Frequency and voltage partitioning in presence of renewable energy resources for power system (example: North Chile power network)

This paper investigates techniques for frequency and voltage partitioning of power network based on the graph-theory. These methods divide the power system into distinguished regions to avoid the spread of disturbances and to minimize the interaction between these regions for frequency and voltage control of power system. In case of required active and reactive power for improving the performance of the power system, control can be performed regionally instead of a centralized controller. In this paper, renewable energy sources are connected to the power network to verify the effect of these sources on the power systems partitioning and performance. The number of regions is found based on the frequency sensitivity for frequency partitioning and bus voltage for voltage partitioning to disturbances being applied to loads in each region. The methodology is applied to the north part of Chile power network. The results show the performance and ability of graph frequency and voltage partitioning algorithm to divide large scale power systems to smaller regions for applying decentralized controllers.Peer ReviewedPostprint (published version

Design And Validation Of An Instrument To Assess A Didactic Sequence Directed To Promote The Development Of Critical Thinking

The text responds to the validation of an instrument that has been designed to evaluate the quality of an intervention proposal aimed at promoting the development of critical thinking in students of the competence assessment diploma of the degree programs of the Caribbean University Corporation CECAR. The design was subjected to a process that began with the validation of the judges, obtaining data that were subjected to the protocol of Lawshe (1975) modified by Tristán (2008), which allowed calculating the content validity index of the instrument 0.829 or 82 , 9%, which confirms the seven proposed dimensions. Also, some recommendations from the judges regarding the writing of some items were accepted. The instrument was then subjected to the process of statistical validity by doing a pilot test with 20 products, initially calculating Cronbach's alpha of 0.912, which shows a high consistency of the construct items. Subsequently, the Guttman and Spearman-Brown reliability coefficients were determined, obtaining values ​​of the coefficient of the two halves of the construct of 0.998 that show high reliability. And at the end, the goodness of fit test of the model was carried out, estimating the variance error, common variance and true variance, estimated common inter-element correlation, estimated reliability and estimation of unbiased reliability, obtaining values ​​that demonstrate high reliability and internal consistency

A surfactant concentration model for the systematic determination of the critical micellar concentration and the transition width

The critical micellar concentration (cmc) is a fundamental property of surfactant solutions. Many proposed methods for the definition and determination of the cmc from property-concentration plots yield values, which depend on the studied property, on the specific technique used for its analysis and in many cases on the subjective choice of the chosen type of plot and concentration interval. In this focus review, we revise the application of a surfactant concentration model we proposed earlier that defines the cmc directly based on the surfactant concentration. Known equations for the concentration-dependence of different surfactant properties can then be combined with this concentration model and fitted to experimental data. This modular concept makes it possible to determine the cmc and the transition width in a systematic and unambiguous way. We revise its use in the literature in different contexts: the determination of the cmc of surfactants and their mixtures from different properties (electrical conductivity, NMR chemical shift, self-diffusion, surface tension, UV-Vis absorption, fluorescence intensity and fluorescence correlation). We also revise the dependence of the width of the transition region on composition, detailed studies of the properties of fluorescent probes and the aggregation of non-surfactant systems, namely amyloid peptidesThis research was funded by Xunta de Galicia, grant number ED431B 2019/18S

Professors’ perceptions of distance education in virtual environments: The case of the Education Faculty of University of Al-Yarmouk (Jordan)

The goal of this study is to determine the perceptions that the teaching staff of the Faculty of Education at University of Al-Yarmouk (Jordan) have of the implementation of distance learning in virtual environments, more specifically, the professors’ opinion of the potential and limitations of this educational strategy. To fulfil this goal, we developed a survey study. The main findings indicate that, overall, distance education in virtual environments has earned a good opinion among the professors who participated in the study, although the potential benefits of distance education are the most highly valued dimension. The professors rank the dimensions of goals and difficulties in implementing this educational strategy second, and planning the third and lowest dimension. Further, some identifying variables (e.g., department, gender) show statistically significant differences relative to the dimensions of the scale used

Critical aggregation concentration for the formation of early Amyloid-β (1–42) oligomers

