Composite structural members for short span highway bridges

Ulloa Barbaran, Fernando Valentin The University of Texas at Austin 2002 해외박사(DDOD)

This research focused on the development of a structural system composed of a reinforced concrete (RC) deck and fiber reinforced plastic (FRP) girders and arches. The deck and the girders were designed to carry the load by means of composite action. This system can be used in applications such as short span bridges. The research study involved both experimental and analytical work. In all, six full-scale specimens were tested. Each specimen was composed of an RC deck and an FRP component, i.e. girder, arches. The length of each specimen was 30 ft, with a clear span between supports of 28.5 ft. The RC deck had an average width of 4 ft., and a thickness of 6 in. Both short and long term loading was considered. Pultruded and contact molded FRP girders were utilized. A pair of arches assembled with filament wound FRP pipes also was studied as an alternative to the girders. Based on the experimental results, the structural system proposed was found to be suitable for short span bridge applications. Furthermore, the excellent corrosion resistance of the FRP makes this system ideal for applications in corrosive environments. Finally, the experimental data was used to develop design recommendations for the proposed structural system.

Novel Data-Adaptive Statistical Methods for Observational and Experimental Studies with Applications to HIV/AIDS Research

Ulloa, Ernesto J University of Washington ProQuest Dissertations & 2022 해외박사(DDOD)

Data-adaptive statistical methods can often be used to improve different attributes of estimators, such as their asymptotic variance, calibration, and predictive accuracy. In this dissertation, we (i) describe how careful estimation of the propensity score can be used to improve the efficiency of a matching estimator; (ii) propose and examine the asymptotic properties of isotonic calibration in the context of conditional average treatment effect estimation; and (iii) implement and assess a SuperLearner for HIV risk prediction that can be used to improve the precision of treatment effect estimators in HIV prevention trials. Matching adjusts for confounding by comparing individuals with similar propensity score; however, it often results in an inefficient estimator. In Chapter 2, we propose mitigating this inefficiency by including an optimal covariate ---estimated via data adaptive methods--- in the propensity score model. Chapter 3 describes how isotonic calibration, paired with flexible estimation of the pseudo-outcomes, can be used to calibrate a given CATE estimator. We provide rates of convergence of our method's calibration and predictive performance. Finally, in Chapter 4, we propose using flexible data adaptive methods to implement a Super Learner for HIV prediction and assess its performance when predicting HIV risk based on different combinations of baseline covariates and varying risk time windows.

Flaming as an alternative weed control method for agronomic crops in organic and conventional production

Ulloa, Santiago M The University of Nebraska - Lincoln 2010 해외박사(DDOD)

Organic producers are interested in testing propane flaming as part of an integrated weed management program for organic crop production. Field experiments were conducted at the Haskell Agricultural Laboratory of the University of Nebraska, Concord, NE in 2007--2008 and 2008--2009 utilizing several doses of propane applied at different plant growth stages depending on the crop and the weed species evaluated. The response of plant species to propane doses was described by log-logistic models based on visual estimates of injury and plant dry weight. Grass weed species were more tolerant than broadleaf species. A propane dose of about 76 to 85 kg/ha provided a 90% dry matter reduction at 14 days after treatment in grasses compared to 40 to 68 kg/ha broadleaf species. Corn treated at 5-L was the most tolerant stage for broadcast flaming, whereas 2-L stage was the most susceptible, resulting in the highest visual crop injury, dry matter reduction, and yield loss. Soybean at cotyledon (VC) stage was the most tolerant whereas unifoliate (VU) stage was the most susceptible to broadcast flaming resulting in the highest visual crop injury, and the largest yield loss. Additionally, greenhouse experiments were conducted at University of Nebraska-Lincoln East Campus Lincoln, NE during April and September of 2009. Two crops (corn and soybean) and two weed species (velvetleaf and green foxtail) were evaluated. Leaf relative water content (RWC) was measured before treatment application. All plant species had lower leaf RWC during the afternoon. This low RWC increased their susceptibility to flaming. Based on these results, plant response to flaming was influenced by propane dose, growth stage, and time of day when flaming was conducted. Broadleaf weeds and soybean were more susceptible, while grass weeds and corn were more tolerant to broadcast flaming. Plants flamed during the afternoon presented more damage than the ones flamed in the morning. Flaming has a potential to be used effectively in controlling weeds in organic crop production systems when conducted properly at the right crop and weed growth stages and at the appropriate time of day.

