Tuning (Anti)Aromaticity: Variations on the [8]-Circulene Framework.

Optoelectronic properties of organic molecules are underpinned by delocalisation and delocalisability of π-electrons. These properties are sensitive to small changes in electron count, whether achieved by heteroatom substitution or redox chemistry. One measure of the delocalisability of π-electrons is the current induced by an external magnetic field, which is diagnostic of (anti)aromaticity. The ab initio ipsocentric method is used here to model diverse ring-current patterns in the family of [8]-circulenes based on tetracyclopenta[def,jkl,pqr,vwx]tetraphenylene (TCPTP), in different charge states, with disjoint hetero-atom substitution, and with CC units systematically replaced by BN pairs. Maps calculated at the CHF/CTOCD-DZ2/6-31G** level reveal that these modifications of the TCPTP framework access the full range of possibilities for current from concentric global circulations (typically counter rotating) to full (non-aromatic) localisation. In the ipsocentric approach, induced current density is partitioned into robust orbital contributions that obey selection rules based on orbital symmetry, energy and nodal character. The selection rules are applied here to interpret current-density and exploit insights gained from simpler models to suggest design strategies for fine-tuning of π-delocalisability (aromaticity and antiaromaticity) in macrocyclic frameworks.

Community- and data-driven homelessness prevention and service delivery: optimizing for equity.

OBJECTIVE: The study tests a community- and data-driven approach to homelessness prevention. Federal policies call for efficient and equitable local responses to homelessness. However, the overwhelming demand for limited homeless assistance is challenging without empirically supported decision-making tools and raises questions of whom to serve with scarce resources. MATERIALS AND METHODS: System-wide administrative records capture the delivery of an array of homeless services (prevention, shelter, short-term housing, supportive housing) and whether households reenter the system within 2 years. Counterfactual machine learning identifies which service most likely prevents reentry for each household. Based on community input, predictions are aggregated for subpopulations of interest (race/ethnicity, gender, families, youth, and health conditions) to generate transparent prioritization rules for whom to serve first. Simulations of households entering the system during the study period evaluate whether reallocating services based on prioritization rules compared with services-as-usual. RESULTS: Homelessness prevention benefited households who could access it, while differential effects exist for homeless households that partially align with community interests. Households with comorbid health conditions avoid homelessness most when provided longer-term supportive housing, and families with children fare best in short-term rentals. No additional differential effects existed for intersectional subgroups. Prioritization rules reduce community-wide homelessness in simulations. Moreover, prioritization mitigated observed reentry disparities for female and unaccompanied youth without excluding Black and families with children. DISCUSSION: Leveraging administrative records with machine learning supplements local decision-making and enables ongoing evaluation of data- and equity-driven homeless services. CONCLUSIONS: Community- and data-driven prioritization rules more equitably target scarce homeless resources.

Scaling-up Child and Youth Mental Health Services: Assessing Coverage of a County-Wide Prevention and Early Intervention Initiative During One Fiscal Year.

PURPOSE: In the U.S., the percentage of youth in need of evidence-based mental health practices (EBPs) who receive them (i.e., coverage rate) is low. We know little about what influences coverage rates. In 2010, the Los Angeles County Department of Mental Health (LACDMH) launched a reimbursement-driven implementation of multiple EBPs in youth mental health care. This study examines two questions: (1) What was the coverage rate of EBPs delivered three years following initial implementation? (2) What factors are associated with the coverage rates? METHODS: To assess coverage rates of publicly insured youth, we used LACDMH administrative claims data from July 1, 2013 to June 30, 2014 and estimates of the size of the targeted eligible youth population from the 2014 American Community Survey (ACS). The unit of analysis was clinic service areas (n = 254). We used Geographic Information Systems and an OLS regression to assess community and clinic characteristics related to coverage. RESULTS: The county coverage rate was estimated at 17%, much higher than national estimates. The proportion of ethnic minorities, individuals who are foreign-born, adults with a college degree within a geographic area were negatively associated with clinic service area coverage rates. Having more therapists who speak a language other than English, providing care outside of clinics, and higher proportion of households without a car were associated with higher coverage rates. CONCLUSION: Heterogeneity in municipal mental health record type and availability makes it difficult to compare the LACDMH coverage rate with other efforts. However, the LACDMH initiative has higher coverage than published national rates. Having bilingual therapists and providing services outside the clinic was associated with higher coverage. Even with higher coverage, inequities persisted.

