The market for electric bicycles has grown extremely and developed rapidly in recent years. To enter such a market with a new product, the development process has to be fast, and throughout the process, feedback from future potential customer(s) should be sought in order to achieve the best possible market acceptance. The article presents the design process of a pedelec e-bike central drive system. The authors were members of the development team and the designers of the mechanical transmission, and therefore had a good overview of the whole project. The development process and the set-up of production require a certain amount of time, during which design changes are inevitable due to changes in customer expectations and demands. The development team should respond to these changes and take them into account during development. Only the ability to react to changes and constant communication with the customer will ultimately lead to a product that can be commercially successful. Based on a critical review of the successfully completed project, general guidelines were established for the development of mechatronic products that consider the principles of Agile methodology. Particular attention was paid to the development of polymer gears, as these were the most demanding components in the system. The presented guidelines were based on an overview of the e-bike R&D process presented, but they can be generalized and used in the development process of any technical physical product. Agile methods were developed in the field of software development and therefore cannot be directly transferred to the field of physical product development. The article highlights and discusses individual special features that distinguish agile development of physical products from software development. Due to fierce competition, shorter delivery times and product complexity, the biggest challenge in new product development is to increase the innovation and efficiency of the development team to shorten the product development cycle. Recently, agile methods of product development have become established alongside concurrent engineering ,2,3. AgiAgile Manifesto, Beck et al. [In the k et al.  presentek et al.  stated, k et al. ,10. One k et al. , which ik et al.  has showk et al.  concludeSommer et al.  suggest Cooper and Sommer  report sCompanies that use agile stage-gate management (ASGM) can expect shorter development times and a higher degree of innovation, but have to spend more resources to accomplish this. Physical product developers using ASGM experience negative impacts on project resource efficiency due to the need for dedicated resources, frequent product demonstrations, and duplicate management structures .Hendler and Boer  argue thIn his research, Smith  also intSchuh et al.  analysedVarious agile methods are available, hence, a targeted selection of a suitable agile method can be tailored to the company’s boundary conditions and integrated into the company’s existing product development structure to generate hybrid design processes . The conŽužek et al. explored the possibility of introducing Scrum into concurrent product development and proposed a Scrum framework for an agile–concurrent hybrid. Scrum was suggested for carrying out the daily work . The maiZink et al.  argue thDue to the decline in fossil fuel consumption and increasing pollution, electric drives are becoming the most widely used alternative to regular internal combustion engines. Electrification and the share of electric drives varies in transport systems by region and sector. The lowest share of electric drives is found in agriculture and wood processing. Caban et al.  note thaApart from the mechanical power source in e-mobility products, i.e., the electric motor, a crucial part of the system are the power transmission components. Here, gears are, in general, the most dominant and widely used components for transmitting rotational motion and power, as well as achieving various required transmission ratios. High-performance gearing design, especially when non-metal materials such as polymers and composites are used, is a complex task that requires extensive know-how and the involvement of numerous digital and numerical tools such as CAD, Finite element analysis, standards-based computational tools, etc. Gears are prone to many different damage modes during operation, induced by applied load conditions, selected geometries, materials, lubrication conditions  and evenThis paper presents a real-world project related to the gearbox drive system with polymer gears. The central drive powertrain system is used in an e-bike. Throughout the project, the authors were directly involved in the design process. The project work required a number of changes to product requirements due to customer needs and demanded a high level of adaptability from the development teams involved. The APD method with an integrated Scrum framework was identified as the appropriate approach, even though some adaptations were required for mechanical products. Based on the experience gained in the project, a generally applicable method based on agile product development was prepared. Mechanical and mechatronic systems were the target area of application.The research critically reviewed the development and mechanical design process of the e-bike drive system. The market for e-bikes has rapidly evolved in recent years. New models of e-bikes are to be launched in the spring. This results in additional requirements for accelerating development activities. Due to the high expectations, agile product development methods with specific adaptation were used. The use of APD methods was critically evaluated at the end of the project. Corrective measures for better project management were defined based on systematic analyses under various aspects. A key concept of agile methods is rapid feedback and testing of products. When developing physical products, this is of course not possible due to financial and time constraints. We tested virtual prototypes and different configurations of mechatronic prototypes to find the optimal combination.Analysis of the team composition based on the Scrum framework.Review of the APD-based product development process and the influence of sudden specification changes on the process.Specifics of polymer gears development following the APD framework.Critical review of the communication model in correlation with the considered Scrum method.In the following pages, several key methods are presented that together formed a comprehensive APD framework for the entire project at hand:The way the APD methods were used was critically evaluated at the end of the project. The review also represented the foundation on which the agile development guidelines for mechatronic products, subsequently presented in Sect. 3, were built.The goal of the project was to develop a new e-bike drive system (powertrain). The dynamic market for electric bicycles led to several changes in technical and commercial requirements during the project implementation. Project activities were carried out in a manner characteristic of APD in combination with concurrent engineering. It should be emphasized that at the beginning, a very tight time window was given and the requirements in terms of volume and required power of the powertrain could not yet be met. Competitive products were benchmarked, and several products analyzed. Some of the existing solutions used toothed belts, others gearing. Gears made of plastic have several advantages and were therefore considered a real option from the start. Plastic gears run quietly, require no lubrication and can be manufactured at a competitive cost. However, plastic gears can only be loaded to a limited extent and are sensitive to elevated temperatures. Therefore, the project required specific skills to develop polymer gears and test their durability.Sub-teams were formed for each module of the powertrain, as shown in Sub-team P1: Project coordination, system design, motor design with electronic commutation, powertrain durability testing.Sub-team P2/customer: system design, power source and wiring, analysis of customer requirements (bikes manufacturers)Sub-team P3: Powertrain R&D (including polymer gearbox)—the authors were part of this team.Sub-team P4: Development of the torque sensorSub-team P5: Development of electronics and control systemThe tasks of the project sub-teams  were as follows: This paper authors were active in sub-team P3 that was working on powertrain, and the presented study relates to the development of a mechanical assembly with polymer gears. Sub-team P2 created the original technical requirements for the powertrain. The first modification to the requirements occurred only five weeks after the original specification was established. After the virtual prototype was presented to the powertrain customer, several new requirements surfaced. The virtual prototype included product architecture, mechanical components and dimensions. The presentation of the prototype allowed for a better understanding of product structure, functionality and competences of the powertrain team. The technical requirements became much more demanding. The required product durability was extended by 10%, while the permissible dimensions and weight of the drive have been reduced—length by 12%, width by 7%, height by 4% and the total weight by 25%. Seventeen weeks after the first modification to requirements, a second change followed, increasing peak power by 100%. At the same time, the permissible housing temperature has been reduced by 25%.Generally, the technical requirements upgrade occurred at the end of the sprint, after the presentation of product development was performed. The second modification was triggered by a benchmarking analysis. One of the products on the market offered a powertrain with better performance than in the original technical requirements.When the technical requirements changed, the traditional product development process would be shifted back