Dielectric Relaxations and Conductivity of Crosslinked PVA/SSA/GO Composite Membranes for Fuel Cells

[EN] Composite membranes obtained from Poly(vinyl Alcohol) (PVA) with sulfosuccinic acid (SSA) as crosslinking agent, and two different proportions of graphene oxide (GO), were prepared to be used in Proton Exchange Membrane Fuel Cells (PEMFCs). The superficial micrographs from transmission electron microscopy (TEM) confirmed a good dispersion of GO. Fourier Transform Infrared spectroscopy (FTIR) was used to evaluate the final chemical structure. Differential Scanning Calorimetry (DSC) showed that glass transition and crystalline phase were not present in the cross-linked PVA/SSA/GO composites membranes. Thermogravimetric analysis (TGA) demonstrated that the addition of GO reduced the moisture content and increased the thermal stability of the membranes. The electrical properties of PVA/SSA and PVA/SSA/GO composite membranes and the effect of GO concentration were evaluated by means of dielectric spectra in a broad range of temperatures and frequencies. The dielectric permittivity of these membranes was significantly promoted at low filler concentration due to an interfacial polarization effect. From the analysis of the dielectric relaxation spectrum, it can be deduced that the origin of the associated molecular movements is intramolecular and occurs in the working range of the PMEFC. In addition, the direct current conductivity, the protonic conductivity, and the polarization currents were correlated to the power produced in a hydrogen monocell. It was observed that low and no high GO concentrations of filler in PVA/SSA composite membranes enhanced their performance. The systematic characterization procedure based on the study of dielectric spectra and conductivity allowed to establish a potential approach to control the addition of GO in the design of other composite membranes for PEMFC with improved properties.The authors would like to thank Dr. Roberto Teruel Juanes and Dr. Victor Saenz de Juano for their advice in the treatment of results. The authors are also thankful to Generalitat Valenciana and the European Social Fund for the Santiago Grisolia scholarship, GRISOLIA/2013/031, and the Spanish Ministry of Science and Innovation for the concession of Research Project ENE2014-53734-C2-1-R.González-Guisasola, C.; Ribes-Greus, A. (2018). Dielectric Relaxations and Conductivity of Crosslinked PVA/SSA/GO Composite Membranes for Fuel Cells. Polymer Testing. 67:55-67. https://doi.org/10.1016/j.polymertesting.2018.01.024S55676

A new subspecies of Orthotylus junipericola Linnavuori, 1965 (Insecta, Heteroptera) from the Azores.

Orthotylus (Parapachylops) junipericola attilioi n.ssp. is described from Terceira (Azores), based on a single male specimen collected in the Azorean endemic tree Juniperus brevifolia. O. (Parapachylops) junipericola Linnavuori, 1965 is a “Rassenkreis” with seven known geographic races with an Atlanto-mediterranean distribution. O. (Parapachylops) junipericola attilioi n.ssp. is the eighth subspecies described from this species, being the most occidental taxon. The new subspecies, O. (Parapachylops) junipericola attilioi n.ssp., was sampled in a biodiversity hotspot from the Azores, Biscoito da Ferraria Natural Forest Reserve of “climax pattern of indigenous forest”

Assessment of the Accuracy of a Multi-Beam LED Scanner Sensor for Measuring Olive Canopies

MDPI. CC BYCanopy characterization has become important when trying to optimize any kind of agricultural operation in high-growing crops, such as olive. Many sensors and techniques have reported satisfactory results in these approaches and in this work a 2D laser scanner was explored for measuring canopy trees in real-time conditions. The sensor was tested in both laboratory and field conditions to check its accuracy, its cone width, and its ability to characterize olive canopies in situ. The sensor was mounted on a mast and tested in laboratory conditions to check: (i) its accuracy at different measurement distances; (ii) its measurement cone width with different reflectivity targets; and (iii) the influence of the target’s density on its accuracy. The field tests involved both isolated and hedgerow orchards, in which the measurements were taken manually and with the sensor. The canopy volume was estimated with a methodology consisting of revolving or extruding the canopy contour. The sensor showed high accuracy in the laboratory test, except for the measurements performed at 1.0 m distance, with 60 mm error (6%). Otherwise, error remained below 20 mm (1% relative error). The cone width depended on the target reflectivity. The accuracy decreased with the target density

