1,231 research outputs found

    Tris(2-pyridyl) Bismuthines: Coordination Chemistry, Reactivity, and Anion-Triggered Pyridyl Coupling

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    Producción CientíficaA series of new tris(2-pyridyl) bismuthine ligands of the type [Bi(2-py′)3] have been prepared, containing a range of substituents at various positions within their pyridyl rings (py′). They can act as intact ligands or, as a result of the low C–Bi bond energy, exhibit noninnocent reactivity in the presence of metal ions. Structural studies of Li+ and Ag+ complexes show that the coordination to metal ions using their pyridyl-N atoms and to anions using the Lewis acidity of their Bi(III) centers can be modified by the presence of substituents within the 2-pyridyl rings, especially at the 6- or 3-positions, which can block the donor-N or Lewis acid Bi sites. Electron withdrawing groups (like CF3 or Br) can also severely reduce their ability to act as ligands to metal ions by reducing the electron donating ability of the pyridyl-N atoms. Noninnocent character is found in the reactions with Cu+ and Cu2+, resulting in the coupling of pyridyl groups to form bipyridines, with the rate of this reaction being dependent on the anion present in the metal salts. This leads to the formation of Bi(III)/Cu(I) complexes containing hypervalent [X2Bi(2-R-py)]− (X = Cl, Br) anions. Alternatively, the tris(2-pyridyl) bismuthine ligands can act as 2-pyridyl transfer reagents, transferring 2-py groups to Au(I) and Fe(II).Ministerio de Ciencia, Innovación y Universidades (project numbers PGC2018-096880-A-I00, MCIU/AEI/FEDER, UE and PGC2018-099470-B-I00,MCIU/AEI/FEDER, UE)Ministerio de Economía, Industria y Competitividad (Project RYC-2015-19035

    The coordination chemistry of the neutral tris-2-pyridyl silicon ligand [PhSi(6-Me-2-py)3]

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    Producción CientíficaDifficulties in the preparation of neutral ligands of the type [RSi(2-py)3] (where 2-py is an unfunctionalised 2-pyridyl ring unit) have thwarted efforts to expand the coordination chemistry of ligands of this type. However, simply switching the pyridyl substituents to 6-methyl-pyridyl groups (6-Me-2-py) in the current paper has allowed smooth, high-yielding access to the [PhSi(6-Me-2-py)3] ligand (1), and the first exploration of its coordination chemistry with transition metals. The synthesis, single-crystal X-ray structures and solution dynamics of the new complexes [{PhSi(6-Me-2-py)3}CuCH3CN][PF6], [{PhSi(6-Me-2-py)3}CuCH3CN][CuCl2], [{PhSi(6-Me-2-py)3}FeCl2], [{PhSi(6-Me-2-py)3}Mo(CO)3] and [{PhSi(6-Me-2-py)3}CoCl2] are reported. The paramagnetic Fe2+ and Co2+ complexes show strongly shifted NMR resonances for the coordinated pyridyl units due to large Fermi-contact shifts. However, magnetic anisotropy also leads to considerable pseudo-contact shifts so that both contributions have to be included in the paramagnetic NMR analysis.The Leverhulme Trust (Grant for DSW and RG-R, postdoctoral funding for ALC, RGP-2017-146Ministerio de Economía, Industria y Competitividad - Agencia Estatal de Investigación (AEI)European Social Fund (ESF)Ramón y Cajal contract (RG-R, RYC-2015–19035

    Portuguese version of the oviedo grit scale: Adaptation, validation, and relationship with educational variables

