A characterization of triangulations of closed surfaces

In this paper we prove that a finite triangulation of a connected closed surface is completely determined by its intersection matrix. The \emph{intersection matrix} of a finite triangulation, $K$, is defined as $M_{K}=(dim(s_{i}\cap s_{j}))_{0\leq i,0\leq j}^{n-1}$, where $K_{2}=\{s_{0}, \ldots s_{n-1}\}$ is a labelling of the triangles of $K$.Comment: Submitted to EUROCOMB 201

Evaluating cerium (IV) oxide nanoparticles membrane behaviour and related toxicity

Cerium (IV) oxide nanoparticles (CeO2 NPs or nano-ceria) are one of the most popular NPs used in both industry and medicine. Nowadays, CeO2 NPs could be considered as one of the NPs with better prospects for future applications in medicine. CeO2 NPs have the ability to change between oxidation states Ce(IV) and Ce(III) creating oxygen vacancies in their structure. This ability, in theory, could regulate oxidative stress (OS). However, there are many contradictory reports regarding the beneficial or adverse effects CeO2 NPs produce when internalised in the body. In addition, the mechanisms through which CeO2 NPs interact once internalised in the body are not yet totally understood. This thesis analyses the interaction between CeO2 NPs and phospholipids (DOPC, DOPG, DOPE, DOPA and DOPS) using a biosensor able to mimic the cellular membrane. The working electrode of the electrochemical sensing device (ESD) consists of a mercury coated platinum electrode (Hg/Pt electrode) where phospholipids are deposited. CeO2 NPs with different size and shapes (spheres, cubes, needles and dots) are synthesised using wet-chemical and hydrothermal methods. Also, coated CeO2 NPs were synthesised using PVP, PEG, dextran and the CeO2 NPs were treated with PBS. The NPs were characterised using TEM, SAED, EDX, XRD, DLS and Z-Potential. Results show the chemical behavior of the CeO2NPs is related to a large extent to the characteristics of the NPs surface, the characteristics of their dispersion media and the size of the NPs. CeO2 NPs (spheres, cubes, needles and dots) did not show an interaction with the phospholipid membrane (DOPC) when the system was under a continuous flow of phosphate saline buffer (PBS, pH 7.4) and citric-citrate buffer (CCB, pH 4.0, 5.0, 6.0). Nevertheless, an interaction was observed when the system was under a continuous flow of CCB (pH 3.0) and GLY (3.0). It was concluded that Ce3+ on the NPs surface can bind to the phosphate group of the phospholipid polar heads when the NPs are in GLY 3.0. Results also showed that citrate on the CeO2 NPs surface hampers the interaction with the phospholipid monolayer at pHs above 3.0. Additionally, at acidic pH (pH 3.0), the CeO2 NPs (spheres and cubes) were able to cross the phospholipid monolayer and directly interact with the Hg/Pt electrode showing a semiconductor effect. Needles, which were bigger in size, did not produce a semiconductor effect under the same conditions. The semiconductor effect decreases as size increases. The interaction of the coated CeO2 NPs with DOPC was found to be dependent on the coating agent. In this way, the interaction between DOPC and the NPs was produced by the coating agent, not the NPs. Finally, CeO2 showed to be inert when interacting with DOPA, DOPG and DOPE under a continuous flow of PBS. The only exception was the dots, which produced a significant interaction with DOPA under the same conditions

Spatial pricing empirical evaluation of ride-sourcing trips using the graph-fussed lasso for total variation denoising

This study explores the spatial pricing discrimination of ride-sourcing trips using empirical data. We use information from more than 1.1 million rides in Austin, Texas, provided by a non-profit transportation network company from a period where the main companies were out of the city. We base the analysis on operational variables such as the waiting or idle time between trips, reaching time, and trip distance. Also, we estimate three different productivity measures to evaluate the impact of the trip destination on the driver continuation payoff. We propose the application of a total variation denoising method that enhances the spatial data interpretation. The selected methodology, known as the graph-fussed lasso (GFL), uses an l₁-norm penalty term that presents a variety of benefits to the denoising process. Specifically, this approach provides local adaptivity; it can adapt to inhomogeneity in the level of smoothness across the graph. Solving the GFL smoothing problem involves convex-optimization methods, we make use of a fast and flexible algorithm that presents scalability and high computational efficiency. The principal contributions of this research effort include a temporal and spatial evaluation of different ride-sourcing productivity measures in the Austin area, an analysis of ride-sourcing trip pricing and its effect on driver equity, and a description of the principal ride-sourcing travel patterns in the city of Austin. The main results suggest that drivers with rides ending in the central area present favorable spatial differences in productivity when including the revenue of two consecutive trips. However, the time effect was more contrasting. Weekend rides tend to provide better driver productivity measures.Statistic

Predicting friction with improved texture characterization

Current methodologies to measure road friction present several disadvantages that make them impractical for field data collection over large highway networks. Thus, it is important to study different ways to estimate surface friction characteristics based on other properties that are easier to measure. The main objective of this study was to analyze surface texture characteristics and to observe their influence on friction. A Line Laser Scanner (LLS) was implemented to make an improved characterization of the road texture which includes macro- and micro-texture description using different texture parameters. Field measurements of friction and texture were collected around Texas using different tests methods. The friction characterization tests included the British Pendulum test (BPT), the Dynamic Friction test (DFT), and the Micro GripTester. Thirty-six different pavement sections were evaluated, including different surface types such as hot-mix asphalt (HMA), surface treatment, and concrete sidewalk. Among the principal conclusions, it was found that there is not a unique relationship between texture and friction. The relationship between texture and friction is strong but it is different for each type of surface, thus, cross-sectional analysis cannot be utilized to quantify the relationship. Additionally, the prediction of friction measures obtained using the BPT and the DFT significantly improved when including information of both macro- and micro-texture into the prediction model. Therefore, a measure of micro-texture should be included into friction models based on texture. Finally, among the study of different texture parameters, the mean profile depth (MPD) was the most significant parameter for macro- and for micro-texture to explain the distinct friction measures.Civil, Architectural, and Environmental Engineerin