The Role of Peripheral Amide Groups as Hydrogen-Bonding Directors in the Tubular Self-Assembly of Dinucleobase Monomers

Nanotubes are a fascinating kind of self‐assembled structure which have a wide interest and potential in supramolecular chemistry. We demonstrated that nanotubes of defined dimensions can be produced from dinucleobase monomers through two decoupled hierarchical cooperative processes: cyclotetramerization and supramolecular polymerization. Here we analyze the role of peripheral amide groups, which can form an array of hydrogen bonds along the tube axis, on this self‐assembly process. A combination of (1)H NMR and CD spectroscopy techniques allowed us to analyze quantitatively the thermodynamics of each of these two processes separately. We found out that the presence of these amide directors is essential to guide the polymerization event and that their nature and number have a strong influence, not only on the stabilization of the stacks of macrocycles, but also on the supramolecular polymerization mechanism

Describing soil surface microrelief by crossover length and fractal dimension

International audienceAccurate description of soil surface topography is essential because different tillage tools produce different soil surface roughness conditions, which in turn affects many processes across the soil surface boundary. Advantages of fractal analysis in soil microrelief assessment have been recognised but the use of fractal indices in practice remains challenging. There is also little information on how soil surface roughness decays under natural rainfall conditions. The objectives of this work were to investigate the decay of initial surface roughness induced by natural rainfall under different soil tillage systems and to compare the performances of a classical statistical index and fractal microrelief indices. Field experiments were performed on an Oxisol at Campinas, São Paulo State (Brazil). Six tillage treatments, namely, disc harrow, disc plow, chisel plow, disc harrow + disc level, disc plow + disc level and chisel plow + disc level were tested. Measurements were made four times, firstly just after tillage and subsequently with increasing amounts of natural rainfall. Duplicated measurements were taken per treatment and date, yielding a total of 48 experimental surfaces. The sampling scheme was a square grid with 25×25 mm point spacing and the plot size was 1350×1350 mm, so that each data set consisted of 3025 individual elevation points. Statistical and fractal indices were calculated both for oriented and random roughness conditions, i.e. after height reading have been corrected for slope and for slope and tillage tool marks. The main drawback of the standard statistical index random roughness, RR, lies in its no spatial nature. The fractal approach requires two indices, fractal dimension, D, which describes how roughness changes with scale, and crossover length, l, specifying the variance of surface microrelief at a reference scale. Fractal parameters D and l, were estimated by two independent self-affine models, semivariogram (SMV) and local root mean square (RMS). Both algorithms, SMV and RMS, gave equivalent results for D and l indices, irrespective of trend removal procedure, even if some bias was present which is in accordance with previous work. Treatments with two tillage operations had the greatest D values, irrespective of evolution stage under rainfall and trend removal procedure. Primary tillage had the greatest initial values of RR and l. Differences in D values between treatments with primary tillage and those with two successive tillage operations were significant for oriented but not for random conditions. The statistical index RR and the fractal indices l and D decreased with increasing cumulative rainfall following different patterns. The l and D decay from initial value was very sharp after the first 24.4 mm cumulative rainfall. For five out of six tillage treatments a significant relationship between D and l was found for the random microrelief conditions allowing a covariance analysis. It was concluded that using RR or l together with D best allow joint description of vertical and horizontal soil roughness variations

Using synchronization to improve earthquake forecasting in a cellular automaton model

A new forecasting strategy for stochastic systems is introduced. It is inspired by the concept of anticipated synchronization between pairs of chaotic oscillators, recently developed in the area of Dynamical Systems, and by the earthquake forecasting algorithms in which different pattern recognition functions are used for identifying seismic premonitory phenomena. In the new strategy, copies (clones) of the original system (the master) are defined, and they are driven using rules that tend to synchronize them with the master dynamics. The observation of definite patterns in the state of the clones is the signal for connecting an alarm in the original system that efficiently marks the impending occurrence of a catastrophic event. The power of this method is quantitatively illustrated by forecasting the occurrence of characteristic earthquakes in the so-called Minimalist Model.Comment: 4 pages, 3 figure

Aplicación del aprendizaje cooperativo en terapia ocupacional

El aprendizaje cooperativo como método de aprendizaje activo proporciona a los estudiantes la oportunidad de aprender con otros, está basado en la construcción colectiva del conocimiento y el desarrollo de habilidades. El aprendizaje es más eficaz cuando el alumno intercambia ideas con sus compañeros y cuando todos colaboran o aportan algo para llegar a una solución. Se consigue un aprendizaje significativo al ser sujeto activo y se motivan viendo su utilización con otros compañeros. La aplicación de esta metodología en Terapia Ocupacional es adecuada para la adquisición de competencias transversales y habilidades, conocimientos y actitudes específicos. Para el profesor supone mayor implicación y un esfuerzo inicial que se rentabiliza con los resultados conseguidos. El rol del profesor es fomentar el diálogo entre los estudiantes y lograr su implicación en su propio proceso de aprendizaje, actuando como mediador y como potenciador del aprendizaje. Se presentan propuestas para incorporar este método de enseñanza aprendizaje y se evalúan los resultados en un grupo de alumnos de primer curso

Ultrasound-assisted extraction of betalains from opuntia fruit pulp of different color varieties

