Seqüència d'ensenyament-aprenentatge per a l'estudi de la interacció llum-matèria a secundària

Aquest article descriu una seqüència d'ensenyament-aprenentatge per a l'estudi de la in-teracció de la llum infraroja (IR) amb la matèria utilitzant diferents eines TIC. Es tracta d'una sessió contextualitzada al voltant de l'efecte d'hivernacle, plantejada per explorar els fonaments de la interacció entre la matèria i la radiació electromagnètica, que permet també introduir diversos conceptes relacionats amb l'espectroscòpia IR

Interacció llum-matèria i efecte hivernacle : seqüència didàctica per a l'estudi de l'espectroscòpia

Treball que correspon a les pràctiques que es fan als tallers REVIR organitzats pel CRECIM de la UAB. La seqüència pretén que l'alumnat de 1r i 2n de Batxillerat assoleixi una major comprensió de la interacció entre la radiació electromagnètica i la matèria. El punt de partida és un fenomen tan conegut com és l'efecte hivernacle, que porta a plantejar la pregunta: Com es pot explicar, des d'un punt de vista químic, la diferència entre els gasos que provoquen efecte hivernacle i els que no

How secondary school students conceptualize infrared radiation - matter interaction? Findings from a research study and implications for an instructional design

This study has been carried out within the REVIR scenario, which is a project promoting that secondary school students have access to a computerized laboratory at the Faculty of Education of our university and work in small groups during four hours with specific instructional material. One of the laboratory sessions included in the REVIR project deals with IR radiation-matter interaction, and is addressed to post-compulsory secondary students (16-18 year-old students). Within this framework, we have conducted a research study to analyse students' conceptualizations of the processes or mechanisms that take place in IR radiation-matter interaction (energy transfer, selective absorption), and its effects at a macroscopic level (temperature increase) and at a molecular level (vibration). For data collection, a question was posed to all students at the end of each REVIR session, asking students to relate what was described in an article about the application of an IR laser for acne treatment to what they had learnt throughout the session. The analysis of the 67 students' answers to that question revealed that many students explained the effects of the IR laser in vague terms, often repeating information included in the article, without explaining absorption of IR radiation in terms of energy. In consecutive versions of the instructional material, more oriented application questions were added after the article and explicit discussion around synthesis and exploratory (of students' previous ideas) questions was carried out during the session. From the analysis of 49 and 119 students' answers in consecutive later versions, we found that the introduction of these changes resulted in a greater number of students' descriptions in macroscopic and microscopic terms, and a lower number of answers simply repeating information extracted from the reading. Furthermore, more students explicitly explained absorption in terms of energy associated to IR light. Implications for the instructional design, in terms of critical features affecting people's abilities to transfer what they have learned, are discussed belo

Com fomentar les vocacions científico-tècniques?

Des de diversos sectors de la societat, com ara universitats, centres de recerca o administració pública, s'impulsa habitualment un gran ventall d'iniciatives adreçades a fer créixer l'interès per la ciència i la tecnologia entre el públic. En molts casos s'afirma que aquestes accions poden servir per perseguir un objectiu més concret, com és el de fomentar les vocacions científico-tècniques entre el jovent, tot i que moltes d'elles probablement estan més guiades per una vaga intuïció que per uns fonaments, i per altra part no sol avaluar-se'n l'impacte real. En aquesta línia, l'equip del CRECIM (Centre de Recerca per a l'Educació Científica i Matemàtica) ha fet un estudi, en el marc d'un projecte europeu (Projecte ECB/ingenious) finançat pel 7è PM i per diverses empreses, sobre els diferents factors que influeixen en els joves a l'hora de decantar-se per una formació científico-tècnica i sobre la forma en què es pot incidir en aquests factors des de l'àmbit educatiu.Desde varios sectores de la sociedad, tales como universidades, centros de investigación o administración pública, se impulsa habitualmente un gran abanico de iniciativas dirigidas a hacer crecer el interés por la ciencia y la tecnología entre el público. En muchos casos se afirma que estas acciones pueden servir para perseguir un objetivo más concreto, como es el de fomentar las vocaciones científico-técnicas entre la juventud, aunque muchas de ellas probablemente están más guiadas por una vaga intuición que por unos fundamentos, y por otra parte no suele evaluarse el impacto real. En esta línea, el equipo del CRECIM (Centro de Investigación para la Educación Científica y Matemática) ha hecho un estudio, en el marco de un proyecto europeo (Proyecto ECB/Ingenious) financiado por el septimo PM y por varias empresas, sobre los diferentes factores que influyen en los jóvenes al decantarse por una formación científico-técnica y sobre la forma en que se puede incidir en estos factores desde el ámbito educativo

