Impact of the solvent composition on the structural and mechanical properties of customizable electrospun poly(vinylpyrrolidone) fiber mats.

The performance of fibrous membrane composites fabricated via electrospinning is strongly influenced by the solution's properties, process variables and ambient conditions, although a precise mechanism for controlling the properties of the resulting composite has remained elusive. In this work, we focus on the fabrication of electrospun poly(vinylpyrrolidone) (PVP) fibers, by varying both the polymer concentration and the mixture of ethanol (EtOH) and dimethylformamide (DMF) used as solvent. The impact of the solvent composition on the structural properties is assessed by a combined experimental and theoretical approach, employing scanning electron microscopy (SEM), differential scanning calorimetry (DSC), rheology, Fourier-transform infrared spectroscopy (FTIR) and stress-strain curves obtained from tensile tests to characterize the fibrous membranes produced, and density functional theory (DFT) calculations to explain the solvent's affect on PVP crystallization. We establish a morphological phase diagram, and propose a possible mechanism based on the measured fiber diameter distribution, the viscoelastic properties of the precursor solution, the correlation between the functional groups and the mechanical properties, the thermal transitions and the degree of crystallinity. We also employ DFT calculations to model the polymer coverage at equilibrium of a PVP polymer chain in the presence of EtOH/DMF solvent mixtures to corroborate the crucial role their O or -OH groups play in achieving high PVP coverages and promoting the stability of the resulting fiber. These findings will be valuable to researchers interested in predicting, modulating, and controlling both a fiber's morphology and its concomitant physico-chemical properties.

Calcium silicates synthesised from industrial residues with the ability for CO2 sequestration.

This work explored several synthesis routes to obtain calcium silicates from different calcium-rich and silica-rich industrial residues. Larnite, wollastonite and calcium silicate chloride were successfully synthesised with moderate heat treatments below standard temperatures. These procedures help to not only conserve natural resources, but also to reduce the energy requirements and CO2 emissions. In addition, these silicates have been successfully tested as carbon dioxide sequesters, to enhance the viability of CO2 mineral sequestration technologies using calcium-rich industrial by-products as sequestration agents. Two different carbon sequestration experiments were performed under ambient conditions. Static experiments revealed carbonation efficiencies close to 100% and real-time resolved experiments characterised the dynamic behaviour and ability of these samples to reduce the CO2 concentration within a mixture of gases. The CO2 concentration was reduced up to 70%, with a carbon fixation dynamic ratio of 3.2 mg CO2 per g of sequestration agent and minute. Our results confirm the suitability of the proposed synthesis routes to synthesise different calcium silicates recycling industrial residues, being therefore energetically more efficient and environmentally friendly procedures for the cement industry.

Surface properties of anatase TiO2 nanowire films grown from a fluoride-containing solution.

Controlling the surface chemistry of nucleating seeds during wet-chemical synthesis allows for the preparation of morphologically well-defined nanostructures. Synthesis conditions play a key role in the surface properties, which directly affect the functional properties of the material. Therefore, it is important to establish post-synthesis treatments to facilitate the optimization of surface properties with respect to a specific application, without losing the morphological peculiarity of the nanostructure. We studied the surface properties of highly crystalline and porous anatase TiO2 nanowire (NW) electrodes, grown by chemical-bath deposition in fluoride-containing solutions, using a combined electrochemical and spectroscopic approach. As-deposited films showed low capacity for catechol adsorption and a poor photoelectrocatalytic activity for water oxidation. Mild thermal annealing at 200 °C resulted in a significant improvement of the electrode photoelectrocatalytic activity, whereas the bulk properties of the NWs (crystal structure, band-gap energy) remained unchanged. Enhancement of the functional properties of the material is discussed on the basis of adsorption capacity and electronic properties. The temperature-induced decrease of recombination centers, along with the concomitant increase of adsorption and reaction sites upon thermal annealing are called to be responsible for such improved performance.

Spectroscopic properties of electrochemically populated electronic states in nanostructured TiO2 films: anatase versus rutile.

A thorough characterization of nanostructured materials under application-relevant conditions is a prerequisite for elucidating the interplay between their physicochemical nature and their functional properties in practical applications. Here, we use a spectroelectrochemical approach to study the population of electronic states in different types of nanostructured anatase and rutile TiO2 films in contact with an aqueous electrolyte. The spectroscopic properties of the two polymorphs were addressed under Fermi level control in the energy range between the fundamental absorption threshold and the onset of lattice absorption (3.3-0.1 eV). The results evidence the establishment of an equilibrium between localized Ti(3+) centers absorbing in the vis/NIR and shallow (e(-))(H(+)) traps absorbing in the MIR upon electron accumulation in anatase electrodes. The absence of the MIR-active (e(-))(H(+)) traps on all rutile electrodes points to a crystal structure-dependent electron population in the films.

