A growing number of articles have identified and reported the benefits and importance of urban green spaces for improving human well-being, but there is a significant knowledge gap regarding the impact of urban green spaces on the subjective well-being of older adults. The literature search (August 2015–August 2022) was derived from two major scientific databases, Google Scholar, and Web of Science. As a result, 2558 articles were found, 1527 of which were retrieved from WOS and the rest from Google Scholar. Bibliometric methods and VOSviewer software were used to screen and organize the articles in the relevant fields. Finally, 65 articles met the review criteria. The included studies aim to capture the benefits of various features of urban green spaces in meeting or enhancing the subjective well-being needs of older adults. The results of our review further support the existence of a strong link between older adults’ subjective well-being and various features of urban green spaces, providing new insights for future in-depth reexamination and policy development. Furthermore, the relationship between urban green spaces and older adults’ subjective well-being depends not only on the urban green spaces themselves but also on the characteristics of the older adult population that uses them. Urbanization and aging are occurring and growing at an unprecedented rate and are key challenges for most countries worldwide. Urbanization leads to more people living in urban areas , and urbResearch on the origins of subjective well-being was first prevalent in the fields of educational psychology, gerontology, marital success, and epidemiology. Diener 2012) coined the term subjective well-being as people’s evaluation of their own lives, well-being, and a sense of purpose . Subject coined tUrban green spaces have been identified as being relevant to promoting human health and enhancing well-being . In receA framework for the potential impact of urban green space on mental health has been succinctly summarized, from attention recovery theory to the sense of place framework to stress reduction theory. Evidence from an epidemiological perspective also implicates urban green spaces in improving residents’ general physical and mental health . Some reDespite reasons to believe in the positive impact of urban green spaces on human health  and well-being, and the significance of their use, due to the comprehensive relationship between urban greenspace use and subjective well-being, these articles did not conclusively demonstrate which characteristics of urban green space play a constructive role in improving the subjective well-being of older people, which is a particularly significant omission. Therefore, the main goal of this systematic review is to fill this need: seeking to understand the association between specific characteristics of green space and the subjective well-being of older people to help urban designers improve the design of urban green spaces and to help governments develop green space policies that are responsive to vulnerable groups. In pursuit of our primary objective, we also investigated a second objective, namely the influence of socio-demographic characteristics of different older people regarding their perceived green space and self-reported well-being. We expect these findings to develop further a deeper understanding of the relationship between urban green spaces and the health and well-being of older adults.Which characteristics of urban green spaces may influence older people’s subjective well-being?Which sociodemographic characteristics have implications for older people’s access to subjective well-being and perceptions of urban green spaces?To this end, this paper aims to address the following research questions:In this study, a systematic search of the literature review was conducted. A systematic review is a research method that aggregates multiple studies based on specific criteria to provide high-quality evidence . We seleIn August 2015, the Second World Assembly on Aging was held by the World Health Organization in Madrid, Spain, and the Global Report on Aging and Health was released, formally introducing the critical concept of healthy aging. Therefore, it is significant that the starting point for inclusion in the review was defined in August 2015, as mentioned earlier. The review aims to examine the important theoretical contributions since 2015 on the role of urban green spaces in influencing the subjective well-being of older people and in establishing insights for future research. Our review study follows the topical information of the times, fits the key trends of social development, and provides a scientific basis for promoting the sustainable development of aging and the aging industry. Clarifying the research cycle of the paper was the first inclusion criterion of this review study.The inclusion criteria were (1) English-language articles published from August 2015 to August 2022; (2) peer-reviewed studies; (3) surveys or qualitative studies; and (4) the primary research focused on urban green spaces and the subjective well-being of older adults. The exclusion criteria were (1) articles published before August 2015 and after August 2022; (2) editorials, opinion pieces, and non-research papers; (3) non-English language articles; and (4) research content not related to urban green spaces or the well-being of older adults, such as the well-being of young people.Of the total number of publications surveyed, 2558 references were from Google Scholar and 1527 references from Web of Science. Approximately two-thirds of the literature was removed because it depended heavily on the relationship between the variables . After excluding these studies, 452 articles were left to be read in detail. Next, conceptual studies or studies without a relevant empirical component were excluded to obtain more evidence with empirical support. Finally, 65 articles were included in the literature review analysis for thematic analysis. Most of these articles were from English language journals, with five being in Chinese. More information about these studies is detailed in Based on the search outcomes, three authors extracted the data and resolved disagreements by consensus. Extracted data included sample characteristics , study design , spatial characteristics of urban green spaces, green characteristics of urban green spaces, green features of urban green spaces, and socio-demographic characteristics of the elderly. VOSviewer is a free JAVA-based software focusing on visualizing scientific knowledge . The mosVOSviewer software was used to analyze and assess the hotspots and knowledge clusters of this study. By importing the bibliometric dataset, visual plots of keywords co-occurrence analysis, common country network analysis, and coupling analysis can be generated.The visualization of the term maps is provided in both This study not only presents the associations and results between three main characteristics of urban green space and the subjective well-being of older people but also analyzes the relationship between the perception of green space and the subjective well-being of older people from the perspective of sociodemographic characteristics. There is no doubt that only a few articles met the review criteria, mainly because many studies were conducted on younger people and were inconsistent with measures of well-being. The results of the study provided a comprehensive analysis of the literature from two major databases (Google Scholar and Web of Science) since August 2015 that are highly relevant to the research topic. The results of the review are presented in two themes to reflect the influence of three main characteristics of urban green spaces  and sociodemographic characteristics on the perception of green spaces and the subjective well-being of older people.This section first presents the findings on the study characteristics of the two research themes. The second section describes the findings of the study on the correlation between spatial characteristics, green characteristics, and gray characteristics of urban green spaces and the subjective well-being of older people.N = 24) originated from European countries; with 22% (N = 11) and 20% (N = 10) being from Asian and American countries, respectively; the remaining 10% of the articles (N = 5) belonged to Australia. Close to half of the studies relate to Europe. However, the locations of South America and Africa were excluded from these studies. From a research content perspective, four articles concerned the three main characteristics of urban green spaces [N = 19), green characteristics (N = 13), and gray characteristics (N = 9). Seen from the perspective of research methods, quantitative research methods, including surveys, questionnaires, and regression analysis, were used in 68% of the papers (N = 34). Qualitative research methods, including bibliometric methods, case studies, interviews, and meta-analysis, were applied in 30% of the papers. A mixed approach of social prescribing approach was conducted in only 2% of the papers (N = 1). In addition, the study sample sizes varied from 15 to 36,368 individuals. All study characteristics for the first research theme are shown in The first research theme was to investigate the association between the spatial characteristics , green cn spaces ,48,49,50n spaces ,52 and gn spaces ,54, and n spaces . The resN = 3), the United States (N = 3), and Australia (N = 4). Moreover, our review revealed that the survey method was the most conducted research method (53.33%). In addition to the survey method, reviews, case studies, cohort studies, ordinal regression, and bibliometric methods were also widely applied in this area of research. Study sample sizes ranged from 100 to 24,954 individuals. All study characteristics for the second research theme are shown in The second research theme was to examine the influence of sociodemographic characteristics of older people on their perception of green space and subjective well-being. A total of 15 articles were included in the review. Five articles (30%) originated from European countries ; the remaining 10 articles were from China (N = 6), systematic reviews , or original scholarship . Area, size, type, location, distance to park, quantity, quality, availability, accessibility, safety, frequency, and duration as spatial characteristics of urban green spaces are used to decipher their association with the subjective well-being of older people. It is worth noting that accessibility is considered the most significant green space feature affecting the subjective well-being of older adults, as it is mentioned and analyzed in detail in 17 articles (65.38%). Accessibility is identified as essential place support to encourage older people to participate in green space and engage in physical activity. N = 13) and size  of parks are remarkably connected to the experience and perception of green space among older adults. The richness of green space type and scale is described in detail as providing diverse spaces for physical activity and social interaction and increasing the likelihood that older adults would use green