Explaining Cost Efficiency of Scottish Farms: A Stochastic Frontier Analysis

In this paper the cost efficiency of Scottish farms is determined, variables that explain the relative cost efficiency by farm type are identified and implications discussed. A cost efficiency approach was selected as it can deal with farms producing multiple outputs (in contrast to production frontiers), and second because it can accommodate output constraints imposed by the Common Agricultural Policy (CAP). To estimate the stochastic cost frontier, a generalised multi-product translog cost function was estimated for five farm types: dairy, cereals and general cropping, cattle and sheep, specialist sheep and mixed farms. Eight farm outputs and four inputs were considered. The data for the estimation were drawn from the Farm Accounts Scheme (FAS) survey for the period 1997-2004, which allowed the construction of an unbalanced panel dataset for 358 farms. Cost efficiency was measured as a fixed effect term and this was used to construct an indicator of relative cost efficiency by farm type. Further analysis, to explain the efficiency results, indicated the presence of important farm size and regional effects. However, other variables used in the analysis, whilst statistically significant, did not produce a consistent effect across the different farm types.Stochastic cost frontier analysis, cost efficiency, Scottish farms, Common Agricultural Policy., Productivity Analysis, Farm Management,

Efficiency of Scottish Farms: A Stochastic Cost Frontier Analysis

In this paper the relative cost efficiency of Scottish farms is determined, and variables that explain this efficiency by farm type are identified and implications discussed. A panel dataset from the Farm Accounts Scheme (FAS) survey for the period 1997-2004 was used for the estimation. A cost efficiency indicator was measured using a fixed effect panel data regression. Further analysis, to explain the efficiency results, indicated the presence of important farm size and regional effects. However, other variables, whilst statistically significant, did not produce a consistent effect across the different farm types.Stochastic cost frontier analysis, cost efficiency, Scottish farms, Common Agricultural Policy, Farm Management, Q12,

Physiological and Pathophysiological Implications of Synaptic Tau

Tauopathies encompass a broad range of neurodegenerative diseases featuring extensive neuronal death and cognitive decline. However, research over the past 30 years has failed to significantly advance our understanding of how tau causes dementia, limiting the design of rational therapeutics. It has become evident that we need to expand our understanding of tau in physiology, in order to delineate how tau may contribute to pathology. This review discusses recent evidence that has uncovered a novel aspect of tau function, based on its previously uncharacterized localization to the synapse. Here, multiple streams of evidence support a critical role for synaptic tau in the regulation of synapse physiology. In particular, long-term depression, a form of synaptic weakening, is dependent on the presence of tau in hippocampal neurons. The regulation of tau by specific phosphorylation events downstream of GSK-3β activation appears to be integral to this signaling role. We also describe how the regulation of synapse physiology by tau and its phosphorylation may inform our understanding of tauopathies and comorbid diseases. This work should provide a platform for future tau biology research in addition to therapeutic design.</jats:p

On the interaction of Jupiter's Great Red Spot and zonal jet streams

In this paper, Jupiter's Great Red Spot (GRS) is used to determine properties of the Jovian atmosphere that cannot otherwise be found. These properties include the potential vorticity of the GRS and its neighboring jet streams, the shear imposed on the GRS by the jet streams, and the vertical entropy gradient (i.e., Rossby deformation radius). The cloud cover of the GRS, which is often used to define the GRS's area and aspect ratio, is found to differ significantly from the region of the GRS's potential vorticity anomaly. The westward-going jet stream to the north of the GRS and the eastward-going jet stream to its south are each found to have a large potential vorticity ``jump''. The jumps have opposite sign and as a consequence of their interaction with the GRS, the shear imposed on the GRS is reduced. The east-west to north-south aspect ratio of the GRS's potential vorticity anomaly depends on the ratio of the imposed shear to the strength of the anomaly. The aspect ratio is found to be $\approx$2:1, but without the opposing jumps it would be much greater. The GRS's high-speed collar and quiescent interior require that the potential vorticity in the interior be approximately half that in the collar. No other persistent geophysical vortex has a significant minimum of potential vorticity in its interior and laboratory vortices with such a minimum are unstable.Comment: Manuscript accepted to Journal of the Atmospheric Sciences, March 2007. v2: minor stylistic changes (after journal proof reading

