The sintering and stability of catalytic nano-particles

Studies were performed on three different catalysts in order to determine their stability and sintering behavior. Pd deposited on a flat single crystal substrate made of Al2O3 was characterized to determine if the mechanism of Ostwald ripening was solely dominated by vapor phase transport of metal atoms. The atoms emitted could be determined by the rate of evaporation and an attempt was then made in order to relate the rates of emission to sintering (instability of nanoparticles). It was found that the rates of emission did not fully reflect vapor phase transport (direct evaporation). The particle-support interaction was increasing the rate of evaporation leading to the belief that adatom diffusion, caused by a weaker bound atom on the support, played a more significant role than vapor phase transport. A powder Pd/Al2O3 was also put under similar ageing conditions as the single crystal samples, but relating the two separate systems proved difficult. This was due to the containment of the metal on the support and changes of the powder support through ageing (loss in surface area). Support changes (decrease in the number of sites for particle nucleation) caused by the heat treatments seemed to also be influencing the sintering behavior. The powder samples were put through two different ageing studies, one with the presence of water vapor and the other without. The presence of water vapor enhanced the rate of sintering due to the interactions with the support and particles, possibly by changing the support morphology or making hydroxyl groups on the metal particle surface or both. A second catalyst was characterized to establish the affect support structure would have on the stability of nanoparticles. 10wt% of Pt and Re were deposited on two different carbon supports, Norit and Vulcan Carbon. Norit Carbon was imaged to be highly roughened and as a result had a large surface area (1000m2/g). The Vulcan Carbon was imaged to be more graphitic and contain two different types of structures, one similar to larger graphitic carbon particles, and the other to resemble a more roughened structure similar to that of Norit. The Pt and Re species appeared to be homogeneously dispersed on the Norit with both atomic species and nanoparticles. It was seen that the Pt and Re atoms preferred to adsorb onto the areas where the carbon structure appeared have an edge site. A third catalyst was used for in-situ TEM studies to clearly identify and record the exact sintering mechanism at the early stages of exposure to reaction conditions. Previous theory and simulation were in debate on which sintering mechanism dominates and what is the cause, our in-situ studies gave direct evidence of the sintering mechanism taking place under a gaseous and heated environment. A ~14wt%Ni on MgAl2O4, used primarily for steam reforming, was put through a series of in-situ TEM experiments under high temperatures (750°C) in the presence of hydrogen and water vapor 3.6mbar (1:1). It was found by recording images at a fast rate (every 100-200 milliseconds) the sintering mechanism could be observed and recorded. In the later stages of heating, ~30 minutes after reaching temperature, larger particles (\u3e5nm) were seen to be mobile on the surface, contrary to theory which suggests that larger particle should be immobile. Recorded images and movies taken at the early stages of heating revealed that smaller particles (\u3c3nm) were immobile on the support but could ripen away rapidly. This evidence is also contrary to previous theory that suggested smaller particles would be highly mobile and coalescence once the catalyst is exposed to reaction conditions. Further investigation into the sintering events, revealed that particle adhesion decreases as both time and particle size increase. The loss in adhesion to support in larger particles and larger ratio of interaction for smaller particles, may explain why smaller particles were stable on the support but ripened, and why larger particles were recorded to be mobile. Future work on flat samples could involve various supports in order to determine which support makes the most stable catalyst and modeling that includes particle-particle interaction could be included. The addition or subtraction of functional groups on a single carbon support could be used as a further probe on how it affects atomic dispersion and adsorption. New in-situ studies performed at atmospheric pressure could be of use as pressures may influence the rate of sintering and the stability of the metal nanoparticles

