Imperfect bifurcations via topological methods in superlinear indefinite problems

In [5] the structure of the bifurcation diagrams of a class of superlinear indefinite problems with a symmetric weight was ascertained, showing that they consist of a primary branch and secondary loops bifurcating from it. In [4] it has been proved that, when the weight is asymmetric, the bifurcation diagrams are no longer connected since parts of the primary branch and loops of the symmetric case form an arbitrarily high number of isolas. In this work we give a deeper insight on this phenomenon, studying how the secondary bifurcations break as the weight is perturbed from the symmetric situation. Our proofs rely on the approach of [5,4], i.e. on the construction of certain Poincar\'e maps and the study of how they vary as some of the parameters of the problems change, constructing in this way the bifurcation diagrams.Comment: 13 pages, 7 figure

Quasi-exact solvability beyond the SL(2) algebraization

We present evidence to suggest that the study of one dimensional quasi-exactly solvable (QES) models in quantum mechanics should be extended beyond the usual \sla(2) approach. The motivation is twofold: We first show that certain quasi-exactly solvable potentials constructed with the \sla(2) Lie algebraic method allow for a new larger portion of the spectrum to be obtained algebraically. This is done via another algebraization in which the algebraic hamiltonian cannot be expressed as a polynomial in the generators of \sla(2). We then show an example of a new quasi-exactly solvable potential which cannot be obtained within the Lie-algebraic approach.Comment: Submitted to the proceedings of the 2005 Dubna workshop on superintegrabilit

Protein-based emulsion electrosprayed micro- and submicroparticles for the encapsulation and stabilization of thermosensitive hydrophobic bioactives

This work shows the potential of emulsion electrospraying of proteins using food-grade emulsions for the microencapsulation and enhanced protection of a model thermosensitive hydrophobic bioactive. Specifically, gelatin, a whey protein concentrate (WPC) and a soy protein isolate (SPI) were compared as emulsion stabilizers and wall matrices for encapsulation of α-linolenic acid. In a preliminary stage, soy bean oil was used as the hydrophobic component for the implementation of the emulsion electrospraying process, investigating the effect of protein type and emulsion protocol used (i.e. with or without ultrasound treatment) on colloidal stability. This oil was then substituted by the ω-3 fatty acid and the emulsions were processed by electrospraying and spray-drying, comparing both techniques. While the latter resulted in massive bioactive degradation, electrospraying proved to be a suitable alternative, achieving microencapsulation efficiencies (MEE) of up to ∼70%. Although gelatin yielded low MEEs due to the need of employing acetic acid for its processing by electrospraying, SPI and WPC achieved MEEs over 60% for the non-sonicated emulsions. Moreover, the degradation of α-linolenic acid at 80 °C was significantly delayed when encapsulated within both matrices. Whilst less than an 8% of its alkene groups were detected after 27 h of thermal treatment for free α-linolenic acid, up to 43% and 67% still remained intact within the electrosprayed SPI and WPC capsules, respectively.Laura G. Gómez-Mascaraque is recipient of a predoctoral contract from the Spanish Ministry of Economy and Competitiveness (MINECO), Call 2013. The authors would like to thank the Spanish MINECO project AGL2012-30647 for financial support. Sara Díaz Cuesta is also acknowledged for experimental support.Peer reviewe

