Search Results (176)

Background and Objectives: Ultrasound-guided placement of tunneled hemodialysis catheters may be useful when fluoroscopy is unavailable or radiation exposure should be avoided. This study describes a technique based on direct ultrasound visualization of the metallic guidewire within the right atrium and evaluates one-year clinical and functional outcomes. Materials and Methods: We conducted a single-center retrospective observational study of 319 adult hemodialysis patients undergoing tunneled catheter placement. The technique combined intravascular guidewire length measurement with subcostal ultrasound visualization of the guidewire tip in the right atrium. Baseline characteristics, insertion site, immediate complications, blood flow rate, Kt/V, and extracorporeal circuit pressures were analyzed. Results: Mean age was 55.9 ± 14.5 years, and 58.6% were women. The main causes of chronic kidney disease were diabetes mellitus and arterial hypertension. Mean blood flow rate was 349 mL/min at 3 months and 357 mL/min at 12 months. Mean Kt/V at 12 months was 1.57. No catheter malpositions requiring immediate repositioning were documented. Procedure-related complications were infrequent and mainly local. Conclusions: Ultrasound-guided tunneled catheter placement using direct visualization of the guidewire within the right atrium was technically feasible and associated with favorable functional parameters and few immediate complications. Given the retrospective design and lack of a comparative group, these findings should be interpreted with caution. Prospective comparative studies are needed to confirm safety, reproducibility, and clinical utility. Full article

The development of sustainable, noble-metal-free photocatalytic systems for acceptorless dehydrogenation (ADH) of cyclic amines remains a significant challenge. Herein, we report a novel heterogeneous photocatalyst constructed by covalently grafting a cobaloxime-based proton reduction catalyst onto a photosensitive covalent organic framework (PT-COF). The tailored PT-COF scaffold, featuring a donor–acceptor architecture and uncondensed amino groups, serves as both an efficient visible-light harvester and a porous support for cobalt active sites. The resulting Co-PT-COF hybrid exhibits excellent photocatalytic activity for the ADH of a wide range of cyclic amines, affording the corresponding N-heteroarenes in 62–95% yields under an Ar atmosphere at 28 °C with blue LED irradiation for 12 h in water. Notably, the catalyst demonstrates outstanding recyclability over five consecutive cycles with minimal loss of activity or cobalt leaching. Comprehensive photoelectrochemical and spectroscopic studies reveal that enhanced charge separation and efficient electron transfer from the photoexcited COF to the cobalt centers underpin the superior performance. Mechanistic investigations, including in situ EPR spectroscopy, confirm the involvement of α-amino radical intermediates in the catalytic cycle. This work establishes a sustainable platform for solar-driven dehydrogenation chemistry and provides a versatile blueprint for integrating molecular catalysts with photoactive frameworks. Full article

Self-powered integrated electrochemical systems require electrode materials that can simultaneously provide energy storage and sensing functions. Boron-doped diamond (BDD) electrodes have good chemical stability and a wide potential window, but their small specific surface area and slow interfacial charge transfer limit their use in such bifunctional applications. In this work, we prepared a three-dimensional porous BDD scaffold on titanium foam by hot-filament chemical vapor deposition, and then grew polypyrrole (PPy) layers on the scaffold by in situ oxidative polymerization. The polymerization time was varied from 8 to 20 h. The BDD/PPy composite obtained after 12 h showed an areal capacitance of 398.6 ± 15.2 mF/cm² at 1 mA/cm², which is about 5.8 times that of the porous BDD alone (67.9 mF/cm²). Its charge transfer resistance (R_ct) was as low as 1.3 ± 0.1 Ω, among the lowest reported for BDD-based electrodes. The porous BDD framework provides ion diffusion pathways, while the PPy layer introduces pseudocapacitance. X-ray photoelectron spectroscopy reveals that the PPy layer contains pyrrolic –NH– groups, which are known to chelate various water pollutants (e.g., heavy metal ions and organic molecules). Based on these surface properties and the low R_ct, we suggest that this composite may have theoretical potential for preconcentrating and detecting multiple pollutants. This work demonstrates a way to improve the capacitance of BDD-based electrodes and may serve as a starting point for future exploration in integrated energy-sensing devices after experimental validation. Full article

