Articulando las actividades de conjeturar y probar de los matemáticos profesionales desde la teoría de Peirce

“La formulación de conjeturas y el desarrollo de pruebas son dos aspectos fundamentales del trabajo de un matemático profesional” (Alibert y Thomas, 1991, p. 215). La investigación que estamos llevando a cabo pretende proponer un modelo, desde la educación matemática, que describa y explique cómo los matemáticos profesionales desarrollan las actividades de conjeturar y probar. Concretamente, y debido al carácter sociocultural de la investigación en matemáticas, los participantes considerados en este trabajo son investigadores en matemáticas que tienen al menos una publicación en “JCR science edition”

Nature or nurture? Clues from the distribution of specific star formation rates in SDSS galaxies

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reservedThis work investigates the main mechanism(s) that regulate the specific star formation rate (SSFR) in nearby galaxies, cross-correlating two proxies of this quantity -- the equivalent width of the \Ha\ line and the (u−r) colour -- with other physical properties (mass, metallicity, environment, morphology, and the presence of close companions) in a sample of ∼82500 galaxies extracted from the Sloan Digital Sky Survey (SDSS). The existence of a relatively tight `ageing sequence' in the colour-equivalent width plane favours a scenario where the secular conversion of gas into stars (i.e. `nature') is the main physical driver of the instantaneous SSFR and the gradual transition from a `chemically primitive' (metal-poor and intensely star-forming) state to a `chemically evolved' (metal-rich and passively evolving) system. Nevertheless, environmental factors (i.e. `nurture') are also important. In the field, galaxies may be temporarily affected by discrete `quenching' and `rejuvenation' episodes, but such events show little statistical significance in a probabilistic sense, and we find no evidence that galaxy interactions are, on average, a dominant driver of star formation. Although visually classified mergers tend to display systematically higher EW(Hα) and bluer (u−r) colours for a given luminosity, most galaxies with high SSFR have uncertain morphologies, which could be due to either internal or external processes. Field galaxies of early and late morphological types are consistent with the gradual `ageing' scenario, with no obvious signatures of a sudden decrease in their SSFR. In contrast, star formation is significantly reduced and sometimes completely quenched on a short time scale in dense environments, where many objects are found on a `quenched sequence' in the colour-equivalent width planeFinancial support has been provided by projects AYA2010-21887-C04-03 (former Ministerio de Ciencia e Innovación, Spain) and AYA2013-47742-C4-3-P (Ministerio de Economía y Competitividad), as well as the exchange programme ‘Study of Emission-Line Galaxies with Integral-Field Spectroscopy’ (SELGIFS, FP7-PEOPLE-2013-IRSES-612701), funded by the EU through the IRSES scheme. YA is also supported by the Ramón y Cajal programme (RyC-2011-09461), currently managed by the Ministerio de Economía y Competitividad (still cutting back on the Spanish scientific infrastructure

Towards a normative diagnosis tool in an organizational context: applying the Evaluative Model of the Normative Appeals

Basándonos en el Modelo Evaluativo de Apelaciones Normativas (EMNA), diseñamos una herramienta de diagnóstico que permite prever el grado de cumplimiento de un conjunto de normas por parte de los empleados. Primero realizamos dos estudios transversales para aplicar la herramienta en una muestra general de trabajadores (Estudio 1, N = 382) y en una muestra de empleados de una organización específica (Estudio 2, N = 82). Dos meses más tarde comprobamos en la misma organización (Estudio 3, N = 80) si la disposición a cumplir una serie de llamamientos normativos se ajustaba al diagnóstico generado en el Estudio 2. Los resultados apoyan la validez de la herramienta para diagnosticar la percepción y la disposición a cumplir los llamamientos normativosBased on the Evaluative Model of Normative Appeals (EMNA), we designed a diagnosis tool that allows forecasting the extent to which employees may comply with a set of norms. We first performed two cross-sectional studies to apply the tool within a general sample of workers (Study 1, N = 382) and within a sample of employees of a specific organization (Study 2, N = 82). Two months later we tested in the same organization (Study 3, N = 80) whether the willingness to comply with a set of normative appeals was aligned with the diagnosis generated in Study 2. The results support the validity of the tool to diagnose the perception of and willingness to comply with normative appeal

