Radiative Transference Equation Algorithm as an ANSYS® User-Defined Function for Solar Technology Applications

Heat effects in photocatalytic reactor applications are discussed and a case study is analyzed where sunlight is used to activate a chemical reaction to degrade water pollutants. Heat is produced in the light-capturing process, and heat effects need to be better understood during the device design process. Radiative transfer equation (RTE) is the guiding equation used to calculate radiation proliferation in participating media, and it is used to describe the balance of radiative energy transport in the participating media including the interactions caused by different processes such as absorption, scattering, and emission, which also are subject to additional phenomena like weakening and magnification. This equation plays an important role in the design process since it may be included in the simulation process to represent the sunlight heat effects in the different photocatalytic reactor components. In this chapter, it is explained how to build a simplified algorithm to incorporate the RTE in a numerical calculation during the design of a photocatalytic reactor using the commercial software ANSYS®. In addition, simplifications are explained that enable the program to coordinate some coefficients such as absorption and dispersion so their effects are included within the numerical calculation. A user-defined function is presented in the end of the chapter as a usable algorithm in ANSYS® program with acceptable results for photocatalytic reactors

Excited States of Six Anthocyanidin Variants with Different Solvents as Dye Sensitizers for Photocatalysis

Anthocyanidins in the gas phase and under the effects of solvents such as water, ethanol, n-hexane, and methanol have been studied using DFT and TDDFT electronic structure calculations for applications as natural dyes in photocatalysis. The results include HOMO and LUMO orbitals, HOMO-LUMO gap, chemical properties, reorganization energies, and excited states. Malvidin presented the lower HOMO-LUMO gap energy. After the inclusion of solvents, HOMO-LUMO gap energy increased in all cases, presenting malvidin with n-hexane as the narrower gap energy. Conceptual DFT results showed that cyanidin, malvidin, and pelargonidin present good charge transfer properties. Cyanidin presented a lower electron reorganization energy (λe) when water is used as the solvent. TDDFT has been used for excited states calculation and absorption data show the main peaks in a wavelength between 479.1 and 536.4 nm. The UV–Vis absorption spectra were generated and the solvent effects in each case are discussed. In consequence, pigments selected in this attempt are suitable to work in the visible part of the electromagnetic spectrum and display the main peak in the green region. These pigments are found as good options for photocatalysis applications, and the best choices for dye sensitization are cyanidin, malvidin, and petunidin after including the more common anthocyanidins in the analysis

Hydrodynamic Analysis on a Photocatalytic Reactor Using ANSYS Fluent^®

Solar technology includes a wide variety of developments in environmental applications that include photovoltaic cells and photocatalytic devices, among others. Sunlight usage as a clean energy source is highly desirable in technology applications. The main interest of this proposal is to carry on with hydrodynamic analysis in photocatalytic reactors applications where sunlight is used to activate a chemical reaction to degrade water pollutants and calculations are based in computational fluid dynamics (CFD) using ANSYS®. The different steps, geometric domain, preprocessing steps, setup, and postprocessing steps, are described to display an analysis of a numerical calculation during the design of a photocatalytic reactor using the commercial software ANSYS Fluent®. This work may help as a guide for chemical reactor design and includes a numerical solution of one case for a photocatalytic reactor during its design process. In addition, simplifications are explained which enable the designer to make an efficient process of the numerical calculation. Calculations and analysis are carried over in ANSYS Fluent® a powerful multi-physics program suite to develop photocatalytic reactors

Solvent Effects on Dye Sensitizers Derived from Anthocyanidins for Applications in Photocatalysis

Anthocyanidins under the effects of solvents water, ethanol, n-hexane, and methanol are interesting due to their suitability as natural dyes for photocatalytic applications. In this chapter, DFT and TDDFT methodologies are used to study their electronic structure. The results displayed include HOMO, LUMO, HOMO-LUMO gap, chemical properties, and reorganization energies for the ground states, and excited state data are also displayed. Malvidin in gas phase has lower gap energy. After addition of solvents, gap energy increases in all cases but malvidin with n-hexane presents narrower gap. Conceptual DFT results show that cyanidin and malvidin may have good charge transfer. Cyanidin presented lower electron reorganization energy (λe) using solvent water; however, ethanol and methanol had similar values. TDDFT is used to calculate excited states, and absorption data show wavelength main peak between 479.1 and 536.4 nm. UV-Vis absorption spectra were generated and solvent effects on each molecule is discussed. Anthocyanidins work well in the visible region with the stronger peak at the green region. These pigments are good options for photocatalysis application and cyanidin and malvidin, in this order, may be the best choices for dye sensitization applications