The copper chaperone as a dual regulator of effects related to oxidative stress and chromatin remodeling

Ulloa, Janella L The Johns Hopkins University 2009 해외박사(DDOD)

The goal of this thesis was to understand the biological roles of the CCS copper chaperone. CCS is known to activate Cu/Zn superoxide dismutase (SOD1), although the precise mechanism is unclear. Guided by published three-dimensional structures of CCS, we used site directed mutagenesis in Chapter 2 to explore CCS activation of SOD1. The N-terminal Domain I of CCS contains a CXXC motif that is believed to coordinate copper together with a CXC motif at the C-terminal Domain 3. Surprisingly, however, we observed that only the CXC cysteines of yeast Ccs1p Domain 3 are required for Sod1p activation; the CXXC site of Domain 1 is not. Moreover, mutations expected to disturb a flexible linker region in Domain 1 also had no effect on yeast Sod1p activation. The Domain 1 CXXC site is clearly not as critical as once thought. CCS Domain 2 docks with SOD1, and we examined specific structural differences between yeast and human Domain 2, namely the disulfide cysteines of human CCS and the extended loop region of yeast Ccs1p. Neither was found necessary for SOD1 activation under physiological conditions but may become important stabilizing features under certain types of stress. Lastly, Chapter 2 addresses the CCS-SOD1 docked complex. The crystal structure of the yeast Ccs1p-Sod1p complex curiously revealed a heterotetramer rather than heterodimer and an unexpected intermolecular disulfide between CCS and SOD1. We probed these findings by mutagenesis and observed that residues expected to promote CCS-CCS interactions in the heterotetramer, as well as a lysine predicted to stabilize the CCS-SOD1 intermolecular disulfide, were all important for SOD1 activity. The crystal structure may in fact represent an accurate snap shot of CCS in action. Chapter 3 addresses a novel role of yeast Ccs1p, namely in chromatin silencing. Previous microarray analysis in the Culotta laboratory noted that loss of Ccs1p in yeast is associated with de-repression of the HMR mating type and subtelomeric "silenced" loci. Here we confirm these findings by RT and real time PCR and demonstrate that the third silenced loci in yeast, the rDNA, is also de-repressed in ccs1Delta strains. Moreover, de-repression of these silenced loci is not observed in sod1Delta strains and loss of rDNA silencing in ccs1Delta strains is retained in an anaerobic environment. Hence, the effects of ccs1Delta mutations on chromatin silencing are independent of SOD1 and oxidative stress. In Chapter 4, we explore possible mechanisms by which loss of Ccs1p affects chromatin silencing. The NAD dependent histone deacetylase Sir2p of yeast is known to mediate silencing of all three loci, however, our studies failed to demonstrate an effect of ccs1Delta mutations on Sir2p protein levels or enzymatic activity. Yet during the course of these studies, we uncovered a new effect of ccs1Delta mutations on chromatin remodeling that is dependent on oxidative stress. We demonstrate that in cells lacking either CCS1 or SOD1, the histone 3 lysine 56 (H3 K56) remains hyperacetylated at the G2/M phase of the cell cycle, similar to what is observed in cells lacking the histone deactylase HST3. Overall these studies help establish new roles for CCS in chromatin remodeling that are both independent (silenced loci) and dependent (H3 K56 aceylation) of oxidative stress. Possible mechanisms are discussed herein.

Epsilon Multiplicity Of Modules with Noetherian Saturation Algebras

Ulloa-Esquivel, Roberto A Purdue University ProQuest Dissertations & Theses 2020 해외박사(DDOD)

In the need of computational tools for ε-multiplicity, we provide a criterion for a module with a rank E inside a free module F to have rational ε-multiplicity in terms of the finite generation of the saturation Rees algebra of E. In this case, the multiplicity can be related to a Hilbert multiplicity of certain graded algebra. A particular example of this situation is provided: it is shown that the ε-multiplicity of monomial modules is Noetherian. Numerical evidence is provided that leads to a conjecture formula for the ε-multiplicity of certain monomial curves in A 3.

