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A direct pathway to convert orange peels waste to useful co-functionalized carbon quantum dots (CQDs) was performed through a friendly and efficient “greener method” consisting of a one-step microwave assisted solvothermal synthesis. The reaction proceeds in a mixture of powder of orange peels as precursor and water. The biomass was characterized by ICP-OES and CHONS analysis together with Fiber's analysis and FT-IR spectroscopy. The prepared CQDs presented a photoluminescent of brightness blue, high aqueous dispersion, chemical stability, an average particle size of 1.16 nm ± 0.1 nm and surface carboxylic and amine groups together with some dopants from the bio-precursor. The Fluorescence study revealed their potential emission in the electromagnetic spectrum of visible light. The bare mesoporous TiO2 semiconductor was impregnated with CQDs and the resultant composites presented a red-shift in the energy band gap with values from 2.3 eV to 2.08 eV, clearly lower than those on bare semiconductor and depending on the amount of CQDs. The CQDs/TiO2 photoelectrodes increased their photocurrent when they were exposed to the UV–Vis light, a decrease of photoelectrochemical band gap energy and an increase of the charge transfer constant in contrast with bare TiO2. These CQDs/TiO2 photoanodes were evaluated in carbon quantum dots-sensitized solar cells (CQDSSC) where there was an increase in the performance of the photovoltaic parameters compared with the bare semiconductor.

The optimal instant of observation of astrophysical phenomena for objects that vary on human time-sales is an important problem, as it bears on the cost-effective use of usually scarce observational facilities. In this paper we address this problem for the case of tight visual binary systems through a Bayesian framework based on the maximum entropy sampling principle. Our proposed information-driven methodology exploits the periodic structure of binary systems to provide a computationally efficient estimation of the probability distribution of the optimal observation time. We show the optimality of the proposed sampling methodology in the Bayes sense and its effectiveness through direct numerical experiments. We successfully apply our scheme to the study of two visual-spectroscopic binaries, and one purely astrometric triple hierarchical system. We note that our methodology can be applied to any time-evolving phenomena, a particularly interesting application in the era of dedicated surveys, where a definition of the cadence of observations can have a crucial impact on achieving the science goals., Accepted for publication to PASP. 23 pages, 2 Tables, 9 Figures, 2 Appendices

Carbon-based materials have been shown to enhance anaerobic digestion processes by promoting direct interspecies electron transfer in methanogenic consortia. However, little is known on their effects during the treatment of complex substrates, such as those derived from protein-rich wastewaters. Here, organic xerogels (OX) are tested, for the first time, as accelerators of the methanogenic activity of an anaerobic consortium treating a synthetic protein-rich wastewater. Three OX with distinct pore size distribution (10 and 1000 nm for OX-10 and OX-1000, respectively) and structural conformation (graphene oxide integration into OX-10-GO polymeric matrix) were synthesized. OX-1000 promoted the highest methane production rate (5.21 mL/g*h, 13.5% increase with respect to the control incubated without OX) among the synthesized OX. Additionally, batch bioreactors amended with OX achieved higher chemical oxygen demand (COD) removal (up to 88%) as compared to the control, which only showed 50% of COD removal. Interestingly, amendment of bioreactors with OX also triggered the production of medium-chain fatty acids, including caprylate and caproate. Moreover, OX decreased the accumulation of ammonium, derived from proteins hydrolysis, partly explained by their adsorption capacities, and probably involving their electron-accepting capacity promoting anaerobic ammonium oxidation. This is the first time that OX were successfully applied as methanogenic accelerators for the anaerobic treatment of synthetic protein-rich wastewater, increasing the methane production rate and COD removal as well as triggering the production of medium chain fatty acids and attenuating the accumulation of ammonium. Therefore, OX are proposed as suitable materials to boost the efficiency of anaerobic systems to treat complex industrial wastewaters., Universidad Nacional Autónoma de México (UNAM, PAPIIT grant TA100120 and UNAM, DGAPA Grant Number COIC/DDTPA/064/2020).

We present a Bayesian inference methodology for the estimation of orbital parameters on single-line spectroscopic binaries with astrometric data, based on the No-U-Turn sampler Markov chain Monte Carlo algorithm. Our approach is designed to provide a precise and efficient estimation of the joint posterior distribution of the orbital parameters in the presence of partial and heterogeneous observations. This scheme allows us to directly incorporate prior information about the system - in the form of a trigonometric parallax, and an estimation of the mass of the primary component from its spectral type - to constrain the range of solutions, and to estimate orbital parameters that cannot be usually determined (e.g. the individual component masses), due to the lack of observations or imprecise measurements. Our methodology is tested by analyzing the posterior distributions of well-studied double-line spectroscopic binaries treated as single-line binaries by omitting the radial velocity data of the secondary object. Our results show that the system's mass ratio can be estimated with an uncertainty smaller than 10% using our approach. As a proof of concept, the proposed methodology is applied to twelve single-line spectroscopic binaries with astrometric data that lacked a joint astrometric-spectroscopic solution, for which we provide full orbital elements. Our sample-based methodology allows us also to study the impact of different posterior distributions in the corresponding observations space. This novel analysis provides a better understanding of the effect of the different sources of information on the shape and uncertainty of the orbit and radial velocity curve., Comment: Accepted for publication to the Astronomical Journal.39 pages, 7 Tables, 18 Figures, two Appendices

