Diseño, construcción y puesta en marcha de intercambiador de masa de película húmeda en el laboratorio de operaciones unitarias “Dr. Pedro Solé de la escuela de Ingeniería Química de la Universidad de San Carlos de Guatemala

El presente trabajo tuvo como objetivo primordial el diseño, construcción y puesta en marcha de un intercambiador de masa de película húmeda dentro de las instalaciones del Laboratorio de Operaciones Unitarias “Dr. Pedro Solé Castellanos”, Facultad de Ingeniería, USAC. La altura efectiva de transferencia por diseño fue de 2.44 m, en donde las fases L y G entran en contacto en un tubo de vidrio de 2 pulg de diámetro. El desempeño fue evaluado bajo un flujo másico constante promedio de 7.494E-4 kg/s, y en un rango L/G= 6.8-1194.3, a diferentes flujos de la fase líquida. Gracias a la turbulencia en las fases, los coeficientes mostraron un incremento para el sistema de absorción oxígeno-agua. Se necesitaría sólo un 16.86 % del flujo de inundación del gas (0.037 kg/s) para alcanzar la concentración de equilibrio XO2=4.03E-4, bajo el flujo mínimo por diseño de la fase líquida, aunque esto difiere con la condición de la mejoría de transferencia con el aumento de L. Para el flujo máximo de la fase líquida por diseño, se necesitaría de 811.87 % al flujo másico de inundación, por lo que no podría alcanzarse el equilibrio. El costo total de construcción fue de Q37,404.98

SUSTAINABLE CONSUMPTION IN TOURISM: AN APPROACH TO ITS STATE OF KNOWLEDGE

Artículo de revisiónLas investigaciones sobre prácticas ambientales han recibido una atención creciente en el área de turismo. Sin embargo, hace falta una revisión bibliográfica que explore las prácticas de consumo sustentable en el sector. Con ese fin, a partir del uso del software ATLAS.ti 9, se realizó un análisis temático de 128 artículos cuyo objetivo principal es examinar los propósitos del consumo sustentable –buenas prácticas; hábitos del consumidor; políticas públicas, y regulaciones ambientales–, sus ámbitos de aplicación –por tipo de empresa– y su relación con la innovación (por ejemplo, con el uso de ecotecnologías). En los resultados, el análisis indica que las buenas prácticas tienen una asociación positiva con la innovación (0.72), lo que demuestra que la relación está bien establecid

T-cell derived acetylcholine aids host defenses during enteric bacterial infection with Citrobacter rodentium.

The regulation of mucosal immune function is critical to host protection from enteric pathogens but is incompletely understood. The nervous system and the neurotransmitter acetylcholine play an integral part in host defense against enteric bacterial pathogens. Here we report that acetylcholine producing-T-cells, as a non-neuronal source of ACh, were recruited to the colon during infection with the mouse pathogen Citrobacter rodentium. These ChAT+ T-cells did not exclusively belong to one Th subset and were able to produce IFNγ, IL-17A and IL-22. To interrogate the possible protective effect of acetylcholine released from these cells during enteric infection, T-cells were rendered deficient in their ability to produce acetylcholine through a conditional gene knockout approach. Significantly increased C. rodentium burden was observed in the colon from conditional KO (cKO) compared to WT mice at 10 days post-infection. This increased bacterial burden in cKO mice was associated with increased expression of the cytokines IL-1β, IL-6, and TNFα, but without significant changes in T-cell and ILC associated IL-17A, IL-22, and IFNγ, or epithelial expression of antimicrobial peptides, compared to WT mice. Despite the increased expression of pro-inflammatory cytokines during C. rodentium infection, inducible nitric oxide synthase (Nos2) expression was significantly reduced in intestinal epithelial cells of ChAT T-cell cKO mice 10 days post-infection. Additionally, a cholinergic agonist enhanced IFNγ-induced Nos2 expression in intestinal epithelial cell in vitro. These findings demonstrated that acetylcholine, produced by specialized T-cells that are recruited during C. rodentium infection, are a key mediator in host-microbe interactions and mucosal defenses

Confiance, autorité et métriques numériques : Datafication des relations publiques, disruption de la mesure et naissance d'une nouvelle expertise professionnelle