Pertenencias pasajeras. La escena subterranea en Peru durante los anos ochenta

Rodriguez-Ulloa, Olga Columbia University 2015 해외박사(DDOD)

The dissertation investigates a repertoire of ideas and objects produced by the Underground Scene (Escena Subterranea) that problematize notions of property within the Peruvian culture and society of the time. This is a young subcultural and countercultural social formation that bonded around rock music and created urban interventions, fiction and non-fiction literature, visual arts and music. My inquiry focuses on how this scene perceived as marginal contested well-established aesthetic practices and believes. I trace the way in which their poems, lyrics, interviews, cassette tapes, covers and prints deal with the expectations of what is appropriate and proper to, often migrant, young mestizo, working-class people within the cultural field. The conditions placed by the Peruvian Internal Conflict (1980-2000) and the migration of rural Peruvians to Lima created a social space where matters of property of land and circulation of people and goods were pivotal to the social experience. Literary and art criticism, along with the historical accounts of music, tend to explain the communal configuration of the scene and its aesthetics in relation to the violence of the armed struggle. These, I argue, also take from the coexistence with the migrants. The Underground Scene produced alongside with a massive marginality of indigenous rural migrants, appropriating their cultural and aesthetic procedures as well as their organizational forms. It worked within the war reflecting upon its various immediate consequences through a generational perspective using tactics borrowed from international subcultures such as the DIY, and others like piracy vastly and successfully used by the migrants. While this influence has been read as purely cultural, I am proposing a material approach. I claim that these conditions of production shaped up in a definitive way what is widely taken as a subculture and counterculture arranged as a mere imitation of the Anglo-Saxon, white, male punk movement. By using the tropes of voice, yell and noise rather than discourse or logos, these youth gave their criticism and affectivity a political dimension that pointed out the failure of party politics and democracy within the national structure.

Climate Displacement, Migration and Relocation in the United States: Resistance, Restoration and Resilience in the Coastal South

Butler-Ulloa, Debra Maria University of Massachusetts Boston ProQuest Disser 2022 해외박사(DDOD)

The story of the Gulf of Mexico began during the Late Triassic breakup of Pangea which resulted in the collapse of the Appalachian Mountains. This earth story is told through layers of strata and sediment carried by rivers into the Gulf Basin. Humans migrated and settled on the Gulf of Mexico 30,000 years ago. These humans observed, interpreted and coded the Gulf’s geological, hydrological and cosmological phenomena through storytelling, which embedded humans within earth’s story as co-actants, inseparable from earth systems. Indigenous presence and praxis remain, overlaid with invasion, colonization, genocide, forced removal and enslavement. Climate change and its impact on coastal systems threatens all life in the Gulf. Storytelling of the present observes, interprets and codes the poisoning of complex air-ocean-land interfaces, estuaries, wetlands, barrier islands and marine life. My research examines the praxis of storytelling in tribal and place-based communities along the northern coast of the Gulf of Mexico. I approach this transdisciplinary work in collaboration and reciprocity with communities who use storytelling to recreate and transfer knowledge, and to transform behaviors of resilience, resistance, resourcing and restoration. In my three-paper dissertation, the first paper lays out the landscape for the study, combining geography with the layers of stories that bring a topography and a place to life. The second paper introduces the communities of Turkey Creek, Poarch Creek, and Isle de Jean Charles, whose approaches to resilience through history, stories, political action, and ongoing commitment to justice and self-determination bring forth new meanings and practices of resilience. In the third paper, I use the metaphor of gumbo to explore traditions, resources, and the practice of doing transdisciplinary research. Overall, my dissertation honors indigenous knowledge and points toward new ways forward in the face of climate change.

The consequences of land-use on subsidies of stream insects to terrestrial consumers

Chaves-Ulloa, Ramsa Dartmouth College 2015 해외박사(DDOD)

The image of a child standing at the side of a creek and skipping stones across it exemplifies how we tend to mentally separate aquatic habitats from dry land. But there is a constant exchange of materials from land to streams, and vice-versa. Ecologists have long recognized the importance of this material exchange, however most of our knowledge on aquatic terrestrial linkages comes from research developed in temperate, forested sites. Undisturbed, forested areas are becoming increasingly rare, however, thus there is a gap in our understanding of how the movement of materials from streams to land affects riparian food webs in systems affected by land-use change, particularly in the tropics. Moreover, research into aquatic-terrestrial linkages tends to focus on "good" subsidies such as carbon and nutrients, but "bad" subsidies, such as methylmercury, are also exported from streams to land. Through several large scale field studies I explore and elucidate how land-use change affects aquatic-terrestrial linkages and the effects on riparian food webs. My results suggest that agricultural land-use change is associated with changes in the composition of stream subsidies to land via changes in the community of benthic invertebrates. However, agriculture was not associated with changes in the magnitude of the subsidy to land. In the Costa Rica system, the magnitude of the subsidy increases with catchment area, a variable associated with increased nutrients. Additionally, my results show that the stream subsidy affects the community of riparian invertebrate predators in tropical dry forest streams. Finally, my results suggest that changes in dissolved organic carbon modulate the movement of methylated mercury from streams to terrestrial consumers. Taken together, this dissertation increase our understanding of aquatic-terrestrial linkages in the context of human activities, and highlights the importance of these subsidies for terrestrial consumers.

