Solution Structure Research Articles

Rough Topography and Fast Baroclinic Rossby Waves

AbstractOceanographic observations have revealed that basin‐scale Rossby waves can travel at speeds systematically exceeding values predicted by linear theory based on the flat‐bottom approximation. Using the recently developed parametric “sandpaper” theory of seafloor roughness, we construct a set of analytical solutions for the vertical structure and dispersion relationship of Rossby waves. We then use simulations to confirm these results and show that baroclinic Rossby waves can be accelerated by irregular small‐scale rough topography by up to a factor of 1.6 relative to their flat‐bottom counterparts. This acceleration is most extreme at high latitudes and wavelengths of approximately 600 km. Our investigation demonstrates the importance of relatively small‐scale processes for the large‐scale flow dynamics in general and baroclinic Rossby waves in particular.

Synthesis of Arsenocholine-Type Polycation Brush and Its Hydration Structure in Aqueous Solution

Synthesis of Arsenocholine-Type Polycation Brush and Its Hydration Structure in Aqueous Solution

Effect of Superstoichiometric Bismuth Addition on the Structure and Dielectric Characteristics of the Solid Solutions (1−x)BiFeO3-xBaTiO3

Ceramic samples of solid solutions of the binary system (1−x)BiFeO3-xBaTiO3 + 2 wt.% Bi2O3 (0.29 ≤ x ≤ 0.33, Δx = 0.01) were prepared using the conventional solid-phase reaction method with and without mechanical activation. Using X-ray studies, it was found that the objects have a pseudocubic crystal structure, and limited solubility occurs in solid solutions of the studied composition, as evidenced by the presence of regions with an increased Bi or Ba content and similar cell parameters. A diffuse phase transition occurred from the FE to PE state in the temperature ranges of (650–850) K. Relaxor-like behavior and the smearing of the phase transition in the studied ceramics can be associated with the presence of non-interacting regions with an increased content of Bi or Ba, different modulation, and crystal lattice symmetry. The grain morphology and dielectric characteristics of the selected solid solutions were investigated. The highest piezoelectric coefficient, d33 = 120 pC/N, was obtained in the mechanically activated ceramics 0.71BiFeO3-0.29BaTiO3 + 2 wt.% Bi2O3.

Near-Surface Concentration Profile of Sheared Semidilute Polymer Solutions.

Controlling the structure of polymer solutions near a solid surface is crucial for many industrial processes as it significantly impacts solution flow and influences slip at the interface. To date, only a few techniques have been developed to experimentally investigate this type of interface at the nanometric scale of solid/liquid interactions. In this study, we probe the interface between a smooth sapphire surface and a semidilute polystyrene solution, using neutron reflectivity. A special setup for flow measurements under shear has been designed and optimized. Our results show that, at rest, polymer chains are globally depleted from the solid surface. Contrary to common assumptions, some polystyrene chains do adsorb onto the wall. Under flow conditions, we experimentally demonstrate that the depletion layer remains stable, a finding that has been hypothesized but is only vaguely confirmed in the literature.

Optimizing UHPC Layers to Improve Punching Shear Performance in Concrete Slabs

Flat slabs supported by columns without beams are widely used in construction owing to their economy and efficiency. However, brittle punching shear failure at slab–column connections can cause progressive collapse. UHPC has a higher tensile strength than NSC and, when appropriately reinforced with steel fibers, exhibits strain hardening after initial cracking. These properties make Ultra-High-Performance Concrete (UHPC) ideal for durable, thin, low-cost bridge decking and heavily loaded elements and an excellent choice for improving slab–column connections that have experienced punched shear failure. This study explores the impact of UHPC layers on the punching shear behavior of reinforced concrete slabs. Sixteen slab specimens were tested with variations in UHPC layer thickness, placement, and column shape. Results demonstrate that incorporating UHPC layers significantly enhances punching shear resistance, increasing ultimate load capacity by 27–91% compared to reference specimens. Notably, thicker UHPC layers (75 mm) and bottom-placed layers exhibited superior performance in terms of ductility and toughness. Square columns outperformed circular ones in resisting punching shear. Additionally, thicker layers reduced initial stiffness, while debonding issues in 25 mm layers adversely affected structural performance. This research provides valuable insights for optimizing UHPC configurations to improve the punching shear resistance of concrete slabs, offering promising solutions for high-load structures in modern construction.