La quantification sans précédent des mondes sociaux a été au cœur de nombreuses recherches. Comprendre comment les métriques numériques façonnent les interactions humaines est une tâche nécessaire que plusieurs filières académiques ont entrepris d'initier. Il a été montré comment les avis en ligne et les scores sur les réseaux sociaux changent les comportements des individus. Par ailleurs, la capacité performative des classements et des indicateurs impacte les communautés de pratique qui s'adaptent pour répondre aux attentes, et les choix gouvernementaux sont influencés par la politique des grands nombres. Cette recherche contribue ainsi à ces travaux en analysant les effets de la mesure numérique dans un groupe particulier : les professionnels des relations publiques (RP). Il s'agit d'un jeune groupe professionnel de communication dont la pierre angulaire est la connaissance intime de ses publics. Leur capacité à appréhender le monde à travers les relations humaines, la réputation et les asymétries d'influence est une valeur fondamentale de leur identité professionnelle. Cependant, le défi de prouver leur valeur pèse de plus en plus sur eux. Ces experts, en particulier, ont été impactés par la promesse socio-technique selon laquelle tout peut être tracé, noté et mesuré. Les statistiques de médias sociaux, métriques d’audience en ligne et d’autres technologies de valuation ont bouleversé leurs pratiques traditionnelles et ont été présentées comme la solution pour évaluer leur efficacité et gagner en légitimité. Ainsi, au cours des 15 dernières années, leur discours est passé d’assurer l'impossibilité de quantifier leur performance à affirmer que ce qui n'est pas mesuré n'a aucune valeur. L'assimilation des métriques numériques dans le groupe professionnel des relations publiques (aussi nommé relations publics) soulève des questions importantes sur la façon dont les professionnels naviguent la déstabilisation causée par le passage à la quantification. Ancrée au croisement de la sociologie de la quantification, de la sociologie des professions et des études des sciences et des techniques, cette recherche montre comment ces professionnels de la communication ont exploité, enduré et répondu à l'escalade des métriques numériques, et comment ils ont négocié son utilisation en tant que preuve objective de valeur, tout en préservant leur influence personnelle et leur autorité. Pour ce faire, ce travail se focalise sur un sur un groupe spécifique d'experts en mesure digital de la communication, datant de 1996, qui a vu dans les métriques numériques une opportunité pour proposer des cadres de mesure, promouvoir de meilleures pratiques et aussi avertir sur les risques d'une approche quantifié. Cette thèse identifie un ensemble de règles grammaticales (Lemieux, 2009) que ces experts en évaluation appliquent pour produire ce qu’ils perçoivent comme des "meaningful metrics" (métriques sensées). Il s'agit de la règle des objectifs, de la règle de la contextualité, de la règle de la causalité et de la règle de la recherche et de la transparence. L'examen de chaque règle nous permet de démêler leurs liens avec les missions, les normes et les valeurs, et de découvrir les aspects négatifs des "meaningless metrics" (métriques insensées). Pour les praticiens, le manquement des règles est à l'origine de nombreuses pratiques néfastes pour la profession. En encourageant les connexions personnelles, en favorisant les espaces collaboratifs, en discutant de leur travail et en créant des conventions de mesure individualisées, ces experts en communication ont réussi à réduire l'écart des métriques numériquesThe unprecedented quantification of social worlds has been extensively studied. Understanding how digital metrics are shaping human interactions is a crucial task that has been undertaken by a variety of academic disciplines. It has been shown how online reviews and social media scores change the behaviour of individuals. The performative capacity of rankings and indicators impact communities of practice who adapt to meet expectations, and government choices are influenced by the politics of large numbers. This thesis contributes to the existing academic research by analysing the effects of digital measurement in a particular group: public relations professionals.This is a young professional group whose cornerstone is proximity to their publics and intimate knowledge of their audiences. Their capacity to understand the world through human relationships, reputation and influence asymmetries is a fundamental value to their professional identity. However, the conundrum of proving their worth has been increasingly weighing on them. They have been particularly impacted by the socio-technical promise that everything can be tracked and measured. Social media analytics, scoring and tracking technologies disrupted public relations’ (PR) traditional practices and were promoted as a way of assessing efficacy and gaining legitimacy. However, digital metrics also created a gap between practitioners and their publics. Nevertheless, in the past 15 years, the PR sector’s discourse has moved from insisting that it is impossible to quantify performance to affirming that what is not measured has no worth.The integration of digital performance indicators into the PR profession raises important questions about how professionals navigate the destabilisation caused by the shift towards quantification. Rooted at the crossroads where the sociology of quantification meets the science and technology studies, and the sociology of professions, this research shows how PR professionals leveraged, endured and responded to the escalation of internet metrics, and how they negotiated its use as an objective proof of value, while preserving their personal influence and authority. This work focuses on a specific group of computer-based PR measurement and evaluation experts, active since 1996, who viewed data-driven indicators as an opportunity for proposing measurement frameworks and promoting better practices but they also waved a red flag on some of the risks of a quantified approach.This thesis identifies a set of grammar rules (Lemieux, 2009) to produce what measurement experts perceive as ‘meaningful metrics’. These are the rule of purpose, the rule of contextuality, the rule of causation and the rule of research and transparency. Examining each rule helps to unravel their links to missions, norms and values; and to discover the flipside of ‘meaningless metrics’. Indeed, for PR measurement experts, infringement of the regulations is at the root of numerous harmful practices for the profession. Finally, the research shows that by encouraging personal connection, nurturing collaborative spaces, discussing their work and creating individualised measurement conventions, these evaluation and communication experts have succeeded in narrowing the gap of digital metric

