The concept of metamaterial recently emerged as a new frontier of scientific research, encompassing physics, materials science and engineering. In a broad sense, a metamaterial indicates an engineered material with exotic properties not found in nature, obtained by appropriate architecture either at macro-scale or at micro-/nano-scales. The architecture of metamaterials can be tailored to open unforeseen opportunities for mechanical and acoustic applications, as demonstrated by an impressive and increasing number of studies. Building on this knowledge, this theme issue aims to gather cutting-edge theoretical, computational and experimental studies on elastic and acoustic metamaterials, with the purpose of offering a wide perspective on recent achievements and future challenges. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'.

ABSTRACT Since it establishes differentiated socio-legal eligibility categories among different migrant groups, family reunification constitutes a prime example of the internal border. In my article, I investigate how the border is produced and negotiated in the context of family reunification of refugee children and parents by focusing on discretionary practices of German immigration bureaucracy through the lens of counselling actors in the city. Taking the city of Frankfurt am Main as my research site, I identify ignorance, verification, and temporalization as three administrative control mechanisms over descent-based refugee families. I argue that family reunification constitutes a highly selective and culturalized field of border control, in which refugee families are filtered according to their conformity to a certain family norm and European bureaucratic standards. By examining how counselling actors understand administrative practice, I also discuss how they respond to it, including their own participation in de- and (re-)bordering.

ABSTRACT Registration promotes emancipation: by acquiring a legal individual identity, a person becomes a formal member of a community and obtains rights. However, registration also enables and reproduces hierarchies and subordinate inclusion, especially when it becomes a selective device. This article aims to highlight the ambiguous status of registration by focusing on municipal registration, a device that is analysed from a historical-theoretical perspective and by highlighting the case of European citizens. The aim is to show that municipal registration is part of a local border regime, as it promotes the internalisation of borders. By proposing a theoretical reflection and drawing on research already carried out on municipal registration, the article aims to reveal the ambiguities of registration as an internal border: in particular, how recognition, or conversely the lack of it, is used to exclude or “omit” people, thus preventing them from being fully autonomous in a legal and material sense.

BACKGROUND Autism spectrum disorder (ASD) is a complex neurodevelopmental condition characterized by heterogeneous symptoms and genetic underpinnings. Recent advancements in genetic and epigenetic research have provided insights into the intricate mechanisms contributing to ASD, influencing both diagnosis and therapeutic strategies. AIM To explore the genetic architecture of ASD, elucidate mechanistic insights into genetic mutations, and examine gene-environment interactions. METHODS A comprehensive systematic review was conducted, integrating findings from studies on genetic variations, epigenetic mechanisms (such as DNA methylation and histone modifications), and emerging technologies [including Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Cas9 and single-cell RNA sequencing]. Relevant articles were identified through systematic searches of databases such as PubMed and Google Scholar. RESULTS Genetic studies have identified numerous risk genes and mutations associated with ASD, yet many cases remain unexplained by known factors, suggesting undiscovered genetic components. Mechanistic insights into how these genetic mutations impact neural development and brain connectivity are still evolving. Epigenetic modifications, particularly DNA methylation and non-coding RNAs, also play significant roles in ASD pathogenesis. Emerging technologies like CRISPR-Cas9 and advanced bioinformatics are advancing our understanding by enabling precise genetic editing and analysis of complex genomic data. CONCLUSION Continued research into the genetic and epigenetic underpinnings of ASD is crucial for developing personalized and effective treatments. Collaborative efforts integrating multidisciplinary expertise and international collaborations are essential to address the complexity of ASD and translate genetic discoveries into clinical practice. Addressing unresolved questions and ethical considerations surrounding genetic research will pave the way for improved diagnostic tools and targeted therapies, ultimately enhancing outcomes for individuals affected by ASD.

BACKGROUND Mental illness is a health challenge faced by adolescents that has grown worse after the Coronavirus disease 2019 pandemic. Research on social media and young people’s mental health has recently increased, and numerous studies have examined whether frequent use of social media is linked to issues such as anxiety, stress, depression, eating disorders, insomnia, frustration, feeling alone, and externalizing problems among adolescents. This influence of social media on adolescents’ lives is clear, with many platforms like Facebook, Instagram, and YouTube playing an important role in daily interactions and self-expression. Even though social media offers numerous benefits, such as connectivity and information sharing, excessive usage can have detrimental effects on mental health, particularly among adolescents. AIM To study the impact of social media on the mental wellbeing of adolescents, and the associated potential dangers in India. METHODS A total of 204 adolescents aged 14 years to 23 years were included in the study. This study explored the intricate relationship between social media usage and adolescent mental health in India. The study employs a cross-sectional survey design to capture a snapshot of adolescent mental health and social media usage patterns. Data collection involved administering structured questionnaires and the analysis utilized quantitative methods, including descriptive statistics. RESULTS Excessive use of social media is correlated with increased stress, anxiety, and depression. Adolescents engage in compulsive behaviors such as scrolling in the middle of the night, which negatively impacts their mental and physical health, and leads to significant sleep disruption. Findings from the study aim to provide insights into the current state of adolescent mental health and inform strategies to promote positive wellbeing in the Indian population. CONCLUSION The study underscores the need for further research to better understand the complex interplay between social media and adolescent mental health, and need for effective strategies to combat online harassment.