Sulfonated Graphene-Based Materials as Heterogeneous Acid Catalysts for Solketal Synthesis by Acetalization of Glycerol

Acid catalysis plays a pivotal role in the industrial landscape due to its multifaceted contributions to various chemical processes in numerous sectors, including petrochemicals, polymers, food processing, and biodiesel production, among others. Sulfonated graphenes hold notable relevance as heterogeneous acid catalysts due to their unique combination of graphene’s structural properties and the introduction of sulfonic groups as catalytic acid sites. Herein, we report the preparation of three sulfonated graphene based materials – sulfonated reduced graphene oxide (rGO-SO3H), chlorosulfonated reduced graphene oxide (rGO-HSO3Cl) and sulfonated graphene oxide (GO-SO3H) – by different synthetic approaches. Physicochemical, textural, morphological, and acidic properties of all materials were characterized in detail by different instrumental techniques. Innovatively, these materials have been evaluated as heterogeneous acid catalysts in the solketal synthesis by acetalization of glycerol, which is considered an interesting building block to produce added-value products. The density of acidic active sites and hydrophobicity were found to be conditioning parameters of the resulting catalytic activity in terms of conversion and selectivity. The best catalytic performance was obtained by rGO-SO3H, reaching the maximum conversion towards solketal in 15 minutes under mild reaction conditions. The reusability and stability of all materials were also examined after three consecutive acetalization reactions with only a slight loss of catalytic activity

Visible-light-driven photocatalytic H2 production using composites of Co-Al layered double hydroxides and graphene derivatives

The direct conversion of solar energy into chemical energy represents an enormous challenge for current science. One of the commonly proposed photocatalytic systems is composed of a photosensitizer (PS) and a catalyst, together with a sacrificial electron donor (ED) when only the reduction of protons to H2 is addressed. Layered double hydroxides (LDH) have emerged as effective catalysts. Herein, two Co-Al LDH and their composites with graphene oxide (GO) or graphene quantum dots (GQD) have been prepared by co-precipitation and urea hydrolysis, which determined their structure and so their catalytic performance, giving H2 productions between 1409 and 8643 μmol g−1 using a ruthenium complex as PS and triethanolamine as ED at 450 nm. The influence of different factors, including the integration of both components, on their catalytic behavior, has been studied. The proper arrangement between the particles of both components seems to be the determining factor for achieving a synergistic interaction between LDH and GO or GQD. The novel Co-Al LDH composite with intercalated GQD achieved an outstanding catalytic efficiency (8643 μmol H2 g−1) and exhibited excellent reusability after 3 reaction cycles, thus representing an optimal integration between graphene materials and Co-Al LDH for visible light driven H2 photocatalytic production.

Visible-light-harvesting basolite-A520 metal organic framework for photocatalytic hydrogen evolution

A heterogeneous photosensitizer Ru@dpdhpzBASF-A520 has been successfully synthesized following an unprecedented strategy based on the incorporation of surface dipyridyl-dihydropyridazine adducts by Diels–Alder reaction on the aluminum fumarate units of the highly porous metal-organic framework (MOF) BASF-A520 and their further coordination to ruthenium metal centers. The characterization of the resulting metal-organic framework, including the ruthenium bipyridine-like photosensitizer moieties attached to its linkers, has been carried out by a wide variety of techniques, such as X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption-desorption isotherms, solid-state cross-polarization magic angle spinning carbon-13 nuclear magnetic resonance (13C CP/MAS NMR), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible (UV–vis) spectroscopy. The light absorption in the visible region shown by the resulting material, Ru@dpdhpzBASF-A520, has allowed its application as a single-site solid photosensitizer for photochemical reactions of hydrogen evolution in conjunction with Pt nanoparticles as catalyst, EDTA as sacrificial electron donor and MV as electron carrier. A remarkable photocatalytic activity after 72 h was achieved, with a TON of 1157 based on the heterogeneous ruthenium photosensitizer, in aqueous solution at pH 5.0, which confirmed the effective stabilization of the ruthenium dipyridyl -dihydropyridazine adducts on the MOF surface and the efficient electron injection from the photoexcited Ru@dpdhpzBASF-A520 to Pt nanoparticles mediated by MV electron carrier for hydrogen generation from water

