Search Results (210)

Wollastonite-1A from Băița Bihor occurs in distal calcic skarns developed in the contact zone of a mainly granodioritic batholith, of Upper Cretaceous age, with Mesozoic limestones and dolostones. Wollastonite generally occurs in the inner part of metasomatic columns, in monomineralic skarns or associated with grossular and molybdenite-2H as ore mineral. The physical properties (i.e., refraction indices α = 1.616, β = 1.629, and γ = 1.631, 2V_α = 39° and density D_m = 2.922(3) g/cm³) are typical for a term close to the stoichiometry, which is confirmed by the chemical analysis. The chemical structural formula of the analyzed wollastonite-1A is (Ca_1.000Mg_0.002Mn_0.001Fe_0.001)(Al_0.004Ti_0.001Si_0.994)O₃, which closely approximates the ideal CaSiO₃. The Gladstone–Dale compatibility indices account for an excellent agreement between physical and chemical data. The mineral can be satisfactorily refined as triclinic, space group P̅1, with R₁ = 0.0678 and cell parameters a = 7.9233(3) Å, b = 7.3203(3) Å, c = 7.0651(3) Å, α = 90.053(3)°, β = 95.208(3)°, γ = 103.384(3)°. Both the IR and Raman spectra principally reveal bands related to vibrations of bridged and non-bridged oxygens pertaining to SiO₄ structural tetrahedra. At Băița Bihor, wollastonite-1A is part of the prograde paragenesis, marked by a peak temperature of 550–600 °C. Full article

Rutin is a naturally occurring flavonoid with well-documented antioxidant and pharmacological properties. In this study, a manganese(II) complex with rutin (Mn(II)-Rut) was synthesized in a solid state and characterized using FT-IR, Raman spectroscopy, thermogravimetric and elemental analysis, confirming its composition as C₂₇H₂₇O₁₆Mn₂·5H₂O. The IR spectra indicated that rutin coordinates manganese ions through the carbonyl group at the C4 position and the hydroxyl group at the C5 atom, as well as the catecholic system. The antioxidant potential of both Mn(II)-Rut and rutin was evaluated using several spectrophotometric assays. The Mn(II)-Rut complex showed stronger activity in most spectrophotometric assays than rutin, i.e., in ABTS assay, 50.37 ± 2.64% vs. 41.49 ± 1.38%; in CUPRAC assay, 0.468 ± 0.006 mM Trolox vs. 0.379 ± 0.007 mM Trolox; and FRAP assay, 0.201 ± 0.002 µM vs. 0.189 ± 0.003 µM. However, the DPPH assay complex showed a diminished effect compared with ligand (IC₅₀ 2.78 ± 0.13 µM vs. 0.98 ± 0.04 µM for rutin). Quantum-chemical calculations were also performed using the Gaussian09 program to determine the optimized geometric structures, electron charge distribution, and the energies of the HOMOs and LUMOs in the analyzed molecules in order to discuss the antioxidant mechanism of the molecules. Enzymatic assays demonstrated that the Mn(II) complex with rutin exhibited a stronger α-amylase inhibitory effect compared to free rutin, which showed the potential antidiabetic activity of the compound. The results suggest that the Mn(II) complex of rutin possesses better antioxidant and α-amylase inhibitory activity than the ligand alone. Full article

Iron(II) and manganese(II) complexes with N4Py [N4Py—N,N-bis(2-pyridylmethyl)-N-(bis-2-pyridylmethyl)amine] have been found to activate O₂ for the oxidation of α-pinene in acetonitrile. For example, for 1 M α-pinene, 0.5 mM [(N4Py)Fe^II]²⁺, and dioxygen as an oxidant, 90 mM α-pinene epoxide, 48 mM verbenol, and 50 mM verbenone have been formed, which, taking into account the concentrations of the minor products (myrtenol and myrtenal), gives a turnover number approximately equal to 400. Based on the amounts of products formed, the conversion of α-pinene is approximately 20% and 18% for iron and manganese catalysts, respectively. Although the manganese catalyst is somewhat less effective than the iron catalyst, the selectivity of the products is similar for both catalysts. Replacement of dioxygen with air as the oxidant causes the reaction yield to be lower. The proposed mechanism assumes the formation of a metal(IV)-oxo complex [(N4Py)M^IV=O]²⁺, M–Fe or Mn, during the simultaneous combination of a catalyst, O₂, and substrate, and its subsequent reactions toward the observed products. Full article

