Symmetry-induced interference effects in metalloporphyrin wires

Organo-metallic molecular structures where a single metallic atom is embedded in the organic backbone are ideal systems to study the effect of strong correlations on their electronic structure. In this work we calculate the electronic and transport properties of a series of metalloporphyrin molecules sandwiched by gold electrodes using a combination of density functional theory and scattering theory. The impact of strong correlations at the central metallic atom is gauged by comparing our results obtained using conventional DFT and DFT+U approaches. The zero bias transport properties may or may not show spin-filtering behavior, depending on the nature of the d state closest to the Fermi energy. The type of d state depends on the metallic atom and gives rise to interference effects that produce different Fano features. The inclusion of the U term opens a gap between the d states and changes qualitatively the conductance and spin-filtering behavior in some of the molecules. We explain the origin of the quantum interference effects found as due to the symmetry-dependent coupling between the d states and other molecular orbitals and propose the use of these systems as nanoscale chemical sensors. We also demonstrate that an adequate treatment of strong correlations is really necessary to correctly describe the transport properties of metalloporphyrins and similar molecular magnets

Formulación de un material de impresión dental en forma de pasta

Los materiales de impresión dental (MID) basados en alginato son muy empleados en Estomatología. En la actualidad se plantea que los MID en forma de pasta tienen una mayor fidelidad de copia, mejor reproducción de detalles de la impresión y no desprenden polvos volátiles secos que sean inhalados por los especialistas en su utilización cotidiana, por lo que se decidimos estudiar una formulación de un MID en forma de pasta. En el presente trabajo se reporta un material formado por dos pastas que al mezclarse entre si en las proporciones adecuadas, gelifica, obteniéndose la impresión. En el componente A esta contenido el alginato de sodio, y en el otro componente B, una sal de un metal divalente (CaSO 4). Se utilizó alginato de sodio sin secar, determinando el porciento de humedad y calculando así, el peso de alginato seco. Se agregó al alginato húmedo el resto de los componentes de la pasta A. A la formulación obtenida se le realizaron las siguientes pruebas físico-mecánicas: apariencia y uniformidad, tiempo de trabajo, tiempo de mezcla, tiempo de fraguado, viscosidad, relación pasta A/pasta B, resultando en todos los casos dentro de los límites establecidos según la norma ISO 1563. Se realizó además el ensayo de pérdida de agua del material (sinéresis) y se comparó con el Dentalgin, MID en forma de polvo.Peer Reviewe

Análisis de las representaciones icónicas del agua subterránea en los textos de educación secundaria

Las diversas investigaciones didácticas han mostrado que la fase subterránea del ciclo del agua es, junto a la fase área, la peor comprendida por el alumnado e incluso puede pasar desapercibida. Sin embargo, el análisis de las ilustraciones gráficas y otros elementos icónicos presentes en los textos del primer ciclo de educación secundaria obligatoria pone de manifiesto el gran número de conceptos y elementos que se representan en estos materiales curriculares. Con su análisis y trabajo en el aula, los profesores tienen una magnífica oportunidad para favorecer la alfabetización visual del alumnado y eliminar sus errores de comprensión en esta fase del ciclo del agua

Photoelectric results of the total lunar eclipse of April 12-13, 1968

According to an observational program of all lunar eclipses visible from La Plata it was photo-electrically measured an area of the Mare Crisium during the total eclipse of April 12-13,1968.Asociación Argentina de Astronomí

Photoelectric results of the total lunar eclipse of April 12-13, 1968

According to an observational program of all lunar eclipses visible from La Plata it was photo-electrically measured an area of the Mare Crisium during the total eclipse of April 12-13,1968.Asociación Argentina de Astronomí

Tuning the conductance of molecular junctions: transparent versus tunneling regimes