Recently, the discovery of the corrosion-promoting effect of graphene has hindered the progress in the use of graphene-based materials as anticorrosive coatings. This work proposes to avoid the corrosion-promoting effect by the introduction of favorable defects to electrochemically reduced graphene oxide (ErGO), which consisted in the hydrogenation of sp2 domains during the removal of O-groups in graphene oxide, favoring sp3 domains and low conductivity. The ErGO films were subsequently modified with 4-pentyonate chains to obtain films with lower conductivity and enhanced hydrophobicity (HrGO). The alkyne chains were bonded to the remaining sp2 domains in ErGO by a simple electrochemical process. Both films were characterized by FT-IR, XPS, Raman spectroscopy and electrochemical methods. As anticorrosive coating, the HrGO film achieved a 4-times decrease in the corrosion current and showed a longer lifetime in comparison to the ErGO film, and an 18-times decrease compared to the bare carbon steel. According to the galvanic current measurements, neither of the films presented a corrosion-promoting effect, which was attributed to their low conductivity, 13 and 1.3 S cm−1 for ErGO and HrGO, respectively. These results show that the corrosion promoting effect of graphene can be avoided using correctly engineering ErGO with adequate defects.

In this work, physical and chemical analyses of 28 sawdust samples (tropical woods, pine woods, and oak woods) derived from the primary process of wood transformation and 4 samples of citrus residues were performed, as an option to make densified biofuels. The study included the determination of initial moisture, particle size distribution, proximate analysis, ultimate analysis, calculation of the calorific value, and ash microanalysis. The initial moisture content of the biomass samples ranged from 6.04 to 75.21%. The biomass granulometry results indicate that the highest proportion corresponds to the 1.0-mm (33.10%) (Fraction retained in mesh 0.5 mm). Other results obtained indicate the following ranges: ash content (0.27 to 6.27%), volatile matter (78.90 to 90.50%), fixed carbon (9.10 to 20.44%), carbon (49.13 to 50.78%), oxygen (42.62 to 44.49%), and hydrogen (5.24 to 6.55%). The calculated calorific value ranged from 17.65 MJ/kg to 20.72 MJ/kg. The chemical elements with the highest concentration in the biomass samples were K and Ca, followed in some cases by Al and P. The biomass with the greatest possibilities for making densified biofuels of better quality is the group of pine woods because they have low mineral content, low nitrogen content, and high calorific value.

Arsenic in groundwater for human consumption has negative effects on human's health worldwide. Due to the above, it is essential to invest in the development of new materials and more efficient technology for the elimination of such priority contaminants as arsenic. Therefore, in the present work, it was synthesized an amorphous hybrid material ZrOx-FeOx with a high density of OH groups, to improve the arsenic adsorption capacity of iron (FeOx) and zirconium (ZrOx) that makes up the bimetallic oxyhydroxide. The spectra of FT-IR and pKa's distribution suggest that in the synthesized binary oxides, a new union between the two metallic elements is formed by means of an oxygen (metal-O-metal). In addition, TEM profiles suggest that there are chemical interactions between both metals since no individual particles of iron oxide and zirconium oxide were found. According to the results, the adsorption capacity of the ZrOx-FeOx material increases 4.5 and 1.4 times with respect to FeOx and ZrOx, respectively. At pH 6, the maximum adsorption capacity was 27 mg g-1, but at pH greater than 7, the arsenic adsorption capacity onto ZrOx-FeOx decreased 66%. Graphical Abstract.

This study describes the effects of graphene oxide (GO) and reduced graphene oxide (rGO) on the acetoclastic, hydrogenotrophic and methylotrophic pathways of methanogenesis by an anaerobic consortium. The results showed that GO negatively affected the hydrogenotrophic and acetoclastic pathways at a concentration of 300 mg/L, causing a decrease of ~ 38% on the maximum specific methanogenic activity (MMA) with respect to the controls lacking GO. However, the presence of rGO (300 mg/L) promoted an improvement of the MMA (> 45%) achieved with all substrates, except for the hydrogenotrophic pathway, which was relatively insensitive to rGO. The presence of either rGO or GO enhanced the methylotrophic pathway and resulted in an increase of the MMA of up to 55%. X-ray photoelectron spectroscopy (XPS) analysis revealed that GO underwent microbial reduction during the incubation period. Electrons derived from substrates oxidation were deviated from methanogenesis towards the reduction of GO, which may explain the MMA decreased observed in the presence of GO. Furthermore, XPS evidence indicated that the extent of GO reduction depended on the metabolic pathway triggered by a given substrate.