The oligomers formed during the early steps of amyloid aggregation are thought to be responsible for the neurotoxic damage associated with Alzheimer’s disease. It is therefore of great interest to characterize this early aggregation process and the aggregates formed, especially for the most significant peptide in amyloid fibrils, Amyloid-β(1–42) (Aβ42). For this purpose, we directly monitored the changes in size and concentration of initially monomeric Aβ42 samples, using Fluorescence Correlation Spectroscopy. We found that Aβ42 undergoes aggregation only when the amount of amyloid monomers exceeds the critical aggregation concentration (cac) of about 90 nM. This spontaneous, cooperative process resembles surfactants self-assembly and yields stable micelle-like oligomers whose size (≈50 monomers, R h ≈ 7–11 nm) and elongated shape are independent of incubation time and peptide concentration. These findings reveal essential features of in vitro amyloid aggregation, which may illuminate the complex in vivo processWe thank the Ministerio de Ciencia e Innovación, the Ministerio de Economía y Competitividad, and the Xunta de Galicia for their financial support (CTQ2010-21369, CTQ2014-59020-R, GPC2013-052, R2014/051, ED431B 2016/024, ED431D R2016/007). S.F. thanks the Xunta de Galicia for her research scholarshipS

Evaluating the Influence of Geochemistry on the Interfacial Interactions Between Kerogen and Water and Its Consequences on Fluid Mobility

Energy Institut

Cinética formal

Titulación: Grao en Enxeñaría de Procesos Químicos Industriais -- Materia: Cinética QuímicaA materia Cinética Química do Grao en Enxeñaría de Procesos Químicos Industriais impártese no segundo cuadrimestre do segundo curso da titulación, polo que os alumnos xa dispón de coñecementos básicos de Química, Física e Matemáticas que son de gran utilidade para cursar esta materia. Esta materia aborda os sistemas en cambio debido a reaccións químicas, polo que é complementaria da materia Termodinámica Aplicada impartida no primeiro cuadrimestre do mesmo curso, que estuda o comportamento fisicoquímico dos sistemas en equilibrio. A materia encádrase no módulo 4 do plan de estudos da titulación, denominado Materias específicas de Enxeñaría de Procesos Químicos Industriais, e relaciónase con varias materias obrigatorias do módulo 3 (Tecnoloxía específica - Química Industrial) e en especial con Enxeñaría da Reacción Química, na que se aplican os conceptos de Cinética Química ás reaccións a nivel industrial. Esta unidade didáctica é de gran importancia na materia xa que nela sentan as bases da Cinética Química. Nesta unidade estúdanse os conceptos básicos relacionados coa velocidade das reaccións químicas, analízanse as reaccións máis sinxelas e revísanse os diferentes métodos experimentais utilizados no estudo cinético dunha reacción química. Esta unidade didáctica desenvolverase en 8 sesións presenciais de 50 minutos cada unha. Delas, 6 sesións dedicaranse a clases teóricoprácticas nas que se discuten os contidos e resólvense exercicios e problemas relacionados, e as 2 sesións restantes utilizaranse para a realización da actividade complementaria proposta. O alumno deberá dedicar unhas 18 horas adicionais de traballo persoal, fundamentalmente para a realización de exercicios e problemas e a aplicación nalgúns deles dos métodos de análise dados na actividade complementaria.Universidade de Santiago de Compostela. Servizo de Normalización Lingüístic

