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In the current work, we compared the green synthesis of silver nanoparticles (AgNP) using plant extracts, a promising methodology against the use of chemical reducers, such as oleic acid and oleylamine. The advantages of green synthesis are one-step method, economic and ecological while the advantages of classic synthesis methods are high nanoparticle performance, homogeneity in size and smaller average sizes. With this work we want to demonstrate that plant extracts with specific mixtures of chemical compounds can obtain smaller average sizes with greater homogeneity in nanoparticles compared to the use of classical synthesis. Myrtillocactus geometrizans was used as a polar plant extract, which was selected by the chemical components contained in the extract. Phytosterols, oleic acid and betalains contained in Myrtillocactus geometrizans are biomolecules responsible for the reduction and stability of AgNP below 5 nm. TEM analysis of the green synthesis of nanoparticles revealed the formation of spherical particles with an average diameter of 5 nm and with preferential crystallographic directions of the silver plane .
We report the synthesis of metal-free nitrogen-doped electrocatalysts obtained from graphite and urea as carbon and nitrogen precursor, respectively. High-energy milling and thermal annealing were carried out to obtain low cost electrocatalysts. Additionally, this method has shorter synthesis times, is environmentally friendly and use high-availability raw materials. A short-route synthesis consisted in the partial exfoliation of graphite by mechanical milling with urea. Afterwards, nitrogen was integrated into the exfoliated graphite lattice by thermal annealing at 500°C. XPS analyses shows up to 1.7 at. % was incorporated to the graphitic lattice. Scanning Electron Microscopy, X-ray diffraction and Raman Spectroscopy were used to analyse the morphology and structural features. The catalytic activity for the oxygen reduction reaction in basic media was evaluated by the rotating disk electrode technique.
The excitability of local surface plasmon modes in radial trimers composed of gold nanorods was mapped using hyperspectral cathodoluminescence (CL) in the scanning electron microscope. In symmetric trimers, the local plasmon resonances could be excited most effectively at the ends of individual rods. Introducing asymmetry into the structure breaks the degeneracy of the dipole modes and changes the excitability of transverse dipole modes in different directions. CL in the scanning electron microscope has great potential to interrogate individual nanophotonic structures and is a complement to electron energy loss spectroscopy and optical microscopy.
The Hopf bifurcation from spike solutions for the classical Gierer–Meinhardt system in a onedimensional interval is considered. The existence of time-periodic solution near the Hopf bifurcation parameter for a boundary spike is rigorously proved by the classical Crandall–Rabinowitz theory. The criteria for the stability of the limit cycle are determined, and it is shown that the limit cycle is unstable.
We report on the successful demonstration of a 150 J nanosecond pulsed cryogenic gas cooled, diode-pumped multi-slab Yb:YAG laser operating at 1 Hz. To the best of our knowledge, this is the highest energy ever recorded for a diode-pumped laser system.
To examine the feasibility of using social media to assess the consumer nutrition environment by comparing sentiment expressed in Yelp reviews with information obtained from a direct observation audit instrument for grocery stores.
Trained raters used the Nutrition Environment Measures Survey in Stores (NEMS-S) in 100 grocery stores from July 2015 to March 2016. Yelp reviews were available for sixty-nine of these stores and were retrieved in February 2017 using the Yelp Application Program Interface. A sentiment analysis was conducted to quantify the perceptions of the consumer nutrition environment in the review text. Pearson correlation coefficients (ρ) were used to compare NEMS-S scores with Yelp review text on food availability, quality, price and shopping experience.
Detroit, Michigan, USA.
Yelp reviews contained more comments about food availability and the overall shopping experience than food price and food quality. Negative sentiment about food prices in Yelp review text and the number of dollar signs on Yelp were positively correlated with observed food prices in stores (ρ=0·413 and 0·462, respectively). Stores with greater food availability were rated as more expensive on Yelp. Other aspects of the food store environment (e.g. overall quality and shopping experience) were captured only in Yelp.
While Yelp cannot replace in-person audits for collecting detailed information on the availability, quality and cost of specific food items, Yelp holds promise as a cost-effective means to gather information on the overall cost, quality and experience of food stores, which may be relevant for nutrition outcomes.