Community Program Resource Guide of Activities for Youth

Youth Alliance serves 81% of clients who are economically disadvantaged in the community of Hollister, with 75% identifying as Hispanic, and 70% of participants between the ages of 6-17. The problem to address is the community\u27s lack of youth social support. The project is a Program Resource Guide for the clients of Youth Alliance. This project will address the issues of parents being unable to find accurate start dates, prices, and any financial assistance. An expected outcome of community collaboration around providing activities for youth is a decrease in crime, drug, and violence rates within the youth population. The project has met its expected outcome by making it less difficult for parents to seek sports and activities for their youth. The parents could find mostly all the information they needed in one place. The next step Youth Alliance should take is to continue to update the Community Resource Guide for the families they serve. Youth Alliance should also consider sharing the guide out more into the community to lessen the problem of other families not having access to information on keeping their youth in extra-curricular activities

Trophic plasticity of omnivorous fishes in natural and human‐dominated landscapes

The persistence of diverse communities and functioning ecosystems under increasing anthropogenic pressure relies on food web rewiring and the ability of animals to expand or change their diet in disturbed ecosystems. We combined a suite of diet tracing techniques to study trophic plasticity in omnivorous fishes, ecomorphologically similar species with high competition potential, across different human land uses in subtropical streams. We found that the proportion of native forest cover, associated with intensive land use, altered the isotopic composition of fishes, which were more enriched in 13C, without affecting the carbon isotope ratios of their prey and basal resources. There was also evidence for a nonlinear effect of native forest cover on the δ15N values of basal resources, macroinvertebrates, and omnivorous fishes, indicating that nutrient pollution from agriculture propagated through stream food webs. The most widely distributed fish species shifted their diet from autochthonous resources to terrestrial invertebrates and sedimentary organic matter in disturbed streams. Moreover, the isotopic niche of this fish species was broader in streams with higher fish species richness, indicating the combined impacts of environmental change and competition on species coexistence. Therefore, our findings showed that the dominance and trophic niche breadth of dominant omnivores depend not only on the availability of resources but also on the interactions with their putative competitors

Linking anatomical and histological traits of the digestive tract to resource consumption and assimilation of omnivorous tetra fishes.

This study explores the interplay between digestive tract traits, food intake, and assimilation in omnivorous tetra fishes (Psalidodon bifasciatus, P. aff. gymnodontus, and Bryconamericus ikaa) from the Iguaçu River basin, an ecologically significant region known for high endemism. We hypothesize that variations in digestive tracts across species would be associated with differences in diet, isotopic composition in fish tissues, and overall diet assimilation. To test this, we employed stereoscopic and light microscopy to characterize the gross anatomy, histomorphology, and histochemistry of fish digestive tracts. Additionally, we used stomach content and stable isotope analyses to trace fish diets. While these tetra fishes shared histological structures, disparities were noted in anatomical digestive traits and diet preferences. The smallest species, B. ikaa, with a shorter intestine, had fewer pyloric caeca and primarily consumed animal-based diets. Conversely, P. bifasciatus and P. aff. gymnodontus, with longer intestines, displayed numerous pyloric caeca and consumed a balanced mix of animal and plant items. Despite anatomical and dietary differences, all three species predominantly assimilated animal-origin food. The tetra fishes had histological variations among digestive tract segments, with the esophagus having the thickest muscular layer, gradually thinning towards the posterior intestine. The final portion of the intestine exhibited a significant expansion in the lumen perimeter, while the esophagus had the smallest lumen area. Goblet cells were most concentrated in the posterior intestine for all species. The gross anatomy of these tetra fishes aligns with their omnivorous habit, while diet assimilation was dominated by animal-origin food. These findings provide crucial insights into the structural and tissue characteristics of their digestive systems, laying the groundwork for deeper exploration into the physiological aspects of their digestive tracts and enhancing our understanding of their feeding strategies

Fish fauna of headwater streams of Perobas Biological Reserve, a conservation unit in the Atlantic Forest of the Northwestern Paraná state, Brazil

The Perobas Biological Reserve is a Conservation Unit characterized by two physiognomies of the Atlantic Forest: Semideciduous Seasonal Forest and Mixed Ombrophilous Forest. The reserve is situated on a ridge watershed between the basins of the Piquiri and Ivaí rivers, Upper Paraná River and had its fish fauna surveyed for the first time. Fishes were collected quarterly from December 2010 to March 2012, using electrofishing in five stretches of 50 m along the four streams, and gillnets only at one site in December, 2010. A total of 2628 individual were collected, belonging to 34 species in 25 genera, 13 families and six orders. Ten taxa may be new species or part of a complex of species within each genus, and requiring more detailed taxonomic revisions. Nine species are the first records for the Piquiri river basin

Amphibia, Anura, Leptodactylidae, Leptodactylus mystaceus (Spix, 1824): distribution extension

This study presents the first record of Leptodactylus mystaceus at the Municipality of Maringá, Paraná state, and its first occurrence at the South Region of Brazil, indicating the expansion of its geographic distribution.