A novel technology was developed for the treatment of a stainless steel wastewater, which contains high nitrate concentration (6.8 g N-NO3–/L), acidic pH (pH 3.3), and high concentration of metals....

We present orbital elements, orbital parallaxes and individual component masses, for fourteen spatially resolved double-line spectroscopic binaries derived doing a simultaneous fit of their visual orbit and radial velocity curve. This was done by means of a Markov Chain Monte Carlo code developed by our group, which produces posterior distribution functions and error estimates for all the parameters. Of this sample, six systems had high quality previous studies and were included as benchmarks to test our procedures, but even in these cases we could improve the previous orbits by adding recent data from our survey of southern binaries being carried out with the HRCam and ZORRO speckle cameras at the SOAR 4.1m and Gemini South 8.1m telescopes, respectively. We also give results for eight objects that did not have a published combined orbital solution, one of which did not have a visual orbit either. We could determine mass ratios with a typical uncertainty of less than 1%, mass sums with uncertainties of about 1% and individual component masses with a formal uncertainty of $0.01 M_\odot$ in the best cases. A comparison of our orbital parallaxes with available trigonometric parallaxes from Hipparcos and Gaia eDR3, shows a good correspondence; the mean value of the differences being consistent with zero within the errors of both catalogs. We also present observational HR diagrams for our sample of binaries, which in combination with isochrones from different sources allowed us to asses their evolutionary status and also the quality of their photometry., 26 pages, 8 figures. Accepted for publication in The Astronomical Journal

The speckle interferometry program at the the 4.1 m Southern Astrophysical Research Telescope (SOAR), started in 2008, now accumulated over 30,300 individual observations of 12,700 distinct targets. Its main goal is to monitor orbital motion of close binaries, including members of high-order hierarchies and low-mass dwarfs in the solar neighborhood. The results from 2021 are published here, totaling 2,623 measurements of 2,123 resolved pairs and non-resolutions of 763 targets. The median measured separation is 0.21", and 75 pairs were closer than 30 mas. The calibration of scale and orientation is based on the observations of 103 wide pairs with well-modeled motion. These calibrators are compared to the latest Gaia data release, and minor (0.5%) systematic errors were rectified, resulting in accurate relative positions with typical errors on the order of 1 mas. Using these new measurements, orbits of 282 binaries are determined here (54 first determinations and 228 corrections). We resolved for the first time 50 new pairs, including subsystems in known binaries. A list of 94 likely spurious pairs unresolved at SOAR (mostly close Hipparcos binaries) is also given., Comment: Accepted by AJ. 14 pages, 5 figures, 8 tables. Full electronic tables 2,3,6,7 are available at http://www.ctio.noirlab.edu/~atokovin/papers/SOAR2021-tables.tar.gz. arXiv admin note: text overlap with arXiv:2105.07040

Carbon-based materials have been shown to enhance anaerobic digestion processes by promoting direct interspecies electron transfer in methanogenic consortia. However, little is known on their effects during the treatment of complex substrates, such as those derived from protein-rich wastewaters. Here, organic xerogels (OX) are tested, for the first time, as accelerators of the methanogenic activity of an anaerobic consortium treating a synthetic protein-rich wastewater. Three OX with distinct pore size distribution (10 and 1000 nm for OX-10 and OX-1000, respectively) and structural conformation (graphene oxide integration into OX-10-GO polymeric matrix) were synthesized. OX-1000 promoted the highest methane production rate (5.21 mL/g*h, 13.5% increase with respect to the control incubated without OX) among the synthesized OX. Additionally, batch bioreactors amended with OX achieved higher chemical oxygen demand (COD) removal (up to 88%) as compared to the control, which only showed 50% of COD removal. Interestingly, amendment of bioreactors with OX also triggered the production of medium-chain fatty acids, including caprylate and caproate. Moreover, OX decreased the accumulation of ammonium, derived from proteins hydrolysis, partly explained by their adsorption capacities, and probably involving their electron-accepting capacity promoting anaerobic ammonium oxidation. This is the first time that OX were successfully applied as methanogenic accelerators for the anaerobic treatment of synthetic protein-rich wastewater, increasing the methane production rate and COD removal as well as triggering the production of medium chain fatty acids and attenuating the accumulation of ammonium. Therefore, OX are proposed as suitable materials to boost the efficiency of anaerobic systems to treat complex industrial wastewaters.

