University of Antofagasta

In this work, we investigate the finite-bias charge current, shot noise, and Fano factor in an Aharonov-Bohm interferometer composed of two parallel quantum dots, each side-coupled to a topological superconducting nanowire represented by an effective Kitaev chain hosting Majorana bound states at its ends. The transport properties are calculated using the nonequilibrium Green's function formalism within the equation-of-motion approach. Our results show that coupling to the Majorana bound states significantly modifies the interference pattern, producing distinctive signatures in the current, shot noise, and Fano factor. These signatures are particularly pronounced at the half-flux condition, where destructive interference suppresses the conventional transport background and enhances the visibility of Majorana-assisted transport. These findings demonstrate that finite-bias shot-noise spectroscopy provides a sensitive indirect probe of Majorana bound states in hybrid superconducting-nanowire interferometers.

Silvered-glass mirrors represent the state of the art in concentrated solar thermal systems. Compared with polymer-or aluminum-based reflector materials, these mirrors offer clear technological advantages, including high solar reflectance of approximately 94.5% combined with low angular scattering (< 3 mrad). In addition, they have become increasingly cost-effective, with prices as low as approximately & euro;12 m-2, depending primarily on production volume and energy costs. Silvered-glass mirrors have also demonstrated excellent long-term durability under field conditions. For instance, mirrors installed in the Solar Energy Generating Systems (SEGS) power plants constructed in the United States during the 1980s have operated for more than 30 years with only minimal reflectance losses. The high corrosion resistance of silvered-glass mirrors is largely attributed to passivating, lead-containing pigments used in their protective coatings. However, the paint and printing ink industries have been pursuing the elimination of lead from their formulations at national, European, and international levels to reduce exposure to toxic and carcinogenic lead compounds. The mirror industry is therefore likely to be affected by forthcoming restrictions or bans on lead-based pigments, following regulatory measures already implemented in the PVC sector. These developments have resulted in a significant contraction of the lead pigment market and a substantial increase in material costs. Consequently, the development of lead-free protective coating systems for solar mirrors is required, both to address environmental and health concerns and to mitigate the risk associated with potential regulatory bans. In this study, lead-free protective coatings for solar mirrors were developed and applied to silvered and coppered glass substrates under both laboratory-scale and industrial manufacturing conditions. The resulting samples were evaluated under outdoor exposure at eight distinct sites for periods of up to eight years, as well as under accelerated aging in climatic chambers. Their corrosion resistance was benchmarked against that of lead-containing reference coatings, and the corresponding service lifetimes were estimated.

This work presents an extended Pitzer model for the simultaneous representation of ionic speciation and thermodynamic properties in the quaternary reciprocal Cu-Na-Cl-SO 4 -H 2 O system and its binary and ternary subsystems. The model was calibrated using literature water activity, osmotic coefficient, vapor pressure, and solid-liquid equilibrium data over 273.15-373.15 K for the binary and ternary subsystems, and at 298.15 K for the quaternary system. Explicit association equilibria were considered for CuSO 4 (aq), CuCl + , CuCl 2 (aq), NaSO 4- , and NaCl(aq), allowing the description of sulfate/chloride complexation effects in concentrated aqueous electrolytes. New Pitzer interaction parameters were obtained for the sodium-containing binary systems, selected ternary systems, and the quaternary reciprocal system. The temperature dependence of the solubility product of CuSO 4 & sdot;Na 2 SO 4 & sdot;2H 2 O(cr) was also determined from 273.15 to 333.15 K. The model reproduced the experimental data with low combined relative standard deviations and yielded lower AIC, AIC c , and BIC values than selected literature Pitzer parameterizations. Speciation calculations showed that increasing chloride concentration strongly promotes Cu(II) chloro-complexation. In the CuSO 4 + NaCl + H 2 O reciprocal composition at 298.15 K, CuCl + reached a maximum fraction of 87.8 % at m(NaCl) = 2.22 mol & sdot;kg -1 , followed by increasing formation of CuCl 2 (aq). The proposed formulation provides a consistent thermodynamic framework for concentrated sulfate/ chloride media relevant to copper hydrometallurgy.

The development of efficient and durable electrocatalysts requires precise control over noble-metal utilization and catalyst morphology to enhance hydrogen evolution reaction kinetics and mechanical stability. In this study, palladium was electrodeposited onto titanium substrates by potentiostatic pulse electrocrystallization to tailor nanoparticle size and catalytic performance. Deposition parameters, including precursor concentration, applied potential, and pulse duration (ton/toff), were systematically varied, including charge-controlled experiments. Morphological analysis revealed nanogranular coatings with different degrees of surface continuity, compatible with a three-dimensional Volmer–Weber growth mode. Electrochemical characterization in alkaline medium showed apparent Tafel slopes in the range of 167–277 mV·dec⁻¹ and significant variations in exchange current density, with overpotentials as low as 178 mV at 10 mA cm⁻². An apparent electrochemically accessible area was estimated from palladium oxide reduction charge, allowing comparison between geometric and area-normalized exchange current densities. The results indicate that enhanced hydrogen evolution reaction performance may arise either from increased accessible surface area or from more efficient utilization of active sites. These findings demonstrate that pulse-controlled electrodeposition enables tuning of both morphology and electrocatalytic behavior, providing practical guidelines for the design of Pd-based electrodes for alkaline electrolysis.

Natural hypobaric hypoxia is a defining feature of high-altitude environments and may alter human motor strategies during repetitive work tasks. This study investigated whether acute exposure and 48 h of continuous natural hypobaric hypoxia modify movement variability during a standardized, submaximal upper-limb reaching task in healthy lowlanders. Ten adults performed a 180 s paced reaching–retrieving task (1 Hz) under three conditions: normobaric normoxia at sea level, acute natural hypobaric hypoxia within 3 h of arrival at 3,600 m, and after 48 h of continuous exposure at 3,600 m. Wrist triaxial acceleration was recorded and processed offline to quantify linear variability metrics (mean acceleration, acceleration standard deviation, root mean square) and nonlinear metrics (sample entropy, maximum Lyapunov exponent) across movement axes, directions, and phases. Multivariate analyses showed significant effects of condition (p < 0.001), axis (p < 0.001), and phase (p = 0.007), as well as significant condition-by-axis (p = 0.016) and condition-by-phase (p = 0.003) interactions. Compared with sea level, hypobaric hypoxia increased acceleration magnitude in task-relevant axes and reduced variability in non-primary axes and early movement phases, whereas nonlinear metrics remained unchanged. These findings suggest that natural hypobaric hypoxia selectively redistributes linear movement variability during repetitive upper-limb performance.