The contribution of young-of-year fishes to aquatic food web dynamics in an arid-land river system (Rio Grande, New Mexico)

1. Larval fishes have a rich history in ichthyological research. However, relatively little attention has been given to the role of young-of-year (YOY) fishes in ecosystem processes. Despite difficulties of sampling and identifying these small fishes, YOY may serve an important role in the dynamics of some aquatic communities. The specific role of YOY fishes in aquatic, desert food webs remains largely uncharacterized. 2. We hypothesize that YOY fishes may control abundance and community composition of lower trophic levels (i.e., aquatic invertebrates) because they are numerically dominant predators during the growing season. The goal of this study is to determine the role of YOY fishes in aquatic food webs and the impact they have on trophic dynamics of dryland river food webs using the Rio Grande as an example. 3. A mesocosm experiment was designed to assess the effect of YOY fish predators on meio- and micro- faunal invertebrate prey density and diversity. We manipulated presence and absence of YOY fishes and leaf litter, and compared invertebrate diversity and abundance across an array of 24 stock tanks. 4. Data showed that YOY fishes significantly influence the composition of invertebrate communities, as does allochthonous carbon. Community composition varied among treatments both because fishes preferred some taxa over others and because of instances of avoidance by invertebrates. Stable isotope analyses (carbon and nitrogen) suggest important indirect effects on the behavior of invertebrates in fish-treated mesocosms. 5. Results suggest that YOY fishes play an important role in aquatic food web dynamics and that community composition of aquatic invertebrates is, in part, subject to direct and indirect changes induced by the presence of YOY fishes

Drivers And Impacts Of The Invasive Round Goby (neogobius Melanostomus) In Michigan Tributaries To The Great Lakes

The abundance and persistence of the invasive round goby (Neogobius melanostomus) has often resulted in antagonistic interactions between the invasive and its native competitors. In this study, I sought to quantify the consequences and environmental context of these interactions in Great Lakes tributaries. Specifically, I aimed to identify changes in feeding and reproductive behavior in a native competitor in response to round goby invasion, identify potential solutions to increase regular stream monitoring by tapping into citizen science programs, and quantify the environmental context associated with successful goby invasion. Surveys of fish communities were conducted over three years in seven Michigan tributaries to the Great Lakes. Each site was evaluated for fish assemblage composition, round goby abundance, and habitat quality. Individual round goby and a native competitor, the Johnny darter (Etheostoma nigrum), were dissected for a diet comparison and to identify investment in reproduction to illustrate changes in feeding and reproductive behavior by the native species. To inform better practices for stream management and invasion detection, a quality assessment of two citizen science programs in the area was completed. Citizen data was directly compared to traditional research focused sampling methods to verify the validity of the data and its potential inclusion in ecological research. Finally, a model was developed to identify the environmental context common to sites invaded by round goby. Results suggest that Johnny darter diet diversity decreases, trophic position increases, and reproductive timing changes when goby are present. Citizen science may provide a way to monitor stream degradation which can facilitate these negative interactions. Despite differences in sampling methodology, qualitative citizen data reached similar conclusions about site quality as quantitative research methods. As identified by the environmental context model, altered riparian land use and decreased native species diversity are common characteristics of sites invaded by round goby. Regular monitoring for these characteristics may help identify locations vulnerable to round goby invasion so prevention and mitigation resources can be efficiently allocated. This research provides background on round goby invasion that can be utilized to better manage native species and ecosystems to increase resistance to and reduce the impacts of invasion

Reproductive phenology of fishes of the Rio Grande, New Mexico : a genes-to-community approach

Reproductive phenology is a key life history attribute of long lived organisms that can strongly affect reproductive success and, ultimately, drive community composition. Understanding the ecological causes and consequences and genetic mechanisms shaping reproductive timing is key to predicting the outcome of environmental change (e.g., climate change). The three chapters that comprised this dissertation were focused on elucidating the ecological and genetic underpinnings of reproductive timing in the fish community of an arid-land river, the Rio Grande, New Mexico. In Chapter 1, we assessed reproductive phenology in the Rio Grande fish community with four years of young-of-year sampling data and spanning 16 years, from 1995 to 2010. Spawning data suggested that, in addition to known spatial habitat partitioning of resources, species also partition resources temporally by differential spawning periodicity. Inter-annual variation in environmental conditions (e.g., river discharge) appears to drive community-level shifts in reproductive phenology. However, the magnitude of phenological shifts differed among species. We discuss these data in light of biotic-interactions among species and scenarios for future climate change. In Chapter 2, we examined within- and among-species DNA sequence variation in a candidate gene, Clock, which is a key circadian rhythm gene that may shape reproductive phenology of fishes of the Rio Grande. Previous research has demonstrated a role for Clock in migratory and reproductive timing in disparate organisms, from songbirds to salmon. In this study, we tested whether patterns of allele length variation in Clock are consistent with: (1) among-species differences in reproductive timing, (2) phylogenetic inertia, or (3) functional-constraint in this key circadian gene. We present evidence that all three of these evolutionary processes may shape patterns of variation in Clock observed in Rio Grande fishes. Finally, in Chapter 3 we broadened our search for genetic underpinnings of reproductive timing beyond Clock, to assess amino acid sequence variation in dozens of candidate genes among three species of Rio Grande cyprinid fishes: fathead minnow (Pimephales promelas), red shiner (Cyprinella lutrensis), and Rio Grande silvery minnow (Hybognathus amarus). We used next-generation 454 DNA sequencing to characterize the transcriptomes and explore sequence level variation among these three species. Using gene ontology analysis, we identified 86 candidate genes with functions potentially associated with reproductive timing and circadian rhythms. The 86 candidate genes had a total of 342 inferred amino acid substitutions among the three species, which could have functional implications and underlie some of the species-specificity in reproductive biology of these three species. Additionally, fifteen of the candidate genes had simple sequence repeats in their inferred amino acid sequences, which might be targets of natural selection for shaping circadian rhythms and reproduction. The variation described in this study affords candidate loci for future comparative studies of reproductive timing

