Active Space Research Articles

Effect of Oriented External Electric Field in Altering Magnetic Exchange and Magnetic Anisotropy in Lanthanide-Radical Complexes.

Magnetic exchange coupling (J) is one of the important spin Hamiltonian parameters that control the magnetic characteristics of single-molecule magnets (SMMs). While numerous chemical methodologies have been proposed to modify ligands and control the J value, and magneto-structural correlations have been developed accordingly, altering this parameter through non-chemical means remains a challenging task. This study explores the impact of an Oriented-External Electric Field (OEEF) on over twenty lanthanide-radical complexes using Density Functional Theory (DFT) and ab initio Complete Active Space Self-Consistent Field (CASSCF) methods. Five complexes - [{(Me3Si)2N]2Gd(THF)}2(μ-η2:η2-N2)] (1), [Gd(Hbpz3)2(dtbsq)] (2), [Gd(hfac)3(IM-2py)] (3), [Gd(hfac)3(NITBzImH)] (4), and [Gd(hfac)3{2Py-NO}(H2O)] (5) - were selected for detailed analysis, revealing significant OEEF effects on magnetic exchange interactions and structural parameters. Various parameters such as bond distances, bond angles, and torsional angles were examined as a function of OEEF to establish guiding principles for molecule selection. In complexes 1, 2, and 3, OEEF influenced torsional angles and altered exchange interactions. Complex 4 demonstrated enhanced ferromagnetic coupling under OEEF, reaching a maximum J value of +5.3 cm-1. Complex 5 reveals switching the sign of JGd-rad exchange interaction from antiferromagnetic to ferromagnetic under OEEF, highlighting the potential of electric fields in designing materials with tuneable magnetic properties. These findings offer valuable insights for future research and applications in advanced materials and molecular electronics.

Superacid-Synthesized Fluorinated Diamines Act as Selective hCA IV Inhibitors.

Carbonic anhydrase (CA) IV is a membrane-bound enzyme involved in important physio-pathological processes, such as excitation-contraction coupling in heart muscle, central nervous system (CNS) extracellular buffering, and mediation of inflammatory response after stroke. Known since the mid-1980s, this isoform is still largely unexplored when compared to other isoforms, mostly for the current lack of inhibitors targeting selectively this isoform. The discovery of selective CA IV inhibitors is thus largely awaited. In this work, we report β-(di) fluoropropyl diamines as effective CA IV inhibitors, opening real perspectives for a new mode of selective inhibition of this isoform. Inhibition data reveal that the essential structure core to ensure a potent and selective inhibition of CA IV is the N-propyldiamine. Molecular modeling studies were employed to understand the binding mode of the synthesized amines. Conformational searches within the active site space carried out in an implicit solvent (water) model were also conducted.

Ground and Excited States from Ensemble Variational Principles

The extension of the Rayleigh-Ritz variational principle to ensemble states ρw≡∑kwk|Ψk⟩⟨Ψk| with fixed weights wk lies ultimately at the heart of several recent methodological developments for targeting excitation energies by variational means. Prominent examples are density and density matrix functional theory, Monte Carlo sampling, state-average complete active space self-consistent field methods and variational quantum eigensolvers. In order to provide a sound basis for all these methods and to improve their current implementations, we prove the validity of the underlying critical hypothesis: Whenever the ensemble energy is well-converged, the same holds true for the ensemble state ρw as well as the individual eigenstates |Ψk⟩ and eigenenergies Ek. To be more specific, we derive linear bounds d−ΔEw≤ΔQ≤d+ΔEw on the errors ΔQ of these sought-after quantities. A subsequent analytical analysis and numerical illustration proves the tightness of our universal inequalities. Our results and particularly the explicit form of d±≡d±(Q)(w,E) provide valuable insights into the optimal choice of the auxiliary weights wk in practical applications.

Relativistic Prolapse-Free Gaussian Basis Sets of Double- and Triple-ζ Quality for s- and p-Block Elements: (aug-)RPF-2Z and (aug-)RPF-3Z.

