Simulating Microstructural Evolution and Electrical Transport in Ceramic Gas Sensors

An integrated computational approach to microstructural evolution and electrical transport in ceramic gas sensors has been proposed. First, the particle-flow model and the continuum-phase-field method are used to describe the microstructural development during the sintering of a prototype two-dimensional film. Then, the conductivity of the sintering samples is calculated concurrently as the microstructure evolves, using both resistor lattice models and effective medium theory for electrical transport in porous aggregates of lightly sintered particles. This approach, when combined with the modeling of resistivity at the grain–grain contacts as a function of neck geometry, ambient gas concentration and temperature, could facilitate the development and optimization of novel microstructures for advanced ceramic gas sensors.     

Determination of a representative area element (RAE) based on nonparametric statistics in bread

The concept of representative area element (RAE) was applied to quantify the air cell present in pre-sliced bread. Ten slices from bread were selected and each divided into nine subareas where 60 air cells were measured. To determine the RAE, one to nine sampling areas were considered and five positions in the image were randomly selected and compared by nonparametric statistic and the fluctuation of mean air cell area method. The RAE was attained when the air cell area size distribution curves for each sampling area did not present significant differences. Hence, the RAE size was 67% of the image using the nonparametric method (equivalent to six subareas of the nine subareas that form the image), whereas the RAE could not be estimated using the fluctuation of mean air cell area method. Therefore, nonparametric statistics are a useful tool to determine the RAE in structures with size distributions that do not fit a normal distribution.     

Statistical profiles of highly-rated learning objects

The continuously growth of learning resources available in on-line repositories has raised the concern for the development of automated methods for quality assessment. The current existence of on-line evaluations in such repositories has opened the possibility of searching for statistical profiles of highly-rated resources that can be used as priori indicators of quality. In this paper, we analyzed 35 metrics in learning objects refereed inside the MERLOT repository and elaborated profiles for these resources regarding the different categories of disciplines and material types available. We found that some of the intrinsic metrics presented significant differences between highly rated and poorly-rated resources and that those differences are dependent on the category of discipline to which the resource belongs and on the type of the resource. Moreover, we found that different profiles should be identified according to the type of rating (peer-review or user) under evaluation. At last, we developed an initial model using linear discriminant analysis to evaluate the strength of relevant metrics when performing an automated quality classification task. The initial results of this work are promising and will be used as the foundations for the further development of an automated tool for contextualized quality assessment of learning objects inside repositories.     

Studies on physico-chemical and antibacterial properties of grafted pullulans solutions

The physico-chemical properties of three grafted pullulans (P) having linked poly(3-acrylamidopropyl)trimethylammonium chloride (pAPTAC) as side chains (P-g-pAPTAC1, P-g-pAPTAC2 and P-g-pAPTAC3 with 22.53, 29.05, and 34.51 (wt.%) of pAPTAC content in polymer, respectively) and possessing polyelectrolyte character were determined by light scattering analysis. All grafted pullulan aqueous solutions were tested in the presence of 0.5 M NaCl, KCl, NaNO₃ or KNO₃. The biggest associations were recorded in 0.5 M NaCl aqueous solutions for P-g-pAPTAC1, P-g-pAPTAC2 and P-g-pAPTAC3 according to the maximum values for R_g extracted from MALLS (multiangle laser light scattering) measurements. Also, the dominant conformation in salted solution of these polyelectrolytes was random coil as Debye plot analysis revealed. Antibacterial activity was tested by Kirby–Bauer diffusion method and all grafted pullulans dissolved in aqueous solutions of 0.5 M NaCl have developed inhibition zone against Staphylococcus aureus (ATCC 25923).     

Adsorption and surface chemistry in tribology

Adsorption on sliding surfaces and the chemical changes occurring within a few nanometers of the surface are key to the performance of lubricants and lubricant additives in the boundary lubrication regime. By means of the methods of modern surface science, these phenomena are beginning to be elucidated on a molecular level. This knowledge will be essential, both for the development of higher-performance lubricants, capable of high-temperature operation, as well as for the design of environmentally benign alternatives to the lubricant systems in current use.     

Toward multimodal notation for mathematics: Why and how

Notation is a tool of thought, recording and communicating concepts and activities related to a domain of knowledge. In the history of mathematical notation, written notation is usually considered. However, to be an effective thinking tool, notation must be properly perceived. Blind and partially sighted people run into difficulty in making, exploring and understanding mathematical concepts conceived for being represented in multi-dimensional space. In this paper, we capitalize on the multifaceted nature of digital symbols to define multimodal digital notation for graph structures that allows blind and partially sighted people to represent graph structures, reason about them and communicate their reasoning with sighted people as well as each other. As support tool for notation proposed we have designed a multimodal interactive system, in which haptic signals play a crucial role. An evolutionary prototype of the system has been developed and evaluated according to the star life cycle model.     

In situ monitoring of pH level with fiber optic evanescent field spectroscopy

Fiber optic evanescent field spectroscopy for in situ monitoring of pH levels is presented. Cladding of plastic clad silica fiber is replaced with polymethyl methacrylate doped with pH sensitive chromoionophores. The chromoionophores include methyl red, thymol blue, and thymolphtalein for pH in acidic, neutral and basic environments, respectively. The evanescent wave is used to selectively excite the indicator molecules within the fiber cladding for sampling aqueous media surrounding the fiber.