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Synthesis and characterization of heterogeneous catalysts (MgO, CaO/Zeolite-Y) via hydrothermal method for biodiesel production
No full textThe global energy crisis and increasing greenhouse gas emissions have driven the development of sustainable energy alternatives, among which biodiesel has gained considerable attention. However, conventional biodiesel production is often limited by homogeneous catalysts that suffer from separation difficulties, low reusability, and secondary waste generation. In this work, heterogeneous MgO and CaO supported Zeolite-Y catalysts were synthesized via a hydrothermal method to enhance metal dispersion and catalyst stability. Structural characterization by XRD confirmed the preservation of the Faujasite-Y framework after metal incorporation, whereas SEM and SEM–EDX analyses revealed a typical octahedral morphology and uniform distribution of MgO and CaO on the Zeolite surface. Acidity measurements verified the availability of active sites suitable for transesterification. The catalysts were evaluated in sono-transesterification of waste cooking oil with methanol at 65 °C for 2 h. MgO/Zeolite-Y achieved a biodiesel yield of 63.824%, while CaO/Zeolite-Y exhibited superior catalytic performance with a yield of 79.344%. The produced biodiesel complied with SNI 7182:2015 and ASTM D6751 standards. These results indicate that CaO/Zeolite-Y is a promising heterogeneous catalyst for biodiesel production, demonstrating superior performance compared to MgO/Zeolite-Y under optimised reaction conditions
Determination of Keratinase Activity using Chicken Feather DMSO extract and its optimization with Response Surface Methodology
No full textKeratinase is an enzyme capable of degrading keratin, exhibiting two activities: protease activity, which cleaves peptide bonds, and disulfide reductase activity, which reduces disulfide bonds (-S-S-). However, keratinase activity is often measured using casein as a substrate, even though casein lacks disulfide bonds and is therefore less suitable. The limited availability of effective keratin substrates highlights the need to develop a more appropriate alternative. This study aimed to extract keratin from chicken feathers, characterize the extract—focusing on peptide and disulfide bonds—and evaluate its effectiveness as a keratinase substrate using keratinase produced by Bacillus sp. MD24. The research was conducted in three stages: (1) extraction of keratin from chicken feathers, (2) production of keratinase, and (3) evaluation and optimization of chicken feather keratin as a substrate using Plackett-Burman Design (PBD) and Central Composite Design–Response Surface Methodology (CCD-RSM). Keratin was extracted with DMSO, and ATR-FTIR and EDX analyses confirmed the presence of characteristic functional groups (–C–O, –N–H, –C–N, –C– H, – C–S, –S–H, and –S–S), indicating successful extraction. Keratinase production was optimized using the One-Factor-at-a-Time (OFAT) method, with optimal conditions identified at a temperature of 37°C and pH 8. Keratinase activity was then tested with casein, chicken feather keratin, and azure keratin. CCD-RSM analysis predicted the following optimal conditions: 56.64 °C and pH 8.02 for casein, 63.07 °C and pH 8.14 for chicken feather keratin, and 53.07 °C and pH 7.97 for azure keratin. Although additional data are needed in PBD to address the lack of fit and in CCD-RSM to evaluate the significance of temperature and pH interactions, the findings demonstrate that keratin extracted from chicken feathers can serve as a viable substrate for keratinase activity assays
Influence of physical, breathing, and vocal exercises in vocalists on the central regulation of changes in heart rate variability parameters
No full textThe autonomic nervous system is a complex multicomponent regulatory mechanism that constantly balances the state of the body depending on external factors, organic processes, and stressful situations. It is known that the autonomic nervous system has regulatory centers in the brain that are connected or influenced by other parts of the brain, including the cortex. In this regard, despite the well-understood and well-known reactions and methods of regulating the state of the body, we can in practice and in research obtain atypical reactions of the autonomic nervous system due to complex cerebral regulation. This article presents a study on how a person's vegetative state changes depending on the performance of physical breathing and vocal exercises. The state of the ANS was objectively assessed by analyzing heart rate variability (HRV) with the recording of indicators before and after exercise. Possible ways of obtaining such reactions have also been theoretically substantiated through complex regulation by various parts of the brain (including cortical structures) involved in motor control, respiratory rhythmogenesis, and vocal function, as well as with the modulating influence of the external environment. he results showed a statistically significant dynamics of HRV parameters, which indicates a purposeful change in the balance of sympathetic and parasympathetic tone
