The Atomic Oxygen Erosion Resistance Effect and Mechanism of the Perhydropolysilazane-Derived SiOx Coating Used on Polymeric Materials in Space Environment

In this work, the atomic oxygen (AO) erosion-resistance effect and mechanism of the Perhydropolysilazane (PHPS) coating were investigated from the perspective of element distribution in the depth direction. The results revealed that the coating demonstrated good adhesion and intrinsic AO erosion-resistance, which was attributed to the composition gradient formed in the coating. Moreover, the oxygen ratio of the SiOx on top layer of the coating could be elevated during AO exposure, strengthening the Ar ion etching durability of the coating. According to these results, an AO erosion-resistance mechanism model of the PHPS-derived SiOx coating was finally obtained.

Deep Exploration of the Planets HR 8799 b, c, and d with Moderate-resolution Spectroscopy

The four directly imaged planets orbiting the star HR 8799 are an ideal laboratory to probe atmospheric physics and formation models. We present more than a decade’s worth of Keck/OSIRIS observations of these planets, which represent the most detailed look at their atmospheres to date by its resolution and signal-to-noise ratio. We present the first direct detection of HR 8799 d, the second-closest known planet to the star, at moderate spectral resolution with Keck/OSIRIS (K band; R ≈ 4000). Additionally, we uniformly analyze new and archival OSIRIS data (H and K band) of HR 8799 b, c, and d. First, we show detections of water (H2O) and carbon monoxide (CO) in the three planets and discuss the ambiguous case of methane (CH4) in the atmosphere of HR 8799 b. Then, we report radial-velocity (RV) measurements for each of the three planets. The RV measurement of HR 8799 d is consistent with predictions made assuming coplanarity and orbital stability of the HR 8799 planetary system. Finally, we perform a uniform atmospheric analysis on the OSIRIS data, published photometric points, and low-resolution spectra. We do not infer any significant deviation from the stellar value of the carbon-to-oxygen ratio (C/O) of the three planets, which therefore does not yet yield definitive information about the location or method of formation. However, constraining the C/O for all the HR 8799 planets is a milestone for any multiplanet system, and particularly important for large, widely separated gas giants with uncertain formation processes.

The First Retrieval of a Substellar Subdwarf: A Cloud-free SDSS J125637.13–022452.4

We present the first retrieval analysis of a substellar subdwarf, SDSS J125637.13−022452.4 (SDSS J1256−0224), using the Brewster retrieval code base. We find SDSS J1256−0224 is best fit by a cloud-free model with an ion (neutral H, H−, and electron) abundance corresponding to Fe / H ion = − 1.5 . However, this model is indistinguishable from a cloud-free model with Fe / H ion = − 2.0 and a cloud-free model with Fe / H ion = − 1.5 assuming a subsolar carbon-to-oxygen ratio. We are able to constrain abundances for H2O, FeH, and CrH, with an inability to constrain any carbon-bearing species likely due to the low metallicity of SDSS J1256−0224. We also present an updated spectral energy distribution (SED) and semiempirical fundamental parameters. Our retrieval- and SED-based fundamental parameters agree with the Baraffe low-metallicity evolutionary models. From examining our “rejected” models (those with ΔBIC > 45), we find that we are able to retrieve gas abundances consistent with those of our best fitting model. We find the cloud in these poorer fitting “cloudy” models is either pushed to the bottom of the atmosphere or made optically thin.

Upscaling Severe Torrefaction of Agricultural Residues to Produce Sustainable Reducing Agents for Non-Ferrous Metallurgy

Torrefaction of almond shells and olive stones, which are typically considered agricultural waste in the southern regions of the European Union, was investigated in this work for application as reducing agents in the metallurgical industry. Four different temperatures were tested: 250, 280, 300 and 350 °C. The evolution of the solid yields with the temperature was determined with TGA measurements. This showed that the duration of torrefaction should not exceed 45 min. The kinetic profiles were successfully fitted using the pseudo-first-order rate equation (PFORE). Then, torrefaction for 45 min was systematically carried out at every temperature and for each resource in a laboratory-scale batch device. The raw and torrefied biomasses were characterized using proximate, ultimate and calorific analyses. The carbon/oxygen ratio and the heating values were increased as a result of the torrefaction severity (from 20 MJ/kg for both raw biomasses to 30 MJ/kg at 350 °C). The highest mass losses were obtained at the highest temperature (67.35 and 65.04 %w for almond shells and olive stones, respectively, at 350 °C). The fixed carbon value also increased, being higher than 67 %w for torrefaction at 350 °C. The large-scale torrefaction at 350 °C (45 min) of these biomasses was carried out in a continuous pilot plant. The solids were characterized as well, and their properties were close to those of the biomasses torrefied in the laboratory-scale batch reactor under the same conditions. This thermal treatment provided biochars with all the required properties to be used as reducing materials in metallurgy.

Fabrication of Highly Porous and Pure Zinc Oxide Films Using Modified DC Magnetron Sputtering and Post-Oxidation

Porous films of metals and metal oxides exhibit larger surface areas and higher reactivities than those of dense films. Therefore, they have gained growing attention as potential materials for use in various applications. This study reports the use of a modified direct current magnetron sputtering method to form porous Zn-ZnO composite films, wherein a subsequent wet post-oxidation process is employed to fabricate pure porous ZnO films. The porous Zn-ZnO composite films were initially formed in clusters, and evaluation of their resulting properties allowed the optimal conditions to be determined. An oxygen ratio of 0.3% in the argon gas flow resulted in the best porosity, while a process pressure of 14 mTorr was optimal. Following deposition, porous ZnO films were obtained through rapid thermal annealing in the presence of water vapor, and the properties and porosities of the obtained films were analyzed. An oxidation temperature of 500 °C was optimal, with an oxidation time of 5 min giving a pure ZnO film with 26% porosity. Due to the fact that the films produced using this method are highly reliable, they could be employed in applications that require large specific surface areas, such as sensors, supercapacitors, and batteries.