Meeting housing needs of child welfare-involved families: Policy insights from simulation modeling.

BACKGROUND: Inadequate housing contributes to the risk of family separation in nearly one-quarter of child maltreatment investigations. Child welfare struggles to identify and address the demand for housing assistance. A range of housing interventions shows promise for stabilizing families. Still, aid remains difficult to access, and little evidence exists for prioritizing households to interventions. Inefficient decisions about who to serve with scarce housing resources threaten to diminish resources and unintentionally place children at greater risk. OBJECTIVE: The present study leverages computational modeling to simulate the complex dynamics of coordinated child welfare response to inadequate housing. Simulations address the lack of microdata on current service delivery to inform policy-making that protects children from family insecurity. PARTICIPANTS AND SETTINGS: A series of simulated policy experiments test strategies for maximizing access to appropriate housing assistance and minimizing system-wide family separations using US estimates of housing insecurity and child welfare involvement. Models incorporate the feedback loops involved in seeking and waiting for needed services, using information on national rates of housing insecurity among child welfare-involved families. RESULTS: Results demonstrate population-level improvements in family stability from enhanced targeting of housing assistance to families most likely to benefit, plus expanded access to housing interventions. Neither improved screening procedures nor more housing supports alone improve child welfare outcomes. CONCLUSIONS: Findings emphasize the importance of data-driven upstream policies for protecting inadequately housed children at risk of maltreatment.

The impact of responsible fatherhood programs on parenting, psychological well-being, and financial outcomes: A randomized controlled trial.

The objective of this study was to examine differences in parenting, psychological well-being, and economic outcomes between fathers receiving two different programs offered by Fathers & Families Support Center for economically disadvantaged fathers: (a) Family Formation (FF), a 6-week/240-h program focused on economic stability/mobility, responsible fatherhood, and healthy relationships, with case management and legal services; (b) Economic Stability (ES), a 4-week/80-h program focused only on economic stability with limited case management and legal services. A randomized controlled trial (RCT) was used to compare fathers in FF (n = 350) vs. ES (n = 342). Surveys were administered at enrollment and 3- and 12-months postintervention. Linear and generalized linear mixed models were used to assess changes in program outcomes over time and across study groups. Four hundred and eighty-two fathers responded to either follow-up survey (251 FF, 231 ES). Nearly all (98%) were non-white (93% Black, 5% other/mixed race) and were on average 34 years old. Approximately 46% attended ≥75% of program sessions (FF 48% vs. ES 44%). Both FF and ES groups experienced improvements in parenting, psychological well-being, and financial outcomes after the programs, but changes in outcomes over time did not differ significantly by program. The lack of difference in outcomes between fathers in FF and ES groups could be due to a similar core focus on employment-related curriculum for both groups. Gaining financial stability could have contributed to positive improvements in other fatherhood domains. Implications for future research and practice are discussed herein.

El objetivo de este estudio fue analizar las diferencias en la crianza, el bienestar psicológico y los resultados económicos entre padres que recibían dos programas diferentes ofrecidos por el Centro de Apoyo a los Padres y las Familias (Fathers & Familiares Support Center) para padres desfavorecidos económicamente: (a) Formación de una Familia (Family Formation, FF), un programa de 6 semanas/240 horas centrado en la estabilidad/movilidad económica, la paternidad responsable y las relaciones saludables, con gestión de casos y servicios legales; (b) Estabilidad Económica (Economic Stability, ES), un programa de 4 semanas/80 horas centrado solamente en la estabilidad económica con poca gestión de casos y servicios legales. Se usó un ensayo controlado aleatorizado para comparar a los padres de FF (n=350) con los de ES (n=342). Se realizaron encuestas en la inscripción y a los 3 y a los 12 meses posteriores a la intervención. Se usaron modelos lineales y modelos mixtos lineales generalizados para evaluar los cambios en los resultados de los programas con el tiempo y entre los grupos de estudio. 482 padres respondieron a cada encuesta de seguimiento (251 FF, 231 ES). Casi todos (el 98 %) eran de color (el 93 % negros, el 5 % de otra raza o de raza mestiza) y tenían, en promedio, 34 años. Aproximadamente el 46 % asistió a más del 75 % de las sesiones de los programas (el 48 % de FF frente al 44 % de ES). Tanto el grupo de FF como el de ES tuvieron mejoras en la crianza, en el bienestar psicológico y en los resultados económicos después de los programas, pero los cambios en los resultados con el tiempo no variaron significativamente por programa. La falta de diferencia en los resultados entre los padres del grupo de FF y los del grupo de ES podría deberse a un enfoque principal similar en un currículo relacionado con el empleo para ambos grupos. La adquisición de estabilidad económica podría haber contribuido a mejoras positivas en otras áreas de la paternidad. Se comentan las consecuencias para la futura investigación y la práctica.