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    El grit es una variable importante para predecir indicadores de éxito en diversos contextos entre los que se encuentra el académico. Sin embargo, son escasos los instrumentos de medida de grit bien validados en apoyo a la investigación. El objetivo del presente estudio es consolidar la validación de la Escala Grit de Oviedo (EGO) presentando datos de su validación en Portugal. Se empleó una muestra de 285 participantes portugueses (Maños= 18.46; DTaños= 1.30). Además, se empleó una muestra de población española para analizar la invarianza de medida (330 participantes; Maños= 23.01 y DTaños= 3.22). Se confirmó la unidimensionalidad de la escala EGO en el contexto portugués, mostrando además invarianza escalar entre ambas poblaciones. La fiabilidad de la escala EGO fue excelente (ω =.96), y mostró una correlación moderada con el bienestar subjetivo (r = .28) y con la confianza para terminar el curso académico (r = .33). La escala EGO puede ser empleada para estudiar el grit en Portugal.Grit is an important variable to predict success indicators in various contexts, including academia. However, there are few instruments for measuring grit to support research. The aim of this study is to consolidate the validation of Oviedo Grit Scale (EGO for its acronym in Spanish) namely taking its validation in Portugal. A sample of 285 Portuguese participants was used (Myears = 18.46; SDyears = 1.30). In addition, a sample of the Spanish population was used to analyze the measurement invariance (330 participants; Myears = 23.01 and SDyears = 3.22). The unidimensionality of the EGO scale was confirmed in the Portuguese context, also showing scalar invariance between both populations. The reliability of the EGO scale was excellent (ω = .96), and it showed a moderate correlation with subjective well-being (r = .28) and with confidence to finish the academic year (r = .33). The EGO scale can be used to study grit in Portugal

    Evaluación de algunos métodos para la extracción de zinc disponible en suelos alcalinos del valle del cauca

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    Se determinó el contenido de zinc disponible por varios métodos de extracción y se trató de establecer en una primera aproximación el nivel crítico de este elemento, en 20 suelos alcalinos (Vertisol, Mollisol, Inceptisol y Entisol) de la zona plana del Valle del Cauca. El orden de eficiencia de las ocho soluciones extractoras fue: HCL 0.1 N and gt; EDTA 0.05 M and gt; (NH4hC03 +EDTA and gt; Olsen Modificado and gt; DTPA - CaCI2- TEA = NH4HC03 DTPA = Carolina del Norte and gt; HCl 0.05 N. Los niveles críticos de zinc en el suelo estuvieron por debajo de los siguientes valores: Olsen Modificado (1.8 ppm), (NH4hC03 + EDTA (1.8 ppm), DTPA (1.2 ppm), NH4HC03 + DTPA (1.0 ppm), EDTA 0.05 M (2.2 ppm), Carolina del Norte (1.0 ppm), HCI 0.1 N (3.0 ppm) y HCI 0.05 N (0.15 ppm). En invernadero no se encontró respuesta significativa de los tratamientos (O, 4, 8, 12, 16 Y 20 kg de Zn/ha) sobre el rendimiento de materia seca del híbrido 8239 de sorgo (Sorghum bicolor L. Moench) pero sí en la concentración y contenido foliar de zinc. La concentración de zinc en la planta, determinada por digestión húmeda con mezcla nítrico-perclórica y metanol ácido, estuvo dentro del rango normal establecido para este elemento. Se encontraron correlaciones positivas y altamente significativas entre el contenido de zinc de la planta y el contenido de zinc extraído del suelo por los métodos de Olsen Modificado, DTPA y HCI 0.1 N, los otros métodos presentaron correlaciones positivas, pero no significativas.In order to determine available zinc content using several extraction methods and trying to stablish in a first aproximation the critical level for this element, 20 alkaline soils (Vertisol, Mollisol, Inceptisol, and Entisol) were collected in the Plain Zone of Cauca Valley. Eight solutions were used; their extraction order was: HCI 0.1 N and gt; EDTA 0.05 M and gt; (NH4)2CO3 + EDTA and gt; Modified Olsen and gt; DTPA- CaCl2 - TEA = NH4HC03 + DTPA = North Caroline and gt; HCl0.05 N. It was found that the critical levels are bellow the following values: Olsen Modified (1.8 ppm), (NH4hCO) + EDTA (1.8 ppm), DTPA (1.2 ppm), NH4HC03 + DPTA (1.0 ppm) EDTA 0.05 M (2.2 ppmj. Double Acid (1.0 ppm) HCl0.1 N (3.0 ppm) and HCl0.05 N (0.15 ppm). In the greenhouse study it was found that the zinc application (0, 4, 8, 12, 16 and 20 kg/ha) did not enhance dry matter accumulation in sorghum, hybrid 8239 (Sorghum bicolor L. Moench), but it did increase the foliar concentration, determined by wet digestion using both nitric perchloric acid and acid methanol, and content of this element. The zinc concentration found in the plant was within the normal range given for this element. Significant positive correlations were found between plant zinc content and soil zinc extracted by Modified Olsen, DTP A, and HCI 0.1 N; another methods showed possitive but no significant correlations

