National University of San Luis

Disposal of discarded photovoltaic solar panels has emerged as a significant environmental concern as they are classified as hazardous electronic waste. However, significant benefits can be gained by strategically recovering valuable materials from this waste. The objective of this study was to utilize aluminum recovered from the frame of a discarded PV solar panel to synthesize magnesium aluminate spinel (MgAl2O4). The synthesis method investigated involved chlorination roasting, employing bischofite (MgCl2·6H2O) as the chlorinating agent. Initially, the frame was separated from the discarded panel, size-reduced and subjected to leaching. The resulting powder was then mixed with bischofite. The mixture was calcined under isothermal and non-isothermal conditions to investigate the influence of temperature and reaction time on the synthesis. Additionally, the effect of the chlorination roasting atmosphere, including air and nitrogen atmospheres, was assessed. Different studies, including thermodynamic calculations, X-ray diffractometry (XRD), and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) were conducted to elucidate the reactions and mechanism involved in the synthesis process. The results showed that AlOOH, Al2O3·H2O, Mg3(OH)5Cl·4H2O and Mg2(OH)3Cl·4H2O are the intermediate products generated during the synthesis process. Magnesium aluminate spinel begins to form at 700 °C, with the optimal operating conditions identified at 700 °C and 120 min.

The Bebedero tectonic depression in San Luis province, Argentina, is a closed drainage basin that has formed as a result of block‐faulting and rifting processes. The Bebedero lake exhibits notable similarities to the endorheic watersheds of the western United States, particularly those of Death Valley, the Saline Valley and, to a lesser extent, the Great Salt Lake. While it is currently classified as a playa lake, there is evidence of lake levels near the sill that overflowed during the Late Pleistocene. Several lines of evidence suggest that climate is the major controlling factor in the basin's fill. The Salina del Bebedero Basin is an underfilled lake basin type, particularly a discharge lake basin. This assertion is supported by recent findings, including precise topography, stratigraphy, facies associations, radiocarbon ages and palaeontology from one section and two transects. The following presentation comprises stratigraphic correlations, palaeoenvironmental reconstructions and a graphical model of lake stages based on these new results and previously published research. This paper provides a model of lake‐level fill from the Late Pleistocene to the present, identifying distinct highstands and lowstands associated with global climate events. The surface and depth of the lake were reconstructed for each stage. The maximum expansion was estimated at 1000 km² during the Pre‐Last Glacial Maximum and 782.6 km² during the Last Glacial Maximum, with depths ranging from 60 to 75 m. Lake Bebedero exhibited similar lake‐level responses to climate variations as Lake Bonneville, Great Salt Lake, as well as sub‐environmental similarities with Death Valley and the Saline Valley. In addition to its palaeoclimate significance, Lake Bebedero has archaeological records of an early settlement dating back ca 10 to 6 cal ka BP. The scarcity of data concerning the early human settlement in southern South America makes archaeological evidence relevant. Therefore, the inferences regarding climate and environment derived from studies of the lake provide important information about the first human groups to populate these regions.

Rare diseases (RDs) are a group of pathologies that individually affect less than 1 in 2000 people but collectively impact around 7% of the world’s population. Most of them affect children, are chronic and progressive, and have no specific treatment. RD patients face diagnostic challenges, with an average diagnosis time of 5 years, multiple specialist visits, and invasive procedures. This ‘diagnostic odyssey’ can be detrimental to their health. Machine learning (ML) has the potential to improve healthcare by providing more personalized and accurate patient management, diagnoses, and in some cases, treatments. Leveraging the MIMIC-III database and additional medical notes from different sources such as in-house data, PubMed and chatGPT, we propose a labeled dataset for early RD detection in hospital settings. Applying various supervised ML methods, including logistic regression, decision trees, support vector machine (SVM), deep learning methods (LSTM and CNN), and Transformers (BERT), we validated the use of the proposed resource, achieving 92.7% F-measure and a 96% AUC using SVM. These findings highlight the potential of ML in redirecting RD patients towards more accurate diagnostic pathways and presents a corpus that can be used for future development and refinements.

