Development and characterization of polyphthalaldehyde for transient applications

Metastable polymers that depolymerize in response to environmental stimuli to change shape, form, or function have garnered increased research interest in recent years. Demonstrated applications include signal amplification, temporary electronics, and drug delivery. These transient applications take advantage of the large transformation in properties that accompany the depolymerization of high molecular weight polymers into their monomeric components. Depolymerization of metastable polymers can be tailored by incorporating stimuli responsive agents that destabilize the host polymer in reaction to a variety of environmental stimuli. This thesis reports on a detailed investigation of the metastable polymer cyclic polyphthalaldehyde (cPPA). cPPA can be triggered to depolymerize into its monomeric component by exposure to heat or acid. Its degradation in response to these stimuli was characterized along with its aging-dependent mechanical properties. Significant effort was invested in on processing (at scale) of cPPA in both solvent/tape casting as well as thermoforming via hot press molding. A photoacid generator (PAG) was incorporated into cPPA films to generate acid within the film in response to exposure to UV light. Acid cleaved the polymer backbone of cPPA and resulted in solid state depolymerization into the monomer oPA. The depolymerization kinetics in response to UV light were characterized by dynamic mechanical analysis and FTIR. These polymer films were then used as substrates for the fabrication of UV triggered transient electronics that were destroyed by exposure to UV light. Transience rates were tuned by modifying the PAG concentration and the irradiance of the UV source. A thermoacid generator (TAG) was also incorporated into cPPA films to generate acid in response to thermal heating. The TAG poly(vinyl tert-butyl carbonate sulfone) (PVtBCS) forms acid at moderate temperatures (ca. 85 °C) in the presence of water and also depolymerizes into purely volatile products. Upon heating to 85 °C, the PVtBCS/cPPA films generated acid and began to depolymerize and evaporate due to volatility of the monomeric byproducts. Thermally-triggered films evaporate to leave < 2 wt% residual mass and depolymerize rapidly with tailorable depolymerization kinetics. The depolymerization kinetics can be accelerated by increasing the triggering temperature or increasing the concentration of PVtBCS in the PVtBCS/cPPA film. It is demonstrated that the total time for depolymerization is much less than the time required for complete evaporation. Solvent-based approaches were developed for the processing of cPPA. Uniform cPPA films were fabricated with both solvent casting and tape casting methods. It was discovered that a considerable amount of residual solvent remained in the polymer films after processing. The mechanical properties of the cPPA films and their dependence on several processing parameters were assessed. As expected, the parameters that resulted in a reduction of the residual solvent concentration led to an increase in the Tg of the cPPA. The volatility of the solvent played a large role in the plasticization of the films and an inverse relation between Tg and boiling point of the solvent was demonstrated. The elastic modulus, ultimate tensile strength, and Tg all increased as the residual solvent concentration decreased. The thermally-triggered depolymerization of neat cPPA was investigated and tailored in order to enable thermal processing routes towards the thermoforming and molding of cPPA. Stabilization of cPPA at elevated temperature was accomplished by removal of the latent Lewis acid catalyst BF3 and by addition of radical inhibitors and a Lewis base. Addition of a plasticizer to the stabilized cPPA significantly depressed the thermal transitions of the stabilized cPPA below the onset temperature of depolymerization, opening a thermal processing route for cPPA. A monolithic solid cPPA polymer was fabricated via hot press molding at 100 °C without initiating thermal depolymerization of cPPA

Social representation an public policies in tourism: The cases of Integrally Planed Centers in Cancún, Litibu and Ixtapa Zihuatanejo, México

El presente trabajo tiene como objetivo analizar la representación social respecto a la instauración de las políticas públicas, particularmente en materia de turismo, referente a los Centros Integralmente Planificados (CIP´s): Cancún, Quintana Roo, Litibú, Nayarit e Ixtapa-Zihuatanejo, Guerrero. Para tal efecto, se desarrollan tres apartados: a) El modelo teórico de la representación social concerniente a la implantación de las políticas públicas; b) Las políticas del Estado Mexicano orientadas al desarrollo del turismo; c) Los resultados del trabajo de campo sobre la representación social de las poblaciones locales respecto a los efectos de la política turística en los CIP’s.SEP-PRODE

A Multiscale Model for Solute Diffusion in Hydrogels.