Dossier « Les professionnels de la montagne face aux transitions socio-environnementales » – « Les gardiens, depuis toujours, ils s’adaptent aux conditions climatiques » : adaptation ou évolution professionnelle, les gardiens de refuge de montagne face au changement climatique
No full textL’activité de gardien de refuge de montagne est directement impactée par les effets du changement climatique : pénurie d’eau, destruction partielle ou totale des sentiers d’accès, événements climatiques extrêmes… De même, les besoins émergents des usagers créent de nouvelles tensions pour l’équipe de travail. Néanmoins, les stratégies d’adaptation socio-environnementale ne constituent qu’une partie des explications des évolutions des pratiques du métier. La complexification et la multiplication des tâches de travail sont issues de différents facteurs externes au groupe professionnel, mais également à des dynamiques internes. Ainsi, la structuration de l’activité en métier et l’évolution des profils des gardiens sont à l’origine de l’émergence de nouvelles pratiques et d’une nouvelle organisation du travail
Faint red auroras as seen from Japan associated with intense magnetospheric compression
No full textWe report four low-latitude auroral events in 2024 as observed from Hokkaido, Japan (June 28, August 4, September 12, and November 9). These auroral events occurred during moderately intense magnetic storms, with the peak Dst index of approximately −110 nT, accompanied by significant magnetospheric compression. We estimate the altitudes of these red auroras to be > ~500 km, via widespread citizen science efforts. During the red aurora appearances in Japan, the ASYM-H index increased significantly to around 150 nT, which was approximately 1.3–2.0 times larger than the SYM-H peak amplitude for all events, suggesting that the actual storm intensities were underestimated. We further propose that the very dense solar wind of >~30 /cc is a key for causing the majority of extended red auroras during moderately intense magnetic storms, possibly via the stronger-than-usual enhancement of the atmospheric Joule heat in the subauroral latitude
The MUSE Ultra Deep Field (MUDF). VIII. The cool gas distribution surrounding galaxies at redshifts z≈ 0.5-2
No full textWe use deep MUSE data from the MUDF survey to investigate the cool gas around galaxies at redshifts 0.5 łesssim z łesssim 2. We constructed two samples: one sample for a down-the-barrel analysis, probing outflows via ( ) absorption against galaxy continua, and the other sample for projected galaxy pairs to examine the gas around the foreground galaxies in the transverse direction. From down-the-barrel stacked spectra, we detected blueshifted ( ) absorption, indicative of outflows, in which the absorption strength increases with stellar mass and star formation rate. Lower-mass galaxies exhibit weaker absorption, but higher outflow velocities, whereas higher-mass systems retain more cool gas with slower outflows. In the transverse direction, the absorption of ( ) decreases with the impact parameter, following a shallow profile. Comparing observations with radiative transfer models, we found that extrapolating an expanding halo model constrained with down-the-barrel measurements to halo scales overestimates the observed equivalent widths, likely due to the outflow geometry and the absence of the interstellar medium in the model. Our results highlight that mass, outflow geometry, and gas retention shape the cool circumgalactic medium, and that the combination of absorption and emission diagnostics provides powerful constraints on the properties of the cold halo gas. Mg II Mg II Mg I
Spatial variability of CH_4 and C_2H_2 absorptions in Jupiter’s auroral regions from Juno-UVS observations
No full textUltraviolet (UV) auroral emissions on Jupiter offer a unique window into the coupling between the planet's magnetosphere and upper atmosphere. Color ratios derived from molecular hydrogen emissions provide valuable diagnostics for the energy of precipitating electrons and the structure of the auroral atmosphere.
We aim to characterize the horizontal and vertical variability of hydrocarbon absorption in Jupiter’s auroral atmosphere using UV data from the Juno-UVS spectrograph and to investigate potential departures from the expected structure.
We constructed color ratio maps sensitive to CH_4 and C_2H_2 absorptions for two of Juno’s close approaches to Jupiter, perijoves (PJs) 6 and 10, by integrating auroral H_2 emission over hydrocarbon-sensitive spectral intervals. For CH_4, we redefined the absorbed spectral band, replacing the traditionally used 125–130 nm interval with 135–140 nm to mitigate higher order calibration issues. In regions of intense auroral brightness, we developed a correction method to account for spectral distortion due to detector nonlinearities at high fluxes.
