Synthesis, multidimensional characterization, biological evaluation, and computational insights into novel N2O2-tetradentate Schiff base metal complexes as potent antimicrobial agents

The reduction of carboxylic acid derivatives to alcohols and amines ranks among the most fundamental transformations in synthetic chemistry, with molecular hydrogen offering an atom-economical and sustainable approach to access these valuable products. While these reactions have traditionally relied on noble metal catalysts, the past decade has witnessed remarkable progress in the development of earth-abundant 3d transition metal alternatives. This review surveys recent advances in homogeneous manganese, iron, and cobalt catalysis for the hydrogenation of esters, amides, and nitriles. Special emphasis is placed on ligand design strategies, ranging from classical pincer architectures featuring metal-ligand cooperation to emerging N-heterocyclic carbene and non-pincer frameworks. For each metal, we discuss the evolution of catalytic systems, their substrate scope, and operational characteristics. Mechanistic aspects are examined in detail, revealing diverse activation modes including outer-sphere and inner-sphere pathways, aromatization-dearomatization processes, and Lewis acid-base cooperativity. The review highlights how increasing electron density at the metal center through ligand modification enhances hydride donor ability and catalytic activity. Recent breakthroughs in polyester depolymerization and challenging substrate classes demonstrate the potential of these base metal catalysts for circular economy applications. This comprehensive overview provides a foundation for future catalyst development and mechanistic investigation in this rapidly evolving field. • Comprehensive review on manganese, iron and cobalt catalysts for hydrogenation of esters, amides and nitriles • Mechanistic analysis reveals diverse pathways beyond classical MLC cooperativity • Recent advances enable polyester depolymerization for circular economy applications

• BS7910 FCGR for R < 0.5 is up to 3.6 × over-conservative for S355 in free corrosion. • Removing this conservatism could improve remaining life by 109%. • For the investigated database, statistical weighting had a negligible impact. • HAZ data fit a bilinear curve more closely, while BM data fit a linear one. • S355J2 + N subgrade displayed the highest FCGR, while S355G10 + M showed the lowest. The recommendations for fatigue crack growth rate (FCGR) in British Standard BS 7910 are based on experimental data which are multiple decades old, and the FCGR laws were constructed using data from multiple structural steel grades. The present study sought to gather more recent FCGR data for S355 steel in a marine free-corrosion environment, which can be applied for use in offshore wind turbine structural integrity life prediction. The collected data were filtered to include only valid Stage II (Paris region) data in the analyses. A method for fitting a bilinear regression curve was developed along with bias reducing weighted regression methods. The resulting bilinear trend shows up to 3.6 times lower FCGR relative to the BS 7910 recommendations for the free-corrosion environment. The analysed S355 data indicated that a bilinear fit best described the FCGR in the heat affected zone, whereas a simple linear fit was appropriate for the base metal. The S355 subgrades, J2 + N, G8 + M and G10 + M, presented considerable variance in mean FCGR, with J2 + N having the highest FCGR and G10 + M the lowest. When considered in the context of offshore wind turbine service life, the overall S355 FCGR reduction relative to the BS 7910 free corrosion curve results in a just over double life expectancy for a 4 × 20 mm surface semi-elliptical flaw size, based on the conservative upper bound analysis. This increase in life could prove invaluable for corrosion protection system repair timescales, considering the need to carefully plan the maintenance time window to avoid adverse weather conditions.

This study investigates the feasibility of using Acidithiobacillus ferrooxidans for the bioleaching of metals from printed circuit boards (PCBs) of scrap mobile phones at varying pulp densities (0.5%, 1%, 1.5%, and 2% w/v). While the effectiveness of A. ferrooxidans in recovering base metals from low-grade ores is welldocumented, its application in electronic waste (e-waste) recycling remains underexplored. The present work aims to assess the organism’s potential for mobilizing key base metals such as copper, nickel, and zinc from urban waste matrices under different pulp density conditions. Statistical analysis, including Analysis of Variance (ANOVA) and F-tests, revealed a significant difference in metal recovery rates across pulp densities, with the highest bioleaching efficiency observed at 1% (w/v). These findings demonstrate the practical potential of bioleaching as a sustainable and low-impact strategy for metal recovery from e-waste, contributing to environmentally sound waste management practices and resource recovery.