Memoria del II Coloquio Internacional sobre Diversidad Cultural y Estudios Regionales

Desde la Sede de Occidente y, específicamente, en el seno de la Coordinación de Investigación y con el apoyo de la Dirección de la Sede y las Coordinaciones de Docencia, Administración y Acción Social, así como de la Vicerrectoría de Investigación, se han celebrado en el 2011 y en el 2012 dos coloquios internacionales sobre diversidad cultural y estudios regionales. El propósito de ambos consistió principalmente en motivar a investigadores e investigadoras de las distintas unidades académicas de la Universidad de Costa Rica y de otras instituciones de Educación Superior, así como a representantes de Centros e Institutos de Investigación nacionales e internacionales, a presentar resultados de investigaciones que contribuyeran a un mayor conocimiento de los procesos culturales y que dieran a conocer resultados que permitieran la comprensión de las realidades de distintos sectores y regiones. En el 2011 se presentaron cuarenta y seis ponencias y se dictaron tres conferencias magistrales, y en el 2012 se expusieron cincuenta ponencias y se impartieron tres conferencias magistrales.UCR::Sedes Regionales::Sede de Occidente::Recinto San Ramón::Centro de Investigaciones sobre Diversidad Cultural y Estudios Regionales (CIDICER

Photosynthetic Pigments with Potential for a Photosynthetic Antenna: A DFT Analysis

Geometrical and electronic properties of the main photosynthetic pigments in higher plants such as chlorophylls and xanthophylls were studied to find potential candidates that were able to participate in an eventual zeolite-dye artificial antenna. CRDFT (chemical reactivity density functional theory) and TD-DFT (time-dependent DFT) methods were employed in ground-state and excited-state calculations, respectively. The evaluated electronic properties at the gas phase included (a) energies such as HOMO-LUMO band gap (H-L, ranging from 2.168 to 2.504 eV), adiabatic ionization potential (I, ranging from 5.964 to 7.207 eV), and adiabatic electronic affinity (A, ranging from 2.176 to 2.741 eV); (b) global chemical reactivity indexes such as electronegativity (χ, ranging from 4.121 to 4.974 eV), hardness (η, ranging from 1.812 to 2.233 eV), electrophilicity index (ω, ranging from 4.365 to 5.541 eV), and electroaccepting-electrodonating powers (ω+, ranging from 1.671 to 2.115 eV, and ω−, ranging from 4.375 to 5.273 eV); (c) electron-hole reorganization energies (λ, ranging from 0.225 to 0.519 eV and ranging from 0.168 to 0.425 eV, respectively) and electron-hole extraction potentials (EEP, ranging from 2.570 to 2.966 eV, and HEP, ranging from 5.538 to 7.012 eV, respectively); and (d) local chemical reactivity indexes like condensed Fukui functions (fk), condensed dual descriptor (f2r), and condensed local softness (sk). These electronic properties allowed the association between molecules and reactivity-selectivity criteria, under the context of charge transfer and electronic transitions. Also, the aforementioned electronic properties were determined for combinations made with the selected molecules (β-cryptoxanthin and zeaxanthin) and 5 solvents (n-hexane, diethyl ether, acetone, ethanol, and methanol) with upward dielectric constants (ε). From frequency calculations, IR spectra were obtained for combinations. Finally, excited-state computations were carried out to acquire UV-Vis spectra of the combinations. We conclude that the selection of dyes is controlled mainly by geometrical constraints rather than by electronic properties

Validez en el registro del pico espiratorio máximo de niños asmáticos de la Ciudad de México Validity of peak flow record in asthmatic children residing in Mexico City