The number of biomedical applications of hydrogels is increasing rapidly on account of their unique physical, structural, and mechanical properties. The utility of hydrogels as drug delivery systems or tissue engineering scaffolds critically depends on the control of diffusion of solutes through the hydrogel matrix. Predicting or even modeling this diffusion is challenging due to the complex structure of hydrogels. Currently, the diffusivity of solutes in hydrogels is typically modeled by one of three main theories proceeding from distinct diffusion mechanisms: (i) hydrodynamic, (ii) free volume, and (iii) obstruction theory. Yet, a comprehensive predictive model is lacking. Thus, time and capital-intensive trial-and-error procedures are used to test the viability of hydrogel applications. In this work, we have developed a model for the diffusivity of solutes in hydrogels combining the three main theoretical frameworks, which we call the multiscale diffusion model (MSDM). We verified the MSDM by analyzing the diffusivity of dextran of different sizes in a series of poly(ethylene glycol) (PEG) hydrogels with distinct mesh sizes. We measured the subnanoscopic free volume by positron annihilation lifetime spectroscopy (PALS) to characterize the physical hierarchy of these materials. In addition, we performed a meta-analysis of literature data from previous studies on the diffusion of solutes in hydrogels. The model presented outperforms traditional models in predicting solute diffusivity in hydrogels and provides a practical approach to predicting the transport properties of solutes such as drugs through hydrogels used in many biomedical applications

Association between serum uric acid levels and cardiovascular risk among university workers from the State of Mexico: a nested case–control study

Background: Recent evidence suggests that serum uric acid (SUA) can be an inexpensive and easy-to-obtain indicator of cardiovascular risk (CR). This is especially important in developing countries with high prevalence of cardiovascular disease. We examined the association between SUA levels and 10-year global CR among university workers from the State of Mexico, Mexico. Methods: A case–control study nested within a cohort was conducted between 2004 and 2006. Anthropometric measures, lifestyle variables, family background and CR factors were assessed. The analysis estimated odds ratios using conditional logistic regression. Results: The study included 319 cases with CR and 638 controls. Subjects in the upper tertile of SUA had 48.0% higher odds of having an elevated CR than those in the lower tertile (OR = 1.48, 95% CI: 1.04 - 2.10) in the crude analysis, but the association was non-significant when adjusting for other covariates. Among physically inactive individuals, being in the third tertile of SUA doubled the odds of high CR, compared with those who perform physical activity three or more hours per week being in the first tertile of SUA (OR = 2.35, 95% CI: 1.24 - 4.45). Conclusion: Serum concentration of uric acid is associated with 10-year global CR among individuals with high levels of physical inactivity

Design of a Microstrip Bowtie Antenna for Indoor Radio-Communications

In this paper, a microstrip bowtie patch antenna (MBPA) for wireless indoor communications is carried out. Here, a microstrip transmission-line feed network was designed in order to match the MBPA. The proposed antenna uses a ground plane with the aim of narrowing down the back lobes in comparison with bowtie sheet antennas, which radiation pattern is omni-directional. The far-field pattern of the antenna was simulated using a finite-element numerical algorithm and obtained by interpolation employing near-field equipment. The experimental results are described in detail intending to agree well with the simulated predictions. The antenna was designed, measured and built and its far field performance was evaluated with a 2.11 GHz resonant frequency. The azimuth and elevation antenna patterns, antenna gain and, the matching frequency were the main parameters obtained to analyze the antenna behaviour. The antenna has a gain approximately equal to 8.77 dBi and its beam-widths are higher than 100° in E plane

Validación de la Escala Breve de Optimismo Interactivo-G en México antes de la COVID-19