La evaluación del desempeño docente en la educación superior

The purpose of this article is to present a critical review of the ways in which the performance of university teachers are usually evaluated. Generally, the institutions state proposal of evaluation that usually coincide with what is evaluated and the use of the results. It includes the review of the different evaluation models to show the discrepancies between the objectives and the practices, that is, the poor relationship between the model used and what is done. Universities usually declare that the focus of the evaluation is improvement of practice. One of the most used instruments is the questionnaire, with which an accurate measurement can be made, but generally it does not evaluate the teaching performance, but, in the best-case scenario, the opinion of the students. If universities state that the evaluation should serve to improve the teaching practice, it would be advisable to favor the constructivist model that promotes changes required through the reflection that arises from the review of the self-evaluation, the hetero-evaluation and the co-evaluation.El objetivo de este trabajo es presentar una revisión crítica de las maneras en que se tiende a evaluar el desempeño de los docentes universitarios. Por lo general, las instituciones enuncian propósitos de la evaluación que suelen no coincidir con lo que se evalúa y con el uso que se hace de los resultados. Se incluye la revisión de distintos modelos de evaluación Para mostrar los desfases entre objetivos y prácticas, es decir, la pobre relación de lo que se hace, con el modelo del declarado. Se tiende a enunciar que el objetivo de la evaluación está centrado en la mejora continua. Uno de los instrumentos más utilizados es el cuestionario, con el que se pretende hacer una evaluación precisa, pero que, por lo general, no evalúa el desempeño docente, sino, en el mejor de los casos, la opinión de los estudiantes. Si se declara que la evaluación debe servir para mejorar la práctica docente, convendría privilegiar el modelo constructivista que permitiría favorecer los cambios que se requieren a través de la reflexión que surja de la revisión de la autoevaluación, la hetero-evaluación y la co-evaluación

La evaluación del desempeño docente en la educación superior

The purpose of this article is to present a critical review of the ways in which the performance of university teachers are usually evaluated. Generally, the institutions state proposal of evaluation that usually coincide with what is evaluated and the use of the results. It includes the review of the different evaluation models to show the discrepancies between the objectives and the practices, that is, the poor relationship between the model used and what is done. Universities usually declare that the focus of the evaluation is improvement of practice. One of the most used instruments is the questionnaire, with which an accurate measurement can be made, but generally it does not evaluate the teaching performance, but, in the best-case scenario, the opinion of the students. If universities state that the evaluation should serve to improve the teaching practice, it would be advisable to favor the constructivist model that promotes changes required through the reflection that arises from the review of the self-evaluation, the hetero-evaluation and the co-evaluation.El objetivo de este trabajo es presentar una revisión crítica de las maneras en que se tiende a evaluar el desempeño de los docentes universitarios. Por lo general, las instituciones enuncian propósitos de la evaluación que suelen no coincidir con lo que se evalúa y con el uso que se hace de los resultados. Se incluye la revisión de distintos modelos de evaluación Para mostrar los desfases entre objetivos y prácticas, es decir, la pobre relación de lo que se hace, con el modelo del declarado. Se tiende a enunciar que el objetivo de la evaluación está centrado en la mejora continua. Uno de los instrumentos más utilizados es el cuestionario, con el que se pretende hacer una evaluación precisa, pero que, por lo general, no evalúa el desempeño docente, sino, en el mejor de los casos, la opinión de los estudiantes. Si se declara que la evaluación debe servir para mejorar la práctica docente, convendría privilegiar el modelo constructivista que permitiría favorecer los cambios que se requieren a través de la reflexión que surja de la revisión de la autoevaluación, la hetero-evaluación y la co-evaluación

Optimal map of the modular structure of complex networks

Modular structure is pervasive in many complex networks of interactions observed in natural, social and technological sciences. Its study sheds light on the relation between the structure and function of complex systems. Generally speaking, modules are islands of highly connected nodes separated by a relatively small number of links. Every module can have contributions of links from any node in the network. The challenge is to disentangle these contributions to understand how the modular structure is built. The main problem is that the analysis of a certain partition into modules involves, in principle, as many data as number of modules times number of nodes. To confront this challenge, here we first define the contribution matrix, the mathematical object containing all the information about the partition of interest, and after, we use a Truncated Singular Value Decomposition to extract the best representation of this matrix in a plane. The analysis of this projection allow us to scrutinize the skeleton of the modular structure, revealing the structure of individual modules and their interrelations.Comment: 21 pages, 10 figure

Stability and bioaccessibility of EGCG within edible micro-hydrogels. Chitosan vs. gelatin, a comparative study