In zinc electrowinning, industrial Pb-Ag anodes have inherent limitations, including high oxygen evolution overpotential and rapid corrosion. This study constructs Ti-Ti₂N-PbO₂-CeMnO_x composite anodes to overcome these shortcoming, Electrochemical characterization revealed enhanced performance with a reduced overpotential (725 mV 50 mA cm⁻²) and lower Tafel slope (102.92 mV dec⁻¹) in the standard zinc electrowinning electrolyte, indicating faster oxygen evolution kinetics compared to commercial benchmarks. Analysis of the XPS test revealed an increase in the content of Mn³⁺, which helps enhance the OER catalytic activity of the electrode. The Ti/Ti₂N/α/β-PbO₂-CeMnO_x (abbreviation: CMO) composite anode exhibited superior corrosion resistance with an extended service life of 53 h under accelerated polarization at 2 A cm⁻². This durability enhancement is attributed to the combined effects of the Ti₂N interlayer and CMO incorporation, which effectively mitigate anode degradation through passivation inhibition. The developed fabrication strategy enables the production of dimensionally stable anodes (DSAs) with balanced electrocatalytic activity and operational stability, showing promising potential for industrial zinc electrowinning applications. Full article

Chronic environmental exposure to mixtures of heavy metals like manganese (Mn) and vanadium (V) has been associated with Parkinson’s disease (PD). We investigated the poorly understood neurotoxic effects of Mn/V co-exposure on PD-relevant behavioral phenotypes in transgenic mice expressing the human alpha-synuclein (αSyn) A53T mutant. C57BL/6 wild-type (WT) and transgenic A53T mice were intranasally co-exposed to 100 µg MnCl₂ and 75 µg V₂O₅ five times weekly for three months, simulating a 5-day workweek. This led to significant Mn/V accumulation in the brain. Exploratory locomotor activity declined significantly in Mn/V-treated A53T mice, but not in Mn/V-treated WT mice when compared to their respective vehicle controls. Motor coordination, assessed via a forced locomotor activity test, was not significantly affected in either group. In Mn/V-treated A53T mice, olfactory deficits were present, but not in Mn/V-treated WT mice. Behavioral despair, assessed by tail suspension and forced swim tests, was not induced by Mn/V co-exposure in any group compared to their vehicle controls. Mn/V-treated A53T mice exhibited anxiety-like behavior and hyperactivity. These findings suggest that Mn/V co-exposure exacerbates neurotoxic effects in A53T mice, with a more pronounced effect in males, providing insight into the role of metal mixture exposure in environmentally linked Parkinsonism. Full article

Hypo-peritectic steels are susceptible to interfacial cracking during thin-slab continuous casting, in which non-metallic inclusions play a critical role. This study systematically investigates the effects of inclusion type and morphology on interface cracking behavior in the steel matrix, with the aim of improving billet shell quality. Hot tensile experiments were conducted using a Gleeble 3800 thermal simulator, and a finite element–based cohesive zone model was developed to simulate inclusion-induced crack nucleation and propagation. The results demonstrate that inclusions markedly influence interfacial stress distribution and damage evolution. The maximum interfacial stresses associated with MnS, Al₂O₃, and composite inclusions are 20.7, 23.4, and 30.5 MPa, respectively. Owing to severe stress concentration at sharp corners, composite inclusions exhibit the earliest crack nucleation at an applied stress of 11.3 MPa and the highest energy dissipation. In all cases, cracks initially nucleate at the location of maximum tensile stress (α = 90°), propagate along the interface, and subsequently penetrate into the matrix, ultimately leading to failure. The strong agreement between numerical simulations and experimental results confirms that angular inclusions accelerate damage by disrupting matrix continuity. These findings provide theoretical guidance for improving hypo-peritectic steel quality through inclusion morphology control during continuous casting. Full article