Bimetallic oxy(hydroxides) have gain great interest in water treatment systems based on adsorption processes. Their high OH groups density, in addition to inheriting the oxides properties make them highly promising adsorbents of anions. In this work, highly affine and selective bimetallic oxyhydroxides of cerium and iron (Ce:Fe-P's) for arsenic(V) were synthesized by implementing an assisted microwave methodology. The Ce:Fe-P's were characterized by various techniques (SEM, FTIR, XRD and XPS) and the As(V) adsorption capacity and kinetics as well as the effect of pH and the presence of coexisting anions were determined. The results showed that Ce:Fe-P's have an outstanding As(V) adsorption capacity (179.8 mg g

Nowadays, diesel desulfuration is of the utmost importance for the petrochemical industry in order to achieve efficient technologies for the production of clean fuels. Adsorption under normal conditions has the potential to produce ultra-low sulfur diesel if advanced materials capable of simultaneously removing both sulfur and nitrogen can be designed. This work contributes to the technology of clean fuels by using iron oxide-activated carbons (AC) that were produced with a microwave-assisted technique in the simultaneous adsorption of sulfur (dibenzothiophene and 4,6-dimethyldibenzothiophene) and nitrogen (indole and quinoline) compounds from model diesel fuel. Crystal habit was tailored with the addition of Mn-ions. The materials were characterized and their capacity was measured at batch and dynamic conditions. The use of Mn during Fe synthesis led to the deposition of reactive iron oxide twinning particles, while keeping most of the pore structure of the activated carbon. This modification allowed a higher total and simultaneous denitrogenation and desulfurization capacity and faster adsorption kinetics unlike iron and manganese modifications of activated carbon. Column dynamic experiments demonstrated that it is feasible to remove the adsorbates up to 200 bed volumes without reaching saturation of the adsorbent. The results demonstrated that twinned iron oxide particles deposited onto activated carbon were more reactive towards sulfur and nitrogen compounds. These particles were only obtained when Mn was present.

This research proposes two threated natural fibers (jute and henequen) as precursor alternative for the production of activated carbon cloth, and evaluates their performance for water treatment. Three activation methods were explored: physical by using carbon dioxide or steam; and chemical with zinc chloride. The materials were characterized by elemental analysis, pore structure, scanning electron microscopy and surface chemistry. To explore their potential application in water treatment, we evaluate the adsorption properties of the activated carbon cloths towards molecules with different physicochemical characteristics: phenol, methylene blue, and cadmium. The pore structure of the activated carbon cloths changes with the activation method: chemical activation generates microporous materials, while physical activation develops porosity in the micro and low mesopore range. The surface area of samples ranged from 480 to 1200 m2/g and a surface chemistry from neutral to acidic, with acid functional groups between 0.03 and 0.35 meq/g. Pore size distribution and surface chemistry had great influence in the adsorption capacity of the activated carbon cloths: microporous carbons were suitable to adsorb micropollutants such as phenol and cadmium, while methylene blue was adsorbed better in mesoporous activated carbon cloths. The activated carbon cloths with the higher amount of acid functionalities exhibited a higher adsorption capacity for cadmium than activated carbon cloths with a pristine surface. According to these results, jute and henequen are suitable for activated carbon cloths production, offering a green alternative to synthetic precursors.

The arsenic removal efficiency of iron-modified activated carbons depends greatly on the number of available iron oxide surface sites, which are given by the surface area of the anchored particles. In this sense, aiming the generation of an adsorbent with superior arsenic adsorption capacity, we developed a protocol to anchor interconnected fibrils of iron oxyhydroxides, using Mn2 + as a morphology regulator. The protocol was based on a microwave-assisted hydrothermal method, using bituminous based activated carbon and both Fe2 + and Mn2 + ions in the hydrolysis solution. The elemental analysis of modified carbons revealed that Mn does not anchor to the carbon. However, when Mn is included in the hydrolysis solution, the iron content in the activated carbon increased up to 3.5 wt%, without considerable decreasing the adsorbent surface area. Under specific hydrothermal conditions, the Mn2 + promoted the formation of iron oxide nanoparticles shaped as interconnected fibrils. This material showed a superior arsenic adsorption capacity in comparison to similar iron modified activated carbons (5 mg As/g carbon, at 2 mg As/L), attributed to the increase in quantity and availability of active sites located on the novel interconnected fibrils of iron oxyhydroxides nanostructures.

The high fluoride content of water in some areas of the world has garnered interest in searching for technologies and processes capable of efficiently removing fluoride at low cost. The use of bio adsorbent is a good and environmentally friendly technique for removing fluoride, due to the green nature of employed materials. Because of its high adsorption capacity, chitosan is a promising biosorbent that contains high amounts of amino and hydroxyl groups capable of interacting with fluoride. Furthermore, the presence of electropositive metal ions, such as transition metals and rare earth elements, like lanthanum, can improve the adsorption of electronegative fluoride. This study aims to synthesize a chitosan-zeolite composite modified with La(III) ions to improve its fluoride adsorption. Synthesized and modified composites were characterized by scanning electron microscopy, N2 physisorption, infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, and point of zero charge techniques in order to determine its physicochemical and texture properties and elucidate the mechanism of fluoride adsorption. The adsorption capacity was assessed by using the Langmuir and Freundlich isotherm models. According to the adsorption experiments, the composite modified with La (III) had a fluoride adsorption capacity of 14.3 mg g−1.

