Isomorphous Structures Research Articles

Fabrication and study of the strontium fluoroarsenate Sr5(AsO4)3F (SFAs) transparent ceramics

Strontium fluorarsenate Sr5(AsO4)3F optical ceramics were fabricated for the first time by vacuum hot pressing of chemically precipitated powders. The properties of these ceramics were compared with those of the well-known strontium fluorophosphate Sr5(PO4)3F. According to BET, X-ray diffraction, and scanning electron microscopy, Sr5(AsO4)3F and Sr5(PO4)3F powders have an isomorphic single-phase structure and similar particle sizes of about 100–200 nm. The transmittances of 1.5 mm thick samples are as high as 89.5% and 85.8% in the mid-IR for Sr5(AsO4)3F and Sr5(PO4)3F, respectively. The Sr5(AsO4)3F ceramics have a wider mid-IR transmission range (up to 5.8 μm) than the Sr5(PO4)3F ceramics (up to 4.5 μm).

Isomorphic Structures and Operator Analysis in Mimetic Discretizations

Isomorphic Structures and Operator Analysis in Mimetic Discretizations

Ինստիտուցիոնալ հավատարմագրման չափանիշների արդյունավետության գնահատում՝ ըստ կառուցվածքային և բովանդակային տարրերի / Assessing Effectiveness of Institutional Accreditation Criteria Through Structural and Content Elements

The article evaluates the effectiveness of institutional accreditation criteria and standards in Armenia, with a focus on their implementation and impact within the Armenian context. It examines how these criteria are perceived and used by key stakeholders, how they are aligned with established procedures and regulations, how the best practices and challenges are identified. The study delves into the impact of these indicators on the demonstration of structural normative and content isomorphism, particularly how they facilitate or hinder the processes of isonymism and isopraxism within the Armenian educational and regulatory frameworks. Additionally, the article discusses the broader European context, highlighting the adoption of quality assurance systems in Europe based on European Standards and Guidelines and emphasizes the collaborative efforts to foster transparency and mutual trust in quality assurance across European higher education institutions.

Design of High-Performance Organic Nonlinear Optical and Terahertz Crystals by Controlling the van der Waals Volume.

In the development of new organic crystals for nonlinear optical and terahertz (THz) applications, it is very challenging to achieve the essentially required non-centrosymmetric molecular arrangement. Moreover, the resulting crystal structure is mostly unpredictable due to highly dipolar molecular components with complex functional substituents. In this work, new organic salt crystals with top-level macroscopic optical nonlinearity by controlling the van der Waals volume (VvdW ), rather than by trial and error, are logically designed. When the VvdW of molecular ionic components varies, the corresponding crystal symmetry shows an observable trend: change from centrosymmetric to non-centrosymmetric and back to centrosymmetric. All non-centrosymmetric crystals exhibit an isomorphic P1 crystal structure with an excellent macroscopic second-order nonlinear optical response. Apart from the top-level macroscopic optical nonlinearity, new organic crystals introducing highly electronegative fluorinated substituents with strong secondary bonding ability show excellent performance in efficient and broadband THz wave generation, high crystal density, high thermal stability, and good bulk crystal growth ability.

Cerium(IV) Pyrasal Complexes: A pH-Dependent 8- to 10-Coordinate Cerium Chelate Switch.

In this work, five cerium(IV) complexes were synthesized, three of which were structural isomorphs from the same pyrasal ligand with the solid-state result identified by structural analysis dependent on the initial pH of the reaction solution and the temperature at which the reaction is performed. The ligands explored here are pyrasal ligands, which are Schiff-base ligands formed by the condensation of 2,3-diaminopyrazine and a salicylaldehyde derivative. Pyrasal ligands have weaker binding than other salophen-type ligands due to the electron-withdrawing effect of the nitrogen atoms contained within the pyrazine ring. The weaker binding leaves the ligand more susceptible to the changes in pH and temperature that alternate the chelating environment from 8- to 10-coordinate. This electron-withdrawing effect of the pyrazine backbone also deactivates the second amine after the first condensation addition of salicylaldehyde. Without a metal to template the complex formation reaction, even with extended reaction times and the addition of a large excess of ligand, the result is the addition of only one salicylaldehyde.