The primary objectives of this study were determining the construct, convergent, and discriminant validity of the Brief Interactive Optimism Scale-G (BIOS-G) in participants from six states of Mexico and estimating its internal consistency. In this study 3 289 Mexicans participated (2 028 men and 1 243 women). The average age was = 30.43 years and SD = 10.52. Confirmatory factor analysis (CFA) and multiple regression analysis (MRA) were applied. There were appropriate fit indexes (e. g., CFI = .99; RMSEA = .07.). Convergent validity showed ANR (3 289)=.52(p=&lt;.01;d=medium), with the Satisfaction with Life Scale (SWLS) and the estimation of discriminant validity was r (3 289) r = -.19 with the Brief Scale for Assessing Anger Proneness (APS-G) (p = &lt; .01; d = almost small), Alpha = .70 (3 289); p = &lt; .01; omega = .76. The conclusion is that there is partial national evidence supporting the use of BIOS-G, because Mexico lacks a measure of this kind, being useful, at least, for research purposes.Los objetivos primarios del presente estudio fueron determinar la validez de constructo, convergente y discriminante de la Escala Breve de Optimismo Interactivo-G (EBOI-G), en participantes de seis estados de México y calcular su consistencia interna. Participaron 3289 mexicanos, 2028 hombres y 1243 mujeres (18 casos no contestaron cuál era su género). Su edad promedio = 30.43 años, de = 10.52. Se usó el análisis factorial confirmatorio y análisis de regresión múltiple, y se encontraron buenos indicadores promedio de bondad de ajuste (e. g., CFI = .99; RMSEA = .07.). Se evaluó la validez convergente, r (3 289) = .52 (p = &lt; .01; d = mediano), con la Escala de Satisfacción con la Vida. Se estimó la validez discriminante, r (3 289) r = -.19, con la Escala Breve de Disposición a la IRA (p = &lt; .01; d = casi pequeño). El alfa = .70 (3 289); p = &lt; .01; el omega = .76. Se concluye que hay evidencia parcial nacional que apoya el uso de la EBOI-G, debido a la carencia de una medida de este tipo en México, útil cuando menos para propósitos de investigación.Os objetivos primários do estudo foram determinar a validade convergente e discriminante do construto da Escala Breve de Otimismo Interativo-G (EBOI-G), em participantes de seis estados do México e calcular sua consistência interna. Participaram 3 289 mexicanos, sendo 2 028 homens e 1 243 mulheres. A média de idade foi = 30.43 anos, DP = 10.52. Foram utilizadas análises fatoriais confirmatórias e análises de regressão múltipla. Bons indicadores médios de qualidade de ajuste foram encontrados (por exemplo, CFI = .99; RMSEA = .07.) A validade convergente foi avaliada, r (3 289) = .52 (p = &lt;.01; d = mediana), com a Escala de satisfação com a vida. A validade discriminante, r (3 289) = -.19 foi estimada com a Escala Breve de Disposição à Raiva (p = &lt;.01; d = quase pequeno). O alfa = 0,70 (3 289); p = &lt;0,01; o ômega = 0,76. Conclui-se que há evidências nacionais parciais que apoiam o uso da EBOI-G, devido à falta de uma medida desse tipo no México, sendo útil pelo menos para fins de pesquisa

Enfrentando los riesgos socionaturales

El objetivo del libro es comprender la magnitud de los Riesgos Socionaturales en México y Latinoamérica, para comprender el peligro que existe por algún tipo de desastre, ya sea inundaciones, sismos, remoción en masa, entre otros, además conocer qué medidas preventivas, correctivas y de contingencias existen para estar atentos ante alguna señal que la naturaleza esté enviando y así evitar alguna catástrofe. El libro se enfoca en los aspectos básicos de análisis de los peligros, escenarios de riesgo, vulnerabilidad y resiliencia, importantes para la gestión prospectiva o preventiva

First Human Isolate of Hantavirus (Andes virus) in the Americas

We isolated Andes virus (formal name: Andes virus [ANDV], a species in the genus Hantavirus), from serum of an asymptomatic 10-year-old Chilean boy who died 6 days later of hantavirus pulmonary syndrome (HPS). The serum was obtained 12 days after his grandmother died from HPS and 2 days before he became febrile. No hantavirus immunoglobulin (Ig) G or IgM antibodies were detected in the serum sample. After three blind passages, ANDV antigens were detected in Vero E6 cells by immunofluorescence assay and enzyme-linked immunosorbent assay, and ANDV RNA was detected by reverse transcription-polymerase chain reaction. A fragment of the virus genome showed 96.2% nucleotide identity with that of prototype ANDV. To our knowledge, this is the first isolation of any agent of hemorrhagic fever with renal syndrome from a human and the first such isolation of hantavirus before symptoms of that syndrome or HPS began