to the beginning. Using agile methodology allowed the Scrum team simply to start a new sprint. Product development activities in different sub-teams were affected by mutual dependency between sub-modules. The integration of a torque sensor, connector sub-assembly and electronics at different stages of development led to additional changes in the powertrain assembly. The rough representation of the activities in the product development process is shown below . After eAfter confirming the initial customer requirements, a conceptual design of the powertrain, designated VP A0, was created. During the development process, several numerical simulations  were performed, and appropriate standards were applied in the calculation of the components. Then other components were included . After the modification to requirements were specified, the sub-team P3 for the powertrain started the new sprint by implementing the required changes. After numerous improvement steps, the powertrain design was ready for the first working mechanical sample—prototype A1 . The powA thorough analysis of the successfully completed prototype A1 led to the identification of critical deficiencies that needed to be addressed in subsequent iterations. These concerned both the assembly and functionality of the current solution itself. At the same time, the design had to be adapted to allow mounting of the array connectors and electronics required to power and control the drive, as well as the torque sensor. While the following prototype iteration A2 did not yet incorporate the above components, the housing was already modified to allow these components to be inserted, as shown in The A2 prototype met all the set requirements, however, at the time of introduction, a competitor just re-leased a new product on the market, which noticeably surpassed the drive performance set in the current specifications of the presented project. This led to a second change in specifications, which now included 100% increase in peak power and a lower overall weight of the drive, leading to significant problems at that stage of the project. Since the electric motor did not provide sufficient peak power at the present gear ratio, it had to be modified by introducing stronger magnets, and the gearbox had to be changed to increase the gear ratio while maintaining the overall volume and further reducing the mass. This task was naturally handed over to the ST responsible for the mechanical assembly , which managed to increase the gear ratio by 25% while maintaining the same volume. The two-stage gearbox now included a pair of steel gears on the second stage, breaking away from the plastic version previously used for the second stage driven gear. While the use of steel could bring with it an increase in the mass of the drive, this was offset by a reduction in the face width of this gear and various other design changes that were now possible thanks to the newly gained space previously occupied by the larger plastic gear. These changes, along with a newly developed custom torque sensor and power and control electronics, were introduced in physical form in the prototype A3 . The latAfter confirming the updates introduced in A3 and a modified mounting system requested by the customer, the B phase of prototyping began with prototype iteration B1 . Some chPolymer gears were indispensable due to technical requirements for low noise levels and low weight, and competitive costs. Polymer gears enable reliable operation even without lubricant. There is not only one argument for selecting polymer gears, but a sum of advantages in comparison to disadvantages and other technical options. However, vibration damping and reduced noise levels are the main reasons for selecting polymer gears. Simultaneously with the development of the entire drive, intensive research and development took place in the field of polymer gears. Polymer gears have a limited load capacity. The first stress level showed a gap between the required load and the mechanical properties of the polymers. There was a large number of potentially interesting polymer gear materials. However, several material properties such as fatigue strength, wear and coefficient of friction, which are important for the design calculations of polymer gears, were not available in the material data sheets. Therefore, gear tests for different material combinations were carried out before and during the development of an optimal gear drive. Plastic gears for testing were manufactured by injection molding. Durability tests have not shown any significant difference between cut and injected molded polymer gears. The steel gears for testing were manufactured by cutting . Gear teWith polymer gears, there are several limitations due to the material properties that need to be checked during the design process: root and flank strength, temperature, wear, deformation, gear quality and final installation quality . All of The product development team already had expertise in the field of polymer gears. Additional research was conducted on standard test rigs and standard gear samples. Polymer gear design guidelines and material properties were used as input for the design of the drive. Parallel to the prototyping, durability tests were carried out on a test bench . The aimThe pinion is connected to the shaft of the electric motor and is made of steel. The pinion meshes with three planet wheels made of plastic a. The plWear of polymer gears  was idenWith the correct design of the gears and accurate data of the polymer material, we were able to significantly shorten the development cycle, reduce the number of iterations of the physical prototypes and thus increase competitiveness in product development. Various measures have been introduced to extend the service life. Prototyping entire drives is even more expensive and time-consuming. It is important to reduce the number of iterations as much as possible. By calculating polymer gears and reliable material data, the number of prototypes required could be significantly reduced.During the project, several areas of communication were important: communication between team members, communication between individual teams and communication with the drive’s customer. The customer also communicated with bike suppliers and battery developers, as well as with end distributors and resellers of the electric bikes, who knew best what the customer wanted. The information was passed on to the development teams of the individual drive sets in the form of modifications.Inter-partner communication is critical, especially for teams working on the same product line that are not in the same location. The members of the development teams for the electric motor, electronics, connectors and torque sensor were in the same place. In contrast, the members of the team developing the mechanical transmission were in three different locations.The members of the mechanical transmission development team had daily online communication. At least once a month, the team members also met on site. At a critical stage in the development of the version B prototype, the members of the mechanical transmission development team moved to the same location for two months. This was a critical part of the project where problems with the prototypes arose and at the same time, the final details for the production of the later versions of the prototypes and also for series production had to be determined. In this phase, on-site communication played a crucial role in speeding up the change and solving problems.Due to the geographical distance, communication with the other partners took place mainly online, with each of them meeting physically at least once during the project. During the development, regular communication with the drive’s client took place, mainly online due to the distance, but on-site meetings were also scheduled several times. During key phases of the project, improvements to the virtual prototypes were presented to the client in weekly video conferences. Before the meeting, the virtual prototypes were evaluated and tested by the team members. After each meeting, the necessary changes and additions were determined.Document sharing within a company is usually governed by a PLM system. In development teams composed of members from different companies, the members usually did not have access to the PLM system of all companies, but only to the one in which they are employed. In the development task studied, the exchange of documents took place via a server. Which information and documents the individual members had access to was regulated by access rights. The latest version of the documents always had to be uploaded to the server. This is important so that all members are aware of all the information and so that changes to the design and to individual documents are traceable.Access to the latest revision of documents was recognized as an open issue that could be improved. A common server was used for storing 3D models and documents. However, it was important to update the files on a regular basis and it was a human factor. Each document had the basic meta-data such as author, date of creation, date of uploading, revision. It helped to assure traceability between different versions of documents. There were several security measures to assure controlled access to the documents: (1) Each of the team members signed an NDA document. (2) Research activities were running in dedicated rooms; random visitors were not able to access documents. (3) Access to the server was controlled with username and password. The document management software enabled access traceability to documents. (4) Regular backups and storing of backups at safe locations. Some more advanced measures such as encrypted files and encrypted communication were not applied. The awareness of team members was the main pillar of data security.Following the completion of the central drive development project, the process was critically reviewed in terms of operational