This study presents two new relativistic Gaussian basis sets without variational prolapse of double- and triple-ζ quality, RPF-2Z and RPF-3Z, along with augmented versions including additional diffuse functions, aug-RPF-2Z and aug-RPF-3Z, which are available for all s and p block elements from Hydrogen to Oganesson. The exponents of the Correlation/Polarization (C/P) functions are obtained from a polynomial version of the generator coordinate Dirac-Fock method (p-GCDF). The choice of C/P functions was guided by multireference configuration interaction calculations with single and double excitations (MR-CISD) based on a valence active space. Finally, calculations of fundamental properties done for atomic and molecular systems (bond lengths, vibrational frequencies, dipole moments, and electron affinities) ensure the expected quality of these new basis sets, which may also exhibit some computational efficiency advantages. Additionally, the prolapse-free feature of these sets must provide a reliable description of properties more dependent on core electron distributions, as well.

Children’s Perspectives of Neighbourhood Spaces: Gender-Based Insights From Participatory Mapping and GIS Analysis

Although several urban design and planning features, such as community spaces, green infrastructure, and traffic measures that prioritise pedestrians and children, have been identified as important characteristics of child-friendly cities and neighbourhoods, there remains a gap in our understanding regarding the specific elements of children’s daily environments that influence their experiences. This study focuses on the everyday activity spaces of children (aged 9–12) living in physically and socially diverse neighbourhoods of low-to-average income in Ankara, Turkey. Drawing on findings from thematic and qualitative GIS-based analyses of 40 participatory map-based focus groups with 217 children, this study aims to understand how neighbourhood design influences children’s everyday experiences across different neighbourhood types and genders. By visualising children’s perceptions of their neighbourhoods and activity spaces, and thematically analysing their comments related to neighbourhood design features that may facilitate positive and negative experiences, this child-centred study contributes to the limited research on children’s experiences of place. Our findings revealed key neighbourhood design features influencing children’s experiences and highlighted gender-based differences. While natural settings were valued across settings and genders, boys reported more physical activities in open spaces while girls more frequently emphasised the need for accessible playgrounds and natural settings. Children in urban neighbourhoods frequented streets, parks, and local shops more often, while those in suburban and sprawling areas preferred amenities near their homes. The study demonstrates that children’s positive everyday experiences can be supported by modifying the neighbourhood design, providing valuable insights for practitioners and policymakers on developing more child-friendly neighbourhoods.

Neighborhoods, Networks, and HIV Care Among Men Who Have Sex With Men: Proposal for a Longitudinal Study.

The majority of people living with HIV in the United States are men who have sex with men (MSM), with race- and ethnicity-based disparities in HIV rates and care continuum. In order to uncover the neighborhood- and network-involved pathways that produce HIV care outcome disparities, systematic, theory-based investigation of the specific and intersecting neighborhood and social network characteristics that relate to the HIV care continuum must be engaged. Using socioecological and intersectional conceptual frameworks, we aim to identify individual-, neighborhood-, and network-level characteristics associated with HIV care continuum outcomes (viral suppression, retention in care, and antiretroviral adherence) among MSM living with HIV in New York City. In the longitudinal cohort study, we assess 3 neighborhoods of potential influence (residential, social, and health care access activity spaces) using Google Earth. We investigate the influence of neighborhood composition (eg, concentrated poverty and racial segregation) and four neighborhood-level characteristics domains: (1) community violence, physical disorder, and social disorganization (eg, crime rates and housing vacancy); (2) alcohol and other drug use; (3) social norms (eg, homophobia and HIV stigma); and (4) community resources (eg, social services and public transit access). We test theoretical pathways of influence, including stress or coping, stigma or resilience, and access to resources, across the different neighborhoods in which MSM live, socialize, and receive HIV care. At each visit, we locate each participant's reported activity spaces (ie, neighborhoods of potential influence) and collect individual-level data on relevant covariates (including perceptions of or exposure to neighborhoods) and social network inventory data on the composition, social support, and perceived social norms. The outcomes are HIV viral suppression, retention in care, and antiretroviral adherence. These data are combined with an existing, extensive geospatial database of relevant area characteristics. Spatial analysis and multilevel modeling are used to test the main theory-driven hypotheses and capture independent neighborhood-level and network-level effects and changes over time. The study began enrollment in March 2019 and concluded visits in December 2023, with a total of 327 participants enrolled. The median age was 44.1 (SD 11.5) years. Almost all participants self-identified as cisgender men (n=313, 98.1%) and as gay, homosexual, or bisexual (n=301, 94.4%). Overall, 192 (60.1%) participants identified as non-Hispanic Black, and 81 (25.3%) identified as Hispanic. Most (n=201, 63%) reported at least occasional difficulty in meeting basic needs (eg, rent and food) in the past 6 months. The mean number of years living with HIV was 15.4 (SD 10.1). This study will have direct implications for the design of multilevel interventions, addressing factors at the neighborhood, network, and individual levels. Results may inform urban planning and program design to improve HIV care outcomes for MSM, particularly for Black and Latino MSM living in urban areas. PRR1-10.2196/64358.

