Master of Science

thesisCu2ZnSnSe4 (CZTSe) possess highly suitable optical and electronic properties for use as an absorber layer in thin film solar cells. CZTSe also has potential to achieve terawatt level solar energy production due to its inexpensive and abundant material constituents. Currently, fabricating CZTSe devices with the expected theoretical performance has not been achieved, making the growth and formation of CZTSe an interesting topic of research. In this work, a two-step vacuum fabrication process consisting of RF co-sputtering followed by reactive annealing was explored as a viable technique for synthesizing CZTSe thin films. Furthermore, the enhancement of the fabrication process by the incorporation of sodium during annealing was studied using a combinatorial approach. Film composition was analyzed using electron dispersive spectroscopy. Structure, phase morphology, and formation were determined using scanning electron microscopy, x-ray diffraction, atomic force microscopy and raman spectroscopy. Optical and electronic properties were characterized using UV-Vis and Voc were measurements under a one sun solar simulator. RF co-sputtering CuSe, ZnSe, and SnSe precursors produced films with good thickness uniformity, adhesion and stoichiometry control over 3 x 3 in2 substrates. Composition measurements showed that the precursor films maintained stability during an annealing process of 580o C for 20 minutes producing near stoichiometric CZTSe. However, grain size was small with an average diameter of 350 nm. The CZTSe film produced by this process exhibited a suitable absorption coefficient of > 104 cm-1 and aband gap near 1.0 eV. The film also produced an XRD pattern consistent with tetragonal CZTSe with no secondary phase formation with the exception of approximately 12.5 nm of interfacial MoSe2 formation at the back contact. The combinatorial investigation of the influence of sodium on CZTSe growth and morphology was achieved using a custom built constant withdraw shutter to evaporate NaF with a 0-60 nm thickness spread on the substrate prior to precursor sputtering. This experiment showed that the incorporation of NaF did enhance grain size; however, there was little correlation with initial NaF composition observed. It is concluded that NaF undergoes high degree of vapor transport and readily distributes nonuniformly throughout the film during the annealing process and also potentially escapes the annealing environment if not properly contained. An experiment on achieving Na incorporation by diffusion from a soda lime glass substrate resulted in a far more uniform enhancement of grain growth. The experiment also revealed that NaF greatly reduced precursor film adhesion to the substrate due to the hygroscopic nature of NaF. X-ray diffraction measurements also showed that the addition of the NaF layer was could potentially suppress the formation of MoSe2

Timekeeping infrastructure for the Catalina Sky Survey

Time domain science forms an increasing fraction of astronomical programs at many facilities. Synoptic and targeted observing modes of transient, varying, and moving sources rely on precise clocks to provide the underlying time tags. Often precision is mistaken for accuracy, or the precise time signals never reach the instrumentation in the first place. We will discuss issues of deploying a stable high-precision GNSS clock on a remote mountaintop, and of conveying the resulting time signals to a computer in a way that permits hardware timestamping of the camera shutter (or equivalent) rather than the arbitrary delays encountered with non-real-time data acquisition software. Strengths and limitations of the Network Time Protocol will be reviewed. Timekeeping infrastructure deployed for the Catalina Sky Survey will serve as an example.Comment: 12 pages, SPIE proceedings, AS107-9

The James Carter Organ Trio

The organ combo reigned supreme for several decades as a meat-and-potatoes mainstay of 50\u27s and 60\u27s jazz. In the hands of saxophonist James Carter, one of jazz\u27s most sophisticated improvisers, the organ trio is elevated by Carter\u27s virtuosic chops, the band\u27s powerful blues-drenched style, and wide-ranging repertoire collected through the members\u27 far-flung musical explorations. Relying heavily on inspired group interplay, the trio features the nimble yet muscular keyboard work of Detroit\u27s rising B3 star Gerard Gibbs and the propulsive support of drummer Alex White.https://digitalcommons.kennesaw.edu/musicprograms/2158/thumbnail.jp

Profile-of-the-Local-Government-Workforce.pdf

An extensive profile of the Australian local government workforce. Supplements include a summary document of the key findings and an infographic