ASSOCIATIVE PLUME OF CULTURAL ARTIFACTS

The article focuses on the analysis of the associative perception of proper names. The purpose of the article is to analyze the associative plume of proper names that mark the naming of cultural artifacts of the onymic landscape. Onyms belonging to pop culture were chosen as the object of research, and their associative plume was the subject. The material of the research was 97 reactions of 30 respondents, which were submitted to three stimuli: Mona Lisa, Star Wars, Eurovision. The research methodology consists of conducting a free associative experiment with selected onyms-stimuli and analyzing the results of the experiment using the semantic gestalt of the associative field method. Reactions to the stimulus are naturally grouped around certain fragments of the conceptual picture of the world, which are reflected in this associative gestalt. Each stimulus formed a two-fold core of a semantic associative gestalt. The isomorphism of the core structure of associative gestalts does not deprive them of their originality, which is manifested in the potential of the dominant gestalt, which we associate with the fact that each cultural artifact has a multi-component structure that cannot be reflected only in a single associative plane. The distribution of onymic reactions also has a certain isomorphism: in all associative fields, anthroponymic reactions that nominate both real and virtual denotates prevail, which can be interpreted as a manifestation of the culture of participation, because in the picture of the world, the main initiator and participant of events is a person. In this way, the concept of anthropocentrism is actualized in modern Ukrainian society, which at the same time realizes and identifies itself through the prism of cultural artifacts, proper names, and a complex of memes. The respondents of the experiment were the representatives of the new generation, and their cultural picture of the world and its onymic part demonstrate commitment to tradition and, at the same time, the realization of their new understanding. All this allows us to assert that with the help of a free associative experiment it is possible to record cultural evolutionary progress.

Kabirian-based optinalysis: A conceptually grounded framework for symmetry/asymmetry, similarity/dissimilarity and identity/unidentity estimations in mathematical structures and biological sequences

This paper introduces “Kabirian-based optinalysis (KBO),” a pioneering framework that addresses the longstanding challenges in estimating symmetry/asymmetry, similarity/dissimilarity, and identity/unidentity within mathematical structures and biological sequences. The existing methods often lack a strong theoretical foundation, leading to inconsistencies and limitations. Kabirian-based optinalysis draws inspiration from isomorphism and automorphism, providing a theoretically grounded framework that unifies estimation methodologies. It introduces the concept of optiscale, autoreflective pairing, isoreflective pairing, and others ensuring invariance and robustness under various mathematical transformations and establishing functional bijectivity for isomorphic or automorphic structures. This not only overcomes previous limitations but also offers precise and interpretable estimations. Additionally, the framework introduces “geometrical pairwise analysis” to improve sensitivity to position-specific and character-specific variations in biological sequences. This novel approach enhances the accuracy of sequence similarity assessments, surpassing the constraints of conventional methods. The novelty of this work extends beyond mathematics and biology, impacting diverse fields such as computer science, data analysis, pattern recognition, and evolutionary biology. Kabirian-based optinalysis presents a holistic and theoretically grounded solution that has the potential to revolutionize the analysis of complex structures and sequences, opening new horizons for interdisciplinary research.•Inspired by automorphism and isomorphism, Kabirian-based optinalysis introduces a new paradigm-shifting and unified approach to estimations in mathematical structures and biological sequences with a solid conceptual and theoretical foundation.•The GPA method enhances pairwise sequence similarity estimation by being sensitive to position-specific and character-specific variations and providing a comprehensive characterization of these features.

Synthesis of CaNb2O6 with a Rynersonite-like Structure: Morphology, Rietveld Refinement, Optical, and Vibrational Properties.

In this study, we report the easy and low-cost synthesis of calcium niobate (CaNb2O6) with the isomorphic structure of the Rynersonite mineral for CaTa2O6. The samples were prepared by the ball milling method at room temperature at a synthesis time of 0.5, 1, 2, 3, and 4 h. The structural analysis by XRD, Rietveld refinement, and vibrational Raman spectroscopy confirms all diffraction peaks and active mode characteristics of the pure phase of CaNb2O6 for the 3-h and 4-h samples, with a crystallite size of 22.5 and 23.2 nm, respectively. The optical band gap obtained was 3.18(2) eV (3-h sample), lower than the optical band gap for niobium oxide, characteristic of materials with strong photon absorption in the UVA region of the spectrum. The surface analysis by scanning electron microscopy reveals the obtention of several agglomerates of irregular particles ranging in the submicro and micro scales. Therefore, the present approach successfully obtained calcium niobate with the formula CaNb2O6 at a short synthesis time and room temperature.

