A research work is being conducted to study the combined production and purification of hydrogen by means of redox processes departing from biomass fast pyrolysis oils (bio-oils). To achieve that ...goal, methanol has been used as featured material because it is the most representative compound of the alcoholic fraction of bio-oils. The study has been carried out in a fixed bed reactor where methanol decomposes in H2 and CO when gets in contact with a reactive solid based in an iron oxide at temperatures above 600 °C. During the first stage of the “steam–iron” process, reactive gases reduce the iron oxide to metallic iron. Afterward, in a following step, the previously reduced iron is reoxidized by steam producing a high purity hydrogen stream. Although coke deposition does exist during the reducing stage, this behaves as inert during the reoxidation process. Coke inert role has been corroborated by GC, SEM and TEM techniques, showing that carbon deposits were constituted by ordered structures (carbon nanotubes). The determination of the hydrogen production along successive cycles allowed the evaluation of the effect of temperature and alternating reactive atmospheres on the stability of the solid, as well as the optimum conditions for such purpose.
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•Production and purification of hydrogen departing from methanol by steam–iron.•Methanol as featured compound of alcoholic fraction of bio-oil for reductions.•Doped iron oxide as reactive material.•Steam as oxidative agent to generate purified hydrogen.•Highly structured carbon deposits act as inert during oxidation stages.
This study examined how heritage language and cultural funds of knowledge of Spanish-dominant Latinx immigrant families served as powerful resources for their concientización-critical awareness of ...important problems and social conditions-and bridged their cultural worlds of home, community, and school policy. The study drew on three complementary theories: Cultural Historical Activity Theory or Funds of Knowledge, Critical Pedagogy, and Bridging Multiple Worlds; all challenge common deficit models that these parents lack sufficient knowledge and concern for their children's formal education. Qualitative ethnographic study of Latinx immigrant parents in a parent engagement program revealed how dialogic interaction or plática, using colloquial funds of knowledge through dichos (words with extended metaphorical cultural significance) and refranes (proverbs conveying cultural wisdom about how to live and act), and cultural brokering from parent-coordinators helped parents author persuasive petition letters to school officials. The discussion addresses implications for research and practice supporting meaningful parent engagement.
This study aimed to select and characterize bacterial strains with multiple plant growth promotion properties able to tolerate drought and salinity stress in order to improve plant growth performance ...under abiotic stresses. Plant growth promoting activities were evaluated in 106 bacterial strains isolated by soil, compost, lignocellulosic biomasses and food matrices. Two strains A. chroococcum 67B and 76A were selected for their multiple plant growth promotion activities (N2-fixing activity, synthesis of siderophores and indole-3-acetic acid) as well as antimicrobial activity against Sclerotinia minor. Moreover, the selected strains were tested for their tolerance to drought and salinity stress in in vitro experiments evaluating their growth, production of SOD, CAT, proline and ACC deaminase. The two Azotobacter chroococcum strains exhibited high tolerance to salt and drought stresses and could alleviate the negative effects exerted by abiotic stress on tomato plants. Overall results showed that the strains Azotobacter chroococcum 67B and Azotobacter chroococcum 76A could be interesting candidates to be employed as bio-effector in sustainable agricultural systems also under stressful conditions leading to improved economic and environmental benefits.
Subject-area standards such as Common Core State Standards for Language Arts and Mathematics and Next Generation Science Standards offer deeper, richer views of subject-area proficiency. In science, ...they underscore doing things with facts and concepts, such as explaining, planning, and investigating—activities that are intertwined with language, with specialized structures and functions of academic English. This article explores the implications of a sociocognitive view of learning for assessment based on these standards, focusing on English learners (ELs). The authors describe how ELs and native English speakers alike develop subject-area and language resources jointly through activities, and how teachers use local knowledge to scaffold this development for students from diverse cultures and varying English experience. They then describe concomitant assessment strategies. The grounding of the standards in learning progressions enables the design of tasks which, while complex, challenge particular aspects of capability at targeted levels. A strategy can be used to craft tasks that are at once consistent with the standards but targeted to students with differing profiles of capabilities. This design strategy is well suited to contextualized formative assessment in local contexts such as classrooms. It supports design for large-scale assessment as well, although rich and complex tasks that are not matched to students' language and subject-area profiles face the low generalizability that plagued performance assessments in the 1980s. We consider ways that assessment design and tailored adaption can ameliorate some of the difficulties.
