Relative Asymptotic of Multiple Orthogonal Polynomials for Nikishin Systems

We prove relative asymptotic for the ratio of two sequences of multiple orthogonal polynomials with respect to Nikishin system of measures. The first Nikishin system ${\mathcal{N}}(\sigma_1,...,\sigma_m)$ is such that for each $k$, $\sigma_k$ has constant sign on its compact support \supp {\sigma_k} \subset \mathbb{R} consisting of an interval $\widetilde{\Delta}_k$, on which $|\sigma_k^{\prime}| > 0$ almost everywhere, and a discrete set without accumulation points in $\mathbb{R} \setminus \widetilde{\Delta}_k$. If {Co}(\supp {\sigma_k}) = \Delta_k denotes the smallest interval containing \supp {\sigma_k}, we assume that $\Delta_k \cap \Delta_{k+1} = \emptyset$, $k=1,...,m-1$. The second Nikishin system ${\mathcal{N}}(r_1\sigma_1,...,r_m\sigma_m)$ is a perturbation of the first by means of rational functions $r_k$, $k=1,...,m,$ whose zeros and poles lie in $\mathbb{C} \setminus \cup_{k=1}^m \Delta_k$.Comment: 30 page

Assessment of the performance of commonly used DFT functionals vs. MP2 in the study of IL-Water, IL-Ethanol and IL-(H2O)3 clusters

We present a comparative study of the accuracy of different DFT approaches vs. MP2 for evaluating ionic liquids (ILs) + cosolvent. Namely, we are interested in [XBmim] + cosolvent (X being Cl−, BF4−, PF6−, and CH3SO3− anions and cosolvent being water or ethanol) and [XBmim] + (H2O)3 clusters. In this study the B3LYP, B3LYP-D3, M06, M06-2X and M06-HF functionals with Pople and Dunning basis sets are considered. We find that the influence of the basis sets is a factor to take into consideration. As already seen for weakly bonded systems when the basis set quality is low the uncorrected counterpoise (unCP) or averaging counterpoise (averCP) energies must be used due to cancellation errors. Besides, the inclusion of extra diffuse functions and polarization is also required specially in the case of ILs interacting with water clusters. The B3LYP functional does not reproduce either the structure or the interaction energies for ILs + H2O and ILs + EtOH aggregates, the energetic discrepancies being more significant than the structural ones. Among the dispersive corrected functionals, M06-2X results resemble to a great extent the reference data when the unCP interaction energies are considered for both water and ethanol. In turn, M06 and B3LYP-D3 functionals are the best option for ILs containing polar and non-polar anions, respectively, whether the averCP interactions energies are taking into consideration. From the structural point of view, B3LYP and M06 functionals describe more open structures whereas B3LYP-D3, M06-2X and M06-HF structures resemble quite well MP2 results. When the number of water molecules increases the H bonding motif gains importance and the effect depends on the underlying functional. Only M06-2X and M06-HF behaviour is similar to that observed for one water molecule. This is important because to describe ILs-cosolvent solutions is not only necessary to take into account the ILs-cosolvent interactions but also the cosolvent-cosolvent ones in the ensemble of the system.Junta de Andalucía FQM282Ministerio de Ciencia e Innovación CTQ2011-2593

