Synthesis and characterization of NaNiF3·3H2O: An unusual ordered variant of the ReO3 type

et al.A new hydrated sodium nickel fluoride with nominal composition NaNiF3·3H2O was synthesized using an aqueous solution route. Its structure was solved by means of ab initio methods from powder X-ray diffraction and neutron diffraction data. NaNiF3·3H2O crystallizes in the cubic crystal system, space group Pn3̅ with a = 7.91968(4) Å. The framework, derived from the ReO3 structure type, is built from NaX6 and NiX6 (X = O, F) corner-shared octahedra, in which F and O atoms are randomly distributed on a single anion site. The 2a × 2a × 2a superstructure arises from the strict alternate three-dimensional linking of NaX6 and NiX6 octahedra together with the simultaneous tilts of the octahedra from the cube axis (φ = 31.1°), with a significant participation of hydrogen bonding. NaNiF3·3H2O corresponds to a fully cation-ordered variant of the In(OH)3 structure, easily recognizable when formulated as NaNi(XH)6 (X = O, F). It constitutes one of the rare examples for the a+a+a+ tilting scheme with 1:1 cation ordering in perovskite-related compounds. The Curie-like magnetic behavior well-reflects the isolated paramagnetic Ni2+ centers without worth mentioning interactions. While X-ray and neutron diffraction data evidence Na/Ni order in combination with O/F disorder as a main feature of this fluoride, results from Raman and magic-angle spinning NMR spectroscopies support the existence of specific anion arrangements in isolated square windows identified in structural refinements. In particular, formation of water molecules derives from unfavorable FH bond formation.We thank Ministerio de Ciencia e Innovación and Comunidad de Madrid for funding Project Nos. MAT2010-19837-C06 and P2009/PPQ-1626, respectively. Financial support from Universidad CEU San Pablo is also acknowledged.Peer reviewe

Relaciones interpersonales y clima laboral en los docentes de la Universidad Católica de Trujillo-2017

El presente informe de investigación es producto de nuestros esfuerzos en conjunto, al anhelar resolver de qué manera se relaciona el clima laboral y las relaciones interpersonales ya que es un tema que nos afecta a nosotras como profesionales, dentro de una institución y a las demás docentes que investigamos de esta universidad, esto nos permite no solo conocer la realidad de esta empresa educativa sino de las demás y saber cuál es la causa de estos problemas y así poder tomar medidas de solución por ello el propósito de la presente tesis es DETERMINAR LA RELACIÓN QUE EXISTE ENTRE LAS RELACIONES INTERPERSONALES Y EL CLIMA LABORAL EN LOS DOCENTES DE LA UNIVERSIDAD CATÓLICA DE TRUJILLO-2017. Se realizó la investigación empleando un diseño no experimental, descriptivo correlacional, con una muestra de cincuenta docentes, se utilizó un muestreo con un solo grupo con un método empírico y estadístico aleatorio; el procesamiento estadístico ha sido elaborado en base a la aplicación de un test del clima laboral y relaciones interpersonales, mediante un cuestionario, la cual está compuesta de 4 Ítems con 5 indicadores por cada ítems, donde los ítems son calificados a base de escala valorativa como: Totalmente de acuerdo, de acuerdo, medianamente de acuerdo, en desacuerdo y totalmente en desacuerdo y los resultados han sido ubicados en los intervalos de cada respuesta entrevistada en relación a cada sub-Ítems, donde son considerados dentro de un ítem. En relación a la discusión de resultados y la conclusión de los antecedentes y el contraste de la hipótesis, donde se llega a la conclusión que si existe relación directa entre la variable 1 y la variable 2 de los docentes de la Universidad Católica de Trujillo.Tesi

Density Functional Theory Modeling of Solid-State Nuclear Magnetic Resonances for Polycyclic Aromatic Hydrocarbons