Implant-Supported Fixed Prostheses (ISFPs) have become a common option for the rehabilitation of fully edentulous arches and have traditionally incorporated metallic substructures with ceramic or acrylic veneering. The rapid expansion of CAD/CAM technologies has introduced not only a range of polymer-based materials as alternatives to conventional metallic frameworks but also the possibility of the fabrication of monolithic rehabilitations. However, the evidence regarding the mechanical behavior of monolithic polymer-based full-arch rehabilitations remains limited. This study aimed to evaluate and compare the mechanical performance of monolithic polymer-based complete prostheses under static loading using Digital Image Correlation (DIC). A total of 12 specimens (3 per group) simulating an FP3 maxillary full-arch ISFP supported by four implants were milled from four materials: poly(ether ether ketone) (G1-PEEK), poly(ether ketone ketone) (G2-PEKK), poly(methyl methacrylate) (G3-PMMA), and fiber-reinforced composite (G4-FRC). All specimens were subjected to static loading up to 200 N at the incisors region, corresponding to the anterior unsupported span, and at the occlusal surface of the molars, corresponding to the most distal portion of the cantilever, using a universal testing machine. Full-field vertical displacement and strain distributions (principal tensile, compressive, and von Mises) were acquired through a stereo DIC system and analyzed using a Linear Mixed-Effects Model with Tukey’s HSD post hoc comparisons (α = 0.05). All prostheses withstood the applied load without macroscopic failure. G3-PMMA exhibited the highest vertical displacement, exceeding 1000 µm in the anterior span and 1500 µm in the cantilever region, along with the greatest strain concentrations, particularly at the interproximal embrasures distal to the terminal abutment. G1-PEEK provided the lowest displacement in the anterior span. G4-FRC presented displacements similar to G1-PEEK and G2-PEKK at the distal cantilever, but the lowest tensile strains and the most homogeneous strain dissipation in both loading at the anterior unsupported span and distal cantilever. This indicated that the biomechanical performance of full-arch ISFPs is highly influenced by the polymer used. PEEK, PEKK, and FRC appear as promising alternatives to PMMA for monolithic full-arch rehabilitations. Full article

Indigenous clays are widely used for facial skincare in South Africa, yet their suitability for cosmetic incorporation remains poorly characterised, particularly with respect to elemental safety. This study assessed two traditionally applied clays for acne-prone skin (Umcako and Ibomvu) using a multi-analytical workflow encompassing colorimetry, scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), pH measurement, in vitro sun protection factor (SPF) estimation, X-ray fluorescence (XRF), and inductively coupled plasma mass spectrometry (ICP-MS) of clay leachates. XRD showed both materials to be kaolinite-dominated, with higher kaolinite content in Umcako (92.5 wt%) than in Ibomvu (77.3 wt%); SEM revealed characteristic overlapping pseudo-hexagonal platelets, and FT-IR did not indicate prominent organic functional groups under the conditions tested. The clays were mildly acidic (pH 4.23–4.48), aligning with physiological skin pH, but exhibited low photoprotective performance when assessed alone (SPF ≈ 2.5–2.6). Elemental screening identified nutritionally relevant trace minerals but also detected regulated or sensitising metals, with Ibomvu showing elevated bulk Pb (53 ± 12 ppm), Ni (126 ± 71 ppm) and Zn (72 ± 26 ppm), while Umcako contained elevated bulk Cr (460 ± 140 ppm) and Pb (18 ± 6 ppm). Overall, although Umcako and Ibomvu display physicochemical properties compatible with clay-based cosmetic products, their heavy metal burden, together with the potential for dermal exposure highlighted by leachate analysis, indicates that purification, batch-to-batch monitoring and regulatory risk assessment are essential before safe cosmetic use. Full article

Cadmium (Cd) is a ubiquitous heavy metal environmental toxicant, and exposure poses a persistent public health concern due to its bioaccumulative properties. However, the impact of maternal Cd exposure on mammary gland function during lactation remains insufficiently understood. In this study, we investigated the effects of Cd exposure during pregnancy and lactation on mammary gland development, hormonal homeostasis, and lactational performance using a drinking water exposure model. Pregnant 7-week-old ICR mice were randomly assigned into Control and Cd groups. The Control group received standard drinking water, while the Cd group was administered water supplemented with Cd (12 mg/L). Results demonstrated that maternal Cd exposure markedly reduced maternal and offspring weight, respectively. Histological analysis revealed that Cd exposure resulted in decreased numbers of mammary alveoli and widened interstitial spaces, indicating impaired mammary development. In addition, Cd exposure markedly compromised lactational performance, as reflected by reduced milk yield and decreased levels of milk protein, fat, and lactose across multiple lactation stages. Integrated metabolomic and transcriptomic analyses further revealed substantial alterations in hormonal profiles and metabolic pathways associated with mammary gland function. Notably, Cd accumulation was detected in mammary tissue and milk, accompanied by transcriptional changes in genes involved in milk synthesis and lipid metabolism. In conclusion, these findings indicated that maternal Cd exposure during pregnancy and lactation is associated with structural and functional alterations of the mammary gland, leading to reduced lactational performance and impaired offspring growth. The findings contribute to a better understanding of the risks posed by environmental Cd exposure, emphasizing the need for effective public health strategies to mitigate its impact on maternal and infant health. Full article