OBJETIVO: Determinar la concordancia entre el pico espiratorio forzado (PEF) registrado por padres de niños asmáticos y el PEF electrónico que es el almacenado en el AirWatch (PEFe). MATERIAL Y MÉTODOS: Se obtuvo el PEF de 42 niños de 5 a 15 años de edad del Hospital Infantil de México Federico Gómez de la Ciudad de México entre octubre de 1998 y 1999. Los padres registraron el valor máximo del PEF en un diario de salud. Se calculó la correlación de Spearman entre el PEFe y el PEFr. Utilizamos un modelo logístico de efectos mixtos. RESULTADOS: La correlación del PEFe y el PEFr fue r= 0.96 (p<0.05) en niños con diagnóstico de asma moderada o severa y r= 0.40 (p< 0.05) en niños con asma leve. El tiempo de seguimiento y severidad del asma, el género y edad del niño y sus interacciones eran predictores de las diferencias entre el PEFe y el PEFr. CONCLUSIONES: Los padres de niños de 6 a 8 años con asma moderada o severa reportan mejor el PEF en el diario de salud a lo largo del seguimiento que los padres de otros grupos.<br>OBJECTIVE: To determine the concordance between maximum peak expiratory flow records (PEFr) reported by the parents of asthmatic children and the electronic values stored by the AirWatch device (PEFe). MATERIAL AND METHODS: Records of PEF measurements between October 1998 and 1999 were obtained from 42 asthmatic children 5 to 15 years of age recruited at the Hospital Infantil de Mexico Federico Gomez, in Mexico City. Parents recorded the maximum value in the health diary. Spearman correlation was calculated between PEFe and PEFr and a mixed-effects logistic model was used. RESULTS: The correlation between PEFe and PEFr was r=0.96 (p<0.05) among children with a diagnosis of moderate or severe asthma and r=0.40 (p<0.05) among children diagnosed with mild asthma. Follow-up time, asthma severity, gender and age of the child and their interactions were predictors of the differences between PEFe and PEFr. CONCLUSIONS: Parents of children with moderate or severe asthma from 6 to 8 years of age report PEF values with greater accuracy during follow-up than others

Validez en el registro del pico espiratorio máximo de niños asmáticos de la Ciudad de México

Objetivo. Determinar la concordancia entre el pico espiratorio forzado (PEF) registrado por padres de niños asmáticos y el PEF electrónico que es el almacenado en el AirWatch (PEFe). Material y métodos. Se obtuvo el PEF de 42 niños de 5 a 15 años de edad del Hospital Infantil de México Federico Gómez de la Ciudad de México entre octubre de 1998 y 1999. Los padres registraron el valor máximo del PEF en un diario de salud. Se calculó la correlación de Spearman entre el PEFe y el PEFr. Utilizamos un modelo logístico de efectos mixtos. Resultados. La correlación del PEFe y el PEFr fue r= 0.96 (p<0.05) en niños con diagnóstico de asma moderada o severa y r= 0.40 (p< 0.05) en niños con asma leve. El tiempo de seguimiento y severidad del asma, el género y edad del niño y sus interacciones eran predictores de las diferencias entre el PEFe y el PEFr. Conclusiones. Los padres de niños de 6 a 8 años con asma moderada o severa reportan mejor el PEF en el diario de salud a lo largo del seguimiento que los padres de otros grupos

Perspectives of Organic Dyes Cosensitization and Its Utilization in TiO₂ Nanoclusters for Photocatalysis Applications

Cosensitization has emerged as a method to improve performance of dye sensitized solar cells (DSSCs) and photocatalysis. In this work, it is proposed to use organic dyes as cosensitizers due to their friendliness with the environment and to the benefits of having two or more different dyes with complementary optical absorption characteristics. Several organic dyes are analyzed as cosensitizers to identify which dye combinations may be good choices to approach a panchromatic absorption spectrum emulating the solar emission spectrum. In addition to the analysis on the prospective sensitizers, it is presented results of titanium dioxide (TiO2) nanoclusters cosensitized with two anthocyanidins using density functional theory (DFT) and time-dependent DFT (TD-DFT). The nanocluster size proved to be definitive in the interactions with two molecule dyes. The selected (TiO2)4–5 nanoclusters cosensitized with two anthocyanidins produce data for a prospective analysis to suggest which dyes are good options for DSSCs and photocatalysis based on dye co-sensitization applications. At the end, one can look at this work as a perspective of which organic dyes may work well as cosensitizers and a contrast to original data from our experimentation with a couple of TiO2 nanoclusters cosensitized with two different anthocyanidins