Elucidating on the Quaternary Structure of Viper Venom Phospholipase A2 Enzymes in Aqueous Solution.

This study focuses on the quaternary structure of the viper-secreted phospholipase A2 (PLA2), a central toxin in viper envenomation. PLA2 enzymes catalyse the hydrolysis of the sn-2 ester bond of membrane phospholipids. Small-molecule inhibitors that act as snakebite antidotes, such as varespladib, are currently in clinical trials. These inhibitors likely bind to the enzyme in the aqueous cytosol prior to membrane-binding. Thus, understanding its controversial solution structure is key for drug design. Crystal structures of PLA2 in the PDB show at least four different dimeric conformations, the most well-known being "extended" and "compact". This variability among enzymes with >50% sequence identity raises questions about their transferability to aqueous solution. Therefore, we performed extensive molecular dynamics (MD) simulations of several PLA2 enzymes in water to determine their quaternary structure under physiological conditions. The MD simulations strongly indicate that PLA2 enzymes adopt a "semi-compact" conformation in cytosol, a hybrid between extended and compact conformations. To our knowledge, this is the first study that determines the most favorable dimeric conformation of PLA2 enzymes in solution, providing a basis for advancements in snakebite envenoming treatment. Recognizing snakebite envenoming as a neglected tropical disease has driven the search for efficient, affordable alternatives to the current antivenoms. Therefore, understanding the main drug targets within snake venom is crucial to this achievement.

Cost-Effective RuNi Solid Solutions Prepared by Electrodeposition for Efficient Alkaline Hydrogen Evolution.

The development of efficient hydrogen evolution reaction (HER) catalysts is crucial for water electrolysis. Currently, Ru-based catalysts are considered top contenders, but issues with stability, activity, and cost remain. In this work, RuNi alloys possessing a solid solution structure within the Ru lattice are prepared via straightforward electrodeposition on various substrates and assessed as HER catalysts in alkaline media. A RuNi solid solution containing 9.8 at. % Ni deposited on Ti substrate, wherein the Ni content greatly surpasses the solubility limit of Ni in Ru at room temperature, exhibits a considerably low overpotential of 28mV at a current density of 10mA cm- 2, along with good long-term stability (less than 100mV increase in overpotential after 600 h). The enhancement in HER performance results from the increased electron density around Ru atoms due to Ni coordination, which facilitates the desorption of H* from the catalyst surface to produce H2. Concurrently, incorporating Ni reduces the Ru usage, rendering the RuNi alloy a viable cost-effective HER catalyst for practical applications.

Toward mitigating the impact of non-bulk defects on describing water structure in salt aqueous solutions: Characterizing solution density with a network-based structural indicator.

Structural indicators, also known as structural descriptors, including order parameters, have been proposed to quantify the structural properties of water to account for its anomalous behaviors. However, these indicators, mainly designed for bulk water, are not naturally transferrable to the vicinity of ions due to disruptions in the immediate neighboring space and a resulting loss of feature completeness. To address these non-bulk defects, we introduced a structural indicator that draws on the concept of clique number from graph theory and the criterion in agglomerative clustering, denoted as the average cluster number. This structural indicator aims to discern intrinsic structural characteristics within the water molecules regardless of the ions occupying the neighboring space, without requiring additional corrections. From molecular dynamics simulation results for neat water and salt aqueous solutions utilizing the TIP4P/2005 water model and the Madrid-2019 force field, we characterized the variations in densities with temperature using this network-based indicator, thereby demonstrating its practical utility. The findings suggest that at lower temperatures, the addition of ions disrupts the intrinsic structure of water molecules, with this effect diminishing as the temperature rises. Cations with larger charge density tend to induce stronger disruptions. This study highlights the importance of mitigating the impact of non-bulk defects before applying the indicators to analyze water's intrinsic structural properties in solutions. By doing so, the relationship between changes in water structure and solution behaviors can be more accurately assessed.

NMR study of the interaction between MinC and FtsZ and modeling of the FtsZ:MinC complex.