Background and Objectives: Percutaneous coronary intervention (PCI) has markedly improved outcomes in coronary artery disease through the implantation of bare-metal stents (BMS) or drug-eluting stents (DES). However, in-stent restenosis (ISR) remains a significant complication, often necessitating repeat interventions. This study aimed to identify risk factors associated with ISR in patients with ST-elevation myocardial infarction (STEMI) who underwent PCI. Materials and Methods: We conducted a retrospective, non-randomized observational study of 107 STEMI patients treated with PCI between January 2016 and December 2019 who subsequently underwent clinically indicated (predominantly symptom-driven) follow-up coronary angiography within 12 months. ISR was defined as ≥50% luminal narrowing at follow-up angiography. Time-to-event analysis was performed using Cox regression models, incorporating clinical, biochemical, and angiographic variables. Results: In this selected cohort of patients undergoing follow-up angiography, ISR of any degree was identified in 87% of patients, and 52% had restenosis >70%. Advanced age, prior cardiovascular events, diabetes mellitus, chronic kidney disease, and history of stroke significantly increased the hazard of ISR. Smoking, dyslipidemia, and hypertension were prevalent in patients with severe ISR. Women presented with more severe clinical profiles (higher Killip class and troponin levels). DES showed slightly better TIMI flow than BMS, but stent type, dimensions, and number did not significantly impact restenosis risk. Thrombolytic therapy was associated with a significantly reduced ISR hazard. Mortality was 6% in patients with severe ISR. The highest restenosis incidence occurred in the LAD and RCA territories. Conclusions: ISR is a multifactorial process influenced by demographic, clinical, and procedural factors. Despite technological advances, ISR remains a prevalent issue, particularly in high-risk groups undergoing clinically indicated follow-up angiography. Secondary prevention strategies, optimized stent deployment, and targeted therapies addressing inflammation and vascular remodeling are essential to improving long-term PCI outcomes. Full article

The reliability of adhesive bonding to CAD/CAM resin composites is influenced not only by material composition and surface treatment but also by the testing methodology used to assess bond strength. However, the impact of different shear bond strength (SBS) test configurations remains insufficiently clarified. This study evaluated the influence of different surface pretreatment protocols and SBS test methods on the bonding performance of a self-adhesive resin cement to two CAD/CAM materials: a conventional particulate-filled composite (Cerasmart 270) and an experimental short glass fiber-reinforced composite (SFRC CAD). Specimens (14 × 12 × 3 mm; n = 80 per material) were ground with 320-grit silicon carbide paper and divided according to surface pretreatment: airborne-particle abrasion (APA) or APA followed by hydrofluoric acid application for 60 s (APA + HF). Each group was further subdivided based on the SBS test method using either resin cement cylinders fabricated with a custom transparent mold (diameter: 3.6 mm; height: 3 mm) or metallic cylinders cemented to the treated surface. Half of the specimens were tested after 48 h of water storage, while the remainder underwent hydrothermal aging by boiling in water for 16 h prior to testing. Material type, SBS test method, surface pretreatment, and aging significantly affected bond strength (p < 0.05). The metallic cylinder method produced higher SBS values than the transparent mold technique, particularly for SFRC CAD. APA + HF tended to reduce SBS in Cerasmart 270, particularly after aging, whereas SFRC CAD showed comparable or higher bond strength values with APA alone. Aging decreased SBS in most groups. Overall, bond strength was influenced by both material type and test methodology. Within the limitations of this study, airborne-particle abrasion alone may be sufficient for SFRC CAD materials, while additional HF treatment may not provide further benefit. These findings highlight the importance of considering both material characteristics and test configuration when interpreting laboratory bond strength data. Full article