Experimental solid-state nuclear magnetic resonance (SS-NMR) has been used to analyze different theoretical models for polycyclic aromatic hydrocarbon crystals of similar structure (naphthalene, anthracene, phenanthrene, picene, and triphenylene). We compare the accuracy of four modeling approaches to compute SS-NMR chemical shifts using ab initio density functional theory (DFT). Models based on X-ray cell parameters, on optimization of the cell with the Perdew, Burke, and Ernzerhof (PBE) approximation, and on two methods adding dispersion forces were compared (using Pearson’s and mean absolute deviation correlation factors). Even though the intermolecular distances and cell volumes are different depending on the model, there is an overall good agreement between theoretical and experimental 13C chemical shifts for all of them. An analysis of intermolecular distances and deviation from planarity in different models and their influence on theoretical chemical shieldings is also performed.We acknowledge funding from C. Madrid (Grant S2013/MIT-2753), MINECO (Grants MAT2014-54231, MAT2016-78625-C2-2P, MAT2016-78362-C4-2-R, and FIS2015-6422-C2-1-P), EU (Grant ERC-2013-SYG-610256 NANOCOSMOS), Generalitat Valenciana (Grant PROMETEO/2017/139); the University of Alicante and computing resources from CTI-CSIC

Plan de negocio para la viabilidad comercial operativa y econ?mica de agregados para el mercado de Lima Norte para la empresa Factra

El presente plan de negocio tiene como objetivo demostrar la viabilidad comercial, operativa y econ?mica para la comercializaci?n de agregados de construcci?n en la empresa Factra S.A para abastecer a los distritos que conforman Lima Norte. Para tal efecto se plantean los siguientes objetivos: - Evaluar el mercado de agregados de construcci?n en la zona de Lima Norte. - Desarrollar una investigaci?n de mercado para estimar la demanda potencial de agregados de construcci?n incluyendo el precio y los atributos m?s valorados por los clientes de Lima Norte. - Analizar el entorno de la empresa Factra S.A para detectar oportunidades y amenazas a fin de establecer el atractivo del mercado. - Analizar a la empresa Factra S.A para detectar sus fortalezas y debilidades a fin de establecer sus capacidades. - Establecer las acciones estrat?gicas para implementar la idea de negocio. - Desarrollar el plan de marketing y operativo para implementar la idea de negocio. - Determinar la viabilidad econ?mica y efectuar el an?lisis de riesgos de la idea de negocio

Evidence of hydrogen content and monovalent Ni oxidation state in non-superconducting bulk anchored infinite-layer nickelates

Since superconductivity was first reported in nickelate thin films, many studies have been published about this family of materials, and different hypotheses have been proposed for explaining the mechanisms and structural dependence. Here, we report the synthesis of anchored infinite-layer LaNi0.9Al0.1O2.1 and its hole-doped derivatives by topotactic reduction from La1−xSrxNi0.9Al0.1O3 rhombohedral perovskites. LaNiO2 derivatives constitute a new family of high-temperature superconductors, with the same structure as high-Tc cuprates but based on nickel, only showing superconductivity in thin films for now. We describe a strategy to stabilize LaNiO2 derivatives in bulk: the presence of Al at the octahedral sites helps to stabilize/anchor the infinite-layer structure. The reasons for the bulk being non-superconductors are hotly debated in the literature. An important question is whether there is some hydrogen incorporated into the structure during the reduction process from LaNiO3 to LaNiO2, predicted theoretically but not reported experimentally. Our neutron powder diffraction data show that, indeed, hydrogen occupies the centers of the Ni–O squares, and spectroscopic evidence from EELS and XAS suggests that Ni is reduced to the Ni+ oxidation state, consistent with the crystallochemical data. © 2023 The AuthorsJ.E.F.S.R. thanks Dr. Carlos Pecharroman and the Service of IR spectroscopy and ellipsometry of the ‘‘Instituto de Ciencia de Materiales de Madrid-CSIC’’ for FTIR measurements. The authors wish to express their gratitude to the ILL and the European Synchrotron Radiation Facility (ESRF) for making all facilities available for neutron and synchrotron diffraction experiments (ESRF proposal HC-4990 in ID22 and in-house beamtime in BM23). Electron microscopy observations were carried out at the Centro Nacional de Microscopia Electronica (CNME-UCM). We are thankful for funding from the Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033) with grant nos. PID2021-122477OB-I00, TED2021-129254B-C21, and TED2021-129254B-C22. J.G. thanks MCIN for granting the contract PRE2018-083398. F.S.-S. is thankful for the grant RYC2021- 033518-I, funded by NextGenerationEU and MICIN.Supplemental information can be found online at https://doi.org/10.1016/j.xcrp. 2023.101724.Peer reviewe

Microstructural and Mechanical Properties of Alkali Activated Colombian Raw Materials