The new alluaudite-group mineral manganobadalovite (IMA 2020-035), ideally NaNaMn(MgFe³⁺)(AsO₄)₃, was found in the Arsenatnaya fumarole, the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption 1975–1976, Tolbachik volcano, Kamchatka peninsula, Far-Eastern Region, Russia. Manganobadalovite is a fumarolic mineral, and its aggregates are found overgrowing basalt scoria or exhalative hematite crystal crusts. Associated minerals are badalovite, hematite, cassiterite, sanidine, glauberite and metathénardite. Manganobadalovite occurs as prismatic to equant crystals up to 0.8 mm long typically combined in open-work clusters; it also forms grains that are irregular in shape and cavernous granular crusts up to 0.5 cm. The mineral is transparent, with vitreous luster, and its color varies from red to yellow. Manganobadalovite is brittle and has a noticeable cleavage in one direction and uneven fracture. The calculated density is 4.108 g cm⁻³. Manganobadalovite is optically biaxial (+), α = 1.790 (7), β = 1.800 (7), γ = 1.815 (8) and 2V_meas = 80 (5)°. Chemical composition (wt.%, electron-microprobe): Na₂O 8.75, K₂O 0.17, MgO 5.32, CaO 3.68, MnO 10.09, CuO 0.42, Al₂O₃ 0.18, Fe₂O₃ 13.90, V₂O₅ 0.42, As₂O₅ 56.75, total 99.68. The empirical formula calculated based on 12 O apfu is Na_1.69K_0.02Ca_0.39Mn_0.85Mg_0.79Cu_0.03Fe³⁺_1.04Al_0.02(As_2.96V_0.03)_∑2.99O₁₂. The crystal structure was solved using single-crystal XRD data, R = 2.30%. Manganobadalovite is monoclinic, C2/c, a = 12.1848(5), b = 12.8924(4), c = 6.6970(3) Å, β = 113.113(5)°, V = 967.60(7) ų and Z = 4. The strongest reflections of the powder XRD pattern are [d,Å(I)(hkl)]: 6.43(30)020, 3.589(32)(−131, 310), 3.215(38)(040, −112), 3.079(23)(221, 002), 2.941(32)(−312, −222, −331), 2.852(15)(041), 2.788(100)(330, 400, 240, 022), 2.649(22)(−402, 112), 2.626(25)(−132). Manganobadalovite is named as an analogue of badalovite NaNaMg(MgFe³⁺)(AsO₄)₃ with Mn²⁺ prevailing in the M(1) site. Full article

Dysphania ambrosioides is a widely distributed species with a traditional use in folk medicine, but it exhibits marked chemical variability that limits its standardization. This study is the first to characterize the essential oil (EO) of three Ecuadorian populations—Arenillas (ARE), Pasaje (PAS) and Piñas (PIN)—using gas chromatography–mass spectrometry/flame ionization detection (GC-MS/FID), and to correlate its composition with edaphic properties and antioxidant activity. Chemical profiles revealed three distinct chemotypes: ARE (α-terpinene 65.35%, o-cymene 24.83% and ascaridole 3.30%), PAS (α-terpinene 56.31%, o-cymene 10.09% and ascaridole 10.84%) and PIN (α-terpinene 56.89%, o-cymene 17.07% and ascaridole 7.60%). The EO yield was low (0.030–0.064% w/w), coinciding with acidic and nutrient-poor soils. On the other hand, PAS, with its neutral soil and high nitrogen, produced the highest number of oxygenated compounds. Only PAS exhibited strong ABTS radical-scavenging activity (SC₅₀ = 37.99 ± 1.01 µg/mL). In contrast, ARE showed weak activity (SC₅₀ = 424 ± 1.01 µg/mL), while PIN showed moderate activity (SC₅₀ = 112.26 ± 1.01 µg/mL), which was correlated with its high total phenol content (298.48 mg EAG/L). The 2,2-diphenyl-1-picrylhydrazyl (DPPH) activity was low in all samples. Principal component analysis (PCA) confirmed clear separation of the chemotypes, which was linked to edaphic factors such as pH, heavy metals (Cu, Fe and Mn) and organic matter. These findings suggest that edaphic conditions may modulate the chemical composition and antioxidant activity of D. ambrosioides, indicating a potential approach for the sustainable selection of plant material. Full article

