Light-induced control of the spin distribution on Cu–dithiolene complexes: A correlated ab initio study

Metal dithiolene complexes—M(dmit)2—are key building blocks for magnetic, conducting, and optical molecular materials, with singular electronic structures resulting from the mixing of the metal and dmit ligand orbitals. Their use in the design of magnetic and conducting materials is linked to the control of the unpaired electrons and their localized/delocalized nature. It has been recently found that UV–Vis light can control the spin distribution of some [Cu(dmit)2]−2 salts in a direct and reversible way. In this work, we study the optical response of these salts and the origin of the differences observed in the EPR spectra under UV–Vis irradiation by means of wave function-based quantum chemistry methods. The low-lying states of the complex have been characterized and the electronic transitions with a non-negligible oscillator strength have been identified. The population of the corresponding excited states promoted by the UV–Vis absorption produces significant changes in the spin distribution, and could explain the changes observed in the system upon illumination. The interaction between neighbor [Cu(dmit)2]−2 complexes is weakly ferromagnetic, consistent with the relative orientation of the magnetic orbitals and the crystal packing, but in disagreement with previous assignments. Our results put in evidence the complex electronic structure of the [Cu(dmit)2]−2 radical and the relevance of a multideterminantal approach for an adequate analysis of their properties. © 2019 by the authors.Departamento Administrativo de Ciencia, Tecnología e Innovación, COLCIENCIAS: 1411712-51515, Ministerio de Economía y Competitividad, Federación Española de Enfermedades Raras: CTQ-2015-69019-

Theoretical study of the photoconduction and photomagnetism of the BPY[Ni(dmit)2]2 molecular crystal

The BPY[Ni(dmit)2]2 molecular crystal synthesized by Naito and coworkers (J. Am. Chem. Soc., 2012, 134, 18656) was characterized as a photo-magnetic-conductor. This crystal is a nonmagnetic semiconductor in the dark and becomes a magnetic conductor after UV irradiation. This work analyzes the key ingredients of the observed photomagnetism and photoconduction by means of wavefunction-based calculations on selected fragments and periodic calculations on the whole crystal. Our results demonstrate that UV-Vis light induces charge transfer processes between the closest [Ni(dmit)2]− and BPY2+ units, that introduce unpaired electrons on the unoccupied orbitals of the BPY cations. Since the conduction bands present a strong mixing of BPY and Ni(dmit)2, the optically activated anion–cation charge transfer enhances the conductivity. The photoinduced (BPY2+)* radicals can indeed interact with the close Ni(dmit)2 units, with non-negligible spin–spin magnetic couplings, which are responsible for the changes induced by the irradiation on the temperature dependence of the magnetic susceptibility.Ministerio de Economía y Competitividad de España y fondos FEDER. CTQ-2015-69019-

Approximate modelling of the multi-dimensional learner

This paper describes the design of the learner modelling component of the LeActiveMath system, which was conceived to integrate modelling of learners' competencies in a subject domain, motivational and affective dispositions and meta-cognition. This goal has been achieved by organising learner models as stacks, with the subject domain as ground layer and competency, motivation, affect and meta-cognition as upper layers. A concept map per layer defines each layer's elements and internal structure, and beliefs are associated to the applications of elements in upper-layers to elements in lower-layers. Beliefs are represented using belief functions and organised in a network constructed as the composition of all layers' concept maps, which is used for propagation of evidence

Open Data in action: Initiatives during the initial stage of the COVID-19 pandemic

The COVID-19 pandemic has increased the demand for access to timely, relevant, and quality data. This demand has been driven by several needs: taking informed policy actions quickly, improving communication on the current state of play, carrying out scientific analysis of a dynamic threat, understanding its social and economic impact, and enabling civil society oversight and reporting. Based on an open call for evidence, this report assesses how open government data (OGD) was used to react and respond to the COVID-19 pandemic during initial stage of the crisis (March-July 2020). It also seeks to transform lessons learned into considerations for policy makers on how to improve OGD policies to better prepare for future shocks

QuizMap: Open social student modeling and adaptive navigation support with TreeMaps

In this paper, we present a novel approach to integrate social adaptive navigation support for self-assessment questions with an open student model using QuizMap, a TreeMap-based interface. By exposing student model in contrast to student peers and the whole class, QuizMap attempts to provide social guidance and increase student performance. The paper explains the nature of the QuizMap approach and its implementation in the context of self-assessment questions for Java programming. It also presents the design of a semester-long classroom study that we ran to evaluate QuizMap and reports the evaluation results. © 2011 Springer-Verlag Berlin Heidelberg

Leishmaniasis in cats: more important than we believe?