The Min system is a key spatial regulator of cell division in rod-shaped bacteria and the first FtsZ negative modulator to be recognized. Nevertheless, despite extensive genetic and in vitro studies, the molecular mechanism used by MinC to inhibit Z-ring formation remains incompletely understood. The crystallization of FtsZ in complex with other negative regulators such as SulA and MciZ has provided important structural information to corroborate in vitro experiments and establish the mechanism of Z-ring antagonism by these modulators. However, MinC and FtsZ have so far eluded co-crystallization, probably because their complex is too unstable to be crystallized. To gain structural insight into the mechanism of action of MinC, we determined the solution structure of the N-terminal domain of B. subtilis MinC, and through NMR titration experiments and mutagenesis identified the binding interfaces involved in the MinCN-FtsZ interaction. By using our experimental results as restraints in docking, we also constructed a molecular model for the FtsZ:MinCN complex and validated it by molecular dynamics. The model shows that MinCN binding overlaps with the FtsZ polymerization interface on the C-terminal globular subdomain of FtsZ and, thus, provides a structural basis for MinCN inhibition of FtsZ filament formation. Given that the C-terminal polymerization interface of FtsZ corresponds to the plus end of FtsZ filaments, we propose that capping is the main mechanism employed by MinC to antagonize FtsZ polymerization.

Comprehensive Rehabilitation of the Punta del Este Shopping Center After Fire Damage

On 6 August 2022, a fire devastated 80% of the Punta del Este Shopping Center in Maldonado, Uruguay. Originating in the kitchen of a supermarket, the fire ravaged the shopping center for 72 h before being brought under control. This article outlines the studies conducted to assess the fire’s impact on the building’s structure, as well as the strategies and rehabilitation project aimed at ensuring its stability and performance. An in-depth analysis of the concrete, reinforcements, and foundations was carried out using destructive and non-destructive testing. In total, over 150 concrete samples were collected for analysis, and the foundations were studied using indirect methods. Based on these analyses, actions were planned for each area, including structural repairs, reinforcements, or demolition. Due to the tight deadline for resuming commercial activity, special innovative structural solutions were designed to rehabilitate large severely damaged areas with the specific feature of avoiding demolition. This involved altering the static scheme of the structure, incorporating reinforcements and using slabs of the damaged structure as formworks. Complete demolition and subsequent reconstruction would have required timelines incompatible with the clients’ expectations, while the adopted solutions enabled the project to meet its objectives.

Microwave-Assisted Synthesis of Platinum-free High-Entropy Alloy Catalysts on Reduced Graphene Oxide Sheets for Enhanced Oxygen Reduction and Evolution Reactions.

Nano-sized high-entropy materials (HEMs) recently received more attention to researchers due to their superior electrochemical catalytic properties. HEMs comprise at least five elements with or without metals and are synthesized through solid-state reactions and solution-mediated techniques. The presence of many elements in these HEMs result in a high mixing entropy and facilitates the formation of stable solid solutions in fundamental crystal structures. Herein, Pt-free high-entropy alloys (HEAs) were synthesized through facile and straightforward pulse microwave (PM) synthesis technique, which serve as efficient electrochemical catalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The PM synthesis method was conducted at an extremely low temperature (100 °C) without any external catalytic reagents. Using this PM technique, Cr18.2Zr13.5Ti5.3Co17.8Ni8.4Cu8.5Fe28.3 and Al15.3Mn18.2Ti3.7Co23.2Ni5.9Cu5.9Fe27.8 HEAs catalysts were synthesized with superior catalytic activity towards OER and ORR and compare its activities with pure Pt catalysts. The as-prepared HEAs also display an anti-CO poisoning effect and long-term durability, as compared to pure Pt catalysts. The low-temperature PM approach not only confirms the feasibility of synthesis of noble metal-free HEAs but also validates their superior catalytic activity towards OER and ORR, which is beneficial for the development of proton exchange membrane fuel cells and proton exchange membrane water electrolysis.

