Narrar y hacer química en un nuevo contexto

Se analiza un taller llevado a cabo en la Universitat Autònoma de Barcelona perteneciente Proyecto ITACA , cuyo objetivo es introducir a los estudiantes de secundaria en la actividad científica que concretamos como "hacer y narrar sobre química". Los datos sobre la ‘actividad química de los alumnos’ se obtienen a partir de una narrativa experimental creada por ellos a partir de la actividad realizada

On the theory of the skewon field: From electrodynamics to gravity

The Maxwell equations expressed in terms of the excitation $\H=({\cal H}, {\cal D})$ and the field strength $F=(E,B)$ are metric-free and require an additional constitutive law in order to represent a complete set of field equations. In vacuum, we call this law the ``spacetime relation''. We assume it to be local and linear. Then $\H=\H(F)$ encompasses 36 permittivity/permeability functions characterizing the electromagnetic properties of the vacuum. These 36 functions can be grouped into 20+15+1 functions. Thereof, 20 functions finally yield the dilaton field and the metric of spacetime, 1 function represents the axion field, and 15 functions the (traceless) skewon field \notS_i{}^j (S slash), with $i,j=0,1,2,3$. The hypothesis of the existence of \notS_i{}^j was proposed by three of us in 2002. In this paper we discuss some of the properties of the skewon field, like its electromagnetic energy density, its possible coupling to Einstein-Cartan gravity, and its corresponding gravitational energy.Comment: latex-file, 15 pages, 1 figur

Selection of white-rot fungi to formulate complex and coated pellets for Reactive Orange 165 decolourization

Six strains of white-rot fungi isolated from southern Chile were evaluated for their ergosterol/biomass correlation and ligninolytic potential in solid medium to formulate pellets for Reactive Orange 165 (RO165) decolourization. The fungus Anthracophyllum discolor was selected to formulate complex pellets (fungal mycelium, sawdust, and activated carbon), coated pellets (complex pellet + alginate) and simple pellets (fungal mycelium). The activity of ligninolytic enzymes (laccase, manganese peroxidase, manganese-independent peroxidase, and lignin peroxidase) was evaluated in both the complex and coated pellets in modified Kirk medium, and the morphology of the pellets was studied using scanning electron microscopy (SEM). Complex pellets of A. discolor showed a higher enzymatic production mainly MnP (38 U L-1 at day 15) compared to coated and simple pellets. Examinations using SEM showed that both pellets produced a black core that was entrapped by a layer of fungal mycelium. Decolourization of RO165 was demonstrated with all the pellets formulated. However, the highest and fastest decolourization was obtained with complex pellets (100% at day 8). Therefore, complex pellets of A. discolor can be used for the biological treatment of wastewater contaminated with RO165.This research was supported by a FONDECYT grant 1090678 and a Doctoral thesis fellowship CONICYT 24100149

Torsion nonminimally coupled to the electromagnetic field and birefringence

In conventional Maxwell--Lorentz electrodynamics, the propagation of light is influenced by the metric, not, however, by the possible presence of a torsion T. Still the light can feel torsion if the latter is coupled nonminimally to the electromagnetic field F by means of a supplementary Lagrangian of the type l^2 T^2 F^2 (l = coupling constant). Recently Preuss suggested a specific nonminimal term of this nature. We evaluate the spacetime relation of Preuss in the background of a general O(3)-symmetric torsion field and prove by specifying the optical metric of spacetime that this can yield birefringence in vacuum. Moreover, we show that the nonminimally coupled homogeneous and isotropic torsion field in a Friedmann cosmos affects the speed of light.Comment: Revtex, 12 pages, no figure

Effect of antioxidant and optimal antimicrobial mixtures of carvacrol, grape seed extract and chitosan on different spoilage microorganisms and their application as coatings on different food matrices

There is growing interest in the use of natural agents with antimicrobial (AM) and antioxidant (AOX) properties. Optimization of the AM capacity for mixtures containing carvacrol, grape seed extract (GSE) and chitosan, against gram-negative (Pseudomonas aeruginosa), gram-positive bacteria (Staphylococcus aureus, Listeria innocua and Enterococcus faecalis) and yeast (Saccharomyces cerevisiae) at 106 cfu mL−1 was studied. To observe the synergistic or antagonistic effect and find optimal combinations between the three agents, a simplex centroid mixture design was run for each microorganism, combining carvacrol (0-300 ppm, X1)X, GSE (0-2000 ppm, X2) and chitosan (0-2% w/v, X3). Results of the response surface analysis showed several synergistic effects for all microorganisms. Combinations of 60 ppm-400 ppm-1.2% w/v (carvacrol-GSE-chitosan; optimal AM combination 1, OAMC-1); 9.6 ppm-684 ppm-1.25% w/v (OAMC-2); 90 ppm-160 ppm-1.24% w/v (OAMC-3) were found to be the optimal mixtures for all microorganisms. Radical scavenging activity (RSA) of the same agents was then compared with a standard AOX (butylated hydroxytoluene; BHT) at different concentrations (25, 50 and 100 ppm; as well as the optimal AM concentrations) by the 1,1-diphenyl-2- picrylhydrazyl (DPPH) method. RSA increased in the following order: chitosan< carvacrol< BHT< GSE and for the OAMC: OAMC-2< OAMC-1< OAMC-3. The best RSA (OAMC-3) was applied as a coating in two different food matrices (strawberries and salmon). For strawberries, P. aeruginosa was more sensitive to the action of OAMC-3 than S. cerevisiae. For salmon, S. aureus was more resistant to the action of OAMC-3 than E. faecalis and L. innocua.info:eu-repo/semantics/publishedVersio

