Simón Bolívar University

Zero-valent trigonal selenium nanoparticles (SeNPs) were potentiostatically formed at room temperature (298 K) on the surface of a glassy carbon electrode (GCE) from SeO₂ dissolved in ethaline, a deep eutectic solvent composed of choline chloride and ethylene glycol. The mechanisms and kinetics of SeNP electrochemical nucleation and growth on GCE were investigated using both potentiodynamic and potentiostatic techniques. From cyclic voltammetry, the equilibrium potential (Eeq) of the Se(IV)/Se(0) redox couple, the exchange current density (j0), and the charge transfer coefficient (α) for the faradaic reaction Se(IV)ethaline + 4e−GCE/Se(0) $$\rightleftarrows$$ Se(s) were determined to be Eeq = 96 mV vs. Ag QRE, j0 = (1.2 ± 0.1) µA·cm⁻², and α = 0.4 ± 0.1. Analysis of the experimental potentiostatic current density transients (j–t plots) recorded at various overpotentials revealed that the SeNP electrodeposition mechanism involves three consecutive processes: (i) Adsorption and double-layer charging, (ii) Multiple 3D nucleation and diffusion-controlled growth of SeNPs, and (iii) Residual water reduction on the growing SeNP surfaces (2H2ODES + 2e− (Se) $$\rightleftarrows$$ H2(g) + 2OH− (DES)). The applied theoretical model enabled deconvolution of the total j–t response into these individual contributions, allowing for extraction of key kinetic parameters, including the SeNP nucleation frequency (A), the number density of active nucleation sites (N0), and the diffusion coefficient of Se(IV) in ethaline, DSe(IV) (298 K) = (4.91 ± 0.04) x 10− 9 cm2s− 1. Furthermore, from the dependence of A on overpotential, beside j0 and α, additional thermodynamic parameters were determined: the surface energy (σ), the critical nucleus size (nc), and the Gibbs free energy for the formation of the critical nucleus (ΔG(nc)) across the range of applied overpotentials. SEM analysis revealed the formation of smooth, quasi-spherical SeNPs with an average diameter of (118 ± 26) nm, uniformly distributed across the GCE surface. High-resolution XPS spectra recorded in the Se 3d region confirmed the presence of selenium in its zero-valent state. The Raman spectrum displays characteristic signals at 236 and 141 cm⁻¹, indicating that the predominant allotropic form of selenium in the nanoparticles is trigonal Se. Additionally, the optical band gap of the electrodeposited film was estimated using UV–Vis spectroscopy and the Kubelka–Munk method. A band gap of 1.7 eV was obtained, which is consistent with previously reported values for trigonal Se nanoparticles.

Platelet-rich plasma (PRP) is a promising orthobiologic therapy for musculoskeletal pathologies. However, its clinical application is influenced by varying legal and regulatory frameworks across regions. This narrative review aims to discuss the regulatory and legal framework for PRP therapy in musculoskeletal pathologies in South America. The authors searched and reviewed contemporary literature on laws and regulations governing platelet-rich plasma use for musculoskeletal pathologies in South America in electronic databases, summarising the findings in a narrative review. PRP regulation in South America falls into three categories: (1) countries with clear regulatory frameworks (Argentina, Bolivia, Colombia, Peru), where PRP is legally recognised and governed by specific provisions; (2) countries with emerging or developing regulations (Chile, Ecuador, Paraguay, Suriname, Uruguay, Venezuela, Guyana), where PRP is indirectly regulated under broader blood or tissue laws; and (3) countries permitting PRP only for experimental or research purposes (Brazil). Despite regional efforts to align with international standards, significant disparities exist in legal clarity, safety protocols, and clinical guidelines. These inconsistencies pose risks such as unregulated medical tourism and hinder scientific progress. PRP in South America presents three distinct regulatory scenarios: clear, established regulations; emerging or developing frameworks; and use restricted to experimental or research contexts. While most countries align with international safety standards, significant variation persists in how orthobiologics are clinically governed. The future challenge is to unify these regulations and build an international consensus on processing standards that guarantee patient safety and quality, while enabling innovation and legal clarity for clinicians.

Given the promising therapeutic potential of VO(IV)-8-hydroxyquinoline complexes and their derivatives, due to their diverse biological activities, such as their anticancer, antidiabetic, and antimicrobial properties, this study aims to advance the field of solution chemistry by investigating the formation and speciation processes of binary and ternary complexes in aqueous media. The speciation of the oxovanadium(IV) complexes with 8-hydroxiquinoline (H8HQ, HL) as primary ligand, as well as different potentially secondary ligands such as: picolinic acid (HPic, HL), dipicolinic acid (H2Dipic, H2L), oxalic acid (H2Oxa, H2L), malonic acid (H2Mal, H2L), bipyridine (Bipy, L), and Phenanthroline (Phen, L) were studied by potentiometric measurements in 1.0 mol dm−3 NaCl at 25.0 °C. In order to obtain stability constants under our experimental conditions, a reexamination of the binary systems was performed, and the results obtained are consistent with those reported in the literature, despite variations in the ionic medium and concentration. The complexes VO(8HQ)(HL), VO(8HQ)(L), and VO(OH)(8HQ)(L) were identified for ternary systems; for clarity, charges have been omitted.

Casabe is a very old food. Historically, it was the Arawaks, aborigines from northern South America, who began to make it by hand. Its origin dates back to the 18th century, since this time people have talked about this delicacy in Venezuela and it is found within Venezuelan gastronomy because it is a traditional component that cannot be missing in most homes in our country. This thin, lightweight cake, derived from cassava, has been claimed for more than 3.000 years. Cassava has a variety of foods that are located in a privileged place, occupying a prominent space in the dietary consumption of Venezuelans since the 16th century. However, in Caracas it also has its place of honor. Hence, the objective of this study is: to make theoretical contributions about casabe, starting from its historical aspects, until reaching the facts that have contributed to its permanence over time and its growing consumption. The methodology is a bibliographic design, with features of transversality and descriptivism, while the type of research is documentary and its level is historical, since the past is analyzed, to give way to other aspects inherent to future constructs.

We describe a radioisotope-excited energy dispersive X-ray fluorescence spectrometric facility for the elemental analysis of minerals containing the rare earth elements (REEs) by the use of the K-line X-rays. Two 241Am sources are used in purpose-designed holders that fit a high-resolution solid-state germanium detector. The system is capable of exciting all the light actinides up to element 69, Tm. The analysis through the well-separated K-lines allows an easy identification of lanthanide elements with advantages over traditional L-line detection particularly in mineral samples with high Fe concentration, enabling the recognition of most lanthanide elements at values close to 10 ppm. We report the achieved elemental sensitivity obtained with a set of pure element standards and spectra of mineral concentrates derived from a REEcontaining Venezuelan Laterite.