Density Topology Research Articles

Influence of the Fe(II) Spin State on Iron-Ligand Bonds in Heme Model Iron-Porphyrin Complexes with 4, 5 and 6 Ligands.

In this work heme models with four [Fe(II)(P)], five [Fe(II)(P)Im], [Fe(II)(P)O2] and six ligands [Fe(II)(P)(Im)O2], where P=porphyrin, with different spin states (ms=5, 3 and 1) of the iron atom were investigated using relativistic-corrected quantum chemistry methods (PW6B95-D3-DKH/jorge-TZP-DKH). Dependence of the iron-ligand bond properties on (i) spin state and (ii) number of ligands were analyzed using natural bond orbital analysis, electron density topology, electrostatic potential and electron localization function. It is shown that reversible binding of O2 is possible in case of formation of semicoordination bond between Fe(II) and imidazole. Binding of the fifth and sixth ligand from the energetic and orbital points of view is more favorable for the triplet Fe(II) state. At the same time for the six-coordinated complex [Fe(II)(P)(Im)O2] interconversion of Fe(II) electrons of valent 3d orbital from quintet to triplet and vice versa is possible under thermal fluctuations (energy barriers less than 2 kcal/mol).

Impact response of additively manufactured density-graded open-cell foams

Additive manufacturing has made it possible to fabricate materials that were unachievable with traditional methods. This study focuses on understanding the deformation behavior and energy absorption mechanics of additively manufactured cellular materials with gradually varying densities. Foams have unique deformation behavior due to their intricate topology and composition, resulting in excellent energy dissipation capability. Varying the density can significantly influence their deformation response and improve energy absorption and impact resistance. Voronoi tessellation is employed to model the foams, as it effectively captures the cell morphology in foam structures and produces stochastic cellular topologies accurately. Resin-based additive manufacturing techniques are employed to fabricate cellular materials with varying density configurations for low-velocity and high-velocity impact experiments. The study demonstrates that density-graded foams effectively dissipate a broad spectrum of impact energies, surpassing uniform counterparts by transmitting reduced stress, especially at lower energy levels. This characteristic enhances their suitability for advanced energy absorption applications. The results also show that at high impact velocities, the direction of density gradation influences energy dissipation and peak stress transmission.

Isolation of Elusive Fluoflavine Radicals in Two Differing Oxidation States.

Facile access and switchability between multiple oxidation states are key properties of many catalytic applications and spintronic devices yet poorly understood due to inherent complications arising from isolating a redox system in multiple oxidation states without drastic structural changes. Here, we present the first isolable, free fluoflavine (flv) radical flv(1-•) as a bottleable potassium compound, [K(crypt-222)](flv•), 1, and a new series of organometallic rare earth complexes [(Cp*2Y)2(μ-flvz)]X, (where Cp* = pentamethylcyclopentadienyl, X = [Al(OC{CF3}3)4]- (z = -1), 2; X = 0 (z = -2), 3; [K(crypt-222)]+ (z = -3), 4) comprising the flv ligand in three different oxidation states, two of which are paramagnetic flv1-• and flv3-•. Excitingly, 1, 2, and 4 constitute the first isolable flv1-• and flv3-• radical complexes and, to date, the only isolated flv radicals of any oxidation state. All compounds are accessible in good crystalline yields and were unambiguously characterized via single-crystal X-ray diffraction analysis, cyclic voltammetry, IR-, UV-vis, and variable-temperature EPR spectroscopy. Remarkably, the EPR spectra for 1, 2, and 4 are distinct and a testament to stronger spin delocalization onto the metal centers as a function of higher charge on the flv radical. In-depth analysis of the electron- and spin density via density functional theory (DFT) calculations utilizing NLMO, QTAIM, and spin density topology analysis confirmed the fundamental interplay of metal coordination, ligand oxidation state, aromaticity, covalency, and spin density transfer, which may serve as blueprints for the development of future spintronic devices, single-molecule magnets, and quantum information science at large.

