Diseño del material de apoyo al estudio independiente en un curso semipresencial de matemática superior

El objetivo de este trabajo es mostrar algunos aspectos a considerar en el diseño de materiales didácticos basados en la utilización de las Nuevas Tecnologías de la Información y las Comunicaciones. Estos materiales soportados en formato electrónico serán utilizados para llevar a cabo la fase no presencial del curso de Matemática I y II para Ingenieros Informáticos en la modalidad semipresencial, que se iniciará en el mes de septiembre del 2002 en el Instituto Superior Politécnico “José Antonio Echeverría” de la ciudad de La Habana, Cuba, con una matrícula aproximada de mas de 600 alumnos, los cuales son maestros de computación en la enseñanza primaria.

Contenidos de material pedagógico de talleres de capacitación.

113 hojas : ilustraciones, fotografías a color.

Through Wafer 3D Vertical Micro-Coaxial Probe for High Frequency Material Characterization and Millimeter Wave Packaging Systems

This work presents the development of an in-plane vertical micro-coaxial probe using bulk micromachining technique for high frequency material characterization. The coaxial probe was fabricated in a silicon substrate by standard photolithography and a deep reactive ion etching (DRIE) technique. The through-hole structure in the form of a coaxial probe was etched and metalized with a diluted silver paste. A co-planar waveguide configuration was integrated with the design to characterize the probe. The electrical and RF characteristics of the coaxial probe were determined by simulating the probe design in Ansoft’s High Frequency Structure Simulator (HFSS). The reflection coefficient and transducer gain performance of the probe was measured up to 65 GHz using a vector network analyzer (VNA). The probe demonstrated excellent results over a wide frequency band, indicating its ability to integrate with millimeter wave packaging systems as well as characterize unknown materials at high frequencies. The probe was then placed in contact with 3 materials where their unknown permittivities were determined. To accomplish this, the coaxial probe was placed in contact with the material under test and electromagnetic waves were directed to the surface using the VNA, where its reflection coefficient was then determined over a wide frequency band from dc-to -65GHz. Next, the permittivity of each material was deduced from its measured reflection coefficients using a cross ratio invariance coding technique. The permittivity results obtained when measuring the reflection coefficient data were compared to simulated permittivity results and agreed well. These results validate the use of the micro-coaxial probe to characterize the permittivity of unknown materials at high frequencies up to 65GHz.

Patterning optically clear films: co-planar transparent and color-contrasted thin films from interdiffused electrodeposited and solution-processed metal oxides

Transparent thin films can now be site-selectively patterned and positioned on surface using mask-defined electrodeposition of one oxide and overcoating with a different solution-processed oxide, followed by thermal annealing. Annealing allows an interdiffusion process to create a new oxide that is entirely transparent. A primary electrodeposited oxide can be patterned and the secondary oxide coated over the entire substrate to form high color contrast coplanar thin film tertiary oxide. The authors also detail the phase formation and chemical state of the oxide and how the nature of the electrodeposited layer and the overlayer influence the optical clearing of the patterned oxide film.

Développement des bétons autoplaçants à faible teneur en poudre, Éco-BAP: formulation et performance