Astrometric Science and Technology Roadmap for Astrophysics (ASTRA) is a bilateral cooperation between China and Italy with the goal of consolidating astrometric measurement concepts and technologies. In particular, the objectives include critical analysis of the Gaia methodology and performance, as well as principle demonstration experiments aimed at future innovative astrometric applications requiring high precision over large angular separations (one to 180 degrees). Such measurement technologies will be the building blocks for future instrumentation focused on the "great questions" of modern cosmology, like General Relativity validity (including Dark Matter and Dark Energy behavior), formation and evolution of structure like proto-galaxies, and planetary systems formation in bio compatibles environments. We describe three principle demonstration tests designed to address some of the potential showstoppers for high astrometric precision experiments. The three tests are focused on the key concepts of multiple fields telescopes, astrometric metrology and very fine sub-pixel precision (goal, 12 pages, 12 figures; SPIE Astronomical Telescopes + Instrumentation, 2020, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation IV

Since July 2014, the ESA Gaia mission has been surveying the entire sky down to magnitude 20.7 in the visible. In addition to the millions of stars, thousands of Solar System Objects (SSOs) are observed daily. By comparing their positions to those of known objects, a daily processing pipeline filters known objects from potential discoveries. However, owing to Gaia's specific scanning law designed for stars, potential newly discovered moving objects are characterized by very few observations, acquired over a limited time. This aspect was recognized early in the design of the Gaia data processing. A daily processing pipeline dedicated to these candidate discoveries was set up to release calls for observations to a network of ground-based telescopes. Their aim is to acquire follow-up astrometry and to characterize these objects. From the astrometry measured by Gaia, preliminary orbital solutions are determined, allowing to predict the position of these potentially new discovered objects in the sky accounting for the large parallax between Gaia and the Earth (separated by 0.01 au). A specific task within the Gaia Consortium has been responsible for the distribution of requests for follow-up observations of potential Gaia SSO discoveries. Since late 2016, these calls for observations (called alerts) are published daily via a Web interface, freely available to anyone world-wide. Between November 2016 and July 2020, over 1700 alerts have been published, leading to the successful recovery of more than 200 objects. Among those, six have provisional designation assigned with the Gaia observations, the others being previously known objects with poorly characterized orbits, precluding identification at the time of Gaia observations. There is a clear trend for objects with a high inclination to be unidentified, revealing a clear bias in the current census of SSOs against high inclination populations., Submitted to Astronomy & Astrophysics

New observational data obtained during the 2018, 2019, and 2020 speckle runs with the 4.1-m Southern Astrophysical Research (SOAR) telescope located at Cerro Pachón (Chile) allowed us to recalculate the orbits of the visual binaries: WDS 00277-1625 (YR 1 Aa,Ab), WDS 00462-2214 (RST4155), WDS 03124-4425 (JC 8), WDS 07427-3510 (HDS 1091), WDS 10093+2020 (A2145), WDS 10116+1321 (HU 874 AB), WDS 10217-0946 (BU 25), WDS 11585-2350 (RST 3767 AB), WDS 13117-2633 (FIN 305), WDS 13305+0729 (A 1789), and WDS 16458-0046 (A1141). In addition, we present the first orbits calculated for the following binaries: WDS 07303-5657 (FIN 105), WDS 09110-1929 (I 824), WDS 12111-5302 (HU 1604), WDS 14592-4206 (HDS 2116 Aa,Ab), WDS 15157-2736 (BU 350), WDS 15493+0503 (A 1126), WDS 16402-2800 (VOU 44 AB), and WDS 18126+1224 (HDS 2570). All of them are placed below Dec. + 21° and the majority are main-sequence stars. Except in cases with giant components or close triple systems, the ANAPAR method was used in order to obtain precise dynamical parallaxes and individual masses. These parallaxes were compared with those obtained by Gaia and/or Hipparcos satellites. In the case of FIN 305, we present two different orbital solutions. Also, using the dynamical parallaxes given by these orbits, we have been able to calculate the luminosity of these systems. Said luminosities allow us to indicate an approximate age for the components of these systems, situating them within the Hertzsprung-Russell (HR) diagram. In addition, a commentary for each binary about the physical and dynamical properties of the studied binaries has been included We are very grateful for the continuous support of the Chilean Telescope Allocation Committee: http://www.das.uchile.cl/das_cntac.html under programs CN2018A-1, CN2019A-2, CN2019B-13, and CN2020A-19 and 2020B-10. This paper was supported by the ‘Xunta de Galicia’ (Spain), under the ED431B 2020/38 grant. RAM and EC acknowledge support from ANID/FONDECYT grant 1190038 SI

