 5 '-terminal region of MERS-CoV RNA genome. #MERS-CoV #RNA_viruses. Aim: The aim of this study was to identify host factors that interact with the 5 ' end of the MERS-CoV RNA genome. Materials & methods: RNA affinity chromatography followed by mass spectrometry analysis was used to identify the binding of host factors in Vero E6 cells. Results: A total of 59 host factors that bound the MERS-CoV RNA genome in non-infected Vero E6 cells were identified. Most of the identified cellular proteins were previously reported to interact with the genome of other RNA viruses. We validated our mass spectrometry results using western blotting. Conclusion: These data enhance our knowledge about the RNA-host interactions of coronaviruses, which could serve as targets for developing antiviral therapeutics against MERS-CoV.

Preface

The title of the ConferenceXXII Conference of PhD Students and Young Scientists "Interdisciplinary topics in mining and geology”The location and the date of the conferencevirtual event – online conference, June 29th to July 1st, 2022 in Wrocław, PolandXXIInd Conference of PhD Students and Young Scientists "Interdisciplinary topics in mining and geology” continues a series of events that started in 2000 at Wrocław University of Science and Technology. Scientific programme of the Conference focuses on four thematic panels:1. Mining Engineering: sustainable development, digitalisation in mining, problems of securing, protecting and using remnants of old mining works, underground mining, opencast mining, mineral processing, waste management, mining machinery, mine transport, economics in mining, mining aeronautics, ventilation and air conditioning in mines,2. Earth and Space Sciences: geology, hydrogeology, environmental protection, extraterrestrial resources, groundwater and medicinal waters, engineering and environmental protection, geotourism,3. Geoengineering: environmental protection, applied geotechnics, rock and soil mechanics, geohazards,4. Geoinformation: mining geodesy, GIS, photogrammetry and remote sensing, geodata modeling and analysis.The XXII Conference of PhD Students and Young Scientists was held as a virtual event, that is as a virtual, online conference in real-time. The reason why the Organizing Committee decided to change the traditional formula of the event to online formula was related to the concern for the health of the participants due to the COVID-19 epidemic.The XXII Conference of PhD Students and Young Scientists took place from June 29th to July 1st, 2022 in Wroclaw, Poland. That is the organizers worked and managed the event from the Wrocław University of Science and Technology Geocentre building. Because the conference focused on four thematic panels, four different special opening lectures were delivered by wellknown scientists- Professor Jan Zalasiewicz (University of Leicester, England)- Associate Professor Artur Krawczyk (AGH University of Science and Technology, Poland)- Professor Biljana Kovacević-Zelić (University of Zagreb, Croatia)- Assistant Professor Eduard Kan (Tashkent Institute of Irrigation and Agricultural Mechanizations Engineers, Uzbekistan).The Conference was divided into 8 oral sessions (with 33 presentations) and 1 poster session (with 33 posters). The amount of time provided to one presentation was 15 minutes, after presentation there was 5 minutes available for discussion. The poster session was available throughout the event, and the posters were available for online viewing on the Conference's website with the possibility of make discussion and ask questions in real time via zoom meeting application as well. Every day of the Conference one "virtual coffee break” was devoted for discussion between participants and question and answer session for the Organizers.There were 96 registered participants from 13 countries. The online XXII Conference of PhD Students and Young Scientists was conducted using the Zoom meeting platform with commemorative screen shots taken. By tradition two competitions, for the best oral presentation and for the best poster were held. The award for the best oral presentation was given ex aequo to Julia Tiganj (TH Georg Agricola University of Applied Sciences, Germany) for the presentation entitled Post-mining goes international: hurdles to climate neutrality using the example of China and Oksana Khomiak, Jörg Benndorf (TU Bergakademie Freiberg, Germany) for the presentation entitled Spectral analysis of ore hyperspectral images at different stages of the mining value chain, whereas the best poster was awarded to Adam Wróblewski, Jacek Wodecki, Paweł Trybała, Radosław Zimroz (Wrocław University of Science and technology, Poland) for the poster entitled Large underground structures geometry evaluation based on point cloud data analysis.List of Scientific Committee, Organizing Committee, Editorial Team are available i this pdf.