Theoretical aspects of Panoan metrical phonology: Disyllabic footing and contextual syllable weight

Elias Ulloa, Jose A Rutgers The State University of New Jersey - New B 2006 해외박사(DDOD)

This dissertation studies the relation between foot size and contextual syllable-weight. In particular, it focuses on the influence that foot disyllabicity has on triggering quantity adjustments of syllable weight. Within Optimality Theory (Prince and Smolensky 1993; 2004), this dissertation formally addresses the relation between foot size and syllable weight through the stringency relation between two constraints: *FOOT(sigma) and *F OOT(mu). The former penalizes feet smaller than two syllables and the latter, feet smaller than two moras. In isolation, they create a scale in which disyllabic feet are more preferable than monosyllabic feet and, in turn, bimoraic monosyllabic feet (symbolized as (H)-feet) are more preferable than monomoraic monosyllabic feet (symbolized as (L)-feet). The existence of other conflicting constraints can, however, prevent the occurrence of disyllabic feet, which in turn causes the emergence of monosyllabic feet. Whether feet are disyllabic or monosyllabic in a given context depends on the conflict between respecting the constraints that inhibit quantity adjustments, complying with those that restrict the distribution of syllable weight and satisfying the constraints *FOOT(sigma) and *FOOT (mu). Empirically, the relation between foot disyllabicity and quantity adjustments of syllable weight is studied through the detailed examination of two Panoan languages spoken in the Peruvian Amazon: Shipibo and Capanahua. The data presented is the result of several fieldtrips carried out by the author. Although both languages are trochaic by default and distinguish heavy versus light syllables, (H)-feet are avoided in favor of disyllabic feet. In order to obtain disyllabic feet and avoid heavy syllables as heads of uneven (H.L)-trochees or in unstressed positions, Shipibo and Capanahua contextually adjust vowel length and the weight of closed syllables. The disyllabic footing of Shipibo and Capanahua is not only supported by the distribution of heads within the Prosodic Word (PrWd) but also by a number of segmental rhythmic phenomena; for example, rhythmic allomorphy, long vowels and heavy closed syllables restricted to even syllables, inhibition of glottal coalescence in odd syllables.

The Impact of Diabetes on an Aging Developing Country: Costa Rica

Santamaria-Ulloa, Carolina The University of Wisconsin - Madison 2013 해외박사(DDOD)

Along with many other countries in Latin America and the Caribbean, Costa Rica is undergoing very high rates of growth of the elderly population. These populations are experiencing an increase in the prevalence of obesity-related conditions such as diabetes. Diabetes is a major cause of both morbidity and mortality among the elderly and represents a source of demands on already constrained healthcare systems. In this dissertation I estimate diabetes incidence and prevalence, identify its most important determinants, and assess the impact on years of life lost and the economic burden on the public health care system. More than a fifth of Costa Rican elderly experience diabetes. Incidence is estimated at 5 per 1000 person-years in population 30+. The disease is strongly associated with increased premature mortality, especially at ages 60-69. Family history of diabetes is a non trivial risk factor. I find a clear gradient between diabetes and obesity. Individuals who are obese and have an increased waist circumference experience much higher risk of contracting diabetes. Similarly, I find that geographical barriers to health care translate into a lower probability of diagnosis. Health care costs associated with diabetes are very high as this population requires much larger expenditures in hospitalizations, outpatient care and medications than the non-diabetic. Diabetes prevalence will continue to increase in the near future. At least 27% of the elderly is expected to be diabetic by 2025 and the elderly population with the disease will double between 2010 and 2025 implying a massive increase in the health care costs. The impact of diabetes on life expectancy at age 60 around the year 2025 is estimated to lead to a loss of about 7 months. Public policy targeted on education about the behaviors that prevent the onset of diabetes will save lives and reduce costs to the public health care system. Prevention also requires a population health approach to create environments in which individuals are encouraged to alter behaviors. The ultimate influence of diabetes in Costa Rica will be brought under control only if policies aimed at reducing risk factors, especially obesity, are quickly put in place.