Mechanical and multifunctional properties of polymer composites based on nano-structures

Mención Internacional en el título de doctorThe continuous development of industries, such as aerospace, automobile or energy, requires a new generation of polymer composites with novel functionalities, i.e. desired values of thermal and electrical conductivities, while maintaining their mechanical properties to be used in structural applications. One example of this new generation of composites could be hybrid fibre-reinforced polymers, consisting in fibre-reinforced polymers in which the matrix is appropriately modified with fillers. As a first step in the above mentioned approach, in this thesis the modification of polymers with different carbon-based fillers is analysed. Graphite nanoplatelets and carbon nanotubes were used to prepare polypropylene composites. Both fillers provided modest improvements on mechanical properties, while the electrical conductivity of the CNT composites was comparable to similar materials previously reported. The third filler was a novel micron-scaled carbon material which exhibited potential to perform as reinforcing agent in polymeric matrices. It was found that the filler significantly enhanced the thermal stability of the composites, while having modest effect on their thermal conductivity and mechanical behaviour. In order to produce polymer composites with specific combination of properties, hybrid carbon-based fillers, using spherical micro- and nano-particles as substrates, were obtained by the chemical vapour deposition technique (CVD). The first developed hybrid filler consisted in alumina nanoparticles and carbon nanotubes and it was used as filler for epoxy matrix composites. The obtained composites showed enhanced thermal and electrical conductivity compared with the neat matrix, although having similar mechanical behaviour. Finally, hollow glass microspheres with carbon nanofibres grown on its surface were obtained and then dispersed within a urethane acrylate resin. The main characteristic of the resulting composites is their low density and thermal conductivity while having higher electrical conductivity, compared to the neat resinEl continuo desarrollo de industrias como la aeroespacial, del automóvil o de la energía, requiere una nueva generación de materiales compuestos poliméricos con nuevas características, como niveles deseados de conductividades térmicas y eléctricas, y que al mismo tiempo mantengan unos niveles de propiedades mecánicas adecuados para ser usados en aplicaciones estructurales. Un ejemplo de materiales compuestos poliméricos mejorados podrían ser los materiales compuestos híbridos de matriz polimérica reforzados con fibras, en los cuales la matriz polimérica está modificada con los refuerzos apropiados. Como primera etapa en el desarrollo de los materiales anteriormente mencionados, en ésta tesis se han analizado varios polímeros modificados con diferentes refuerzos basados en carbono. Se han empleado nanoplaquetas de grafito y nanotubos de carbono para la preparación de materiales compuestos de matriz polipropileno. Ambos refuerzos proporcionaron ligeros aumentos de las propiedades mecánicas, mientras que la conductividad eléctrica de los materiales con nanotubos de carbono es comparable a la de materiales similares reportados en la literatura disponible. El tercer material es un novedoso refuerzo micrométrico basado en carbono, que ha sido empleado para el procesado de materiales compuestos de polipropileno. Éste refuerzo mejoró significativamente la estabilidad térmica del polipropileno al mismo tiempo que produjo mejoras más modestas en conductividad térmica y propiedades mecánicas. Con el objetivo de obtener materiales compuestos