We present a new numerical code that solves the general relativistic magneto-hydrodynamical (GRMHD) equations coupled to the Einstein equations for the evolution of a dynamical spacetime within a ...conformally-flat approximation. This code has been developed with the main objective of studying astrophysical scenarios in which both, high magnetic fields and strong gravitational fields appear, such as the magneto-rotational collapse of stellar cores, the collapsar model of GRBs, and the evolution of neutron stars. The code is based on an existing and thoroughly tested purely hydrodynamical code and on its extension to accommodate weakly magnetized fluids (passive magnetic-field approximation). These codes have been applied in the past to simulate the aforementioned scenarios with increasing levels of sophistication in the input physics. The numerical code we present here is based on high-resolution shock-capturing schemes to solve the GRMHD equations, which are cast in first-order, flux-conservative hyperbolic form, together with the flux constraint transport method to ensure the solenoidal condition of the magnetic field. Since the astrophysical applications envisaged do not deviate significantly from spherical symmetry, the conformal flatness condition approximation is used for the formulation of the Einstein equations; this has repeatedly shown to yield very good agreement with full general relativistic simulations of core-collapse supernovae and the evolution of isolated neutron stars. In addition, the code can handle several equations of state, from simple analytical expressions to microphysical tabulated ones. In this paper we present stringent tests of our new GRMHD numerical code, which show its ability to handle all aspects appearing in the astrophysical scenarios for which the code is intended, namely relativistic shocks, highly magnetized fluids, and equilibrium configurations of magnetized neutron stars. As an application, magneto-rotational core-collapse simulations of a realistic progenitor are presented and the results compared with our previous findings in the passive magnetic-field approximation.
A new rock-dwelling (petrophilous) tiger beetle,
Duran & Roman,
is described from calcareous canyons and steep hillsides in the Trans-Pecos region of western Texas. It is distinguished from all other
...based on multiple morphological characters, biogeography, and ecology. A revised key to the genus
is provided.
Magneto‐elastic oscillations of neutron stars are believed to explain the observed quasi‐periodic oscillations (QPOs) in the decaying tail of the giant flares of highly magnetized neutron stars ...(magnetars). Strong efforts by theoretical modeling from different groups have increased our understanding of this phenomenon significantly. Here we discuss some constraints on the matter in neutron stars that arise if the interpretation of the observations in terms of superfluid magneto‐elastic oscillations is correct. To explain the observed modulation of the light curve of the giant flare, we describe a model that allows the QPOs to couple to the stellar exterior through the magnetic field. In this magnetosphere, the shaking magnetic field induces currents that provide scattering targets for resonant cyclotron scattering of photons, which is calculated with a Monte Carlo approach and coupled to a code that calculates the momentum distribution of the charge carriers as a one‐dimensional accelerator problem. We show first results of a simplified, but self‐consistent momentum distribution, that is a water‐bag distribution, and the corresponding spectra.
Selenium (Se) is an essential micronutrient for human health due to its antioxidant capabilities. The Se content around the world is highly variable from 0.005 mg kg-1 in areas from China and Finland ...to 8,000 mg kg-1 in seleniferous soils fromTuva-Russia. However, about one billion of people in the worldwide are Se deficient. During the last decade, studies related with strategies for Se biofortification in food plants for human nutrition have significantly increased because this metalloid is incorporated into human metabolism mainly as a constituent of food plants. Similarly, Se biofortification is important in pastures for increasing the Se content in cattle to enrich meat and to prevent disease associated to Se deficiency as white muscle disease. In China, two endemic diseaseshave been relatedto Se deficiency: Keshan and Keshin-Beck diseases. Agronomic biofortification by using inorganic Se sources is a current practice in countries as China, Finland, and USA. In Chile, fertilization by using chemical compounds with Se is an uncommon practice due the edaphoclimatic characteristics of Andisols, which represent around 60% of agricultural soils of southern Chile. Recent studies showed that microorganisms as bacteria and arbuscularmycorrhizal fungi play an important role in the transformations and Se availability, representing an interesting biotechnological alternative to Se biofortification. This review is focalized to describing Se behavior in soil-plant system and the possible strategies to improving Se content, including the use of microorganisms as biotechnological tools for increasing plant nutrition and quality. Specific attention will be devoted to volcanic soils of Southern Chile, where different factors concur to enhance the Se-deficiency problem.
This study evaluated the co-inoculation effect of the endophytic selenobacteria Bacillus sp., Klebsiella sp. or Acinetobacter sp. and the arbuscular mycorrhizal (AM) fungus Rhizophagus intraradices ...on lettuce plants grown under drought conditions. Plants inoculated with bothnmicroorganisms were able to enhance the Se content in their shoots (1 to 6 pg plant-1) and promote macro-and micronutrient uptake. Moreover, the inoculated plants showed significantntolerance to drought stress, as determined by their adaptation to physiological parameters(relative water content and stomatal conductance), increase in photosynthetic pigments (chlorophyll and carotenoids) and improvement inantioxidant enzyme levels (catalase, ascorbate peroxidase and glutathione reductase). The selenobacteria increased the Se content in lettuce plants and enhanced the effect of AM fungus in controlling the antioxidant systems that play a role as elicitors of plant drought responses and improving the nutritional quality and physiological and biochemical processes involved in plant drought tolerance.
We present an alternative method to estimate the numerical viscosity in simulations of astrophysical objects, which is based on the damping of fluid oscillations. We apply the method to general ...relativistic hydrodynamic simulations using spherical coordinates. We perform 1D spherical and 2D axisymmetric simulations of radial oscillations in spherical systems. We first calibrate the method with simulations with physical bulk viscosity and study the differences between several numerical schemes. We apply the method to radial oscillations of neutron stars and we conclude that the main source of numerical viscosity in this case is the surface of the star. We expect that this method could be useful to compute the resolution requirements and limitations of the numerical simulations in different astrophysical scenarios in the future.
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