Valorization of cotton residues for production of bio-oil and engineered biochar

[EN] Cotton seed was submitted to fast pyrolysis in a fixed bed reactor and the liquid and solid products were characterized applying several techniques. The detailed chemical composition of the bio-oil was investigated using GC × GC/TOFMS combined with software tools and retention index. A total of 257 compounds were tentatively identified with 168 were confirmed by LTPRI. The most abundant compounds identified in the cotton seed bio-oil were nitrogenous (56 compounds) and phenolic (42 compounds) what distinguishes this bio oil from others, produced from various sources of biomass. The higher heating values of cotton seed and bio-oil were 19.34 MJ kg ¿1 and 34.25 MJ kg ¿1 respectively and demonstrating the feasibility of the use of cotton seed in its natural form for energy generation or as a secondary source once a bio-oil with these characteristics would be a suitable candidate for use in boilers for heating purposes or chemical extraction. The biochar had a significant carbon content and a high heating value (22.12 MJ kg ¿1), making it attractive for fuel applications. The activation methods used were able to improve the physical and chemical characteristics of the biochar, as demonstrated by methylene blue adsorption tests. The maximum adsorption capacity of NaOH-activated biochar was 23.82 mg g ¿1 while that of K2CO3-activated biochar was 332.40 mg g ¿1.The authors would like to thanks the support of Brazilian Coordenaçao de Aperfeicoamento de Pessoal de Nivel Superior(CAPES, scholarships for the first author-Finance code 001) and EBW thorn Project Euro-Brazilian Windows Erasmus Mundus Program (scholarships for the first author).Primaz, CT.; Ribes-Greus, A.; Jacques, RA. (2021). Valorization of cotton residues for production of bio-oil and engineered biochar. Energy. 235:1-11. https://doi.org/10.1016/j.energy.2021.12136311123

A solar cycle lost in 1793--1800: Early sunspot observations resolve the old mystery

Because of the lack of reliable sunspot observation, the quality of sunspot number series is poor in the late 18th century, leading to the abnormally long solar cycle (1784--1799) before the Dalton minimum. Using the newly recovered solar drawings by the 18--19th century observers Staudacher and Hamilton, we construct the solar butterfly diagram, i.e. the latitudinal distribution of sunspots in the 1790's. The sudden, systematic occurrence of sunspots at high solar latitudes in 1793--1796 unambiguously shows that a new cycle started in 1793, which was lost in traditional Wolf's sunspot series. This finally confirms the existence of the lost cycle that has been proposed earlier, thus resolving an old mystery. This letter brings the attention of the scientific community to the need of revising the sunspot series in the 18th century. The presence of a new short, asymmetric cycle implies changes and constraints to sunspot cycle statistics, solar activity predictions, solar dynamo theories as well as for solar-terrestrial relations.Comment: Published by Astrophys. J. Let

The Dynamic Formation of Prominence Condensations

We present simulations of a model for the formation of a prominence condensation in a coronal loop. The key idea behind the model is that the spatial localization of loop heating near the chromosphere leads to a catastrophic cooling in the corona (Antiochos & Klimchuk 1991). Using a new adaptive grid code, we simulate the complete growth of a condensation, and find that after approx. 5,000 s it reaches a quasi-steady state. We show that the size and the growth time of the condensation are in good agreement with data, and discuss the implications of the model for coronal heating and SOHO/TRACE observations.Comment: Astrophysical Journal latex file, 20 pages, 7 b-w figures (gif files

On the novel free porphyrins corallistin B, C, D, and E : isolation from the demosponge Corallistes sp. of the Coral Sea and reactivity of their nickel (2) complexes toward formylating reagents

Reported here are the novel free corallistin B, C, D, and E, isolated as methyl esters 2a, 3a, 4a, and 5a, respectively, from the sponge #Corallistes sp.(#Lithistida) collected at the basis of the South New Caledonian coral reef. A protocol is also established for formulation of their NiII complexes, which show a different reactivity pattern toward DMF/POCI3 from metal complexes of deuteroporphyrin IX (isolate as 6a) also present in the sponge, the new corallistins, which may be thought to derive from protoporphyrin via heme, account for an amazing 60% of the etOH extract from the sponge. (Résumé d'auteur

Sponges and ascidians control removal of particulate organic nitrogen from coral reef water

10 pages, 5 figures, 5 tables.-- This is HIMB contribution 1199 and SOEST contribution 6596We studied removal rates of plankton and total particulate organic nitrogen (PON) by benthic reef communities from the overlying water in a large experimental flume. The flume was filled with mixtures of coral and coral rubble, and biomass of plankton was measured as water was recirculated over the experimental benthic community. All planktonic particle types, picoplankton, nanoplankton, microplankton, and total PON, decreased in concentration at rates proportional to their biomass. The mean first-order rate constant for the decrease in particle concentration was 96 ± 61 × 10-6 m s-1, corresponding to PON uptake of 10 mmol N m-2 d -1. Synechococcus sp. and heterotrophic bacteria were the major sources of PON. Particulate organic nitrogen removed by rubble and live coral assemblages was directly related to sponge and ascidian biomass (number and area) on the coral and coral rubble. Uptake of PON was about the same as the previously measured uptake of dissolved inorganic nitrogen into these coral reef communities, making it an important flux of nitrogen into the reef. © 2005, by the American Society of Limnology and Oceanography, Inc.Support for this work was provided by a postdoctoral fellowship from the Ministerio de Educación y Cultura (MEC) and a Ramón y Cajal research contract to M.R. This paper was funded in part by NOAA project R/CR-1, which is sponsored by the University of Hawaii Sea Grant College Program, School of Ocean and Earth Science Technology (SOEST), under grant NA 86RG0041. Additional funding was provided by CISNet (NOAA project NA 870A0531) and TransCom (Transfer at Community level) project (REN2002-01631/MAR)Peer Reviewe