Multilayer emulsions stabilized by vegetable proteins

There is great interest in the food, cosmetic and pharmaceutical industry in the use of proteins and polysaccharides as natural hydrocolloids to create novel emulsion systems with improved stability and functionality. For example, the electrostatic interaction between proteins and polysaccharides may be used to form oil-in-water (O/W) emulsions with multilayered interfacial membranes around oil droplets or multilayer emulsions. This type of emulsions have been developed using the layer-by-layer (LbL) technique, which consists of direct adsorption of an oppositely charged polyelectrolyte layer (e.g. polysaccharides) on a primary layer of ionic emulsifiers (e.g. proteins). The polymeric structure and electrical charge of proteins make them a special class of compounds very suitable for its utilization in the LbL technique. In recent years, the utilization of proteins as emulsifier in the food and pharmaceutical industry has been turning towards plants as a preferred alternative to animal-based sources. This article reviews the current understanding of the utilization of different vegetable proteins as emulsifier in order to stabilize O/W multilayer emulsions systems. Additionally, it highlights some potential applications of the multilayer emulsion technology in the industry for improving the stability of emulsions to environmental stresses or and for developing controlled or triggered release systems

Massive motion in Brans-Dicke geometry and beyond

Gravity theories that can be viewed as dynamics for area metric manifolds, for which Brans-Dicke theory presents a recently studied example, require for their physical interpretation the identification of the distinguished curves that serve as the trajectories of light and massive matter. Complementing previous results on the propagation of light, we study effective massive point particle motion. We show that the relevant geometrical structure is a special Finsler norm determined by the area metric, and that massive point particles follow Finsler geodesics.Comment: 12 page

Chilean Spanish transcultural adaptation of CAP-II and SIR scales in an online format for parents of children with hearing aids or cochlear implants

Spoken language acquisition is challenging for very young deaf or hard-of-hearing children (DHH) who wear hearing aids or cochlear implants (CI). Timely decision-making for treatment is essential for these children and requires suitable assessments. Two such assessments are the Categories of Auditory Performance Index II (CAP-II) and the Speech Intelligibility Rating Scale (SIR). These have been shown to be helpful for the ongoing evaluation of developing speech perception and spoken language skills in various languages, but they are not available in Chilean Spanish. This study aimed to create a Chilean Spanish translation of the CAP-II and SIR appropriate for online self-administration by parents-caregivers in Chile to assist professionals in monitoring DHH children’s progress, considering the COVID-19 restrictions. The methods used in the process started with translating a self-report proposal from the original English versions of the CAP-II and SIR scales. Finally, the Chilean Spanish versions were tested in 107 Chilean parents-caregivers of DHH children with CIs. The results suggest these instruments are suitable for use in a Chilean context

Direcciones y derroteros de la Protección Social en Chile : análisis del proceso de reconstrucción de una ciudadanía basada en derechos

Production of INCASI Project H2020-MSCA-RISE-2015 GA 691004La hipótesis de trabajo que este articulo discute se centra en afirmar que si bien la protección social en Chile tiene una concepción o diseño universalista que responde al concepto de ciudadanía social postconvencional, en su aplicación tiende al particularismo y a la focalización: Esta tensión entre diseño e imple-mentación estaría dando cuenta de distintos tipos de sistemas de bienestar, que oscilan entre perspectivas de bienestar más comunitaristas y perspectivas más liberales. Tomando en cuenta lo anterior, las decisiones que se tomen a futuro en torno a las políticas que faltan por integrar a este sistema, serán claves para entender el tipo de orientación que éste terminará asumiendo en su fase de madurez, ¿Qué fisonomía adquirirá finalmente la protección social en Chile? Es la interrogante que este artículo quiere dejar planteada a pocos meses del término del segundo período de gobierno de la Presidenta de la República, Michelle Bachelet en cuyo primer y segundo mandato se impulsaron bases de esta discusión que propende al cambio de lógica de la política.The working hypotheses that this article discusses it centers on affirm that although social protection in Chile has a universalist conception or design that responds to the concept of postconventional social citizenship, in its application tends to particularism and targeting: This tension between design and implementation would be realizing different types of welfare systems, ranging from more communitarian welfare perspectives to more liberal perspectives. For the same reason, the decisions that are taken in the future around the policies that are missing to integrate this system will be key to understand the type of orientation that this will end up assuming in its phase of maturity, ¿What physiognomy will finally acquire the social protection in Chile? It is the question that this article wants to leave raised a few months after the end of the second period of government of the President of the Republic, Michelle Bachelet in whose first and second mandate have been driven bases of this discussion that tends to change the logic politics