Estrategia de aprendizaje en la formación ambiental con estudiantes de las Ciencias Agrarias

En la actualidad, los procesos de aprendizaje de las ciencias agrarias deben volcar la mirada a fortalecer la temática ambiental y protección de los medios de vida, a transformar la ciencia y la tecnología a favor de una educación de calidad, orientada a fortalecer la temática ambiental, ya que permite una combinación extraordinaria entre los saberes y los quehaceres en el campo. Se ha desarrollado un estudio exploratorio, basándose desde un enfoque cualitativo, con el afán de comprender las valoraciones percibidas por los actores que han participado de estas experiencias. En palabras de los estudiantes “consideran que los conocimientos adquiridos nos benefician a saber trabajar la tierra sin degradarla” uno de los hitos de mayor relevancia en esta experiencia, es haber roto esquemas de la relación familia-hijos, puesto que los padres, al dejar a sus hijos realizar estos experimentos en sus propios lugares, consideran un paso importante en la vida de los jóvenes, que van cambiando su propio entorno. Estas acciones permiten armonizar actitudes, esquemas mentales y prácticas productivas que estén a la par de los desafíos del futuro

Temperature-Responsive Polyelectrolyte Complexes for Bio-Inspired Underwater Adhesives

Adhesive proteins of marine organisms contain significant amounts of hydrophobic amino acids. Therefore, inter- and intramolecular hydrophobic interactions are expected to play an important role in both adhesion and cohesion. Here, we mimic the hydrophobicity of adhesive proteins by using temperature-responsive polyelectrolyte complexes (TERPOCs) with a high poly(N-isopropylacrylamide) (PNIPAM) content. Upon mixing aqueous solutions of PNIPAM-b-poly(acrylic acid)-b-PNIPAM and poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA), complexation between the oppositely charged polyelectrolytes occurs. At low temperatures, complex coacervate core micelles (C3Ms) with a PNIPAM corona are formed, and upon a temperature increase, the solution turns into a hydrogel by the formation of a network of hydrophobic PNIPAM domains. Consequently, an abrupt increase in viscosity is observed upon heating which facilitates injectability of the adhesive. The gelation temperature, Tgel, and (adhesive) strength of the TERPOC can be adjusted by altering the salt and polymer concentration, which changes the balance between the electrostatic and hydrophobic interactions. Despite the importance of hydrophobic groups in strong underwater adhesives, we conclude that TERPOCs with a high PNIPAM content (70 wt%) are unstable due to water release. Consequently, there is a limited amount of hydrophobic groups that can be inserted in this type of systems. Nevertheless, TERPOCs show promising and tunable properties for application as injectable underwater adhesives, for example in biomedical applications

El huerto escolar como herramienta de sensibilización ambiental para el aprendiza je y mejora alimenticia en las comunidades rurales

El papel de la educación superior está llamado a jugar un papel importante en la formación de profesionales con calidad y calidez humana, valores que respondan a la sociedad con solidaridad y respeto. En ese sentido, la Universidad Nacional Autónoma de Nicaragua UNAN Managua, en su Facultad Regional Multidisciplinaria de Chontales (FAREM-Chontales), siguiendo el razonamiento planteado, ha desarrollado una iniciativa de apoyo al Ministerio de Educación (MINED), el cual ha armonizado los objetivos y la metodología de trabajo para la implementación de Huertos Escolares en dos escuelas de la comunidad San Miguelito, del municipio de Juigalpa, departamento de Chontales, Nicaragua; beneficiando a 69 jóvenes en multigrado por encuentro en secundaria con edades que oscilan entre 14 y 20 años y 20 niños de multigrado diurno con edades que oscilan de los 5 a 13 años y a 18 estudiantes universitarios. Desde la universidad se han apropiado tres principios: la adquisición de conocimientos, la creación de hábitos y el desarrollo de la comunicación, especialmente en el contexto rural, que es un universo de conocimientos y saberes aprovechables hacia el resguardo de la conciencia, la diversidad de sentidos del colectivo social, a las condiciones socio productivas que se pueden sumar al desarrollo de los objetivos educacionales en todos los niveles, para incidir en la mejora de la calidad educativa, diversidad productiva y de la dieta asegurando alimento y nutrición a la familia campesina. Como modelo de formación se incluyó a las jóvenes y comunitarias en la cocina, para mostrar de forma práctica los beneficios de las diferentes partes de los cultivos, el contenido nutricional, así como el buen sabor que poseen estos frutos orgánicos: “El huerto nos sirve para muchas cosas, aprender nuevas cosas, aprovechar los suelos, aprender a cultivar los patios para tener una buena alimentación que nos ayude a desarrollar sanos y saludables que nos ayude física y mentalmente”. Esta experiencia educativa demuestra que se puede llegar a adoptar cambios sustanciales en el pensar de la sociedad del sector urbano y del campo rural y, a vivir en concordancia con la naturaleza

Tuning the Interactions in Multiresponsive Complex Coacervate-Based Underwater Adhesives