efficiency, communication, information gathering, and design testing. The review was conducted within the available agile methodology and Scrum framework guidelines. Several issues were identified with the project execution, but also with the available guidelines, as most of them were only partially applicable to the type of project described. Using the obtained review insights, new agile development guidelines, tailored to mechatronic product development were developed.Testing of the developed product using prototypes is of paramount importance. Producing a physical prototype is time-consuming and costly and can result in project delays if a large number of prototype iterations are required. Virtual prototypes can often successfully replace physical prototypes, provided that the underlying assumptions of the used physical models have been suitably validated.While initial specifications were accurately defined, these often changed based on new insights gained by the customer either following their internal market analyses or after the presentation of intermediate physical prototypes by the development team. Several changes occurred fairly late in the project resulting in further delay. Using virtual prototypes to convey new important design changes can help the customer understand more quickly what their actual requirements are and iterate to the final solution faster.To confirm that newly introduced solutions are technically suitable, virtual prototypes have their limitations, and physical testing is often required. Partial physical prototypes proved critical to determine if a function  was successfully met. To test and confirm critical components and sub-assemblies more quickly with partial physical prototypes, access to rapid prototyping tools that enable component production of comparable quality to conventional production methods is essential.The response to changes in customer requirements was often too slow. Adapting to intermediate specification changes can only be conducted in a quick and responsive fashion if modern CAD/CAE software tools are systematically used to develop and numerically test new VP iterations and then transition to physical prototypes. Using suitable parametrization methods for quick model updates and numerical simulation checks, combined the model-based definition approach (MBD) to transition seamlessly from model to production can yield quicker prototype iterations.Only after the mechanical system of the e-bike drive was developed, the electronics necessary for system power supply and control could begin to be tested. This could have been avoided, i.e., the electronics could be tested in parallel with the mechanics, if a suitable prototype testbed replicating the e-bike operation conditions was available for this purpose.While regular meetings were scheduled during the project to help keep all members of the various STs informed, they were often too broad in scope, regularly including all or most of the STs involved and covering a wide range of topics that often did not directly affect all STs. Broader meetings should be time-limited and only serve to define what needs to be done, not discuss problems. Issues are then discussed in more detail within each ST or among the STs involved.The project backlog and reviews of each development cycle—both in terms of design updates and new knowledge gained—were often poorly managed, contributing to slower than optimal project progress. Implementing appropriate (web-based) tools and methods for regularly updating and sharing the latest relevant information is especially important when the parties involved are from different organizations across wide geographical areas. In the project described, the flow of information proved to be suboptimal, as information was not exchanged directly and quickly enough between the parties involved.The key deficiencies that affected the overall performance of the development process are:The issues just described were identified only after a thorough analysis of the project, most of which was conducted after project completion. In conjunction with a comprehensive literature review, several new rules and guidelines—based predominantly on agile development principles—were distilled from all the information gathered. These guidelines, described below, could help make the physical product design process more efficient and lead to superior products.The product is divided into individual sets that are interdependent and ultimately make up the entire system but can also be developed individually and simultaneously to a certain extent.Teams are composed of members with specific skills required to develop each set. Work on individual sets should take place within an appropriate agile framework. In the case studied, Scrum proves to be a suitable basis.The product development team needs to be supported with key skills such as polymer gear design. Necessary research must be conducted in parallel with a simplified and generic model to reduce time and complexity (if possible).The results of each iteration/sprint must be evaluated accordingly. Numerical simulations  and engineering tools such as FMEA  and DoE (Design of Experiments) can be employed to assess the virtual prototypes. Features that cannot be evaluated on the virtual prototype are tested on a physical prototype. The physical prototype needs to be adapted to the testing purpose.Continuous product testing is essential. This is divided into the following two categories:A) Functionality testing ▪Functional testing is carried out at four levels and takes place before testing at the customer’s premises: (I). Virtual prototype testing, (II). Testing of partial physical prototypes , (III). Testing full physical prototypes of each stage and (IV). Testing of the whole product . ▪A full physical prototype is required for functional testing of the product. The prototype merges the results of successful phases of all Scrum Teams. The production of the prototype is time consuming and usually involves high costs. Individual product subassemblies are interconnected but are not always needed for testing in all phases. Some tests can be performed on prototypes that only cover the R&D work of a single scrum team or a limited number of Scrum Teams.B) Product acceptance testing with potential customers ▪The result of each sprint is an updated virtual prototype. A set of fully functional virtual prototypes can be assembled into a comprehensive virtual prototype that can be shown to the customers . By reviewing the customer feedback, the necessary changes that lead to a higher product value are identified. Customer feedback must be taken into account in the next sprint. It is especially important to communicate with customers in the earlier phases and present updated results (and thus determine what customers want).  ▪Identify modules or submodules that can be further developed while waiting for production and test results of a physical prototype. Optimal parallelization of development tasks is the goal. ▪There are several critical issues to consider when developing a completely new, complex physical product. If ST does not master these, it may not be able to meet the required product specifications. External revisions can provide new solutions and help bridge the critical points. ▪Information must be communicated comprehensively and as quickly as possible, without unnecessary noise. Short chains of communication usually prove to be the best.Accordingly, we have developed an updated model of agile development of mechatronic products using the Scrum framework . ProductEach sprint requires the internal structure as shown in Preliminary design of the gear based on the input data . If the selected polymer material pair already has known material properties, the procedure can be continued with Stage 3.Accelerated (step) tests. Preliminary step tests . The step test is a fast prediction of tribological properties and polymer strength and helps to identify the most promising material pairs, which are then followed up in life tests (durability tests). Coefficient of friction can be determined from operating parameters and measured temperature as presented in .Lifetime tests on a test bench with standard size gears (at selected speed and torque). The test is carried out with the pair of materials and under conditions close to those of the final product . Wear, coefficient of friction and durability are properties, which depend on selected pair of materials. Durability tests of gears are the best indicators of material properties, which are important for the calculation of gears . MateriaDetailed calculation and design of polymer gears: well-defined material properties (Stage 2) enable reliable calculation of gears. This reduces the number of prototypes required.Testing of gears in the final application . The production of tools for injection molding is expensive and time-consuming. It is important to perform all the previous steps well and create the tools only once.Taking into account the observations made during the project, the previous experience of the development group in the field of polymer gears and the principles of agility, we propose the model of polymer gearbox development shown in When developing polymer power transmissions, there are several performance enhancements possible. The first option is gear shape optimization. Most mass-produced polymer gears are injection molded, hence, the manufacturing cost is not dependent on the gear profile shape. Therefore, profile modifications such as enlarged root rounding or fully rounded roots can be easily applied. Furthermore, special non involute gear geometries with increased tooth bending strength and reduced specific sliding can be used, without the need of special cutting tools and additional costs . The secThe conclusions of this research are consistent with the experiences of several other authors who have attempted to integrate agile methods into the physical product development process, such as Cooper and Sommer . The