We present a theoretical study of the transport characteristics of molecular junctions, where first-row diatomic molecules are attached to (001) gold and platinum electrodes. We find that the conductance of all of these junctions is of the order of the conductance quantum unit $G_0$, spelling out that they belong to the transparent regime. We further find that the transmission coefficients show wide plateaus as a function of the energy, instead of the usual sharp resonances that signal the molecular levels in the tunneling regime. We use Caroli's model to show that this is a rather generic property of the transparent regime of a junction, which is driven by a strong effective coupling between the delocalized molecular levels and the conduction channels at the electrodes. We analyse the transmission coefficients and chemical bonding of gold/Benzene and gold/Benzene-dithiolate (BDT) junctions to understand why the later show large resistances, while the former are highly conductive.Comment: 9 pages, 7 figure

Virtual reality body exposure therapy for anorexia nervosa. A case report with follow-up results

Objective: Exposure-based therapies such as mirror exposure may help to improve the results of classic cognitive behavioral therapy in anorexia nervosa (AN). Virtual reality (VR)-based procedures provide interesting novelties for targeting body-related concerns. This study aimed to provide preliminary evidence of the usefulness of a VR body exposure therapy in a patient diagnosed with AN. Method: Fear of gaining weight (FGW), body anxiety, drive for thinness, body image disturbances, body mass index and body-related attentional bias were assessed before and after the intervention, as well as five months later. Five sessions of VR body exposure therapy were included within the standard course of cognitive behavioral therapy. The sessions involved a systematic and hierarchical exposure of the patient to a virtual representation of her own silhouette, with the body mass index of the avatar progressively increasing in subsequent sessions. Results: After the intervention, there was a clear reduction in AN symptoms such as the FGW, drive for thinness, body-related anxiety and dissatisfaction. Body mass index values rose continuously during the intervention and reached healthy levels. Finally, there was a notable change in the dysfunctional body-related attentional bias. Almost all these improvements were maintained after five months, except for the FGW. Conclusion: To the best of our knowledge, this study is the first to focus on treating the FGW and body-related concerns in AN using a VR-based paradigm. To pursue this study further and assess the effectiveness of this new VR software, larger controlled clinical trials are needed

Where Should I Submit My Work for Publication? An Asymmetrical Classification Model to Optimize Choice