Abstract : Although concrete is a relatively green material, the astronomical volume of concrete produced worldwide annually places the concrete construction sector among the noticeable contributors to the global warming. The most polluting constituent of concrete is cement due to its production process which releases, on average, 0.83 kg CO[subscript 2] per kg of cement. Self-consolidating concrete (SCC), a type of concrete that can fill in the formwork without external vibration, is a technology that can offer a solution to the sustainability issues of concrete industry. However, all of the workability requirements of SCC originate from a higher powder content (compared to conventional concrete) which can increase both the cost of construction and the environmental impact of SCC for some applications. Ecological SCC, Eco-SCC, is a recent development combing the advantages of SCC and a significantly lower powder content. The maximum powder content of this concrete, intended for building and commercial construction, is limited to 315 kg/m[superscript 3]. Nevertheless, designing Eco-SCC can be challenging since a delicate balance between different ingredients of this concrete is required to secure a satisfactory mixture. In this Ph.D. program, the principal objective is to develop a systematic design method to produce Eco-SCC. Since the particle lattice effect (PLE) is a key parameter to design stable Eco-SCC mixtures and is not well understood, in the first phase of this research, this phenomenon is studied. The focus in this phase is on the effect of particle-size distribution (PSD) on the PLE and stability of model mixtures as well as SCC. In the second phase, the design protocol is developed, and the properties of obtained Eco-SCC mixtures in both fresh and hardened states are evaluated. Since the assessment of robustness is crucial for successful production of concrete on large-scale, in the final phase of this work, the robustness of one the best-performing mixtures of Phase II is examined. It was found that increasing the volume fraction of a stable size-class results in an increase in the stability of that class, which in turn contributes to a higher PLE of the granular skeleton and better stability of the system. It was shown that a continuous PSD in which the volume fraction of each size class is larger than the consecutive coarser class can increase the PLE. Using such PSD was shown to allow for a substantial increase in the fluidity of SCC mixture without compromising the segregation resistance. An index to predict the segregation potential of a suspension of particles in a yield stress fluid was proposed. In the second phase of the dissertation, a five-step design method for Eco-SCC was established. The design protocol started with the determination of powder and water contents followed by the optimization of sand and coarse aggregate volume fractions according to an ideal PSD model (Funk and Dinger). The powder composition was optimized in the third step to minimize the water demand while securing adequate performance in the hardened state. The superplasticizer (SP) content of the mixtures was determined in next step. The last step dealt with the assessment of the global warming potential of the formulated Eco-SCC mixtures. The optimized Eco-SCC mixtures met all the requirements of self-consolidation in the fresh state. The 28-day compressive strength of such mixtures complied with the target range of 25 to 35 MPa. In addition, the mixtures showed sufficient performance in terms of drying shrinkage, electrical resistivity, and frost durability for the intended applications. The eco-performance of the developed mixtures was satisfactory as well. It was demonstrated in the last phase that the robustness of Eco-SCC is generally good with regards to water content variations and coarse aggregate characteristics alterations. Special attention must be paid to the dosage of SP during batching.

The difference of Being in the early modern world: a relational-material approach to life in Scotland in the period of the witch trials

This thesis investigates how ways of being in different ontologies emerge from material and embodied practice. This general concern is explored through the particular case study of Scotland in the period of the witch trials (the 16th and 17th centuries C.E.). The field of early modern Scottish witchcraft studies has been active and dynamic over the past 15 years but its prioritisation of what people said over what they did leaves a clear gap for a situated and relational approach focusing upon materiality. Such an approach requires a move away from the Cartesian dichotomies of modern ontology to recognise past beliefs as real to those who experienced them, coconstitutive of embodiment and of the material worlds people inhabited. In theory, method and practice, this demands a different way of exploring past worlds to avoid flattening strange data. To this end, the study incorporates narratives and ‘disruptions’ – unique engagements with Contemporary Art which facilitate understanding by enabling the temporary suspension of disbelief. The methodology is iterative, tacking between material and written sources in order to better understand the heterogeneous assemblages of early modern (counter-) witchcraft. Previously separate areas of discourse are (re-)constituted into alternative ontic categories of newly-parallel materials. New interpretations of things, places, bodies and personhoods emerge, raising questions about early modern experiences of the world. Three thematic chapters explore different sets of collaborative agencies as they entwine into new things, co-fabricating a very different world. Moving between witch trial accounts, healing wells, infant burial grounds, animals, discipline artefacts and charms, the boundaries of all prove highly permeable. People, cloth and place bleed into one another through contact; trees and water emerge as powerful agents of magical-place-making; and people and animals meet to become single, hybrid-persons spread over two bodies. Life and death consistently emerge as protracted processes with the capacity to overlap and occur simultaneously in problematic ways. The research presented in this thesis establishes a new way of looking at the nature of Being as experienced by early modern Scots. This provides a foundation for further studies, which can draw in other materials not explored here such as communion wares and metal charms. Comparison with other early modern Western societies may also prove fruitful. Furthermore, the methodology may be suitable for application to other interdisciplinary projects incorporating historical and material evidence.

Evaluación de la exposición laboral a material particulado en empresas pertenecientes a diferentes sectores económicos en Colombia, 2014