Water-based drill cuttings generated during onshore natural gas development are complex solid wastes that may pose environmental risks if improperly managed. This study evaluates the feasibility of reutilizing water-based drill cuttings as pavement base materials after stabilization using a novel composite stabilizer composed of cement, stabilizer liquid agent, and water-reducing powder (CLP stabilizer). Mix proportion optimization was conducted through compaction and 7-day unconfined compressive strength tests, followed by evaluation of road performance, including strength, compressive rebound modulus, water stability, and temperature shrinkage, with stabilized powder stabilized soil as a control. Microstructural characteristics were analyzed using X-ray diffraction and scanning electron microscopy, and environmental safety was assessed through heavy metal leaching tests and background soil investigation. The results show that the optimal mixture ratio of curing agent (5% cement + 2% liquid stabilizer + 8% superplasticizer powder) satisfies the strength requirement for pre-drilling road bases, exhibiting superior performance compared to the control group. When the stabilizer dosage reaches 9%, the 7-day unconfined compressive strength achieves a maximum of 3.38 MPa, representing a 51% increase over the control group. At a stabilizer dosage of 12%, the splitting tensile strength reaches a peak value of 0.901 MPa, showing a 60.3% improvement. These results indicate enhanced deformation resistance, water stability, and reduced temperature shrinkage rates. Microstructural analysis indicates that the formation of calcium silicate hydrate (C-S-H) gel and ettringite (AFt phase) leads to a denser structure and enhanced durability. Heavy metal concentrations comply with relevant standards, demonstrating controllable environmental risks and supporting sustainable pavement base application. Full article

Phenazine derivatives are promising metal-free chromophores with strong redox and photophysical properties, yet their use in photocatalytic hydrogenation remains limited. Here, we report a homogeneous phenazine-based system for the visible-light-driven hydrogenation of nitroarenes under mild conditions. Using nitrobenzene as a model substrate and triethanolamine as a sacrificial hydrogen source, the photocatalyst achieved aniline yields of up to 81% after 12 h of irradiation at 390 nm. Systematic variation in reaction parameters revealed that catalyst structure, solvent, and light wavelength strongly influence performance. Kinetic analysis indicated that prolonged irradiation reduces overall yield due to the reconversion of reactive intermediates. The system exhibited higher efficiency toward nitroarenes bearing electron-withdrawing groups, while aliphatic nitro compounds underwent only partial reduction. Mechanistic studies using UV–Vis, fluorescence, and EPR spectroscopy confirmed the formation of persistent radical species and supported a stepwise electron and proton transfer mechanism. This work showcases the potential of phenazine-based photocatalysts as metal-free platforms for nitroarene reduction under visible light. Full article

This study provides a comprehensive assessment of 12 metal(loid)s in the muscle tissue of the commercially vital shrimp, Penaeus semisulcatus, from four stations (Bozyazi, Silifke, Karatas, and Iskenderun) along the Northeastern Mediterranean. Metal concentrations were evaluated separately for males and females, utilizing Estimated Weekly Intake (EWI), Target Hazard Quotient (THQ), Carcinogenic Risk (CR), and Selenium Health Benefit Value (HBV_Se) indices. While the species is generally safe for consumption across the region, a striking, localized bioaccumulation of Chromium (Cr) was identified specifically in Iskenderun Bay, where male shrimps exhibited concentrations (1.209 mg/kg wet weight) approximately 10-fold higher than females, highlighting a sex-specific sensitivity likely linked to metabolic and physiological differences. By adopting a precautionary risk assessment framework—considering the region’s intense industrial profile—this localized spike resulted in a Total Carcinogenic Risk (∑CR = 5.15 × 10⁻⁴) for this group, exceeding the priority threshold. Furthermore, widespread Lead (Pb) contamination was detected across all stations, with several samples surpassing EU maximum levels (0.50 mg/kg). Regarding Arsenic (As), while high total concentrations led to THQ values > 1 across the regional gradient, this was characterized as a conservative modeling artifact rather than a physiological threat, as Arsenic in crustaceans is predominantly in the non-toxic organic form. Conversely, any potential risk from Mercury (Hg) was conclusively mitigated by an overwhelming molar excess of Selenium (Se) at all locations, confirmed by consistently positive HBV_Se values (0.312–0.658). In conclusion, our findings demonstrate that seafood safety is conditional and region-specific. The study underscores that localized contamination “hotspots” can be easily masked by non-sex-specific sampling and emphasizes the necessity of moving beyond simplistic risk models by incorporating selenium-mercury antagonism and precautionary risk assumptions for industrial pollutants. Full article