An Improved Graph Isomorphism Network for Accurate Prediction of Drug–Drug Interactions

Drug–drug interaction (DDI) prediction is one of the essential tasks in drug development to ensure public health and patient safety. Drug combinations with potentially severe DDIs have been verified to threaten the safety of patients critically, and it is therefore of great significance to develop effective computational algorithms for identifying potential DDIs in clinical trials. By modeling DDIs with a graph structure, recent attempts have been made to solve the prediction problem of DDIs by using advanced graph representation learning techniques. Still, their representational capacity is limited by isomorphic structures that are frequently observed in DDI networks. To address this problem, we propose a novel algorithm called DDIGIN to predict DDIs by incorporating a graph isomorphism network (GIN) such that more discriminative representations of drugs can thus be learned for improved performance. Given a DDI network, DDIGIN first initializes the representations of drugs with Node2Vec according to the topological structure and then optimizes these representations by propagating and aggregating the first-order neighboring information in an injective way. By doing so, more powerful representations can thus be learned for drugs with isomorphic structures. Last, DDIGIN estimates the interaction probability for pairwise drugs by multiplying their representations in an end-to-end manner. Experimental results demonstrate that DDIGIN outperforms several state-of-the-art algorithms on the ogbl-ddi (Acc = 0.8518, AUC = 0.8594, and AUPR = 0.9402) and DDInter datasets (Acc = 0.9763, AUC = 0.9772, and AUPR = 0.9868). In addition, our case study indicates that incorporating GIN enhances the expressive power of drug representations for improved performance of DDI prediction.

Selective uptake and removal of aromatic and heterocyclic compounds by para-dicyanobenzene-linked, EFe3(CO)9-incorporated (E = Te, Se), semiconducting Cu chain polymers

The uptake and removal of volatile and toxic organic compounds is an important issue in modern industrial chemistry because these organic pollutants have long-term effects on public health and the global environment. In this work, we successfully synthesized two novel para-dicyanobenzene (p-DCB)-linked, EFe3(CO)9-incorporated (E = Te, Se) 1D polymers [EFe3(CO)9Cu2(p-DCB)1.5]n (E = Te, 1a; Se, 1b) from liquid-assisted grinding (LAG) of the di-Cu compounds [EFe3(CO)9Cu2(MeCN)2] with p-DCB. Polymers 1a and 1b had isomorphous structures with single- and double-p-DCB linkers alternatively connected to Cu atoms of EFe3(CO)9Cu2 (E = Te, Se) cores, in which two p-DCB of the double-p-DCB moiety were parallel-displaced with the π···π interaction on their benzene rings. The selective adsorption of C7−C10-alkyl aromatics, polycyclic aromatics, and heterocyclic compounds by 1a and 1b was accomplished via neat grinding or THF-aided LAG processes. These reactions led to the formation of the guest molecule (G)-intercalated products, i.e., 1a- and 1b-based polymers [EFe3(CO)9Cu2(p-DCB)1.5·(G)m]n [E = Te, 1a·mG; E = Se, 1b·mG; m = 0.5 or 1] and the THF-introduced single-p-DCB-bridged polymer [TeFe3(CO)9Cu2(p-DCB)·(THF)]n (2a·1THF). These adsorption activities of 1a and 1b were thoroughly evaluated by single-crystal and powder X-ray analysis and TGA and DSC measurement, where some C−H···π, π···π, and C−H···E (E = O, S) interactions between guest molecules and the p-DCB linkers were observed to stabilize polymer chains. The desorption of volatile heterocyclic (THF, furan, thiophene) or alkyl aromatic (toluene, m-xylene, mesitylene, durene) guest molecules to give the parent polymers 1a and 1b could be achieved by vacuum and recrystallization or stepwise LAG process in the Te system. Importantly, these EFe3(CO)9Cu2-incorporated (E = Te, Se) polymers 1a and 1b, as well as their host−guest adducts, exhibited semiconducting behaviors possessing tunable energy gaps (1.36−1.51 eV) with moderate electrical conductivities ((1.21−6.55)×10–7 S·cm–1), in which the guest molecules played a crucial role in modulating the electron transport in the solid state.