Introducción El material particulado son partículas sólidas y líquidas emitidas al aire, las cuales pueden generar diferentes alteraciones en la salud, variando desde cuadros respiratorios alérgicos, a episodios asmáticos, dermatitis o inclusive llegar a facilitar la génesis de enfermedades de tipo neoplásico. Estos pueden tener origen natural e industrial, encontrandose en diferentes actividades económicas. Objetivo Evaluar la exposición laboral a material particulado en empresas pertenecientes a diferentes sectores económicos afiliadas a una ARL en Colombia, en el periodo comprendido entre 2011 al 2014 Metodología Es un estudio de corte transversal, analizando una base de datos de 257 empresas con 1108 mediciones de material particulado, recolectados entre 2011 – 2014. Las variables usadas fueron: región, actividad económica, área, oficio, tiempo de exposición y concentración de material particulado. Se realizó distribuciones de frecuencia, medidas de tendencia central y de dispersión. Se evaluaron las diferencias de las distribuciones de los tiempos de exposición y el porcentaje de exposición entre los grupos con y sin riesgo (los que sobrepasaban o no los límites permisibles), con la prueba asintótica no paramétrica de Mann Whitney. Resultados Las principales mediciones ambientales en las empresas fueron en la industria química con un 31%, siendo 2 de cada 3 datos pertenecientes a la región andina, las cuales tienen como principales contaminantes químicos las partículas no fraccionadas con el 70,9%. Respecto a las concentraciones ambientales de material particulado en las empresas participantes, se encontró un promedio de 1,72 mg/m3 ± 3,613, con una mediana de 0,480 mg/m3 y un coeficiente de variación de 210,05%. El 2,9% sobrepasaron los valores límites establecidos por la ACGIH (American Conference of Governmental Industrial Hygienists) y el 92,5% según los límites de la EPA (Agencia de Protección del Ambiente), presentando mayor riesgo en el personal operativo con 93,3% (p= 0,002). Conclusión El riesgo según los límites establecidos por la ACGIH para las mediciones realizadas en Colombia fue bajo, aunque al utilizar los parámetros de la EPA, el riesgo fue alto, por lo cual se requiere hacer un seguimiento específico a estas empresas y fomentar la implementación del sistema de gestión en seguridad y salud en el trabajo.

Relação entre resistência ao cisalhamento no plano e parâmetros processuais de co-cura de juntas em compósitos auto-reforçados de polietileno de matriz reprocessada

Este estudo investiga a otimização da resistência ao cisalhamento no plano de juntas de sobreposição co-curadas do compósito termoplástico unidirecional auto-reforçado de polietileno de baixa densidade reciclado reforçado por fibras de polietileno de ultra alto peso molecular através da relação desta resistência com os parâmetros processuais de prensagem a quente para a conformação da junta (pressão, temperatura, tempo e comprimento). A matriz teve sua estrutura química analisada para verificar potenciais degradações devidas à sua origem de reciclagem. Matriz e reforço foram caracterizados termicamente para definir a janela de temperatura de processamento de junta a ser estudada. A elaboração das condições de cura dos corpos de prova foi feita de acordo com a metodologia de Projeto de Experimento de Superfície de Resposta e a relação entre a resistência ao cisalhamento das juntas e os respectivos parâmetros de cura foi obtida através de equação de regressão gerada pelo método dos Mínimos Quadrados Ordinários. A caracterização mecânica em tração do material foi analisada micro e macromecanicamente. A análise química da matriz não demonstrou a presença de grupos carboxílicos que evidenciassem degradação por ramificações de cadeia e reticulação advindos da reciclagem do material. As metodologias de ensaio propostas demonstraram ser eficazes, podendo servir como base para a constituição de normas técnicas. Demonstrou-se que é possível obter juntas com resistência ótima ao cisalhamento de 6,88 MPa quando processadas a 1 bar, 115°C, 5 min e com 12 mm. A análise da fratura revelou que a ruptura por cisalhamento das juntas foi precedida por múltiplas fissuras longitudinais induzidas por sucessivos debondings, tanto dentro quanto fora da junta, devido à tensão transversal acumulada na mesma, proporcional a seu comprimento. A temperatura demonstrou ser o parâmetro de processamento mais relevante para a performance da junta, a qual é pouco afetada por variações na pressão e tempo de cura.

Correlation between structure and electrochemistry of LiMO2 cathode materials (M = Ni, Co)

Technical diversity and various knowledge is required for the understanding of undoubtedly complex system such as a Lithium-ion battery. The peculiarity is to combine different techniques that allow a complete investigation while the battery is working. Nowadays, research on Li-ion batteries (LIBs) is experiencing an exponential growth in the development of new cathode materials. Accordingly, Li-rich and Ni-rich NMCs, which have similar layered structure of LiMO2 oxides, have been recently proposed. Despite the promising performance on them, still a lot of issues have to be resolved and the materials need a more in depth characterisation for further commercial applications. In this study LiMO2 material, in particular M = Co and Ni, will be presented. We have focused on the synthesis of pure LiCoO2 and LiNiO2 at first, followed by the mixed LiNi0.5Co0.5O2. Different ways of synthesis were investigated for LCO but the sol-gel-water method showed the best performances. An accurate and systematic structural characterization followed by the appropriate electrochemical tests were done. Moreover, the in situ techniques (in-situ XRD and in situ OEMS) allowed a deep investigation in the structural change and gas evolution upon the electrochemically driven processes.