Dual-Action Effect of Gallium and Silver Providing Osseointegration and Antibacterial Properties to Calcium Titanate Coatings on Porous Titanium Implants.

Previously, functional coatings on 3D-printed titanium implants were developed to improve their biointegration by separately incorporating Ga and Ag on the biomaterial surface. Now, a thermochemical treatment modification is proposed to study the effect of their simultaneous incorporation. Different concentrations of AgNO3 and Ga(NO3)3 are evaluated, and the obtained surfaces are completely characterized. Ion release, cytotoxicity, and bioactivity studies complement the characterization. The provided antibacterial effect of the surfaces is analyzed, and cell response is assessed by the study of SaOS-2 cell adhesion, proliferation, and differentiation. The Ti surface doping is confirmed by the formation of Ga-containing Ca titanates and nanoparticles of metallic Ag within the titanate coating. The surfaces generated with all combinations of AgNO3 and Ga(NO3)3 concentrations show bioactivity. The bacterial assay confirms a strong bactericidal impact achieved by the effect of both Ga and Ag present on the surface, especially for Pseudomonas aeruginosa, one of the main pathogens involved in orthopedic implant failures. SaOS-2 cells adhere and proliferate on the Ga/Ag-doped Ti surfaces, and the presence of gallium favors cell differentiation. The dual effect of both metallic agents doping the titanium surface provides bioactivity while protecting the biomaterial from the most frequent pathogens in implantology.

Good Architecture Matters: The Architect's Perspective on Design for Ageing and Energy Efficiency

Custom-built solutions for ageing, urban regeneration, energy efficiency, thermal performance, and well-being are contemporary challenges that have prompted considerable research over the past decades. In the construction field, subjects such as energy efficiency and thermal performance are often addressed within the scope of mandatory regulations, the suitability of construction solutions and the incorporation of technical equipment. Considering four residential structures for older adults under construction in Portugal, this paper aims to highlight the importance of a comprehensive approach to these issues, including architectural quality as the main target. In pursuit of this, a cohesive set of intervention principles guided the analysis: the adaptive reuse of raw materials;taking advantage of the site's conditions;vegetation (type and location);construction options and durability;solar exposure and shading;the pedagogy of building use;and the comfort and thermal perception. Several reflections emerge from the analysis: good architectural design must consider dynamic models incorporating each context and the site's conditions;the culture of use and maintenance and the notion of "adaptive comfort" are primary factors to enhance thermal performance and energy efficiency;and each building is a unique result of a complex negotiation process. Bridging research through practice, and multidisciplinary scientific integration enable engagement with reality and raise awareness of the constraints and challenges to innovation in LTC design.

Forms of participation and learning of mathematics in virtual workgroups in engineering students

The objective of the research was to determine the relationship between the type of participation, collaborative organizational structure of the groups and the learning of mathematics, in a group task carried out in virtual form by the context of health emergency by COVID19. During four weeks, eight working groups composed of three environmental engineering students worked four activities on the analysis of the variation of functions. The working meetings were developed by ZOOM and WhatsApp. It was found that reasoning and argumentation as well as problem solving is favored when students express new ideas or explanations about any doubt or when they address the content of the task, especially in groups with an integrative organizational structure. © 2023 IEEE.

COVID-19 X-RAY IMAGE DETECTION ALGORITHM BASED ON DEEP LEARNING

In order to enhance the ability to diagnose and distinguish COVID-19 from ordinary pneumonia, and to assist medical staff in chest X-ray detection of pneumonia patients, this paper proposes a COVID-19 X-ray image detection algorithm based on deep learning network. First of all, a model of deep learning network is set up based on VGG - 16, and then, the network structure and parameter optimization is adjusted, which makes the network model can be applied to COVID - 19 x ray imaging detection task. In the end, through adjusting the image size of the original data set, the input data meets the requirements of the deep learning network. Experimental results show that the proposed algorithm can effectively learn the characteristics of the COVID-19 X-ray image data set and accurately detect three states of COVID-19, common viral pneumonia and non-pneumonia, with a very high detection accuracy of 95.8%. © 2023 SPIE.