Research on topology optimization strut-and-tie model and prestress construction for cable-pylon anchorage zone of Fengshuba Bridge

To address the challenges associated with accurate load-bearing capacity calculation and prestress design for the cable-pylon anchorage zone of cable-stayed bridges, a case study focusing on the Fengshuba Bridge is conducted. Utilizing the Solid Isotropic Material with Penalization (SIMP) variable density topology optimization method, a strut-and-tie model (STM) is constructed for the cable-pylon anchorage zone. This model is subsequently employed to verify load-bearing capacity of the struts and nodes within the cable-pylon anchorage zone, as well as to calculate the required quantity of circumferential prestressing tendons. Additionally, a spatial segmental finite element model is established for the cable-pylon anchorage zone to perform a detailed analysis of prestressed structural optimization. This analysis determines various structural details, including the arrangement of prestressing tendons along the height, the design for prestressing blind zones, and the quantity of prestressing tendons. Subsequently, the optimized model is subjected to stress verification. The research results indicate that the adoption of dispersed tendon arrangement results in reduced principal tensile stress within the cable-pylon anchorage zone, in contrast to the concentrated tendon arrangement. The introduction of short prestressing steel bundles within the conduit of prestressing blind zones uniformly enhances the pre-compressive stress on the cable-pylon side wall. Due to the Poisson effect of materials, it is necessary to arrange prestressing tendons appropriately within the cable-pylon anchorage zone. Arranging prestressing steel bundles according to the proposed STM and structural optimization method adequately fulfills the structural force requirements of the cable-pylon anchorage zone.

Topology-optimized thermal metamaterials based on inhomogeneous and anisotropic unit array

In this paper, inhomogeneous and anisotropic thermal metamaterials are designed to achieve the manipulation of heat flow (MHF) at multiple points. The thermal metamaterial unit is constructed from mixtures of two solid-state materials with different thermal conductivities. A variable density topology optimization method is employed to design the filling fractions of the mixed materials within the unit. The thermal concentrator and cloak are designed through the optimization of the topological functional units (TFUs). The thermal gradients of 14 and 0.05 times the uniform thermal gradient are achieved by the concentrator and the cloak, respectively. The effectiveness of the proposed design method is validated through the excellent agreement between numerical simulations and experimental results.

Lower density soft operators and density soft topologies

The classical density topology is derived from the Lebesgue density points of Lebesgue measurable sets. Wilczynski proposed a more general scheme for defining density points. It turns out that his scheme works in the category sense in addition to the measure-theoretic one. The sets of density points necessitate some properties of the operator of density points. Such an operator is named the lower density operator. In this theme, we introduce lower density soft operators on (abstract) chargeable soft spaces along with their basic properties. Among others, we show that each lower density soft operator defines a system of parametric lower density operators. Then, we study density soft topologies, the soft topologies generated by lower density soft operators. The main attributes and topological properties of density soft topologies are analyzed. We finalize this work by demonstrating several characterizations of (simple) soft density topologies. In particular, we prove that in density soft topologies, the Borel soft σ-algebra coincides with the soft σ-algebra of soft sets with the Baire property.

ANISOTROPY AND MECHANICAL CHARACTERISTICS OF ULTRA-HIGH PERFORMANCE CONCRETE AND ITS INTERPENETRATING PHASE COMPOSITE WITH TRIPLY PERIODIC MINIMAL SURFACE ARCHITECTURES

Abstract This work numerically explores the anisotropy, impact phase wave propagation, buckling resistance, and natural vibration of ultra-high performance concrete (UHPC) and UHPC-steel interpenetrating phase composite (IPC) with triply periodic minimal surfaces (TPMSs), including sheet and solid Gyroid, Primitive, Diamond, and I-WP. The experiment is conducted verifying the accuracy of the numerical model in terms of Young's modulus of polylactic acid (PLA)-based TPMS lattices and PLA-cement IPCs with TPMS cores, with the highest percent difference of 15% found for IPCs and 17% found for lattice. The results indicate that UHPC material with sheet Gyroid exhibits the least extreme anisotropy in response to the varying orientation among other lattices regardless of the change of solid density, making it the ideal candidate for construction materials. Interestingly, compared to UHPC-based TPMS lattice, IPCs possess a much smaller anisotropy and exhibit almost isotropy regardless the variation of solid density and TPMS topology, offering a free selection of TPMS type to fabricate IPCs without much care of anisotropy. The phase wave and buckling resistance of UHPC- and IPC-based beams with TPMSs nonlinearly decrease with a drop of TPMS solid density, but it is the almost linear pattern for the case of natural vibration frequency. UHPC material and IPC with sheet Gyroid lattice are found to possess the lowest phase wave velocity and exhibit the least anisotropy of wave propagation, showing it as an ideal candidate for UHPC material to suppress the destructive energy induced by the external impact.

Structural Investigation of Schiff Base Ligand and Dinuclear Copper Complex: Synthesis, Crystal Structure, Computational, and Latent Fingerprint Analysis.