Existence and Uniqueness of Solutions in Nonassociated Mohr-coulomb Elastoplasticity:<strong/>

In 1902 Jacques Hadamard [1] formulated three conditions that mathematical models of physical phenomena should satisfy, namely that: (a) A solution exists (b) The solution is unique (c) The solution depends continuously on the problem data Problems involving models that satisfy all of these conditions are termed well-posed. Otherwise, if one or more conditions are violated, the problem is said to be ill-posed. The meaning of condition (a) is quite clear. Conditions (b) and (c) are often intimately linked and can for many practical purposes be coalesced into a single condition. In finite element analysis “non-unique ” solutions are often generated by altering the problem data slightly, for example through introduction of random imperfections. It is relatively well known (though not always appreciated to its full extent) that standard elastoplastic constitutive models may violate conditions (b) and (c) if the flow rule is not associated. Indeed, since the pioneering work of Rice [2], the ensuing ill

Homogenized rigid-plastic model for masonry walls subjected to impact

A simple rigid-plastic homogenization model for the analysis of masonry structures subjected to out-of-plane impact loads is presented. The objective is to propose a model characterized by a few material parameters, numerically inexpensive and very stable. Bricks and mortar joints are assumed rigid perfectly plastic and obeying an associated flow rule. In order to take into account the effect of brickwork texture, out-of-plane anisotropic masonry failure surfaces are obtained by means of a limit analysis approach, in which the unit cell is subdivided into a fixed number of sub-domains and layers along the thickness. A polynomial representation of micro-stress tensor components is utilized inside each sub-domain, assuring both stress tensor admissibility on a regular grid of points and continuity of the stress vector at the interfaces between contiguous sub-domains. Limited strength (frictional failure with compressive cap and tension cutoff) of brick-mortar interfaces is also considered in the model, thus allowing the reproduction of elementary cell failures due to the possible insufficient resistance of the bond between units and joints. Triangular Kirchhoff-Love elements with linear interpolation of the displacement field and constant moment within each element are used at a structural level. In this framework, a simple quadratic programming problem is obtained to analyze entire walls subjected to impacts. In order to test the capabilities of the approach proposed, two examples of technical interest are discussed, namely a running bond masonry wall constrained at three edges and subjected to a point impact load and a masonry square plate constrained at four edges and subjected to a distributed dynamic pressure simulating an air-blast. Only for the first example, numerical and experimental data are available, whereas for the second example insufficient information is at disposal from the literature. Comparisons with standard elastic-plastic procedures conducted by means of commercial FE codes are also provided. Despite the obvious approximations and limitations connected to the utilization of a rigid-plastic model for masonry, the approach proposed seems able to provide results in agreement with alternative expensive numerical elasto-plastic approaches, but requiring only negligible processing time. Therefore, the proposed simple tool can be used (in addition to more sophisticated but expensive non-linear procedures) by practitioners to have a fast estimation of masonry behavior subjected to impact

Rural and Urban Underserved Program Update: Underserved-Focused Clinical Experiences

Support, mentor, and prepare interested medical students to fulfill their goal of effectively providing healthcare to underserved groups in New Mexico

A critical appraisal of "Effects of horse riding simulator on sitting motor function in children with spastic cerebral palsy"

The clinical question for the paper was can a horse riding simulator improve balance in children with cerebral palsy.This article chosen for this critical appraisal is “Effects of horse riding simulator on sitting motor function in children with spastic cerebral palsy.” Each section of the research article was analyzed for its strengths and weaknesses and evaluated for credibility. Overall, the study was credible and no major red flags were discovered. There were some minor issues but the majority of the article was written in a clear and logical fashion. The authors did their best to eliminate bias where they could, accurately interpreted their results in the discussion and acknowledged limitations to their study. The two biggest issues with the appraised paper were small organizational problems in the introduction that made it mildly confusing to read and difficult to understand tables. The results of the study support the implementation of HRS into standard treatment for children with spastic cerebral palsy and did not show any significant risks associated with the treatment. At the time of the appraisal, not much research has been done this intervention and further studies are need to determine just how effective (or non-effective) it is for improving balance in children with cerebral palsy

Quevedo y Proclo: lectura ontológica del soneto “Si quien ha de pintaros ha de veros”

Análisis de la influencia del neoplatonismo renacentista en el desarrollo de las convenciones anti-petrarquistas del Siglo de Oro tardío, plasmada en un soneto de Quevedo. La lectura muestra cómo el tropo procleano del «círculo de eros» da forma a la relación tópica del poeta con el objeto de su meditación, representada en esquemas retóricos y lenguaje derivados el discurso de la ontología neoplatónica. A study of the influence of Renaissance Neo-Platonism on the evolution of anti-Petrarchan conventions in the late Golden Age, as seen in a sonnet by Quevedo. The reading demonstrates how the Proclan trope of the «circle of eros» shapes the topical relationship between the poet and the object of his meditation, which is described in rhetorical structures and language derived from the discourse of Neo-Platonic ontology