Although excessive manganese (Mn) exposure is known to cause neuromotor function in cases of poisoning, its effect on grip strength (a neuromotor marker) in older adults at environmental levels remains unclear. To investigate this issue, we conducted an integrated investigation combining epidemiology and animal experimentation to examine the association between urinary manganese and grip strength. A cross-sectional study of 375 elderly men (60–74 years) was conducted in Guangxi, China, from 2016 to 2017. Urinary Mn concentrations were determined by ICP-MS, and their associations with grip strength were evaluated using generalized linear models and restricted cubic splines. In parallel, 32 six-week-old male C57BL/6J mice were exposed to 0, 5, 10, or 15 mg/kg MnCl₂·4H₂O via intraperitoneal injection for 6 weeks. Forelimb grip strength of the mice was measured after the final exposure, and mRNA expression of inflammatory markers and cytokines (C reactive protein (CRP), interleukin (IL)-6, and tumor necrosis factor (TNF)-α in triceps) in triceps tissue was quantified. The median urinary Mn concentration in the study population was 0.22 μg/g creatinine. After adjusting for confounders, urinary Mn was inversely associated with hand grip strength (highest vs. lowest tertile: β = −3.57 kg; 95% CI: −5.68 to −1.47; p-trend = 0.007). Similarly, in male C57BL/6J mice, grip strengths declined significantly with increasing Mn exposure (p-trend < 0.0001), accompanied by upregulation of the mRNA levels of CRP, IL-6 and TNF-α in muscle tissue. Together, our findings suggest that environmental manganese exposure is inversely associated with grip strength in elderly men. While the manganese doses used in the animal study exceeded typical human environmental exposure, the experimental results further indicate that such grip strength reduction may be linked to muscle inflammation. Full article

Grokhovskyite, CuCrS₂, was observed in small sulfide inclusions (up to 50–80 µm) in Ni-rich iron (kamacite) of the Uakit iron meteorite (IIAB) in the Republic of Buryatia, Russia. The grain sizes of this mineral are usually less than 5 μm, and the biggest detected crystals are 10 × 5 μm in size. It is commonly associated with daubréelite, troilite, schreibersite, and, sometimes, with carlsbergite and uakitite. Within inclusions, the mineral forms elongated splintered crystals, or, rarely, needle-shaped grains in daubréelite. The grokhovskyite-containing associations in the Uakit meteorite seem to form due to high-temperature (>1000 °C) separation of Fe-Cr sulfide liquid, which is locally enriched in Cu, from Fe-Ni metal melt. Physical and optical properties of grokhovskyite are quite similar to those of synthetic CuCrS₂: yellow–brown and non-transparent phase with metallic luster; Mohs hardness ≈ 4; gray to light gray color with yellow tint in reflected light; weak to medium bireflectance, anisotropy, and pleochroism; density (calc.) = 4.559 g/cm³. Grokhovskyite is structurally related to the Cr-containing disulfide minerals with general formula Me⁺CrS₂ (where Me⁺ = Na, Cu, Ag), including caswellsilverite, NaCrS₂; schöllhornite, Na_0.3CrS₂·H₂O; and cronusite, Ca_0.2CrS₂·2H₂O. Structural data were obtained for one grokhovskyite crystal using the EBSD technique. Fitting of the EBSD patterns for a synthetic α-CuCrS₂ model (trigonal R3m; a = 3.4794(8) Å; c = 18.702(4) Å; V = 196.08(10) ų; Z = 3) resulted in the parameter MAD = 0.57–1.16° (good fit). Analytical data for grokhovskyite (n = 36, in wt.%) are as follows: Cu—32.97; Cr—27.65; Fe—3.69; Ni—0.16; S—35.71; Na, Zn, V, Mn, and Co—below detection limit (<0.005 wt.%). The empirical formula is (Cu_0.930Cr_0.952Fe_0.118Ni_0.005)_2.005S_1.995; however, different concentrations of Fe are indicated in two individual grains of grokhovskyite (0.09–0.17 apfu). Such variations may be explained by Fe incorporation in the grokhovskyite structure according to the scheme ^IVCu⁺ + ^VICr³⁺ → ^IVFe²⁺ + ^VIFe²⁺. The three main bands (near 110, 250, and 310 cm⁻¹), which are common of synthetic CuCrS₂, were observed in the Raman spectra of grokhovskyite. Full article