Evaluation of Microalgae’s Plastic Biodeterioration Property by a Consortium of Chlorella sp. and Cyanobacteria sp.

Malaysia is one of the top eight countries that has a drawback of mismanaged plastic waste. This study intended to investigate polymer degradation using the biological technique with the help of microalgae to minimise the time required for biodegradation. This research article aims to identify the collected sample with the most suitable microalgae for the biodegradation of microplastic and to analyse the biodegradation of the polymer by microalgae. The results revealed that the consortium of Chlorella sp. and Cyanobacteria sp. were able to deteriorate low-density polyethene (LDPE sample) through several stages, and this was confirmed by UV-Spec, FESEM, EDX, CHNO, FTIR and DSC analysis. The results obtained revealed that microalgae producing exopolysaccharides (EPS) decreased the carbon and oxygen ratio. According to SEM micrographs, microalga may colonise, agglomerate, and adhere microplastics to its surface, regardless of its fractional size. The EDX analysis showed that the initial composition of carbon was 92.30 ± 1.23 %, while after the incubation, the carbon composition started decreasing from 53.18 % to 39.12 ± 1.08 %. Finally, there was a 37.91 % decrease in carbon weight from elemental analysise

Electronic Transport Mechanisms Correlated to Structural Properties of a Reduced Graphene Oxide Sponge

We report morpho-structural properties and charge conduction mechanisms of a foamy “graphene sponge”, having a density as low as ≈0.07 kg/m3 and a carbon to oxygen ratio C:O ≃ 13:1. The spongy texture analysed by scanning electron microscopy is made of irregularly-shaped millimetres-sized small flakes, containing small crystallites with a typical size of ≃16.3 nm. A defect density as high as ≃2.6 × 1011 cm−2 has been estimated by the Raman intensity of D and G peaks, dominating the spectrum from room temperature down to ≃153 K. Despite the high C:O ratio, the graphene sponge exhibits an insulating electrical behavior, with a raise of the resistance value at ≃6 K up to 5 orders of magnitude with respect to the room temperature value. A variable range hopping (VRH) conduction, with a strong 2D character, dominates the charge carriers transport, from 300 K down to 20 K. At T < 20 K, graphene sponge resistance tends to saturate, suggesting a temperature-independent quantum tunnelling. The 2D-VRH conduction originates from structural disorder and is consistent with hopping of charge carriers between sp2 defects in the plane, where sp3 clusters related to oxygen functional groups act as potential barriers.

Electronic Transport Mechanisms Correlated to Structural Properties of a Reduced Graphene Oxide Sponge

We report morpho-structural properties and charge conduction mechanisms of a foamy &ldquo;graphene sponge&rdquo;, having a density as low as &asymp; 0.07 kg/m3 and a carbon to oxygen ratio C:O ≃ 13:1. The spongy texture analysed by scanning electron microscopy is made of irregularly-shaped millimetres-sized small flakes, containing small crystallites with a typical size of ≃ 16.3 nm. A defect density as high as ≃ 2.6&times;1011 cm&minus;2 has been estimated by the Raman intensity of D and G peaks, dominating the spectrum from room temperature down to ≃ 153 K. Despite the high C:O ratio, the graphene sponge exhibits an insulating electrical behavior, with a raise of the resistance value at ≃ 6 K up to 5 orders of magnitude with respect to the room temperature value. A variable range hopping (VRH) conduction, with a strong 2D character, dominates the charge carriers transport, from 300 K down to 20 K. At T&amp;lt; 20 K, graphene sponge resistance tends to saturate, suggesting a temperature-independent quantum tunnelling. The 2D-VRH conduction originates from structural disorder and is consistent with hopping of charge carriers between sp2 defects in the plane, where sp3 clusters related to oxygen functional groups act as potential barriers.

Role of SpO2/FiO2 Ratio and ROX Index in Predicting Early Invasive Mechanical Ventilation in COVID-19. A Pragmatic, Retrospective, Multi-Center Study

The ability of COVID-19 to compromise the respiratory system has generated a substantial proportion of critically ill patients in need of invasive mechanical ventilation (IMV). The objective of this paper was to analyze the prognostic ability of the pulse oximetry saturation/fraction of inspired oxygen ratio (SpO2/FiO2) and the ratio of SpO2/FiO2 to the respiratory rate–ROX index–as predictors of IMV in an emergency department in confirmed COVID-19 patients. A multicenter, retrospective cohort study was carried out in four provinces of Spain between March and November 2020. The discriminative power of the predictive variable was assessed through a prediction model trained using a derivation sub-cohort and evaluated by the area under the curve (AUC) of the receiver operating characteristic (ROC) on the validation sub-cohort. A total of 2040 patients were included in the study. The IMV rate was 10.1%, with an in-hospital mortality rate of 35.3%. The performance of the SpO2/FiO2 ratio was better than the ROX index–AUC = 0.801 (95% CI 0.746–0.855) and AUC = 0.725 (95% CI 0.652–0.798), respectively. In fact, a direct comparison between AUCs resulted in significant differences (p = 0.001). SpO2 to FiO2 ratio is a simple and promising non-invasive tool for predicting risk of IMV in patients infected with COVID-19, and it is realizable in emergency departments.