This study investigates geometric dimensions of the weld bead produced by gas metal arc surfacing with a consumable electrode. Standard surfacing is characterized by low productivity because of the significant number of runs and the need for machining tall beads. Deep penetration causes a significant proportion of the base metal in the surfaced layer and inhomogeneity of the chemical composition. Existing approaches to controlling the geometry of the weld bead (pulsed arc modes, electrode oscillations, electromagnetic arc control) have a limited effect on the width or complicate the design of the welding head. This work considers gas metal arc surfacing with controlled low-frequency oscillations of the workpiece with a liquid weld pool. The installation is built on an adjustable electric drive with a stepper motor with a programmable setting of the frequency and amplitude of oscillations. These parameters, together with energy parameters and speed, affect the geometric dimensions of the weld bead and the mechanical properties of the surfaced metal. The width, height, and depth of the weld bead penetration were determined from macrographic cross-sections. A mathematical model of bead geometry as a function of surfacing parameters has been built by using experimental data regression analysis. The errors in predicting the width and height did not exceed 21.7% and 15%, respectively, thereby confirming its practical applicability. Controlled oscillations were found to increase bead width by a factor of 1.5–2 and reduce bead height by up to a factor of 6 compared with vibration-free surfacing. This is attributed to redistribution of thermal energy and intensification of horizontal melt flows. Changing the weld bead geometry increases surfacing productivity and control accuracy. The method is suitable for use in adaptive welding systems

Abstract Gold, silver, and copper heap leach metal processing is widespread in Nevada, one of the world’s most productive mining regions. Decades of large-scale operations have generated extensive inventories of leached tailings that retain significant quantities of unrecovered base, precious, and critical metals due to the selective nature of heap-leach extraction. This study compiles a comprehensive statewide inventory of active and inactive heap-leach sites and estimates the remaining recoverable metal endowment within these materials. Our analysis indicates that Nevada’s leached tailings contain approximately $88 billion United States Dollars in precious metals and &gt;$15 billion United States Dollars in critical metals at current market prices. Reprocessing these materials could meet or exceed annual United States demand for several critical metals while mitigating environmental liabilities at legacy waste sites. As global demand grows amid supply-chain vulnerabilities, tailings reprocessing represents a promising opportunity to strengthen domestic resource security and advance sustainable mining strategies.

In the automotive industry, ultrasonic welding (USW) stands out as a highly effective solid-state welding technique. It is specifically designed for joining components within lithium-ion battery modules and energy storage systems. To achieve an optimal weight-to-body ratio, dissimilar materials like aluminum, copper, and nickel are joined to reduce the weight of electrical and electronic devices. This study presents a systematic analysis of aluminum (Al) and cupro-nickel (CuNi) dissimilar joints using USW, with variations in welding parameters. The lap shear strength results show that sonotrode pressure and welding energy have a greater impact on joint strength than the amplitude of vibration at all tested levels. Joint strength reached peak values of 942N and 236N, respectively, before declining sharply as weld energy increased due to the high interfacial temperature. Resistance measurements revealed that resistance decreased with increasing welding energy. Additionally, Al-CuNi specimens exhibited higher hardness values at the faying surface compared to their base metals. A metallographic analysis of the weld cross-section was conducted to evaluate diffusion across the joint interface, supported by X-ray energy-dispersive spectroscopy, electron backscatter diffraction, and X-ray diffraction to assess weld quality.