Advances in medical textiles

Medical textile is one of the technical textiles sectors, growing faster due to developments in polymer science and technology and innovation in forming new textile structures. In this review, current market trends for the growth of medical textiles for both pre and post covid pandemic periods were discussed. Focus is given to the classification of medical textiles and devices, specific requirements of fibers and widely used types of fibers, and advanced developments in this field, including nanofibers, bicomponent fibers, superabsorbent polymers, and conductive materials used in a wide range of advanced medical devices. Various fabric structures (woven/knitted/nonwoven/braided) have been in use in biomedical devices;however, recent 3D shaped structures such as spacer fabrics, and 3D-printed materials have profoundly marked their significance with its ability to adapt to specific needs of the medical community. Smart wearable sensor technologies for monitoring, diagnosis, and treatment are discussed and critically reviewed, enabling the readers to understand the complexity of the nature of interdisciplinary approaches required for developing such complex structures and systems. Antimicrobial agents (synthetic and natural/organic) used in the development of medical textiles mainly wound dressings, advances in antiadhesive textile coatings, and antimicrobial assessments of medical fabrics are critically reviewed. Finally, a case study on 3D printing of complex structures is presented to update modern developments using fine detail resolution (FDR), a selective laser sintering that uses carbon dioxide laser to produce delicate and complex 3D structures suitable for medical applications. It is anticipated that readers will benefit from this critical overview of trends in this sector and the multidisciplinary approaches needed to meet the demands of the ever-growing consumer base. © 2023 Elsevier Ltd. All rights reserved.

An Enhanced Convolution Neural Network Model based on Depthwise-separable Convolutions for Pneumonia Classification

This paper is an attempt to customize a lightweight model to classify pneumonia images by integrating depthwise-separable convolutions with typical CNN model, and focus on the performance of DSCNN in comparison with typical CNN model based on X-ray images. The experimental result shows that in our four-layer structure, DSCNN reduce around 50,000 parameters compared to CNN. But DSCNN had a relative low recall on COVID-19(89.23%). However, with proper means of optimization such as focal loss and data augmentation, there was a slight increase in test accuracy of DSCNN(from 95.25% to 96.14%), and a significant increase in recall on COVID-19(from 89.23% to 94.61%). And this model also performed well on the rest two labels. © 2022 IEEE.

Small-angle polarimetry as a technique for identification of nucleotide sequences in bioinformatics

Background and Objectives: The method of identification of symbolic sequences associated with the genetic structure of biological objects using the principles of small-angle polarimetry is considered. This method of analyzing and visualizing symbolic sequences obtained by sequencing DNA fragments can be defined as small-angle polarimetry of phase-modulating structures associated with genetic information. Materials and Methods: The analyzed symbolic sequence is represented by a two-dimensional phase-modulating matrix, each element of which corresponds to one of the four basic nucleotides (adenine, cytosine, thymine, guanine), and the depth of modulation of the phase of the reading coherent linearly polarized beam is determined by the content of this nucleotide in the corresponding triplet in the nucleotide sequence. As a result of the diffraction of a reading coherent beam with a polarization plane oriented at an angle of 45° to the sides of the phase-modulating matrix, a spatial distribution of local polarization states of the reading field diffracted on the matrix is formed in the paraxial region of the far diffraction zone. Discrimination of local polarization states in accordance with the proposed algorithm makes it possible to synthesize a binary spatial distribution, which is a unique identifier of the analyzed symbol sequence. Results: Modeling of the processes of phase coding and subsequent analysis of local polarization states in the near-axial region using sequencing results for the strains "Wuhan”, "Delta” and "Omicron” of the SARS-CoV-2 virus has shown a high sensitivity of the method to local changes in the structure of nucleotide sequences. Conclusion: The results of the simulation allow us to conclude that binary distributions of local polarization states of light fields diffracted on DNA-associated phase-modulating structures recorded in the axial region are characterized by high sensitivity to local mutational changes in the structure of nucleotide sequences. The results obtained can be used as a basis for creating effective hybrid methods for analyzing genetic information using the principles of polarization coding and small-angle polarimetry. © 2023 Vestnik Novosibirskogo Gosudarstvennogo Universiteta, Seriya: Istoriya, Filologiya. All rights reserved.