We briefly introduce the VLBI maser astrometric analysis of IRAS 18043–2116 and IRAS 18113–2503, two remarkable and unusual water fountains with spectacular bipolar bow shocks in their high-speed collimated jet-driven outflows. The 22 GHz H2O maser structures and velocities clearly show that the jets are formed in very short-lived, episodic outbursts, which may indicate episodic accretion in an underlying binary system.
The study of orthographic errors in a transparent language such as Spanish is an important topic in relation to writing acquisition because in Spanish it is common to write pseudohomophones as valid words. The main objective of the present study was to explore the possible differences in activation patterns in brain areas while processing pseudohomophone orthographic errors between participants with high (High Spelling Skills (HSS)) and low (Low Spelling Skills (LSS)) spelling orthographic abilities. We hypothesize that (a) the detection of orthographic errors will activate bilateral inferior frontal gyri, and that (b) this effect will be greater in the HSS group. Two groups of 12 Mexican participants, each matched by age, were formed based on their results in a group of spelling-related ad hoc tests: HSS and LSS groups. During the fMRI session, two experimental tasks were applied involving correct and pseudohomophone substitution of Spanish words. First, a spelling recognition task and second a letter searching task. The LSS group showed, as expected, a lower number of correct responses (F(1, 21) = 52.72, p <.001, η2 = .715) and higher reaction times compared to the HSS group for the spelling task (F(1, 21) = 60.03, p <.001, η2 = .741). However, this pattern was reversed when the participants were asked to decide on the presence of a vowel in the words, regardless of spelling. The fMRI data showed an engagement of the right inferior frontal gyrus in HSS group during the spelling task. However, temporal, frontal, and subcortical brain regions of the LSS group were activated during the same task.
After more than half a century of community support related to the science of “solar activity”, IAU's Commission 10 was formally discontinued in 2015, to be succeeded by C.E2 with the same area of responsibility. On this occasion, we look back at the growth of the scientific disciplines involved around the world over almost a full century. Solar activity and fields of research looking into the related physics of the heliosphere continue to be vibrant and growing, with currently over 2,000 refereed publications appearing per year from over 4,000 unique authors, publishing in dozens of distinct journals and meeting in dozens of workshops and conferences each year. The size of the rapidly growing community and of the observational and computational data volumes, along with the multitude of connections into other branches of astrophysics, pose significant challenges; aspects of these challenges are beginning to be addressed through, among others, the development of new systems of literature reviews, machine-searchable archives for data and publications, and virtual observatories. As customary in these reports, we highlight some of the research topics that have seen particular interest over the most recent triennium, specifically active-region magnetic fields, coronal thermal structure, coronal seismology, flares and eruptions, and the variability of solar activity on long time scales. We close with a collection of developments, discoveries, and surprises that illustrate the range and dynamics of the discipline.
Este libro reúne un número significativo de artículos suponen una aportación ciertamente notable a la bibliografía disponible hasta la fecha. Juan de Mena: de letrado a poeta recoge dieciséis trabajos en los que se estudia su figura y su obra desde perspectivas distintas pero complementarias que abren nuevas líneas de investigación o bien enriquecen otras ya existentes. El libro está estructurado en tres grandes bloques temáticos: El primero de ellos se dedica al contexto histórico de Juan de Mena. El segundo bloque gira en torno a la configuración del poeta, atendiendo a la conciencia autorial de Mena y a los recursos literarios que emplea. El tercer y último bloque está dedicado a la transformación del 'famosíssimo poeta Juan de Mena' en un clásico. Cristina Moya García es profesora en la Universidad de Córdoba. This book contains several studies reviewing the two facets of Juan de Mena's life as lawyer and poet. These contributions open up new lines of research on this important early-fifteenth-century Castilian writer and enrich some existing ones, studying Juan de Mena from different perspectives. The book is structured into three thematic blocks: The first is devoted to the historical context of Juan de Mena. The second section focuses on the configuration of the poet. The third and final part is dedicated to the transformation of "famosíssimo poeta Juan de Mena" into a classic author. Cristina Moya García is a profesor at the Universidad de Córdoba.Contributors: Federica Accorsi, Carlos Alvar, Linde M. Brocato, Daniel Capra, Juan Luis Carriazo Rubio, Antonio Cortijo, Sila Gómez Álvarez, Ángel Gómez Moreno, Daniel Hartnett, Julián Jiménez Heffernan, Maxim Kerkhof, Françoise Maurizi, Cristina Moya García, Francisco de Paula Cañas Gálvez, Pedro Ruiz Pérez.