Abstract Stress corrosion cracking (SCC) of stainless-steel welds in chloride-containing environments remains a major concern in structural and process industries. Although Activated Tungsten Inert Gas (A-TIG) welding has been widely investigated for improving weld penetration and mechanical properties, comparative assessment of SCC behaviour of flux-assisted A-TIG welded AISI 304L stainless steel remains limited. This study investigates the SCC response of AISI 304L stainless steel welds fabricated using conventional TIG (C-TIG) and A-TIG welding employing SiO 2 , TiO 2 , and Cr 2 O 3 activating fluxes under chloride environments. SCC susceptibility was evaluated using Slow Strain Rate Testing (SSRT) in air and 3.5 wt.% NaCl solution. Mechanical degradation behaviour, time-to-failure response, fracture morphology, and localized compositional variations were comparatively assessed. Chloride exposure reduced the mechanical performance of all weld conditions. Among the investigated welds, TiO 2 -assisted A-TIG exhibited the most favourable SCC resistance, achieving a time-to-failure of 115 min compared with 98 min for the C-TIG weld. The SCC susceptibility indices further revealed lower degradation in strength and ductility for TiO 2 -assisted welds (Iσ ≈ 4.18% and Iε ≈ 10.82%) than for C-TIG welds (Iσ ≈ 15.96% and Iε ≈ 28.19%). Fractographic analysis also indicated comparatively reduced crack propagation in TiO 2 -assisted welds. The SCC resistance trend under the investigated conditions was established as TiO 2 A-TIG &gt; Base Metal &gt; Cr 2 O 3 A-TIG &gt; SiO 2 A-TIG &gt; C-TIG. The study provides a direct comparative assessment and performance-based ranking of activating fluxes with respect to SCC behaviour of AISI 304L stainless steel welds exposed to chloride environments.

This paper presents the structural design and supporting analysis for the Microreactor Applications Research Validation and Evaluation (MARVEL) primary coolant system (PCS) using the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code Section III, Division 5, rules. MARVEL is a liquid metal–cooled microreactor intended to provide experimental capabilities for the rapid testing and development of microreactor technologies. The PCS utilizes high-temperature sodium-potassium liquid metal as the primary coolant and operates at a design temperature of 570°C, necessitating the consideration of creep-related failure mechanisms. The base metal for the PCS is 316H stainless steel, and the weldments are made with a 16-8-2 filler. The design approach incorporates the current base code rules along with ASME code cases N-924, N-861, and N-862 to address primary load, ratcheting, and creep-fatigue evaluations, respectively. The reactor’s operation involves complex thermal and mechanical interactions due to natural convective flow and differential thermal expansion between components. This paper discusses the structural engineering challenges encountered, such as managing thermal stresses in the distribution plenum and guard vessel, and outlines the strategies implemented to meet the code requirements, including design modifications and operational constraints.

Nanoparticles of uranium and rare earth elements in polymetallic mine waste.

As multilayer ceramic capacitors continue to evolve toward thinner dielectric layers and lower cost, the development of barium titanate powders combining nano-scale particle size with reduction resistance has become a critical industry demand. In this paper, BT-xOH nano-powders with different hydroxyl defect contents were prepared by the sol–gel–hydrothermal method through adjusting the concentration of the mineralizer KOH, and the regulation mechanism of hydroxyl defects on the reduction resistance of barium titanate ceramics was systematically investigated. The research shows that for BT-xOH ceramics sintered under a reducing atmosphere, hydroxyl defects are converted into oxygen vacancies, disrupting the long-range order of ferroelectric domains and associating with barium vacancies to form [VBa‘’-VO..] defect dipoles. These dipoles, in coordination with the increase in grain boundary density, enhance the charge carrier migration barrier and the suppression of oxygen vacancies and electronic conductivity by the grain boundary space charge layer, resulting in a resistivity on the order of 1011 Ω·cm under a reducing atmosphere. Meanwhile, oxygen vacancies generate a pinning effect at grain boundaries, achieving the effect of inhibiting grain growth. This study reveals the microscopic mechanism by which the reduction resistance is enhanced through the regulation of intrinsic hydroxyl defects in the powder, providing a new technical pathway for dielectric materials used in high-performance base metal electrode MLCCs.