Manorial Officeholding in Late Medieval and Early Modern England, 1300-1600

This thesis investigates the role and identity of manorial officers, individuals drawn from a lord’s tenants who were vital in administering his manor court and directly-farmed lands. It analyses officeholding from a social and political standpoint, examining the role of officers in governing village communities, and how this was affected by the decline of lordship and development of the state. The study deliberated bridges the medieval/early modern divide, analysing the period 1300-1600. The evidence base for this investigation relies on the reconstruction of officeholding from the court rolls of three case-study manors. These consist of Little Downham (Cambs.), Horstead (Norf.) and Worfield (Salop.). The first part of the thesis utilises quantitative methodologies to analyse the change in presentments made by officers (chapter one) and patterns in participation in office (chapter two). The second part adopts a qualitative approach to examine the role of officers in governing village communities (chapter three), attitudes to office among manorial tenants (chapter four), and the interaction of officeholding with the state and especially with the emergent civil parish (chapter five). Four central conclusions emerge from this work. Firstly, manorial officeholding remained an important institution in the English countryside across the period 1300-1600. Secondly, this was achieved via support from tenants who were invested in manorial office rather than pressure from lords or the crown. Thirdly, officeholding worked to create and reinforce social stratification, helping maintain the position of a village elite. Fourthly, the officeholding system was robust enough to survive the expansion of the state into local communities under successive English monarchs. These conclusions in turn have implications for the wider historical literature concerning late medieval and early modern England. They reinforce the revisionist argument that lord-tenant relations were not inevitability hostile and that many wealthier tenants benefitted from seignorial structures. More significantly, they add weight to the notion of a medieval equivalent to the early modern ‘middling sort’, suggesting that the emergence of a local elite was operative through manorial structures long before 1600.This thesis was funded via a Trinity College Internal Graduate Studentshi

Starvation Resistance is Associated with Developmentally Specified Changes in Sleep, Feeding and Metabolic Rate

Food shortage represents a primary challenge to survival, and animals have adapted diverse developmental, physiological and behavioral strategies to survive when food becomes unavailable. Starvation resistance is strongly influenced by ecological and evolutionary history, yet the genetic basis for the evolution of starvation resistance remains poorly understood. The fruit fly Drosophila melanogaster provides a powerful model for leveraging experimental evolution to investigate traits associated with starvation resistance. While control populations only live a few days without food, selection for starvation resistance results in populations that can survive weeks. We have previously shown that selection for starvation resistance results in increased sleep and reduced feeding in adult flies. Here, we investigate the ontogeny of starvation resistance-associated behavioral and metabolic phenotypes in these experimentally selected flies. We found that selection for starvation resistance resulted in delayed development and a reduction in metabolic rate in larvae that persisted into adulthood, suggesting that these traits may allow for the accumulation of energy stores and an increase in body size within these selected populations. In addition, we found that larval sleep was largely unaffected by starvation selection and that feeding increased during the late larval stages, suggesting that experimental evolution for starvation resistance produces developmentally specified changes in behavioral regulation. Together, these findings reveal a critical role for development in the evolution of starvation resistance and indicate that selection can selectively influence behavior during defined developmental time points

Longitudinal teacher education and workforce study (LTEWS) final report

The Longitudinal Teacher Education Workforce Study (LTEWS) investigated the career progression of graduate teachers from teacher education into teaching employment in all states and territories across Australia in 2012 and the first half of 2013, and tracked their perceptions, over time, of the relevance and effectiveness of their teacher education programs. Specifically, it investigated: The career progression of the 2011 teacher education graduates from teacher education into, and possible exit from, teaching employment, including their utilisation into teaching, their retention and attrition in teaching in their early years, and their geographic and schools sector mobility; and, The views of teacher education graduates over time on the relevance and effectiveness of their teacher education for their teaching employment, including the relationship between their views of their teacher education and their early career teaching career. &nbsp

