Structural Constraints Research Articles

Exo-Selective Diels-Alder Reactions.

The Diels-Alder reaction stands as one of the most pivotal transformations in organic chemistry. Its efficiency, marked by the formation of two carbon-carbon bonds and up to four new stereocenters in a single step, underscores its versatility and indispensability in synthesizing natural products and pharmaceuticals. The most significant stereoselectivity feature is the "endo rule". While this rule underpins the predictability of the stereochemical outcomes, it also underscores the challenges in achieving the opposite diastereoselectivity, making the exo-Diels-Alder reactions often considered outliers. This review delves into recent examples of exo-Diels-Alder reactions, shedding light on the factors inverting the intrinsic tendency. We explore the roles of steric, electrostatic, and orbital interactions, as well as thermodynamic equilibriums in influencing exo/endo selectivity. Furthermore, we illustrate strategies to manipulate these factors, employing approaches such as bulky substituents, s-cis conformations, transient structural constraints, and innovative control physics. Through these analyses, our aim is to provide a comprehensive understanding of how to predict and design exo-Diels-Alder reactions, paving the way for new diastereoselective catalyst systems and expanding the chemical scope of Diels-Alder reactions.

Construction of knowledge constraints: a case study of 3D structural modeling

The uncertainty of structural interpretation complicates the practical production and application of data-driven complex geological structure modeling technology. Intelligent structural modeling excavates and extracts structural knowledge from structural interpretation through human–machine collaboration and combines structural interpretation to form a new model of complex structural modeling guided by knowledge. Specifically, we focus on utilizing knowledge rule reasoning technology to extract topological semantic knowledge from interpretive data and employ knowledge inference to derive structural constraint information from complex geological structure models, thus effectively constraining the 3D geological structure modeling process. To achieve this, we develop a rule-based knowledge inference system that derives theoretical models consistent with expert cognition from interpretive data and prior knowledge. Additionally, we represent the extracted knowledge as a topological semantic knowledge graph, which facilitates computer recognition and allows estimation of intersection lines during 3D geological modeling, resulting in the creation of accurate models. The applicability of our proposed method to various complex geological structures is validated through application tests using real-world data. Furthermore, our method effectively supports the realization of intelligent structure modeling in real working area.

Listening to the Voices of Health Care Workers During the COVID-19 Pandemic: A Qualitative Study Providing In-Depth Insights Into Ethical and Individual Challenges.

In their daily practice, health care workers (HCWs) experience the effects of tensions between professional ethos and work realities, which can lead to ethical dilemmas. We aim to explore the ethical dilemmas that affected HCWs in Germany during the COVID-19 pandemic and to understand these in the context of the German health system. Between April and December 2022, we interviewed HCWs from various levels of care and key informants responsible for decisions related to HCWs in Germany. Three themes were identified in the data analyzed from 78 participants. The first highlighted the potency of pre-existing health system problems during the COVID-19 pandemic. The second captured the ethical dilemmas that were described as having arisen due to the tension between professional ethos and structural constraints. The third included factors related to increasing or diminishing the implications of ethical dilemmas. A lack of opportunities for HCWs to participate in political and managerial decisions was suggested to result in policies that do not meet the needs of HCWs and patients. Positive interpersonal interactions were described as helpful when coping with dilemmatic decision-making situations. In order to avoid negative consequences caused by unresolved ethical dilemmas, including moral distress, among HCWs, staff shortages and decision-making in the German health system urgently need to be addressed. HCWs' working conditions regularly evoke ethical dilemmas, particularly during public health emergencies. Together with HCWs, decision-makers must develop new models for working in health care settings that are in line with HCWs' professional ethos.