The aim of this research is to find out how the eTwinning project prepared to prevent bread waste is evaluated from the students' perspective. The research was conducted within the scope of qualitative research. The research was carried out with 6th grade students consisting of six people who voluntarily participated in the eTwinning project. In line with the main purpose of the research, semi-structured interviews were conducted with the students at the end of the project and data were collected. The data obtained were subjected to content analysis, and codes and themes were created. At the end of the research, it was revealed that the students found the ŞEBİT eTwinning project educational, instructive and entertaining. In addition, it was determined that the project contributed to awareness of bread waste, learning web 2.0 tools, taking responsibility, teamwork and communication. In addition, it was determined that students had difficulties in using web 2.0 tools and time within the scope of the project. In line with the students' opinions, it is suggested that the eTwinning platform should be made more functional for both teachers and students within the scope of this research.

This study aims to examine the experiences of pre-service elementary mathematics teachers regarding the school experience course conducted through distance education due to the Covid-19 pandemic. The study was conducted with 64 volunteer participants, from students who took the School Experience course in the fall semester of the 2021-2022 academic year at a state university, which was determined by convenience sampling among the universities in Turkey. The data was gathered using Google form at the end of the fall semester, using a data collection tool including 4 open-ended questions. These questions were about general evaluation, contributions, faced problems, and suggestions about the school experience course process. The study is phenomenological research from qualitative research types, and the content analysis method was used to analyze the data. Based on the analysis of the collected data, the following codes were obtained: positive, neutral, and negative under the heading of general evaluation; no contribution, getting to know students, professional skills, and time under the heading of contributions; technological problems, lack of professional skills, professional satisfaction, and communication under the heading of faced problems; and active participation, changing the course content, educational support, face-to-face education, student participation, and technological support under the heading of suggestions.

Science, technology, engineering, and mathematics (STEM) subjects are a significant concern in educational systems worldwide. Students who learn these subjects acquire skills and knowledge that enable countries to develop advanced technological infrastructures in industry and academia, ultimately driving local and global economies toward a more advanced future. However, many countries have reported reduced student interest in STEM studies. While students become interested in STEM subjects after joining space education projects, these are often informal activities that occur outside schools. Space education allows students to explore several subjects simultaneously through a multidisciplinary approach and facilitates the development of important skills required in the knowledge-intensive industry and academia. Hence, this research aimed to analyze the perceptions and attitudes of high school graduates exposed to school-based space studies within the formal educational framework in relation to their motivation to undergo STEM studies and other pedagogical issues. The results reveal students’ high degree of motivation to undergo STEM studies through space education, which is an expected but not obvious finding. As for the pedagogical aspect, the issues highlighted by space education include learning activities outside the classroom, the acquisition of skills, and the use of the project-based learning (PBL) approach.

Technology has revolutionised everyday existence. Information and Communication Technology (ICT) is essential to society, employment, and education. Improved microelectronics has facilitated the proliferation of inexpensive portable devices such as smartphones. This study, therefore, investigated whether senior secondary school students' nomophobia and smartphone addiction are linked to math anxiety. Two research hypotheses were tested and the study was guided by social cognitive theory. This study employed a descriptive survey research methodology and primary data were collected from 397 students in Ikorodu, Lagos, Nigeria with the use of the Nomophobia Questionnaire (NMP-Q, α=0.89), the Smartphone Addiction Scale Short Version (SAS-SV, α=0.82), and the Mathematics Anxiety Scale (MAS, α=0.81) developed by Yildirim and Correia (2015), Kwon et al. (2013), and Ablian and Parangat (2022) respectively. The data gathered were subjected to analysis using frequency counts, Pearson correlation, and regression analysis at 0.05 significance level. This analysis was conducted using SPSS software, specifically version 23.0. The research revealed a significant association between nomophobia and smartphone addiction among the students. Additionally, the severity of nomophobia and smartphone addiction emerged as significant predictors of mathematics anxiety among high schools in Lagos. Consequently, this investigation proposes that educational authorities in Lagos State should consider implementing a ban on mobile phone usage within secondary schools as a means to mitigate these behavioural addictions among adolescents. Additionally, stakeholders within the education sector, including parents, can contribute to the prevention of these addictions by advising students about the perils of smartphone addiction, fostering ethical social interactions that cultivate trust in the family unit, and imposing restrictions on their children's smartphone usage and associated expenses.

The factors related to estimating skills are twofold: cognitive and affective perspectives. Perception of self-efficacy in mathematics, one of the affective factors, is essential for the individual's capacity, abilities, and self-belief in mathematics for the mathematics course. The present study examined the relationship between students' computational estimation skills and mathematical self-efficacy perceptions. For this purpose, two sets of instruments were used as data collection tools: a computational estimation skills task and a mathematical self-efficacy perceptions scale. A correlational design was used in this study, and a total of 83 eighth-grade students participated in the research. As a result, it was concluded that there was a moderately positive and statistically significant relationship between computational estimation skills and mathematical self-efficacy perceptions. Students experience more stress when making estimations compared to mathematical computations whose results are specific. In addition, students mostly need to correct their estimations in questions related to computations with fractions, and they mostly use the rounding strategy when making estimations. These results are further discussed in relation to the perspective of supporting children’s abilities for estimations at the primary school.