Water-dependent micromechanical and rheological properties of silica colloidal crystals studied by nanoindentation.

Here we show the suitability of nanoindentation to study in detail the micromechanical response of silica colloidal crystals (CCs). The sensitivity to displacements smaller than the submicrometer spheres size, even resolving discrete events and superficial features, revealed particulate features with analogies to atomic crystals. Significant robustness, long-range structural deformation, and large energy dissipation were found. Easily implemented temperature/rate-dependent nanoindentation quantified the paramount role of adsorbed water endowing silica CCs with properties of wet granular materials like viscoplasticity. A novel "nongranular" CC was fabricated by substituting capillary bridges with silica necks to directly test water-independent mechanical response. Silica CCs, as specific (nanometric, ordered) wet granular assemblies with well-defined configuration, may be useful model systems for granular science and capillary cohesion at the nanoscale.

Fabrication, Physical-Chemical and Biological Characterization of Retinol-Loaded Poly(vinyl Alcohol) Electrospun Fiber Mats for Wound Healing Applications.

Nowadays, there exists a huge interest in producing innovative, high-performance, biofunctional, and cost-efficient electrospun biomaterials based on the association of biocompatible polymers with bioactive molecules. Such materials are well-known to be promising candidates for three-dimensional biomimetic systems for wound healing applications because they can mimic the native skin microenvironment; however, many open questions such as the interaction mechanism between the skin and the wound dressing material remain unclear. Recently, several biomolecules were intended for use in combination with poly(vinyl alcohol) (PVA) fiber mats to improve their biological response; nevertheless, retinol, an important biomolecule, has not been combined yet with PVA to produce tailored and biofunctional fiber mats. Based on the abovementioned concept, the present work reported the fabrication of retinol-loaded PVA electrospun fiber mats (RPFM) with a variable content of retinol (0 ≤ Ret ≤ 25 wt.%), and their physical-chemical and biological characterization. SEM results showed that fiber mats exhibited diameters distribution ranging from 150 to 225 nm and their mechanical properties were affected with the increasing of retinol concentrations. In addition, fiber mats were able to release up to 87% of the retinol depending on both the time and the initial content of retinol. The cell culture results using primary mesenchymal stem cell cultures proved the biocompatibility of RPFM as confirmed by their effects on cytotoxicity (low level) and proliferation (high rate) in a dose-dependent manner. Moreover, the wound healing assay suggested that the optimal RPFM with retinol content of 6.25 wt.% (RPFM-1) enhanced the cell migratory activity without altering its morphology. Accordingly, it is demonstrated that the fabricated RPFM with retinol content below the threshold 0 ≤ Ret ≤ 6.25 wt.% would be an appropriate system for skin regenerative application.

Fabrication of Porous Alumina Structures by SPS and Carbon Sacrificial Template for Bone Regeneration.

In this work, a procedure for fabricating porous alumina with the use of a carbon sacrificial template has been tested in order to optimize the fabrication of porous structures mimicking the porosity and mechanical properties of the human cortical bone. Two different sources of sacrificial carbon were used and compared, and different sintering and calcination routes were considered. The porosity of the alumina structures studied by Hg porosimetry revealed that the amount of porosity and the size and shape of the pores are still below the required values, although some acicular pores were clearly observed by SEM. Moreover, measured mechanical properties (Young's modulus) remained below that of the bone, suggesting the need for further consolidation treatments. In summary, these encouraging results drive the optimization of future fabrication routes.

Colloidal crystals and water: Perspectives on liquid-solid nanoscale phenomena in wet particulate media.

Solid colloidal ensembles inherently contain water adsorbed from the ambient moisture. This water, confined in the porous network formed by the building submicron spheres, greatly affects the ensemble properties. Inversely, one can benefit from such influence on collective features to explore the water behavior in such nanoconfinements. Recently, novel approaches have been developed to investigate in-depth where and how water is placed in the nanometric pores of self-assembled colloidal crystals. Here, we summarize these advances, along with new ones, that are linked to general interfacial water phenomena like adsorption, capillary forces, and flow. Water-dependent structural properties of the colloidal crystal give clues to the interplay between nanoconfined water and solid fine particles that determines the behavior of ensembles. We elaborate on how the knowledge gained on water in colloidal crystals provides new opportunities for multidisciplinary study of interfacial and nanoconfined liquids and their essential role in the physics of utmost important systems such as particulate media.

Unexpected inverse correlation between Native American ancestry and Asian American variants of HPV16 in admixed Colombian cervical cancer cases.