space. Over 40% of the articles emphasize the many benefits of park size , distance to home , and quantity  on older adults’ mental health. The larger the area of green space and the closer the distance to home, the more significant the health benefits of green space. An increase in the number of parks shows a positive correlation with psychological well-being. In addition, more than 30% of the articles reveal correlations between the frequency of greenspace visits and duration of stay , quality , location , and availability , and the impact of these characteristics on older adults’ self-reported health and well-being. Secondly, more than half of the papers report that the type  mention the perception of safety. However, the final review shows that most articles combine the dimension of the perceived safety of green spaces and gray features of green spaces, perhaps due to the interesting finding that older adults use more gray facilities  in green spaces when visiting them. The above results highlight that the spatial characteristics of urban green spaces can provide benefits and specific uses for older adults and can influence potential benefits for older people, such as higher levels of social support.N = 7). The literature review in this area reveals that 90% of the articles (N = 18) identify biodiversity conservation as a green feature of urban green spaces and as the green indicator most strongly associated with the subjective well-being of older adults. There is a strong correlation between perceived biodiversity and measures of the health of older adults. This is followed by vegetation richness, an indicator mentioned in 65% of the articles (N = 13), where rich plant communities not only support and promote biodiversity in green spaces but also promote positive socio-ecological outcomes in green spaces. Purifying the environment and providing aesthetic spaces are considered essential features of urban green spaces that can significantly contribute to ecosystem services and promote the physical and mental health of the elderly, a message we observed in 45% (N = 9) of the papers. In addition, improved urban microclimate , water resources , bird and animal species richness , and socio-cultural integration with landscape ecology  are also widely noted green features of green spaces as effective factors that can enhance well-being at the sensory levels of sight, hearing, and touch, reduce anxiety levels, and can promote more positive responses. Maintaining carbon and oxygen balance is assessed and analyzed by 30% of the papers (N = 6) as the primary green feature of urban green space, and it is concluded that maintaining carbon and oxygen balance reveals the correlation between urban green space and subjective well-being of older adults from an ecological perspective. Moreover, 25% of the papers (N = 5) mention urban noise as one of the main threats affecting the self-reported well-being of older adults and urban green space as a natural buffer zone. Its noise reduction function can directly or indirectly affect the life satisfaction and subjective well-being of older people. Finally, it is fortuitous that a logistic regression study from China  examines earthquake mitigation as a green indicator, which is the only article (5%) that mentions an association between earthquake mitigation and older adults’ well-being. The results of the review suggest that green features of green spaces have a non-negligible role in reducing environmental pollution, reducing life stress, relieving pain, improving sleep, providing visual stimulation, and improving mental health. The findings of this review on studies related to the green characteristics of urban green spaces and the well-being of older people provide a theoretical basis for future research.A total of 20 articles ,81,82,83N = 13) as influential gray facility that influences older adults’ visitation and use of urban green spaces, playing an important role in attracting visitors and promoting visitation rates. In addition, we observe that pavement conditions in urban green spaces are as important as rest facilities in influencing the well-being of older adults . Path and pavement conditions are the main aspects that reflect the inclusive design of urban green spaces and park accessibility. This result suggests that paths as gray facilities in urban green spaces are strongly associated with the perceived safety and well-being of older people in green spaces. Furthermore, 64.7% of the papers (N = 11) assess the importance of providing accessible green spaces, as this factor determines the safety and comfort of older people engaging in physical activities and social interactions in urban green spaces. In contrast, lighting facilities (N = 9), safety facilities (N = 9), recreational facilities (N = 10), sanitation facilities (N = 10), and campus management centers (N = 10) are analyzed in closer proportions  in terms of their relevance in supporting the health and well-being of older adults. In addition, sports facilities (N = 6) and directional facilities (N = 6) are considered necessary aspects to keep urban green spaces in good condition. Finally, only 23.5% of the papers (N = 4) consider that landscape facilities affect the perception of green spaces and the well-being of the elderly.Similar to the content validation studies on measures of well-being in older adults, it was emphasized that age, gender, marital status, education, pre-retirement employment, and income need to be considered as essential factors in evaluating well-being in older adults. Cohort studies in the United States and Australia have indicated that psychological distress and general health deficits are more prevalent among older adults, women, and those with low education, low income, or not working. In a cross-sectional study in the Netherlands, which included age, marital status, education, and income as background variables for older people, these demographic characteristics were found to be associated with high scores in all quality-of-life domains, while women scored lower in physical health and psychological aspects. Studies in China have also suggested that older people who continue to work after retirement have better economic and physical health than those who do not work after retirement, but their mental health is lower than the latter. In terms of gender-related perceptions, men and women expressed different expectations and sensitivities regarding their perceptions and experiences of urban green spaces and public spaces, with women being more willing to spend time in the community and to be more integrated into the community’s green space.Using thematic analysis, we grouped the collected articles according to topics: (1) Quantifying the characteristics of urban green spaces, including their spatial, green, and grey characteristics. We analyzed the positive and negative effects of the different characteristics of urban green spaces on the subjective well-being of older people. 2) Reviewed the sociodemographic characteristics of older people and their effects on subjective well-being. Based on our review, we can conclude that urban green spaces would be a corollary to the positive association in promoting health-related behaviors and subsequent positive health outcomes among older adults. Changes in sociodemographic characteristics may also contribute to the fact that older adults have inconsistent perceptions, preferences, and use of urban green spaces. Although the review methodology and exclusion conditions differ, our results are consistent with recent findings. Urban green spaces are an important factor affecting the physical and mental health of older adults  Reviewed. In the This paper presents the findings of a review investigating the relationship between urban green spaces and subjective well-being from the perspective of older people. Despite a growing body of articles identifying and reporting on the benefits and importance of urban green spaces in improving human well-being, the available evidence on the role of urban green spaces in influencing older people’s subjective well-being is under-captured, leading to potential gaps in our understanding of older people’s use and perception of urban green spaces concerning their physical health, psychological well-being, and subjective well-being. Which characteristics of urban green spaces may influence older people’s subjective well-being, and what is the impact of sociodemographic characteristics on older people’s perceived urban green spaces on their subjective well-being? The preconditions that influence the use of urban green spaces are their size, quantity, and quality . In geneThe choice and use of urban green spaces by older people can promote a variety of health benefits, such as increased physical health through participation in physical activities in parks in green spaces ,68,111 aIn addition, for older people living in more socio-economically disadvantaged communities, their consideration of the accessibility, reachability, and safety of urban green spaces also needs to be addressed. This is because the access to urban green spaces that can be identified by GIS is not necessarily applicable to older people in the analyzed areas. Examples include high-end private gardens or golf clubs. Policymakers and urban planners are keen to commission the expert design of urban green spaces. However, from the perspective of designing complexity for the real world, urban green spaces are hardly ever designed to provide any specific health benefits due to a lack of clarity about which specific features of urban green spaces provide benefits for specific groups of people, such as older people. As Lee et al. ,70 pointThe 11 studies related to the green features of urban green spaces and the subjective well-being of older adults have been summarized in our review. Vegetation is the only primary producer in urban ecosystems and is considered to be an important component of terrestrial ecosystems and urban landscapes . The natA cost-benefit and utility analysis of urban green elements from an economic perspective allow for methods and tools to economically assess the value of urban green to address all uses and co-benefits ,115. UrbContact with nature, such as lushly vegetated parks or streetscapes, can promote rational mechanisms for many health benefits ,120, whiTo sum up, the findings of the review on the positive impact of green characteristics of urban green spaces on the subjective well-being of the elderly show that there is a strong correlation between the two, which has important design implications for urban designers and landscape planners. Designing rich plant communities is an essential design element to support the biodiversity of green spaces and a reasonable mechanism to purify the air, improve urban microclimate, and promote the health of the elderly. Increasing green natural landscapes and rich natural systems meet the requirements of the elderly for natural recreation and spiritual entertainment. Green elements can help seniors relieve stress, reduce loneliness and depression, and thus improve overall well-being. Moreover, designers need to pay attention to the