Leishmaniasis is one of the world, neglected tropical diseases (NTD), recently, celebrated its day (January 30, 2020). Infection due to Leishmania is a major public health problem in many tropical countries; due to its high incidence and wide geographical distribution [1]. Both domestic and wild animals may serve as host reservoirs of Leishmania spp [2]. The Role of dogs in the zoonotic cycle of Leishmania spp, especially in urban and peri-urban areas, has long been understood. Nevertheless, recent studies have detected Leishmania infections in domestic cats

Identification and expression pattern of a new carotenoid cleavage dioxygenase gene member from Bixa orellana

Carotenoid cleavage dioxygenases (CCDs) are a class of enzymes involved in the biosynthesis of a broad diversity of secondary metabolites known as apocarotenoids. In plants, CCDs are part of a genetic family with members which cleave specific double bonds of carotenoid molecules. CCDs are involved in the production of diverse and important metabolites such as vitamin A and abscisic acid (ABA). Bixa orellana L. is the main source of the natural pigment annatto or bixin, an apocarotenoid accumulated in large quantities in its seeds. Bixin biosynthesis has been studied and the involvement of a CCD has been confirmed in vitro. However, the CCD genes involved in the biosynthesis of the wide variety of apocarotenoids found in this plant have not been well documented. In this study, a new CCD1 gene member (BoCCD1) was identified and its expression was charaterized in different plant tissues of B. orellana plantlets and adult plants. The BoCCD1 sequence showed high homology with plant CCD1s involved mainly in the cleavage of carotenoids in several sites to generate multiple apocarotenoid products. Here, the expression profiles of the BoCCD1 gene were analysed and discussed in relation to total carotenoids and other important apocarotenoids such as bixin

Poly (lactic acid)/D-limonene/ZnO bio-nanocomposites with antimicrobial properties

Antimicrobial films of poly (lactic acid) (PLA)/D-limonene/zinc oxide (ZnO)-based bio-nanocomposites were prepared via melt compounding and subsequent thermocompression. D-limonene was incorporated at concentrations of 10 or 20 wt%, and ZnO pure nanoparticles and those organically modified with oleic acid (O-ZnO), with an average diameter of 13.5 nm, were included at concentrations of 3, 5, and 8 wt%. The plasticizing effect of D-Limonene was corroborated by a decrease in the glass transition temperature compared to pure PLA. The presence of ZnO and O-ZnO in the PLA matrix promoted a slight increase in the degree of crystallinity due to its nucleant performance. Although ZnO and O-ZnO induced lower thermal stability and slightly decreased microhardness in the composites, excellent antimicrobial performance was demonstrated. Both ZnO and O-ZnO nanocomposites reached 99.9% of effectiveness for nanoparticles content above 5 wt%, regardless of the source of irradiation, D-limonene concentration, and nanoparticle modification. Therefore, these bio-nanocomposites will allow for future advances in sustainable antimicrobial materials for the medical or food packaging fields.DICYT, Grant/Award Number: Project 022041ZR_POSTDOCT; Fondo Nacional de Desarrollo Científico y Tecnológico,Grant/Award Numbers: 1170226, 320029

Optical Properties of Multilayered Sol–Gel Zinc-Oxide Films

Study of structural, optical and photocatalytic properties of multilayered (1–8 layers) zinc oxide films deposited on glass substrates by sol-gel method showed, that after thermal treatment at 500°C they consist of random oriented hexagonal crystalline grains with size of 34–40 nm, forming larger particles with sizes of 100–150 nm, which do not depend on number of layers. With an increase in the number of layers, the intensity of exciton photoluminescence decreases by a factor of 10, the absorption of light in the visible and near IR ranges increases, and the efficiency of photocatalytic decomposition of the test organic dye rhodamine B increases by 10–12%. The observed changes are related to the increase in the total area of grain boundaries and to the change in the integral amount of oxygen vacancies and interstitial atoms as the number of layers increases, which makes it possible to control the properties of zinc oxide films for applications in optoelectronics, photovoltaics and photocatalysis