phySalvato and Laplume argue that the agile approach has a negative impact on the efficiency of project resources . This isHendler and Boer argue that binding decisions must be made early in the physical product development process . The autIf we consider the presented development process in the context of the presented guideline, some remarks can be formulated. The product was divided into several interdependent sets, which could be developed individually to a certain extent. The Scrum Teams were in continual communication with the customer, who was incidentally a member of the development team one level higher. The entire development process was guided from the beginning by the wishes of the end customers. These were identified by project managers and system architects and passed on to the STs.How strong prototyping needs to be in physical product development is an important question. Zink et al. argue that prototyping is the key aspect of the agile approach and have established criteria for the use of physical prototypes . ReichweThe STs consisted of a fixed number of members, but experts were brought in depending on the phase and project needs. The need for specific knowledge and a larger number of staff was only present in individual development phases. Individual members of ST could contribute in the phases where their specific knowledge could contribute to a better product. The results of each sprint were evaluated by all Scrum members and presented to the customer who was most familiar with the e-bike user’s needs. The set of activities foreseen in sprint planning also defined the duration of each sprint.Sprint planning was conducted by the members of ST before the next sprint was started. The aim was to identify the requirements to be solved in this sprint. At the end of the sprint, the results were reviewed and presented to the client. Together with the customer, the design review was conducted and the requirements for the next sprint were defined. After successive sprints, the result was verified on a prototype. The prototype could be partial models—pure design or partial functional prototypes. The individual product assemblies are interdependent, but it is not essential to test them all in each phase. For example, version A prototypes were used to test mechanical performance and had an external power supply and control electronics, while the torque sensor and connector assembly were not included at this stage.Different projects and products require specific competences. In the case of the drive, the external partners for the control system and the torque sensor were included in the project team. The key competence of the scrum team for the powertrain was the knowledge of polymer gears. It was crucial to split the whole project into tasks that could run in parallel. The results of the parallel proficiency tests on the test bench were used for the polymer gearbox calculations and the powertrain design. This reduced the number of prototyping iterations needed, contributed to an optimized design and shortened the overall development time of the drive.The project carried out has specific characteristics, such as the degree of complexity, the experience of the partners involved and the competences of the members of the project team. The authors have tried to set guidelines for the agile approach in general. However, each company and each product has specific requirements, and each team has specific competences, so agile tools and methods have to be applied individually. This is in line with . The mecThis study was conducted during an industrial development project. The development was based on a combination of Scrum-based APD and concurrent development methods, which enabled immediate address of all challenges, resulting in an excellent final product and a satisfied client and end customer. Regular communication with the client and frequent iterations/sprints related to presentations of the results proved to be crucial for early introduction of changes.Physical prototypes are essential for testing and validating the functionality of mechatronic products. Compared to software development, physical products usually require the creation of several physical prototypes in addition to virtual prototypes. However, this requires a certain amount of time and money. With the right approach, ST can reduce the number of physical prototypes accordingly, while developing certain parts of the product with the production of the physical prototype. When mass producing physical products, it is important that the entire production is well prepared and planned before the final prototype is available.Prototyping powertrains is time-consuming and costly. It is not acceptable to carry out tests on polymer gears, such as selecting the polymer material or optimizing gear geometry for the entire drive. Systematic polymer tests were carried out before and partly in parallel with the development of the drive. The design of sophisticated drives requires very precise input data on the polymer gear material combinations and durability, which were determined on the test bench for standard polymer gear sizes. The drive prototype is used to fine-tune the design parameters and for product validation. It is important to identify key technologies and competencies and integrate them into the product development team in a timely manner. Based on a critical review of the successfully completed project to develop the central electric drive of the bicycle, the study summarizes the most important guidelines for the agile development of mechatronic products.The authors plan to further use the agile methodology on new product development projects. New development projects of products of varying complexity will contribute to new experiences with the application of agile methods. The goal is to establish criteria and more detailed guidelines for which agile tools and methods should be used in the development of physical products.


Journal of Membrane Science published the highest number of articles and was identified as the most-cited journal in the field. China, India, and the USA were observed as the top three research hubs. The top-ranked authors in the field were Wang, Jixiao, and Wang, Zhi. To find research trends, four different clusters of keywords were generated and analyzed. The top five most frequent keywords turn out to be polyaniline, water, performance, membranes, and nanoparticles. The analysis suggests that the application of nanotechnology for modifying PANI membranes  is the future of this field. This study elucidates the research streamline of the field that may serve as a quick reference for early career researchers and industries exploring this field.Polyaniline (PANI), which is a member of the family of electrically conducting polymers, has been widely discussed as a potential membrane for wastewater treatment. Although a steady growth in PANI literature was observed, analyzing PANI literature quantitatively is still a novelty. The main aim of this study is to unearth the current research status, global trends, and evolution of PANI membranes literature and their use in water treatment applications over time. For this purpose, a scientometric study was performed consisting of bibliometric and bibliographic analysis. A total of 613 entities were extracted from Web of Science published during the last 50 years and were analyzed to map trends based on leading peer-reviewed journals, publication records, leading research disciplines, countries, and organizations. The study shows that the number of annual publications increased exponentially from 2005 to 2020 and is expected to keep increasing in the current decade. The  Ever since its discovery, polyaniline (PANI) has proven to be an exceptionally useful polymer that has found wide applications in diverse fields, such as corrosion-resistant coatings , tissue At this juncture, it was felt necessary to sketch an overview of the recent research trends in the use of PANI membranes for water treatment applications. It must be noted here that despite its high value in understanding its research directions, such a study has not been reported so far in the available publications. Keeping this in mind, this article aims at providing quantitative mapping of the field of PANI membranes, in terms of water treatment, by using bibliometric and bibliographic analysis.Bibliometric analysis is a widely used research tool for exploring and analyzing the literature published on a specific topic or a field to map research evolution while endeavoring emerging topics of a field . This teAbout 21,100 peer-reviewed journals are currently indexed in this database which provides access to about 53 million publications along with 1.18 billion cited references [The year of publication was set to 1971–2020, and all the articles published in languages other than English were excluded from the analysis. Data were exported as plain text files: each containing 500 entities. This data included a full record of publication, including the type of article and page numbers along with cited references. For visualizing and analyzing data, VOSviewer , and OriOn searching the Core Collection of WoS, a total of 613 entities were found related to PANI during the span of 50 years from 1971 to 2020. The scientometric analysis and discussion on the results obtained are being produced as follows.Although the authors searched the Core Collection of WoS for the last fifty years, the very first article discussing PANI membranes in the context of water was spotted in 1995 . In thisThe last 25 years of research progress in PANI membranes for wastewater treatment can be classified into two periods: the explorative period and the developmental period. The explorative period is the time when the conceptual basis of the topic was being built and the development period is the time when the topic started getting matured and received a lot of attention from the research community. For the present case, 1995–2004 was the