Vibration IOT Control Algorithm for Steel Structures of Concrete Buildings with Elastic Boundary Constraints

Abstract Because of the influence of steel structure’s elastic properties in concrete buildings, the traditional vibration Internet of Things (IOT) control algorithm of steel structures has the problem of low control efficiency. Based on the research subject of concrete buildings, a corresponding steel structure model is established, and the corresponding vibration control standard is determined according to the characteristics of the model. In this model, the boundary elastic constraints of the steel structure are set according to its structural characteristics, and the vibration characteristics of the steel structure are analyzed under the constraints. The external vibration signal is simulated, and the response of the building’s steel structure under different signal excitations is observed. According to the response characteristics of the steel structure, the vibration controller is designed and installed, the real-time vibration signal is input into the controller, and finally the vibration control of steel structure of concrete building is realized. By comparison with the traditional vibration IOT control algorithm, it is concluded that the vibration control method designed by combining vibration frequency and vibration amplitude has smaller error and shorter time cost, that is, the designed vibration IOT control algorithm has more advantages in control efficiency.

Probing RNA structural landscapes across Candida yeast genomes.

Understanding the intricate roles of RNA molecules in virulence and host-pathogen interactions can provide valuable insights into combatting infections and improving human health. Although much progress has been achieved in understanding transcriptional regulation during host-pathogen interactions in diverse species, more is needed to know about the structure of pathogen RNAs. This is particularly true for fungal pathogens, including pathogenic yeasts of the Candida genus, which are the leading cause of hospital-acquired fungal infections. Our work addresses the gap between RNA structure and their biology by employing genome-wide structure probing to comprehensively explore the structural landscape of mRNAs and long non-coding RNAs (lncRNAs) in the four major Candida pathogens. Specifically focusing on mRNA, we observe a robust correlation between sequence conservation and structural characteristics in orthologous transcripts, significantly when sequence identity exceeds 50%, highlighting structural feature conservation among closely related species. We investigate the impact of single nucleotide polymorphisms (SNPs) on mRNA secondary structure. SNPs within 5' untranslated regions (UTRs) tend to occur in less structured positions, suggesting structural constraints influencing transcript regulation. Furthermore, we compare the structural properties of coding regions and UTRs, noting that coding regions are generally more structured than UTRs, consistent with similar trends in other species. Additionally, we provide the first experimental characterization of lncRNA structures in Candida species. Most lncRNAs form independent subdomains, similar to human lncRNAs. Notably, we identify hairpin-like structures in lncRNAs, a feature known to be functionally significant. Comparing hairpin prevalence between lncRNAs and protein-coding genes, we find enrichment in lncRNAs across Candida species, humans, and Arabidopsis thaliana, suggesting a conserved role for these structures. In summary, our study offers valuable insights into the interplay between RNA sequence, structure, and function in Candida pathogens, with implications for gene expression regulation and potential therapeutic strategies against Candida infections.

Les pièces de théâtre de Matéi Visniec – Source d’inspiration pour des créations non conventionnelles


 
 
 The type of theatre proposed by the playwright Matei Vișniec offers great freedom to theatre creators and more. His plays can also be a starting point for light, sound, image installations. By its very nature, interdisciplinarity is born from the union of fragments from different fields, and Matei Vișniec’s dramaturgy is one that works as well in its entirety as it does fragmentally. Refusing structural constraints, as if, with each new play, he were intending to liberate it from the rules of writing, transgressing the usual boundaries of time and space and, of course, those of the psychology of the characters, Matei Vișniec’s theatre can be the seed for various types of artistic expression. They can just as well be the basis for psychological research since they are paradoxical snippets of life, so unusual and, at the same time, so repeatable. In the article, using some existing visual landmarks, we will trace and create in the imagination spaces proposed by the playwright in some of his plays, at the same time watching if and how the message of the text is reshaped. 
 
 

Empowering families traveling with young children: a transformative service research perspective

PurposeThis study aims to explore families that travel with children, as focuses on vulnerabilities, resource constraints and service exclusion through the lens of transformative service research (TSR). This paper investigates: how the experienced vulnerability of these families is shaped by structural, interpersonal and intrapersonal constraints, and how the constraints influence the family tourist-resource interaction in the air travel service encounter.Design/methodology/approachIn total, 2,855 reviews of the family tourists with children were analyzed with text mining, t-test and multidimensional scaling using the interpretive language R to answer the research questions with analyses on unstructured (e.g. text) and structured (e.g. consumer rating) data.FindingsThe findings of the empirical investigation answered how experienced vulnerability is shaped by structural, interpersonal and intrapersonal resource constraints and the types of family tourist-resource interaction in the travel service encounter to understand the resource constraints. The findings of this paper help examine family tourism experiences from a value formation perspective to unfold how stakeholders interact to form value while increasing and decreasing their well-being by the value of co-creation and co-destruction.Originality/valueThis research helps advance the TSR’s service inclusion framework by enabling opportunities, offering choice, relieving suffering and fostering happiness with empirical findings in travel service encounters. These findings are particularly insightful to family tourists with children struggling with unfair access and treatment in aeromobility service encounters, which may help enhance the well-being of individuals and communities.