We present results from Speckle inteferometric observations of fifteen visual binaries and one double-line spectroscopic binary, carried out with the HRCam Speckle camera of the SOAR 4.1 m telescope. These systems were observed as a part of an on-going survey to characterize the binary population in the solar vicinity, out to a distance of 250 parsec. We obtained orbital elements and mass sums for our sample of visual binaries. The orbits were computed using a Markov Chain Monte Carlo algorithm that delivers maximum likelihood estimates of the parameters, as well as posterior probability density functions that allow us to evaluate their uncertainty. Their periods cover a range from 5 yr to more than 500 yr; and their spectral types go from early A to mid M - implying total system masses from slightly more than 4 MSun down to 0.2 MSun. They are located at distances between approximately 12 and 200 pc, mostly at low Galactic latitude. For the double-line spectroscopic binary YSC8 we present the first combined astrometric/radial velocity orbit resulting from a self-consistent fit, leading to individual component masses of 0.897 +/- 0.027 MSun and 0.857 +/- 0.026 MSun; and an orbital parallax of 26.61 +/- 0.29 mas, which compares very well with the Gaia DR2 trigonometric parallax (26.55 +/- 0.27 mas). In combination with published photometry and trigonometric parallaxes, we place our objects on an H-R diagram and discuss their evolutionary status. We also present a thorough analysis of the precision and consistency of the photometry available for them., Comment: 28 pages, 10 figures, 1 appendix. Accepted for publication in The Astronomical Journal

Institute of Astronomy, Graduate School of Science, the University of Tokyo is promoting the University of Tokyo Atacama Observatory Project, which is to construct an infrared-optimized 6.5m telescope at the summit of Co. Chajnantor (5640m altitude) in northern Chile. The high altitude and dry climate (PWV-0.5mm) realize transparent atmosphere in the infrared wavelength. The project is now approaching the final phase of the construction. Production of major components are almost completed: Production and preassembly test of a telescope mount and dome enclosure have been completed in Japan, and they are being transported to Chile. Three mirrors, the 6.5m primary, 0.9m secondary, and 1.1m-0.75m tertiary mirrors and their support systems have been all completed and tested in the USA. An aluminizing chamber have been fabricated in China, and its tests have been carried out in Japan. Development of two facility instruments, SWIMS and MIMIZUKU, are also completed. They were transported to the Subaru telescope, successfully saw the first light in 2018, and are confirmed to have the performance as designed. On-site construction work at the summit is now underway. Expansion of a summit access road from the ALMA concession was completed in 2019. Installation of foundation will follow, and then erection of the dome enclosure and a control building. The construction works are delayed by COVID-19, and we expect to complete the dome enclosure by Q3 of 2021. The telescope will be installed inside the dome and see the engineering first light by early 2022.

A poly(acrylic acid-co-itaconic acid) (PAA-co-IA)/NaOH hydrogel containing bamboo-type multiwall carbon nanotubes (B-MWCNTs) doped with nitrogen (PAA-co-IA/NaOH/B-MWCNTs) was synthesized and characterized by SEM, absorption of water, point of zero charges, infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The possible use of the PAA-co-IA/NaOH/B-MWCNT hydrogel as an electrode modifier and pre-concentrator agent for Cd(II) sensing purposes was then evaluated using carbon paste electrodes via differential pulse voltammetry. The presence of the B-MWCNTs in the hydrogel matrix decreased its degree of swelling, stabilized the structure of the swollen gel, and favored the detection of 3 ppb Cd(II), which is comparable to the World Health Organization&rsquo, s allowable maximum value in drinking water. A calibration curve was obtained in the concentration range of 2.67 &times, 10&minus, 8 to 6.23 &times, 7 M (i.e., 3 and 70 ppb) to determine a limit of detection (LOD) of 19.24 &mu, gL&minus, 1 and a sensitivity of 0.15 &mu, C ppb&minus, 1. Also, the Zn(II), Hg(II), Pb(II) and Cu(II) ions interfered moderately on the determination of Cd(II).

International audience; Individual and combined photo(electro)chemical reduction treatments of graphene oxide thin films have been performed to modulate the type of defects introduced into the graphene sheets during the reduction. These were characterized by X-ray photoeleanalysis and electrochemical methods. Illumination of the graphene oxide thin film electrodes with low irradiance simulated solar light provoked the photoassisted reduction of the material with negligible photothermal effects. The photoreduced graphene oxide displayed a fragmented sp2 network due to the formation of a high density of defects (carbon vacancies) and the selective removal of epoxides and hydroxyl groups. In contrast, the electrochemical reduction ctron and Raman spectroscopies, nuclear reaction under mild polarization conditions favored the formation of sp3 defects over vacancies, with a preferential removal of carbonyl and carboxyl groups over hydroxyl/epoxides. Used in conjunction, mild photochemical and electrochemical treatments allowed the obtainment of reduced graphene oxides with varied reduction degrees (ca. C/O ratio ranging from 4.9 to 2.2), and surface defects. Furthermore, the electrochemical reduction prevented the formation of vacancies during the subsequent illumination step. In contrast, both types of defects were accumulated when the GO electrode was first exposed to illumination and then polarized