Bayesian Learning Based Elitist Nondominated Sorting Algorithm for a Kind of Multi-objective Integrated Production Scheduling and Transportation Problem

This paper focuses on a kind of multi-objective integrated production scheduling and transportation problem (MIPSTP), which is encountered in many real-life industrial processes. MIPSTP contains a production stage for processing products and a transportation stage for transporting products. In MIPSTP, we consider a dedicated integration of distributed scheduling and transportation regarding the two stages, arising from a practical project for a cooperative iron and steel company. The objective of MIPSTP is to minimize the total completion time of each factory and total transportation cost. To solve the problem, a Bayesian learning-based elitist nondominated sorting algorithm (BLENSA) is proposed. The primary highlights of this work are two-fold: 1) new solution structures of MIPSTP and 2) novel search model of BLENSA. For the solution structures, we propose for the first time the mathematical description of MIPSTP, accounting for several features in applications and so is different from conventional scheduling problems. For the search model of BLENSA, we propose a Bayesian learning-based probability model to learn valuable knowledge about nondominated solutions. Thereby, BLENSA combines the Bayesian learning-based probability model to produce a candidate population (CP) and the nondominated sorting method to generate a main population (MP). Next, we propose a greedy competition strategy to construct MP from CP and MP for the next generation. Results of experiments on 57 test instances and a real-life case study demonstrate the effectiveness and practical values of BLENSA.

Synthesis, Characterization, FT-IR and UV-Vis of a Novel (E)-3-(5-bromo-3-fluoro-2-hydroxybenzilide amino)benzaldehyde of Compound

One of the most studied compound families in the field of crystallography is the Schiff-based compounds. The basis of this research article is a newly synthesized Schiff-base compound. This research aims to investigate the synthesized (E)-3-(5-bromo-3-fluoro-2-hydroxybenzilide amino)benzaldehyde phenol compound using experimental methods. FT-IR, UV-Vis and X-ray diffraction methods were used to elucidate the structural properties of the compound synthesized at the end of chemical processes. The structure solution was carried out from the data obtained as a result of X-ray analysis. According to these results, a molecule was formed in the asymmetric cell.The resulting structure has shaped in enol-imine form. The number of molecules in the unit cell was also determined as 4 (Z=4). According to the results obtained as a result of UV-Vis spectroscopy, the structure revealed that the enol-imine form was dominant. The reasons for this situation were explained.

When can we trust structural models derived from pair distribution function measurements?

The pair distribution function (PDF) is an important metric for characterising structure in complex materials, but it is well known that meaningfully different structural models can sometimes give rise to equivalent PDFs. In this paper, we discuss the use of model likelihoods as a general approach for discriminating between such homometric structure solutions. Drawing on two main case studies-one concerning the structure of a small peptide and the other amorphous calcium carbonate-we show how consideration of model likelihood can help drive robust structure solution, even in cases where the PDF is particularly information-poor. The obvious thread of these individual case studies is the potential role for machine-learning approaches to help guide structure determination from the PDF, and our paper finishes with some forward-looking discussion along these lines.

Solutions of stochastic excited structures with inerter systems in closed-form considering physical mass and mass amplifying factors

Solutions of stochastic excited structures with inerter systems in closed-form considering physical mass and mass amplifying factors

Unveiling the Darknet: An Analysis of its Structure, Challenges, and Potential Solutions.

Unveiling the Darknet: An Analysis of its Structure, Challenges, and Potential Solutions.

Genome mining and heterologous expression reveal streptacidin, a new lasso peptide from Streptacidiphilus jiangxiensis.

A lasso peptide biosynthetic gene cluster (BGC) was identified through genome mining in the species Streptacidiphilus jiangxiensis CGMCC 4.1857, which was isolated from acidic rhizosphere soil. The BGC was reconstructed in Escherichia coli, leading to the heterologous production of a lasso peptide named streptacidin. The solution structure of streptacidin was determined based on the distance constraints derived from the NOESY spectrum, establishing the first lasso peptide utilizing methionine as a steric lock for the unique spatial configuration and the remarkable stability against heat (up to 95 °C) and proteolytic degradation by carboxypeptidase Y and chymotrypsin. Under experimental conditions, streptacidin showed weak effectiveness against vancomycin sensitive Enterococcus faecalis ATCC 29212 and Pseudomonas aeruginosa ATCC 902. These findings further the understanding of this distinctive class of compounds.

