Browsing by Author "Reyes, Javier"

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    Enhanced photoconversion efficiency of hybrid TiO2/nox-MWCNT/Si photoanode for water splitting in neutral medium
    (2021) Olivares, Fernanda; Segura del Rio, Rodrigo; Reyes, Javier; Peon, Francisco; Henriquez, Ricardo; Hevia, Samuel A.; Duran, Boris; Villalonga, Reynaldo
    Hybrid films composed by TiO2 and functionalized MWCNTs were synthesized and used as photoanodes to perform the water splitting process under neutral and free of sacrificial agents medium. The results show that introducing a sublayer of MWCNTs functionalized with -NO2 and -COOH groups leads to structural modifications on TiO2 that decrease the band gap and reduce the recombination phenomenon. Those groups anchored to nanotubes also play an important role in their dispersibility and provide an additional electron withdrawing effect to the pristine nanotubes. These conditions significantly improve the photoconversion efficiency of the hybrid system until 15-fold regarding pristine TiO2 prepared under the same conditions. (c) 2020 Elsevier B.V. All rights reserved.
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    Exotic surfaces
    (2024) Reyes, Javier; Urzua, Giancarlo
    Although exotic blow-ups of the projective plane at n points have been constructed for every n >= 2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$n \ge 2$$\end{document}, the only examples known by means of rational blowdowns satisfy n >= 5\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$n \ge 5$$\end{document}. It has been an intriguing problem whether it is possible to decrease n. In this paper, we construct the first exotic CP2#4CP2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathbb {C}}{\mathbb {P}}<^>2 \# 4 \overline{{\mathbb {C}}{\mathbb {P}}<^>2}$$\end{document} with this technique. We also construct exotic 3CP2#b-CP2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$3{\mathbb {C}}{\mathbb {P}}<^>2 \# b<^>- \overline{{\mathbb {C}}{\mathbb {P}}<^>2}$$\end{document} for b-=9,8,7\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$b<^>-=9,8,7$$\end{document}. All of them are minimal and symplectic, as they are produced from projective surfaces W with Wahl singularities and KW\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$K_W$$\end{document} big and nef. In more generality, we elaborate on the problem of finding exotic (2 chi(OW)-1)CP2#(10 chi(OW)-KW2-1)CP2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\begin{aligned} (2\chi ({\mathcal {O}}_W)-1) {\mathbb {C}}{\mathbb {P}}<^>2 \# (10\chi ({\mathcal {O}}_W)-K<^>2_W-1) \overline{{\mathbb {C}}{\mathbb {P}}<^>2} \end{aligned}$$\end{document}from these Koll & aacute;r-Shepherd-Barron-Alexeev surfaces W, obtaining explicit geometric obstructions on the corresponding configurations of rational curves.
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    Rational configurations in K3 surfaces and simply-connected pg=1 surfaces with K2=1, 2, 3, 4, 5, 6, 7, 8, 9
    (2022) Reyes, Javier; Urzua, Giancarlo
    The aim of this paper is to directly relate the problem of constructing simply-connected p(g) = 1 surfaces of general type via Q-Gorenstein smoothings with geographical problems about arrangements of rational curves in K3 surfaces. We focus on simple normal crossing arrangements, showing numerical constraints based on their log Chern numbers and their rank in the Neron-Severi group. We also show what to expect as Wahl singularities, classifying the case when K-2 = 1. We use these arrangements to prove the existence of many (20 - 2K(2))-dimensional families of simply-connected surfaces with ample canonical class, p(g) = 1, and 1 <= K-2 <= 9, through several constructions with various special properties. We work out all our surfaces from one particular arrangement in a specific K3 surface with maximal Picard number. Our surfaces with K-2 = 7 and K-2 = 9 are the first surfaces known in the literature, together with the existence of a 4-dimensional family for K-2 = 8. With this, unobstructed simply-connected p(g) = 1 surfaces have been found for every possible K-2.
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    Sport omnivorism: Social stratification of sports practice in Chile
    (2021) Reyes, Javier
    Using Chan and Goldthorpe's theoretical framework of cultural consumption, this study analyses the patterns of social stratification in sports practice in Chile. Based on the data of the National Survey of Physical Activity and Sports Habits in the Population Aged 18 and Over 2015 in Chile (n= 5511), a latent class analysis was used to identify and characterize types of sports practice in this country. After this, logistic and multinomial regressions were performed to relate the types of sports practice found and its social determinants. The results support current literature in sports participation, finding evidence in favour of both the homology hypothesis and omnivorous-univorous hypothesis. However, in the same way as previous studies, it is shown that these arguments are reconfigured in the field of sport.