The effects of intense fire on headwater streams of the Colville National Forest, WA

Thesis (M.S.) University of Alaska Fairbanks, 2006Forest fires play an important role in shaping ecosystems, and there has been growing concern on the effects of high intensity fires on forest and aquatic ecosystems. Headwater streams are highly connected to riparian and surrounding terrestrial systems, and to downstream aquatic systems, partly through prey and organic matter transfers via aquatic invertebrate drift and emergence. Because of their small size, headwater streams may experience the greatest initial impact from forest fire, but may also return to pre-fire conditions quicker than larger streams. In this study, headwater streams from replicated burned and control watersheds were sampled in the two years following an intense forest fire in northeastern Washington. Benthic, drift and emergence samples of aquatic invertebrates were taken and analyzed for differences in density, biomass and community composition between watershed types. There was significantly higher density of invertebrates in burned sites, but no difference in biomass except in invertebrate emergence which was greater at burned sites. There was lower diversity in the burned watersheds, and the invertebrate community was dominated by chironomids. These changes in invertebrate density and community composition could influence the food resources available to aquatic and riparian consumers

B States at the Tevatron

The CDF and D0 experiments have produced a wealth of heavy flavour physics results since the beginning of Run II of the Fermilab Tevatron. We review recent measurements of B hadron states including excited B states (B^{**}, B_s^{**}) and the Bc+ meson. We also summarize the discoveries of the Sigma_b baryon states and the Xi_b baryon.Comment: Contribution to proceedings of Heavy Quarks and Leptons, Melbourne, 2008. 6 pages with 6 figures and 1 tabl

Chemistry

published or submitted for publicatio

Physics of B0s Mesons and Bottom Baryons

We discuss the physics of B0s mesons focusing on CP violation in B0s -> J/Psi Phi decays at the Tevatron. We summarize measurements of the properties of bottom baryons at the Tevatron including the Sigma_b states and the Xi_b baryon. We also discuss the discovery of the Omega_b baryon.Comment: Contribution to proceedings of CIPANP 2009 conference, La Jolla, May 2009. 4 pages with 2 figure

A small population of hypothalamic neurons govern fertility: the critical role of VAX1 in GnRH neuron development and fertility maintenance.

Fertility depends on the correct maturation and function of approximately 800 gonadotropin-releasing hormone (GnRH) neurons in the brain. GnRH neurons are at the apex of the hypothalamic-pituitary-gonadal axis that regulates fertility. In adulthood, GnRH neurons are scattered throughout the anterior hypothalamic area and project to the median eminence, where GnRH is released into the portal vasculature to stimulate release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary. LH and FSH then regulate gonadal steroidogenesis and gametogenesis. Absence of GnRH neurons or inappropriate GnRH release leads to infertility. Despite the critical role of GnRH neurons in fertility, we still have a limited understanding of the genes responsible for proper GnRH neuron development and function in adulthood. GnRH neurons originate in the olfactory placode then migrate into the brain. Homeodomain transcription factors expressed within GnRH neurons or along their migratory path are candidate genes for inherited infertility. Using a combined in vitro and in vivo approach, we have identified Ventral Anterior Homeobox 1 (Vax1) as a novel homeodomain transcription factor responsible for GnRH neuron maturation and fertility. GnRH neuron counts in Vax1 knock-out embryos revealed Vax1 to be required for the presence of GnRH-expressing cells at embryonic day 17.5 (E17.5), but not at E13.5. To localize the effects of Vax1 on fertility, we generated Vax1flox mice and crossed them with Gnrhcre mice to specifically delete Vax1 within GnRH neurons. GnRH staining in Vax1flox/flox:GnRHcre mice show a total absence of GnRH expression in the adult. We performed lineage tracing in Vax1flox/flox:GnRHcre:RosaLacZ mice which proved GnRH neurons to be alive, but incapable of expressing GnRH. The absence of GnRH leads to delayed puberty, hypogonadism and complete infertility in both sexes. Finally, using the immortalized model GnRH neuron cell lines, GN11 and GT1-7, we show that VAX1 is a direct regulator of Gnrh1 transcription by binding key ATTA sites within the Gnrh1 promoter. This study identifies VAX1 as a key transcription factor regulating GnRH expression and establishes VAX1 as a novel candidate gene implicated in heritable infertility

Undermining and Strengthening Social Networks through Network Modification

Social networks have well documented effects at the individual and aggregate level. Consequently it is often useful to understand how an attempt to influence a network will change its structure and consequently achieve other goals. We develop a framework for network modification that allows for arbitrary objective functions, types of modification (e.g. edge weight addition, edge weight removal, node removal, and covariate value change), and recovery mechanisms (i.e. how a network responds to interventions). The framework outlined in this paper helps both to situate the existing work on network interventions but also opens up many new possibilities for intervening in networks. In particular use two case studies to highlight the potential impact of empirically calibrating the objective function and network recovery mechanisms as well as showing how interventions beyond node removal can be optimised. First, we simulate an optimal removal of nodes from the Noordin terrorist network in order to reduce the expected number of attacks (based on empirically predicting the terrorist collaboration network from multiple types of network ties). Second, we simulate optimally strengthening ties within entrepreneurial ecosystems in six developing countries. In both cases we estimate ERGM models to simulate how a network will endogenously evolve after intervention

Neuroscience-informed Auditory Training in Schizophrenia: A Final Report of the Effects on Cognition and Serum Brain-Derived Neurotrophic Factor.