con las combinaciones deseadas de propiedades, se han obtenido materiales híbridos en estructuras de carbono por medio de un proceso de deposición química en fase vapor. Para ello se han empleado partículas cerámicas micro y nanométricas. En primer lugar se ha desarrollado un material híbrido compuesto por nanopartículas de alúmina y nanotubos de carbono, usado como refuerzo para una resina epoxi. Los materiales compuestos obtenidos presentaron mayores niveles de conductividad térmica y eléctrica mayores comparados con la matriz sin modificar, sin embargo su comportamiento mecánico era similar al de la resina. En segundo lugar se han obtenido microesferas de vidrio huecas con nanofibras de carbono sintetizadas en su superficie. Éste material se ha usado como refuerzo de materiales compuestos con una resina uretano acrilato. Las principales características de los materiales desarrollados son su baja densidad y conductividad térmica y alta conductividad eléctrica, comparada con la resina pura.Chapter 3: This work was supported by the European Commission under the 7th Framework Program, NFRP project (PICIG12-GA-2012-33924). R.G.V. gratefully acknowledges the Spanish Ministry of Science and Innovation for financial funding through the Ramon y Cajal Fellowship. J.P.F-B is grateful for support from the “Marie Curie” Amarout Programme. -- Chapter 4: This work was supported by the European Commission under the 7th Framework Program, NFRP project (PICIG12-GA-2012- 33924), ROBOHEALTH-A project (DPI2013-47944-C4-1-R) funded by Spanish Ministry of Economy and Competitiveness and from the RoboCity2030-II-CM project (S2009/DPI-1559), funded by Programas de Actividades I+D en la Comunidad de Madrid and cofunded by Structural Funds of the EU. R.G.V. gratefully acknowledges the Spanish Ministry of Science and Innovation for funding through the Ramon y Cajal Fellowship. L.C.H-R acknowledges the support from the Spanish Ministry of Education through the FPU programme (FPU14/06843). The authors would also thank to the Ministerio de Economía y Competitividad for the Torres Quevedo Grant of Pere Castell (PTQ12-05223). -- Chapter 5: This work was supported by the European Commission under the 7th Framework Program, NFRP project (PICIG12-GA-2012-33924). R. G. V. gratefully acknowledges the Spanish Ministry of Science and Innovation for financial funding through the Ramon y Cajal Fellowship. L. C. H-R acknowledges the support from the Spanish Ministry of Education through the FPU programme (FPU14/06843).-- Chapter 6: This work was supported by the European Commission under the 7th Framework Program, NFRP project (PICIG12-GA-2012-33924). R. G. V. gratefully acknowledges the Spanish Ministry of Science and Innovation for financial funding through the Ramon y Cajal Fellowship. L. C. H-R acknowledges the support from the Spanish Ministry of Education through the FPU programme (FPU14/06843).-- Chapter 7: This work was supported by the European Commission under the 7th Framework Program, NFRP project (PICIG12-GA-2012-33924), ROBOHEALTH-A project (DPI2013-47944-C4-1-R) funded by Spanish Ministry of Economy and Competitiveness and from the RoboCity2030-II-CM project (S2009/DPI-1559), funded by “Programas de Actividades I+D en la Comunidad de Madrid” and co-funded by Structural Funds of the EU. R. G. V. gratefully acknowledges the Spanish Ministry of Science and Innovation for financial funding through the Ramon y Cajal Fellowship. L. C. H-R acknowledges the support from the Spanish Ministry of Education through the FPU programme (FPU14/06843).Programa Oficial de Doctorado en Ciencia e Ingeniería de MaterialesPresidente: Miguel Ángel López Manchado.- Secretario: Silvia González Prolongo.- Vocal: Cristina Vallés Calliz