Microstructural and mechanical properties of alkali activated binders based on blends of Colombian granulated blast furnace slag (GBFS) and fly ash (FA) were investigated. The synthesis of alkali activated binders was conducted at 85 °C for 24 h with different slag/fly ash ratios (100:0, 80:20, 60:40, 40:60, 20:80, and 0:100). Mineralogical and microstructural characterization was carried out by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) and Nuclear magnetic resonance (NMR). Mechanical properties were evaluated through the compressive strength, modulus of elasticity and Poisson’s ratio. The results show that two different reaction products were detected in the slag/fly ash mixtures, a calcium silicate hydrate with Al in its structure (C-A-S-H gel) and a sodium aluminosilicate hydrate (N-A-S-H gel) with higher number of polymerized species and low content in Ca. It was found that with the increase of the amount of added slag, the amount of C-A-S-H gel increased and the amount of N-A-S-H gel decreased. The matrix was more dense and compact with almost absence of pores. The predominance of slag affected positively the compressive strength, Young’s modulus and Poisson’s ratio, with 80% slag and 20% fly ash concrete being the best mechanical performance blend.We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).Maria Criado expresses her gratitude to the Spanish Ministry of Science and Innovation for the Juan de la Cierva (Reference JDC-2010) contract. Willian Aperador acknowledges the funding received by the Vice-Rector for Research of the University Militar Nueva Granada, ING 1572

Polysiloxane hybrids via sol-gel process: Effect of temperature on network formation

This article belongs to the Special Issue Thin and Thick Films: Deposition, Characterization and Applications.The effect of temperature on the network formation of polysiloxane hybrids was evaluated since this type of material is currently in high demand. In the last decades, the deposition of these coatings on different substrates, mostly metals, has demonstrated anticorrosion properties. Sol-gel hybrids were prepared by mixing 3-methacryloxypropyltrimethoxysilane (MPTS) and tetramethyl orthosilicate (TMOS) with a molar ratio of 1. The formation, thickness and composition of these hybrid materials were evaluated by nuclear magnetic resonance (NMR) spectroscopy and scanning electron microscopy (SEM), respectively. The results showed that the temperature plays an important role in the network formation, the total condensation degree and the total dimensionality of the hybrid materials. At room temperature, the polysiloxane hybrids presented total condensation degrees lower than 75% and a total dimensionality (dtotal) = 2.5, while those obtained at 65 °C presented total condensation degrees higher than 80% and a dtotal = 2.8. The ideal conditions to prepare polysiloxane hybrids are 65 °C for 4 h, where this shows a higher atomic percentage of Si and a greater thickness.This research received external funding from Project MAT2016-78362-C4-2-R financed by MICINN, Spain.Peer reviewe

Medium-range order in disordered K-feldspars by multinuclear NMR

The structures of K-rich feldspar, (K>Na)AlSi3O8, are currently described as >ideal> crystals with periodic average structures from Bragg diffraction maxima obtained by reciprocal-space techniques. Polymorphism is explained by variable substitutional disorder of framework Si and Al cations in tetrahedral T sites, and positional disorder of cavity alkali cations in a single M site. Here, high-resolution magic angle spinning multinuclear magnetic resonance spectroscopy, leading to 29Si, 27Al, and 23Na spectra at 9.4 as well as 27Al, 39K, and 23Na spectra at 19.6 T, has been used to investigate the >real> structures along the order-disorder series of K-feldspar crystals. The >ideal> and >real> structure coincides only in the perfectly long-range ordered triclinic end-member of the low-microcline structure. Long-range disordered structures (either with monoclinic or triclinic symmetry by X-ray diffraction) show non-random disorder at the medium-range scale, triclinic-like distortions with four sets of T sites for framework atoms, two sets of M sites for alkali atoms, and Al-O-(K,Na) multi-site correlations by NMR spectroscopy. The K-feldspar structures can be described by a medium-range structure using the number of Al atoms per four-membered rings of tetrahedra, with >...-2-0-2-0-...> chains for microcline and orthoclase where the Al-occupancies t1O > t2m > t2O ≈ t1m, and with >...-1-1-1-1-...> chains for valencianite and sanidine, in which t1O > t2m ≈ t2O ≈ t1m. Framework cations respect Loewenstein's rule (Al-O-Al avoidance), as well as some additional constraints of charge dispersion involving deficiency of Si atoms in Q4 (4Si,0Al), (1Si,3Al), and (0Si,4Al) environments, constraints which are particularly strong in valencianite. These >real> structure features cannot be described by >ideal> structures owing to the lack of resolving power of the reciprocal-space techniques.Peer Reviewe