Periodoannulenes: A Generalized Annulene-within-an-Annulene Paradigm for Combined σ and π Ring Currents.

Periodoannulene molecules and ions CxIxq in planar geometry offer examples of systems with the potential for outer σ and inner π ring-current double aromaticity, given a sufficient overlap of tangential pσ-orbital manifolds on the large atoms of the outer cycle. Previous theoretical work indicated concentric diatropic currents in the dication C6I62+. Ab initio ipsocentric calculations support an account in terms of frontier-orbital selection rules for current contributions in C6I62+ (and radical C6I6+, implicated in recent experimental work on the oxidation of periodobenzene). A σ/π analogue of the annulene-within-an-annulene model is applied here to periodo systems based on cyclooctatetraene. Model species C8I8q with charges q = 0, +1, +2, +4, -2 and structures constrained to a planar D4h symmetry exhibit maps with all combinations of σ/π con- and counter-rotation, comprising global σ ring currents on the iodine perimeter and central π ring currents on the carbocycle. All can be rationalized by the separate application of the tropicity selection rules to the two subsystems, whether in singlet or triplet states.

Understanding Mechanisms Driving Family Homeless Shelter Use and Child Mental Health.

Homeless shelters throughout the U.S. are overcrowded and under-resourced. Families with children face substantial barriers to timely, successful shelter exit, and prolonged shelter stays threaten child mental health. This community-based system dynamics study explored barriers to timely, successful shelter exit and feedback mechanisms driving length of stay and child mental health risk. Group model building - a participatory systems science tool - and key informant interviews were conducted with clients (N = 37) and staff (N = 6) in three family homeless shelters in a Midwestern region. Qualitative content analysis with emergent coding identified key themes feedback loops. Findings indicated overcrowding delayed successful shelter exit; longer stays exacerbated crowding and stress in a vicious cycle. Furthermore, longer stays exacerbated child risk for mental disorder both directly and indirectly via crowding and caregiver stress. Capacity constraints limited families served, while contributing to ongoing unmet need. Future research should investigate the roles of these dynamic feedback relationships in the persistent vulnerability of homeless families. Service design should prioritize interventions that alleviate crowding and subsequent threats to mental health such as private or scattered-site shelter accommodations, affordable child care, and homelessness prevention to facilitate successful shelter exit and mitigate child mental health risk.

A Correlated Source-Sink-Potential Model Consistent with the Meir-Wingreen Formula.

We model a molecular device as a molecule attached to a set of leads treated at the tight-binding level, with the central molecule described to any desired level of electronic structure theory. Within this model, in the absence of electron-phonon interactions, the Landauer-Büttiker part of the Meir-Wingreen formula is shown to be sufficient to describe the transmission factor of the correlated device. The key to this demonstration is to ensure that the correlation self-energy has the same functional form as the exact correlation self-energy. This form implies that nonsymmetric contributions to the Meir-Wingreen formula vanish, and hence, conservation of current is achieved without the need for Green's Function self-consistency. An extension of the Source-Sink-Potential (SSP) approach gives a computational route to the calculation and interpretation of electron transmission in correlated systems. In this picture, current passes through internal molecular channels via resonance states with complex-valued energies. Each resonance state arises from one of the states in the Lehmann expansion of the one-electron Green's function, hole conduction derived from ionized states, and particle conduction from attached states. In the correlated device, the dependence of transmission on electron energy is determined by four structural polynomials, as it was in the tight-binding (Hückel) version of the SSP method. Hence, there are active and inert conduction channels (in the correlated case, linked to Dyson orbitals) governed by a set of selection rules that map smoothly onto the simplest picture.