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Seqüència d'ensenyament-aprenentatge per a l'estudi de la interacció llum-matèria a secundària

Aquest article descriu una seqüència d'ensenyament-aprenentatge per a l'estudi de la in-teracció de la llum infraroja (IR) amb la matèria utilitzant diferents eines TIC. Es tracta d'una sessió contextualitzada al voltant de l'efecte d'hivernacle, plantejada per explorar els fonaments de la interacció entre la matèria i la radiació electromagnètica, que permet també introduir diversos conceptes relacionats amb l'espectroscòpia IR

How secondary school students conceptualize infrared radiation - matter interaction? Findings from a research study and implications for an instructional design

This study has been carried out within the REVIR scenario, which is a project promoting that secondary school students have access to a computerized laboratory at the Faculty of Education of our university and work in small groups during four hours with specific instructional material. One of the laboratory sessions included in the REVIR project deals with IR radiation-matter interaction, and is addressed to post-compulsory secondary students (16-18 year-old students). Within this framework, we have conducted a research study to analyse students' conceptualizations of the processes or mechanisms that take place in IR radiation-matter interaction (energy transfer, selective absorption), and its effects at a macroscopic level (temperature increase) and at a molecular level (vibration). For data collection, a question was posed to all students at the end of each REVIR session, asking students to relate what was described in an article about the application of an IR laser for acne treatment to what they had learnt throughout the session. The analysis of the 67 students' answers to that question revealed that many students explained the effects of the IR laser in vague terms, often repeating information included in the article, without explaining absorption of IR radiation in terms of energy. In consecutive versions of the instructional material, more oriented application questions were added after the article and explicit discussion around synthesis and exploratory (of students' previous ideas) questions was carried out during the session. From the analysis of 49 and 119 students' answers in consecutive later versions, we found that the introduction of these changes resulted in a greater number of students' descriptions in macroscopic and microscopic terms, and a lower number of answers simply repeating information extracted from the reading. Furthermore, more students explicitly explained absorption in terms of energy associated to IR light. Implications for the instructional design, in terms of critical features affecting people's abilities to transfer what they have learned, are discussed belo

The role of exact exchange in the description of Cu2+-(H2O)(n) (n=1-6) complexes by means of DFT methods

This paper analyses the behavior of different density functionals in the description of the most stable structures of Cu2+-(H2O)(n) complexes (n = 1-6). From n = 3 to n = 6, different coordination numbers of the metal cation were considered. The structures and energies of the complexes were theoretically determined by means of density functional methods that include different amounts of exact exchange: the BLYP functional (0% of exact exchange), the B3LYP functional (20% of exact exchange), the MPWBlK functional (44% of exact exchange), and BHLYP functional (50% of exact exchange). In addition, CCSD(T) calculations with a large basis set were carried out. It has been found that the functionals with lesser amount of exact exchange. especially BLYP, fail to describe the relative energies between the different structures or each cluster because these functionals tend to overestimate the stability of low-coordinated structures. The inclusion of the exact exchange into the functional improves the results, those obtained with MPWBlK and BHLYP being in very good agreement with the CCSD(T) ones. This behavior is related to the poor description of the second ionization energy of Cu by pure functionals, which leads to a too delocalized spin density in the complex with GGA functionals

Interacció llum-matèria i efecte hivernacle : seqüència didàctica per a l'estudi de l'espectroscòpia

Treball que correspon a les pràctiques que es fan als tallers REVIR organitzats pel CRECIM de la UAB. La seqüència pretén que l'alumnat de 1r i 2n de Batxillerat assoleixi una major comprensió de la interacció entre la radiació electromagnètica i la matèria. El punt de partida és un fenomen tan conegut com és l'efecte hivernacle, que porta a plantejar la pregunta: Com es pot explicar, des d'un punt de vista químic, la diferència entre els gasos que provoquen efecte hivernacle i els que no

Enantioselective addition of oxazolones to maleimides. An easy entry to quaternary aminoacids

The catalytic enantioselective addition of 2-tert-butyl-4-aryl-1,3-oxazol-5-ones to maleimides is reported. The addition takes place exclusively at the C-4 position of the oxazolone ring, giving access to quaternary amino acid derivatives. The reaction is catalyzed by readily available chiral bases such as (DHQD)2PYR, rendering the final compounds in good yields and with moderate to good diastereo- and enantioselectivities. When the C-4-substituent of the 2-tert-butyl-oxazolone is an alkyl group, the regioisomeric C-2 addition product is also obtained.<br/