Sustainable micro renewal and renovation of arts town in China: Intermingling design of contemporary art and Chinese classical garden

<p>The gardening philosophy of Chinese classical gardens is an integral part of China’s rich traditional culture, reflecting ancient scholars’ understanding of nature and humanity and embodying aesthetic and philosophical values. With the progression of time, integrating the principles of Chinese classical garden gardening into contemporary space design has emerged as a critical issue in contemporary public space design. This study uses the Butong Arts Town in Qinhuangdao as a case study, focusing on applying Chinese classical garden gardening concepts in public space design and regional micro-renovation. Special attention is given to nodes that simultaneously serve interactive and recreational functions. In the micro-renovation of the Butong Arts Town area, Chinese classical garden gardening principles can be employed through greening, landscaping, and other means to enhance the quality of the space. Additionally, by integrating local cultural characteristics, it is possible to create public spaces with distinct regional features, providing a comfortable and pleasant environment for artists, designers, planners, and tourists. The design methods used in this study explore the behavioral characteristics and usage needs of various groups from multiple perspectives, aiming to optimize activity spaces. This research identifies the main issues within the target areas and proposes corresponding improvement measures to enhance the functionality and aesthetic quality of the space. The aim is to integrate people’s growing spiritual pursuits with public activity spaces, providing new references and ideas for future sustainable space design.</p>

Impact of urban landscape patterns on butterfly diversity in Fuzhou City parks

Butterflies are crucial bioindicators of urban environmental changes. Utilizing urban green spaces to create ecological corridors and habitats is essential for maintaining biodiversity. Therefore, understanding the factors that influence landscape patterns in urban green spaces and their impact on butterfly diversity is crucial. This study investigated how landscape patterns in urban green spaces affect butterfly diversity through a year-long survey across 24 urban parks in Fuzhou. The main findings were as follows: (1) A total of 7786 butterflies from 59 species were recorded, with the highest species diversity and richness observed in Fushan Country Park. Seasonal abundance peaked in summer, while richness was highest in autumn. Species composition varied significantly across park types. (2) Monophagous butterfly diversity was positively correlated with woodland proportion and negatively to waterbody largest patch index. Polyphagous and oligophagous butterfly diversity showed positive correlations with woodland aggregation index and grassland proportion within 500 m buffers, but negative with construction land proportion. Factors such as the waterbody proportion and landscape division index influenced butterfly diversity in different activity spaces. (3) Butterfly communities with different feeding types and vertical activity space ranges responded differently to landscape pattern indices. Seasonal variations indicated that polyphagous butterflies and those occupying the middle activity space exhibited similar responses to environmental factors.