Photophysical study of Thioflavin T as fluorescence marker of amyloid fibrils

This is the accepted manuscript of the following article: Freire, S., de Araujo, M., Al-Soufi, W., & Novo, M. (2014). Photophysical study of Thioflavin T as fluorescence marker of amyloid fibrils. Dyes And Pigments, 110, 97-105. doi: 10.1016/j.dyepig.2014.05.004. © 2014 Elsevier B.V. This manuscript version is made available under the CC-BY-NC-ND 4.0 license (http://creativecommons.org/licenses/by-nc-nd/4.0/)Thioflavin T is a highly sensitive fluorescent marker of amyloid fibrils that has been widely used for in vitro biomedical assays. However, neither its complex photophysical behavior nor its binding mode to amyloid fibrils are still well understood. We present a detailed analysis of the photophysical properties of Thioflavin T in various media, including solvents and solvent mixtures of different viscosities as well as fibrillar and globular proteins. We propose a model that explains the strong wavelength dependency of the Thioflavin T fluorescence and the large fluorescence enhancement in certain environments. We determine the binding affinities and the fluorescence properties of Thioflavin T bound to amyloid-β (1–42) fibrils and to bovine serum albumin and discuss the sensitivity and the specificity of this probe to amyloid aggregates. These results allow us to assess the suitability of Thioflavin T for quantitative determinations in biomedical studiesS.F. and M. H. A. thank the Xunta de Galicia and the Ministerio de Educación, Cultura y Deporte (Program "Ciencia sin Fronteras") for scholarship. M.N. and W.A. thank the Ministerio de Ciencia e Innovación and the Xunta de Galicia for their financial support (CTQ2010-21369, CN2012/314, GPC2013/052)S

Activated carbon from grape seeds upon chemical activation with phosphoric acid: Application to the adsorption of diuron from water

The preparation of activated carbon from grape seeds was studied by chemical activation with phosphoric acid. Grape seeds were pretreated with sulfuric acid to improve wettability and impregnated at different grape seed to phosphoric acid ratios (1:1-1:4). The impregnated grape seeds were carbonized in a static horizontal furnace at temperatures between 350 and 550°C. Microporous activated carbons with some contribution of mesoporosity were obtained. The best results in terms of surface area (1139m2/g) and mesopore volume (0.24cm3/g) development were observed for a grape seeds to phosphoric acid ratio of 1:3 and a carbonization temperature of 500°C. The activated carbon prepared shows granular morphology and an egg shell structure that favors application in liquid phase. The activated carbon was tested in the adsorption of diuron from aqueous phase. The adsorption rate was measured within the temperature range of 15-45°C. First and second order rate equations and intraparticle diffusion model were checked to fit the kinetic dataWe greatly appreciate financial support from the Spanish MCYT (CTQ2009-09983 and CSD2006-44) and CAM (REMTAVARES S-2009/AMB-1588). M. Al Bahri thanks to the Spanish MICINN a research grant (CTQ2006-13512

Towards Ratiometric Sensing of Amyloid Fibrils In Vitro

This is the peer-reviewed version of the following article: Chemistry - A European Journal 2015, 21, 3425–3434, DOI: 10.1002/chem.201406110. The final form has been published at https://onlinelibrary.wiley.com/doi/abs/10.1002/chem.201406110. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived VersionsThe aggregation of amyloid‐β peptide and its accumulation in the human brain has an important role in the etiology of Alzheimer’s disease. Thioflavin T has been widely used as a fluorescent marker for these amyloid aggregates. Nevertheless, its complex photophysical behavior, with strong wavelength dependencies of all its fluorescence properties, requires searching for new fluorescent probes. The use of 2‐(2′‐hydroxyphenyl)imidazo[4,5‐b]pyridine (HPIP), which shows two emission bands and a rich excited‐state behavior due to the existence of excited‐state intramolecular processes of proton transfer and charge transfer, is proposed. These properties result in a high sensitivity of HPIP fluorescence to its microenvironment and cause a large differential fluorescence enhancement of the two bands upon binding to aggregates of the amyloid‐β peptide. Based on this behavior, a very sensitive ratiometric method is established for the detection and quantification of amyloid fibrils, which can be combined with the monitoring of fluorescence anisotropy. The binding selectivity of HPIP is discussed on the basis of the apparent binding equilibrium constants of this probe to amyloid‐β (1–42) fibrils and to the nonfibrillar protein bovine serum albumin. Finally, an exhaustive comparison between HPIP and thioflavin T is presented to discuss the sensitivity and specificity of these probes to amyloid aggregates and the significant advantages of the HPIP dye for quantitative determinationsXunta de Galicia European Regional Development Fund Ministerio de Ciencia e Innovación Xunta de Galicia. Grant Numbers: CTQ2010‐21369, CTQ2010‐17835, GPC2013/052, R2014/051 RS MacDonald Charitable TrustS