Modelling aromatisation of (BN)nH2n azabora-annulenes.

Despite a long tradition of descriptions of borazine as an 'inorganic benzene', this molecule is a non-aromatic species according to the magnetic (ring-current) criterion. Borazine, borazocine, and the larger neutral (BN)nH2n azabora-annulene heterocycles in planar conformations, although π-isoelectronic with [2n]annulenes, support only localized induced currents in perpendicular magnetic fields. The π-current maps of these systems comprise superpositions of separate 'lone-pair' circulations on all nitrogen centres. For the systems with n > 4, planarity must be enforced by a constraint. Qualitative orbital analysis based on the ipsocentric approach to calculation of induced current density suggests that global induced currents could be produced through strategic changes to the π electron count. In ab initio calculations, azabora-annulenes with rings of size [8]- and larger were indeed found to support global diatropic ring currents in both anionic and cationic forms with (4N + 2) π electron counts. The planar conformation of the charged ring typically occupies a stationary point of higher order on the potential energy surface, rather than a minimum. However, the borazocine dianion, [B4N4H8]2-, occupies a planar minimum, supports a diatropic ring current of strength comparable to that in benzene, and is predicted to participate in sandwich compounds; it is therefore a good candidate for an aromatised azabora-annulene.

Ring-Current Maps for Benzenoids: Comparisons, Contradictions, and a Versatile Combinatorial Model.

As a key diagnostic property of benzenoids and other polycyclic hydrocarbons, induced ring current has inspired diverse approaches for calculation, modeling, and interpretation. Grid-based methods include the ipsocentric ab initio calculation of current maps, and its surrogate, the pseudo-π model. Graph-based models include a family of conjugated-circuit (CC) models and the molecular-orbital Hückel-London (HL) model. To assess competing claims for physical relevance of derived current maps for benzenoids, a protocol for graph-reduction and comparison was devised. Graph reduction of pseudo-π grid maps highlights their overall similarity to HL maps, but also reveals systematic differences. These are ascribed to unavoidable pseudo-π proximity limitations for benzenoids with short nonbonded distances, and to poor continuity of pseudo-π current for classes of benzenoids with fixed bonds, where single-reference methods can be unreliable. Comparison between graph-based approaches shows that the published CC models all shadow HL maps reasonably well for most benzenoids (as judged by L1-, L2-, and L∞-error norms on scaled bond currents), though all exhibit physically implausible currents for systems with fixed bonds. These comparisons inspire a new combinatorial model (Model W) based on cycle decomposition of current, taking into account the two terms of lowest order that occur in the characteristic polynomial. This improves on all pure-CC models within their range of applicability, giving excellent adherence to HL maps for all Kekulean benzenoids, including those with fixed bonds (halving the rms discrepancy against scaled HL bond currents, from 11% in the best CC model, to 5% for the set of 18 360 Kekulean benzenoids on up to 10 hexagonal rings). Model W also has excellent performance for open-shell systems, where currents cannot be described at all by pure CC models (4% rms discrepancy against scaled HL bond currents for the 20112 non-Kekulean benzenoids on up to 10 hexagonal rings). Consideration of largest and next-to-largest matchings is a useful strategy for modeling and interpretation of currents in Kekulean and non-Kekulean benzenoids (nanographenes).

Design of annulene-within-an-annulene systems by the altanisation approach. A study of altan-[n]annulenes.

The altanisation strategy, devised to design molecules with large and paratropic perimeter circulations, is applied to the family of [n]annulenes to give, altan-[n]annulenes, i.e. [n,5]coronenes. Analytical expressions are obtained for the eigenvalues of the Hückel Hamiltonian for altan-[n]annulenes, and used in conjunction with selection rules derived from the ipsocentric approach to predict patterns of global ring current in these systems. Density-functional calculations performed on seven altan-[n]annulenes, three neutral and four charged, give current-density maps in essential agreement with the predictions obtained at the unperturbed Hückel level. All but one of the systems show patterns with the tropicities expected for isolated annulenes, in line with the altanisation concept. The apparent exception is altan-[11]annulene-, the only singlet system with a well defined open-shell character in the studied set. The key role of open-shell character can be accommodated by appropriate choice of the occupation numbers of the initial Hückel molecular orbitals, where the anion altan-[11]annulene- is considered as an [11]annulene inside the [22]annulene anion.