The gliding arc plasma technique (glidarc) was used for the precipitation and deposition of Mn or Fe oxides on zirconia fibers. Two types of fibers were used: commercial (Fib Zr(C)) and biomorphic (Fib Zr(B)) ZrO₂ fibers, the latter produced using cotton as a biotemplate. Both series of supported catalysts were characterized physicochemically and morphologically. Scanning Electron Microscopy (SEM) analyses showed that Fib Zr(B) largely retained the morphology of cotton. Fib Zr(B) presented the tetragonal phase (t-ZrO₂), while Fib Zr(C) exhibited the monoclinic phase (m-ZrO₂). Using X-ray Diffraction (XRD), the cryptomelane phase (K_xMn₈O₁₆) was identified only for Mn-Fib Zr(B). In the case of Fe-supported samples, the α-Fe₂O₃ phase appeared clearly in both biomorphic and commercial fibers. SEM and Transmission Electron Microscopy (TEM) images revealed that the precipitated iron oxides appeared to be better distributed than the manganese oxides, covering the outer surface of the fibrous supports more homogeneously. X-ray Photoelectron Spectroscopy (XPS) confirmed that Mn has an average oxidation state between 3+ and 4+, consistent with the cryptomelane phase detected by XRD. The synthesized supported systems were tested as catalysts in soot and CO oxidation, with the Mn-supported fibers proving to be more active than their Fe-containing counterparts in both reactions. Full article

Composite materials based on low-density polyethylene (LDPE) embedded with iron-manganese nanoparticles with compositions Fe_0.9Mn_0.1 and Fe_0.8Mn_0.2 were prepared and investigated. The newly created composites were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and Mössbauer spectroscopy. The composition, electronic, and atomic structure of the nanoparticles were established. The study confirms that the nanoparticles possess a ‘core-shell’ structure, the nature of which depends on the manganese content. The nanoparticles of Fe_0.8Mn_0.2 in LDPE exhibit a three-layered structure: a metallic α-Fe core is coated with an intermediate oxidized layer structurally close to Fe₂O₃, while the outermost shell consists of manganese oxide (Mn₂O₃). In contrast, nanoparticles with lower Mn content Fe_0.9Mn_0.1 show a predominantly fully oxidized structure. This structural evolution is consistent with thermodynamic principles, where manganese, having a higher oxide formation enthalpy, migrates to the surface. The core–shell architecture is promising for applications requiring stable magnetic components or tailored catalytic interfaces within a polymer matrix. Full article