Age-disparate and intergenerational sex partnerships and HIV: the role of gender norms among adolescent girls and young women in Malawi

BackgroundAge-mixing (age-disparate [5–9 years difference] and intergenerational [≥ 10 years difference]) partnerships are hypothesized drivers of HIV in adolescent girls and young women (AGYW; 15–24 years). These partnerships are often associated with increased gender inequities which undermine women’s agency and assertiveness. We assessed whether age-mixing partnerships were associated with HIV in Malawi and if endorsement of inequitable gender norms modifies this relationship.MethodsWe analyzed data from the Malawi Population-based HIV Impact Assessment, a nationally representative household survey conducted in 2015–2016. Participants underwent HIV testing and completed questionnaires related to actively endorsed gender norms and sexual risk behavior. We used multivariate logistic regression and multiplicative interaction to assess associations among AGYW who reported the age of their primary sex partner from the last year.ResultsThe analysis included 1,958 AGYW (mean age = 19.9 years, SD = 0.1), 459 (23.4%) and 131 (6.7%) of whom reported age-disparate and intergenerational partnerships, respectively. AGYW in age-mixing partnerships accounted for 13% of all AGYW and were older, more likely to reside in urban areas, to be married or cohabitating with a partner, and to have engaged in riskier sexual behavior compared with AGYW in age-concordant partnerships (p < 0.05). HIV prevalence among AGYW in age-disparate and intergenerational partnerships was 6.1% and 11.9%, respectively, compared with 3.2% in age-concordant partnerships (p < 0.001). After adjusting for residence, age, education, employment, wealth quintile, and ever been married or cohabitated as married, AGYW in age-disparate and intergenerational partnerships had 1.9 (95% CI: 1.1–3.5) and 3.4 (95% CI: 1.6–7.2) greater odds of HIV, respectively, compared with AGYW in age-concordant partnerships. Among the 614 (31% of the study group) who endorsed inequitable gender norms, AGYW in age-disparate and intergenerational partnerships had 3.5 (95% CI: 1.1–11.8) and 6.4 (95% CI: 1.5–27.8) greater odds of HIV, respectively, compared with AGYW in age-concordant partnerships.ConclusionsIn this Malawi general population survey, age-mixing partnerships were associated with increased odds of HIV among AGYW. These findings highlight inequitable gender norms as a potential focus for HIV prevention and could inform interventions targeting structural, cultural, and social constraints of this key group.

“Let’s Get a Little Bit Aboriginal, Shall We?”: Transforming Cultural Appropriation into Spiritual Wellness via the Neohealthism of KINRGY

Celebrity-driven wellness ventures are pervasive and often spearheaded by white women, resulting in white-centric health guidance. One such venture is KINRGY, a workout and lifestyle method created by professional dancer Julianne Hough that regularly appropriates and exploits Eastern, Aboriginal, and BIPOC cultural practices. Through a critical rhetorical interrogation of the workout videos and Instagram feed of KINRGY, we assess how this method relies on cultural appropriation and New Age Orientalism to situate spirituality as the crux of universal health, thus establishing a reconfiguration of healthism into what we call “neohealthism”—a phenomenon that further obfuscates structural constraints on health, and expands the individual imperatives of healthful choices by placing metaphysical considerations on consumers’ shoulders. We theorize neohealthism through the following themes: the consumption of the Other via cultural exploitation, the question of expertise in spiritual leadership, and the intensified neoliberal imperatives that individualize health and wellness for self and the universe.

Shifts at the margin of European welfare states: How important is food aid in complementing inadequate minimum incomes?