Micro-hydrogels are very promising systems for the protection and controlled delivery of sensitive bioactives, but limited knowledge exists regarding the impact of this encapsulation on their bioaccessibility. In this work, two different hydrogel-forming biopolymers (gelatin and chitosan) were compared as wall materials for the microencapsulation of a model flavonoid, (−)-epigallocatechin gallate (EGCG). Results showed that gelatin was more adequate as wall material for the encapsulation of EGCG than chitosan, achieving higher encapsulation efficiencies (95% ± 6%), being more effective in delaying EGCG release and degradation in aqueous solution and exhibiting a 7 times higher bioaccessibility of the bioactive compound (in terms of antioxidant activity) after in-vitro gastrointestinal digestion. A very low bioaccessibility of EGCG in chitosan was observed, due to the neutralization of the carbohydrate in the basic simulating salivary conditions, thus precluding subsequent flavonoid release. Moreover, gelatin micro-hydrogels also hindered dimer formation during in-vitro digestion, thus suggesting greater bioavailability when compared with free EGCG.Laura G. Gómez-Mascaraque is recipient of a predoctoral contract from the Spanish Ministry of Economy and Competitiveness (MINECO), Call 2013. The authors would like to thank the Spanish MINECO projectAGL2015-63855-C2-1 for financial support.Peer reviewe

A survey of IRAS young stellar object candidates: Searching for large-scale Herbig-Haro objects

Context. Jets and outflows are associated with young stellar objects across the stellar mass spectrum, from brown dwarf protostars to massive Ae/Be stars. Frequently the jet morphology is spatially discontinuous because of the temporal variability of the ejection from the driving source. Images covering a wide field of view around the jet-driving source are useful to map the large-scale jet emission and to explore the mass ejection history. Aims. The aim of our work was to search for large-scale optical Herbig-Haro (HH) objects lying in a wide field around a sample of IRAS sources, which are candidates to trace young stellar objects. Methods. Deep narrowband images through the Hα and [S II ] emission lines, and through an off-line continuum filter, covering a wide (∼15 0 ) field around the IRAS targets were acquired. The images in the three filters were analyzed to identify shock-excited line emission (i.e., HH) in contrast to scattered line emission. Results. New images of a sample of 15 IRAS sources, obtained in a homogeneous way are presented. HH emission was detected in six fields, and the astrometry of the knot features is given. The nature of the extended emission as scattered emission around nine of the IRAS targets is confirmed. For seven IRAS sources with unclear optical counterparts, a more plausible counterpart is proposed. A refined value of the source distance is reported for seven targets. An update of the main data available for each of the sampled fields, including images from public data archives, is also presented

Impact of molecular weight on the formation of electrosprayed chitosan microcapsules as delivery vehicles for bioactive compounds

The molecular weight of chitosan is one of its most determinant characteristics, which affects its processability and its performance as a biomaterial. However, information about the effect of this parameter on the formation of electrosprayed chitosan microcapsules is scarce. In this work, the impact of chitosan molecular weight on its electrosprayability was studied and correlated with its effect on the viscosity, surface tension and electrical conductivity of solutions. A Discriminant Function Analysis revealed that the morphology of the electrosprayed chitosan materials could be correctly predicted using these three parameters for almost 85% of the samples. The suitability of using electrosprayed chitosan capsules as carriers for bioactive agents was also assessed by loading them with a model active compound, (−)-epigallocatechin gallate (EGCG). This encapsulation, with an estimated efficiency of around 80% in terms of preserved antioxidant activity, showed the potential to prolong the antiviral activity of EGCG against murine norovirus via gradual bioactive release combined with its protection against degradation in simulated physiological conditions.Laura G. Gómez-Mascaraque is recipient of a predoctoral contract from the Spanish Ministry of Economy and Competitiveness (MINECO), Call 2013. Gloria Sanchez was supported by the “Ramón y Cajal” Young Investigator Program. The authors would like to thank the Spanish MINECO project AGL2015-63855-C2-1 and INIA grant RTA2014-00024-C04-03 for financial support.Peer reviewe

Reducing Trade Inequality: A Network-Based Assessment.

International trade, the network that underpins globalization, shows an extreme inequality. Despite efforts of multilateral organizations to foster a more fair world through trade agreements, it is hard to assess the effect of these changes on such a complex system. We have measured, using numerical simulation on a recently published network model, the impact of simple policies to boost trade chances among the weakest economies. Results suggest that global inequality may be reduced improving trade among low-income economies.post-print3064 K