    Impact of caries and dental fluorosis on oral health-related quality of life: a cross-sectional study in schoolchildren receiving water naturally fluoridated at above-optimal levels

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    Purpose The purpose of this study was to evaluate the impact of caries and fluorosis on oral health-related quality of life (OHRQoL) among schoolchildren living in areas with high concentrations of fluoride in water. Methods Five hundred and twenty-four schoolchildren (8–12 year olds) residing in rural communities in central Mexico were examined for oral hygiene, caries (International Caries Detection and Assessment System, ICDAS II), and fluorosis (Thylstrup and Fejerskov Index, TFI). OHRQoL was evaluated with the Child Perceptions Questionnaire for two age groups (CPQ8–10 and CPQ11–14). Generalized structural equation models were constructed for data analysis. Results Overall prevalence of caries was 88.5% and fluorosis 46.9%. In the group of 8–10 year olds, 48% of the children had advanced carious lesions in primary or permanent teeth (ICDAS ≥4), 22.6% had moderate/severe fluorosis, and 59.9% of children had an impact on OHRQoL. Schoolchildren with ICDAS ≥4 were more likely [OR = 1.75, (95% CI 1.34–2.28)] to suffer a negative impact on OHRQoL. In the group of 11–12 year olds, 19.9% of children had advanced carious lesions and 23.2% showed moderate/severe fluorosis; 67.3% of children reported had an impact on OHRQoL. Children 11–12 year olds with fluorosis (TFI ≥4) [OR = 2.39 (95% CI 2.12–2.69)], caries (ICDAS ≥4) [OR = 2.18 (95% CI 2.13–2.24)], and low brushing frequency [OR = 2.04 (95% CI 1.21–3.44)] were more likely to have deterioration on OHRQoL. Conclusion A negative impact on OHRQoL was observed in children with caries and fluorosis

    Quantifying the tuneable interactions between colloid supported lipid bilayers

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    Colloid supported lipid bilayers (CSLBs) are formed via the rupture and fusion of lipid vesicles to coat spherical colloidal particles. CSLBs are an emerging vector for the controlled self-assembly of colloids due to the ability to include additives into the bilayer, which influence the (a)specific interactions between particles. To evaluate the specificity of CSLB assembly, first a fundamental study on the tunability of the colloidal interaction and resulting colloidal stability of CSLBs without specific interactions is reported here. It was found that both fluid and gel CSLBs showed significant clustering and attraction, while the addition of steric stabilizers induced a profound increase in stability. The interactions were rendered attractive again by the introduction of depletion forces via the addition of free non-adsorbing polymers. The compositions of fluid and gel CSLBs with 5% membrane stabiliser were concluded to be optimal for further studies where both colloidal stability, and contrasting membrane fluidity are required. These experimental findings were confirmed semi-quantitatively by predictions using numerical self-consistent mean-field theory lattice computations

    On the properties of GaP supersaturated with Ti

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    We have fabricated GaP supersaturated with Ti by means of ion implantation and pulsed-laser melting to obtain an intermediate band material with applications in photovoltaics. This material has a strong sheet photoconductance at energies below the bandgap of GaP and it seems to be passivated by a Ga defective GaPO oxide layer during the laser process. Passivation is consistently analyzed by sheet photoconductance and photoluminescence measurements. We report on the structural quality of the resulting layers and analyze the energy of the new optical transitions measured on GaP:Ti. A collapse found in the sheet photoconductance spectra of GaP:Ti samples fabricated on undoped substrates is explained by the negative photoconductivity phenomenon. (C) 2019 Elsevier B.V. All rights reserved

