Representations in Density Dependent Hadronic Field Theory and compatibility with QCD sum-rules

Different representations of an effective, covariant theory of the hadronic interaction are examined. For this purpose we have introduced nucleon-meson vertices parametrized in terms of scalar combinations of hadronic fields, extending the conceptual frame of the Density Dependent Hadronic Field Theory. Nuclear matter properties at zero temperature are examined in the Mean Field Approximation, including the equation of state, the Landau parameters, and collective modes. The treatment of isospin channels in terms of QCD sum rules inputs is outlined.Comment: 23 pages, 6 PostScript figures, Revtex4 clas

Two Tunnels to Inflation

We investigate the formation via tunneling of inflating (false-vacuum) bubbles in a true-vacuum background, and the reverse process. Using effective potentials from the junction condition formalism, all true- and false-vacuum bubble solutions with positive interior and exterior cosmological constant, and arbitrary mass are catalogued. We find that tunneling through the same effective potential appears to describe two distinct processes: one in which the initial and final states are separated by a wormhole (the Farhi-Guth-Guven mechanism), and one in which they are either in the same hubble volume or separated by a cosmological horizon. In the zero-mass limit, the first process corresponds to the creation of an inhomogenous universe from nothing, while the second mechanism is equivalent to the nucleation of true- or false-vacuum Coleman-De Luccia bubbles. We compute the probabilities of both mechanisms in the WKB approximation using semi-classical Hamiltonian methods, and find that -- assuming both process are allowed -- neither mechanism dominates in all regimes.Comment: 16 PRD-style pages, 13 figures. PRD, in press. Revised to match published versio

Identifying the needs of the Purhepecha children and families: An indigenous population of immigrants from Michoacan Mexico living in the the United States

The purpose of this study was to identify the needs of the Purhepecha children, also referred to as Tarascan, and their families living in the Eastern Coachella Valley located in California. A questionaire was developed by the author in order to identify the population\u27s specific needs. Ultimatley, it is with hope that the Purhepecha people\u27s needs will be understood as relevant to their language and culture, and make these needs public for other professionals working with this population

Autoinhibition and Activation of Parkin

Mutations in the gene encoding parkin, an E3-ubiquitin ligase, result in 50% of Autosomal Recessive Juvenile Parkinsonism cases. Parkin has been identified as a key mediator of mitochondrial regeneration following oxidative stress, and pathogenic mutations have been shown to impair its ubiquitin ligase activity. Neurodegeneration of dopamine-producing neurons appears to be a downstream consequence of parkin loss-of-function, resulting in early-onset forms of Parkinson’s disease. Although ubiquitination activity is essential for its neuroprotective function, parkin is autoinhibited in its native state by various mechanisms, including its N-terminal ubiquitin-like (UBL) domain. Therefore, the overarching objective of this thesis was to structurally characterize the autoinhibited state of parkin and determine how this inactive structure is modified to a catalytically-competent form. It was determined that autoinhibited parkin maintains a compact tertiary structure mediated by a tight intramolecular association between the UBL and C-terminal region. A high-resolution NMR strategy was developed and used to identify the binding site of the UBL domain that further revealed allosteric structural changes associated with UBL binding and displacement. Recently, multiple reports emerged identifying serine 65 phosphorylation of both ubiquitin and parkin’s UBL domain as key inducers of parkin activity. To examine the roles of these phosphorylation signals, several methods were used to generate homogenous S65-phosphorylated ubiquitin and UBL including: chemical modification, orthogonal translation, and phosphorylation by a catalytically-active kinase. Thermodynamic parameters of ubiquitin and UBL binding to parkin were measured and it was demonstrated how these are significantly altered upon S65 phosphorylation to promote a loss of autoinhibition. To understand the structural consequences of S65 phosphorylation, the three-dimensional structure of the phosphorylated parkin UBL was solved. Phosphorylation impacts the structure, stability and autoinhibitory association of the UBL domain in parkin. Further, cooperative roles of phospho-ubiquitin and phospho-UBL were established in reorganizing the parkin to an extended structure, allowing its engagement in the ubiquitination cascade. Finally, to investigate a chemical mechanism of catalysis in activated parkin, a detailed characterization of active site atoms in parkin was performed. Chemical biology approaches were used to generate an activated parkin~ubiquitin intermediate that will provide further mechanistic insight into ubiquitin transfer onto mitochondrial substrates

Wide Angle: Eadweard Muybridge, the Pacific Coast, and Trans-Indigenous Representation

Eadweard Muybridge's Pacific Coast photographs provide an important site for investigating Victorian visual practices and their relationship to imperial control. This essay's analysis of critical spatiality engages with the familiar temporal dimension of the "long nineteenth century" through discussions of periodicity and the representation of timescales in nineteenth-century media

Pigmentary Uveitis

The recent report by Townsend and Gornik aims to provide more reliable data on the prevalence of two common but poorly understood ocular conditions of Golden Retrievers: uveal cysts and pigmentary uveitis (PU). The study is well designed in terms of patient selection and examination methods, and high degree of disease ascertainment and diagnostic consistency was obtained by having all examinations performed by a single board-certified veterinary ophthalmologist. Even though this and two other studies suggest that these two conditions may perhaps be part of a broader disease complex, there is, as yet, no conclusive evidence of such an association

Window Into Retinal Studies

Professor Gustavo Aguirre discusses the context of his research studies at the University of Pennsylvania, which are currently concentrating on the degenerative disease, retinitis pigmentosa