Levantamento de parasitoses intestinais na cidade de Cianorte - PR no período de outubro de 2002 a março de 2003 em pacientes da rede pública de saúde

O presente trabalho teve como objetivo verifi car a freqncia das parasitoses intestinais na cidade de Cianorte-PR, onde foram analisados 303 exames parasitolgicos de fezes no perodo de outubro de 2002 a maro de 2003. Foramanalisados os parasitas encontrados, a faixa etria do paciente e o setor ao qual pertencia. Verifi cou-se a ocorrncia de maiornmero de exames negativos do que positivo, sendo que os parasitas mais freqentes foram ancilostomdeos (39,81%),Entamoeba histolytica (31,48%), Giardia lamblia (17,59%), Enterobius vermiculares (9,26%) e Ascaris lumbricides(1,85%). A faixa etria mais afetada foi a idade escolar (6-20 anos), fato relacionado ao maior contato dessas crianas entresi, o que pode favorecer a disseminao dessas parasitoses. Apenas o Bairro Pedro Moreira apresentou mais exames positivosdo que negativos, fato esse devido s baixas condies sanitrias e ao tipo de atendimento mdico realizado no local

Seasonality and interspecific competition shape individual niche variation in co‐occurring tetra fish in Neotropical streams

The drivers of intraspecific niche variation and its effects on species interactions are still unclear, especially in species-rich Neotropical environments. Here, we investigated how ecological opportunity and interspecific competition affect the degree of individual trophic specialization and the population niche breadth in tetra fish. We studied the four ecologically similar species (Psalidodon aff. gymnodontus, P. aff. paranae, P. bifasciatus, and Bryconamericus ikaa) in subtropical headwater streams (three sites with two co-occurring species and three sites with only one species). We sampled fish in two contrasting seasons (winter/dry and summer/wet) and quantified their trophic niches using gut content analysis. Psalidodon bifasciatus was the only species distributed over all the sampled streams. We observed seasonal differences in population trophic niche breadth of P. bifasciatus just when this species co-occurred with P. aff. gymnodontus. These findings confirm the complex nature of the effects of interspecific competition, depending, for instance, on the identity of the competitor. The degree of individual specialization of P. bifasciatus was higher in the winter, and it was not influenced by the presence of another species. Conversely, the other two Psalidodon species studied presented greater individual specialization in the summer, when fish consumed a higher proportion of allochthonous items (terrestrial insects and seeds), and there were no effects only for B. ikaa. Herein, our results suggest that seasonality in food-resource availability is a major driver of niche variation and it has the potential to play an important role in how these similar tetra species interact and coexist.info:eu-repo/semantics/publishedVersio

SPECIES COMPOSITION AND ABUNDANCE OF NON-NATIVE SPECIES IN STREAMS UNDER URBAN INFLUENCE

A introdução de espécies não-nativas em ambientes de água doce é uma das maiores ameaças à biodiversidade. Em ambientes urbanizados, as espécies não-nativas tem se proliferado em detrimento das nativas. O objetivo deste estudo é relatar a composição de espécies e a abundância de espécies não-nativas em riachos urbanos na região de Cascavel. Os peixes foram amostrados por pesca elétrica em quatro riachos. No total foram amostradas 31 espécies de peixes, entre as quais, cinco foram espécies não nativas, destacando-se Poecilia reticulata e Gymnotus sylvius. Esse estudo contribui para programas de manejo objetivando a sustentabilidade em riachos urbanos