The social commentary of Squid Game: reflections on Korean art, space and inequality

This paper discusses how communal spaces of childhood activity in Korea are reimagined in the drama Squid Game as part of a social commentary on class and economy. Many spaces shown in Squid Game are nostalgic representations of common Korean playgrounds, parks, and urban neighborhoods. In the show, however, these spaces of delightful memory are transformed into gory places where the literalized violence of neoliberal capitalism plays out. I argue that the creators of the show participate in a history of understanding communal spaces as focal points of social structure and expression that have been crucial in Korea since the Joseon Dynasty (1392–1897). The use of such spaces over centuries, including their reenvisioning in modern media, illustrates how political and economic relationships are intimately tied to constructions and perceptions of space. Through a detailed structural, visual, and semiotic analysis of the communal spaces of historical and modern urban Korea, and a comparison with the spaces in Squid Game, I argue that social spaces are intimately tied to social hierarchies and the long history of inequality in Korea.

Assessing Appropriation of Space in Urban Green Spaces: Three Case Studies in Downtown Shanghai

This study investigated patterns of activities in urban green spaces (UGSs) in downtown Shanghai. UGSs are essential public infrastructure, contributing to urban sustainability, quality of life, and social cohesion. Although widely studied, there is a gap in the literature regarding Chinese UGSs when the object of study is the nature the activities. In this sense, we aimed to investigate the activities from the perspective of appropriation of the space, considered here as different from the use of space. This study addressed this by analyzing user demographics, frequency, and spatial activity patterns to assess how these activities could be classified and scored according to a varying levels of appropriation. Through a mixed-methods design based on non-participant observation and behavior mapping, the study was conducted across three comprehensive parks in Shanghai, divided into nine observation zones. The data were analyzed through descriptive statistics, IBM SPSS, and qualitative coding, revealing, as the main findings, sixty distinct activity types, a soft to moderate level of appropriation, and notable variations in demographic presence and temporal trends. This research underscores the effectiveness of observational methods, validates appropriation as an analytical category, and emphasizes the importance of structured classification systems for improving the understanding of UGSs’ socio-spatial performance and their societal role.

Reduced Scaling Correlated Natural Transition Orbitals for Multilevel Coupled Cluster Calculations.

Multilevel coupled cluster theory offers reduced scaling computation of intensive properties in systems that are too large for standard coupled cluster calculations. A significant benefit of the multilevel coupled cluster framework is the possibility of calculating intensive properties that are not tightly localized if an appropriate set of active orbitals is used. Correlated natural transition orbitals (CNTOs) are tailored to describe excitation processes. For multilevel coupled cluster singles and doubles (MLCCSD) and singles and perturbative doubles (MLCC2) calculations, the construction of CNTOs generally becomes the computational bottleneck. Here, we demonstrate how CNTOs can be obtained with operations, eliminating the -scaling steps involved in the original approach. This reduction in scaling moves the bottleneck of MLCC2 and MLCCSD calculations from the active orbital space preparation to the MLCC2 and MLCCSD equations with -scaling.

Exact-Two-Component Complete Active Space Method with Variational Treatment of Magnetic Field and Spin-Orbit Coupling: Application to X-ray Magnetic Circular Dichroism Spectroscopy.

We introduce an exact-two-component complete active space self-consistent-field (X2C-CASSCF) method formulated under the restricted-magnetic-balance condition. This framework allows for the nonperturbative treatment of static magnetic fields using gauge-including atomic orbitals (GIAOs). The GIAO-X2C-CASSCF methodology effectively captures all microstates within the same 2J + 1-degenerate manifold and their splitting in a static magnetic field, which are not accessible through single-reference-based methods. We also present mathematical recursive expressions for evaluating one-electron relativistic integrals by using GIAOs in the presence of a finite magnetic field. Benchmark studies include oxygen and nitrogen K-edge X-ray magnetic circular dichroism spectroscopy (XMCD) for closed-shell organic compounds, as well as L-edge XMCD spectroscopy for the high-spin open-shell transition metal ion Mn2+ and the tetrahedral Mn(II)O46- complex.

Extending GPU-accelerated Gaussian integrals in the TeraChem software package to f type orbitals: Implementation and applications.