BACKGROUND: European (E) variants of HPV 16 are evenly distributed among world regions, meanwhile Non-European variants such as European-Asian (EAs), Asian American (AA) and African (Af) are mostly confined to Eastern Asia, The Americas and African regions respectively. Several studies have shown that genetic variation of HPV 16 is associated with the risk of cervical cancer, which also seems to be dependent on the population. This relationship between ethnicity and variants have led to the suggestion that there is co-evolution of variants with humankind. Our aim was to evaluate the relationship between the individual ancestry proportion and infection with HPV 16 variants in cervical cancer. METHODS: We examined the association between ancestry and HPV 16 variants in samples of 82 cervical cancer cases from different regions of Colombia. Individual ancestry proportions (European, African and Native American) were estimated by genotyping 106 ancestry informative markers. Variants were identified by PCR amplification of the E6 gene, followed by reverse line blot hybridization (RLB) with variants specific probes. RESULTS: Overall European (E) and Asian American (AA) variants frequency was 66.5% and 33.5% respectively. Similar distribution was observed in cases with higher proportions of European or African ancestry. A higher Native American ancestry was significantly associated with higher frequency of E variants (median ancestry>23.6%, Age and place of birth adjusted OR: 3.55, 95% CI: 1.26-10.03, p=0.01). Even further, an inverse geographic correlation between Native American ancestry and frequency of infections with AA variants was observed (ρ=-0.825, p=0.008). Regions with higher proportion of Native American ancestry had a lower frequency of AA variants of HPV 16. CONCLUSIONS: This study suggests replacement of AA variants by E variants of human papillomavirus 16 in cervical cancer cases with high Native American ancestry.

Algoritmo de control de potencia para el simulador básico a nivel de sistema LTE / Power control algorithm for an LTE system level basic simulator / Algoritmo de controle de potência para o simulador básico no nível do sistema LTE

RESUMEN Evolución de Largo Término (LTE) es la tecnología móvil celular que brinda las mayores velocidades de transmisión de datos; para garantizar los requerimientos de los usuarios y los diferentes servicios utiliza mecanismos de Gestión de Recursos Radio (RRM), tales como el control de potencia. En este artículo se presenta el modelado y la implementación de algoritmos de control de potencia en el Simulador Básico a Nivel de Sistema para LTE, desarrollado por estudiantes de la Universidad del Cauca, para analizar el efecto del control de potencia en el desempeño de una red LTE. Se empleó la metodología del Proceso Racional Unificado, definiendo los requerimientos, el diseño, la implementación, los escenarios y las pruebas, se realizó el análisis en los escenarios de LTE definidos, evaluando el impacto de los algoritmos de control de potencia en el desempeño del sistema LTE. Las pruebas del sistema evidenciaron que el control de potencia en lazo cerrado permite mantener un número mayor de usuarios conectados en la celda, brinda un mejor aprovechamiento de la potencia de transmisión. Además, se obtienen mayores probabilidades de servicio para diferentes radios de celda y número de usuarios, en comparación con el algoritmo de control de potencia en lazo abierto.

ABSTRACT Long Term Evolution (LTE) is a mobile communication technology for high-speed data rates; in order to get them, it uses radio resource management (RRM) procedures such as power control. This article shows the modeling and implementation of power control algorithms in a system level simulation, in a simulator developed by students of the University of Cauca, to analyze the effect of power control on the performance of an LTE network. We use a methodology based on a unified rational process to define the requirements, the analysis, design and implementation, and the test scenarios, to evaluate the impact of the power control algorithms on the performance of an LTE system. The results show that the closed loop power control brings service to a bigger number of users in a cell, a more efficient use of the power and increases the coverage probability for different cell sizes and number of users in comparison to the open-loop power control.

RESUMO Long Term Evolution (LTE) é a tecnologia móvel celular que fornece as maiores velocidades de transmissão de dados; Para garantir os requisitos dos usuários e dos diferentes serviços, utiliza mecanismos de gerenciamento de recursos de rádio (RRM), como controle de energia. Este artigo descreve a modelagem e implementação de algoritmos de controlo de potência na simulação básico em nível de sistema para LTE, desenvolvido por estudantes da Universidad del Cauca é apresentado para analisar o efeito de controle de potência no desempenho de uma rede LTE metodologia Rational Unified processo foi utilizado, para definir as necessidades, de criação, aplicação, e cenários de teste, a análise foi realizada sobre as fases de LTE definidos, avaliar o impacto dos algoritmos de controlo de potência de desempenho Sistema LTE. teste de sistema mostrou que o controle de potência em circuito fechado permite-lhe manter um maior número de usuários conectados na célula, proporciona melhor aproveitamento da potência de transmissão. Além disso, mais provável que servem para raios célula diferente e número de utilizadores, em comparação com o algoritmo de controlo de potência em circuito aberto é obtido.

How Important is Working with an Ordered Electrode to Improve the Charge Collection Efficiency in Nanostructured Solar Cells?