Biomass from agro-industrial waste is a vital renewable resource for addressing energy and environmental challenges. Hydrothermal carbonization (HTC) is utilized to produce hydrochar from various materials, including these wastes, for environmental remediation and other industrial applications. In this work, the effects of temperature and treatment time on the solid and liquid obtained from the application of the HTC process to grape stalks were assessed. The energetic properties of the hydrochar, its physico-chemistry, and that of the activated carbons prepared with it were evaluated by proximate analysis, higher heating value (HHV), BET area, pore volume, FTIR, and SEM. Temperature significantly impacted the hydrochar’s mass yield (50%), while time had minimal effect. The hydrochars’ energy yield was about 70%, with an HHV value of 26.21 MJ/kg. The activated carbons produced from grape stalk hydrochar, using KOH and H3PO4, exhibited BET areas of 1630 and 1800 m²/g, respectively, highlighting their potential as adsorbents and or energetic applications. Meanwhile, the liquid fraction emerged as a potential source of antioxidant compounds due to the presence of phenols and flavonoids. The highest concentration of phenolic compounds (TPC) was obtained at 240 °C for 10 h TPC (1310.17 mM GAE/100 g dw), and the highest of flavonoids (TFC) at 180 °C for 2 h (39 mm QE/100 g dw). Antioxidant capacity was determined by DPPH scavenging activity and ferric-reducing antioxidant power assay (FRAP). These results present genuine possibilities for the technological application of the products derived from this simple process, pending the completion of complementary studies. Graphical Abstract

The rapid increase in electronic waste, driven by the widespread use of electronic devices, poses significant environmental challenges due to its classification as hazardous waste. Among these, end-of-life solar panels present a growing concern, as improper disposal can lead to the release of toxic pollutants. Recycling these panels not only prevents environmental contamination but also optimizes resource and energy use. This study focuses on repurposing silicon from discarded panels to synthesize cordierite, a material with industrial applications. The synthesis process involves the thermal treatment of silicon obtained from waste panels, combined with kaolinitic clay and bischofite, which acts as a chlorinating agent. Non-isothermal experiments were conducted within a temperature range of 20–900 °C to evaluate the effects of temperature on the reaction process and impurity behavior. Additionally, isothermal experiments were performed to assess the impact of reaction time. The reaction mechanism was also analyzed. The results revealed that cordierite begins to form at 700 °C through the reaction of evolved mullite and enstatite in a chlorine atmosphere. At 600 °C, iron impurities in the clay undergo chlorination, forming volatile FeCl₃. Optimal conditions for the process were identified at 900 °C with a reaction duration of 120 min, enabling the selective synthesis of cordierite and the effective removal of iron and vitreous silica impurities.

Clay-based monoliths with incorporation of active phases derived from the waste of the metallurgical and livestock industries (powdered iron and bone meal) and composite with both raw materials were synthesized by the extrusion process and used as adsorbents in the As(V) removal from aqueous solutions. These monoliths exhibited excellent mechanical properties compared to commercial ceramic-based monoliths, with potential for their use in continuous systems due to ease of handling and extraction of the adsorption medium (i.e., packed bed) and having defined meso and macroporosity. Specifically, the clay-based monoliths were obtained along with (i) active iron phases (hematite and magnetite), (ii) bone char and (iii) a combination of both materials. They showed As(V) adsorption capacities of up to 0.56, 3.4 and 8.0 mg g ⁻¹ at neutral pH and room temperature conditions. The proposed adsorption mechanism was associated with ligand exchange between the As(V) species and the hydroxyl functional groups, in addition to the presence of inner-sphere bidentate unprotonated arsenate surface complexes that was reflected in the formation of new absorption bands in Fourier Transform Infrared Spectroscopy spectra related to the Metal-O interaction and changes in the bands associated with the -OH groups. The SIPS isotherm model fitted the experimental data obtained at equilibrium and was related to strong adsorbent/adsorbate interactions and high surface heterogeneity. Finally, the composite ceramic monolith synthesized in the present study exhibits capabilities comparable to those reported in the literature, highlighting the low cost of raw materials, as well as its excellent mechanical properties and well-defined porosity.

A new mebendazolium di­hydrogen phosphate phospho­ric acid solid material was obtained and characterized by single-crystal X-ray diffraction and complementary solid-state techniques {systematic name: 5-benzoyl-2-[(meth­oxy­carbon­yl)amino]-1H-1,3-benzo­diazol-3-ium di­hydrogen phosphate–phos­pho­ric acid (1/1), C16H14N3O3⁺·H2PO4⁻·H3PO4}. Structure solution confirmed proton transfer from phospho­ric acid towards the basic imidazole ring of mebendazole. The mebendazolium cation and the di­hydrogen phosphate anion assemble in the solid state in a cyclic hydrogen-bond-driven supra­molecular motif, as observed in all mebendazolium/oxyanions structures reported in the literature. This salt crystallizes in the monoclinic P21/c (No. 14) space group. A detailed study of the crystal structure performed by atom-to-atom and global Hirshfeld surface analysis indicates that several hydrogen bonds act as the main inter­molecular inter­actions stabillizing the material. The new material is stable up to 458 K.