explorative period for PANI membranes. On average, one or two new publications were introduced each year during this era. Following the first publication  related The number of articles published annually showing the research growth in the subject under study is plotted on a chart along with the cumulative number of publications starting from 1995 to 2020 as shown in pP is the projected number of cumulative publications in a specific year Y. Using Equation (1), the total number of publications that are expected to be published by 2030 is estimated as 1425, which is nearly three times the cumulative number of publications in 2020.After performing the statistical analysis of the data of the publications, it is concluded that the cumulative number of publications shows a regular exponential trend with the following equation.In the development era starting in 2005, steady growth was observed in PANI membrane literature focusing on water treatment. A wide range of studies was performed during this period and various technologies were integrated with it, as discussed in The entities obtained from the database were distributed in six categories: research articles, proceeding papers, review articles, book chapters, meeting abstracts, and early access. The majority of the entities belong to research articles (93.96%), proceeding papers (7.01%), and review articles (2.28%), whereas the contribution of the remaining categories is marginally insignificant, i.e., 0.98%. Only 12.56% of the total entities were published as open access articles, while the remaining 87.43% were accessible with a subscription. Concerning the language of publication, 98.37% were published in the English language, followed by Chinese, Portuguese, and Polish, which contributed 1.14%, 0.32%, and 0.16%, respectively. Articles published in languages other than English were not included in the analysis.The citation analysis showed that all entities related to PANI were cited 15,059 times with each paper cited by 24.97 times on average. Overall, the h-index of this topic was 60. Most cited articles of a field provide valuable information about the important concepts or ideas of that field. In the case of PANI membranes for water treatment, a list of most cited articles has been presented in In author analysis, it was realized that there are about 2551 authors who have contributed to research on PANI membranes for water treatment. A list of the top 10 authors is presented in In total, about 63 countries have been involved in PANI research over the last 50 years. To spot out leading countries, only those were selected who have a minimum of seven publications and ten citations on their credit. Twenty-six countries were filtered out and are mapped in It is clear from The top 10 countries involved in PANI research contributed 71.39% in publications and 71.37% in citations as shown in The leading organizations in PANI membrane research are depicted in Journal of Membrane Science is the leading journal in this field, followed by Desalination and RCS Advances.This analysis shows that the literature related to PANI membranes for water treatment was published in a total of 276 journals, out of which 26 have published at least 5 articles and have received at least 50 citations as shown in Among the top 10 journals in the field, the majority of the journals are focused on the chemistry or chemical aspects of PANI membranes, followed by the materials’ application. Different categories involved in studying the chemical aspects of PANI membranes are electrochemistry, analytical chemistry, physical chemistry, and multidisciplinary chemistry. All these categories cover different aspects of chemistry. For example, electrochemistry deals with the relationship between chemical changes with electricity. Generation of electricity as a result of chemical reactions, and chemical changes as a result of electricity production, are the main topics covered by electrochemistry. Analytical chemistry sheds light on the analytical techniques that generate any type of information about chemical systems, such as separation techniques, pyrolysis, and thermal analysis. Physical chemistry includes resources on photochemistry, solid-state chemistry, kinetics, catalysis, quantum chemistry, surface chemistry, electrochemistry, chemical thermodynamics, thermophysics, colloids, fullerenes, and zeolites. Multidisciplinary chemistry is concerned with the interdisciplinary approaches applied to chemical systems .The engineering perspectives of PANI membranes are discussed under chemical engineering which deals with the conversion of raw materials to useful products. The next research category most popular among the top 10 journals is related to materials including polymer science and multidisciplinary materials science. Polymer science includes all resources dealing with the study, production, and technology of natural or synthetic polymers; whereas, multidisciplinary materials science covers resources having a general or multidisciplinary approach to the study of the nature, behavior, and use of materials .Major research disciplines within PANI research are depicted in Overall, the most frequently used keywords are listed in In addition, information related to the evolution of the field can also be extracted from content analysis as shown in The content analysis technique was used to find out the main research streams of the field. A total of 3215 keywords were extracted from the analysis and a filter was applied to map frequent keywords. Only those keywords sorted out have a minimum frequency of occurrence of 10, and these are presented in Cluster 1 (red) relates carbon nanotubes to PANI membranes and water treatment. A strong linkage was observed between PANI membranes and carbon nanotubes reflecting the fact that it is a common practice in the literature to reinforce, template, or blend carbon nanotubes with PANI ,50,51,52Cluster 2 (green) portrays methods used for the removal or reduction of pollutants from wastewater using PANI membranes. Mostly discussed methods/techniques in this regard are adsorption, ultrafiltration, and nanofiltration. In addition, cluster 2 also highlights that electrical conductivity and wettability play vital roles in determining water treatment efficiency. Cluster 3 (blue) sheds light on the different techniques used to improve the efficiency or performance of PANI membranes. The study of morphological characteristics, surface modification, and transport properties of PANI membranes has been promising and mostly discussed by the research community. Cluster 4 (yellow) also highlights some common practices used in coordination with PANI membranes for water purification. Dehydration and pervaporation of water-miscible compounds such as tetrahydrofuran, as well as separation and pervaporation of gasses and liquids, are found to be some most prominent practices. Moreover, hydrophilicity retention of PANI membranes due to chitosan, along with the effect of temperature and permeability of membranes are spotted as some highly discussed topics.PANI membranes have great potential as an alternative to traditional oxidants for oxidation of organic compounds in wastewater treatment. PANI membranes can be applied at higher pH values than other available oxidants, and it also has advantages such as fast redox reaction kinetics and low cost. These advantages have led to the use of PANI-based technologies for removal of organic compounds from aqueous solutions. The main applications are in dyeing, food and beverage, pulp and paper, textile, chemical, petrochemical, and pharmaceutical industries. However, there are a few challenges to using PANI membranes for the treatment of wastewaters as discussed below.Despite the great potential of PANI membranes, the use of PANI membranes for wastewater treatment is limited due to the challenges associated with their application. The main challenge is the reduction of the lifetime of the membrane by the oxidation of the PANI. The use of antioxidants is another challenge, and the feed solution may be limited in the number of antioxidants available. The PANI is a semiconductor and is sensitive to electromagnetic fields (EMFs). This makes the PANI membranes prone to breakdown when the membranes are subjected to EMFs. Although the PANI membranes have great potential, their application in wastewater treatment is still in its infancy. Some key challenges of using PANI membranes for the treatment of wastewaters are discussed below.The main factors affecting the PANI membrane durability are the chemical nature of the species transported, the pH of the solution, and the redox potential of the membrane. These factors lead to PANI degradation, which includes loss of electrochemical activity followed by a decrease in the crosslinking density and PANI content in the membrane. The main mechanisms of PANI degradation are reduction in functional groups, oxidation of the aromatic rings, and possible chain scission. The reduction in functional groups by water-soluble species can be prevented by keeping the pH low. Oxidation of the aromatic rings can be prevented by adding antioxidants such as phenol, hydroquinone, and thiabendazole. Further, it can also be controlled by reducing the pH of the solution. Lastly, PANI chain scission can be controlled by low pH values, but is a very slow process. The chain scission leads to the formation of highly branched PANI polymers and poor water permeability. When these branched polymers react with other oxidants, the membrane loses its ability to remove organic impurities.Owing to this degradation, the life span and durability of PANI membranes become a challenge. Therefore, there is a dire need to develop new functional groups and aromatic rings that could help in increasing PANI membrane stability.Due to the high pH and conductivity of the feed solution, the selection of an appropriate electrochemical technique to determine PANI concentration becomes a challenge.The PANI content in the membrane can be quantified