Thermoelectric Enhancement in BaGa_2Sb_2 by Zn Doping

The Zintl phase BaGa_2Sb_2 has a unique crystal structure in which large tunnels formed by ethane-like dimeric [Sb_3Ga−GaSb_3] units are filled with Ba atoms. BaGa_2Sb_2 was obtained in high purity from ball-milling followed by hot pressing. It shows semiconducting behavior, in agreement with the valence precise Zintl counting and band structure calculations, with a band gap ∼0.4 eV. The thermal conductivity of BaGa_2Sb_2 is found to be relatively low (0.95 W/K m at 550 K), which is an inherent property of compounds with complex crystal structures. As BaGa_2Sb_2 has a low carrier concentration (∼2 × 10^18 h^+/cm^3) at room temperature, the charge carrier tuning was performed by substituting trivalent Ga with divalent Zn. Zn-doped samples display heavily doped p-type semiconducting behavior with carrier concentrations in the range (5−8) × 10^19 h^+/cm^3. Correspondingly, the zT values were increased by a factor of 6 by doping compared to the undoped sample, reaching a value of ∼0.6 at 800 K. Zn-doped BaGa_2Sb_2 can thus be considered as a promising new thermoelectric material for intermediate-temperature applications

High temperature thermoelectric properties of Zn-doped Eu_5In_2Sb_6

The complex bonding environment of many ternary Zintl phases, which often results in low thermal conductivity, makes them strong contenders as thermoelectric materials. Here, we extend the investigation of A_5In_2Sb_6 Zintl compounds with the Ca_5Ga_2As_6 crystal structure to the only known rare-earth analogue: Eu_5In_2Sb_6. Zn-doped samples with compositions of Eu_5In_(2−x)ZnxSb_6 (x = 0, 0.025, 0.05, 0.1, 0.2) were synthesized via ball milling followed by hot pressing. Eu_5In_2Sb_6 showed significant improvements in air stability relative to its alkaline earth metal analogues. Eu5In2Sb6 exhibits semiconducting behavior with possible two band behavior suggested by increasing band mass as a function of Zn content, and two distinct transitions observed in optical absorption measurements (at 0.15 and 0.27 eV). The p-type Hall mobility of Eu_5In_2Sb_6 was found to be much larger than that of the alkaline earth containing A_5In_2Sb_6 phases (A = Sr, Ca) consistent with the reduced hole effective mass (1.1 me). Zn doping was successful in optimizing the carrier concentration, leading to a zT of up to 0.4 at ∼660 K, which is comparable to that of Zn-doped Sr_5In_2Sb_6

Hypocretin neuron-specific transcriptome profiling identifies the sleep modulator Kcnh4a

Sleep has been conserved throughout evolution; however, the molecular and neuronal mechanisms of sleep are largely unknown. The hypothalamic hypocretin/orexin (Hcrt) neurons regulate sleep/wake states, feeding, stress, and reward. To elucidate the mechanism that enables these various functions and to identify sleep regulators, we combined fluorescence cell sorting and RNA-seq in hcrt:EGFP zebrafish. Dozens of Hcrt-neuron-specific transcripts were identified and comprehensive high-resolution imaging revealed gene-specific localization in all or subsets of Hcrt neurons. Clusters of Hcrt-neuron-specific genes are predicted to be regulated by shared transcription factors. These findings show that Hcrt neurons are heterogeneous and that integrative molecular mechanisms orchestrate their diverse functions. The voltage-gated potassium channel Kcnh4a, which is expressed in all Hcrt neurons, was silenced by the CRISPR-mediated gene inactivation system. The mutant kcnh4a(kcnh4a-/-) larvae showed reduced sleep time and consolidation, specifically during the night, suggesting that Kcnh4a regulates sleep.United States-Israel Binational Science Foundation (Grant 2011335)Israel Science Foundation (Grant 366/11)Israel Science Foundation (Legacy Heritage Biomedical Program Grant 398/11)Israel Science Foundation (Legacy Heritage Biomedical Program Grant 992/14)European Community. Marie-Curie Research Networks (International Reintegration Grant FP7-PEOPLE-2010-RG274333