Virtual research and learning communities in Latin America : The CEVALE2VE case

New strategies for the adaptation of higher scientific education to the requirements of the network society are briefly discussed, in particular the pivotal role played by virtual research and learning communities in the Latin American region. The Centro Virtual de Altos Estudios de Altas Energias (CEVALE2VE) is singled out in reference to the virtual graduate course on particle physics that was given at several Venezuelan and Colombian national universities and research institutions during the semesters September 2014 - February 2015 and March 2016 - July 2016. Different course implementation aspects are reviewed to encourage and facilitate similar regional initiatives in the near future.Peer reviewe

Sustitución del grano de maíz por bagazo de limón deshidratado en dietas de recría de vaquillonas = Substitution of corn grain for dehydrated lemon bagasse in rearing heifer´ s diets

El objetivo de este trabajo fue evaluar la sustitución del grano de maíz (GM) por niveles crecientes de bagazo de limón deshidratado (BLD) en dietas de recría de vaquillonas. Se utilizaron 40 vaquillonas Braford (158 ± 3,5 kg PV inicial) asignadas aleatoriamente en 20 corrales, siendo cada corral la unidad experimental. Se generaron cuatro tratamientos a partir de la inclusión de proporciones crecientes de BLD en la dieta (0, 15, 30 y 45 % MS) en reemplazo del GM. La duración del ensayo fue de 90 d. Se evaluó el peso vivo final (PVf), el aumento medio diario (AMD), el consumo de ración (CMS), la conversión alimenticia (EC), el espesor de grasa dorsal (EGD) y el área de ojo de bife (AOB). Se recolectaron muestras individuales de cada ingrediente y muestras compuestas de las raciones ofrecidas para la determinación de la composición química. El diseño experimental fue completamente aleatorizado con 5 repeticiones por tratamiento. Los resultados fueron analizados utilizando el procedimiento GLM de SAS, siendo declaradas diferencias con P < 0,05. La sustitución parcial o total del GM por el BLD no generó diferencias significativas sobre el PVf (P = 0,61), CMS (P = 0,59), AMD (P = 0,35), EC (P = 0,29), AOB (P = 0,19) y EGD (P = 0,17). Se concluye que el bagazo de limón es un sub-producto que puede sustituir en forma parcial o total al grano de maíz en dietas de recría sin afectar el desempeño animal.The objective of this study was to evaluate the substitution of corn grain (CG) for increasing levels of dehydrated lemon bagasse (DLB) in rearing heifer ́s diets. Forty Braford heifers (158 ± 3.5 kg LW) were randomly assigned in 20 pens, considering each pen as an experimental unit. Four treatments were generated from the inclusion of increasing proportions of DLB in the diet (0, 15, 30, and 45% DM) in replacement of the corn grain. The experiment lasted 90 d. Final live weight (FLW), average daily gain (ADG), dry matter intake (DMI), feed conversion (feed:gain), backfat thickness (BFT), and rib eye area (REA) were evaluated. Individual samples of each ingredient and composite samples of the offered rations were collected for the determination of the chemical composition. The experimental design was completely randomized with 5 repetitions per treatment. The results were analyzed using the GLM procedure of SAS, being declared differences with P < 0.05. The partial or total substitution of the GM for the DLB did not generate significant differences on the FLW (P = 0.61), DMI (P = 0.59), ADG (P = 0.35), feed conversion (P = 0.29), REA (P = 0.19), and BFT (P = 0.17). It is concluded that DLB is a co-product that can partially or totally replace the corn grain in rearing diets without affecting animal performance.EEA Santiago del EsteroFil: López, Agustín. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Santiago del Estero; Argentina.Fil: López, Agustín. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; Argentina.Fil: Nasca, Jose Andres. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Investigación Animal del Chaco Semiárido; ArgentinaFil: Hernandez, Olegario. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Santiago del Estero; ArgentinaFil: Fissolo, Hector Miguel. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Santiago del Estero; ArgentinaFil: Zimerman, María. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Investigación Animal del Chaco Semiárido; ArgentinaFil: Bottegal, Diego Nicolas. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Investigación Animal del Chaco Semiárido; ArgentinaFil: Molina Arias, Alvaro Marcelo. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Investigación Animal del Chaco Semiárido; ArgentinaFil: Royo, Victoria. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Investigación Animal del Chaco Semiárido; ArgentinaFil: Franck, C. Asesor privado; ArgentinaFil: Arroquy, Jose Ignacio. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Cesareo Naredo; Argentina.Fil: Arroquy, Jose Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Arroquy, Jose Ignacio. Universidad Nacional del Sur. Departamento de Agronomía; Argentina