How to teach chemistry? Is Chemistry a new universal language

Chemistry has been developed greatly throughout the 20th century. Chemistry is included in the curriculum of elementary and secondary education. In general, students are not interested in science, and because of this ,students tend not to make an effort to learn and understand the meaning of concepts and the chemistry language that are being taught to them. If we consider that there is a little bit analogy between chemistry and foreign languages, we should learn the sym bols of the Periodic Table as symbols of an alphabet. The first knowledge that one needs to know when we are learning a second language is the new symbols of our new alphabet. It is necessary to learn more than 103 symbols, the chemical alphabet. After that, the students are ready to begin the formation of chemical words. In this case, learning the compounds names is easier when only two elements are involved, but when there are more than two, the chemical language is more complex. The proposal of this study is intended to design and implement a teaching strategy for teaching and learning the chemical language, first of all the chemical alphabet, the Periodic Table and then, the language which it is built the chemistry. For this proposal, we will use some m ultimedia application (Information and Communication Technologies (ITC)), which consists in an interactive periodic table. Students will be able to push one element and they will be able to see the properties of this element and which other element will be able to combine with it, and furthermore, if this element will be able to combine with itself. When they know properly the simple language, they will be able to continue studying more complex words, in this case, the reactions. With this multimedia application, the students will be able to watch how the atoms will change, one atom changes to a new atom during a whole reaction. And finally, they will be able to watch how these new atoms have new properties, and they combine each one. With this Periodic Table, the students learn chemical formulas and equations. 2. Experimental. This study was created as a descriptive study in which the survey technique was used. The study was carried out during the course 2013 /14. The sample consisted of 35 volunteer studen ts from two different classes, at the first course of Mechanical Engineer degree at University of Málaga. But the vast majority of them were there, they did not love chemistry. Each student made one questionnaire about the utility of our multimedia application. The scale of the test was a five point Likert type scale with a range of five options. The positive items range from 1= Certainly Agree to 5 = Certainly Disagree. 3. Results and Discussion. Mostly the average of these statements showed an overall positive response statements .The majority of the each student average of the response statements shown are positive, more than 2.5. After this study, we studied if there was some difference between the two groups studied and it can be seen that the mean an d the standard deviation for the different variables according to the two investigated groups demonstrated that there was no significant difference in the level of interest or utility that they give to the multimedia application. 4. Conclusions. The results of this study are based on a survey purpose after the use of an interactive application in order to improve the learning process of the chemistry language. This information is valuable since students could watch these animations on a computer. This is based on the cognitive theory of multimedia learning, which assumes that learners process information through a dual coding capability involving a auditory/verbal channel and a visual/pictorial channel. Nevertheless, the vast majority of students recognize that chemistry knowledge is useful to interpret aspect of their everyday life, but not many of them express their wish to continue chemistry studies.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

The use of simulations and videos in order to improve the learning of REDOX reactions in Engineering Degrees

Many students from secondary schools to universities in many countries struggle to learn chemistry and many do not succeed. Many high school and university students experience difficulties with fundamental ideas in chemistry [1]. Despite the importance of the foundation of chemistry, most students emerge from introductory courses with very limited understanding of the subject [2]. Chemistry had been regarded as a difficult subject for students by many researchers, teachers and science educators [3-4] because of the abstract nature of many chemical concepts, teaching styles applied in class, lack of teaching aids and the difficulty of the language of chemistry. Information and communication technologies (ICT) have fundamentally changed the practices and procedures of teaching Chemistry at University Degrees. In general, the use of ICT in education lends itself to more student-centred learning settings. Furthermore, and due to the fact that the globalization is becoming more and more important, the role of ICT in education is becoming more and more essential. The presence of ICT in the interactive educational environment can help to develop thinking skills and make classrooms an environment for educational growth. ICT also helps students to develop new thinking skills which may transfer to different situations which may require analysis and comprehension skills, and consequently critical skill development. ICT has become an increasingly popular technological tool within an educational context. Even though, the potential of ITC use in increasing student interactivity and collaboration has been explored by many educators, the research conducted on the effectiveness of these tools use in an educational context is still quite limited. In this work a study to investigate the use of ICT in the teaching and learning of Chemistry at Malaga University was conducted between 2015/16. The study participants were two classrooms of the 1º level of Mechanical Engineering Degree. In the present work, a positive attitude towards learning has been accompanied by a motivated behaviour. This could be seen as the use of the simulation and some videos (ICT). The present study investigated whether computer assisted instruction, simulation and videos were more effective than face-to-face instruction in increasing student success in chemistry. This study aims to investigate the effectiveness ICT as an educational tool in an undergraduate course for students. The results of the Mechanical Engineering Degree study is based on surveys purpose after the use of an interactive application and videos in order to know, if they think the use of these ITC have improved their learning process. On average, the students find the use and application useful, overall because they are able to transfer from macroscopic level to microscopic or/ and symbolic level. Several concepts and conceptual relations covered in the chemistry or science courses were provided in a concrete way, the help of computer simulations improved the student success significantly. [1] Carson, J. , & Watson, E. M (2002). Undergraduate students’ understandings of entropy and gibbs free energy. University Chemistry Education, 4, 4-12. [2] Ochs, R.S. (1996) Thermodynamics and Spontaneity, Journal of Chemical Education, 73(10), pp 952-954. [3] Carter, C.S. and Brickhouse, M.W. (1989) What Makes Chemistry Difficult? Alternate Perceptions, Journal of Chemical Education, 66(3), 223-225 [4] Nakhleh, M.B. (1992) Why Some Students Don’t Learn Chemistry, Chemical Misconceptions, Journal of Chemical Education, 69(3), 191-196.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Highlights from galactic observations with MAGIC