Human activities inevitably affect natural ecosystems, the impact of which most often refers to negative factors resulting in the accumulation of toxic elements in environmental components. This study quantified the presence of 12 toxic elements (Cd, Co, Cr, Cu, Hg, Fe, Mn, Ni, Pb, Zn, As, and Se) in water, soil, and six melliferous plant species across the Republic of Croatia. Sampling sites were classified into four groups according to the dominant anthropogenic impact: agricultural areas, urban and traffic-affected zones, industrial vicinities, and forested hill regions. The results demonstrate the transfer of toxic elements from abiotic matrices into plants, indicating their potential as bioaccumulators. Soil contamination with toxic metals was identified as a relevant ecological risk factor, while contamination of melliferous plants highlights potential implications for human health through the production of honeybee-derived products. Element concentrations in water and soil were determined using three atomic absorption spectrometry techniques (FAAS, GFAAS, and CVAAS), whereas concentrations in floral samples of melliferous plants were measured using inductively coupled plasma mass spectrometry (ICP MS). The obtained results were interpreted in relation to natural background levels and the current national legislation. Anthropogenic impacts were further evaluated using environmental quality indices and bioaccumulation factors, revealing site-specific contamination patterns of both natural and anthropogenic origin. Full article

A new solvent extraction system for the removal of 4f ions (Ln³⁺) from water by use of chelating ligands (HLn, n = 5, 6, 7, and 8) composed of heterocyclic receptors and one β-dicarbonyl fragment is reported. The covalent attachment of a β-dicarbonyl unit to a saturated N-heterocycle with variable ring size resulted in a cooperative interaction within the receptor for Ln³⁺ transfer, which remarkably enhanced the efficiency of the process. The intramolecular cooperative effect was observed only in the ionic liquid (IL) solvent system, providing a several-fold increase in extraction performance for Ln³⁺ ions (La, Nd, Eu and Dy) over chloroform. Thus, it is not possible to confirm that an identical reaction mechanism operated in both liquid systems: IL or CHCl₃. The existence of neutral chelates of the type LnL₃ or anionic lanthanoid complexes [LnL₄⁻] in an ionic medium during the solvent extraction process applying various solvent systems has been established hitherto. Consequently, the Ln³⁺ ion was held by HLn molecules more rigidly in an IL medium ([C₁C_nim⁺]/[C₁C₄pyr⁺]/[C₁C₄pip⁺][Tf₂N⁻], n = 4, 6, 8, 10) than in chloroform, representing an important factor dominating the magnitude of the intramolecular cooperative effect of the chelating ligands for Ln³⁺ ions. The effect of the diluent’s chemical nature on the metal extraction and separation has been studied and discussed thoroughly. Furthermore, competitive solvent extraction and separation studies with various s-, p-, d-, and f-ions of the periodic table revealed that the magnitude of the intramolecular cooperative effect depends on the suitability between the metal ion size and the cavity size or flexibility of the HLn compounds. In addition, the solvent extraction process of 12 refractory metals and 8 platinum group metals with the synthesized chelating extractants is also investigated in different organic liquid media. Full article

Heavy metal exposure is increasingly linked to impaired childhood growth, but the biological mechanisms are poorly understood. Here, we assessed associations between heavy metal exposure and growth impairment (idiopathic short stature [ISS] and growth hormone deficiency [GHD]) in 36 children (24 cases, 12 controls, males 41.7%), identifying related alterations in circulating exosomal miRNAs. Blood/urine concentrations of nine metals, including Pb, As, and Hg were measured, and serum exosomal miRNAs were profiled via sequencing. Elevated heavy metal exposure was associated with significantly increased proportions of ISS and GHD. Specifically, high blood Pb was associated with ISS (p = 0.01) and high urinary As with overall short stature (p = 0.03). Elevated urinary Hg showed a marginal association with GHD (p = 0.07). Differentially expressed miRNAs were identified: hsa-miR-4488 was downregulated in high-Pb and ISS groups, whereas hsa-miR-133a-3p and hsa-miR-4516 were upregulated in high urinary Hg/As and GHD groups. Predicted targets of these miRNAs involved growth hormone (GH)–insulin-like growth factor-1 (IGF-1) signaling and endochondral ossification. In conclusion, Pb, As, and Hg exposures were associated with impaired growth in children. The dysregulation of related miRNAs suggests biological mechanisms involving both local growth-plate dysfunction and GH-IGF1 signaling disruption. Full article