implications of the richness of bird and animal species on seniors’ experience and perception of green spaces, which was an unexpected finding in our review study that urban green spaces not only provide habitats for plants and animals, but also enhance ecosystems and improve the living environment, and thus contribute to seniors’ mental health and well-being. Lastly, the aesthetic function of green spaces cannot be ignored, and designing urban green spaces that meet the aesthetic desires of the elderly is an initiative to enhance the quality of life and health, and well-being of the elderly.The gray infrastructure of urban green spaces refers mainly to the network of facilities such as roads, accessible design, lighting systems, and street furniture in green spaces. Increased mobility has a direct impact on the quality of life of older people , hence tThe design of urban public and green spaces, especially regarding the specific needs of older people, should be addressed ,85 to imIn addition, traffic-related air and noise pollution can directly affect the body, cause respiratory and cardiovascular health problems, and increase the risk of breast and prostate cancer. In one study, older people expressed a desire to make their experience in parks fun by ‘playing’ with exercise equipment and using other recreational facilities for stretching or even using handrails, branches, and benches to help them exercise ,88,124. Therefore, in the design of urban green spaces, attention needs to be paid to the specific needs of older people and to improve the gray infrastructure of urban green spaces through creative and friendly design and practice . These would support the secular mobility and social interaction of older people in public and green spaces and promote healthy aging, quality of life as well as their well-being in later life.Research has found that access to green space views, visits to urban parks and public spaces, access to private green spaces, neighborhood greening, and increased duration and frequency of green space exposure were associated with reduced stress and distress during the pandemic . StudiesOver the last few decades, the quality of life of older people has been at the forefront of international policy debates on aging . Health Positive self-concept about health is associated with older people’s willingness to engage in physical activity, which in turn facilitates their functional autonomy. Older people who perceive positive health are more likely to enter urban green spaces for social activities and physical activity, reducing loneliness  and imprSome studies have shown that, across family types, multigenerational families have the lowest social capital satisfaction and self-esteem scores and the highest depression scores. This finding may be explained by intergenerational differences in political orientation or economic power leading to conflict among family members . FurtherUrban green spaces positively impact residents’ physical and mental health. However, this impact may differ between older men and women due to differences in perceptions of urban green spaces between genders. The differences are in terms of safety, accessibility, species diversity, and patterns of use. Males and females also show differences in the perception and valuation of urban green space features due to the different sensitivities and expectations of males and females in terms of green space perception and experience. There are also significant differences in the perceived health and well-being of older people regarding the characteristics of urban green spaces .Nevertheless, many urban sustainable greening development strategies and green justice dimensions recognize different stakeholder situations. These studies do not consider the gender equality of older people in urban green spaces. When confronting the complexity of sustainable urban greening, it is imperative to pay attention to gender equality, especially in the context of an age-friendly society, in relation to the health and well-being of older people’s perceptions of urban green spaces. Additionally, it has been observed that boosting education and eliminating inequality in residential status are more beneficial than possessing material wealth when it comes to enhancing the subjective well-being dimension . TherefoFollowing the literature review, we also found several studies stating that older people who choose to continue working even after retirement because of the possibility of gaining social participation and social support contribute to their meaning and purpose in life. This would help to improve their mental health and well-being and reduce their mortality rates .None of the 65 articles included in the review have been analyzed for knowledge topics with the help of visualization software. In our review process, an attempt was made to combine bibliometric methods and VOSviewer software for literature screening and organization, and visual network plots could be generated to analyze the relevance of previous studies. VOSviewer software has an absolute advantage in terms of its graphical presentation capabilities, allowing the processing of large volumes of literature in databases and enabling the construction of maps for any suitable mapping technique. On the one hand, it helps to perform scientific metric analysis and interpretation of mapping language for relevant literature data in the field of review research. On the other hand, research hotspots and relevant knowledge clusters in the cross-cutting area of urban green space and elderly well-being research can be identified. Compared with previous studies, this is a bold innovation in the research methodology aspect of this review.The results of our review suggest that the positive role of urban green spaces in influencing the subjective well-being of older adults can be clearly understood by establishing links between the three main characteristics of urban green spaces and the subjective well-being of older adults. Previous studies on urban green space and well-being have had different emphases and have all contributed significantly to the study of landscape well-being. However, previous studies have not categorized the characteristics of urban green spaces. Our review study, however, differs from previous studies precisely in clarifying the characteristics of urban green spaces, forming three major categories of urban green spaces: spatial characteristics, green characteristics, and gray characteristics. In addition, the discussion section provide in-depth analysis and discussion. It not only fills the gap in this theoretical knowledge but also provides references and support for subsequent studies. This is the most outstanding theoretical contribution of this paper.In addition, most previous studies have focused on the effects of urban green space on urban citizens, and although the study sample also includes the elderly, it is not common to find articles that single out the elderly as a research group. Instead, our study focused on the effects of different sociodemographic characteristics of older adults on perceived green space and assessed well-being. Greenspace satisfaction and subjective well-being scores vary from person to person, and sociodemographic characteristics are one of the key factors in determining the impact. Thus, our review also provides theoretical support for subsequent quantitative studies.(1)The spatial, green, and gray characteristics of urban green spaces not only provide space and opportunities for social interaction, alleviate anxiety and stress, and provide improvements in older people’s mood and concentration but also have a more significant contribution to older people’s subjective well-being and high levels of social cohesion.(2)Sociodemographic characteristics also have substantial implications for older people’s subjective well-being in relation to urban green spaces. Older people’s transient perceptions, experiences, and well-being of urban green space environments are vital to the planning and design of age-friendly spaces by increasing the quantity and scale of green spaces and encouraging the optimal design of their accessibility to improve their attractiveness and suitability for older people.Our work has further supported the understanding of the relationship between the subjective well-being of older people and urban green spaces. New insights are presented for integrating urban green spaces, subjective well-being, and older people. Specifically, two aspects are included:It should be noted that there are certain limitations to the process and results of this study. Firstly, the time frame and language of article screening was the first limiting factor we encountered. We targeted our search to articles written in English between August 2015 to August 2022, which resulted in only a small number of articles (65) meeting the eligibility screening criteria. However, beyond this period, many more valuable articles on this area have been published or exist in the literature in other languages. Secondly, we conducted a literature search in a limited number of databases, such as Google Scholar and Web of Science, to present the research in a narrative synthesis. In addition, the inherent geographical and health diversity of older people, as well as the complex impact of socio-cultural, socio-economic background, and sociodemographic variables on the study, prevented us from understanding their different needs and differences in subjective well-being acquisition in greater detail. Furthermore, the measurement of urban green space characteristics was based on the presence of open and accessible green spaces and did not consider other factors that may have a bearing on older people’s access to health and well-being benefits, such as climatic conditions and air quality. Finally, this study did not consider the impact of private gardens or rooftop gardens at the front and back of the home on older people’s physical and mental health benefits and subjective well-being.In future studies, we need to establish the benefits and various limiting factors such as socio-economic factors, personal values, or cultural perceptions that older people gain from visiting green spaces from the perspective of green space use patterns and individual level. In addition, an attempt could be made to ascertain if there is an effect of different types of green space features on older people’s usage preferences through the results of an eye-movement experiment. In-depth interviews could also be used to obtain completely new data on older people’s understanding of the emotional, perceptual, and experientially defined boundaries associated with enhancing urban green spaces. Finally, relevant government departments and urban planners should pay attention to and encourage policy research related to the planning and management of green space spaces for the elderly. Attention should be paid to the results of older people’s participation, experience, and perception of various features of urban green spaces and to the development of green space policies that meet the actual needs of older people and thus contribute to their well-being.