The collection efficiency of carriers in solar cells based on nanostructured electrodes is determined for different degrees or morphological one-dimensional order. The transport process is modeled by random walk numerical simulation in a mesoporous electrode that resembles the morphology of nanostructured TiO2 electrodes typically used in dye-sensitized solar cells and related systems. By applying an energy relaxation procedure in the presence of an external potential, a preferential direction is induced in the system. It is found that the partially ordered electrode can almost double the collection efficiency with respect to the disordered electrode. However, this improvement depends strongly on the probability of recombination. For too rapid or too slow recombination, working with partially ordered electrodes will not be beneficial. The computational method utilized here makes it possible to relate the charge collection efficiency with morphology. The collection efficiency is found to reach very rapidly a saturation value, meaning that, in the region of interest, a slight degree of ordering might be sufficient to induce a large improvement in collection efficiency.

Modelado y simulación de planificadores de recursos radio para una red LTE

Una de las principales características de LTE es la capacidad para realizar la asignación dinámica de recursos de radio disponibles en el sistema, haciendo uso de diferentes algoritmos de planificación. Este artículo describe el modelado de los tres algoritmos de planificación de recursos de radio básicos en enlace descendente LTE conocidos como Round Robín, Proportional Fairy Maximun Rate, su implementación en el Simulador Básico a Nivel de Sistema, y la simulación de un escenario específico para evaluar el rendimiento de cada algoritmo en capacidad (throughput) para una red LTE. Para cumplir con tal propósito se emplea una metodología lineal secuencial, empezando con una breve descripción de la tecnología LTE para contextualizar al lector seguidamente se detallan las fases de diseño e implementación y finalmente se realizan procesos de simulación y pruebas en dos escenarios LTE específicos, con el fin de evaluar el desempeño de cada uno de los planificadores de recursos radio implementados y determinar el impacto que tienen estás técnicas en la capacidad (throughput) que se puede llegar a alcanzar en una red LTE.

One of the main features of LTE is the ability to perform the dynamic allocation of radio resources available in the system using different scheduling algorithms. This paper describes the modeling of the three basic radio resource scheduling algorithms in LTE downlink known as Round Robin, Proportional Fair and Maximun Rate, its implementation in the Basic System Level Simulator and simulation on a specific scenario to evaluate the performance of each algorithm in capacity (throughput) for a LTE network. To accomplish this purpose a sequential linear method is used, beginning with a brief description of the LTE technology to contextualize the reader then the phases of design and implementation are described and finally simulation and testing processes are performed on two specific scenarios LTE, in order to evaluate the performance of each radio resource scheduling algorithms modeled and to determine the impact of these techniques in the capacity (throughput) that can reach a LTE network.

Uma das principais características do LTE é a capacidade de executar a atribuição dinâmica de recursos de rádio disponíveis no sistema, o uso de diferentes algoritmos de escalonamento. Este artigo descreve a modelagem do recurso três algoritmos de planejamento de rádio LTE básico downlink conhecido e Round Robin, Proportional Fair y Maximun Rate, a sua implementação no Simulação Básica em Nível de Sistema e simulando um cenário específico para avaliar o desempenho de cada algoritmo de capacidade (throughput) para uma rede LTE. Para cumprir este propósito uma metodologia linear sequencial utilizado, começando com uma breve descrição da tecnologia LTE para contextualizar o leitor, em seguida, as fases de projeto e implementação são detalhados e, finalmente, processos de simulação e testes são realizados em dois cenários específicos LTE, a fim de avaliar o desempenho de cada um dos planeadores de recursos rádio implementadas e determinar o impacto destas técnicas na capacidade (throughput) que podem atingir uma rede LTE.

Identification of adsorption sites in Cu-BTC by experimentation and molecular simulation.

The adsorption of several quadrupolar and nonpolar gases on the Metal Organic Framework Cu-BTC has been studied by combining experimental measurements and Monte Carlo simulations. Four main adsorption sites for this structure have been identified: site I close to the copper atoms, site I' in the bigger cavities, site II located in the small octahedral cages, and site III at the windows of the four open faces of the octahedral cage. Our simulations identify the octahedral cages (sites II and III) and the big cages (site I') as the preferred positions for adsorption, while site I, near the copper atoms, remains empty over the entire range of pressures analyzed due to its reduced accessibility. The occupation of the different sites for ethane and propane in Cu-BTC proceeds similarly as for methane, and shows small differences for O2 and N2 that can be attributed to the quadrupole moment of these molecules. Site II is filled predominantly for methane (the nonpolar molecule), whereas for N2, the occupation of II and I' can be considered almost equivalent. The molecular sitting for O2 shows an intermediate behavior between those observed for methane and for N2. The differences between simulated and experimental data at elevated temperatures for propane are tentatively attributed to a reversible change in the lattice parameters of Cu-BTC by dehydration and by temperature, blocking the accessibility to site III and reducing that to site I'. Adsorption parameters of the investigated molecules have been determined from the simulations.