Scaling Up Housing Services Within the Child Welfare System: Policy Insights From Simulation Modeling.

OBJECTIVES: Housing insecurity and homelessness contribute to risk of maltreatment among one in five of the nearly 3.5 million children annually investigated for maltreatment in the United States. The Family Unification Program (FUP)-a federal initiative-connects inadequately housed families involved in child welfare with long-term rental subsidies to avoid foster placement. However, FUP remains understudied and underutilized with funding levels that serve only a fraction of eligible households. The present study uses system dynamics modeling to inform decision-making by testing policies for scaling FUP. METHOD: Simulations model delivery of FUP within child welfare from a feedback perspective. Calibrated on national data, models replicate trends in child welfare involvement from 2013 through 2016, and analyses forecast rates through 2019. Experiments test policies that enhance FUP. Outcomes track system-wide rates of family separation and returns on investment of expanded housing interventions. RESULTS: Dramatic expansions of FUP benefit more families and improve marginal return on investment. Yet, scale-up fails to reduce system-wide rates of family separation or generates substantial cost-savings. CONCLUSIONS: Simulations demonstrate structural challenges for scaling FUP. Constant demand for affordable housing constrains sustainable improvements in child protection. Child welfare responses to homelessness require innovations that reduce demand for housing services through prevention and earlier intervention.

Molecular graphs and molecular conduction: the d-omni-conductors.

Ernzerhof's source-and-sink-potential (SSP) model for ballistic conduction in conjugated π systems predicts transmission of electrons through a two-wire device in terms of characteristic polynomials of the molecular graph and subgraphs based on the pattern of connections. We present here a complete classification of conduction properties of all molecular graphs within the SSP model. An omni-conductor/omni-insulator is a molecular graph that conducts/insulates at the Fermi level (zero of energy) for all connection patterns. In the new scheme, we define d-omni-conduction/insulation in terms of Fermi-level conduction/insulation for all devices with graph distance d between connections. This gives a natural generalisation to all graphs of the concept of near-omni-conduction/insulation previously defined for bipartite graphs only. Every molecular graph can be assigned to a nullity class and a compact code defining conduction behaviour; each graph has 0, 1, >1 zero eigenvalues (non-bonding molecular orbitals), and three letters drawn from {C, I, X} indicate conducting, insulating or mixed behaviour within the sets of devices with connection vertices at odd, even and zero distances d. Examples of graphs (in 28 cases chemical) are given for 35 of the 81 possible combinations of nullity and letter codes, and proofs of non-existence are given for 42 others, leaving only four cases open.

Capability Traps Impeding Homeless Services: A Community-Based System Dynamics Evaluation.

Continuums of Care (CoCs) are the primary coordinating bodies for homeless services in the United States. However, the complexities involved in delivering homeless services across interagency networks challenges coordination and system improvement. CoC governance, planning, and service provision have received little attention in academic literature, and thus, Continuums attempt to manage complex systems with little guidance. This evaluation applied community-based system dynamics with homeless consumers and service providers to (1) identify capability traps that impede services delivery and to (2) engage stakeholders in a structured system improvement process. Results revealed organizational structures for governance and planning that inhibit system outcomes. Insights led to policy and practice recommendations for the homeless system.

In search of Coulson's lost theorem.

In Hückel theory, the bond number is the sum of the orders of the π bonds incident on a given carbon center. From the work of Coulson and his school, it has been believed for over 70 years that the bond number has a maximum of 3 and that this bound is realized by exactly one conjugated framework, that of the trimethylenemethane radical. Search of published literature and archived correspondence failed to find any formal proof of these two statements. Here, we provide a new formula for bond number that leads to an easily checked proof of both. The bond number of graphene is 1.574 597… (90.9% of the mathematical limit), and this value appears to act as a separator for the classes of metallic and semiconducting single-walled nanotubes, as defined within Hückel theory.

Assessment of progress in education for children and youth with disabilities in Afghanistan: A multilevel analysis of repeated cross-sectional surveys.