by UV–Vis spectroscopy for the UV–Vis region of the spectrum. However, this technique does not provide information about the amount of PANI degraded in the membrane. To overcome these limitations, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) have been used to some extent. However, these techniques are time-consuming and expensive. In addition, they do not provide precise information about PANI degradation.The oxidation of the PANI in the membrane leads to the formation of PANI radicals, which react with water to form hydroxyl radicals which reduce the lifetime of the membrane.The regeneration of the PANI membranes is an important issue. The main regeneration methods are air oxidation, UV oxidation, and chemical oxidation. Air oxidation is a viable method to regenerate the PANI membranes. However, it is not advisable for wastewater treatment applications due to the high pH value of the feed solution. UV oxidation is the common method used for the regeneration of the PANI membranes. It is a simple method, but it requires a high UV intensity and is not suitable for large-scale applications. Low-pressure chemical oxidation is a promising method for the regeneration of PANI membranes. This method is based on the oxidation of phenol by ozone in water to generate HO radicals, which react with the PANI to form phenol and regenerate the PANI. However, requiring low pressure is a key limitation of this process.For industrial applications, PANI membranes should have the potential to deal with wastewater of diverse contamination levels and conditions. The adverse environmental conditions found in wastewater treatment are biological activity, high pH values, temperature, and pressure. The biological activity can be controlled by using antibiotics and biocides, which are not suitable to be used with PANI membranes. The pH of the feed solution is difficult to be controlled due to the chemical reactions and microbial activity. The temperature and pressure can be controlled by using jacketed reactors, but they are also challenging factors.Further, PANI membranes have limitations when the feed water is highly saline and has high pH values. In the presence of seawater in the feed solution, the membrane is less stable due to the presence of NaCl, which can interact with the PANI in the membrane and form NaPANI. The high pH feed solution leads to the formation of hydroxide ions, which can react with the PANI and form water-soluble PANI species with anions such as chloride. This results in the formation of pores in the membrane and membrane fouling.The research growth in the application of PANI membranes for water treatment is highlighted. The analysis reveals that the concept of using PANI membranes for water treatment application was introduced during the 1990s. The era of 1995–2005 was an explorative period in which conceptual basics were developed, such as PANI membrane doping and blending, whereas, after 2005, the development era started in which this topic received steady attention.Journal of Membrane Sciences, Desalination, and RSC Advances are the leading journals. The majority of the top journals in this field were focused on chemical aspects of membranes followed by material applications in PANI membranes.A total of 276 journals have published research related to this topic out of which A total of 63 countries were found active in PANI membrane research with China, India, and the USA as top players in terms of citations and number of publications. Nevertheless, concerning the number of publications per population, China and Australia were spotted as the leaders.Concerning research trends, performance optimization of PANI membranes for water treatment was observed as the most discussed topic in the literature. For performance enhancement, the immensely used techniques include the use of nanoparticles and nanocomposites, modification in fabrication techniques, and the use of films.Using nanoparticles, carbon nanotubes, and graphene oxides; employing electrospinning, and introducing new adsorbents are hot topics in the field.This study reports a scientometric analysis of the literature, related to the application of PANI membranes for water treatment and published during the last 50 years. A total of 613 entities were extracted from the Web of Science and were analyzed using bibliometric and bibliographic analysis techniques. The key findings of this study are as follows:


Since the advent of IVF in 1978, many novel techniques have arisen in Assisted Human Reproduction (AR). Every year thousands of people seek treatment, with success rates ranging from 35% to 40%. The way of assessing an embryo for intrauterine transfer is still carried out by means of morphological parameters, a traditional methodology that brings little information about embryo physiology. Analyses of embryo metabolic activity seem to be excellent predictors of embryo viability and implantation potential. This methodology is still new and experimental, presenting some degree of operational difficulty, for which reason it is not yet performed on a routine basis at major Assisted Reproduction centers. This paper intends to discuss the importance of studying the embryonic metabolome for the selection and transfer of human embryos. The use of assisted reproduction techniques has helped thousands of people throughout the world accomplish the project of building a family. Infertile couples use low- and high-complexity protocols to attain their goal of generating a healthy baby at home. However, those methods, whether of high or low complexity, still have success rates lower than 50% at the best reproduction centers  uses cytogenetic and/or molecular techniques in order to select embryos that are free of specific genetic conditions .rd day does not seem to be the best time for obtaining genetic material. On the 5th day of cultivation, when embryos are in the blastocystic stage, genetically modified cells go into apoptosis or become confined to form placental tissue. Accordingly, today, trophectoderm biopsy on the 5th day of cultivation seems to be the best option  is an analytical technique which can count and measure the mass of a large variety of gas atoms and molecules in ionized forms in a fast, selective, highly sensitive and reliable manner. MS differs from other spectroscopic techniques, such as ultraviolet and infrared rays and nuclear magnetic resonance spectroscopy, which are based on measuring the physical events resulting from the interaction of organic molecules with electromagnetic radiation (Nuclear magnetic resonance spectroscopy (NMRS) is one of the commonest, most widely used spectroscopic techniques used for analyzing the metabolome, based on the magnetic properties of atomic nuclei. This technique provides a multivariate analysis approach by non-destructively examining tissue and biological fluids , in addition to the purchasing cost of equipment.However, the prospects are that after the standardization of a proper technique, it will be internationally accepted and become increasingly simpler, as well as a routine procedure over the course of time.


To provide services safely to refugees during the COVID-19 pandemic, humanitarian non-governmental organizations (NGOs) have instituted public health safety protocols to mitigate the risk of spreading the SARS-CoV-2 virus. However, it can be difficult for people to adhere to protocols under the best of circumstances, and in situations of nested crises, in which one crisis contributes to a cascade of additional crises, adherence can further deteriorate. Such a nested crises situation occurred in Beirut, Lebanon, when a massive explosion in the city injured or killed thousands and destroyed essential infrastructure. Using data from a study on COVID-19 safety protocol adherence during refugee humanitarian assistance in Lebanon, Jordan, and Turkey, we conduct a cross-country comparison to determine whether the nested crises in Beirut led to a deterioration of protocol adherence–the “fragile rationalism” orientation–or whether adherence remained robust–the “collective resilience” orientation. We found greater evidence for collective resilience, and from those findings make public health recommendations for service provision occurring in disaster areas. To provide services safely to refugees during the COVID-19 pandemic, humanitarian non-governmental organizations (NGOs) have instituted public health safety protocols to mitigate the risk of spreading the SARS-CoV-2 virus. However, those protocols are not always followed, with a number of mitigating conditions presenting barriers to protocol adherence. This is especially true in locations where political instability, conflict, and economic hardships are prevalent. Given that the vast majority of refugees have sought protection in low- and middle-income countries that are often vulnerable to these kinds of circumstances, humanitarian stakeholders need to consider how such mitigating conditions might shape COVID-19 safety protocol adherence.On the evening of August 4, 2020, a massive explosion in a warehouse along Beirut's port occurred that leveled a good portion of the city and caused major disruptions in a number of city services and destruction of physical infrastructure, including the destruction of three hospitals. Several days after the explosion and following protests over government mismanagement, the Lebanese government leadership stepped down. The explosion and political instability increased currency volatility of the Lebanese pound, exacerbating what was already a crisis situation for Lebanese citizens and the large number of refugees living in the country.This paper is part of a larger study on COVID-19 protocols during refugee assistance in Turkey, Lebanon, and Jordan, in which we examined the adherence to protocols designed to reduce the risk of SARS-CoV-2 infection  during the summer of 2020. Because the Beirut explosion happened at the approximate halfway point during the data collection, we were able to analyze