The occurrence of pollutants in drinking water sources has become a serious problem worldwide. Sometimes, the contamination is not even related to human activities but occurs naturally during the weathering of minerals in water reservoirs. This is the typical case for arsenic- and fluoride-polluted human consumption water sources, which is a well-documented problem that impacts millions of people worldwide. Due to the health affectation to humans, the permissible concentration limit of arsenic and fluoride in drinking water is very low, 10 μg/L and 1.5 mg/L, respectively. Therefore, purifying water to reach those levels in a cost-effective way has become a real challenge. In this chapter, we first reviewed the full-scale strategies for the elimination of arsenic and fluoride from water, considering only physicochemical processes. Afterward, we make emphasis on adsorption, mainly by metal oxyhydroxides as adsorbent materials. The focus of the current research on this topic is the generation of new materials with superior characteristics, including higher adsorption capacity and selectivity. Metal and bimetallic oxyhydroxides have been developed and have shown to be promising materials to remove up to 200 and 250 mg/g of arsenic and fluoride, respectively. Also, researchers have oriented their efforts to transform metal oxyhydroxides into granular materials that can be applied in full-scale drinking water operations. Among the strategies are the synthesis of polymer composites, the agglomeration of metal oxide powder with various binders, and the anchorage of particles onto granular materials such as activated carbon: the processes involved are revised, with emphasis on the interactions between the carbonaceous matrix and the anchored metal oxyhydroxides.

Graphene oxide (GO) is a single-atom-thick sheet of carbon with oxygen-containing functional groups decorating its basal plane and edge sites. Most of its high surface area can be lost due to restacking of individual layers during the synthesis and drying of GO-based bulk sorbents. There is great interest to increase the specific surface area of graphene-based sorbents by introducing organic molecules as “pillaring agents” between GO sheets to hinder the stacking process and create sorbents with elevated surface area. This work synthesizes pillared GO by introducing chitosan (CS), a linear polysaccharide with various molecular weights. A composite of low molecular weight CS at a CS/GO ratio of 0.1 is shown to have the highest specific surface area (up to 70.5 m2/g) in comparison to the medium and high CS molecular weight, pristine GO, and the CS/GO composite materials. The affinity of the optimized GO/CS composites towards benzene, toluene, and naphthalene was evaluated at 19.3 mg/L of organic matter content while altering pH. Sips and Langmuir adsorption isotherm models well described the adsorption behavior, and benzene adsorption performance was reduced at low pH. Related to the presence of dissolved organic matter (DOM) in solution, lower diffusivity constants (k1) in hydrocarbon systems were recorded. Our results demonstrate the feasibility of CS as a potential pillaring agent in CS/GO composites to increase specific surface area and enhance the capture of soluble hydrocarbons from aqueous solutions.

Nafion and Ultrex membranes were modified with nanocomposites (NCs) of silver nanoparticles (AgNPs) immobilized on graphene oxide (GO) as a thin film, using a polydopamine adhesive (pda). The morphological, physicochemical, transport, electrochemical and anti-(bio)fouling properties were determined. The results indicated that the silver nanoparticles were immobilized on adsorption points of the graphene oxide to form nanocomposites. Polydopamine acted satisfactorily as a support and adhesive to bind the nanocomposites to the outer and inner surface of the membranes. The hydrophilicity, ionic exchange capacity, fixed ion concentration, electrochemical and conductivity properties were mostly enhanced in the modified Nafion membranes with pdaGO and pdaNC, but in the Ultrex a shortening of the hydrophilic channels occurred. The impedance results suggested that both modified membranes were more conductive at low frequencies or longer times, due to an adequate interfacial distribution of charges. The differences were attributed to the microstructure of the membranes. Also, the modification of Nafion and Ultrex membranes improved their anti-(bio)fouling properties. Hence, both membranes could be used in separation systems, since they allow a higher charge transfer and low energy consumption.

Graphene oxide (GO) is an emerging nanomaterial widely used in many manufacturing applications, which is frequently discharged in many industrial effluents eventually reaching biological wastewater treatment systems (WWTS). Anaerobic WWTS are promising technologies for renewable energy production through biogas generation; however, the effects of GO on anaerobic digestion are poorly understood. Thus, it is of paramount relevance to generate more knowledge on these issues to prevent that anaerobic WWTS lose their effectiveness for the removal of pollutants and for biogas production. The aim of this work was to assess the effects of GO on the methanogenic activity of an anaerobic consortium using a particulate biopolymer (starch) and a readily fermentable soluble substrate (glucose) as electron donors. The obtained results revealed that the methanogenic activity of the anaerobic consortium supplemented with starch decreased up to 23-fold in the presence of GO compared to the control incubated in the absence of GO. In contrast, we observed a modest improvement on methane production (>10% compared to the control lacking GO) using 5 mg of GO L−1 in glucose-amended incubations. The decrease in the methanogenic activity is mainly explained by wrapping of starch granules by GO, which caused mass transfer limitation during the incubation. It is suggested that wrapping is driven by electrostatic interactions between negatively charged oxygenated groups in GO and positively charged hydroxyl groups in starch. These results imply that GO could seriously hamper the removal of particulate organic matter, such as starch, as well as methane production in anaerobic WWTS.