In recent decades, disappointing poverty trends and welfare state limitations in many European countries – including constraints on minimum income benefits – have paved the way for a larger role of the third sector. An interesting but controversial form of third-sector in-kind support is food aid provision. In Europe, food aid is, so far, a non-rights-based practice displaying worrisome discretionary and stigmatizing characteristics. Yet, the phenomenon of food aid in Europe has spread, professionalized, and penetrated the institutions of the welfare state. This raises the question if, how and to what extent food aid plays a role in bypassing structural constraints on minimum income protection. This article applies an exploratory case study approach to estimate the monetary value of food aid in relation to statutory minimum incomes in four EU-countries. We use cross-nationally comparable food reference budgets to price food aid packages in Belgium, Finland, Hungary and Spain. The results show that food aid, although not sufficient to close the at-risk-of-poverty gap, is non-trivial for some European households. In Spain and Belgium food aid packages can reach up to €100 a month (expressing 7% to 11% of respective minimum income benefit levels). Importantly, we perceive (formalized) cooperation and interaction between local welfare agencies and food charities in all countries, suggesting that welfare state actors use non-rights-based food aid for filling gaps in the social safety net. The large between- and within-country variation of the monetary values of food aid packages points, however, to food aid as a problematic discretionary practice.

Light Activation and Photophysics of a Structurally Constrained Nickel(II)-Bipyridine Aryl Halide Complex.

Transition-metal photoredox catalysis has transformed organic synthesis by harnessing light to construct complex molecules. Nickel(II)-bipyridine (bpy) aryl halide complexes are a significant class of cross-coupling catalysts that can be activated via direct light excitation. This study investigates the effects of molecular structure on the photophysics of these catalysts by considering an underexplored, structurally constrained Ni(II)-bpy aryl halide complex in which the aryl and bpy ligands are covalently tethered alongside traditional unconstrained complexes. Intriguingly, the tethered complex is photochemically stable but features a reversible Ni(II)-C(aryl) ⇄ [Ni(I)···C(aryl)•] equilibrium upon direct photoexcitation. When an electrophile is introduced during photoirradiation, we demonstrate a preference for photodissociation over recombination, rendering the parent Ni(II) complex a stable source of a reactive Ni(I) intermediate. Here, we characterize the reversible photochemical behavior of the tethered complex by kinetic analyses, quantum chemical calculations, and ultrafast transient absorption spectroscopy. Comparison to the previously characterized Ni(II)-bpy aryl halide complex indicates that the structural constraints considered here dramatically influence the excited state relaxation pathway and provide insight into the characteristics of excited-state Ni(II)-C bond homolysis and aryl radical reassociation dynamics. This study enriches the understanding of molecular structure effects in photoredox catalysis and offers new possibilities for designing customized photoactive catalysts for precise organic synthesis.

The Stress of Injustice: Public Defenders and the Frontline of American Inequality

Abstract Fairness in the criminal legal system is unattainable without effective legal representation of indigent defendants, yet we know little about the experience of attorneys who do this critical work. Using semi-structured interviews, our study investigated occupational stress in a sample of 78 attorneys representing indigent clients across the United States. We show how the chronic stressors experienced at work culminate in what we define as the stress of injustice: the social and psychological demands of working in a punitive system with laws and practices that target and punish those who are the most disadvantaged. Respondents positioned their professional stress around structural, not individual, aspects of the American criminal legal system, specifically punitive excess, underfunding of indigent defense, and the criminalization of mental illness and substance use. Working within these interrelated structural constraints makes public defenders highly vulnerable to stress and attrition.

Navigating travel constraints for individuals with mental health conditions

ABSTRACT While previous accessible travel studies focused primarily on physical disabilities, this research examined the perceptions and challenges related to travel experiences among individuals with mental health conditions. Grounded on the leisure constraint model, this study captured the distinct travel constraints and experiences shared by individuals with mental health conditions. Utilising the Reddit API, we collected data from several subreddits that cater to various mental health conditions, including autism, attention-deficit hyperactivity disorder, post-traumatic stress disorder, bipolar disorder, anxiety disorders, eating disorders, and depression. Through the application of topic modelling and topic network analysis, 30 themes and 7 communities emerged, spotlighting the pre- and during-travel constraints of individuals with mental health conditions. The resulting travel constraints were identified, leading to their categorisation as intrapersonal, interpersonal, and structural constraints. This categorisation lays the foundation for developing strategies that can enhance the travel experiences and engagements of individuals with mental health conditions.