In this work, we report the systematic investigation of a multiresponsive complex coacervate-based underwater adhesive, obtained by combining polyelectrolyte domains and thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) units. This material exhibits a transition from liquid to solid but, differently from most reactive glues, is completely held together by non-covalent interactions, i.e., electrostatic and hydrophobic. Because the solidification results in a kinetically trapped morphology, the final mechanical properties strongly depend on the preparation conditions and on the surrounding environment. A systematic study is performed to assess the effect of ionic strength and of PNIPAM content on the thermal, rheological and adhesive properties. This study enables the optimization of polymer composition and environmental conditions for this underwater adhesive system. The best performance with a work of adhesion of 6.5 J/m2 was found for the complex coacervates prepared at high ionic strength (0.75 M NaCl) and at an optimal PNIPAM content around 30% mol/mol. The high ionic strength enables injectability, while the hydrated PNIPAM domains provide additional dissipation, without softening the material so much that it becomes too weak to resist detaching stress. © 2019 by the authors. Licensee MDPI, Basel, Switzerland

Self-curing super-stretchable polymer/microgel complex coacervate gels without covalent bond formation

Elastic physical gels are highly desirable because they can be conveniently prepared and readily shaped. Unfortunately, many elastic physical gels prepared in water require in situ free-radical polymerization during the gel formation stage. In contrast, complex coacervate gels are physical gels that can be prepared by simply mixing two pre-formed oppositely-charged polyelectrolytes. However, as far as we are aware, highly elastic complex coacervate gels have not yet been reported. Herein, we combine polyanionic microgel particles with a well-known commercially-available cationic polyelectrolyte to prepare polymer/microgel complex coacervate (PMCC) physical gels. This new family of gels requires annealing at only 37 °C and behaves like a covalent gel but does not form covalent bonds. Thermal reconfiguration of the dynamic ionic bonds transforms the shapeable pre-gel into a highly elastic gel that is super-stretchable, adhesive, self-healing, highly swellable and can be further toughened using Ca2+ as an ionic crosslinker. Our PMCC gels have excellent potential for applications as engineering gels and structural biomaterials, as well as for wound healing and water purification

Thermoresponsive Complex Coacervate-Based Underwater Adhesive

Sandcastle worms have developed protein-based adhesives, which they use to construct protective tubes from sand grains and shell bits. A key element in the adhesive delivery is the formation of a fluidic complex coacervate phase. After delivery, the adhesive transforms into a solid upon an external trigger. In this work, a fully synthetic in situ setting adhesive based on complex coacervation is reported by mimicking the main features of the sandcastle worm's glue. The adhesive consists of oppositely charged polyelectrolytes grafted with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) chains and starts out as a fluid complex coacervate that can be injected at room temperature. Upon increasing the temperature above the lower critical solution temperature of PNIPAM, the complex coacervate transitions into a nonflowing hydrogel while preserving its volume—the water content in the material stays constant. The adhesive functions in the presence of water and bonds to different surfaces regardless of their charge. This type of adhesive avoids many of the problems of current underwater adhesives and may be useful to bond biological tissues.</p

Twelve-crystal prototype of Li2_2MoO4_4 scintillating bolometers for CUPID and CROSS experiments

An array of twelve 0.28 kg lithium molybdate (LMO) low-temperature bolometers equipped with 16 bolometric Ge light detectors, aiming at optimization of detector structure for CROSS and CUPID double-beta decay experiments, was constructed and tested in a low-background pulse-tube-based cryostat at the Canfranc underground laboratory in Spain. Performance of the scintillating bolometers was studied depending on the size of phonon NTD-Ge sensors glued to both LMO and Ge absorbers, shape of the Ge light detectors (circular vs. square, from two suppliers), in different light collection conditions (with and without reflector, with aluminum coated LMO crystal surface). The scintillating bolometer array was operated over 8 months in the low-background conditions that allowed to probe a very low, $\mu$Bq/kg, level of the LMO crystals radioactive contamination by $^{228}$Th and $^{226}$Ra.Comment: Prepared for submission to JINST; 23 pages, 9 figures, and 4 table

A first test of CUPID prototypal light detectors with NTD-Ge sensors in a pulse-tube cryostat

CUPID is a next-generation bolometric experiment aiming at searching for neutrinoless double-beta decay with ~250 kg of isotopic mass of $^{100}$Mo. It will operate at $\sim$10 mK in a cryostat currently hosting a similar-scale bolometric array for the CUORE experiment at the Gran Sasso National Laboratory (Italy). CUPID will be based on large-volume scintillating bolometers consisting of $^{100}$Mo-enriched Li$_2$MoO$_4$ crystals, facing thin Ge-wafer-based bolometric light detectors. In the CUPID design, the detector structure is novel and needs to be validated. In particular, the CUORE cryostat presents a high level of mechanical vibrations due to the use of pulse tubes and the effect of vibrations on the detector performance must be investigated. In this paper we report the first test of the CUPID-design bolometric light detectors with NTD-Ge sensors in a dilution refrigerator equipped with a pulse tube in an above-ground lab. Light detectors are characterized in terms of sensitivity, energy resolution, pulse time constants, and noise power spectrum. Despite the challenging noisy environment due to pulse-tube-induced vibrations, we demonstrate that all the four tested light detectors comply with the CUPID goal in terms of intrinsic energy resolution of 100 eV RMS baseline noise. Indeed, we have measured 70--90 eV RMS for the four devices, which show an excellent reproducibility. We have also obtained outstanding energy resolutions at the 356 keV line from a $^{133}$Ba source with one light detector achieving 0.71(5) keV FWHM, which is -- to our knowledge -- the best ever obtained when compared to $\gamma$ detectors of any technology in this energy range.Comment: Prepared for submission to JINST; 16 pages, 7 figures, and 1 tabl