protocol adherence before and after the explosion, comparing Beirut to other parts of the Middle East. In this way, we can ascertain the probable effects of the explosion on COVID-19 protocol adherence. This paper addresses the question, is the Beirut blast associated with a change in adherence to COVID-19 prevention protocols by refugees and service providers?behaviors. Marck et al.  has been available in all three countries, and commonly used by humanitarian NGOs while serving refugees. Due to both devaluation of the Lebanese pound and increased demand, the cost of PPE increased dramatically during the summer of 2020. This included face masks, making it more difficult for refugees in Lebanon to afford masks and leading to the inability of many NGO service providers to make masks available to refugee clients who arrived without them.The pandemic arrived on the heels of close to a decade of refugee flows not matched since the first part of the Twentieth Century . The humThe explosion of stockpiled explosives at the Port of Beirut, Lebanon was preceded by years of dysfunctional, corrupt, chaotic governance that even before the pandemic of 2020 had become increasingly untenable . PoliticThis study uses data collectedData were collected from interviews with NGO staff on how well-refugees and staff practiced social distancing (keeping 2 m distance between each other), wore face masks, and washed or sanitized hands and surfaces during services provided to refugees. Fifteen data collectors conducted interviews, asking a series of closed-ended and open-ended questions to staff either in person, over the phone, or in a few cases through video conferencing. The data collectors asked questions about how frequently safety protocols were followed based on a Likert-type scale; All of the time, Most of the time, Some of the time, or Very little of the time. The questions referred to the services that the staff provided either earlier that day or the previous day (depending upon what time the interview was conducted). Staff were asked to reflect on how frequently refugees maintained social distance and wore masks, how frequently staff followed these protocols around refugees and around other staff, and then how frequently the interviewee personally followed these protocols, all during the specific service referenced in the interview. Staff were also asked how often refugees washed their hands before, during, and after that service, how often refugees used hand sanitizer before, during, and after that service. Staff were also asked about those same hand hygiene protocols for other staff.In addition to the three primary safety protocol behaviors, we collected data on the location where services were provided, the day of the interview, the type of service, and the refugee populations served. Data collectors entered the interview responses into a Qualtrics database, so that data monitoring could occur in real time throughout the data collection period given the geographic expanse of the research team and study populations.Using interviews as the observational unit, we constructed comparisons that allowed us to identify similarities and differences in protocol adherence along axes of time, resources, and regions. The findings described in this paper are based on interviews conducted about services in Beirut (319 interviews), comparing those to interviews about services in Turkey (464 interviews) and Jordan (209 interviews). Among 319 interviews conducted in Beirut, 127 (40.8%) of them were the first interview with this certain staff, while 192 (59.2%) of them were at least the second interview conducted with the same staff. In Turkey, among 464 interviews, 423 (91.2%) of them were the first interviews with the staff while the remaining 41 (8.8%) were at least the second time when the same staff was interviewed. For Jordan, among 209, 127 (58.3%) of them were the interviews where the staff was interviewed for the first time, while 83 (41.7%) interviews were at least the second time with the same staff. Interviews were conducted between July 6 and September 15, 2020. Using the date of the interview, we constructed a variable indicating the number of weeks from the start of data collection. Because there were a small number of interviews during the first 2 weeks of data collection, we start week 1 on July 20 and include the next 8 weeks. Measuring time in this way rather than measuring time as a binary (before vs. after the explosion) allows us to observe trends that predated the explosion, so as to avoid attributing changes over time to the explosion that actually started well beforehand. For each protocol, we assigned a numeric value to the four categories of protocol adherence: All of the time = 4, Most of the time = 3, Some of the time = 2, and Very little of the time = 1. For each week, we calculated the average in responses to the frequency of protocol adherence, for a value ranging from 1 to 4, with a higher number indicating better adherence. We examined resource availability comparing Beirut to Turkey and Jordan, and protocol adherence region-wide and comparing Beirut to Turkey and Jordan. We excluded parts of Lebanon outside of Beirut, which may have experienced some ancillary effects of the explosion but would not have been as acutely affected. With a focused comparison of Beirut to Jordan and Turkey, we avoid de-emphasizing the effects of the explosion that may have also impacted other parts of Lebanon but to a lesser extent.Soap, water, and hand sanitizer were broadly available during service provision across the region both before and after the explosion. We first analyze protocol adherence over time across the entire region. This provides an overall picture in patterns of adherence. The results are presented in Mask wearing improved markedly among refugees, going from an average of 2.60 during the first week to 3.70 during the last week. Staff mask wearing remained high throughout the period but did increase over time in staff wearing masks around other staff.Our measures of hand washing and sanitizing included how frequently refugees and staff followed these protocols before, during, and after services. Hand sanitizer use and hand washing showed similar patterns for refugees and staff, so we show only the results of the former. Refugees were more likely to use hand sanitizer before services, and least likely during services. Staff were more likely to use hand sanitizer after services, and least likely to use it during services.Refugees much more frequently used hand sanitizer than washed their hands, particularly before the start of services. The average for refugees using hand sanitizer before services started at 2.92 and increased to 3.29 by the final week (down slightly from 3.33 during week six).Staff were better at using hand sanitizer compared to refugees, but changed very little over time. Staff's use of hand sanitizer before and after services was consistent throughout the data collection period. While there was some fluctuation in hand sanitizer use during services, adherence during the last week was nearly the same as the first week.To analyze the effects of the explosion in Beirut, we compare adherence over time in Beirut compared to Turkey and Jordan. The explosion occurred at the beginning of week 3 (which included August 3–9). Thus, if the explosion affected protocol adherence, we would expect to see that effect starting in week 3 or week 4.10. We found four general patterns in adherence to protocols across the 8 weeks of data collection; (1) very little change occurring over time, (2) variable change over time in which adherence was worse in Beirut than in Turkey and Jordan, (3) consistent improvement over time in which adherence was better in Beirut than in Turkey and Jordan, and (4) a notable decrease in adherence in Beirut that corresponded to the time of the explosion, with adherence rebounded by the final week of data collection. We present figures that are emblematic of the second, third, and fourth patterns.Because of the large number of comparisons in these analyses, we limited our presented findings to a select number of figures . We present those analyses in Refugees and staff adherence to social distancing demonstrates a pattern of uneven adherence over time, and ending with adherence in Beirut being worse than in Turkey and Jordan. For example, with social distancing refugee adherence in Beirut fluctuated slightly, ranging from 2.60 in week 6 to 2.25 in week 8, ending with worse adherence compared to Turkey and Jordan. The decline started in week 5, not in week 3 when the explosion occurred. These findings are presented in Staff adherence to social distancing from refugees decreased after the first week in both Beirut and Turkey/Jordan. In Beirut, adherence continued to decline until week 6, and declined again in week 8. In Turkey and Jordan, there was a general increase in staff's adherence to social distancing from refugees in week 4, ending with better adherence in the final week compared to Beirut. These results are presented in For mask wearing, adherence in Beirut was better overall compared to Turkey and Jordan, and increased over time. This was particularly true for staff wearing masks around refugees up until the final week when adherence in Beirut and Turkey/Jordan converged. The increase began prior to the explosion and does not seem related to the event. There was a decrease in adherence to all mask wearing protocols in the final week in Beirut, but no change around the time of the explosion in week 3. In Turkey and Jordan, mask wearing by refugees increased sharply from the first to last week, increased somewhat over time for staff wearing masks around other staff, and remained mostly flat for staff wearing masks around refugees. Even with the increases in mask wearing protocol adherence over time, Turkey and Jordan still had less consistent adherence compared to Beirut. These results are shown in For hand hygiene, we examined changes over time in refugees' and