The equiatomic CoCrFeNiMn high-entropy alloy (HEA) possesses excellent properties including exceptional strength–ductility synergy, high corrosion resistance, and good thermal stability. Selective laser melting (SLM) additive manufacturing facilitates the convenient fabrication of the CoCrFeNiMn HEA parts with complex geometries. Here, the SLM process optimization was conducted to achieve a high relative density of as-built CoCrFeNiMn HEA bulks. The mechanisms of process-induced defects and process control were elucidated. The microscale mechanical behaviors were analyzed through in situ scanning electron microscopy observation during the compression tests on micro-pillars of the as-built HEA. The stress–strain characteristics by repeated slip and mechanism of “dislocation avalanche” during the compression of micro-pillars were discussed. The high-cycle fatigue tests of the as-built HEA were performed. It was found that a large number of nano-twins were induced by the fatigue, causing a non-negligible cycle softening phenomenon. The effects of promoted ductility due to the fatigue-induced nano-twins were illustrated. This work has some significance for the engineering application of the SLM additively manufactured CoCrFeNiMn HEA parts. The concept of multi-component high-entropy alloys (HEAs) was first proposed by Yeh et al. . The numMany scholars have studied HEAs ,6,7, butThe effect of SLM process parameters on the quality of the parts has been studied in a large body of literature, including mild steels , iron-ba−1), laser spot diameter D (mm), powder layer thickness h (μm), scanning spacing H (μm), etc. In addition to emphasizing the effect of single factors on the density of SLMed parts, more scholars argue that stable part quality can be guaranteed after carefully considering all the parameters and their interactions. To comprehensively study the effect of different parameters on SLM, the concept of energy density [3). The most common energy density equation is as follows:d is the layer thickness, and Nearly 130 factors affect the quality of the final parts , among w density  is introSeveral AM methods have been successfully implemented to fabricate structures with HEAs. Some scholars have developed and manufactured HEA parts by SLM . For exaGenerally, the SLM has made significant progress in the past 20 years. However, there is still a significant gap in developing into a mature technology, especially in productivity, quality control, and repeatability, which poses severe challenges for critical components . MoreoveIn this research, by investigating the SLM process of Cantor HEAs, the density of the parts can reach up to 98.87%, but the density of the parts will slightly decrease when the laser energy density continues to increase, and finally stays at about 97%. This research also finds that laser rapid non-equilibrium melting and solidification lead to that a large number of nano twin crystals induced by fatigue stress existing near high-density low-angle grain boundaries and micro-plastic deformation and ductility are improved in the low-load high-cycle fatigue process and provides a theoretical basis for controlling SLM forming quality of Cantor HEAs.A professional SLM device is used in the experiment, including a laser beam system, mechanical motion system, control system, scanning system, material delivery system, and atmosphere protection system. Its parameters are presented in 10 = 24.6 μm, D50 = 36.2 μm and D90 = 55.8 μm, respectively. The scanning strategies of this paper are based on the recommendations of the literature [In this research, the CoCrFeNiMn spherical powder produced by gas atomization is provided by Jiangsu Vilory Advanced Materials Technology Co., Ltd. , and its size is Dterature . The filThe density can be measured in many ways. By comparing the advantages and disadvantages of the Archimedean method, helium pycnometer method, and cross-sectional micrograph method in measuring the density of SLMed parts, the literature  concludeThe mass of parts is measured by analytical balance with an accuracy of 0.1 mg. As shown in A traditional plate specimen is used as an experimental object, and its external dimensions are shown in To better analyze the quality of SLMed parts, an essential indicator for judging the properties of parts is introduced, namely density. The processing parameters  directly determine the density of the parts. The samples were built in a wide range of laser powers and scanning speeds in this work. The corresponding volumetric energy density is calculated by Equation (1), and the relationship between relative density and laser energy density is shown in 3 and other process parameters are constant, the density of the formed components significantly increases with increasing laser energy density, which is consistent with the results of other studies [3, the density of the parts is the highest, up to 98.87%. When the laser energy density further increases, the density of the parts decreases slightly and is finally kept stable at about 97%.As shown in  studies . When thIn When the laser beam scans through loose powder, the laser irradiates several powder particles simultaneously (Stage I), heating the particles. Subsequently, heat flows to the center of the particle until the particle temperature is locally steady . Only thUnder laser irradiation, the melt in the molten pool inevitably splashes to either side of the molten pool, forming spherical metal or ablating into the forming surface and forming tiny pores. Some pores are formed during subsequent powder spreading, melting, and solidification, as shown in The pores are mainly caused by moisture or contaminants on the surface of the powder particles , such as2. Pores are included in the parts under the gas retention effect.Small amounts of oxygen and carbon in HEAs can react at high temperatures to form gaseous products, such as CO or COIn addition, the particle size and the shape of powders are critical in reducing the number of defects in built-up layers ,47.3. In this case, most pores of the parts are round (diameter ≤ 10 μm), as shown in The laser energy increases with increasing laser power. On the one hand, as the metal powder can absorb more energy, more powder particles are melted, and the amount of generated liquid is increased accordingly, even if the solid powder is not melted, thus improving the overall mobility, filling the pores and reducing the porosity with the help of liquid “bridge”. On the other hand, high energy directly heats the molten pool. The liquid metal more quickly flows at a relatively high temperature, which can fill the pores generated during the manufacturing process. The part density reaches the maximum, up to 98.87%, when the laser line energy density is increased to 66.7 J/mmThe part density slightly decreases with a further increase in the laser energy density. Scholars have discovered similar phenomena in other materials . Many scAs the laser energy density further increases, especially when the laser power increases and the scanning speed decreases, the number of liquid phases increases, which generates a higher density. However, the density cannot keep increasing and tends to be stable at about 97%.An SEM in situ mechanical experimental device is used in this research to prepare a micro-scale cone structure from SLMed Cantor HEAs through FIB, as shown in The SLMed CoCrFeNiMn HEA is organized as polycrystals, and crystal atoms are arranged in order. When a load is applied to a micro-structure of these crystal structures, the crystals will experience a micro-scale slip, inherent dislocations, and new dislocations and move under stress, resulting in excessive dislocations entangled within the metal and a local strengthening effect. When the applied stress further breaks through the yield stress threshold for local dislocation strengthening, the typical “dislocation avalanche” phenomenon occurs, driving the sudden movement of the entangled dislocations, thus weakening the metal strength, which is more difficult to control and a direct physical effect on the overall macroscopic failure behavior of the materials. The SEM micro-scale stress–strain experiments under in situ observation can accurately determine the location of the “avalanche” and its relationship with the loading direction and grain orientation.Each metal atom has nuclei and electron clouds of different sizes, resulting in high distortion of the HEA lattice, which can theoretically slow down or even delay the motion of the entangled dislocations and thus store more dislocations in a relatively small volume. However, unlike traditional alloys, the HEA lattice and micro-structure accumulate more dislocation density, which also leads to more obvious “mutation” characteristics of stress and strain resulting from the “dislocation avalanche”, obviously detrimental to the sudden control of material failure.The mechanical properties of macroscopic materials and microcolumns are significantly different in dislocation motion and strengthening mechanisms due to the size effect. From the viewpoint of micro-scale mechanics, the