Reconceiving Our Community: A Cosmopolitan Case for Open Borders

In this thesis I present a cosmopolitan case for open borders. First, I examine the U.S. border policy of the last several decades and challenge its cost-effectiveness and impact on undocumented immigrants. Then I tackle the undergirding assumption of the U.S. border policy, namely, that the political state is morally entitled to control its borders, by examining the most prominent argument on either side of the debate. In light of this discussion, I challenge the legitimacy of the undergirding nation-state system in our world and argue for a more global conception of community and world-order through the cosmopolitan accounts of the ancient Stoics, Immanuel Kant, and Jürgen Habermas

Leveraging Subject Matter Expertise to Optimize Machine Learning Techniques for Air and Space Applications

We develop new machine learning and statistical methods that are tailored for Air and Space applications through the incorporation of subject matter expertise. In particular, we focus on three separate research thrusts that each represents a different type of subject matter knowledge, modeling approach, and application. In our first thrust, we incorporate knowledge of natural phenomena to design a neural network algorithm for localizing point defects in transmission electron microscopy (TEM) images of crystalline materials. In our second research thrust, we use Bayesian feature selection and regression to analyze the relationship between fighter pilot attributes and flight mishap rates. We use the Bayesian approach to incorporate findings from prior qualitative studies on flight mishaps. In our last research thrust, we utilize data generated from Air Force evaluation processes. We use structural causal models to represent our knowledge of Air Force evaluation processes and present a framework for using regression to identify and estimate causal relationships

Modelling Spatially Regulated β-Catenin Dynamics and Invasion in Intestinal Crypts

AbstractExperimental data (e.g., genetic lineage and cell population studies) on intestinal crypts reveal that regulatory features of crypt behavior, such as control via morphogen gradients, are remarkably well conserved among numerous organisms (e.g., from mouse and rat to human) and throughout the different regions of the small and large intestines. In this article, we construct a partial differential equation model of a single colonic crypt that describes the spatial distribution of Wnt pathway proteins along the crypt axis. The novelty of our continuum model is that it is based upon assumptions that can be directly related to processes at the cellular and subcellular scales. We use the model to predict how the distributions of Wnt pathway proteins are affected by mutations. The model is then extended to investigate how mutant cell populations can invade neighboring crypts. The model simulations suggest that cell crowding caused by increased proliferation and decreased cell loss may be sufficient for a mutant cell population to colonize a neighboring healthy crypt

Anyone Can Become a Troll: Causes of Trolling Behavior in Online Discussions

In online communities, antisocial behavior such as trolling disrupts constructive discussion. While prior work suggests that trolling behavior is confined to a vocal and antisocial minority, we demonstrate that ordinary people can engage in such behavior as well. We propose two primary trigger mechanisms: the individual's mood, and the surrounding context of a discussion (e.g., exposure to prior trolling behavior). Through an experiment simulating an online discussion, we find that both negative mood and seeing troll posts by others significantly increases the probability of a user trolling, and together double this probability. To support and extend these results, we study how these same mechanisms play out in the wild via a data-driven, longitudinal analysis of a large online news discussion community. This analysis reveals temporal mood effects, and explores long range patterns of repeated exposure to trolling. A predictive model of trolling behavior shows that mood and discussion context together can explain trolling behavior better than an individual's history of trolling. These results combine to suggest that ordinary people can, under the right circumstances, behave like trolls.Comment: Best Paper Award at CSCW 201

Cyclin Y inhibits plasticity-induced AMPA receptor exocytosis and LTP

Cyclin Y (CCNY) is a member of the cyclin protein family, known to regulate cell division in proliferating cells. Interestingly, CCNY is expressed in neurons that do not undergo cell division. Here, we report that CCNY negatively regulates long-term potentiation (LTP) of synaptic strength through inhibition of AMPA receptor trafficking. CCNY is enriched in postsynaptic fractions from rat forebrain and is localized adjacent to postsynaptic sites in dendritic spines in rat hippocampal neurons. Using live-cell imaging of a pH-sensitive AMPA receptor, we found that during LTP-inducing stimulation, CCNY inhibits AMPA receptor exocytosis in dendritic spines. Furthermore, CCNY abolishes LTP in hippocampal slices. Taken together, our findings demonstrate that CCNY inhibits plasticity-induced AMPA receptor delivery to synapses and thereby blocks LTP, identifying a novel function for CCNY in post-mitotic cells