The structural studies of the fluorinated Schiff base ligand and its copper complex were synthesized and characterized by Fourier transform infrared, UV-visible, and photoluminescence spectroscopy. Single-crystal X-ray diffraction analysis unveils a dinuclear copper complex arising from double bridging acetate anions to copper ions that are chelated by the tridentate Schiff base ligand Cu(LS). The trigonality index τ5 of 0.080 indicates a distorted square pyramidal coordination geometry for the metal. The SL ligand and complex exhibit intra- and intermolecular interactions, leading to unique supramolecular architectures. The structural changes between the free halogenated Schiff base ligand and upon coordination with the metal were extensively studied by experimental and theoretical approaches. The intra- and intermolecular interactions have been analyzed by Hirshfeld surface and quantum theory of atoms in molecules analysis, and the enrichment ratio highlights the most favored interactions in the formation of molecular packing. The chemical and physical properties, such as the HOMO - LUMO energy gap, chemical reactivity, and electron density topology, are studied using density functional theory studies. In addition, the Schiff base ligand compound is used to study the latent fingerprint analysis.

Prediction of charge density wave, superconductivity and topology properties in two-dimensional Janus 2H/1T-WXH (X = S, Se)

The multiple properties in two-dimensional (2D) materials have attracted widespread attention. Utilizing first-principles calculations, we theoretically predict four 2D transition metal Janus sulfide hydrides, named 2H/1T-WXH (X = S, Se). The 2H-WSH and 2H–WSeH demonstrate superconductivity with critical temperatures (Tc) of 13.4 K and 11.4 K, respectively. Whereas 1T-WSH and 1T-WSeH display charge density wave (CDW) properties arising from electron-phonon coupling (EPC). It is noteworthy that the CDW can be suppressed through biaxial compressive strain, leading to the emergence of superconductivity with Tc of 12.2 K and 11.9 K for 1T-WSH (−2 %) and 1T-WSeH (−4 %), respectively. The superconductivity of the above materials originates from the coupling between W-3d electrons and the low-frequency vibrations of W. Interestingly, the 2H–WSeH and 1T-WSeH (−4 %) display nontrivial topological properties, as evidenced by topological invariant Z2 and the presence of edge states. Our research not only provides theoretical guidance for further exploring 2D Janus materials, but also provides ideas for the competition of multiple orders in 2D materials.

Polymer Brushes on Nanoparticles for Controlling the Interaction with Protein-Rich Physiological Media.

The interaction of nanoparticles (NPs) with biological environments triggers the formation of a protein corona (PC), which significantly influences their behavior in vivo. This review explores the evolving understanding of PC formation, focusing on the opportunity for decreasing or suppressing protein-NP interactions by macromolecular engineering of NP shells. The functionalization of NPs with a dense, hydrated polymer brush shell is a powerful strategy for imparting stealth properties in order to elude recognition by the immune system. While poly(ethylene glycol) (PEG) has been extensively used for this purpose, concerns regarding its stability and immunogenicity have prompted the exploration of alternative polymers. The stealth properties of brush shells can be enhanced by tailoring functionalities and structural parameters, including the molar mass, grafting density, and polymer topology. Determining correlations between these parameters and biopassivity has enabled us to obtain polymer-grafted NPs with high colloidal stability and prolonged circulation time in biological media.

Bifonazole caffeate: The first molecular salt of bifonazole with enhanced biopharmaceutical property based on experiments and quantum chemistry research

In order to make novel breakthroughs in molecular salt studies of BCS class-IV antifungal medication bifonazole (BIF), a salification-driven strategy towards ameliorating attributes and aiding augment efficiency is raised. This strategy fully harnesses structural characters together attributes and benefits of caffeic acid (CAF) to concurrently enhance dissolvability and permeability of BIF by introducing the two ingredients into the identical molecular salt lattice through the salification reaction, which, coupled with the aroused potential activity of CAF significantly amplifies the antifungal efficacy of BIF. Guided by this route, the first BIF-organic molecular salt, BIF-CAF, is directionally designed and synthesized with satisfactorily structural characterizations and integrated theoretical and experimental explorations on the pharmaceutical properties. Single-crystal X-ray diffraction resolving confirms that there is a lipid-water amphiphilic sandwich structure constructed by robust charge-assistant hydrogen bonds in the salt crystal, endowing the molecular salt with the potential to enhance both dissolvability and permeability relative to the parent drug, which is validated by experimental evaluations. Remarkably, the comprehensive DFT-based theoretical investigations covering frontier molecular orbital, molecular electrostatic potential, Hirshfeld surface analysis, reduced density gradient, topology, sphericity and planarity analysis strongly support these observations, thereby allowing some positive relationships between macroscopic properties and microstructures of the molecular salt can be made. Intriguingly, the optimal properties, together with the stimulated activity of CAF markedly augment in vitro antifungal ability of the molecular salt, with magnifying inhibition zones and reducing minimum inhibitory concentrations. These findings fill in the gaps on researches of BIF-organic molecular salt, and adequately exemplify the feasibility and validity by integrating theoretical and experimental approaches to resolve BIF’s problems via the salification-driven tactic.

