Browsing by Author "Fernandez, Francisco"

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    A comparison of mixed logit and latent class models to estimate market segments for seafood faced with ocean acidification
    (2023) Campos-Requena, Nelyda; Vasquez-Lavin, Felipe; Fernandez, Francisco; Barrientos, Manuel; Gelcich, Stefan; Ponce Oliva, Roberto D.
    This study uses a choice experiment to characterize market segments (consumer preferences heterogeneity) based on three attributes of seafood (mussels) that are affected by ocean acidification: shell appearance, meat color, and nutritional composition. Using a sample of 1,257 individuals from two main cities in Chile, we estimate both the Mixed Logit model and the Latent Class model. We use the individual-specific posterior (ISP) parameters' distribution to categorize consumers' heterogeneity based on the signs and intensity (i.e., like or dislike dimension) of these ISPs. We compare the pattern of preferences and whether people are classified within the same preference pattern in both models. In general, we observed that the models identify a different number of segments with various patterns of preferences. Moreover, the models classify the same people into different groups. Since the segmentation is sensitive to the chosen model, we discuss strengths, inconsistencies, biases, and best practices regarding methodological approaches to establishing market segments in choice experiments and future ocean acidification conditions.
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    Anterior and distal tunnel orientation for anatomic reconstruction of the medial patellofemoral ligament is safer in patients with open growth plates
    (SPRINGER, 2020) Irarrazaval, Sebastian; Besa, Pablo; Fernandez, Francisco; Fernandez, Tomas; Tuca, Maria; Lira, Maria J.; Orrego, Mario
    Purpose In patients with open growth plates, the direction of tunneling that avoids distal femoral physis (DFP) damage in anatomic reconstructions of the medial patellofemoral ligament (MPFL) has been a topic of discussion. The objective of this study was to determine the ideal orientation for anatomic reconstructions of MPFL tunneling that minimized DFP damage while avoiding breaching the intercondylar notch. Methods Eighty magnetic resonance images of patients aged 10 through 17 were obtained, randomly sampled from the institutional database. A de novo software was developed to obtain 3D models of the distal femur and DFP. In each model, the anatomical insertion point of the MPFL was determined as defined by Stephen. A 20-mm-depth drilling was simulated, starting from the insertion point at every possible angle within a 90 degrees cone using 5-, 6- and 7-mm drills. Physeal damage for each pair of angles and each drill size was determined. Damage was expressed as a percentage of total physis volume. Statistical analysis was conducted using Student'sttest and one-way ANOVA. Results Maximum physeal damage (5.35% [4.47-6.24]) was obtained with the 7-mm drill when drilling 3 degrees cephalic and 15 degrees posterior from insertion without differences between sexes (n.s.). Minimal physeal damage (0.22% [0.07-0.37]) was obtained using the 5-mm drill aimed 45 degrees distal and 0 degrees anteroposterior, not affected by sex (n.s.). Considering intra-articular drilling avoidance, the safest zone was obtained when aiming 30 degrees-40 degrees distal and 5 degrees-35 degrees anterior, regardless of sex. Conclusion Ideal femoral tunnel orientation, avoiding physeal damage and breaching of the intercondylar notch, was obtained when aiming 30 degrees-40 degrees distal and 5 degrees-35 degrees anterior, regardless of sex. This area is a safe zone that allows anatomic MPFL reconstruction of patients with an open physis.
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    Electrodes based on zeolites modified with cobalt and/or molybdenum for pesticide degradation: part II-2,4,6-trichlorophenol degradation
    (2021) Castro, Jorge; Fernandez, Francisco; Olivares, Felipe; Berrios, Cristhian; Garrido-Ramirez, Elizabeth; Blanco, Elodie; Escalona, Nestor; Aspee, Alexis; Barrias, Pablo; Soledad Ureta-Zanartu, M.
    2,4,6-trichlorophenol (TCP) is a persistent pollutant introduced in water by industrial processes and pesticides. We have studied the electrooxidation of TCP on glassy carbon (GC) electrodes drop-coated with a suspension containing Mo- and/or Co-modified zeolite, graphite, and Nafion (R) perfluorinated ion-exchange resin in distilled water. Three zeolites, Linde type A (ZA), Faujasite (ZY) and MFI (ZSM-5), of different hydrophilic/hydrophobic character, were modified with molybdenum and/or cobalt by the wet impregnation method and characterized by Fourier-transform infrared spectroscopy with attenuated total reflection and temperature programmed reduction. The electrochemical study included cyclic voltammetry, electrochemical impedance spectroscopy, and electrolysis at controlled potential. High performance liquid chromatography and mass spectrometry allowed detecting the following reaction products: 2,6-dichloro-1,4-benzoquinone, 2,6-dichloro-1,4-hydroquinone, 3,5-dichloro-2-hydroxy-1,4-benzoquinone, and malic, maleic, picric, and acetic acids. A maximum degradation of about 90% was reached after 4 h of electrolysis at 0.83 V vs Ag/AgCl/KCl 3 M, using a GC/graphite-ZSM5(Mo) electrode. The electrodes modified with Mo, and especially that with ZSM5, the most hydrophobic zeolite, were active for the degradation of TCP. We conclude that the main role of the Mo species is to catalyze the hydrogen peroxide decomposition yielding reactive singlet oxygen, as evidenced by the pink color of 3,5-dichloro-2-hydroxy-1,4-benzoquinoneand confirmed by mass spectrometry.