FIB sampling location and SLM process defects directly affect the microcolumn strength and damage resistance. For microcolumn sampling in this experiment, the SLM porosity and sparse process defects are avoided, as shown in The investigation of the intrinsic strength of SLMed HEAs should exclude material discontinuities such as process defects. More focus should be put on the critical role of composition, crystal structure, grain orientation, and grain/subgrain boundaries. However, SLM forming process control plays a crucial role in improving the mechanical properties and service life of macroscopic parts. It has a certain effect on the mechanical properties of submicron and nano-scale materials. For example, as shown in Aiming to further clarify the material micro-mechanism for different cyclic softening in the high-cycle fatigue process of SLMed parts, the fatigue failure samples are analyzed by micro-area EBSD, and the sampling area is close to the fracture or crack area. As shown in The average grain size of SLM laser rapid solidification is significantly smaller than that of traditional quasi-static casting. At the same time, the intercrystalline substructure in the SLM microstructure and the aggregation of nano-oxide particles and heavy metal elements on the sub-micron and even nano-scale cell walls have a significantly higher dislocation pinning strengthening effect. More importantly, a high proportion of low-angle grain boundaries efficiently induces nano-twin nucleation under stress, and a large number of twin structures further enhance the plasticity and damage tolerance under structural strain, i.e., twin-induced plasticity (TWIP) mechanism, thus making a significant contribution to improving the plastic toughness synergy of the overall fine-crystalline SLMed parts. This can increase the strength of laser rapid non-equilibrium melting and solidification structure and play a positive role in prolonging low-load high-cycle fatigue lifetime in addition to certain or even better ductility.As the laser energy density further increases, especially when the laser power increases but the scanning speed decreases, the number of liquid phases increases, producing a higher density. However, the density cannot keep increasing and tends to stabilize at 97% or so. During the SLM process, the pre-solidified parts and micro-structures are highly susceptible to accumulated residual stresses. Internal structural defects, including microcracks, balling, and porosity, generally occur under unacceptable process conditions, which significantly affect the mechanical fatigue properties of macroscopic parts.For example, uneven structure thermal stress releasing caused by laser rapid non-equilibrium melting and solidification, uneven solid–liquid interface solidification, and remarkable shrinkage effect resulting from incomplete melting of local powder as well as mismatching laser parameters with the set thickness of powder layer are factors easily leading to buckling deformation and the generation of macro cracks in parts, or the generation of micro-cracks inside the part. Additionally, balling evoked by inappropriate laser parameters is a common defect that exerts a major effect on the quality and mechanical properties of the parts in the SLMed parts or on the SLM surface. Meanwhile, pores are frequently found in layer-by-layer laser scanning due to balling defects independent of morphological characteristics. Consequently, excessive porosity declined density, and unsatisfactory surface roughness is caused in the parts. What is more, incompletely melted local powder results from remaining pores in the molten pool, excessive laser scanning distance or powder layer thickness will also give rise to many pore defects. In particular, if the gas phase is introduced into the molten pool via the rolled winding or the laser spot pressure fails to spill before solidification in the rapid solidification of the molten pool, it will easily be remained in the solid structure, forming tiny spherical pores. The remaining pore defect is a common phenomenon in the laser “keyhole” effect. The remaining locations of the process defects in the core of the parts or the outer surface with greater roughness are potential areas susceptible to fatigue crack, which is the main cause of premature failure of the parts under fatigue load. Branch cracks in the initiation and development process are straightforward to develop again into the main crack along the defective parts and bring severer damage. Existing studies have found that core defects are the main cause of fatigue failure in terms of high-cycle fatigue of the SLM metal parts, i.e., fatigue cracks are only initiated and expanded from the core, highly different from the case where high-cycle fatigue is preferentially initiated and expanded on the surface compared with conventional forgings made of ideal materials. It should be noted that numerous studies have demonstrated that the density of the parts is increased by optimizing the SLM process parameters. The risk of premature fatigue failure of the parts is reduced through appropriate post-treatment processes, especially HIP post-treatment for entire parts, and mechanical densification/fine crystallization post-treatment for the surface or surface layer of the AM parts can significantly improve fatigue performance.It should be noted that the effect of SLM additive manufacturing microstructure anisotropy on fatigue performance is also considered. Various metal structures suitable for SLM manufacturing are comparable to their casting and forging materials in quasi-static strength. Still, their fracture toughness is generally low, and the discrete characteristics of fatigue performance test data are significant, which is not only related to process defects but also significantly related to the characteristics of the SLM microstructure. For metallic materials with a single matrix phase or main phase, the effect mechanism of grain size and its distribution characteristics, grain boundary angle distribution characteristics, grain morphology and texture, and intercrystalline substructure  of SLM part micro-structures on the mechanical fatigue performance has attracted the attention of relevant researchers. The SLMed parts present microstructural texture characteristics, and growth characteristics of columnar grains lead to significant anisotropy in mechanical properties, which directly affects the fracture behavior or the preferred orientation of crack growth; in practice, by changing the laser heat source parameters, the grain orientation can be controlled in some way to improve the anisotropy of mechanical properties, for example, higher laser energy density leads to preferential growth of FCC grains along <001>. In comparison, lower energy density leads to preferential growth of grains along <110>. The <110> grain orientation facilitates the formation of a large number of twin crystals in the austenite structure in case of deformation. It results in a higher strain hardening rate, increasing the strength limit and ductility of the structure. However, in general cases, the crystalline structure also exhibits unavoidable differences in orientation characteristics along the SLM building direction.The SLM parameter is optimized based on density. The results show that the increase in laser energy density can significantly improve the quality of the parts when other process parameters remain unchanged. The density of the parts can reach up to 98.87%, but the density of the parts will slightly decrease with increasing laser energy, and finally tend to stabilize. The part density decreases with increasing layer thickness and scanning spacing.The causes of porosity defects and the effect of process parameters are elaborated. Pore defects are caused by metal agglomeration, spatter, moisture or contaminants, gaseous products, etc.; the laser energy increases with increasing temperature and fluidity of the molten pool, in which case pore defects are easily eliminated, but the pores in the final parts cannot be eliminated due to moisture, solidification shrinkage, etc.This research analyzes the effect of different typical SLM process conditions on the quasi-static and dynamic mechanical properties, investigates the strength and toughness of the micro-scale and macro-scale samples, reveals the stress–strain changes resulting from repeated slippage in quasi-static compression behavior of micro-scale materials and “dislocation avalanche” behavior mechanism, and finds that laser rapid non-equilibrium melting and solidification lead to that a large number of nano twin crystals induced by fatigue stress exist near high-density low-angle grain boundaries and micro-plastic deformation and ductility are improved in the low-load high-cycle fatigue process.Given SLM process characteristics, this research investigates the process window of SLM forming of Cantor alloy, analyzes the effect law of different process parameters on the forming quality, microstructure, and mechanical properties of Cantor HEAs, and draws the following conclusions:


