GPS based tectonic analysis of the Aleutian arc and Bering plate

Thesis (M.S.) University of Alaska Fairbanks, 2007Global Positioning System (GPS) measurements enable a quantitative analysis of tectonic deformation in the Aleutian Islands, Alaska. We construct elastic deformation models to calculate coupling on the subduction interface and the interseismic strain recorded at stations throughout the Aleutian arc. Using a grid-search inversion procedure, we determine an arc translation velocity for each region of the arc, revealing south to southwest motions of 4 to 14 mm/yr. In the central Aleutians, there is good agreement between areas of high coupling and areas of large moment release in major seismogenic events. We have combined modeling results from the Aleutians with direct measurements of station velocities of sites in western Alaska and the Bering Sea islands to test the hypothesis of a clockwise rotating Bering plate. The Bering Sea area including the Aleutian arc and western Alaska is fit by an Euler pole located at 42.5°N, 121.3°E with an angular velocity of 6.0°/my, relative to stable North America. The Bering plate's eastern boundary appears to be related to left lateral faulting in interior Alaska as clockwise rotation of the plate results in south-southwest motion relative to the North American plate. The Bering plate's interaction with a counter-clockwise rotating southcentral Alaska block may be responsible for the decreased slip-rate on the western Denali fault. Thrust earthquake slip azimuths expose a systematic discrepancy with Pacific-Bering plate convergence direction. A simple model of slip partitioning and GPS measurements reveal that slip partitioning is present in the forearc throughout the arc but only develops in the back arc west of Amchitka Pass.1. Introduction -- 2. Plate coupling variation and block translation in the Andreanof segment of the Aleutian arc determined by subduction zone modeling using GPS data -- 3. Evidence for and implications of a Bering plate based on geodetic measurements from the Aleutians and Western Alaska -- 4. Conclusions

Poly-arginine peptide R18D reduces neuroinflammation and functional deficits following traumatic brain injury in the Long-Evans rat

We have previously demonstrated that the poly-arginine peptide R18 can improve histological and functional outcomes following traumatic brain injury (TBI) in the Sprague–Dawley rat. Since D-enantiomer peptides are often exploited in pharmacology for their increased stability and potency, the present study compared the effects of R18 and its D-enantiomer, R18D, following TBI in the Long-Evans rat. Following a closed-head impact delivered via a weight-drop apparatus, peptide was administered at a dose of 1000 nmol/kg at 30 min after TBI. Treatment with R18D, but not R18 resulted in significant reductions in sensorimotor (p = 0.026) and vestibulomotor (p = 0.049) deficits as measured by the adhesive tape removal and rotarod tests. Furthermore, treatment with R18 and R18D resulted in a significant reduction in brain protein levels of the astrocytic marker, glial fibrillary acidic protein (p = 0.019 and 0.048, respectively). These results further highlight the beneficial effects of poly-arginine peptides in TBI, however additional studies are required to confirm these positive effects

Histopathological Analysis of Quails in the Trans-Pecos Ecoregion of Texas

Quail populations in Texas, USA, have declined over the past few decades due primarily to habitat loss. The role that parasites may play in such declines has been a recent topic of concern. To help address this question, we collected 12 scaled quail (Callipepla squamata), 8 Gambel’s quail (Callipepla gambelii), and 3 Montezuma quail (Cyrtonyx montezumae) from across the Trans-Pecos ecoregion of Texas via hunter harvest, funnel traps, and night netting. Quail samples were necropsied to determine the abundance of eyeworms (Oxyspirura petrowi). Histopathological analyses were conducted on quail eyeballs and periocular tissues to gain information on parasite-related tissue damage and document other pathogenic factors. We calculated mean abundances of Oxyspirura petrowi for sampled scaled (x̄ = 5.5, standard deviation [SD] = 2.5, x̃ = 3, n = 12), Gambel’s (x̄ = 6.4, SD = 4.2, x̃ = 1.5, n = 8), and Montezuma quail (x̄ = 13, SD = 1.5, x̃ = 13, n = 3). Host tissues exhibited immune responses (i.e., lymphocytic conjunctivitis and plasmacytic adenitis) to O. petrowi. The observed immune responses indicated relatively mild irritation within the ocular tissues. It has been speculated that such irritation to ocular tissues could negatively impact quail vision. This potential impact is worth noting because quails rely on keen vision to detect predators. Future research should focus on measuring the effects of O. petrowi infections on quail survival