Approximate isomorphism of metric structures

AbstractWe give a formalism for approximate isomorphism in continuous logic simultaneously generalizing those of two papers by Ben Yaacov [2] and by Ben Yaacov, Doucha, Nies, and Tsankov [6], which are largely incompatible. With this we explicitly exhibit Scott sentences for the perturbation systems of the former paper, such as the Banach‐Mazur distance and the Lipschitz distance between metric spaces. Our formalism is simultaneously characterized syntactically by a mild generalization of perturbation systems and semantically by certain elementary classes of two‐sorted structures that witness approximate isomorphism. As an application, we show that the theory of any ‐tree or ultrametric space of finite radius is stable, improving a result of Carlisle and Henson [8].

Unified Transformer With Isomorphic Branches for Natural Language Tracking

Natural language tracking aims to localize the target object referred to by a language description using a sequence of bounding boxes in video frames. Compared with traditional visual single object tracking initialized with only a bounding box (BBox), this task introduces high-level semantic information to reduce the ambiguity of BBox and enhance the ability to retrieve the target in a global manner. Thus, it can yield more accurate and robust tracking results. Previous methods usually adopt off-the-shelf grounding and tracking branches to tackle this task, where feature representations are learned in isolation without benefiting each other. The two branches can associate with each other to discover crucial clues since the language description and the template image provide information from different sources. Therefore, we propose a unified transformer method for natural language tracking named TransNLT, which utilizes isomorphic Transformer structures for grounding and tracking branches where collaborative learning is enabled to construct comprehensive features for the target. In addition, we propose a Selective Feature Gathering (SFG) module which can integrate cross-modal global information of the tracking target from the visual template and language description. Through effective interaction of visual and language information, we can achieve better results than tracking with only a single modality. Extensive experiments on three popular natural language tracking benchmarks show our proposed TransNLT outperforms previous state-of-the-art methods.

Factors Controlling Complex Morphologies of Isomorphous Metal-Organic Frameworks.

We demonstrate here how nitrate salts of bivalent copper, nickel, cobalt, and manganese, along with an achiral organic ligand, assemble into various structures such as symmetrical double-decker flowers, smooth elongated hexagonal bipyramids, and hexagonal prisms. Large morphological changes occur in these structures because of different metal cations, although they maintain isomorphous hexagonal crystallographic structures. Metal cations with stronger coordination to ligands (Cu and Ni) tend to form uniform crystals with unusual shapes, whereas weaker coordinating metal cations (Mn and Co) produce crystals with more regular hexagonal morphologies. The unusual flower-like crystals formed with copper nitrate have two pairs of six symmetrical petals with hexagonal convex centers. The texture of the petals indicates dendritic growth. Two different types of morphologies were formed by using different copper nitrate-to-ligand ratios. An excess of the metal salt results in uniform and hexagonal crystals having a narrow size distribution, whereas the use of an excess of ligand results in double-decker morphologies. Mechanistically, an intermediate structure was observed with slightly concave facets and a domed center. Such structures most likely play a key role in the formation of double-decker crystals that can be formed by fusion processes. The coordination chemistry results in isostructural chiral frameworks consisting of two types of continuous helical channels. Four pyridine units from four separate ligands are coordinated to the metal center in a plane having a chiral (propeller-type) arrangement. The individual double-decker flower crystals are homochiral and a batch consists of crystals having both handedness.

Noncompliance with the law as institutional maintenance at ultra‐religious schools

AbstractHow do ultra‐religious schools respond to state regulations that conflict with deep‐rooted cultural norms? This study investigates this question in the context of Haredi boys schools' decisions regarding Israel's core‐curriculum regulations. It draws on a first‐of‐its‐kind dataset of interviews and school data collected from a representative sample of 82 principals and teachers in schools serving 18,000 students and six government inspectors overseeing dozens of schools. We identify isomorphic structures of compliance and noncompliance and analyze the law's role among the competing sources of schools' decisions. These sources include rabbis, nongovernmental network supervisors, private consultants, models set by other schools, resource constraints, parents, and personal opinions. The findings reveal a tension between the law's overarching role in setting the baseline for schools' decisions and its under‐enforcement. We conceptualize this tension as a manifestation of coupled institutional maintenance, whereby ultra‐religious schools and government inspectors collaborate to maintain schools' noncompliance and autonomy.