Impacts of environmental policy uncertainty on urban environmental pollutant emissions in China: a study based on textual analysis

How to accelerate the clean use of fossil energy and promote the transformation and upgrading of energy structure is an important challenge commonly faced by countries around the world. In the post-Covid-19 era, the uncertainties faced by countries around the world are increasing and the frequency of policy adjustments in various countries is accelerating. The discharge of pollution by enterprises is significantly impacted by environmental regulatory policies. Under the carbon neutrality goal, the uncertainty of environmental policy caused by multiple political factors can directly influence the decisions made by businesses and residents, in turn, affect their confidence and expectations. However, researchers have given limited attention to measuring the environmental policy uncertainty index (EPUI). In this paper, we select 460 newspapers from the China National Knowledge Infrastructure (CNKI) newspaper database from 2001 to 2016 and use the text analysis method to directly construct China's national, provincial, and prefecture-level EPUI. The results show that China's EPUI has obvious stage characteristics and regional characteristics. By applying the Chinese city-level EPUI to the field of urban pollution reduction, we have obtained an important finding that when urban environmental policy uncertainty increases by 1%, urban industrial sulfur dioxide emission decreases by about 0.145%, and carbon dioxide emission decreases by about 0.053%. We believe that this is due to an increase in environmental policy uncertainty inhibiting the development and scaling of secondary industries.

Structural and Computational Studies of Cobalt(II) and Copper(II) Complexes with Aromatic Heterocyclic Ligand

Two coordination complexes, a cobalt(II) complex tris(1,10-phenanthroline)-cobalt perchlorate hydrate, [Co(phen)3]·(ClO4)2·H2O(1), and a copper(II) complex tris(1,10-phenanthroline)-copper perchlorate 4-bromo-2-{[(naphthalene-1-yl)imino]methyl}phenol hydrate, [Cu(phen)3]·(ClO4)2·HL·[O] (2), [where, phen = 1,10-phenathroline as aromatic heterocyclic ligand, HL = 4-bromo-2-((Z)-(naphthalene-4-ylimino) methyl) phenol] have been synthesized and structurally characterized. Single crystal X-ray analysis of both complexes has revealed the presence of a distorted octahedral geometry around cobalt(II) and copper(II) ions. density functional theory (DFT)-based quantum chemical calculations were performed on the cationic complex [Co(phen)3]2+ and copper(II) complex [Cu(phen)3]2+ to get the structure property relationship. Hirshfeld surface and 2-D fingerprint plots have been explored in the crystal structure of both the metal complexes. To find potential SARS-CoV-2 drug candidates, both the complexes were subjected to molecular docking calculations with SARS-CoV-2 virus (PDB ID: 7BQY and 7C2Q). We have found stable docked structures where docked metal chelates could readily bound to the SARS-CoV-2 Mpro. The molecular docking calculations of the complex (1) into the 7C2Q-main protease of SARS-CoV-2 virus revealed the binding energy of −9.4 kcal/mol with a good inhibition constant of 1.834 µM, while complex (2) exhibited the binding energy of −9.0 kcal/mol, and the inhibition constant of 1.365 µM at the inhibition binding site of receptor protein. Overall, our in silico studies explored the potential role of cobalt(II) complex (1), and copper(II) complex (2) complex as the viable and alternative therapeutic solution for SARS-CoV-2.