Novel interactions between phytoplankton and bacteria shape microbial seasonal dynamics in coastal ocean waters

Trophic interactions between marine phytoplankton and heterotrophic bacteria are at the base of the biogeochemical carbon cycling in the ocean. However, the specific interactions taking place between phytoplankton and bacterial taxa remain largely unexplored, particularly out of phytoplankton blooming events. Here, we applied network analysis to a 3.5-year time-series dataset to assess the specific associations between different phytoplankton and bacterial taxa along the seasonal scale, distinguishing between free-living and particle-attached bacteria. Using a newly developed network post-analysis technique we removed bacteria-phytoplankton correlations that were primarily driven by environmental parameters, to detect potential biotic interactions. Our results indicate that phytoplankton dynamics may be a strong driver of the inter-annual variability in bacterial community composition. We found the highest abundance of specific bacteria-phytoplankton associations in the particle-attached fraction, indicating a tighter bacteria-phytoplankton association than in the free-living fraction. In the particle-associated fraction we unveiled novel potential associations such as the one between Planctomycetes taxa and the diatom Leptocylindrus spp. Consistent correlations were also found between free-living bacterial taxa and different diatoms, including novel associations such as those between SAR11 with Naviculales diatom order, and between Actinobacteria and Cylindrotheca spp. We also confirmed previously known associations between Rhodobacteraceae and Thalassiosira spp. Our results expand our view on bacteria-phytoplankton associations, suggesting that taxa-specific interactions may largely impact the seasonal dynamics of heterotrophic bacterial communities

Integral field spectroscopy of nitrogen overabundant blue compact dwarf galaxies

We study the spatial distribution of the physical properties and of oxygen and nitrogen abundances in three Blue Compact Dwarf Galaxiess (HS 0128+2832, HS 0837+4717 and Mrk 930) with a reported excess of N/O in order to investigate the nature of this excess and, particularly, if it is associated with Wolf-Rayet (WR) stars We have observed these BCDs by using PMAS integral field spectroscopy in the optical spectral range (3700 - 6900 {\AA}), mapping their physical-chemical properties, using both the direct method and appropriate strong-line methods. We make a statistical analysis of the resulting distributions and we compare them with the integrated properties of the galaxies. Our results indicate that outer parts of the three galaxies are placed on the "AGN-zone" of the [NII]/H{\alpha} vs. [OIII]/H{\beta} diagnostic diagram most likely due to a high N/O combined with the excitation structure in these regions. From the statistical analysis, it is assumed that a certain property can be considered as spatially homogeneous (or uniform) if a normal gaussian function fits its distribution in several regions of the galaxy. Moreover, a disagreement between the integrated properties and the mean values of the distribution usually appears when a gaussian does not fit the corresponding distribution. We find that for Mrk 930, the uniformity is found for all parameters, except for electron density and reddening. The rotation curve together with the H{\alpha} map and UV images, reveal a perturbed morphology and possible interacting processes. The N/O is found to be constant in the three studied objects at spatial scales of the order of several kpc so we conclude that the number of WR stars estimated from spectroscopy is not sufficient to pollute the ISM and to produce the observed N/O excess in these objectsComment: 17 pages, 14 figures, accepted for publication in Astronomy & Astrophysic