The increasing availability of graphics processing units (GPUs) for scientific computing has prompted interest in accelerating quantum chemical calculations through their use. However, the complexity of integral kernels for high angular momentum basis functions often limits the utility of GPU implementations with large basis sets or for metal containing systems. In this work, we report the implementation of f function support in the GPU-accelerated TeraChem software package through the development of efficient kernels for the evaluation of Hamiltonian integrals. The high efficiency of the resulting code is demonstrated through density functional theory (DFT) calculations on increasingly large organic molecules and transition metal complexes, as well as coupled cluster singles and doubles calculations on water clusters. Preliminary investigations into Ni(I) catalysis with DFT and the photochemistry of MnH(CH3) with complete active space self-consistent field are also carried out. Overall, our GPU-accelerated software appears to be well-suited for fast simulation of large transition metal containing systems, as well as organic molecules.

Block-Correlated Coupled Cluster Theory Based on the Generalized Valence Bond Reference for Singlet-Triplet Energy Gaps of Strongly Correlated Systems.

A block-correlated coupled cluster (BCCC) method based on the triplet generalized valence bond (GVB) wave function (GVB-BCCC) has been implemented for the first time. By introducing several techniques, we have developed a practical and efficient GVB-BCCC code. The GVB-BCCC3 method (with up to three-pair correlation) can be used to deal with strongly correlated (SC) systems with triplet or singlet ground states, allowing singlet-triplet (S-T) energy gaps in the active space of SC systems computationally available. For selected SC systems, our calculations show that GVB-BCCC3 can always provide correct ground-state spin multiplicity as the complete active space configuration interaction (CASCI) or density matrix renormalization group (DMRG). Furthermore, we found that the S-T energy gaps from GVB-BCCC3 are quite consistent with CASCI or DMRG results. This work demonstrates that GVB-BCCC3 is a promising theoretical tool for describing S-T energy gaps within the active space of SC systems with large active spaces.

Perception of the Urban Space of the Waorani Nationality in Shell Township, Pastaza, Ecuador

The township of Shell in the Province of Pastaza, Ecuador was initially an exploration base and later, a missionary base for evangelization of the peoples and nationalities of the Amazon. It plays an important role in the Waorani nationality and its social, cultural and economic dynamics, especially in the Nuevo Amanecer neighborhood, which is home to approximately 43 Waorani families whose epicenter has become a strategic space for their territorial dynamics. The research, through ethnographic methodologies and field work, has allowed to establish the perception from the Waorani nationality to the urban space. During the development of this study two sources of information were applied: methodological bibliography and thematic content reference. The study of 120 members of 43 Waorani families of the Ecuadorian Amazon and a process of direct observation, as a participant observer during the years 2019-2020-2021-2022, resulted in a conceptual model Bailey (1996), where the Waorani use preferences of displacement, economic attributes of the area, location of residence, representation of the spatial-urban structure, space-action, time of stay, activity space and objective spatial structure of the urban environment; and a transect as a very effective method to recognize population movements, sectoral differences, topographic slopes and social dynamics presented in the territory from a plan and elevation view. Human beings adapt easily to new spaces, in spite of cultural and social differences, their assimilation processes will depend on their capacity to approach and accept the environment. The Nuevo Amanecer settlement has motivated families to move to peri-urban or urban spaces in intermediary cities, which has provoked a forced adaptation and assimilation due to the same processes involved in rural-urban relations. Received: 30 May 2024 / Accepted: 21 October 2024 / Published: 05 November 2024

Active and sedentary use of public open spaces in Asian countries

ABSTRACT Public open spaces are important resources for physical activity. Observational studies conducted in Western countries found that public open spaces users tend to be mostly sedentary, while a few studies conducted in Asia (China, Thailand) reported more active patterns of public open spaces use. To better understand in what ways public open spaces are used in Asia, we examined how active and sedentary public open spaces users were in Bangladesh and the Philippines, where no research on this topic has been conducted. We collected data from adult visitors of 10 public open spaces using on-site intercept surveys, in which they reported the duration of active and sedentary use of public open spaces. The mean total time spent in public open spaces by 804 participants was 53 min (standard deviation: 19 min). A high level of active public open spaces use was observed: about 70% of the time in public open spaces was active (65% in Bangladesh, 73% in the Philippines). However, women and older adults were less active in public open spaces than their counterpart. Our findings suggest that producing more public open spaces and promoting public open spaces use in these Asian countries may help to increase adults’ physical activity. Future research should identify features of public open spaces that can encourage women and older adults to engage in active public open spaces use.