The heat enhancement in hybrid nanofluid flow through the peristaltic mechanism has received great attention due to its occurrence in many engineering and biomedical systems, such as flow through canals, the cavity flow model and biomedicine. Therefore, the aim of the current study was to discuss the hybrid nanofluid flow in a symmetric peristaltic channel with diverse effects, such as electromagnetohydrodynamics (EMHD), activation energy, gyrotactic microorganisms and solar radiation. The equations governing this motion were simplified under the approximations of a low Reynolds number (LRN), a long wavelength (LWL) and Debye–Hückel linearization (DHL). The numerical solutions for the non-dimensional system of equations were tackled using the computational software Mathematica. The influences of diverse physical parameters on the flow and thermal characteristics were computed through pictorial interpretations. It was concluded from the results that the thermophoresis parameter and Grashof number increased the hybrid nanofluid velocity near the right wall. The nanoparticle temperature decreased with the radiation parameter and Schmidt number. The activation energy and radiation enhanced the nanoparticle volume fraction, and motile microorganisms decreased with an increase in the Peclet number and Schmidt number. The applications of the current investigation include chyme flow in the gastrointestinal tract, the control of blood flow during surgery by altering the magnetic field and novel drug delivery systems in pharmacological engineering. In the current century, it has been identified that the flow of nanofluids in various geometries is a potential research area. This is due to the researchers who have ameliorated the performance of heat transfer and other characteristics by adding different nanoparticles into pure base fluids, which leads to considerable practical applications in diverse situations, such as biomedical engineering, cancer treatment thermal therapy, microelectronics, metallurgical sectors, the delivery of drugs, microchannels, power generation and micromanufacturing processes. Initially, Choi  introducChoi perhaps was the first to work on nanofluids for industrial applications; however, his research and many of the previously mentioned works were confined to unitary nanofluids (nanofluids with a single nanoparticle type). Later in 2004, Makishima et al.  propoundNowadays, research on bioconvection has received a great deal of attention due to its tremendous applications in electronic, civil, process, mechanical and chemical engineering. More specifically, bioconvection applications include cooling systems, building insulation, microreactors, micro-heat pipes and micro-channel thermal sinks. In physiological systems, bioconvection is involved in biomedical instrumentation, nano-biotechnology, microenzymes, biosensors, blood flow, nanomedicine, content detection, pharmacokinetics and drug delivery. In the past few decades, the implementation of activation energy has been much considered in some engineering advances. For instance, thermal magnetic flux, fusion control, nuclear reactor cooling, liquid metal filtration, casting and compact heat exchangers. In view of the applications of bioconvection and activation energy, several authors have started working on these crucial topics. Rekha  et al. dThe phenomenon of peristalsis is a well-known mechanism in physiological systems. It is a vital and automatic process that drives the biological liquids in the fallopian tube, duodenum, reproductive tract and many other situations. The concept of this phenomenon is exploited in many bioengineering and industrial processes, such as novel pharmacological delivery systems, sanitary fluid transport, corrosive fluid transport and blood pumps in heart–lung machines. The propulsion of hybrid nanofluids in biological systems has great importance in medical sciences and engineering. Its applications include cancer therapy and blood circulation. There is also some less well-known work on hybrid nanofluid flow through peristaltic geometry. For instance, Bhatti and Abdelsalam  discusseIn the earlier literature, authors have presented their analysis on nanofluid and hybrid nanofluid flows in various geometries, and a very few works exist in the direction of hybrid nanofluid flows in a peristaltic mechanism. We also noticed that no work has been made in the direction of hybrid nano-liquid (gold–silver–water) propulsion in a bio-channel. With this motivation, the current article deals with the flow of a hybrid nanofluid through a symmetric channel with the effects of solar radiation, electromagnetohydrodynamics, gyrotactic microorganisms and activation energy. The non-dimensional problem is solved with the computational software Mathematica. The numerical solutions are presented in pictorial and tabular forms for velocity, nanoparticle temperature, nanoparticle concentration, motile microorganisms, Sherwood number, Nusselt number and skin friction. The current results have many applications in bio-medical and engineering fields, including in DNA analyzers, water filtration and purification processes, microchannel devices and electro-osmotic pumps.Consider the motion of a hybrid nanofluid (gold–silver–water) through an electromagnetohydrodynamic peristaltic channel under the effects of activation energy, solar radiation and gyrotactic microorganisms. The Cartesian coordinate system d C1 see . The repU and V are the velocity components, The equations  governing the flow of the hybrid nanofluid in the laboratory frame can be written as follows ,43,44:U=The thermophysical properties of water and hybrid nanofluids with various shapes are given by the following equations :(10)μhnfConsider the following transformations between the wave and fixed frame:We can introduce the non-dimensional variables as follows:The above-mentioned quantities are non-dimensional parameters and their nomenclature is given as follows: Using the non-dimensional quantities and transformations, and the assumptions of the lubrication approach, the governing equations can be converted as follows:The non-dimensional shear stress, Nusselt number and Sherwood number at the right wall can be represented as follows:Equations (17–20) with their corresponding boundary conditions ) are highly nonlinear and not amenable to find the exact solutions. For this reason, the system of equations was solved with the NDSolve command in Mathematica based on the shooting method. NDSolve is a widely used mathematical solver for the solution of ordinary differential equations and some partial differential equations. This technique can also handle some algebraic differential equations, which are a mix of algebraic and differential equations. NDSolve can solve both initial and boundary value problems iteratively. Nowadays, this technique is widely used by researchers ,49.This section deals with the numerical results of velocity, nanoparticle volume fraction, temperature, motile microorganisms, shear stress, Nusselt number and Sherwood number with sundry parameters of the Hartmann number (The velocity enhances with the Peclet number, thermophoresis parameter, electro-osmosis parameter and Grashof number near the right wall of the peristaltic channel.Stronger magnetic strengths reduce the velocity of the hybrid nanofluid.Stronger thermophoresis and Brownian motion effects lead to an increment in nanoparticle temperature.The radiation and Schmidt effects decrease the temperature profile.Nanoparticle concentration is enhanced with the radiation parameter and activation energy.The radiation and Brownian effects uplift the motile microorganism profiles.Shear stress increases with the enhancement of activation energy and radiation effects, and the trend is reversed for the thermophoresis and Schmidt parameters.The radiation and Brownian motion effects increase the motile microorganism profiles.The Sherwood number and Nusselt number are decreasing functions of the activation energy and Brownian motion effects, and the trend is reversed for the Schmidt number and fitted parameter.The current article dealt with the propulsion of a gold–silver–water hybrid nanofluid flow through a peristaltic microchannel under the effects of activation energy, radiation, Brownian motion, a magnetic field and an electric field. Initially, the nonlinear system of equations was simplified under the LWL and LRN approximations. The resulting highly nonlinear system was solved with the computational software Mathematica. Finally, the numerical results were provided for the Sherwood number, Nusselt number, shear stress, motile microorganisms, nanoparticle volume fraction, nanoparticle temperature and velocity with sundry parameters in pictorial and tabular forms. It should be noted from The findings of the present mathematical analysis will be a benchmark for simulating a more generalized model in three-dimensions for hybrid nanofluid flow with various geometries of nanoparticles in blood vessels, such as arteries and capillaries, for the better visualization and real applications of drug delivery in the circulatory system.