Nowadays the recovery of low-molecular soluble aromatic hydrocarbons (HCs) released into natural bodies of water continues to be a challenging task. These contaminants bring sever consequences to the environment and to the human health. Biosorption on macroalgae (Ma) biomass seem to be a potential alternative due to low costs and high availability, but the low strength and density are important drawbacks to handle, start up and operate continuous biosorption units. In this study, chitosan (Ch) and pectin (Pe) were employed as precursors to synthesize a new Ma−Ch−Pe composite with regard to enhance the stability and applicability of macroalgae biomass towards the removal of soluble HCs pollutants. The biocomposite synthesis was based on a factorial design and a posterior response surface methodology. The optimized biocomposite (75.4%, 19.8 and 4.8% for macroalgae biomass, chitosan and pectin, respectively), was characterized and evaluated under different ionic strengths, pH values and organic load to determine their potential as biosorbents and to elucidate the adsorption mechanisms involved. Removal capacities were 58.68, 16.64 and 6.13 mg g−1 for benzene, toluene and naphthalene, respectively. The adsorption capacity was slightly influenced by the pH (3–9), and diminished with ionic strength values up to I > 0.6 M. The presence of dissolved organic matter (DOM) enhanced the removal of HCs by providing hydrophobic sites to the biosorbents. Moreover, the biosorption data was well-described by Sips adsorption isotherm, and the pseudo-second order equation represented the best fitting model for the biosorption kinetics. The biosorption mechanisms included hydrophobic effect by the algae fraction and London forces between the HC and the diverse of functional groups present offered by the precursors.

We present new results from the Parallaxes of Southern Extremely Cool dwarfs program to measure parallaxes, proper motions and multi-epoch photometry of L and early T dwarfs. The observations were made on 108 nights over the course of 8 years using the Wide Field Imager on the ESO 2.2m telescope. We present 118 new parallaxes of L \& T dwarfs of which 52 have no published values and 24 of the 66 published values are preliminary estimates from this program. The parallax precision varies from 1.0 to 15.5 mas with a median of 3.8 mas. We find evidence for 2 objects with long term photometric variation and 24 new moving group candidates. We cross-match our sample to published photometric catalogues and find standard magnitudes in up to 16 pass-bands from which we build spectral energy distributions and H-R diagrams. This allows us to confirm the theoretically anticipated minimum in radius between stars and brown dwarfs across the hydrogen burning minimum mass. We find the minimum occurs between L2 and L6 and verify the predicted steep dependence of radius in the hydrogen burning regime and the gentle rise into the degenerate brown dwarf regime. We find a relatively young age of 2 Gyr from the kinematics of our sample., Comment: In press MNRAS

Arsenic adsorption in aqueous solutions onto a novel goethite-P(AAm) (Poly(Acrylamide)) composite, in batch and continuous processes, has been studied. This work included the synthesis and characterization of a novel goethite-P(AAm) composite. For the synthesis of the composite, three grades of crosslinking and the goethite content were evaluated. The optimal synthesis conditions were determined by using the response surface methodology. The selected goethite-P(AAm) composite was characterized by swelling, surface area, thermogravimetric analysis (TGA), scan electron microscopy (SEM) and infrared spectroscopy (FTIR). The adsorption capacity of arsenic on the goethite-P(AAm) composite was 1.22 mg g−1, comparable to that of powder goethite. The immobilization mechanism of goethite in Poly(Acrylamide) was attributed to hydrogen bonding between goethite and hydroxyl and amines groups of P(AAm), as well as to acid and basic Lewis interactions. The adsorption isotherms were best fitted by the Langmuir model, and the adsorption process is promoted in acid solution. The column experiments demonstrated that the goethite-P(AAm) composite can supply 400 BV of treated water with less than 25 ppb, this means that only 1.53 kg of composite could be needed to supply the monthly consumption of domestic water for one person. These results suggest the potential application of goethite-P(AAm) composite like a friendly environmental adsorbent.

The redox-mediating capacity of magnetic reduced graphene oxide nanosacks (MNS) to promote the reductive biodegradation of the halogenated pollutant, iopromide (IOP), was tested. Experiments were performed using glucose as electron donor in an upflow anaerobic sludge blanket (UASB) reactor under methanogenic conditions. Higher removal efficiency of IOP in the UASB reactor supplied with MNS as redox mediator was observed as compared with the control reactor lacking MNS. Results showed 82 % of IOP removal efficiency under steady state conditions in the UASB reactor enriched with MNS, while the reactor control showed IOP removal efficiency of 51 %. The precise microbial transformation pathway of IOP was elucidated by high-performance liquid chromatography coupled to mass spectroscopy (HPLC-MS) analysis. Biotransformation byproducts with lower molecular weight than IOP molecule were identified in the reactor supplied with MNS, which were not detected in the reactor control, indicating the contribution of these magnetic nano-carbon composites in the redox conversion of this halogenated pollutant. Reductive reactions of IOP favored by MNS led to complete dehalogenation of the benzene ring and partial rupture of side chains of this pollutant, which is the first step towards its complete biodegradation. Possible reductive mechanisms that took place in the biodegradation of IOP were stated. Finally, the novel and successful application of magnetic graphene composites in a continuous bioreactor to enhance the microbial transformation of IOP was demonstrated.