A Comprehensive Instrument for Identifying Critical Information Infrastructure Services

Kriitiliste Informatsiooni Infrastruktuuride (KII) teenuste kindlaks määramine on üks valituste ja organisatsioonide peamisi prioriteete. KII on ühtlasi kaaluka küberturvalisuse poliitika kriitiline osa. Nii avalikus kui erasektoris Kriitilise Infrastruktuuri (KI) haavatavus suureneb, sest kasvab omavahel ühilduvate hädavajalike teenuste arv, samaaegselt tõuseb ka tõenäosus vahelesegamisteks. Hädavajalike teenuste lubamatute vahelesegamiste mõju võib välja viia arenguteni, kus aset leiab hävitav kaskaadeffekt, mille tagajärjeks on riikliku infrastruktuurisüsteemi kokkuvarisemine. Antud lõputöö eesmärgiks on tutvustada ainulaadset kõikehõlmavat instrumenti, mis toetab eskaleeritud KII teenuste kindlaksmääramist, ja põhineb kolmel analüütilisel komponendil. Nendeks on: peamiste sidusrühmade kindlaks määramine kui täpne terminoloogia loomaks terminitest ühist arusaama; kohaldatava maatriksina töötav kalkuleerimisprotsess kriitiliste reastuste otstarbeks; ja, illustratiivne raamistik nimega 360-kraadi-tagasiside, mis kinnistab terviklikku lähenemist. Terminoloogiline edasiarendus tuleneb vahendi loomisest, mis võtab arvesse esialgseid leide, see tagab KIIde vallas suurema selguse ja täpsuse. Unikaalseid tunnusjooni omavad KIId peaksid olema hinnatud iseseisvalt. Seda vaatamata KIIde ühistele joontele KIde teiste tahkudega. Vahendi kohaldatavus on näitlikustatud Kolumbia juhtumikirjelduses, kus on illustreerivalt toodud seos kahe potensiaalse hädavajaliku teenuse vahel. Juhtumikirjedluses on ühtlasi kaardistatud nende tõenäoline paiknemine riikliku kaitse prioriteetide seas. Antud lõputöö kombineerib kvalitatiivseid ja kvantiatiivseid meetodeid, sisaldab võrdlusanalüüsi teoreetilisi sisendite kohta. Lõputöö tugineb peamiselt dokumentide analüüsil, ametlikest kanalitest pärineval sekundaarselt statistilisel infol, poolstruktureeritud intervjuudel ja juhtumikirjeldusel, mis annab tööle praktilise kaalutluse. Käesolev magistritöö on kirjutatud inglise keeles, koosneb 56 leheküljest, 22 näidetest ja 26 tabelitest.The identification of Critical Information Infrastructure (CII) services has become a top priority for governments and organizations, and a crucial component of a sound cyber security policy. As the interconnectivity of essential services spreads, the probability of disruptions increases and with it the vulnerability of all Critical Infrastructure (CI) sectors public and private. The impact of an undue interruption of essential services may develop in a devastating cascading effect and the collapse of a country’s infrastructures system. The purpose of this work is to introduce an original comprehensive instrument that supports the escalated identification of CII services on the basis of three analytical components: the identification of main stakeholders, as an accurate terminology for establishing a common understanding of the terms; the calculating process for criticality ranking that works as an adaptable matrix; and, an illustrative framework called the 360- DEGREE-FEEDBACK that applies the complete perspective. Terminological development preceded the formulation of the instrument considering preliminary findings on that the field of CII warrants more clarity and precision, and that the CIIs, despite their commonalities with other dimensions of CIs, possess unique characteristics that should be assessed independently. The applicability of the instrument is illustrated in a case study of Colombia, which is used to exemplify the relationship between two potential essential services and map the likely position of them in the table of national protection priorities. This study combines qualitative and quantitative methods, benchmarking theoretical contributions, and relying mainly on documentary analysis, secondary statistical data from official sources, semi-structure interviews and a case study of practical implications. This thesis is written in English and is 56 pages long, including 22 figures and 26 tables

Enhancing Human Schwann Cells Reparative Behavior using Heparin/Collagen Layer-by-layer Coatings

When a peripheral nerve injury (PNI) occurs, the gold standard for tissue regeneration is the use of autografts. However, due to the secondary effects produced by multiple surgeries involved in the removal and implantation of autografts for very small lesions, it is possible to replace them with the use of Nerve Guide Conduits (NGCs). However, NGCs are limited to short lesions (less than 1 cm). This limitation is caused by the absence of compounds in the extracellular matrix (ECM) that autografts can provide. Since much of the regenerative process takes place on the NGC surface, our work aims to modify its surface using heparin and collagen coatings, two natural polymers present in the ECM. Heparin/collagen bilayers (HEP/COL) will increase biocompatibility, cell adhesion and migration, and allow the incorporation of neurotrophic factors such as Nerve Growth Factor (NGF). This research evaluates the effects on human Schwann cells (hSCs) when cultured on a commercial collagen NGC under four conditions: without coatings and with six heparin/collagen bilayers (HEP/COL)6 with and without NGF supplemented to the culture medium (10 ng/ml). We have exhaustively characterized (HEP/COL)6 coatings. The chemical structures of the polymers, the morphology, and the surface charge of the coatings could be determined. Real-time analysis of hSCs behavior showed three main phases: adhesion, proliferation, and adaptation. The adhesion phase was increased in the conditions with (HEP/COL)6, and the viability studies showed an increase of up to 250% compared to cells grown on polystyrene without coatings. The cell morphology has never been altered by (HEP/COL)6, as well as the morphology of the coated NGC. Cell migration was favored, and (HEP/COL)6 also increased the expression of some proteins such as BDNF, which promotes the duration of the myelination process, or TNF alpha, which is a mediator of inflammatory and immune functions. Concerning the surface modification of a commercial NGC, these studies showed an increase of more than 200% in cell viability when compared to uncoated NGCs. We also determined the presence of heparin and evidenced the cell adhesion on (HEP/COL)6 coated NGCs. In conclusion, (HEP/COL)6 seems to be a promising strategy to improve the performance of NGCs