Effectively answering why questions on structural graph clustering

The pSCAN algorithm is widely acknowledged for its efficiency in structural graph clustering across diverse graph applications, frequently utilized to detect significant clusters within graphs. The results of pSCAN are constrained by two parameters: (1) the structural similarity constraint ϵ; (2) the density constraint μ. Nevertheless, determining appropriate values for these parameters proves challenging as users often lack the requisite professional knowledge. Consequently, users may inquire about the inclusion of unexpected vertices in specified clusters, posing why questions. In this paper, we aim to address these inquiries by investigating the challenge of answering why questions on structural graph clustering. The objective is to refine the initialized clustering parameters to exclude unexpected vertices from specified clusters. Initially, we introduce the crucial concept of label-vertices and delve into a unified explanation framework designed for addressing why questions on structural graph clustering. Subsequently, we propose two effective refining algorithms, namely FReEPS and FReMU, specifically tailored to modify the similarity constraint ϵ and the density constraint μ independently. Moreover, in our approach to enhancing efficiency, we introduce two baseline explanation algorithms, ReParFirstMUand ReParFirstEPS, simultaneously refining the parameters ϵ and μ to exclude unexpected vertices from specified clusters. Additionally, we explore two improved algorithms, FReParFirstMUand FReParFirstEPS, incorporating a process of pruning unnecessary parameter combinations and computations. This enhancement aims to improve the efficiency of simultaneously refining the two parameters for addressing these questions. Finally, we conducted comprehensive experiments on real social network datasets. The results illustrate that the explanation efficiency of FReEPS and FReMU surpasses that of the state-of-the-art explanation algorithms by 1-2 orders of magnitude. Moreover, FReMu exhibits faster performance than FReEPS. Furthermore, simultaneous refinement of the parameters ϵ and μ yields better-refined parameters. Additionally, FReParFirstMU and FReParFirstEPS outperform ReParFirstMU and ReParFirstEPS, respectively.

Inequalities in privacy cynicism: An intersectional analysis of agency constraints

A growing body of research highlights a trend toward widespread attitudes of privacy cynicism, apathy and resignation among Internet users. In this work, we extend these discussions by concentrating on the concept of user agency. Specifically, we examine how five types of structural constraints—interpersonal, cultural, technological, economic and political—restrict user agency and contribute to the prevalence of privacy cynicism as a common response. Drawing on critical data studies and adopting an intersectional lens, we demonstrate how these constraints disproportionately impact various social groups unequally, leading to a disparate distribution of agency and privacy cynicism. Furthermore, we contend that the sense of powerlessness engendered by excessive constraints on user agency can, in turn, exacerbate user vulnerability to such constraints, potentially initiating a vicious cycle of disempowerment. The article enriches the field of privacy research by linking the traditionally individual-focused and psychological dimensions of privacy with critical surveillance studies and by proposing potential interventions to mitigate privacy cynicism.

Adaptive robust constraint-following control for morphing quadrotor UAV with uncertainty: A segmented modeling approach

During morphing, changes in a quadrotor UAV’s center of gravity and inertia contribute to unstable flight. Various uncertainties also impact its performance. In modeling, considering inertia and length variations due to morphing increases complexity. In control, detailed knowledge of uncertainties, such as parameter variability, is often needed. We propose a segmented modeling approach to obtain the quadrotor UAV model under morphing condition, along with an adaptive robust control to handle uncertainties within the system. The quadrotor UAV is innovatively segmented into three subsystems. Using the Udwadia–Kalaba (U–K) equation’s cascading and clustering features, we transform desired trajectories into constraints and integrate them with structural morphing constraints. This provides a direct analytical solution for constraint forces, which is immediately applicable to subsequent control design. This control consists of a nominal control part and an adaptive robust control part. Additionally, we only require that the uncertainty is bounded. The designed adaptation law is leaky, and adaptive parameters are adjusted based on the system’s performance to compensate for uncertainties within the system. The efficacy of the proposed modeling and control approaches is validated through simulation results.