staff's washing hands and using hand sanitizer before and after services. Refugees' and staff's adherence to washing hands prior to services was higher in Beirut and improved over time. The improvement occurred largely after the explosion, between week 5 and 6. A similar pattern emerged in hand washing after services. By contrast, in Turkey and Jordan refugees washing their hands before services decreased over time, and refugees washing their hands after services remained flat. For staff, washing hands before and after services changed very little over time in Turkey and Jordan. In In hand sanitizer use we saw the first clear evidence of a decrease in protocol adherence in Beirut that corresponded with the port explosion. There was little change over time in refugees' use of hand sanitizer before services, but in using sanitizer after services there was a marked dip in refugees' adherence in Beirut between weeks 3 and 4. A similar pattern was apparent for staff in hand sanitizer use both before and after services, although the dip was much smaller for staff. By contrast, in Turkey and Jordan hand sanitizer protocol adherence either changed little between weeks 3 and 4, or it improved. However, in all cases the protocol adherence in Beirut rebounded back to pre-explosion levels, although refugees' adherence to those levels remained below those in Turkey and Jordan. The most dramatic changes were seen in refugees' use of hand sanitizer before services, which we show in While one might expect the massive explosion in Beirut to have a broad detrimental impact on refugee service provision in the city, we found little evidence that the challenges service providers undoubtedly faced had any discernible effect on the hand hygiene resources available nor detracted from the ability of refugees and staff to adhere to COVID-19 safety protocols. On the contrary, protocol adherence during services in Beirut was sometimes better than in our sampled service locations in Turkey and Jordan, and decreases in protocol adherence that occurred did not always directly correspond to the week when the explosion happened. The only instance in which we saw a decrease in protocol adherence in Beirut that corresponded to the explosion was in the use of hand sanitizer, and even in that case protocol adherence improved to near or better than pre-explosion levels by the end of our study period.Across the region there were general improvements in protocol adherence, particularly among refugees, suggesting that over time people in these service centers become better acclimated to following safety protocols. Our data show that even in the refugee communities in Beirut, there was a similar pattern of acclimation. Our data indicate that the explosion, despite clearly disrupting many aspects of economic and social life, did not lead to a major sustained disruption to improved protocol. Contrary to what would be predicted by the frame of fragile rationalism and much of the literature on health behaviors during nested crises, we did not see a decline in protocol adherence that corresponded to the timeline of the Beirut explosion. Instead, we see evidence of a collective resilience of Beirut's residents that led to steady improvement in adherence to some protocols even with the explosion. Thus, we found support for the collective resilience orientation that Drury et al.  describeWhen reflecting on the events, our project team members in Lebanon noted the resilience that people in Lebanon have had to develop as a result of multiple, nested crises. The COVID-19 pandemic is experienced by the Lebanese people as a disaster nested within political and economic crises. The explosion, while it led to devastating loss of life and destruction of infrastructure, was just one more crisis nested within the challenges wrought by pandemic, political instability, and economic volatility. Because of this, the explosion did not create the shock effect that it might have if it had occurred in a location that was not already facing multiple challenges.Our project team's own resilience supports this orientation. While our team in the United States expected data collection in Beirut to slow down following the explosion, our data collectors in Beirut continued to collect data and conducted more interviews in the 2 days following the explosion than the 2 days prior. This occurred even though one of our supervising NGO coordinators in Beirut was attending to damage incurred to her home because of the explosion. While there were new challenges presented by the explosion, our empirical findings and project team experience supports an interpretation that withstanding multiple nested crises builds resilience among people and institutions that protects against “shock” events like that of the Beirut explosion.While our findings are compelling, there are limitations to this study. These data come from interviews with NGO staff and thus represent their recollection and interpretation of protocol adherence. While this project did include direct observations of protocol adherence, that component was started later in 2020 and very few observations occurred before the explosion. The specific staff sampled each week depended on a number of factors including availability to give an interview and the kind of service they were leading (with the intent of sampling from a range of service types). Because staff were not randomly chosen for interviews, there is likely some unmeasured noise in who completed interviews on any given day and their perceptions of protocol adherence. However, we do not have any reason to suspect that unmeasured variables correlated with service locations, and so should not affect the relative adherence between the different sites. But we have no way of determining if the explosion itself might have affected how staff in Beirut recalled protocol adherence during their services. Future research on nested crises testing the collective resilience vs. fragile rationalism orientations should attempt to utilize objective measures of their outcomes, either using direct observations or video recordings, to control for effects a crisis has on how people remember and report a given outcome.There are several recommendations emerging from our research. First, while catastrophic disasters are often deeply disruptive, this analysis supports a policy of staying the course in terms of maintaining delivery of services and the basic health protocols around those services. Regardless of the disruption caused by the explosion, the NGO service providers still seemed to understand the importance of continuity in delivering medical, health, education and other refugee services—and there was no indication that those services were less well-utilized by the refugees themselves. The maintenance of COVID-19 prevention behaviors by both service providers and recipients indicates the interest in delivering and receiving services. We, therefore, recommend that donors continue funding agencies for continuity of deliverance of services to refugees. The NGOs participating in this study are embedded in communities and are personally known by service recipients, and our data indicated that the recipients and NGOs maintained relationships of trust despite the evident mistrust between the Lebanese government and the people in Lebanon. During times of crisis, this trust might be more important than peak functioning physical infrastructure.Second, we noted that our data collectors actually increased data collection after the disaster. Indeed, the data collection and the meetings with our international research team seemed to provide a needed maintenance of routine and purpose in the midst of the post-explosion chaos. This leads to the recommendation that research organizations involved in evaluation and study of humanitarian assistance follow the lead of those on the ground. It may well be the case, in the context of the cascading crises like in Lebanon, that local researchers benefit from continued work even in the wake of a catastrophic event. The continuation of routine and the reason for contact with those outside the local context may well be welcome. Third, in the context of multiple-cascading disasters, donors and humanitarian agencies should not assume that practices on the ground will change dramatically in the wake of a major disaster that makes international media headlines. For the Lebanese people, the explosion was disruptive and caused loss of life and humanitarian infrastructure, but it was only the most recent in a long experience of crises. The resilience of the Lebanese people is inherent in understanding the need to carry on with day-to-day tasks amidst apparent catastrophe.Lastly, we recommend that humanitarian actors normalize evidence-based health practices within service provision such that these practices become habit, especially during times of nested crises. Those norms can become protective habits against the disruptive effects of future shock events, such that even in the face of additional disasters, service providers and recipients will continue to follow safety protocols.The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.The studies involving human participants were reviewed and approved by Institutional Review Board, Michigan State University. Written informed consent for participation was not required for this study in accordance with the national legislation and the institutional requirements.SN, EK, and SG contributed to research design and implementation, data analysis and interpretation, and writing manuscript. RM and AG contributed to research design and implementation, interpretation of results, and writing manuscript. SM-P contributed to data analysis and writing manuscript. All authors contributed to the article and approved the submitted version.Funding for this project was provided by Elrha Learning and Research for Humanitarian Assistance and Michigan State University (grant #51551).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.