Sizing and Eddy currents in magnetic core nanoparticles: An optical extinction approach

Optical extinction is a handy and ubiquitous technique that allows us to study colloidal nanoparticles in their native state. The typical analysis of the extinction spectrum can be extended in order to obtain structural information of the sample such as the size distribution of the cores and the thickness of the coating layers. In this work the extinction spectra of Fe3O4, Fe3O4@Au, and Fe3O4@SiO2@Au single and multilayer nanoparticles are obtained by solving full Mie theory with a frequency dependent susceptibility derived from the Gilbert equation and considering the effect of Eddy currents. The results are compared with non-magnetic Mie theory, magnetic dipolar approximation and magnetic Mie theory without Eddy currents. The particle size-wavelength ranges of validity of these different approaches are explored and novel results are obtained for Eddy current effects in optical extinction. These results are used to obtain particle size and shell thickness information from the experimental extinction spectra of Fe3O4 and Fe3O4@Au nanoparticles in good agreement with TEM results, and to predict the plasmon peak parameters for Fe3O4@SiO2@Au three layer nanoparticles.Fil: Mendoza Herrera, Luis Joaquin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; ArgentinaFil: Bruvera, Ignacio Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; ArgentinaFil: Scaffardi, Lucia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; ArgentinaFil: Schinca, Daniel Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; Argentin

Cooling Average Potential of Evaporative Cooling System in Dry Warm Climate

AbstractThe high summer temperatures, high solar radiation and common inadequate thermal design of buildings obliges the occupants to recur to the use cooling equipment such as evaporative air-conditioning to achieve acceptable levels of habitability. Evaporative cooling systems require considerable electric energy and a significant constant clean water supply during operation. Therefore, this paper presents the results of a field study aims to quantify in this kind of weather, the potential cooling means having the following strategies: indirect evaporative cooling and shading devices; indirect evaporative cooling, shading devices and thermal mass; indirect evaporative cooling, solar protection, thermal mass and nocturnal radiative cooling; indirect evaporative cooling, thermal insulation and nocturnal radiative cooling; and finally indirect evaporative cooling, thermal insulation, thermal mass and nocturnal radiative cooling. The method consisted of measuring the reduction in air temperature is achieved with each of these cooling strategies, applied in three research modules of same construction features, orientation and dimensions during the summer 2012.Then quantified the cooling average potential by the method proposed by Dr. Eduardo Gonzalez (1989). Finally registration was the water consumption with each of these strategies and estimated required consumption by direct evaporative cooling to achieve the same cooling potential. The results obtained indicate that the IEC/TI/NRC had cooling potential of 822.89 Wh/m2day, followed IEC/SP with 764.19 Wh/m2day and finally IEC/SP+TM 568.60 Wh/m2day

José Eustasio Rivera, poeta de promisión

En Santa Rosa de Viterbo empezó el largo proceso de formación que hace un jesuíta : letras humanas, ciencias. . . Estudió filosofía en la Universidad Javeriana y obtuvo la licenciatura de filosofía, letras y pedagogía. Cumplió tres años de magisterio en los colegios de Medellín y Bucaramanga, San Ignacio y San Pedro Claver. Hizo su teología en la Universidad Javeriana de Bogotá y fue ordenado sacerdote en 1959

El efecto de la distancia anafórica y de la causalidad implícita en el procesamiento de pronombres en niños entre 5 y 7 años.