The Perversion of Virtue―Causes and Consequences of Threats to Academic Freedom in the Contemporary University

The authors locate contemporary fissures in academic freedom in two interrelated macro-societal developments that intensified across the second half of the twentieth century: massification, involving the exponential expansion of higher education, and standardization, an isomorphism of structure and content in academic organization. The article develops a theoretic argument that the unfurling of higher education nationally and globally together with its sociocultural consistency creates a supranatural order endowed with unprecedented power centered in the core actors of universities. While these historical developments create for universities a dominant moral authority in the contemporary epoch, they also engender moralism—an evaluation of speech, writing, and behavior that venerates emotion. To illustrate the strategies of those who deploy moralism, a comparison is drawn between moralism’s contemporary instantiation in higher education and the early medieval Catholic church’s approach to perceived competitors. The comparison demonstrates that while displays of moralism in higher education may be comparatively new, their historical uses are well-worn. While massification and standardization have entailed individual and societal benefits, a rise of moralism obstructs the academic freedom on which institutions of higher education depend.

Direct Observation of Competing Prion Protein Fibril Populations with Distinct Structures and Kinetics.

In prion diseases, fibrillar assemblies of misfolded prion protein (PrP) self-propagate by incorporating PrP monomers. These assemblies can evolve to adapt to changing environments and hosts, but the mechanism of prion evolution is poorly understood. We show that PrP fibrils exist as a population of competing conformers, which are selectively amplified under different conditions and can "mutate" during elongation. Prion replication therefore possesses the steps necessary for molecular evolution analogous to the quasispecies concept of genetic organisms. We monitored structure and growth of single PrP fibrils by total internal reflection and transient amyloid binding super-resolution microscopy and detected at least two main fibril populations, which emerged from seemingly homogeneous PrP seeds. All PrP fibrils elongated in a preferred direction by an intermittent "stop-and-go" mechanism, but each population possessed distinct elongation mechanisms that incorporated either unfolded or partially folded monomers. Elongation of RML and ME7 prion rods likewise exhibited distinct kinetic features. The discovery of polymorphic fibril populations growing in competition, which were previously hidden in ensemble measurements, suggests that prions and other amyloid replicating by prion-like mechanisms may represent quasispecies of structural isomorphs that can evolve to adapt to new hosts and conceivably could evade therapeutic intervention.

Synchrotron X-ray diffraction of pyrolusite (MnO2) and rutile (TiO2) during heating to ∼1000 °C

To compare thermal expansion behaviors in isomorphic structures with different redox behaviors, we separately heated pyrolusite (Mn4+O2) and rutile (Ti4+O2) powders from 25 to ∼1000 °C at a rate of 0.05 °C/s at ambient pressure and analyzed them using synchrotron X-ray diffraction and Rietveld refinement. The pyrolusite exhibited two reduction-induced phase decompositions. Between 531 and 583 °C, pyrolusite decomposed to bixbyite (Mn3+2O3), and between 972 and 998 °C, bixbyite decomposed to hausmannite (Mn2+Mn3+2O4). The rutile experienced no phase decompositions or transitions over this same temperature interval.The refined bond lengths and angles for pyrolusite showed that the Mn4+ coordination octahedron became more distorted near the phase decomposition to bixbyite due to the approach of two coordinating oxygen atoms. The 3d electrons of each Mn4+ ion in pyrolusite make π bonds with the 2p electrons of the surrounding O2− ions, whereas the Ti4+ of rutile has no 3d electrons. Thus, π bonding between octahedral Mn4+ and the surrounding O2− anions increases the strength of the Mn–O bonds of pyrolusite relative to the Ti–O bonds of rutile. However, we observed a small decrease in O–O distances in pyrolusite before the decomposition, suggesting that at high temperature, increased π bonding between adjacent O anions precedes the release of O2 and the reduction of Mn4+ to Mn3+. Analogous behavior was observed for bixbyite before its reductive phase decomposition to hausmannite. In contrast, no anomalous changes in the O–O distances occurred for rutile.Our X-ray diffraction analyses provided accurate thermal expansion coefficients for these materials over a broader temperature range than reported in previous studies. The Mn–O bond lengths in pyrolusite were shorter and stronger than the Ti–O bonds of rutile; for example, at 60 °C, <Mn–O> bond distances in pyrolusite refined to 1.8854(6) Å whereas the <Ti–O> bond lengths of rutile were 1.9575(4) Å. Accordingly, the axial and volumetric thermal expansion coefficients refined for rutile were greater than those for pyrolusite. The axial coefficients of thermal expansion (CTE) for pyrolusite were 96% (a-axis) and 69% (c-axis) of the corresponding values for rutile, and the volumetric CTE for pyrolusite was 85% of that for rutile.