The CH_4 and C_2H_2 absorptions generally follow the expected vertical distribution, with the CH_4 density extending to higher altitudes than C_2H_2. However, several localized regions show unexpected spatial distribution of the absorption. In PJ6, such anomalies are attributed to instrumental nonlinearities. Following the correction, the CR distributions become consistent with standard hydrocarbon vertical distributions. In PJ10, however, some anomalous patterns persist despite the correction. Spectral modeling studies indicate that these can be explained by modifying the relative abundances of CH_4 and C_2H_2, suggesting horizontal compositional variability and possible deviations in the homopause altitude between species.
Our results confirm that hydrocarbon absorption in Jupiter’s aurora is vertically stratified, but that the altitude of this stratification itself varies horizontally with latitude and longitude. These findings underscore the importance of accounting for local atmospheric composition when interpreting UV auroral spectra and retrieving electron energy distributions. Juno-UVS thus provides a powerful diagnostic for probing both the auroral precipitation and upper atmospheric structure. The framework developed here enables more accurate retrievals of electron energies and provides new constraints on the spatial variability of Jupiter's upper atmosphere. A systematic application to the full Juno dataset will offer deeper insights into the temporal and spatial dynamics of the Jovian aurora
Weak S-type asteroids compared to C-type explain the observed size distribution of the main belt
No full textThe main belt, the region between the orbits of Mars and Jupiter, is home to more than 1 million asteroids. These asteroids form orbital groups, (i.e., asteroid families formed by collisions) and also spectral groups (taxonomies) with different chemical compositions, in particular carbonaceous (C-types) and silicate (S-types). In this paper, we extend the existing main-belt collisional model by finding the appropriate strength-versus-size dependence (also known as the scaling law) for these two groups. We used color indices and geometric albedos of 56 and 72 spectroscopically confirmed C- and S-types (control samples), along with statistical methods on 1,065,034 asteroids, to assign C-, S-, or other types. This allowed us to construct observed size-frequency distributions (SFDs) for several subpopulations constrained by either semimajor axis (inner, middle, outer) or taxonomy (C, S, other). Then we used a Monte Carlo collisional model to compute the long-term collisional evolution (4.5 billion years) and derive synthetic SFDs. Our best-fit scaling laws indicate that S-types must be weaker below approximately 0.2, than C-types to explain the deficiency of asteroids in the inner part of the main belt near (and below) the observational limit. This may correspond to differences in chemical composition or material porosity. Future research will focus on the scaling laws of asteroids with rare or "extreme" taxonomies (e.g., V, M)
Non-common path aberration compensation and a dark hole loop with a pyramid adaptive optics system: Application to SAXO+
No full textIn ground-based high-contrast instruments, residual aberrations known as non-common path aberrations (NCPAs) limit detection performance, as they are unseen by the adaptive optics (AO) wavefront sensor but impact the astrophysical image, creating quasi-static speckles. SAXO+, the upgrade of the SAXO (SPHERE AO system) includes a second loop of AO downstream of the SAXO loop. This second loop is equipped with a near-infrared pyramid wavefront sensor whose nonlinearities, usually described with modal optical gains, might be challenging for removing quasi-static speckles.
We investigated two methods of quasi-static speckle removal : NCPA compensation and a dark hole loop, behind a pyramid AO system, measuring the interest of compensating for the pyramid optical gains.
We performed end-to-end numerical simulations of SAXO+ under various astrophysical conditions (seeing, star magnitude). We offset the pyramid wavefront sensor operating point to apply both the speckle suppression methods, calibrating or not calibrating the optical gains. We evaluated their performance by measuring the residual starlight in the coronagraph image.
A by-product of our study is an on-sky calibration method of measuring the pyramid optical gains. Non-common path aberration compensation reduces the residual starlight in the coronagraph image by a factor of up to 20 for seeing between 0.7" and 1" for a bright star and a factor of 2 at 0.7" for a faint star. Optical gains compensation enhances the performance at poor seeing and small pyramid modulation radius with a bright star, but shows a useless or even negative impact due to estimation inaccuracies at faint targets. On the other hand, the dark hole loop reduces the residual starlight by a factor of up to 200. The optical gain calibration enhances the dark hole performance behind a single pyramid AO system but is useless behind the SAXO+ system. Our parametric study gives baseline values for the efficient control of the dark hole loop for the SAXO+ system