How important is the support during the rational design of a catalyst? Herein, doped ceria (Zr; Pr and Tb) was used as an active support to prepare Pt catalysts (0.5 wt%) for glycerol selective oxidation. A thorough characterization of achieved catalytic systems showed that the nature of doping elements led to different physicochemical properties. The presence of surface Pr³⁺ and Tb³⁺ not only increased oxygen vacancies but also electron mobility, modifying the oxidation state of platinum particles. The redox properties of the catalyst were also affected, achieving a close interaction between the support and metal particles even in the form of Pt-O-Pr(Tb) solid solutions. Furthermore, the combination of medium-sized metal particle dispersion, strong metal–support interaction and a synergy between the amount of oxygen vacancies and Pt⁰, observed in the Pt/CeTb catalyst, led to a high turnover frequency (TOF) and increased selectivity to glyceric acid. Thus, the present study reveals how a simple structural modification of active supports, such as cerium oxide, by means of doping elements is capable of improving the catalytic performance during glycerol selective oxidation, avoiding the cumbersome methods of synthesis and activation treatments.

In the problem of allocating a single non-disposable commodity among agents whose preferences are single-peaked, we study a weakening of strategy-proofness called not obvious manipulability (NOM). If agents are cognitively limited, then NOM is sufficient to describe their strategic behavior. We characterize a large family of own-peak-only rules that satisfy efficiency, NOM, and a minimal fairness condition. We call these rules "simple". In economies with excess demand, simple rules fully satiate agents whose peak amount is less than or equal to equal division and assign, to each remaining agent, an amount between equal division and his peak. In economies with excess supply, simple rules are defined symmetrically. These rules can be thought of as a two-step procedure that involves solving a claims problem. We also show that the single-plateaued domain is maximal for the characterizing properties of simple rules. Therefore, even though replacing strategy-proofness with NOM greatly expands the family of admissible rules, the maximal domain of preferences involved remains basically unaltered.

Chemically tuned organic–inorganic hybrid halide perovskites based on bromide and chloride anions CH(NH2)2Pb(Br1−xClx)3 (CH(NH2)2+: formamidinium ion, FA) have been crystallized and investigated by neutron powder diffraction (NPD), single crystal X-ray diffraction (SCXRD), scanning electron microscopy (SEM) and UV–vis spectroscopy. FAPbBr3 and FAPbCl3 experience successive phase transitions upon cooling, lowering the symmetry from cubic to orthorhombic phases; however, these transitions are not observed for the mixed halide phases, probably due to compositional disorder. The band-gap engineering brought about by the chemical doping of FAPb (Br1-xClx)3 perovskites (x = 0.0, 0.33, 0.5, 0.66 and 1.0) can be controllably tuned: the gap progressively increases with the concentration of Cl− ions from 2.17 to 2.91 eV at room temperature, presenting a nonlinear behavior. This study provides an improved understanding of the structural and optical properties of these appealing hybrid perovskites.

Background Residency selection is crucial for enhancing the healthcare workforce. Most research on this topic arises from the global north, leaving a gap from the global south perspective. Hence, this study aimed to evaluate factors associated with the Peruvian National Residency Examination (ENARM) in Peruvian applicants. Methods A repeated cross-sectional analytical study was conducted using data from applicants to the Peruvian ENARM from 2019 to 2023. The data were sourced from the National Council of Medical Residency’s webpage and analyzed using descriptive statistics and linear mixed-effect models. Results The final population consisted of 28,872 (95.06%) of applicants between 2019 and 2023. The mean ENARM score was 11.69, with a pass rate of 61.6% if a standard setting was set at 11. The highest scores were seen in those who achieved scores above 13 in the ENAM and received honors in medical school, while the lowest in those who applied in the captive modality and did not take the ENAM. Most applicants were concentrated in Lima and applied to Surgery, Pediatrics, and Obstetric-Gynecology. The ENAM score was positively associated with the ENARM in the mixed model when adjusting for receiving, year, setting of application, modality, and application specialty. Conclusions ENAM scores and honors in medical school were most associated with ENARM; hypothetically, 4 out of 10 applicants would fail the ENARM. Moreover, we portrayed the disparities in Peruvian medical education that point toward the quality of medical education, its centralization in the Peruvian capital, and the power dynamics between specialties.

Background: Trihexyphenidyl (THP) has been widely used for over three decades as pediatric pharmacotherapy in patients affected by segmental and generalized dystonia. In order to achieve effective and safe pharmacotherapy for this population, new formulations are needed. Objective: The aim of this work is the development of trihexyphenidyl orodispersible minitablets (ODMTs) for pediatric use. Methods: Six different excipients were tested as diluents. The properties of powder mixtures were evaluated before direct compression and pharmacotechnical tests were performed on the final formulation. The determination of the API content, uniformity of dosage, and physicochemical stability studies were analyzed by an HPLC-UV method. Results: The developed ODMTs met pharmacopeia specifications for content, hardness, friability, disintegration, and dissolution tests. The physicochemical stability study performed over 18 months shows that API content remains within 90.0–110.0% at least for this period. Conclusions: These ODMTs will allow efficient, safe, and high-quality pharmacotherapy.