The six platinum group elements (PGE) are among the rarest elements in the upper continental crust of the earth. Higher values of PGE have been detected in the upper mantle and in chondrite meteorites. The PGE are siderophile and chalcophile elements and are divided into the following: (1) the Ir subgroup (IPGE) = Os, Ir, and Ru and (2) the Pd subgroup (PPGE) = Rh, Pt, and Pd. The IPGE are more refractory and less chalcophile than the PPGE. High concentrations of PGE led, in rare cases, to the formation of mineral deposits. The PGE are carried in discrete phases, the platinum group minerals (PGM), and are included as trace elements into the structure of base metal sulphides (BM), such as pentlandite, chalcopyrite, pyrite, and pyrrhotite. Similarly to PGE, the PGM are also divided into two main groups, i.e., IPGM composed of Os, Ir, and Ru and PPGM containing Rh, Pt, and Pd. The PGM occur both in mafic and ultramafic rocks and are mainly hosted in stratiform reefs, sulphide-rich lenses, and placer deposits. Presently, there are only 169 valid PGM that represent about 2.7% of all 6176 minerals discovered so far. However, 496 PGM are listed among the valid species that have not yet been officially accepted, while a further 641 are considered as invalid or discredited species. The main reason for the incomplete characterization of PGM resides in their mode of occurrence, i.e., as grains in composite aggregates of a few microns in size, which makes it difficult to determine their crystallography. Among the PGM officially accepted by the IMA, only 13 (8%) were discovered before 1958, the year when the IMA was established. The highest number of PGM was discovered between 1970 and 1979, and 99 PGM have been accepted from 1980 until now. Of the 169 PGM accepted by the IMA, 44% are named in honour of a person, typically a scientist or geologist, and 31% are named after their discovery localities. The nomenclature of 25% of the PGM is based on their chemical composition and/or their physical properties. PGM have been discovered in 25 countries throughout the world, with 64 from Russia, 17 from Canada and South Africa (each), 15 from China, 12 from the USA, 8 from Brazil, 6 from Japan, 5 from Congo, 3 from Finland and Germany (each), 2 from the Dominican Republic, Greenland, Malaysia, and Papua New Guinea each, and only 1 from Argentine, Australia, Bulgaria, Colombia, Czech Republic, England, Ethiopia, Guyana, Mexico, Serbia, and Tanzania each. Most PGM phases contain Pd (82 phases, 48% of all accepted PGM), followed, in decreasing order of abundances, by those of Pt 35 phases (21%), Rh 23 phases (14%), Ir 18 phases (11%), Ru 7 phases (4%), and Os 4 phases (2%). The six PGE forming the PGM are bonded to other elements such as Fe, Ni, Cu, S, As, Te, Bi, Sb, Se, Sn, Hg, Ag, Zn, Si, Pb, Ge, In, Mo, and O. Thirty-two percent of the 169 valid PGM crystallize in the cubic system, 17% are orthorhombic, 16% hexagonal, 14% tetragonal, 11% trigonal, 3% monoclinic, and only 1% triclinic. Some PGM are members of a solid-solution series, which may be complete or contain a miscibility gap, providing information concerning the chemical and physical environment in which the mineral was formed. The refractory IPGM precipitate principally in primitive, high-temperature, mantle-hosted rocks such as podiform and layered chromitites. Being more chalcophile, PPGE are preferentially collected and concentrated in an immiscible sulphide liquid, and, under appropriate conditions, the PPGM can precipitate in a thermal range of about 900–300 °C in the presence of fluids and a progressive increase of oxygen fugacity (fO₂). Thus, a great number of Pt and Pd minerals have been described in Ni-Cu sulphide deposits. Two main genetic models have been proposed for the formation of PGM nuggets: (1) Detrital PGM represent magmatic grains that were mechanically liberated from their primary source by weathering and erosion with or without minor alteration processes, and (2) PGM reprecipitated in the supergene environment through a complex process that comprises solubility, the leaching of PGE from the primary PGM, and variation in Eh-pH and microbial activity. These two models do not exclude each other, and alluvial deposits may contain contributions from both processes. Full article