Synthesis and characterization of defective PBAs electrode material

Sodium manganese hexacyanoferrate (NaMnHCF) and its derivatives have been synthesized by simple co-precipitation method with addition of the citric and ascorbic acids respectively. The correspondent crystal structure, water content, chemical formula and a deep structural investigation of prepared samples have been performed by means of the combination of the laboratory and synchrotron techniques (PXRD, FT-IR, TGA, MP-AES and XAS). Electrochemical tests have been done using three-electrode system in sodium nitrate solution at different concentration. From cyclic voltammetry curves, Fe3+/2+ redox peak has been observed, whereas Mn3+/2+ peak was not always evident. Structural stability of the cycled samples has then been tested using 2D XRF imaging and Transmission X-ray microscopy (TXM) techniques. The intercalation of NaMnHCF after 20 cycles has been found by micro-XANES analysis of the highlighted spots which have been found in the XRF images. TXM has also confirmed the appearance of the intercalated particles after 50 cycles comparing the spectra between charged and discharged materials at three different edges (Mn, Fe and N). However, by comparison with lithium samples, it seems obvious that sodium samples are more homogeneous and intercalation is at the very beginning indicating the relative structural stability of sodium manganese hexacyanoferrate electrode material.

Crystal engineering of co-crystals and host-guest systems for environmentally friendly applications: sunscreens stabilization, pollutant sequestering and herbicide reformulation.

Solid state engineered materials have proven to be useful and suitable tools in the quest of new materials. In this thesis different crystalline compounds were synthesized to provide more sustainable products for different applications, as in cosmetics or in agrochemistry, to propose pollutants removal strategy or to obtain materials for electrocatalysis. Therefore, the research projects presented here can be divided into three main topics: (i) sustainable preparation of solid materials of widely used active ingredients aimed at the reduction of their occurrence in the natural environment. The systems studied in this section are cyclodextrins host-guest compounds, obtained via mechanochemical and slurry synthesis. The first chemicals studied are sunscreens inclusion complexes, that proved to have enhanced photostability and desired photoprotection. The same synthetic methods were applied to obtain inclusion complexes of bentazon, a herbicide often found to leach in groundwaters. The resulting products showed to have desired water solubility properties. The same herbicide was also adsorbed on amorphous calcium phosphate nanoparticles, to obtain a biocompatible formulation of this agrochemical. This herbicide could benefit by the adsorption on nanoparticles for what concerns its kinetic release in different media as well as its photostability. (ii) Sustainable synthesis of co-crystals based on polycyclic aromatic hydrocarbons, for the proposal of a sequestering method with a resulting material with enhanced properties. The co-crystallization via mechanochemical means proved that these pollutants can be sequestered via simple solvent-free synthesis and the obtained materials present better photochemical properties when compared to the starting co-formers. (iii) Crystallization from mild solvents of nanosized materials useful for the application in electrocatalysis. The study of compounds based on nickel and cobalt metal ions resulted in the obtainment of 2D and 1D coordination polymers. Moreover, solid solutions were obtained. These crystals showed layered structures and, according to preliminary results, they can be exfoliated.

Effect Of Platform Connection And Abutment Material On Stress Distribution In Single Anterior Implant-supported Restorations: A Nonlinear 3-dimensional Finite Element Analysis.

Although various abutment connections and materials have recently been introduced, insufficient data exist regarding the effect of stress distribution on their mechanical performance. The purpose of this study was to investigate the effect of different abutment materials and platform connections on stress distribution in single anterior implant-supported restorations with the finite element method. Nine experimental groups were modeled from the combination of 3 platform connections (external hexagon, internal hexagon, and Morse tapered) and 3 abutment materials (titanium, zirconia, and hybrid) as follows: external hexagon-titanium, external hexagon-zirconia, external hexagon-hybrid, internal hexagon-titanium, internal hexagon-zirconia, internal hexagon-hybrid, Morse tapered-titanium, Morse tapered-zirconia, and Morse tapered-hybrid. Finite element models consisted of a 4×13-mm implant, anatomic abutment, and lithium disilicate central incisor crown cemented over the abutment. The 49 N occlusal loading was applied in 6 steps to simulate the incisal guidance. Equivalent von Mises stress (σvM) was used for both the qualitative and quantitative evaluation of the implant and abutment in all the groups and the maximum (σmax) and minimum (σmin) principal stresses for the numerical comparison of the zirconia parts. The highest abutment σvM occurred in the Morse-tapered groups and the lowest in the external hexagon-hybrid, internal hexagon-titanium, and internal hexagon-hybrid groups. The σmax and σmin values were lower in the hybrid groups than in the zirconia groups. The stress distribution concentrated in the abutment-implant interface in all the groups, regardless of the platform connection or abutment material. The platform connection influenced the stress on abutments more than the abutment material. The stress values for implants were similar among different platform connections, but greater stress concentrations were observed in internal connections.