ANALYSIS OF RELATED PHYSICAL AND MECHANICAL PROCESSES AND STATES AND SYNTHESIS METHODS OF DESIGN AND TECHNOLOGICAL SOLUTIONS OF ARMORED COMBAT VEHICLES ELEMENTS

Existing research methods of contact interaction and stress-strain state of complex structural elements are analyzed. The main elements of hydraulic transmissions in tank transmissions are ball pistons that are connected to the toroidal running surface of the stator ring. Important parameters of these elements are the ratio of the radii of the piston and the cross-section of the running track. The studied regularities indicate the optimal range of radii ratios, which ensures minimum contact pressure and stress. Taking into account the elastic-plastic deformation of the materials of the contacting parts, in particular the surface layers, is important for recommendatory decisions. Patterns of influence on the characteristics of strength and performance of the investigated structures of varied parameters have been revealed. Accordingly, in each specific case, it is possible to develop recommendations for the justification of progressive technical solutions of certain structures according to the mentioned criteria. Ball pistons in connection with the toroidal running surface of the stator ring are decisive for strength and durability of the hydraulic transmission elements of promising tank transmissions. In particular, important parameters are the radii ratio of the piston, on the one hand, and on the other, of the cross section of the treadmill. Despite the traditionally existing approaches and efforts to bring the shapes of the contacting surfaces of conjugated bodies as close as possible, the work established regularities that contradict such solutions.

МЕТОДИКА ОБОСНОВАНИЯ ХАРАКТЕРИСТИК ТЕПЛОИЗОЛЯЦИОННОГО МАТЕРИАЛА В СОСТАВЕ ОГРАЖДАЮЩЕЙ КОНСТРУКЦИИ С ИСПОЛЬЗОВАНИЕМ СРЕДСТВ КВАДРАТИЧНОГО ПРОГРАММИРОВАНИЯ

Abstract: Relevance of the research is connected to the importance of the problems related to the determination of the characteristics for structural solutions used in the construction or reconstruction of buildings and structures (taking into account the indicators of energy and economic efficiency), as well as the relatively low practical significance of the relevant scientific developments. Problem statement. It is necessary to determine the most preferred variant (model) of heat-insulating material used as an additional layer in the wall structure on the basis of the criteria related to the provided heat transfer resistance and the payback period of the corresponding design solution. Research aim. Development of tools for determination of the characteristics for thermal insulation material as part of wall structure within a residential building. Research tasks are the following: 1. Review and comparative analysis of scientific developments in the field of research. 2. Development of the procedure for determination of the characteristics for the heat-insulating material as part of the wall structure with the use of quadratic optimization tools. 3. Implementation of the developed procedure on a practical example. Results. Procedure for determination of the characteristics for the heat-insulating material as part of the wall structure with the use of quadratic optimization tools has been developed. The procedure has been implemented using a practical example, and the received results have been analyzed. Findings. The results of the procedure’s implementation on a practical example confirm the high practical significance of the developed tool. Thus, quadratic optimization tools can be effectively used to solve the problem related to the determination of the characteristics for heat-insulating material as part of an wall structure.

DFT Calculations of 1H and 13C NMR Chemical Shifts of Hydroxy Secondary Oxidation Products of Geometric Isomers of Conjugated Linoleic Acid Methyl Esters: Structures in Solution and Revision of NMR Assignments.

Detailed DFT studies of 1H and 13C NMR chemical shifts of hydroxy secondary oxidation products of various geometric isomers of conjugated linolenic acids methyl esters are presented. Several low energy conformers were identified for model compounds of the central dienenol OH moiety, which were found to be practically independent on the various functionals and basis sets used. This greatly facilitated the minimization process of the geometric isomers of conjugated linolenic acids methyl esters. Several regularities of the literature experimental 1H and 13C chemical shifts were reproduced very accurately with the computational chemical shifts of the Gibbs low energy DFT optimized conformers, after a Boltzmann analysis. δ(13C) and δ(1H) of the methine CH-OH group are highly diagnostic for the trans/trans and cis/trans geometric isomerism of the adjacent double bond. δ(13C) of the -CH2- group adjacent to the terminal double bond of the conjugated system strongly depend on the cis/trans geometric isomerism of this bond and, thus, could be of importance in structural analysis. Ambiguities in the reported literature resonance assignments of olefinic carbons had been resolved. Computational δ(1H) and δ(13C) can be utilized for the identification of geometric isomerism and structural and conformational elucidation of hydroxy derivatives of conjugated linoleic acids and their ester derivatives.