Magnetoencephalography for social science” we aimed at expanding this literature by editing four MEG studies that investigate various social processes: from morality, through the neural development of social-cognitive functioning and of face processing, to surprise. These studies, which are summarized below, relied on the uniqueness of MEG data to reveal complex neural dynamics underlying these social processes.The past two decades have seen the growth of the field of social and affective neuroscience. By using a range of neuroimaging tools, research in this field has progressed in uncovering the neural substrates and systems involved in social and affective processes (Cacioppo and Decety, Hiraishi et al. used MEG to distinguish between morally good and bad judgments. They addressed a gap in the literature on the neuroscience of morality that has mainly focused on brain areas using fMRI neuroimaging, while rarely examining the temporal and connectivity patterns related to moral processes. Using MEG, the study revealed differences at regional, temporal and functional connectivity levels.In one study, Sato et al. investigated a vulnerable population of children who were born with very low birth weight. They investigated their functional connectivity at rest and its associations with early nutrition and IQ and behavioural problems. The authors found that at preschool-age, these children show altered resting-state connectivity despite IQ and behaviour being in the average range, possibly reflecting functional reorganization of networks to support social-cognitive and behavioural functioning. The authors emphasized the importance of early postnatal nutrition in the development of resting-state networks that support social functions in childhood.Another study by Mousavi et al. analyzed MEG data in an oddball task to investigate the phenomenon of surprise from a detailed neurodynamic outlook. Although surprise has been examined in many studies, the authors set forth an information-theoretical model to describe and predict the surprise level of an external stimulus in MEG data. The results of their analyses found that middle temporal components and the right and left fronto-central regions offer the strongest power for decoding surprise. The authors concluded that this is a practical and rigorous method for evaluating the interactive and social effects of surprising events on the brain.A paper by Chen et al. studied face processing during the developmental period between 1 and 4 years. Despite this period being characterized by rapid changes in the ability to encode facial information, there are very few studies which investigate the neural processes of face encoding during this age, and this study sought to fill the gap between prior studies in infants and school-aged children. While implementing a longitudinal MEG approach across the first 4 years of life, they examined the maturation of the MEG responses in the fusiform gyri, which are primary nodes in the face-encoding network. The findings reported face-sensitive maturational changes, providing foundational data to the literature.Finally, Overall, although MEG studies on social processes are increasing, the contribution of this Research Topic has been to consolidate this budding literature and increase exposure to this growing field of research. We contend that this has the potential to motivate social neuroscientists to use MEG, on one hand, and on the other hand motivate MEG scientists to explore social processes. Our ambition is to support the use of this non-invasive method for exploring new horizons that would expand the understanding of social phenomena and their underlying neural mechanisms. Finally, we note that recent technological progress in wearable-MEG, optically-pumped magnetometers, dual-MEG and multiple-brain analyses will certainly yield novel ecologically-valid paradigms that would enhance MEG's ability to emulate real-life validity in the near future (Hari et al., JL wrote an initial draft for the editorial. All authors contributed to editorial revision, read, and approved the submitted version.


As this commentary is being written, the number of probable cases of acute hepatitis of unknown origin in children reported worldwide continues to rise, now exceeding 650. Thirty-three countries representing all continents have reported cases, with the UK accounting for the highest number with 222 . NotablyWhile efforts to thoroughly investigate and identify the cause(s) of this mysterious illness are ongoing, health alerts and guidelines for sample collection, testing, and reporting have been released across the globe by public health authorities. So far, no firm explanations for the contemporaneous occurrence of similar cases in geographically distant nations have been found.The topic was discussed in a late breaker session by co-author AEK on May 3 at the Clinical Virology Symposium, organized by the American Society for Microbiology, and since then several editorials, commentaries, and letters to editors have been contributed to various journals, and social media blogs, raising awareness ,3.Under the case definition released by the Centers for Disease Control and Prevention in the USA (CDC), “Children <10 years of age with elevated aspartate aminotransferase (AST) or alanine aminotransferase (ALT) (>500 U/L) who have an unknown aetiology for their hepatitis,” the number of persons under investigation in the United States alone now involves 38 states since 1 October 2021, and was collectively reported by the CDC to be 246 as of 1st June [The intriguing detection of adenovirus by qPCR in a considerable number of the cases investigated so far, and in particular of enteric type HAdV-F41  has attrBoth of the human species F adenoviruses, types 41 and 40, are causative agents of paediatric gastroenteritis  with typAlthough informative, the detection of concurrent viral infections is not sufficient to prove causality, and an expanded variety of clinical specimens needs to be collected from as many affected individuals as possible to add critical pieces to this difficult puzzle, in order to better investigate and understand the involvement of various organs and anatomical compartments.in situ hybridization, strongly suggests that adenovirus infection is not directly responsible for the observed liver pathology. As demonstrated for various other non-hepatotropic viruses, systemic infections may cause hepatic injury ranging from mild to severe acute hepatitis and occasionally acute liver failure [With COVID-19 mitigation practices in recent years, the prevalence of many respiratory and other infectious diseases decreased significantly. With the majority now returning to pre-pandemic levels we postulate that the recently observed hepatitis cases may be due to adenovirus, and likely other co-infections, triggering exacerbated inflammatory responses targeting a sensitized liver. The lack of detection of characteristic nuclear inclusion bodies, viral antigen by immunohistochemistry, or nucleic acid by  failure . The desA history of exposure to SARS-CoV-2 is a strong contender for a pre-existing condition and a common feature of paediatric populations around the world. While SARS-CoV-2 serology investigations in the reported paediatric hepatitis cases are still ongoing, very little is currently known about long COVID in children, especially regarding effects on liver function. However, evidence for the hepatic tropism of SARS-CoV-2 and molecular signature data from the characterization of associated liver injury provides strong incentive to pursue further study in this area . The recMultidisciplinary teams of investigators including immunologists, virologists, pathologists, and epidemiologists must be assembled to assist with the ongoing investigations to provide mechanistic insights on the pathogenesis of this intriguing illness.


The glia are the cells in the central nervous system (CNS) that originally were considered to only provide support, protection, and nutrition for neurons. The glia outnumber the neurons in the brain and spinal cord, the ratio of these two types of cells varies across species and tissues. The word "glia" comes from "glue", describing the cells that surround neurons and gathering them together like glue. However, in the past decades, studies gradually revealed the key roles of the glia and their heterogeneity in term of categorie and function.etc. Oligodendrocytes, the mature categories of oligodendrocyte lineage cells in CNS, form the membranous sheath covering axons and facilitate the neuronal electric signal transduction. The pathogenic mechanisms, regeneration and repair of the demyelination lesions have been extensively studied in neurological diseases. Microglia, the primary innate immune effector cells of the CNS, are distinctive from the other types of glia in their origins and functions.In CNS, astrocytes make up to 20% to 40% population of the glia, while oligodendrocytes 40% to 70%, and microglia 10% to 20%. Astrocytes are highly heterogeneous in morphology and function, dominantly participating in the biological processes such as the homeostatic regulation of neurotransmitters, water, ions and pH; the regulation of energy balance, food intake and metabolism; sleep homeostasis, development and synaptic plasticity, as well as local blood flow regulation, perivascular waste clearance, in vitro or ex vivo and in vivo studies. The discrepancies hinted that the interstitial microenvironment and the interactions with neurons are vital for the pathophysiological properties of the glia. In vivo multi-photon imaging can reveal the morphological and functional features of in situ glial cells with cellular resolution. Positron emission tomography (PET) can be used to visualize the metabolic processes of the glia noninvasively with cell-type oriented sensors; finally, the development of molecular manipulation techniques, such as, opto- and chemo-genetics, genetically encoded fluorescent sensors for calcium signaling, neurotransmitters, substantially opened a new era of understanding with regard to the molecular mechanisms in glial cells.The exploration of the mystery of the glia has been aided by the technical development targeting in this field, particularly the techniques characterizing the glial functions in live animals. Contradicting conclusions were reported between . Zheng et al reviewed the latest progress in spinal cord tissue repair by transplantation of human astrocytes of various origins, including