Tuning and real-time evaluation of a four-loop cascaded control scheme for a Combustion Turbogenerator

Development of control systems for power plants must demonstrate satisfactory real-time performance in both, the development and the target platforms, before going into actual operation. This paper presents the tuning procedure of a four-loop cascaded control scheme for a gas-turbine driven electric generator, and the real-time performance evaluation, against a conventional three-loop control scheme, when controlling speed (omega), terminal voltage (V), active power (P) and reactive power (Q). The cascaded-scheme considers parallel-cascaded and series-cascaded configurations using P. and VQ control couples for the turbine and the generator, respectively. The proposed control scheme, based on discrete-time PID controllers, is compared to a conventional P omega-V control scheme by means of real-time simulation experiments in a PC-based development platform. Simulations are carried out at the start-up, synchronization and generation stages. Results show that the four-loop P omega-VQ parallel-series scheme has better performance than the conventional P omega-V three-loop scheme

Gillnet selectivity for the spotted rose snapper (Lutjanus guttatus) and the amarillo snapper (Lutjanus argentiventris) in Navidad Bay, Jalisco, Mexico

Gillnet selectivity for Lutjanus guttatus and L. argentiventris in Navidad Bay, Jalisco (Mexico), was estimated using monthly samples. Gillnets of 7.62- and 8.89-cm mesh size were used for the experimental design; 475 organisms of L. guttatus and 134 organisms of L. argentiventris were caught. The results show that the organisms caught with the 8.89-cm mesh were on average 4 cm larger and 100 g heavier than those caught with the 7.62-cm mesh. For L. guttatus, the optimum length (100% retention probability) was 29.1 cm for the 7.62-cm mesh and 33.9 cm for the 8.89-cm mesh; for L. argentiventris, the optimum length for the 7.62-cm mesh was 28.9 cm and for the 8.89-cm mesh, 33.7 cm. In both cases the catch mode corresponds to the calculated optimum length. The gillnet of 7.62-cm mesh caught the largest abundance in terms of number of individuals and biomass; however, the 8.89-cm mesh assures the catch of organisms that have reached first maturity length

Gillnet selectivity for the spotted rose snapper (Lutjanus guttatus) and the amarillo snapper (Lutjanus argentiventris) in Navidad Bay, Jalisco, Mexico

Gillnet selectivity for Lutjanus guttatus and L. argentiventris in Navidad Bay, Jalisco (Mexico), was estimated using monthly samples. Gillnets of 7.62- and 8.89-cm mesh size were used for the experimental design; 475 organisms of L. guttatus and 134 organisms of L. argentiventris were caught. The results show that the organisms caught with the 8.89-cm mesh were on average 4 cm larger and 100 g heavier than those caught with the 7.62-cm mesh. For L. guttatus, the optimum length (100% retention probability) was 29.1 cm for the 7.62-cm mesh and 33.9 cm for the 8.89-cm mesh; for L. argentiventris, the optimum length for the 7.62-cm mesh was 28.9 cm and for the 8.89-cm mesh, 33.7 cm. In both cases the catch mode corresponds to the calculated optimum length. The gillnet of 7.62-cm mesh caught the largest abundance in terms of number of individuals and biomass; however, the 8.89-cm mesh assures the catch of organisms that have reached first maturity length