A nickel-catalyzed direct tetra-alkynylation at the B(3,4,5,6) positions of o-carboranes has been developed using a bidentate directing group strategy. This method delivers B(3,4,5,6)-tetra-alkynylated o-carborane derivatives in high yields. By employing a base metal catalyst in an oxidant-free process, this approach offers a more sustainable, cost-effective, and environmentally benign alternative for synthesizing polyalkynylated o-carboranes.

RETRACTION: Schiff Base Metal Derivatives Enhance the Expression of HSP70 and Suppress BAX Proteins in Prevention of Acute Gastric Lesion

ABSTRACT Aluminium composites having applications extensively in all sectors owing to their excellent strength-to-weight ratio, high thermal conductivity and inherent corrosion resistance. Nevertheless, incorporating reinforcements to improve mechanical properties can significantly influence the corrosion characteristics of the base metal. The electrochemical studies focus on evaluating the corrosion behaviour of different aluminium matrix composites (AMCs) synthesised with varying beryl compositions (6%, 8%, 10%, 12%) in 0.1 M NaCl at different temperatures. Potentiodynamic polarisation (PDP) results indicate that an increase in the concentration of beryl decreased the corrosion rate till 8%. Morphological studies supported the above results showing minimum roughness for 8% beryl with respect to 0% beryl composite, supporting the EIS and PDP studies. The Monte Carlo (MC) results show that higher adsorption energies (more negative values) indicate that beryl is better able to create a stable, protective layer on the AlBeCe composite surface, which improves corrosion resistance.

Friction stir welding (FSW) has recently intrigued academics’ interest due to advances in high strength, low heat generation, tiny grain size, no melting, and the ability to produce dissimilar welding. It created a weld joint by stirring and applying stress to the interface of two metallic plates with a high-hardness tool. The impact of tool pin geometries during the stirring process and the existence of the friction stir welding tool are typically disregarded, particularly in molecular dynamics (MD) simulations, despite a large number of earlier reports. Therefore, in this report, the dissimilar welding joint of Mg-Al by friction stir welding (FSW) is investigated via MD simulation. The effects of travel speed, rotation speed of the tool, and tool pin geometry on the formation of Mg-Al weld joints are examined. The results indicate that Al atoms mix more effectively in the Mg plate than Mg atoms do in the Al plate. Improving the travel speed from 500 to 2000 m/s leads to a more severe atomic strain distribution, leading to a high-temperature zone up to 1000 K and an amorphous fraction of 18.8%. Moreover, the plastic deformation and high-temperature zone tend to become greater when the rotation speed increases. The mechanical atomic mixing level fluctuates with rotation speed, reaching a maximum value at 12 rad/ps. Rotating at 12 rad/ps also leads to the highest levels of mechanical atomic mixing and amorphous atoms. Considering the tool pin geometry, the rectangular prism and cone geometries gain a higher level of heating. The triangular and tube geometries create a better stirring effect. The results enhance atomic-level understanding of the mechanics of the FSW process. The following studies should evaluate the influence of offset distance and tool angle on the material flow of base metals.