fetal brain, spinal cord and pluripotent stem cells. Jia et al summarized the frontier progress in glial cell-type oriented tracers for PET imaging. Gong et al summarized the recent studies about the dysfunction of oligodendrocytes in amyotrophic lateral sclerosis. Li et al reviewed the immunologic role of oligodendrocyte lineage cells in demyelination diseases. Yan et al summarized mechanisms regulating cerebral hypoperfusion in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). Sun et al presented a visualization pipeline for in vivo two-photon volumetric astrocytic calcium imaging. Different from conventional two-dimensional imaging, they captured the three-dimensional cortical astrocytic Ca2+ time-lapse images through chronic craniectomy in brain state transitions from resting awake to isoflurane anesthetized states. Wang et al reported a clinical study of six patients of CADASIL and twelve healthy controls, they found that the severity of hypoperfusion correlates with the white matter hyperintensity volume. It highlighted the mutual links between the elements of the glio-vascular unit (G-unit). We hope the readers find this special issue interesting and intriguing.In this special issue, we have selected eight different articles that are presenting recent advances in the study of the glia and their effect on health and disease, particularly focusing on astrocytes and oligodendrocytes. Obara-Michlewska reviewed the contribution of astrocytes to obesity-associated metabolic disturbances, including the central regulation of appetite and energy metabolism


The COVID-19 pandemic has shown the need for neuropsychological care for olderadults with memory complaints in different contexts, including rural areas orareas with difficult access. This study aimed to analyze the clinical utility of the Phototest, throughtelemedicine, to identify mild cognitive impairment in rural older adultswith memory complaints, during the COVID-19 pandemic. We performed a cross-sectional, case-control, and clinical utilitycomparison of brief cognitive tests (BCTs). The sample included 111 ruralelderly people with mild cognitive impairment (MCI) and 130 healthy controlsfrom the Los Lagos region, Chile. The instruments adopted were modifiedMini-Mental State Examination (MMSEm) and adapted version of the Phototest(PT) for Chile. To identify mild cognitive impairment, using a cutoff score of 27-28 points,the Phototest showed a sensitivity of 96.6% and a specificity of 81.8%;indicators superior to those of the MMSEm. The Phototest is more accurate than the MMSEm in identifying cognitivealterations in rural older adults with cognitive memory complaints throughtelemedicine. Therefore, its use in primary care is recommended in order toperform early detection of preclinical cognitive alterations in mildcognitive impairment or neurodegenerative diseases. It was carried out during the second half of 2020, i.e., duringnational quarantine, due to the global pandemic of the COVID-19.,,The initial sample was composed of 354 rural seniors, aged 65 years or older, whoattended the annual checkup part of the Preventive Medicine Program for theOlder Adult (EMPAM for its acronym in Spanish). This is a national program ofthe Chilean Ministry of Health that is carried out in all primary care centersin the countryIn the context of this annual evaluation, 354 older adults were assessed at afamily health center (CESFAM) in a rural sector of the Los Lagos region(southern Chile). Of these, 181 reported having memory problems and 173 did notreport such problems. All patients were evaluated with the EFAM, together with aCDR clinical interview and medical assessment. The assessment was performedthrough the Zoom platform, except for the anthropometric measurements, the TUG,and the unipodal station test, which was performed in person at the ruraldoctor’s office, during the patient’s first visit.In the first group, with memory complaints, 111 participants were identified withMCI, but autonomous or functional, whereas, in the second group, without memorycomplaints, 130 participants were confirmed as autonomous or functional elderly,without cognitive problems. In both the groups, clinical and psychometriccriteria were applied to confirm the MCI group and the healthy control (HC)group. To identify the subjects as MCI and HC, first, the results of the EFAMfunctional tests were considered. In the case of the MCI group, the result of the functionalassessment should classify the patient as a self-sufficient or autonomous olderadult, according to the first part of the EFAM. Although individuals with verymild functional failure in instrumental activities of daily living wereincluded. Then, in the second part of the EFAM, the patient had to obtain CDscores on the abbreviated MMSE or MMSE-EFAM (≤13 points). In addition, the scoreon the CDR had to be 0.5. In contrast, HC had to be classified as self-valent orautonomous on the EFAM, obtaining high scores on the abbreviated MMSE (≥14points) and classified by the CDR as 0.0.After being evaluated with the EFAM, 113 subjects were excluded from the studyfor presenting functional problems, suspected dementia, depression, orvoluntarily withdrew from the study. But they were redirected to thepsychosocial care program. Finally, the presumptive diagnosis made by primarycare professionals was reviewed and validated by a neuropsychologist and anexpert neurologist. Subsequently, two groups were established, one consistingof older adults with MCI (MCI=111) and healthy controls (HC=130). Then, allpatients underwent a TNP assessment, where the modified MMSE (MMSEm)The PT ,The team of health center professionals was trained in virtual telehealthprograms and TNP procedures; in addition, they were trained by neurologists andneuropsychologists with expertise in cognitive pathology and detection of CD anddementia. They were trained in the use of clinical criteria, clinical interview(CDR), and cognitive instruments, including the MMSEm and PT. For the TNPassessment of subjects with MCI and HC, the modified Mini-MentalA descriptive analysis of the demographic characteristics and the results ofcognitive tests was performed on the groups analyzed. A comparison betweengroups was performed using Student’s t-test, and an analysis of the clinicalutility of the instruments was performed using ROC curves. Sensitivity (Sn) andspecificity (Sp) values were calculated along with the cutoff scores suggestedin the Chilean literature for the MMSEm The procedures performed in the present study complied with the ethical standardsof the pertinent national committees and institutions on human experimentationand the Declaration of Helsinki 1975, which was revised in 2008. Allparticipants were informed about the nature of the study and signed consent.This study was approved by the Institutional Ethics Committee of UniversidadSanto Tomás, in Chile (CEC UST Nº 15), and of Universidad de La Costa, inColombia (Act No. 092). The research is part of an international and multicenterstudy.The flow diagram of the participants is shown in A comparison between the PT and the MMSEm was performed among participants. ,,The MMSE is the gold-standard test for the detection of CD,,Moreover, the PT is a very brief test (<3 min) that can be used in primary healthcare and clinical contexts that have very limited time and large volumes of patientsseeking treatment,,,Recent studies have reported the superiority of the PT in identifying CD in generaland MCI in various health contextsAnother interesting result was related to the characteristics of the digital platformused and the effectiveness of remote neurocognitive assessment, to identify CD inthe participants of this study. Since the PT is not a pencil and paper task and doesnot require the subject to manipulate the test, its inclusion in the digitalplatform was easy. Also, the PT has several advantages over other available BCTs.The test (face-to-face or remote) starts with a naming task that includes a slidewith six images, which is shown to the patient. The developers of this instrumenthave created several slides to perform the assessment, thus reducing the learningeffect and diagnostic errors of the instrument (http://www.fototest.es/).Additionally, the application of the test is notably fast,,,,Therefore, despite the evidence supporting the assessment of dementia in vulnerablepopulations through telemedicine,,Therefore, since care should be provided to confined patients in rural areas ofChile, where access to medical care is limitedThis is pioneering research in LA, although it has some limitations. The authors ofthis study believe that follow-up studies are needed to gather evidence in favor ofthe PT using videoconferencing technologies for remote neuropsychologicalassessments. However, geographical and confinement limitations, in addition tolimited access to professionals with expertise in cognitive pathologies, highlightthe relevance of rapid TNP assessments. On the other hand, it would have beeninteresting to have compared the performance of this sample in urban populations.Unfortunately, this was not possible due to the sanitary measures of confinement. Itwas also not possible to analyze in depth the impact of quarantine or socialisolation on the mental health and cognition of the participants. During thefunctional assessment (EFAM), subjects who exhibited significant symptoms of moodalterations, or those whose symptoms were reported by their caregivers or relatives,were excluded from this study and referred to the psychosocial care program.Questions about the emotional situation of the elderly during confinement were notincluded in the TNP assessment.In addition, it was not possible to incorporate extensive neuropsychologicalassessments or to have complete cognitive profiles. Similarly, it was not possibleto specify the type of MCI, due to logistical problems, bandwidth, and thecomplexity of applying extensive neuropsychological assessments remotely throughthese virtual environments. Recent reports stress that such connection-relateddifficulties can affect processing speed tasks. The low resolution of the screenscan affect the discrimination of colors present in the tests. Finally, the qualityof the audio can lead to loss of information or interruptionThus, PT proved to be more accurate in identifying MCI in elderly people in ruralChile using TNP compared with the gold-standard measure. Its use is recommended inprimary health care contexts to detect preclinical cognitive alterations, such asMCI.