ObjectiveWe previously reported the interim effects in a per protocol analysis of a randomized controlled trial of an innovative neuroscience-informed computerized cognitive training approach in schizophrenia. Here we report the effects of training on behavioral outcome measures in our final sample using an intent-to-treat analysis. We also report the effects on serum brain-derived neurotrophic factor (BDNF).MethodEighty-seven clinically stable participants with schizophrenia were randomly assigned to either targeted auditory training (AT, N=46) or a computer games control condition (CG, N=41). Participants were assessed on neurocognition, symptoms and functional outcome at baseline and after 50 hours of intervention delivered over 10 weeks. Serum BDNF was assessed at baseline, at 2 weeks, and at 10 weeks.ResultsAfter the intervention, AT participants showed significant gains in global cognition, speed of processing, verbal learning, and verbal memory, relative to CG participants, with no changes in symptoms or functioning. At baseline, schizophrenia participants had significantly lower-than-normal serum BDNF. AT participants showed a significant increase in serum BDNF compared to CG participants, and "normalized" levels by post training.ConclusionsParticipants with chronic schizophrenia made significant cognitive gains after 50 hours of intensive computerized training delivered as a stand-alone treatment, but no improvement in symptoms or functioning. Serum BDNF levels were significantly increased, and may serve as a peripheral biomarker for the effects of training. Future research must focus on: 1) Methods of integrating cognitive training with psychosocial treatments; 2) A deeper understanding of underlying neurophysiology in order to enhance critical mechanisms of action

Interest-Based Self-Organizing Peer-to-Peer Networks: A Club Economics Approach

Improving the information retrieval (IR) performance of peer-to-peer networks is an important and challenging problem. Recently, the computer science literature has attempted to address this problem by improving IR search algorithms. However, in peer-to-peer networks, IR performance is determined by both technology and user behavior, and very little attention has been paid in the literature to improving IR performance through incentives to change user behavior. We address this gap by combining the club goods economics literature and the IR literature to propose a next generation file sharing architecture. Using the popular Gnutella 0.6 architecture as context, we conceptualize a Gnutella ultrapeer and its local network of leaf nodes as a "club" (in economic terms). We specify an information retrieval-based utility model for a peer to determine which clubs to join, for a club to manage its membership, and for a club to determine to which other clubs they should connect. We simulate the performance of our model using a unique real-world dataset collected from the Gnutella 0.6 network. These simulations show that our club model accomplishes both performance goals. First, peers are self-organized into communities of interest - in our club model peers are 85% more likely to be able to obtain content from their local club than they are in the current Gnutella 0.6 architecture. Second, peers have increased incentives to share content - our model shows that peers who share can increase their recall performance by nearly five times over the performance offered to free-riders. We also show that the benefits provided by our club model outweigh the added protocol overhead imposed on the network for the most valuable peers

Cell Phone Demand and Consumer Learning - An Empirical Analysis

A structural model is used in this paper to analyze the demand and learning behavior in cell phone market. We assume that the cell phone consumption can be divided into a high-value part and a low-value part. The consumers are assumed to be uncertain about the exogenous shock of the need for high-value usage and also their preferences over the low-value usage. Meanwhile, we assume that the consumers' knowledge improves over time. As a result, the match between their plan choice and consumption pattern becomes better. Such a learning behavior is supported by the data set. Bayesian updating is used to represent the learning. The estimates of the parameters are obtained and compared to the benchmarks from previous research

Co-evolution, sustainable tourism and protected areas

This paper explores the concept of co-evolution and its role in achieving a greater understanding of sustainable tourism in the context of protected areas. Adopting a co-evolutionary perspective has potential to be a fertile ground for studying governance and policy of Sustainable Development. In the context of protected areas where social and ecological systems run parallel with each other, and where Sustainable Development has become a key objective, co-evolutionary development may be expected. Therefore, this exploration of sustainable tourism policy and governance in a protected area through a co-evolutionary lens uncovers a wide range of linkages and relationships to other policies, internal and external influences and the protected area’s historical context. The paper reveals how sustainable tourism policies in the Lake District National Park, England, developed incrementally and gradually over a period of 20 years and were often reformulated and reframed during this time scale. Similarly, the paper also discusses findings from research within the Peak District National Park Authority, England which reveal how drivers for sustainable tourism increased greater partnership working and how policies for sustainable development and sustainable tourism “co-evolved” during the studied period. The paper draws attention to the value of adopting a co-evolutionary approach to sustainable tourism research, particularly if institutions are operating in an environment where the ability to learn and understand the complexity of sustainable tourism and can contribute to their wider goals of Sustainable Development