A Multi-Scale Analysis of the Effects of Local- and Landscape-Level Variables on Nuthatch Occupancy and Distribution

The objectives of this study are to conduct a multi-scale analysis of the effects of habitat variables on Brownheaded Nuthatch (S. pusilla) occupancy and spatial distribution in the greater Greenville area of South Carolina. By understanding the local- and landscape-drivers of an ecologically sensitive species, we can build a predictive model of species occurrence and contribute to regional conservation efforts of both habitat and biodiversity

Theory of surface modes in structured plasmonic arrays

Metamaterials can provide many different functionalities and striking optical properties, whereby the optical control often comes from metallic building blocks which exhibit plasmonic resonances in the optical and infra-red frequency regimes. However, one of the major obstacles in the use of metallic elements is the overcoming of the losses in plasmonic structures. In this thesis, we consider how mode hybridisation can be used to circumvent these losses using cut-wire plasmonic arrays coupled to photonic slab waveguides. The resulting hybrid modes can have low loss characteristics and we investigate how the geometric parameters of the structure can be used to control the transmission and dispersion properties. We then investigate finite arrays finding they can support modes with extremely high quality factors (Q∼ 4000), which is highly unusual in plasmonic systems, and that the individual loss mechanisms can be controlled via the geometry. In the second part of the thesis we consider another type of surface mode, the spoof SPP. Theoretical methods for describing spoof SPPs in perfectly conducting materials are well established, enabling the design of an arbitrary spoof plasma frequency. However, for dispersive materials there have been a lack of theoretical studies. We begin by considering first how small changes to the spoof plasmon geometry affect the characteristics of spoof SPP waves, adapting the coupled mode method to slanted geometries and even right-angled triangular indentations, a structure not normally associated with spoof SPPs. We then develop a formalism based on the coupled mode method allowing the dispersion of real metal spoof SPPs to be understood and tuned, thus enabling control of the optical spoof SPP characteristics via both the geometry and the incorporated materials. This method also enables an in depth look at the modal losses which occur once dispersive materials are incorporated into the spoof plasmon dispersion relation and vary drasticallywith the groove width.Open Acces

Stephen Parker. Bertolt Brecht: A Literary Life. London: Bloomsbury, 2014. x + 704 pp.

Review of Stephen Parker. Bertolt Brecht: A Literary Life. London: Bloomsbury, 2014. x + 704 pp

The Contribution of Private Forestland Management and Monitoring to Avian Conservation in Pine Systems in South Carolina

Land-use activities and changes to ecosystems pervasively threaten biodiversity. The United States Department of Agriculture (USDA) Farm Bill allocates financial and technical resources to meet the need for agricultural and timber production while also conserving natural resources. On private forestlands in South Carolina, management practices (prescribed burning, thinning, herbicide application) are employed to improve upland pine habitat for wildlife and are reimbursable through Farm Bill cost-share programs. Some regional priority bird species have habitat requirements dependent on forestry management, so data are needed on how common management activities affect bird communities. I studied managed loblolly pine systems in the South Carolina Piedmont region to understand how forestry management practices influence wildlife habitat at local and landscape levels. I used traditional point counts and autonomous recording units (ARUs) to survey birds on 53 private forestland sites. In Chapter 2, I discuss the effects of management on pine stand characteristics, on overall species diversity, and on abundance of particular guilds and species. Repeated burning and thinning shifted stand conditions to open pine woodlands with herbaceous understories and supported higher species diversity. Some guilds and species responded positively to active management, but many relationships were subtler and varied by life history. In Chapter 3, I address the need for widespread, effective monitoring to gauge responses of wildlife to private land management. I evaluate ARUs as an efficient tool for collecting presence/absence data to characterize diversity on private lands when resources are limited. Although I detected similar lists of species with individual point counts as with individual acoustic surveys, I detected more species across all visits and seasons with the point count method. ARUs are reliable sampling tools for spatial and temporal replication but come with processing challenges. I found rich avian communities on working timber lands, supporting the idea that private lands contribute to wildlife conservation in South Carolina. I showed that one strategy for private land conservation, voluntary Farm Bill habitat incentive programs, can improve regional resources for wildlife. Finally, effective monitoring methods must be used to help conservation practitioners and land managers track the benefits of these programs to wildlife communities

Cohomogeneity-One Lagrangian Mean Curvature Flow

We study mean curvature flow of Lagrangians in $\mathbb{C}^n$ that are cohomogeneity-one under a compact Lie group $G \leq \mathrm{SU}(n)$ acting linearly on $\mathbb{C}^n$. Each such Lagrangian necessarily lies in a level set $\mu^{-1}(\xi)$ of the standard moment map $\mu : \mathbb{C}^n \to \mathfrak{g}^*$, and mean curvature flow preserves this containment. We classify all cohomogeneity-one self-similarly shrinking, expanding and translating solutions to the flow, as well as cohomogeneity-one smooth special Lagrangians lying in $\mu^{-1}(0)$. Restricting to the case of almost-calibrated flows in the zero level set $\mu^{-1}(0)$, we classify finite-time singularities, explicitly describing the Type I and Type II blowup models. Finally, given any cohomogeneity-one special Lagrangian submanifold in $\mu^{-1}(0)$, we show it occurs as the Type II blowup model of a Lagrangian MCF singularity, thereby providing infinitely many previously unobserved singularity models. Throughout, we give explicit examples of suitable group actions, including a complete list in the case of $G$ simple.Comment: 53 pages, 3 figure

Application of a coupled human natural system framework to organize and frame challenges and opportunities for biodiversity conservation on private lands