Assessment of R18, COG1410, and APP96-110 in excitotoxicity and traumatic brain injury

Cationic arginine-rich and poly-arginine peptides (referred to as CARPs) have potent neuroprotective properties in in vitro excitotoxicity and in vivo models of stroke. Traumatic brain injury (TBI) shares many pathophysiological processes as stroke, including excitotoxicity. Therefore, we evaluated our lead peptide, poly-arginine R18, with the COG1410 and APP96-110 peptides, which have neuroprotective actions following TBI. In an in vitro cortical neuronal glutamic acid excitotoxicity injury model, R18 was highly neuroprotective and reduced neuronal calcium influx, while COG1410 and APP96-110 displayed modest neuroprotection and were less effective at reducing calcium influx. In an impact-acceleration closed-head injury model (Marmarou model), R18, COG1410, and APP96-110 were administered intravenously (300 nmol/kg) at 30 minutes after injury in male Sprague- Dawley rats. When compared to vehicle, no peptide significantly improved functional outcomes, however the R18 and COG1410 treatment groups displayed positive trends in the adhesive tape test and rotarod assessments. Similarly, no peptide had a significant effect on hippocampal neuronal loss, however a significant reduction in axonal injury was observed for R18 and COG1410. In conclusion, this study has demonstrated that R18 is significantly more effective than COG1410 and APP96-110 at reducing neuronal injury and calcium influx following excitotoxicity, and that both R18 and COG1410 reduce axonal injury following TBI. Additional dose response and treatment time course studies are required to further assess the efficacy of R18 in TBI

Epidemic growth rates and host movement patterns shape management performance for pathogen spillover at the wildlife–livestock interface

Managing pathogen spillover at the wildlife–livestock interface is a key step towards improving global animal health, food security and wildlife conservation. However, predicting the effectiveness of management actions across host–pathogen systems with different life histories is an on-going challenge since data on intervention effectiveness are expensive to collect and results are system-specific.We developed a simulation model to explore how the efficacies of different management strategies vary according to host movement patterns and epidemic growth rates. The model suggested that fast-growing, fast-moving epidemics like avian influenza were best-managed with actions like biosecurity or containment, which limited and localized overall spillover risk. For fast-growing, slower-moving diseases like foot-and-mouth disease, depopulation or prophylactic vaccination were competitive management options. Many actions performed competitively when epidemics grew slowly and host movements were limited, and how management efficacy related to epidemic growth rate or host movement propensity depended on what objectivewas used to evaluatemanagement performance. This framework offers one means of classifying and prioritizing responses to novel pathogen spillover threats, and evaluating current management actions for pathogens emerging at the wildlife–livestock interface. This article is part of the theme issue ‘Dynamic and integrative approaches to understanding pathogen spillover’

“One Health” or Three? Publication Silos Among the One Health Disciplines

The One Health initiative is a global effort fostering interdisciplinary collaborations to address challenges in human, animal, and environmental health. While One Health has received considerable press, its benefits remain unclear because its effects have not been quantitatively described. We systematically surveyed the published literature and used social network analysis to measure interdisciplinarity in One Health studies constructing dynamic pathogen transmission models. The number of publications fulfilling our search criteria increased by 14.6% per year, which is faster than growth rates for life sciences as a whole and for most biology subdisciplines. Surveyed publications clustered into three communities: one used by ecologists, one used by veterinarians, and a third diverse-authorship community used by population biologists, mathematicians, epidemiologists, and experts in human health. Overlap between these communities increased through time in terms of author number, diversity of co-author affiliations, and diversity of citations. However, communities continue to differ in the systems studied, questions asked, and methods employed. While the infectious disease research community has made significant progress toward integrating its participating disciplines, some segregation—especially along the veterinary/ecological research interface—remains

Dehydropolymerization of Amine-Boranes using Bis(imino)pyridine Rhodium Pre-Catalysis: σ-Amine-Borane Complexes, Nanoparticles, and Low Residual-Metal BN-Polymers that can be Chemically Repurposed.

The sigma amine-borane complexes [Rh(L1)(h2:h2H3B·NRH2)][OTf] (L1 = 2,6-bis-[1-(2,6-diisopropylphenylimino)ethyl]pyridine, R = Me, Et, nPr) are described, alongside [Rh(L1)(NMeH2)][OTf]. Using R = Me as the pre-catalyst (1 mol%) the dehydropolymerization of H3B·NMeH2 gives [H2BNMeH]n selectively. Added NMeH2, or the direct use of [Rh(L1)(NMeH2)][OTf], is required for initiation of catalysis, which is suggested to operate through formation of a neutral hydride complex, Rh(L1)H. The formation of small (1-5 nm) nanoparticles is observed during catalysis, but studies are ambiguous as to whether the catalysis is solely nanoparticle promoted or if there is a molecular homogeneous component. [Rh(L1)(NMeH2)][OTf] is shown to operate at 0.025 mol% loadings on a 2 g scale to give polyaminoborane [H2BNMeH]n [Mn = 30,900 g/mol, Ð = 1.8] that can be purified to a low residual [Rh] (6 µg/g). Addition of Na[N(SiMe3)2] to [H2BNMeH]n results in selective depolymerization to form the eee-isomer of N,N,N-trimethylborazane [H2BNMeH]3: the chemical repurposing of a main-group polymer

Chinese overseas doctoral student narratives of intercultural adaptation

This study aims to explore how Chinese overseas doctoral students adjust to a different academic, social and cultural environment, using Giddens’ theoretical framework of self-identity (1991). The findings indicate the participants proactively used various coping strategies in meeting challenges, and adapting to new social environments. Continuity and stability of self-identity were achieved either culturally or academically through self-reflexivity, autonomy, creativity, authenticity, and reliance on an ontological identity. The result is to challenge the grand narrative of essentialised “problematic Chinese learners”

Inferring infection hazard in wildlife populations by linking data across individual and population scales

Our ability to infer unobservable disease-dynamic processes such as force of infection (infection hazard for susceptible hosts) has transformed our understanding of disease transmission mechanisms and capacity to predict disease dynamics. Conventional methods for inferring FOI estimate a time-averaged value and are based on population-level processes. Because many pathogens exhibit epidemic cycling and FOI is the result of processes acting across the scales of individuals and populations, a flexible framework that extends to epidemic dynamics and links within-host processes to FOI is needed. Specifically, within-host antibody kinetics in wildlife hosts can be short-lived and produce patterns that are repeatable across individuals, suggesting individual-level antibody concentrations could be used to infer time since infection and hence FOI. Using simulations and case studies (influenza A in lesser snow geese and Yersinia pestis in coyotes), we argue that with careful experimental and surveillance design, the population-level FOI signal can be recovered from individual-level antibody kinetics, despite substantial individual-level variation. In addition to improving inference, the cross-scale quantitative antibody approach we describe can reveal insights into drivers of individual-based variation in disease response, and the role of poorly understood processes such as secondary infections, in population-level dynamics of disease

Measurement of inclusive D*+- and associated dijet cross sections in photoproduction at HERA

Inclusive photoproduction of D*+- mesons has been measured for photon-proton centre-of-mass energies in the range 130 < W < 280 GeV and a photon virtuality Q^2 < 1 GeV^2. The data sample used corresponds to an integrated luminosity of 37 pb^-1. Total and differential cross sections as functions of the D* transverse momentum and pseudorapidity are presented in restricted kinematical regions and the data are compared with next-to-leading order (NLO) perturbative QCD calculations using the "massive charm" and "massless charm" schemes. The measured cross sections are generally above the NLO calculations, in particular in the forward (proton) direction. The large data sample also allows the study of dijet production associated with charm. A significant resolved as well as a direct photon component contribute to the cross section. Leading order QCD Monte Carlo calculations indicate that the resolved contribution arises from a significant charm component in the photon. A massive charm NLO parton level calculation yields lower cross sections compared to the measured results in a kinematic region where the resolved photon contribution is significant.Comment: 32 pages including 6 figure