Betalains are water-soluble pigments that have exhibited important pharmacological properties such as antioxidant, anticancer, antilipidemic and antimicrobial activity. These compounds have been isolated in numerous purple plants or fruits, as is the case of the wild species under the Opuntia genus. The fruits of these species are often disregarded because of their small size as well as the frequent presence of prickles. Based on this, this research has as its objective the optimization of a method based on ultrasound-assisted extraction to obtain extracts enriched with betalains from a wild Opuntia species (Opuntia dillenii (Ker Gawl.) Haw.). Four variables (%EtOH in the solvent, temperature of extraction, ultrasound amplitude and cycle) were selected using a Box-Behnken design. The quadratic interaction of %EtOH and the interaction of %EtOH-cycle have proven to be influential variables at 95% confidence. The conditions to obtain the highest betalain concentration were 100 mg of pulp with 20 mL (60%:40% EtOH:H2O) solvent at 20 degrees C at 24% amplitude and 0.2 cycle for 10 min. The suitability and reliability of the method were evaluated with repeatability and intermediate precision tests obtaining CVs <5%. Finally, the developed method has been employed in the analysis of five Opuntia commercial samples and obtained significant antioxidant activity of the extracts, confirming its applicability.info:eu-repo/semantics/publishedVersio

Bioactivity, nutritional property, and rapid chemical characterization of aqueous extract of Annona muricata leaf from Mexico

Purpose: To investigate the bioactive and nutritional properties, as well as rapid chemical characterization of aqueous extract of Annona muricata leaf from Mexico Methods: The crude aqueous extract of A. muricata leaf was obtained by decoction. Cytotoxicity was tested against cervicouterine cancer cells (HeLa) using methyl thiazol tetrazolium (MTT) assay. Antioxidant activity was evaluated using 2, 2-diphenylpicrylhydrazyl (DPPH) assay. Nutritional evaluation was carried out according to Association of Official Analytical Chemists (AOAC) procedures. Rapid qualitative chemical characterization of the extract was carried out by direct analysis in real-time mass spectrometry (DART-MS) method. Results: The aqueous extract of A. muricata leaf showed cytotoxicity against HeLa cells and also antioxidant activity in a concentration-dependent manner. Nutritional analysis revealed the presence of carbohydrates, vitamin C, Na, and Fe in the aqueous extract. DART-MS spectra showed the presence of alkaloids and phenols as the major components. Conclusion: The cytotoxic and antioxidant activities of the aqueous extract of A. muricata leaf lend some support for its traditional uses as anti-cancer remedy. These activities are probably due to its active secondary metabolites. Thus, the aqueous extract is a source of healthy nutritional components as well as a potential anti-cancer agent for humans

Assessment of the Canary current upwelling system in a regionally coupled climate model

The Canary current upwelling is one of the major eastern boundary coastal upwelling systems in the world, bearing a high productive ecosystem and commercially important fisheries. The Canary current upwelling system (CCUS) has a large latitudinal extension, usually divided into upwelling zones with different characteristics. Eddies, filaments and other mesoscale processes are known to have an impact in the upwelling productivity, thus for a proper representation of the CCUS and high horizontal resolution are required. Here we assess the CCUS present climate in the atmosphere-ocean regionally coupled model. The regional coupled model presents a global oceanic component with increased horizontal resolution along the northwestern African coast, and its performance over the CCUS is assessed against relevant reanalysis data sets and compared with an ensemble of global climate models (GCMs) and an ensemble of atmosphere-only regional climate models (RCMs) in order to assess the role of the horizontal resolution. The coupled system reproduces the larger scale pattern of the CCUS and its latitudinal and seasonal variability over the coastal band, improving the GCMs outputs. Moreover, it shows a performance comparable to the ensemble of RCMs in representing the coastal wind stress and near-surface air temperature fields, showing the impact of the higher resolution and coupling for CCUS climate modelling. The model is able of properly reproducing mesoscale structures, being able to simulate the upwelling filaments events off Cape Ghir, which are not well represented in most of GCMs. Our results stress the ability of the regionally coupled model to reproduce the larger scale as well as mesoscale processes over the CCUS, opening the possibility to evaluate the climate change signal there with increased confidence.Open Access funding enabled and organized by Projekt DEAL. Ruben Vazquez was supported through a doctoral grant at the University of Ferrara and University of Cadiz. Dmitry Sein was supported in the framework of the state assignment of the Ministry of Science and Higher Education of Russia (No. 0128-2021-0014). This work used resources of the Deutsches Klimarechenzentrum (DKRZ) granted by its Scientific Steering Committee (WLA) under project ID ba0987

Review and comparison of effective delayed neutron fraction calculation methods with Monte Carlo codes

The calculation of the effective delayed neutron fraction, beff , with Monte Carlo codes is a complex task due to the requirement of properly considering the adjoint weighting of delayed neutrons. Nevertheless, several techniques have been proposed to circumvent this difficulty and obtain accurate Monte Carlo results for beff without the need of explicitly determining the adjoint flux. In this paper, we make a review of some of these techniques; namely we have analyzed two variants of what we call the k-eigenvalue technique and other techniques based on different interpretations of the physical meaning of the adjoint weighting. To test the validity of all these techniques we have implemented them with the MCNPX code and we have benchmarked them against a range of critical and subcritical systems for which either experimental or deterministic values of beff are available. Furthermore, several nuclear data libraries have been used in order to assess the impact of the uncertainty in nuclear data in the calculated value of beff

Charged-current inclusive neutrino cross sections in the SuperScaling model

SuperScaling model (SuSA) predictions to neutrino-induced charged-current π+ production in the Δ-resonance region are explored under MiniBooNE experimental conditions. The SuSA charged-current π+ results are in good agreement with data on neutrino flux-averaged double-differential cross sections. The SuSA model for quasielastic scattering and its extension to the pion production region are used for predictions of charged-current inclusive neutrino- nucleus cross sections. The contribution of two-particle-two-hole vector meson-exchange current excitations is also considered within a fully relativistic model. Results are compared with the T2K experimental data for inclusive scattering.España, DGI y Fundación FEDER FIS2011-28738-C02-01, FPA2013-41267Junta de Andalucía CSD2007-0004