Isomorphous but No Dead Ringer: Contrasting the Supramolecular Binding of Tetrafluoroberyllate and Sulfate Ions by Nanojars

An extensive single-crystal X-ray crystallographic study of 11 nanojar structures (of which seven are novel) of the formula [anion⊂{cis-CuII(μ-OH)(μ-pz)}n]2– (anion = BeF42–, n = 28, 31, 32, CunBeF4; anion = SO42–, n = 28, 31, CunSO4; pz = pyrazolate, C3H3N2–) has been carried out, providing a detailed description of isomorphism and pseudopolymorphism in nanojars. The results point to a remarkable variety in the shape of the constituent [cis-CuII(μ-OH)(μ-pz)]x (Cux; x = 6, 8, 9, 10, 12 and 14) metallamacrocycles, despite only small differences in the coordination environment of the individual Cu2+ centers. The flexibility of the Cux rings and, ultimately, of the nanojar framework allows for the incarceration of different anions with slightly different dimensions in a nanojar of a given size, resulting in the formation of isomorphous structures in the case of CunBeF4 and CunSO4. Selectivity studies monitored by electrospray-ionization mass spectrometry (ESI-MS) and proton nuclear magnetic resonance spectroscopy (1H NMR) reveal that despite the virtually identical H-bonding pattern around the two anions in nanojars of a given size, SO42– is strongly preferred over BeF42–. The origins of this selectivity are discussed, along with the nature of bonding in the two isosteric anions. Lastly, the crystal structure of (Bu4N)3Be2F7(H2O)3 documents the formation of the Be2F73– ion from BeF42–.

Enhanced Catalytic Activity of TEMPO-Mediated Aerobic Oxidation of Alcohols via Redox-Active Metal-Organic Framework Nodes.

Metal-organic frameworks (MOFs) are outstanding platforms for heterogeneous catalysis due to their tunable pore size, huge surface area, large porosity, and potential active sites. The design and synthesis of MOF/organocatalyst co-catalytic systems have attracted considerable interest owing to their high catalytic activity, low toxicity, and mild reaction conditions. Herein, we reported the synthesis of a bifunctional TEMPO-IsoNTA organocatalyst featuring a pyridyl group as an anchoring site and a TEMPO radical as a catalytic active site. By using the topologically isomorphic structures of MIL-101(Fe) and MIL-101(Cr) as co-catalysts, these MOF/TEMPO-IsoNTA systems enable the efficient aerobic oxidation of various alcohols to their corresponding aldehydes or ketones under mild conditions. Notably, the MIL-101(Fe)/TEMPO-IsoNTA system exhibits superior catalytic activity, thanks to their redox-active FeIII-oxo nodes, which facilitate the regeneration of TEMPO-IsoNTA. Our research not only solves the problem of potential heavy metal contamination in the TEMPO-based homogeneous catalytic system, but also enriches the understanding of synergism of MOFs/organocatalysts.

Structural properties and isomorphism theorems for Cayley digraphs of full transformation semigroups with respect to Green's equivalence classes

Let T(X) be the full transformation semigroup on a nonempty set X. In this paper, the Cayley digraphs of T(X) with connection sets L and R, the Green's equivalence classes of T(X) according to the Green's relations L and R, are investigated. Furthermore, their connectedness properties are characterized. In addition, the isomorphism theorems for Cayley digraphs of T(X) are also presented.