100 p.Existen diversas investigaciones que buscan dilucidar lo que sucede con el procesamiento de pronombres. Existe bastante evidencia en adultos, pero escasa en niños. De acuerdo con la literatura, el procesamiento de pronombres puede variar por multiples factores, entre ellos la distancia anafórica y la causalidad implícita en el verbo. El presente estudio tiene como propósito conocer el efecto de la distancia anafórica y de la causalidad implícita en el procesamiento de pronombres en niños con desarrollo típico del lenguaje de 5, 6 y 7 años de edad. También se busca indagar acerca del desarrollo de estas habilidades en los niños en los distintos rangos de edad. Los resultados demuestran que los niños de 7 años procesan de mejor manera los anaforos pronominales que los niños de 5 años. Lo anterior indicaría que existe una progresión a medida que pasa el tiempo, puesto que a mayor edad es mejor el procesamiento de anaforos pronominales. Palabras claves: procesamiento de pronombres, distancia anafórica, causalidad implícita

Efecto de la relacion semantica en la recuperacion de la informacion episodica desde la memoria en niños con trastornos específicos del lenguaje

93 p.os niños con trastorno específico del lenguaje (TEL) presentan dificultades en aspectos de la memoria, como lo es en la memoria de trabajo fonológica. Uno de los aspectos de la memoria poco estudiados en niños con TEL es la memoria episódica. Por ello el propósito de este trabajo es estudiar el efecto de la relación semántica en la recuperación de la información episódica desde la memoria en niños con TEL. Se comparó el desempeño intergrupal de un grupo de niños con TEL expresivo y un grupo de niños control sin TEL, e intragrupal en el grupo estudio (con TEL). Los resultados demuestran que la recuperación de la información episódica desde la memoria en niños con TEL se ve afectada por el grado y tipo de relación semántica, no así cuando procesan estímulos temáticos donde su rendimiento es similar al de los niños control. Esto significaría que los niños con TEL procesan información contextual, pero en menor cantidad en relación a los niños con un desarrollo típico del lenguaje. Se discuten las implicancias de los resultados

Implications of the agreements between China and Panama

Studying the implications of the bilateral agreements between the Republic of Panama and the People’s Republic of China of 2017 allows us to understand the economic and political effects of Chinese diplomacy on international cooperation, economic development, and soft power under the principles of trust and mutual benefit. The objective is to theorise the possible risks of the various aspects of these agreements; expand or modify their terms, ideally, if desirable; promote all sectors’ participation; and collect scientific evidence to make the agreements easier for decision-makers to evaluate. Maintaining complex, interdependent relationships with different spheres of power requires prioritising national interests and adapting them to the new global reality of the COVID-19 pandemic, which requires adjusting agreements on grounds other than the Belt and Road’s specific objectives

The 'two Chinas' and Panama: an historical review of Panamanian relations with the People’s Republic of China and Taiwan, 1903–2017

This paper offers a historical overview of Panama’s ties with the “two Chinas”, focusing initially on Asian migration to the Isthmus of Panama before the territory became part of New Granada (Colombia). This migration was the result of Chinese labourers being recruited to work for the Panama railway construction company from 1850-1855 and, a few decades later, for construction of the French Canal and the Panama Canal. This will be followed by an examination of the Republic of China (ROC or Taiwan) and the People’s Republic of China (PRC) respective policies towards Panama. In addition, this paper analyses the new social, political, and economic scenarios resulting from Panama’s decision to establish diplomatic relations with the People’s Republic of China in June 2017. Panama’s engagement with China, particularly its links with China’s signature Belt and Road Initiative presents opportunities and challenges for the Central American country as it balances these with its national priorities