Hydrogen bond analysis of the p-coumaric acid-nicotinamide cocrystal using the DFT and AIM method

Background: The molecular geometric structure of p-coumaric acid-nicotinamide has been optimised using Density Functional Theory (DFT) and Atom In Molecule (AIM). Objective: To analyse the hydrogen bond of the p-coumaric acid–nicotinamide cocrystal. Method: Structural optimisation using DFT was carried out on the basis set B3LYP/6-311G++ (d, p). The electron density topology from the optimisation results obtained was then validated using the Non-Covalent Interaction (NCI) method. Result: Optimisation results showed that there are intermolecular hydrogen bonds in the carbonyl group of p-coumaric acid and the amine group of nicotinamide, namely C1=O11∙∙∙O34 with length 1.804 Å. On the other hand, the results of the topology test with AIM showed a value of ∇2ρ = 0.1196 a.u; G = 0.0393 a.u; H = 0.0946 a.u; V = -0.0488 a.u which means there was an intermolecular Hydrogen bond with EH∙∙∙O = -64.05 a.u. Conclusion: A hydrogen bond in the cocrystal of p-coumaric acid-nicotinamide is classified as an intermolecular hydrogen bond between the carbonyl group of p-coumaric acid and the amine group in the carboxyl group.

The Outstanding Excellences of Interactive Energy Density Topology Change Method

It has not been solved that the fruits, vegetables, strawberries, cells, blood and a bottle of liquor are damaged, broken during transportation. It is the greatest factor in this situation that there is a danger vibration frequency band where these are easy to scratch and are prone to death. If there are eigen frequencies within this danger frequency band, it needs that those eigen frequencies within this danger frequency band are moved out of the band. In the former paper, it was shown difficult to apply the existing topology optimization methods using homogenization method or density method to control plural eigen frequencies for solving this problem. Therefore in the former paper, it was proposed the so called “Interactive Energy Density Topology (IEDT) change method” that is a new high precision and high efficiency method for controlling plural eigen frequencies simultaneously referring to the kinetic and the strain energy density distributions. Here it is discussed more about the IEDT change method and show that it is sometimes difficult for the traditional methods to get solutions because especially in the dynamic problem, eigen frequencies may go up or down depending on its size even if reinforcement or hall for change topology is applied at the same location. But with the proposed IEDT change method, always it can be realized because the proposed method has wider solution spaces than the traditional one. Lastly, it is shown that this IEDT method is also very effective to reduce the integral value of response curve by frequency.

Ordering self-assembly structures via N[sbnd]H⋯S and Br⋯S interactions in (E)-2-(4-bromobenzylidene)hydrazinecarbothioamide : Insights from crystallographic and computational study

In this research paper, the compound (E)-2-(4-bromobenzylidene)hydrazinecarbothioamide (NC2) was synthesized and characterized by spectroscopic techniques and crystal structure was elucidated using single crystal X-ray diffraction method. The Hirshfeld surface analysis revealed the relative contributions of different intermolecular interactions to crystal packing, while the 2D fingerprint plots provided a visual representation of the intermolecular interactions via the surface area corresponding to each type of interaction. The findings revealed that the crystal packing of the molecule is mostly determined by H…H, C-Br…S and NH…S interactions. We investigated the structural and electronic properties of the compound NC2 using density functional theory (DFT). The optimized geometry, total energy, HOMO-LUMO gap, and vibrational spectra were calculated at the ωB97X/6–311+G(d,p) level of theory. The calculated results showed that the molecule has a stable geometry with a trans-conformation. The HOMO-LUMO gap of 3.813 eV indicates that the molecule has moderate stability. The nature of noncovalent interactions are investigated using the methods reduced density gradient (RDG) and topology analysis like quantum theory of atoms in molecules (QTAIM) proposed by Bader et al. The compound NC2 is found to adhere to the Lipinski's rule of five and exhibit good pharmacokinetic properties.