The direct synthesis of long-chain α-olefins from syngas offers a strategically vital pathway for producing high-value chemicals from alternative carbon resources. However, achieving high selectivity toward C₅₊ olefins remains challenging due to competing paraffin formation and difficulties in precisely regulating chain growth kinetics. To mitigate these critical challenges, a series of Rh-promoted Co-Mn catalysts supported on SiO₂ were synthesized using a carbon-mediated impregnation strategy for the direct conversion of syngas to long-chain α-olefins (C₅₊). The introduction of Rh significantly enhanced both catalytic activity and C₅₊ olefin selectivity. The optimal 1.1 wt% Rh-loaded catalyst achieved 24.6% CO conversion and 46.0% total olefin selectivity, with 34.2% of the selectivity toward C₅₊ olefins, while maintaining low CH₄ (6.2%) and CO₂ (<1%) selectivity. Comprehensive characterization techniques, including XRD, H₂-TPR, XPS, and TEM/HAADF-STEM, revealed that the carbon-mediated method facilitated the formation of highly dispersed Co₃O₄ nanoparticles with abundant oxygen vacancies and strengthened the Co-MnO_x interface. Rh promotion modulated the cobalt speciation (Co⁰/Co²⁺), improved reducibility, and enhanced the metal-support interaction. This promoted chain growth and olefin desorption while suppressing over-hydrogenation. This study demonstrates the efficacy of Rh promotion and carbon mediation in designing high-performance Fischer-Tropsch catalysts for selective α-olefin synthesis, offering new insights into the design of efficient metal-oxide interfacial catalysts. Full article

Bee pollen is highly regarded for its nutritional and therapeutic properties, and Tunisia’s diverse ecosystems provide ideal conditions to produce high-quality bee pollen. The aim of this study was to characterize seven polyfloral bee pollen samples from major Tunisian regions, analysing their physicochemical and phytochemical parameters to evaluate compliance with national quality standards and their potential contribution to human nutrition. The nutritional and biochemical characterization of bee pollen samples was performed using standardized methods. Phenolic, flavonoid, and tannin contents were measured by colorimetric assays; carotenoids and chlorophylls spectrophotometrically; amino acids and sugars by HPLC; fatty acids by GC–MS; and minerals by atomic absorption spectroscopy. Amino acid levels were relatively constant between samples, but significant differences (p < 0.05) were noted, with concentrations ranging from 4.93 ± 0.15 mg·kg⁻¹ (K-O4) to 82.72 ± 2.36 mg·kg⁻¹ (O-O4). Tyrosine, aspartic acid, and glutamic acid were the dominant amino acids in both total and free forms, while threonine was identified as the relatively limiting amino acid. The proportion of total essential amino acids (TEAA) to total amino acids (TAA) met the nutritional recommendations set by the FAO. A total of 16 fatty acids were quantified in the seven BP samples, including nine saturated and six unsaturated fatty acids, with total content ranging from 0.26 g/100 g⁻¹ (T-03) to 37.06 g/100 g⁻¹ (G-03), which the primary fatty acids identified were α-linolenic acid, palmitic acid, and oleic acid. However, palmitoleic acid was detected in only two samples, in small amounts (0.34% and 0.46%). Essential minerals such as K, Ca, P, Mg, Zn, Fe, Mn, and Cu were present in significant amounts, playing a crucial role in both plant metabolism and human health Despite variations between samples, Tunisian bee pollen was overall evaluated as a valuable dietary supplement. Full article

Although Ru-based catalysts have been investigated in various oxidation systems, their application in sulfate radical-based AOPs, particularly as heterogeneous activators for acidic wastewater treatment, remains limited. Herein, Ru was incorporated into α-MnO₂ via lattice doping and surface loading to construct Ru_latt/α-MnO₂ and Ru_surf/α-MnO₂, and their PMS activation performance toward carbamazepine (CBZ) degradation was evaluated. Ru_latt/α-MnO₂ exhibited superior activity, achieving near-complete CBZ removal within minutes under acidic conditions. PMS dosage, catalyst loading, and pH affected the degradation efficiency, with acidic environments significantly enhancing PMS activation. Cl⁻ slightly promoted CBZ degradation, whereas HCO₃⁻ and natural organic matter inhibited it. Mechanistic analysis revealed that Ru activated PMS through a nonradical pathway, continuously generating ¹O₂ via a reversible Ru (II)/Ru (III)/Ru (IV) cycle, while the Mn (III)/Mn (IV) redox couple acted as an electron buffer to sustain Ru cycling and improve durability. The catalyst maintained high activity in complex water matrices, demonstrating strong potential for practical remediation of CBZ-contaminated acidic wastewater. Full article