[EN] Choosing a journal to publish a work is a task that involves many variables. Usually, the authors' experience allows them to classify journals into categories, according to their suitability and the characteristics of the article. However, there are certain aspects in the choice that are probabilistic in nature, whose modelling may provide some help. Suppose an author has to choose a journal from a preference list to publish an article. The researcher is interested in publishing the paper in a journal with a rank number less than or equal to k. For this purpose, a simple classification model is presented in order to choose the best journal from the list, from which some fundamental consequences can be deduced and simple rules derived. For example, if the list contains 100 journals and is ordered using 2-year impact factor, the rule "send to the journal at the k - 10 position" is adequate.Ferrer Sapena, A.; Calabuig, JM.; García-Raffi, LM.; Sánchez Pérez, EA. (2020). Where Should I Submit My Work for Publication? An Asymmetrical Classification Model to Optimize Choice. Journal of Classification. 37:490-508. https://doi.org/10.1007/s00357-019-09331-7S49050837Althouse, B.M., West, J.D., Bergstrom, C.T., Bergstrom, T. (2009). Differences in impact factor across fields and over time. Journal of the Association for Information Science and Technology, 60(1), 27–34.Black, S. (2012). How much do core journals change over a decade? Library Resources and Technical Services, 56, 80–93.Bradshaw, C.J., & Brook, B.W. (2016). How to rank journals. PloS One, 11 (3), e0149852.Ferrer-Sapena, A., Diaz-Novillo, S., Sánchez-Pérez, E.A. (2017). Measuring time-dynamics and time-stability of Journal Rankings in Mathematics and Physics by Means of Fractional p-Variations. Publications, 5(3), 21.Ferrer-Sapena, A., Sánchez-Pérez, E.A., González, L.M., Peset, F., Aleixandre-Benavent, R. (2015). Mathematical properties of weighted impact factors based on measures of prestige of the citing journals. Scientometrics, 105(3), 2089–2108.Ferrer-Sapena, A., Sánchez-Pérez, E.A., González, L.M., Peset, F., Aleixandre-Benavent, R. (2016). The impact factor as a measuring tool of the prestige of the journals in research assessment in mathematics. Research Evaluation, 25(3), 306–314.Gastel, B., & Day, R.A. (2016). How to write and publish a scientific paper. Santa Barbara: ABC-CLIO.Gibbs, A. (2016). Improving publication: advice for busy higher education academics. International Journal for Academic Development, 21(3), 255–258.Grabisch, M.M., Marichal, J.L., Mesiar, R., Pap, E. (2009). Aggregation functions. Cambridge: Cambridge University Press.Haghdoost, A., Zare, M., Bazrafshan, A. (2014). How variable are the journal impact measures?. Online Information Review, 38, 723–737.Hol, E.M. (2013). Empirical studies on volatility in international stock markets. Berlin: Springer.Kelly, J.L. Jr. (2011). A new interpretation of information rate. Manuscript. Reprinted in: The Kelly capital growth investment criterion: theory and practice (pp. 25–34).Klement, E.P., Mesiar, R., Pap, E. (2000). Triangular norms. Dordrecht/Boston/London: Kluwer Academic Publishers.Klement, E.P., Mesiar, R., Pap, E. (2001). Uniform approximation of associative copulas by strict and non-strict copulas. Illinois Journal of Mathematics, 45 (4), 1393–1400.Lawrence, P.A. (2003). The politics of publication. Nature, 422(6929), 259–261.Lu, J., Wu, D., Mao, M., Wang, W., Zhang, G. (2015). Recommender system application developments: a survey. Decision Support Systems, 74, 12–32.Mansilla, R., Köppen, E., Cocho, G., Miramontes, P. (2007). On the behavior of journal impact factor rank-order distribution. Journal of Informetrics, 1, 155–160.Murtagh, F., Orlov, M., Mirkin, B. (2018). Qualitative judgement of research impact: Domain taxonomy as a fundamental framework for judgement of the quality of research. Journal of Classification, 35, 5–28.Neff, B.D., & Olden, J.D. (2010). Not so fast: inflation in impact factors contributes to apparent improvements in journal quality. BioScience, 60(6), 455–459.Nelsen, R.B. (1999). An introduction to copulas. New York: Springer.Pajić, D. (2015). On the stability of citation-based journal rankings. Journal of Informetric, 9, 990–1006.Shannon, C.E. (1948). A mathematical theory of communication. The Bell System Technical Journal, 27, 379–423. Reprinted in: ACM SIGMOBILE Mobile Computing and Communications Review, 5(1)(2001), 3-55.Xu, H., Martin, E., Mahidadia, A. (2014). Contents and time sensitive document ranking of scientific literature. Journal of Informetrics, 8, 546–561

Physical and chemical characterization of cerium(IV) oxide nanoparticles

Chemical composition, size and structure of the nanoparticle are required to describe nanoceria. Nanoparticles of similar size and Ce(III) content might exhibit different chemical behaviour due to their differences in structure. A simple and direct procedure based on affordable techniques for all the laboratories is presented in this paper. The combination of Raman and UV-vis spectroscopy and particle impact coulometry (PIC) allows the characterization of nanoceria of small size from 4 to 65 nm at a concentration from micromolar to nanomolar, a concentration range suitable for the analysis of lab-prepared or commercial nanoparticle suspensions, but too high for most analytical purposes aimed at nanoparticle monitoring. While the PIC limits of size detection are too high to observe small nanoparticles unless catalytic amplification is used, the method provides a simple means to study aggregation of nanoparticles in the media they are needed to be dispersed for each application. Raman spectroscopy provided information about structure of the nanoparticle, and UV-vis about their chemical behaviour against some common reducing and oxidizing agents