    A Tris(3‐pyridyl)stannane as a Building Block for Heterobimetallic Coordination Polymers and Supramolecular Cages

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    Producción CientíficaThe systematic assembly of supramolecular arrangements is a persistent challenge in modern coordination chemistry, especially where further aspects of complexity are concerned, as in the case of large molecular mixed‐metal arrangements. One targeted approach to such heterometallic complexes is to engineer metal‐based donor ligands of the correct geometry to build 3D arrangements upon coordination to other metals. This simple idea has, however, only rarely been applied to main group metal‐based ligand systems. Here, we show that the new, bench‐stable tris(3‐pyridyl)stannane ligand PhSn(3‐Py)3 (3‐Py=3‐pyridyl) provides simple access to a range of heterometallic SnIV/transition metal complexes, and that the presence of weakly coordinating counter anions can be used to build discrete molecular arrangements involving anion encapsulation. This work therefore provides a building strategy in this area, which parallels that of supramolecular transition metal chemistry.Ministerio de Economía, Industria y Competitividad - Agencia Estatal de Investigación - Fondo Social Europeo (Ramon y Cajal contract RG‐R, RYC‐2015‐19035)Ministerio de Ciencia, Innovación y Universidades - Agencia Estatal de Investigación - FEDER - Unión Europea (project PGC2018‐096880‐A‐I00)

    Central relaxin-3 receptor (RXFP3) activation increases ERK phosphorylation in septal cholinergic neurons and impairs spatial working memory.

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    The medial septum/diagonal band (MS/DB) is a relay region connecting the hypothalamus and brainstem with the hippocampus, and both the MS/DB and dorsal/ventral hippocampus receive strong topographic GABA/peptidergic projections from the nucleus incertus of the pontine tegmentum. The neuropeptide relaxin-3, released by these neurons, is the cognate ligand for a Gi/o-protein-coupled receptor, RXFP3, which is highly expressed within the MS/DB, and both cholinergic and GABAergic neurons in this region of rat brain receive relaxin-3 positive terminals/boutons. Comprehensive in vitro studies have demonstrated that a range of cell signaling pathways can be altered by RXFP3 stimulation, including inhibition of forskolin-activated cAMP levels and activation of ERK phosphorylation. In this study we investigated whether intracerebroventricular (icv) injection of RXFP3-A2, a selective relaxin-3 receptor agonist, altered ERK phosphorylation levels in the MS/DB of adult male rats. In addition, we assessed the neurochemical phenotype of phosphorylated (p) ERK-positive neurons in MS/DB after RXFP3-A2 administration by dual-label immunostaining for pERK and key neuronal markers. RXFP3-A2 injection significantly increased pERK levels in MS/DB, compared to vehicle at 20 and 90 min post-injection. In addition, icv injection of RXFP3-A2 increased the number of cells expressing pERK in the MS/DB after 90 min, with increases detected in cholinergic, but not GABAergic neurons. Moreover, we found that septal cholinergic neurons express RXFP3 and that icv infusions of RXFP3-A2 impaired alternation in a spatial working memory behavioral paradigm. The presence of the receptor and the specific RXFP3-related activation of the MAPK/ERK pathway in MS/DB cholinergic neurons identifies them as a key target of ascending relaxin-3 projections with implications for the acute and chronic inhibition of cholinergic neuron activity/function by relaxin-3/RXFP3 signaling.This research was supported by a predoctoral fellowship (FPI-UJI: PREDOC/2014/35) to HAG; a traineeship fellowship (UJI P1·1A2014-06) to AGA; the FP7-PEOPLE-IRSES PIRSES-GA-2012-318997 NEUREN project to ALG and FEO-B; NHMRC (Australia) project grants (1027522, 1026939) and a Brain and Behavior Research Foundation (USA) NARSAD Independent Investigator Award to ALG; Generalitat Valenciana (AICO/2015/042) project grant and Universitat Jaume I (P1·1A2014-06) project grant to AMS
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