The Problem of Shrinkage of the Active Space in Russia and the Possibilities of Its' Solution

The Problem of Shrinkage of the Active Space in Russia and the Possibilities of Its' Solution

(Wo)Man-Made Public Space

Women experience limitations in public space regarding their safety, comfort, and accessibility, which might be mitigated by urban design. This article addresses the question: How can public space become more gender-inclusive through the implementation of design principles focused on meeting the needs of women? It draws on existing literature combined with empirical observations and interviews, to establish a framework of eight design principles (safety cues, informal surveillance, legibility, spatial appropriation, representation, diversity, slow modes and ease of use) to make public spaces more gender-inclusive. The principles are applied in an exemplary design case focused on a public street in the city centre of Heerlen, Netherlands , which currently faces many of the issues that are especially limiting to women. Active public spaces, meaning spaces that encourage user engagement and interaction, often already contain some elements outlined in the framework, leading to easier fulfilment of the design principles. The application of the principles is limited to one design case, and the focus is restricted to women’s experiences. When applying the principles in other cases or typologies, the implications of the proposed design guidelines need to be carefully considered.

Small tensor product distributed active space (STP-DAS) framework for relativistic and non-relativistic multiconfiguration calculations: Scaling from 109 on a laptop to 1012 determinants on a supercomputer

Despite the power and flexibility of configuration interaction (CI) based methods in computational chemistry, their broader application is limited by an exponential increase in both computational and storage requirements, particularly due to the substantial memory needed for excitation lists that are crucial for scalable parallel computing. The objective of this work is to develop a new CI framework, namely, the small tensor product distributed active space (STP-DAS) framework, aimed at drastically reducing memory demands for extensive CI calculations on individual workstations or laptops, while simultaneously enhancing scalability for extensive parallel computing. Moreover, the STP-DAS framework can support various CI-based techniques, such as complete active space (CAS), restricted active space, generalized active space, multireference CI, and multireference perturbation theory, applicable to both relativistic (two- and four-component) and non-relativistic theories, thus extending the utility of CI methods in computational research. We conducted benchmark studies on a supercomputer to evaluate the storage needs, parallel scalability, and communication downtime using a realistic exact-two-component CASCI (X2C-CASCI) approach, covering a range of determinants from 109 to 1012. Additionally, we performed large X2C-CASCI calculations on a single laptop and examined how the STP-DAS partitioning affects performance.

Residential and experienced social segregation: the roles of different transport modes, metro extensions, and longitudinal changes in Hong Kong

Social segregation is a challenge intensified by rapid urbanisation. Using mobility data, researchers have widened the scope of analysis from static residential segregation patterns to experienced segregation in activity space. Despite such progress, we have yet to decipher how social segregation evolves with the urban development process. The different roles of transport modes, major transport infrastructure expansion, and longitudinal changes over decades are rarely captured. This study utilises three Hong Kong Travel Characteristics Surveys data from 1992 to 2011 to analyse the city’s social mixing changes. Detailed mobility and socio-demographic data of 101,385 (2011), 92,520 (2002) and 77,271 (1992) individuals were included. We found that the unequal experience of social segregation among different social demographic groups has persisted across the two decades. Nevertheless, public transit has a significant effect in increasing social mixing, thereby moderating the experienced social segregation. The roles of buses and the metro system are particularly noteworthy. Nonetheless, we found a selection bias of new metro stations in areas of high social mixing already. Over time, the metro expansion plays a paradoxical role. On one hand, the metro stations’ immediate catchment areas have seen a decreased low-income population. On the other hand, the increased number of metro trips allows people to have a more diverse experience.