MAGIC is one of the main instruments for exploring the galactic gamma-ray sky from ground in the energy range of 50 GeV - 50 TeV. It consists of two 17 m diameter imaging atmospheric Cherenkov telescopes located at the Roque de los Muchachos Observatory, on the Canary island of La Palma. Thanks to its excellent sensitivity, MAGIC has conducted relevant studies on galactic objects of different types at Very High Energies. Among them, the Crab pulsar up to TeV energies, the spectral cut-off of the supernova remnant Cassiopeia A, the super-orbital variability of the binary system LSI +61 303, the search for microqusars, multi-year observations of the Galactic Center and follow-up studies of unidentified HAWC sources. In many cases, the results from these observations challenge our understanding of the underlying emission mechanisms. Here we review the latest results from the observation of these galactic sources with MAGIC.Comment: Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017), Bexco, Busan, Korea (arXiv:1708.05153

Chemical language, a language that you need to know if you want to learn Chemistry

There is a little bit analogy between chemistry and foreign languages. One reason why people find Chemistry as a language is because of the orthography, the systematic way it is written. In order to learn a second language, one needs to know the new symbols, In chemical language, it is necessary to learn 103 symbols, the chemical alphabet, this is the periodic table. After knowing the alphabet, the students are ready to begin the formation of chemical words. In this case, learning the compounds names are easier when only two elements are involved, but when there are more than two, the chemical language is more complex. As a language, students can build a huge amount of chemical formulas and reactions from finite components. After a few classes of chemistry, the students are ready to attempt intelligent conversation by combining the chemical alphabet words into sentences, the reactions. They can translate between Spanish and Chemistry. Actually, every chemist in every language refer to the same concept using the same word. It is true that in a subject as Chemistry, the language is laden with a specific vocabulary. As a foreign language, chemistry demand hard work in the form of many hours of repetitions examples and problems, but why not easy the burden by beginning. Chemical education researches have recognized that students often have difficulty learning chemistry concepts, language and so on. Researchers have proposed several suggestions as to the reasons for this difficulty, including frequent overloading of student working memory [1-3]. One of the major goals in teaching chemical language with a contextual approach is that students will develop the ability to understand a make decision about issued they may face in their everyday lives outside of the classroom [4,5]. In this work, we report a study that employed computer simulations. The proposal of this study is intended to design and implement a teaching strategy for teaching and learning the chemical language, first of all the chemical alphabet,the Periodic Table and then, the language which it is built the chemistry. For this proposal we will use some multimedia application (Information and Communication Technologies (TIC)), which consists in a interactive periodic table. Student will be able to push one element and they will be able to see the properties of this element and which other element will be able to combine with it, and furthermore, if this element will be able to combine with itself. Whenn they know properly the simple language, they will be able to continue studying more complex words, in this case, the reactions. With this multimedia application, the students will be able to watch how the atoms will change, one atom changes to a new atom during a whole reaction. And finally, they will be able to watch how these new atoms have new properties, and they combine each one. [1] Carlson, R., Chandler, P., Sweller, J., J. Educ. Psych., 95, (2003) p. 629. [2]. Johnstone, A. H., Chem. Educ. Res. Pract., 7, (2006) pp 49. [3]. Johnstone, A. H., J. Chem. Educ., 87, (2010) pp 22. [4] King, D. 2007. Teacher beliefs and constraints in implementing a context-based approach in chemistry. Teaching Science- the Journal of the austalian Scinece teacher association, 53 (1), 14.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech