Peer Mentorship in Nursing Schools: A Pilot Study

Undergraduate Theoretical Proposa

Hedonic Valuation of Sportfishing Harvest

A hedonic valuation strategy is introduced to estimate the marginal value of sportfishing harvest. The strategy uses market prices, thereby avoiding some of the measurement problems associated with the constructed or proxy prices used in common valuation methods. A charter fee hedonic equation is estimated using data from the market for offshore charter fishing in the Gulf of Mexico. The marginal value of sportfishing harvest is identified using spatial variation in harvest rates and fish sizes. A two-stage minimum distance estimator is used to address potential omitted variables and cluster-sampling issues. Our results demonstrate that valid estimates of the marginal value of sportfishing harvest can be derived directly using market prices. The estimated marginal value per fish is consistent with published estimates using alternative methods. Thus, the hedonic approach suggested in this article offers promise as an independent validation of the typical methods used to value sportfishing harvest.Sportfishing, charter boats, hedonic, revealed preference, valuation, Public Economics, Research Methods/ Statistical Methods, Q22, Q26, Q51,

An extended space approach for particle Markov chain Monte Carlo methods

In this paper we consider fully Bayesian inference in general state space models. Existing particle Markov chain Monte Carlo (MCMC) algorithms use an augmented model that takes into account all the variable sampled in a sequential Monte Carlo algorithm. This paper describes an approach that also uses sequential Monte Carlo to construct an approximation to the state space, but generates extra states using MCMC runs at each time point. We construct an augmented model for our extended space with the marginal distribution of the sampled states matching the posterior distribution of the state vector. We show how our method may be combined with particle independent Metropolis-Hastings or particle Gibbs steps to obtain a smoothing algorithm. All the Metropolis acceptance probabilities are identical to those obtained in existing approaches, so there is no extra cost in term of Metropolis-Hastings rejections when using our approach. The number of MCMC iterates at each time point is chosen by the used and our augmented model collapses back to the model in Olsson and Ryden (2011) when the number of MCMC iterations reduces. We show empirically that our approach works well on applied examples and can outperform existing methods.Comment: 35 pages, 2 figures, Typos corrected from Version

Does quorum sensing regulate the conjugation of the two co-resident megaplasmids of Agrobacterium tumefaciens 15955

While the effects of Agrobacterium tumefaciens can be easily observed and have been studied closely, the mechanisms for their virulence habits have not. Several studies have suggested the mechanisms for plasmid transfer and conjugation, particularly concerning plasmid Ti (pTi), the TraR (TraR1) regulator, and the quorum sensing (QS) system associated with it. Very little is known, however, about the second plasmid (pAt) present within the bacteria nor its regulatory QS systems. To further understand these mechanics of plasmid conjugation, we have devised a series of experiments in order to find connections between the conjugation of both pTi and pAt and the regulatory genes of TraR1 (of pTi) and TraR2 (of pAt). The first is designed to establish the impact of removal of both TraR1 and TraR2 on the conjugation of pTi. The second is to provide a connection between removal of both TraR genes on pAt conjugation. The third serves as a complimentary experiment to the first, testing the impact of the overexpression of the TraR genes on pTi conjugation. The fourth is then designed to compliment the second and discover the effect of the TraR genes’ overexpression on pAt conjugation. These studies, however, remain ongoing and incomplete

Bioinformatics analysis of homologies between pathogen antigens, autoantigens and the CFTR cystic fibrosis protein: A role for immunoadsorption therapy?

The cystic fibrosis CFTR chloride channel is involved in pathogen entry into epithelial cells, and provides the glutathione and hypochlorous acid necessary for bactericidal and viricidal actions. CFTR mutations block these effects, diminishing pathogen defence and allowing pathogen accumulation in the extracellular space, where antibody encounter is likely. The pathogen antigens observed in cystic fibrosis (including P. Aeruginosa, S.Aureus and S.Maltophilia proteins) are homologous to the autoantigens reported in cystic fibrosis and all are homologous to the CFTR protein itself. Antibodies to pathogens and autoantigens may also target the CFTR protein, acting as antagonists, further compromising its function. The tripartite relationship between pathogen antigens, autoantigens and the CFTR protein creates a feed forward cycle, diminishing the function of the CFTR protein and increasing the probability of pathogen accumulation and further antibody encounters at every turn. Kegg pathway analysis of the CFTR/autoantigen interactome indicates that the CFTR protein is also involved in pathogen entry pathways, diabetes and pancreatic and gastric acid secretion pathways, in pathways related to cardiac myopathy, and in the gonadotrophin signalling network, all which are relevant to cystic fibrosis. Interruption of this cycle by antigen and antibody adsorption, and possibly by immunosuppressant therapy may perhaps be of clinical benefit in cystic fibrosis

Proteins of the XMRV retrovirus implicated in chronic fatigue syndrome and prostate cancer are homologous to human proteins relevant to both diseases.

The XMRV retrovirus has been implicated in chronic fatigue syndrome and prostate cancer. A homology search comparing retroviral with human proteins revealed short contiguous amino acid strings (typically 5-8 aa) matching human proteins whose dysfunction might be expected to cause fatigue, including mitochondrial proteins related to oxidative phosphorylation, glutamate receptors and their synaptic scaffolds, muscular acetylcholine receptor scaffolds and structural proteins, components of the immune system, and phosphatidylinositol signalling inter alia. Viral proteins are also homologous to members of the oestrogen, peroxisome proliferator, and CREB activated receptor networks, all of which are implicated in prostate cancer, and to a protein, SRCAP, that controls the expression of the prostate-specific antigen. These short matches are often predicted to be antigenic, and antibodies to XMRV proteins may target their human homologues. This is supported by the presence of autoantibodies to muscarinic receptors , vimentin and LAMINB1 (all XMRV homologues) in chronic fatigue syndrome sufferers. Homologous XMRV proteins might also interfere with the protein interactomes of their human homologues. Viral mimicry of human proteins is extensive and often relevant to disease. For example Epstein-Barr viral proteins aligns with multiple sclerosis autoantigens, while HIV-1 proteins align with several components of the immune system. Mutant proteins in Huntington's disease and cystic fibrosis also align with proteins from common phages or viruses. This suggests a common theme of viral derived autoimmunity/network interference in many human disorders, which could radically change the shape of future therapy. Such viral mimicry likely relates to the idea that life evolved from viruses, leaving behind a legacy of viral derived human proteins whose homology to the current virome may be responsible for many human diseases and syndromes. Vaccination programmes or immunosuppression may be beneficial in many of these conditions

Hierarchical Models for Relational Event Sequences

Interaction within small groups can often be represented as a sequence of events, where each event involves a sender and a recipient. Recent methods for modeling network data in continuous time model the rate at which individuals interact conditioned on the previous history of events as well as actor covariates. We present a hierarchical extension for modeling multiple such sequences, facilitating inferences about event-level dynamics and their variation across sequences. The hierarchical approach allows one to share information across sequences in a principled manner---we illustrate the efficacy of such sharing through a set of prediction experiments. After discussing methods for adequacy checking and model selection for this class of models, the method is illustrated with an analysis of high school classroom dynamics

Robust Targeting for the Smartphone Video Guidance Sensor

The Smartphone Video Guidance Sensor (SVGS) is a miniature, self-contained autonomous rendezvous and docking sensor developed using a commercial off the shelf Android-based smartphone. It aims to provide a miniaturized solution for rendezvous and docking, enabling small satellites to conduct proximity operations and formation flying while minimizing interference with a primary payload. Previously, the sensor was limited by a slow (2 Hz) refresh rate and its use of retro-reflectors, both of which contributed to a limited operating environment. To advance the technology readiness level, a modified approach was developed, combining a multi-colored LED target with a focused target-detection algorithm. Alone, the use of an LED system was determined to be much more reliable, though slower, than the retro-reflector system. The focused target-detection system was developed in response to this problem to mitigate the speed reduction of using color. However, it also improved the reliability. In combination these two methods have been demonstrated to dramatically increase sensor speed and allow the sensor to select the target even with significant noise interfering with the sensor, providing millimeter level accuracy at a range of two meters with a 1U target