Performance Analysis of Positive Output (P/O) Push-Pull Switched Capacitor Converter for High Power Density Applications

The micro-power-consumption technique requires high power density DC/ DC converters and power supply sources. In this research, a PI and Fuzzy Logic Controllers for an elementary circuit of positive output (P/O) push-pull switched capacitor converter has developed for high power density applications with high sustainability under enormous line and load disturbances. The voltage lift technique is a popular application in electronic circuit design. The power converter performs DC-DC step-up voltage conversion with high efficiency, high power density and cheap topology in a simple structure. The proposed converter combines both switched-capacitor and voltage lift techniques. Referable to the time varying and switching nature of the power electronic converter their dynamic behavior becomes highly nonlinear. Conventional controllers are incapable of providing excellent dynamic performance and hence the fuzzy logic controller can be used as a feed forward controller for controlling power electronic converters. The control algorithm is developed to ensure tracking of the reference voltage and rejection of system disturbances by successive measurements of the converter output voltage at certain time instants within a conduction period. The simulation of PI and Fuzzy logic controls have been carried out using MATLAB/Simulink software to evaluate the controller’s performances. Keywords: Luo converter, DCDC converter, PI Controller, Fuzzy Controller.

On lower density operators

Abstract The classical density topology is an extension of the natural topology on the real line, as the interior of arbitrary Lebesgue measurable set A is contained in the set of density points of A. Also each density point of A belongs to the closure of A for arbitrary measurable set A. In this paper, we concentrate on lower density operators for which the inclusions mentioned above are not fulfilled. In the first part, examples of such lower density operators generated by measure-preserving bijections are given. There are introduced three conditions to investigate lower density operators for which only the second inclusion holds. In the second part, the concept of operator D introduced by K. Kuratowski is applied to the characterization of such operators.

DFT study on the Stereoselectivity of Asymmetric Synthesis of C, N‐Cyclic Azomethine Imines with Allyl Alkyl Ketones

AbstractBased on the density functional theory, the stereoselectivity of the asymmetric synthesis of tetrahydroisoquinolinopyrazole derivatives by the cycloaddition reaction of C, N‐cyclic azomethine imines with allyl alkyl ketones which was catalyzed using a chiral primary amine is studied theoretically. The results demonstrate that the four chiral transition states (TS‐1R2R, TS‐1R2S, TS‐1S2R and TS‐1S2S) are formed by the reaction of dienamine intermediate with C, N‐cyclic azomethine imine, and the reaction barrier of TS‐1R2S is in the lowest level (ΔG=6.98 kcal/mol). The consequence reveal that the 1R2S configuration product is formed by TS‐1R2S transition state. Non‐covalent interaction and electron density topology analysis show that the stereoselectivity of the chiral product is determined through van der Waals forces and hydrogen bond interaction of the transition state molecules.

On density topology using ideals in the space of reals

In this paper we have introduced the notion of I-density topology in the space of reals introducing the notions of upper I-density and lower I-density where I is an ideal of subsets of the set of natural numbers. We have further studied certain separation axioms of this topology.

Planar tetracoordinate beryllium compounds with a partially covalent Be-Ng bond.

An analysis of the thermodynamic and kinetic stability and the nature of the chemical bond in hypercoordinated compounds with the formula BeH3Ng+ (Ng = He-Rn) through high-level calculations is presented in this work. Thermochemical calculations show that, for the heavier noble gases (Ar-Rn), these systems are thermodynamically stable at room temperature; however, this stability decreases due to a weakening of the Be-H2 interaction, while the Be-Ng bond strengthens going down the periodic table. These results are complemented by Born Oppenheimer molecular dynamics simulations, in which the increasing tendency to dissociate the Be-H2 bond is evidenced. The nature of the chemical bonding depends on the analysis performed. On the one hand, the interacting quantum atoms method indicates that the covalent contribution is around 25 to 30%. On the other hand, the electron density topology indicates a covalent nature for compounds with Kr-Rn, while Hirshfeld population analysis in conjunction with Mayer's bond order establishes polar covalent behavior. The geometrical parameters and natural energy decomposition analysis (NEDA) indicate a covalent nature, allowing us to consider that the Be-Ng bond has a partially covalent character.

Heat Dissipation Design Based On Topology Optimization And Auxiliary Materials

Abstract In this paper, a variable density topology optimization method is used to design a high thermal conductivity path structure for efficient heat dissipation. The temperature and stiffness in the module volume are taken as the objective function. Simulations are carried out to compare with a high-power electronics device heat dissipation. The heat dissipation performance (HDP) of structures optimized topologically is further enhanced through the use of auxiliary materials, including highly thermally conductive coating material and phase change material (PCM). The efficient heat dissipation of the constructed topology optimization model and the effectiveness of the proposed method are verified.