Abstracts In this work, the results of a detailed sound monitoring conducted during December 2023 in the mountain rainforest of Yungas (750 meters above sea level), in the vicinity of Piedras stream within the protected area of Sierra San Javier Park, are presented. The spectrograms obtained from the inner forest differ consistently from those of the riparian forest, distinguishable by their bioacoustic characteristics. It is conjectured that the stream, through its geophonic load and ecological imprint on the landscape, imposes restrictions on the occupation of the ecoacoustic niche by the fauna ensemble present in the area.

Resumen En este trabajo se presentan los resultados de un monitoreo sonoro detallado realizado durante diciembre de 2023 en selva montana de Yungas (750 msnm), en las proximidades del arroyo Piedras dentro del área protegida Parque Sierra San Javier. Los espectrogramas obtenidos bosque adentro difieren de los de bosque de ribera de forma consistente, discernible por sus biofonías. Se conjetura que el arroyo, a través de su carga geofónica e impronta ecológica en el paisaje, impone restricciones para la ocupación del nicho ecoacústico por parte del elenco faunístico presente en el área.

Abstract Rotary drums can show different granular flow regimes each one with its own specific flow behavior, which increase the complexity in their study. The way particles move inside the rotary drum is directly related to the mass and energy transfer rates, and consequently to the process performance. Thus, an experimental investigation regarding the transition between different flow regimes inside a rotary drum was carried out in the present work. To the best of our knowledge, the hysteresis phenomenon was observed for the first time in the transition between cataracting-centrifuging regimes, which was shown to be dependent on the physical properties of the particles such as sphericity, density and particle-wall friction coefficient. A new expression for the centrifuging critical rotation speed was proposed in this work.

An anaerobic sequencing batch biofilm reactor (AnSBBR) containing immobilized biomass and operating with recirculation of the liquid phase (total liquid volume 4.5 L; treated volume per cycle 1.9 L) was used to treat sucrose-based wastewater at 30 ºC and produce biohydrogen. The influence of applied volumetric organic load was studied by varying the influent concentration at 3600 and 5400 mgCOD.L-1 and using cycle lengths of 4, 3 and 2 hours, obtaining in this manner volumetric organic loads of 9, 12, 13.5, 18 and 27 gCOD.L-1.d-1. Different performance indicators were used: productivity and yield of biohydrogen per applied and removed load, reactor stability and efficiency based on the applied and removed organic loads, both in terms of organic matter (measured as COD) and carbohydrate (sucrose). The results revealed system stability (32-37% of H2 in biogas) during biohydrogen production, as well as substrate consumption (12-19% COD; 97-99% sucrose). Conversion efficiencies decreased when the influent concentration was increased (at constant cycle length) and when cycle lengths were reduced (at constant influent concentrations). The best yield was 4.16 mol-H2.kg-SUC-1 (sucrose load) at 9 gCOD.L-1.d-1 (3600 mgCOD.L-1 and 4 h) with H2 content in the biogas of 36% (64% CO2 and 0% CH4). However, the best specific molar productivity of hydrogen was 8.5 molH2.kgTVS-1.d-1 (32% H2; 68% CO2; 0% CH4), at 18 gCOD.L-1.d-1 (5400 mgCOD.L-1 and 3 h), indicating that the best productivity tends to occur at higher organic loads, as this parameter involves the "biochemical generation" of biogas, whereas the best yield tends to occur at lower and/or intermediate organic loads, as this parameter involves "biochemical consumption" of the substrate. The most significant metabolites were ethanol, acetic acid and butyric acid. Microbiological analyses revealed that the biomass contained bacilli and endospore filaments and showed no significant variations in morphology between different experimental conditions.