Irrational or Rational? Time to Rethink Our Understanding of Financially Responsible Behavior

Models of finance rationality expect individuals to actively prepare for retirement by consistently investing and building a diversified asset portfolio, with any behavior deviating from these expectations being identified as irresponsible. This framework of (ir)rationality and (ir)responsibility ignores the role of constraints in shaping financial behavior. Extending economic geographic insights on everyday financial practices as complex processes of meaning-making, we reveal how varied approaches to retirement savings are shaped by the experience of constraints inherent in a capitalist welfare state. Using the accounts of forty-two interviewed women and people with a minority ethnic background in the UK, we show how the interplay between everyday rationalities and structural constraints construct variegated financial subjectivities and practices that reflect the context that individuals face. Our findings contribute to the theorization of variegated financial subjects and disrupt the application of corrective policy measures, such as financial education, which put more pressure on individuals rather than tackling the inequalities inherent in the capitalist welfare state broadly and in the pension system specifically.

Why traditional firms from the same industry reject digital transformation: Structural constraints of perception and attention

We explain why some traditional companies fail to sense new digital technologies when facing an identical scenario of digital transformation. Our objective is to investigate situations where discontinuous changes steaming from digital transformation are actively rejected, in the sense that they are not perceived as a strategic issue, i.e., a threat or opportunity. We draw on a mixed-method research design comprising two sequential studies. The first study is based on Delphi's Technique, which uses a panel of specialists to build the most likely future scenarios in the medium term for the language education industry. The second one is a qualitative comparative study with eleven traditional firms. Their senior executives were first asked for their spontaneous sensing of emerging technologies and later asked to provide their assessment of the most likely future scenarios. Our contribution lies in developing a conceptual model that proposes a structural “schema-driven” explanation of why firm-level structures – concrete, contextual and knowledge – can hinder perception and attention. Active rejection is prompted not by the absence of attentional structures, but by their specific attributes. This expands the dominant ontology of issues, asserting their existence independently of an organization's epistemological experience, and adds to the theoretical understanding regarding the constraints of the sensing dynamic capability in digital transformation.

A unified model for cross-modal plasticity and skill acquisition.

Historically, cross-modal plasticity following early blindness has been largely studied in the context of visual deprivation. However, more recently, there has been a shift in focus towards understanding cross-modal plasticity from the perspective of skill acquisition: the striking plasticity observed in early blind individuals reflects the extraordinary perceptual and cognitive challenges they solve. Here, inspired by two seminal papers on skill learning (the "cortical recycling" theory) and cross-modal plasticity (the "metamodal" hypothesis) respectively, we present a unified hypothesis of cortical specialization that describes how shared functional, algorithmic, and structural constraints might mediate both types of plasticity.

What ASEAN Must Learn from Timor-Leste: A Tripartite Analysis on Australian Foreign Policy Related to Timor Sea Treaty 2018

The Timor Gap had been a hotspot of territorial dispute between Australia and Timor-Leste. In 2018, Australia finally agreed to settle a permanent maritime boundary in favour of Timor-Leste. Why was Australia willing to sacrifice the border and give a favourable outcome to Timor-Leste? The research examined the importance of the tripartite approach to Foreign Policy analysis to understand why a country may choose seemingly unfavourable options in territorial disputes. The analysis showed how Australian foreign policy was influenced by agency-structure interactions within the international system. The research demonstrated that structural constraints at the international level influenced Australia’s decision, including the South China Sea dispute between ASEAN members and China, previous agreements Australia-Timor-Leste on the management of the Timor Gap, and domestic political dynamics in Australia. The research reveals a relationship between actors’ structural and dispositional dimensions in foreign policy. In the case of Australia, there is a strong link between democratic values ​​and respect for the international rules-based order. Altogether, this situation prompted Australia to continue negotiations with Timor-Leste over the Timor Gap and ultimately to accept an agreement for maritime delimitation in Timor-Leste’s favor.