Improved Selective Cholesterol Adsorption By Molecularly Imprinted Poly(methacrylic Acid)/silica (pmaa-sio₂) Hybrid Material Synthesized With Different Molar Ratios.

The present paper describes the synthesis of molecularly imprinted polymer - poly(methacrylic acid)/silica and reports its performance feasibility with desired adsorption capacity and selectivity for cholesterol extraction. Two imprinted hybrid materials were synthesized at different methacrylic acid (MAA)/tetraethoxysilane (TEOS) molar ratios (6:1 and 1:5) and characterized by FT-IR, TGA, SEM and textural data. Cholesterol adsorption on hybrid materials took place preferably in apolar solvent medium, especially in chloroform. From the kinetic data, the equilibrium time was reached quickly, being 12 and 20 min for the polymers synthesized at MAA/TEOS molar ratio of 6:1 and 1:5, respectively. The pseudo-second-order model provided the best fit for cholesterol adsorption on polymers, confirming the chemical nature of the adsorption process, while the dual-site Langmuir-Freundlich equation presented the best fit to the experimental data, suggesting the existence of two kinds of adsorption sites on both polymers. The maximum adsorption capacities obtained for the polymers synthesized at MAA/TEOS molar ratios of 6:1 and 1:5 were found to be 214.8 and 166.4 mg g(-1), respectively. The results from isotherm data also indicated higher adsorption capacity for both imprinted polymers regarding to corresponding non-imprinted polymers. Nevertheless, taking into account the retention parameters and selectivity of cholesterol in the presence of structurally analogue compounds (5-α-cholestane and 7-dehydrocholesterol), it was observed that the polymer synthesized at the MAA/TEOS molar ratio of 6:1 was much more selective for cholesterol than the one prepared at the ratio of 1:5, thus suggesting that selective binding sites ascribed to the carboxyl group from MAA play a central role in the imprinting effect created on MIP.

Mesenchymal Stromal Cells From Adipose Tissue Attached To Suture Material Enhance The Closure Of Enterocutaneous Fistulas In A Rat Model.

Surgical treatment for enterocutaneous fistulas (EF) frequently fails. Cell therapy may represent a new approach to treatment. Mesenchymal stromal cells (MSCs) have high proliferative and differentiation capacity. This study aimed to investigate whether MSCs could adhere to suture filament (SF), promoting better EF healing. MSCs, 1 × 10(6), from adipose tissue (ATMSCs) were adhered to a Polyvicryl SF by adding a specific fibrin glue formulation. Adhesion was confirmed by confocal and scanning electron microscopy (SEM). A cecal fistula was created in 22 Wistar rats by incising the cecum and suturing the opening to the surgical wound subcutaneously with four separate stitches. The animals were randomly allocated to three groups: control (CG)-five animals, EF performed; injection (IG)-eight animals 1 × 10(6) ATMSCs injected around EF borders; and suture filament (SG): nine animals, sutured with 1 × 10(6) ATMSCs attached to the filaments with fibrin glue. Fistulas were photographed on the operation day and every 3 days until the 21st day and analyzed by two observers using ImageJ Software. Confocal and SEM results demonstrated ATMSCs adhered to SF (ATMSCs-SF). The average reduction size of the fistula area at 21st day was greater for the SG group (90.34%, P < 0.05) than the IG (71.80%) and CG (46.54%) groups. ATMSCs adhered to SF maintain viability and proliferative capacity. EF submitted to ATMSCs-SF procedure showed greater recovery and healing. This approach might be a new and effective tool for EF treatment.

Brazilian Natural Fiber (jute) As Raw Material For Activated Carbon Production.

Jute fiber is the second most common natural cellulose fiber worldwide, especially in recent years, due to its excellent physical, chemical and structural properties. The objective of this paper was to investigate: the thermal degradation of in natura jute fiber, and the production and characterization of the generated activated carbon. The production consisted of carbonization of the jute fiber and activation with steam. During the activation step the amorphous carbon produced in the initial carbonization step reacted with oxidizing gas, forming new pores and opening closed pores, which enhanced the adsorptive capacity of the activated carbon. N2 gas adsorption at 77K was used in order to evaluate the effect of the carbonization and activation steps. The results of the adsorption indicate the possibility of producing a porous material with a combination of microporous and mesoporous structure, depending on the parameters used in the processes, with resulting specific surface area around 470 m2.g-1. The thermal analysis indicates that above 600°C there is no significant mass loss.