Recent study shows that 617 million children and adolescents-or six out of 10 globally- are not acquiring minimum levels in literacy and mathematics, indicating the magnitude of the learning acquisition problem. For children with disabilities in context of conflict, the situation is arguably even worse: the literature shows that they face difficulties to access the education system due to multiple barriers, and when they do access, they are not learning. Our paper examines if an active education policy promoting inclusion since 2005 in Afghanistan, a protracted crisis context, has been effective. Using two cross sectional household surveys carried out eight years apart (2005-2013), our study shows that access to school and literacy did not improve between 2005 and 2013 for children and youth with disabilities. Both access and literacy outcomes were worse for girls with disabilities, those with a mental, learning or associated disability and those living in household where the head was uneducated. Finally, odds of being mentally distressed significantly declined between 2005 and 2013 indicating that schools might play a protective role for children with disabilities in Afghanistan. Our findings suggest that a multilevel multi-pronged adaptation of the existing system to improve the learning experience and promote children's resilience, particularly for children with disabilities, in conflict context such as Afghanistan, is required.

Social Cohesion, Neighborhood Collective Efficacy, and Adolescent Subjective Well-being in Urban and Rural Taiwan.

This study investigates the association between neighborhood social cohesion, collective efficacy, and adolescent subjective well-being in a nationally representative sample of Taiwanese youth. The study represents a first to adapt and test a developmental ecological model within a Chinese cultural context. Data came from the Taiwan Youth Project, which assessed representative samples of seventh graders (n = 2,690) and ninth graders (n = 2,851) from both urban and rural counties. The analytic sample included 4,988 adolescents (M age = 14.4, SD = 1.14; 50% female) in Taiwan. A path analysis estimated the direct and indirect effects of social cohesion on adolescent well-being. The results suggest that neighbors can affect young people's well-being by reinforcing their perception of safety and enhancing their self-esteem. Comparisons between youth from urban and rural areas demonstrate a general similarity in the developmental processes, though the perception of safety is less of a concern in rural areas. Findings emphasize universal aspects of neighborhood collective efficacy and developmental-ecological models, as well as allude to culturally specific dimensions in a Chinese-based context.

Solving Homelessness from a Complex Systems Perspective: Insights for Prevention Responses.

Homelessness represents an enduring public health threat facing communities across the developed world. Children, families, and marginalized adults face life course implications of housing insecurity, while communities struggle to address the extensive array of needs within heterogeneous homeless populations. Trends in homelessness remain stubbornly high despite policy initiatives to end homelessness. A complex systems perspective provides insights into the dynamics underlying coordinated responses to homelessness. A constant demand for housing assistance strains service delivery, while prevention efforts remain inconsistently implemented in most countries. Feedback processes challenge efficient service delivery. A system dynamics model tests assumptions of policy interventions for ending homelessness. Simulations suggest that prevention provides a leverage point within the system; small efficiencies in keeping people housed yield disproportionately large reductions in homelessness. A need exists for policies that ensure reliable delivery of coordinated prevention efforts. A complex systems approach identifies capacities and constraints for sustainably solving homelessness.

Can percolation theory explain the gelation behavior of diblock copolymer worms?

It is well known that polymerization-induced self-assembly (PISA) offers an efficient synthetic route for the production of highly anisotropic diblock copolymer worms. When prepared in aqueous media, such worms form thermoresponsive free-standing hydrogels that are (i) readily sterilizable, (ii) can act as a 3D matrix for the culture of normal mammalian cells and (iii) can induce stasis in human stem cell colonies. Herein we critically examine the gelation behavior of two types of diblock copolymer worms in terms of recent advances in percolation theory for rigid rods, which explicitly account for the effect of rod length polydispersity. More specifically, we use small-angle X-ray scattering (SAXS) to determine the weight-average worm contour length, L w, and the mean worm cross-sectional radius, R. This approach enables a direct comparison to be made between the theoretical critical worm volume fraction, φ c, required for gelation and the experimental values indicated by rheological measurements and tube inversion experiments. Given that these diblock copolymer worms are relatively flexible rather than truly rod-like, reasonably good agreement between these two parameters is observed, particularly for shorter, relatively stiff worms. For longer, more flexible worms a proportionality constant of approximately two is required to reconcile theory with experimental values for φ c. These findings are expected to have important implications for the aqueous gelation behavior exhibited by various other anisotropic nanoparticles, such as cellulose nanocrystals and semicrystalline block copolymer rods, and also fibril-forming small molecule (e.g. dipeptide) gelators.