Martin boundary of a killed random walk on a quadrant

A complete representation of the Martin boundary of killed random walks on the quadrant ${\mathbb{N}}^*\times{\mathbb{N}}^*$ is obtained. It is proved that the corresponding full Martin compactification of the quadrant ${\mathbb{N}}^*\times{\mathbb{N}}^*$ is homeomorphic to the closure of the set $\{w={z}/{(1+|z|)}:z\in{\mathbb{N}}^*\times{\mathbb{N}}^*\}$ in ${\mathbb{R}}^2$. The method is based on a ratio limit theorem for local processes and large deviation techniques.Comment: Published in at http://dx.doi.org/10.1214/09-AOP506 the Annals of Probability (http://www.imstat.org/aop/) by the Institute of Mathematical Statistics (http://www.imstat.org

The Efficacy of Paroxetine and Placebo in Treating Anxiety and Depression: A Meta-Analysis of Change on the Hamilton Rating Scales

Background: Previous meta-analyses of published and unpublished trials indicate that antidepressants provide modest benefits compared to placebo in the treatment of depression; some have argued that these benefits are not clinically significant. However, these meta-analyses were based only on trials submitted for the initial FDA approval of the medication and were limited to those aimed at treating depression. Here, for the first time, we assess the efficacy of a selective serotonin reuptake inhibitor (SSRI) in the treatment of both anxiety and depression, using a complete data set of all published and unpublished trials sponsored by the manufacturer. Methods and Findings: GlaxoSmithKline has been required to post the results for all sponsored clinical trials online, providing an opportunity to assess the efficacy of an SSRI (paroxetine) with a complete data set of all trials conducted. We examined the data from all placebo-controlled, double-blind trials of paroxetine that included change scores on the Hamilton Rating Scale for Anxiety (HRSA) and/or the Hamilton Rating Scale for Depression (HRSD). For the treatment of anxiety (k = 12), the efficacy difference between paroxetine and placebo was modest (d = 0.27), and independent of baseline severity of anxiety. Overall change in placebo-treated individuals replicated 79% of the magnitude of paroxetine response. Efficacy was superior for the treatment of panic disorder (d = 0.36) than for generalized anxiety disorder (d = 0.20). Published trials showed significantly larger drug-placebo differences than unpublished trials (d’s = 0.32 and 0.17, respectively). In depression trials (k = 27), the benefit of paroxetine over placebo was consistent with previous meta-analyses of antidepressant efficacy (d = 0.32). Conclusions: The available empirical evidence indicates that paroxetine provides only a modest advantage over placebo in treatment of anxiety and depression. Treatment implications are discussed

The geography of British exports: country-level versus firm-level evidence

This study investigates the degree of regionalization of UK exporters. The firm-level findings, based on an original set of primary data of 356 UK exporters, are contrasted with the UK national trade flows as well as with the geographic spread of the UK, European and the world's largest MNEs. The analysis produced consistent findings of regionalization regardless of the classification thresholds or sales matrices employed. The findings also imply that country-level data supports the firm-level findings of regionalization. White the analysis presents relatively strong corroborating evidence of regionalization of UK exports, it also indicates that UK exporters might be more multi-regional and global oriented than previously thought. (C) 2009 Elsevier Ltd. ALL rights reserved

Correlation Study Regarding Professional Development and Technology Integration in K-12 Twenty-First Century Classrooms

The purpose of this correlation study is to test the relationship between the amount and type of technology used in the classroom, and the educators receiving local professional development on how to integrate technology in the classroom. The research design for this study is a relationship correlation study. Bivariate correlational statistics were used to determine if there was a positive correlation between the co-variable; the school district\u27s data from the administrator\u27s observation of technology integration, and the predictor variable; the local professional development on technology. The Pearson\u27s r design was chosen as the technique used for measuring this correlation study since the variables are continuous, and the software program statistical package for the social sciences (SPSS) was used to analyze the data (Gall, Gall, & Borg, 2010; Gay, Mills, & Airasian, 2006). The participants for this study are both the educators and students who make up a suburban school district in the state of Georgia. The sample size for this study is the 9,147 classroom observations reported over the course of two years from the 32 schools in the district. The results of this correlation study showed that there was no significant correlation between the integration of technology in the classroom and the local school district\u27s professional development given through the technology summit

Modeling energy consumption in the mining and milling of uranium

textA family of top-down statistical models describing energy consumption in the mining, milling, and refining of uranium are formulated. The purpose of the models is to estimate the energy-to-grade dependence for uranium extraction, while defining a minimum grade that can be feasibly mined and produced. The results serve as a basis for understanding the factors governing energy consumption in the production of U3O8. The models are applied to a considerably larger data set of operating mines than in any previous effort. In addition, the validity of the modeling approach is established by modeling energy for two other commodities, gold and copper, thereby showing it can be applied to other metals. Statistical measures of explanatory power show that the models the energy-to-grade relationship is well-described for both uranium and gold. For copper, there was insufficient data over a broad range of ore grades to obtain a model that passed statistical confidence measures. The results show that mining of lower-grade deposits of uranium is likely to be less energy-intensive than previous investigators concluded. It is shown that the uncertainty in the results is dominated by the contribution of the grade-independent component of energy consumption.Mechanical Engineerin

A Case Study of an Office of Disability Support Services in Higher Education for Students with Autism Spectrum Disorder

The purpose of this qualitative case study is to identify the factors that impact learners with autism spectrum disorder (ASD) at a university in central Virginia. The theory guiding this study is disability theory as it seeks to explain the limitations placed on persons with disabilities. The central research question is: What factors of the disability support services impact learning in university students with ASD? The subquestions include: (a) How do students with ASD describe their experiences with the university’s disability support service offices? (b) How do university faculty describe their role in supporting students with ASD? (c) What factors of the disability support service offices are perceived by students and faculty as having a positive impact on student learning? (d) What factors of the disability support service offices are perceived by students and faculty as lacking or ineffective? This single case study included six student participants with autism spectrum disorder and four disability support services office faculty members from the university. Data was collected via individual interviews, an online focus group, and documents/archival records. Data analysis consisted of categorical aggregation, development of naturalistic generalizations, and development of themes

Post-Deployment Key Management in Heterogeneous Wireless Sensor Networks

Many wireless sensor network applications require secure communication between nodes in the network. However, establishing pair-wise keys between nodes to provide security is challenging due to the limited resources in sensor nodes and the hostile environments in which they are deployed. Many key establishment schemes have been previously proposed for wireless sensor networks. However, most of these schemes were designed to work in a homogeneous network environment in which the nodes all have similar capabilities. Our work establishes that better performance can be achieved in a heterogeneous sensor network environment. We present a key management scheme for establishing pair-wise keys after deployment in a heterogeneous wireless sensor network. We take advantage of the more powerful nodes present in a heterogeneous network to reduce the communication overhead and ultimately the power consumption necessary to perform these services to the network. Additionally, by taking advantage of these nodes we are able to increase the overall network connectivity and resiliency against node capture attacks