Low-temperature Co-Fired Ceramics necessitate low sintering temperatures to enable cofiring with base metals, while dielectric resonator antennas demand temperature-stable dielectric properties; hexagonal perovskite Ba12Zn0.5Zr0.5Nb9O36 (R3̅m) ceramics exhibit excellent microwave dielectric performance but suffer from a high sintering temperature (1475 °C) and undesirably high temperature coefficient of resonant frequency (τf = 26.4 ppm/°C), limiting their practical applications. A synergistic strategy overcomes these critical bottlenecks by integrating BaWO4 (I41/a) for precise τf tuning and BaCu(B4O8) as a sintering aid to enable low-temperature sintering. XRD Rietveld refinement confirms the composites consist exclusively of impurity-free Ba12Zn0.5Zr0.5Nb9O36 and BaWO4 phases, and Raman spectroscopy validates the characteristic vibrational modes of NbO6 octahedra and [WO4]2- groups. The optimal composite at x = 0.89 exhibits exceptional all-around microwave dielectric properties (εr = 19.0, Q × f = 30100 GHz, τf = 3.0 ppm/°C) when sintered at 1000 °C, coupled with excellent chemical compatibility with Cu electrodes during cofiring. The DRA based on this composite delivers a broad 375 MHz bandwidth, 5.13 dBi gain, and 97.17% radiation efficiency at 9.14 GHz, highlighting its great potential for LTCC technology and microwave communication applications.

Synthesis and multi-target biological evaluation of Schiff base metal complexes: tuning anticancer efficacy and enzyme inhibition via metal center variation.

ABSTRACT Cold metal transfer (CMT) welding of Ti-6Al-4V sheets was carried out at different welding conditions, e.g. welding current, welding voltage and welding speed. It was observed that the weld pool size increased as a function of heat input during welding. The base metal (BM) had near equiaxed grains of α with insignificant amount (∼ 2%) of β at the boundaries of α grains. However, the fusion zone (FZ) and heat-affected zone (HAZ) consisted of predominantly α and α′ grains. The FZ exhibited the highest micro-hardness and residual stress values as compared to the HAZ and BM regions. The residual stress values of the welds were found to be compressive in nature and they decreased as a function of heat inputs of the welding. The welded samples had higher tensile strengths as well as ductility as compared to the sample before welding. Further, the strength and ductility of the welded samples were found to decrease with increasing the heat input of the welding. Similarly, the welded sample exhibited a lower corrosion rate and superior biocompatibility as compared to the base metal.

In this study, three new Ni(II) complexes, namely, [Ni(C16H13Cl2NO3)(C10H8N2)]·H2O·2CH3OH (C1), [Ni(C16H13Cl2NO3)]·3H2O·CH3OH (C2), and [Ni(C16H13Cl2NO3)(C10H8N2)]·1.5H2O (C3), were synthesized using chlorinated Schiff base ligands derived from the condensation of 3,5-dichlorosalicylaldehyde with L/D-phenylalanine, combined with Ni2+ ions and 2,2'-bipyridine as a co-ligand (for C1 and C3). All complexes C1-C3 were characterized by single-crystal X-ray diffraction and elemental analysis. This study systematically investigates the influence of co-ligands (2,2'-bipyridine vs. solvent molecules) and amino acid configurations (L-vs.D-phenylalanine) on the structural stability and urease inhibitory activity of the complexes. In vitro urease inhibitory assays showed that C1 exhibited the most potent activity (IC50 = 10.68 ± 0.09 μM), which significantly surpassed the positive control AHA (IC50 = 27.73 ± 0.33 μM), followed by C3 (IC50 = 15.49 ± 0.29 μM) and C2 (IC50 = 36.49 ± 0.13 μM). Molecular docking indicated that C1 binds to the urease active pocket stably via hydrogen bonding with HIS593 and hydrophobic interactions with ARG439/ALA440. DFT calculations revealed that the carboxyl oxygen atoms of C1 are potential electrophilic attack sites, while pyridine ring regions are prone to nucleophilic attacks. Structure-activity relationship (SAR) analysis suggested that the L-phenylalanine fragment and 2,2'-bipyridine co-ligand are crucial for enhancing urease inhibitory activity. These findings provide valuable insights for the development of novel Schiff base metal complexes as potent urease inhibitors.

Influence of adhesive type on microstructure and wear performance of SiC coated CK45 steel using GTA cladding: A cost-effective substitute for X120Mn12 alloy