Disassembly, Re-Engineering, Mobilization and Re-Assembly Journey of the First Lift Boat from Gulf of Mexico to the Caspian Sea

The Cheleken field offshore Turkmenistan is going through brown field development and challenges with retaining and enhancing production increase every day. Well Interventions are deemed to be a daily necessity to maintain production. Coiled Tubing, Wireline and other rigless interventions have been used directly on platforms resulting in occupying critical spaces, logistic and marine congestion (one Coiled Tubing Move comprises of over twenty lifts), structure integrity limitations, crane and lifting limitation, and a lot more. The need for a self-elevating platform arose and operator search for a proper one within the Caspian Sea ended with disappointments. This paper details the innovative and out of the box solution that was put in place to mobilize the first Lift Boat to the Caspian Sea. A lift boat was identified in the USA in the Gulf of Mexico which was underutilized after the pandemic and oil recession. The Class 230 specifications met the end user's requirements but the challenge was how to mobilize it to the Caspian. In addition, there were a handful of modifications that were requested for the Caspian operation that were not necessarily required in the Gulf. Mobilization of the lift boat must be carried out through the Volga-Don canal locking system which has a width of 57 feet 9 inch (maximum allowable beam for vessels is 56 feet 5 inches). The beam of the lift boat was 78 feet which is too wide to fit through the Volga-Don shipping canal. Hence, it was necessary to disassemble and transport the lift boat in sections. This paper describes the following: • Disassembly requirements necessary to prepare the lift boat for mobilization • The mobilization of the lift boat • • Installation of well service and intervention equipment • Technology and methodology adopted The reassembly requirements once the lift boat reached the shipyard at Caspian Sea The Lift boat was disassembled into three major sections for transportation: a) the center hull module b) the port wing module, and c) the starboard wing module. The wing modules, miscellaneous equipment and containers were loaded onto a barge and sea-fastened for transportation. The center hull module was wet towed to the shipyard located in the Caspian where the lift boat was reassembled, and the well service equipment was installed. The mobilization and assembly happened during the Covid-19 era, and the vessel was hit by Hurricane Ida which impacted the disassembly schedule. Challenges on mobilizing the personnel, equipment, machinery, port clearance, etc. were all extremely tough due to Covid-19. The paper will also cover technical implications on conducting this task by complying with the classification and flag state requirements as per Turkmenistan authority. The main lesson of the paper is the identification of gaps on mobilization and how the improved techniques can be utilized for executing the task on a fast-track manner. © 2023, Offshore Technology Conference.

Virus-laden droplet nuclei in vortical structures associated with recirculation zones in indoor environments: A possible airborne transmission of SARS-CoV-2.

Droplet nuclei dispersion patterns in indoor environments are reviewed from a physics view to explore the possibility of airborne transmission of SARS-CoV-2. This review analyzes works on particle dispersion patterns and their concentration in vortical structures in different indoor environments. Numerical simulations and experiments reveal the formation of the buildings' recirculation zones and vortex flow regions by flow separation, airflow interaction around objects, internal dispersion of airflow, or thermal plume. These vortical structures showed high particle concentration because particles are trapped for long periods. Then a hypothesis is proposed to explain why some medical studies detect the presence of SARS-CoV-2 and others do not detect the virus. The hypothesis proposes that airborne transmission is possible if virus-laden droplet nuclei are trapped in vortical structures associated with recirculation zones. This hypothesis is reinforced by a numerical study in a restaurant that presented possible evidence of airborne transmission by a large recirculating air zone. Furthermore, a medical study in a hospital is discussed from a physical view for identifying the formation of recirculation zones and their relation with positive tests for viruses. The observations show air sampling site located in this vortical structure is positive for the SARS-CoV-2 RNA. Therefore, the formation of vortical structures associated with recirculation zones should be avoided to minimize the possibility of airborne transmission. This work tries to understand the complex phenomenon of airborne transmission as a way in the prevention of transmission of infectious diseases.