Conservation science addresses the complementary goals of preventing future biodiversity loss while sustaining critical human foundations. In this paper we use two case studies focused on land management to discuss how private lands conservation can be more effective by considering how planning and decision making reflects a coupled human and natural system (CHANS). The first case study focuses on conservation easements in the temperate forests of eastern United States; the second focuses on conservation opportunities in Midwestern agroecosystems, in particular the value of agroforestry. For each case study we discuss the natural and human subsystems, how elements and interactions within and between subsystems (as organized by elements of CHANS) create challenges and opportunities for conservation, and the importance of considering relevant scales of subsystems. Review of these case studies demonstrates that additional insight gained by using a CHANS perspective, particularly given how the subsystems interact at different scales, improves identification of important points of social and ecological overlap, ultimately enhancing conservation research, planning, and practice

Ventral Tegmental Area Neuronal Ensembles Accurately Encode Action Number

Real-time updates to behavioral strategy require animals to understand how many actions have been executed toward completion of a goal. These operations are essential for optimizing behavior and have been linked to dopaminergic innervation of prefrontal cortex networks (Gallistel and Gibbon, 2000; Allman et al., 2011; Lustig, 2011). It is an open question how networks of dopaminergic and non-dopaminergic neurons in the ventral tegmental area (VTA) encode information when multiple or complex behaviors are required to earn rewards (Niv et al., 2006; Dayan and Niv, 2008; Niv and Schoenbaum, 2008). Most electrophysiological studies have focused on the averaged activity of dopamine neurons during reward prediction error signaling in simple behavioral paradigms. Thus, VTA neuronal correlates of executive processes and complex behavior remain elusive. In the current experiment, rats learned to repetitively execute actions (nose pokes) to receive rewarding outcomes (sugar pellets). These actions were randomly rewarded, and all actions were identically valued because each was equally likely to be reinforced. Actions differed only by their number within a trial. While animals executed serial actions, many VTA neurons were activated or suppressed by unique subsets of actions within a trial. Some neurons fired preferentially during low numbered actions while others preferred high numbered actions. A population averaging approach, which is conventionally used for analysis of dopaminergic neuronal activity, offered poor decoding of action number. In contrast, action number within a trial was accurately decoded from the entire pool of unique activity patterns, considering each neuron independently. These results suggest that the collective activity of VTA neuronal ensembles signals real-time information about ongoing action number—a critical component of behavioral organization

Deacylated tRNA Accumulation Is a Trigger for Bacterial Antibiotic Persistence Independent of the Stringent Response

Bacterial antibiotic persistence occurs when bacteria are treated with an antibiotic and the majority of the population rapidly dies off, but a small subpopulation enters into a dormant, persistent state and evades death. Diverse pathways leading to nucleoside triphosphate (NTP) depletion and restricted translation have been implicated in persistence, suggesting alternative redundant routes may exist to initiate persister formation. To investigate the molecular mechanism of one such pathway, functional variants of an essential component of translation (phenylalanyltRNA synthetase [PheRS]) were used to study the effects of quality control on antibiotic persistence. Upon amino acid limitation, elevated PheRS quality control led to significant decreases in aminoacylated tRNAPhe accumulation and increased antibiotic persistence. This increase in antibiotic persistence was most pronounced (65-fold higher) when the relA-encoded tRNA-dependent stringent response was inactivated. The increase in persistence with elevated quality control correlated with ;2-fold increases in the levels of the RNase MazF and the NTPase MazG and a 3-fold reduction in cellular NTP pools. These data reveal a mechanism for persister formation independent of the stringent response where reduced translation capacity, as indicated by reduced levels of aminoacylated tRNA, is accompanied by active reduction of cellular NTP pools which in turn triggers antibiotic persistence. IMPORTANCE Bacterial antibiotic persistence is a transient physiological state wherein cells become dormant and thereby evade being killed by antibiotics. Once the antibiotic is removed, bacterial persisters are able to resuscitate and repopulate. It is thought that antibiotic bacterial persisters may cause reoccurring infections in the clinical setting. The molecular triggers and pathways that cause bacteria to enter into the persister state are not fully understood. Our results suggest that accumulation of deacylated tRNA is a trigger for antibiotic persistence independent of the RelA-dependent stringent response, a pathway thought to be required for persistence in many organisms. Overall, this provides a mechanism where changes in translation quality control in response to physiological cues can directly modulate bacterial persistence

Using \u27big data\u27 to explain visits to lakes in 17 US states

We use large dataset on US lakes from 17 states to estimate the relationship between summertime visits to lakes as proxied by social media use and the lakes\u27 water quality, amenities, and surrounding landscape features and socioeconomic conditions. Prior to estimating these relationships we worked on 1) selecting a parsimonious set of explanatory variables from a roster of more than 100 lake attributes and 2) accounting for the non-random pattern of missing water quality data. These steps 1) improved the interpretability of the estimated visit models and 2) widened our estimated models\u27 scope of statistical inference. We used Machine Learning techniques to select parsimonious sets of explanatory variables and multiple imputation to estimate water quality at lakes missing this data. We found the following relationships between summertime visits to lake and their attributes across the 17-state region. First, we estimated that every additional meter of average summer-time Secchi depth between 1995 and 2014 was associated with at least 7.0% more summer-time visits to a lake between 2005 to 2014, all else equal. Second, we consistently found that lake amenities, such as beaches, boat launches, and public toilets, were more powerful predictors of visits than water quality. Third, we also found that visits to a lake were strongly influenced by the lake\u27s accessibility and its distance to nearby lakes and the amenities the nearby lakes offered. Finally, our results highlight the biased results that big data -based research on recreation can generate if non-random missing observation patterns in the data are not corrected

Prospectus, January 28, 2009

https://spark.parkland.edu/prospectus_2009/1002/thumbnail.jp