286 research outputs found
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
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
In Vitro Probiotic Modulation of the Intestinal Microbiota and 2′Fucosyllactose Consumption in Fecal Cultures from Infants at Two Months of Age
2-fucosyllactose (2 FL) is one of the most abundant oligosaccharides in human milk, with benefits on neonatal health. Previous results point to the inability of the fecal microbiota from some infants to ferment 2 FL. We evaluated a probiotic formulation, including the strains Lactobacillus helveticus Rosell®-52 (R0052), Bifidobacterium longum subsp. infantis Rosell®-33 (R0033), and Bifidobacterium bifidum Rosell®-71 (R0071), individually or in an 80:10:10 combination on the microbiota and 2 FL degradation. Independent batch fermentations were performed with feces from six full-term infant donors of two months of age (three breastfed and three formula-fed) with added probiotic formulation or the constituent strains in the presence of 2 FL. Microbiota composition was analyzed by 16S rRNA gene sequencing. Gas accumulation, pH decrease and 2 FL consumption, and levels of different metabolites were determined by chromatography. B. bifidum R0071 was the sole microorganism promoting a partial increase of 2 FL degradation during fermentation in fecal cultures of 2 FL slow-degrading donors. However, major changes in microbiota composition and metabolic activity occurred with L. helveticus R0052 or the probiotic formulation in cultures of slow degraders. Further studies are needed to decipher the role of the host intestinal microbiota in the efficacy of these strains.This research was funded by a contract of Lallemand Health Solutions Inc. with IPLA-CSIC
(Spanish National Research Council contract number 201266) and by the Intramural Spanish National
Research Council project PIE201970E061. S.A. was the recipient of a postdoctoral Juan de la Cierva
contract (Ministry of Science and Innovation, Ref. IJCI-2017-32156), and N.S. has a postdoctoral
contract awarded by the Biosanitary Research Foundation in Asturias (FINBA, Spain)
Physical and psychological paths toward less severe fibromyalgia: A structural equation model
The authors gratefully acknowledge all the participants for their
collaboration and enthusiasm. We thank the assistant researchers
involved in this study and all the members of the Physical Activity
for HEaLth Promotion (PA-HELP; CTS-1018) research group.Supplementary data associated with this article can be found, in
the online version, at https://doi.org/10.1016/j.rehab.2019.06.017.Objectives: Previous research suggested isolated associations of physical and psychological factors with
fibromyalgia severity. Integration of physical and psychological, experienced and observed, modifiable
factors associated with fibromyalgia severity in a single model will reveal therapeutic paths toward less
severity of disease. We aimed to examine an encompassing model of determinants of fibromyalgia
severity.
Methods: This observational, population-based cross-sectional study included 569 people with
fibromyalgia. An integrative model of fibromyalgia severity was tested by using structural equation
modelling. This model included 8 factors: resilience, catastrophizing, active lifestyle, declarative
memory, subjective fitness, objective fitness, psychological distress, and physical fatigue.
Results: Two core paths were associated with reduced fibromyalgia severity: 1) a psychological path
connecting high resilience and low catastrophizing with low distress and 2) a physical path, connecting a
more active lifestyle (directly and via high objective and subjective physical fitness) with low fatigue.
Additional interconnecting paths especially suggested a connection from the psychological to physical
path. Our model explained 83% of the fibromyalgia severity.
Conclusions: The present model integrated the complexity of mutually influencing factors of fibromyalgia
severity, which may help to better understand the disease. It emphasised the importance of: 1) physical
factors and psychological factors and their interconnections, 2) patients’ experiences and clinical
measurements, and 3) positive and negative signs such as physical fitness and distress. Future
longitudinal and experimental research should aim at testing the causal direction of the associations in
the model as well as the clinical implications suggested by the model. For instance, to reduce fatigue,
exercise should enhance not only objective fitness but also fitness-related perceptions. Reducing distress
and fatigue seems crucial for lowering fibromyalgia severity.This work was supported by the Spanish Ministry of Economy and Competitiveness [I+D+i DEP2010-15639, I+D+I DEP2013-40908, I+D+I PSI2015-65241-R, and BES-2014-067612] and the Spanish Ministry of Education [FPU15/00002]. This study was funded in part by the University of Granada, Plan Propio de Investigación 2016, Excellence actions: Units of Excellence; Unit of Excellence on Exercise and Health (UCEES), and the Junta de Andalucía, Consejería de Conocimiento, Investigación y Universidades and European Regional Development Fund (ref. SOMM17/6107/UGR) and University of Jaén, Plan de Apoyo a la Investigación 2017-2019 [EI_SEJ07_2017]. The funders did not have any role in the study design, data collection and analyses, decision to publish, or preparation of the manuscript
Objective and subjective measures of physical functioning in women with fibromyalgia: what type of measure is associated most clearly with subjective well-being?
To find modifiable factors that are related to subjective well-being would be valuable for improving
interventions in fibromyalgia. Physical activity, sedentary behaviour, and physical fitness may represent potential
areas to optimize treatment regimens. In fibromyalgia, there is a discordance between clinical observations and
patient-reported outcomes (objective and subjective assessments). Therefore, the present study aims at analyzing
the associations of objective and subjective evaluations of physical activity, sedentary behaviour, and physical
fitness with subjective well-being and determine if and how objective and subjective associations differ In the most conservative multivariate analysis, we found independent associations of the objective
measures of physical activity with positive affect and life satisfaction and sedentary behaviour with
positive affect. No such relationship was seen with subjective measures of the same behaviours.
Moreover, we observed that objective and subjective physical fitness evaluations were independent of
each other related to subjective well-being. Independent associations of the objectivemeasures (but not the subjective assessments) of physical
activity with positive affect and life satisfaction, and of sedentary behaviour with positive affect were observed.
However, objective measures and subjective appraisals of physical fitness appear to be independently related to
well-being,which should be consideredwhen developing physical exercise interventions for fibromyalgiaThis work was supported by the Spanish Ministry of Economy and
Competitiveness [I+D+i DEP2010-15639, I+D+I DEP2013-
40908, and BES-2014–067612]; the Spanish Ministry of Education
[FPU15/00002]. This study has been partially funded by the
University of Granada, Plan Propio de Investigación 2016,
Excellence actions: Units of Excellence; Unit of Excellence on
Exercise and Health (UCEES), and by the Junta de Andalucía,
Consejería de Conocimiento, Investigación y Universidades and
European Regional Development Fund (ERDF), ref. SOMM17/6107/
UGR. This research was supported (in part) by the Intramural
Research program of the NIH, National Institute of Nursing
Research
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